GB2620055A

GB2620055A - Two-stage scroll compressor

Info

Publication number: GB2620055A
Application number: GB2315121.0A
Authority: GB
Inventors: Kawakami Hayato; Tatsuwaki Kohei
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2021-04-12
Filing date: 2021-04-12
Publication date: 2023-12-27
Also published as: JP7408011B2; GB202315121D0; WO2022219668A1; JPWO2022219668A1

Abstract

This two-stage scroll compressor comprises: a sealed container that constitutes an outer shell; a drive mechanism unit that is disposed inside the sealed container and serves as a drive source; two compression mechanism units that are respectively disposed above and below the drive mechanism unit, each having a compression chamber formed by combining a fixed scroll that is fixed inside the sealed container and an orbiting scroll that is driven by the drive mechanism unit; a crankshaft that transmits the driving power of the drive mechanism unit to the two orbiting scrolls; and a balancer that is provided to the crankshaft and cancels out an unbalance caused by the two orbiting scrolls. The two orbiting scrolls are provided eccentrically in the same direction with respect to the center axis of the crankshaft.

Description

Translation of the International Application

DESCRIPTION Title of Invention

TWO-STAGE SCROLL COMPRESSOR

Technical Field

[0001] The present disclosure relates to a two-stage scroll compressor to be mounted mainly in a refrigeration apparatus, an air-conditioning apparatus, and a water heating apparatus.

Background Art

[0002] A known multi-stage scroll compressor includes a sealed container, multiple compression mechanisms disposed in the sealed container and configured to compress refrigerant, and a drive mechanism configured to drive the multiple compression mechanisms. The drive mechanism is disposed between two of the multiple compression mechanisms. The sealed container has three internal spaces including a low-pressure space from which the refrigerant is sucked by one of the multiple compression mechanisms, an intermediate-pressure space into which the refrigerant sucked from the low-pressure space and compressed by the one of the multiple compression mechanisms is discharged, and a high-pressure space into which the refrigerant sucked from the intermediate-pressure space and compressed by another one of the multiple compression mechanisms is discharged. The multiple compression mechanisms each include a fixed scroll and an orbiting scroll, each of which includes a baseplate and a scroll wrap protruding from the baseplate, and each have a compression chamber defined by a combination of the fixed scroll and the orbiting scroll. Such a configuration ensures adequate performance of the scroll compressor (refer to, for example, Patent Literature 1).

Citation List Patent Literature [0003] Patent Literature 1: Japanese Patent No. 6689414 Summary of Invention Technical Problem [0004] Like the scroll compressor disclosed in Patent Literature 1, a two-stage scroll compressor includes a sealed container, two compression mechanisms, and a drive mechanism disposed between the two compression mechanisms such that the two compression mechanisms and the drive mechanism are located in the sealed container. The number of eccentrically positioned parts (hereinafter, referred to as eccentric parts), such as orbiting scrolls, of such a two-stage scroll compressor is larger than that of a single-stage scroll compressor. Inappropriate balancing design of the eccentric parts may cause a decrease in efficiency of the compressor and an increase in vibration and noise.

[0005] In response to the above issue, it is an object of the present disclosure to provide a two-stage scroll compressor including eccentric parts appropriately designed for balancing that reduces or eliminates a decrease in efficiency of the compressor and an increase in vibration and noise.

Solution to Problem [0006] A two-stage scroll compressor according to an embodiment of the present disclosure includes a sealed container serving as a shell, a drive mechanism disposed in the sealed container and serving as a driving source, two compression mechanisms disposed above and below the drive mechanism and each having a compression chamber defined by a combination of a fixed scroll fixed in the sealed container and an orbiting scroll configured to be driven by the drive mechanism, a crankshaft configured to transmit a driving force from the drive mechanism to the two orbiting scrolls, and a balancer disposed on the crankshaft and configured to remove an unbalanced condition caused by the two orbiting scrolls. The two orbiting scrolls are offset from a central axis of the crankshaft in the same direction.

Advantageous Effects of Invention [0007] In the two-stage scroll compressor according to the embodiment of the present disclosure, the two orbiting scrolls, which are eccentric parts, are offset from the central axis of the crankshaft in the same direction. Such a configuration allows the balancer to be disposed between the two compression mechanisms. This ensures a sufficient displacement, thus reducing or eliminating a decrease in efficiency of the compressor. This also reduces static and dynamic unbalanced conditions, thus reducing or eliminating an increase in vibration and noise.

Brief Description of Drawings

[0008] [Fig. 1] Fig. 1 is a sectional view of a two-stage scroll compressor according to Embodiment 1.

[Fig. 2] Fig. 2 includes diagrams illustrating directions of simple harmonic motion of two Oldham rings in the two-stage scroll compressor according to Embodiment 1.

[Fig. 3] Fig. 3 is a schematic diagram illustrating a positional relationship between the two Oldham rings and two orbiting scrolls in the two-stage scroll compressor according to Embodiment 1.

[Fig. 4] Fig. 4 is a graph illustrating an inertial force that acts on the orbiting scroll and a balancer during one revolution in the two-stage scroll compressor according to Embodiment 1.

[Fig. 5] Fig. 5 is a graph illustrating an inertial force that acts on the Oldham ring in a direction of offset during one revolution in the two-stage scroll compressor according to Embodiment 1.

[Fig. 6] Fig. 6 is a graph illustrating inertial forces that act on the two Oldham rings in the direction of offset during one revolution in the two-stage scroll compressor according to Embodiment 1 including parts arranged such that the directions of simple harmonic motion of the two Oldham rings are orthogonal to each other.

[Fig. 7] Fig. 7 is a graph illustrating inertial forces that act on the two Oldham rings in the direction of offset during one revolution in the two-stage scroll compressor according to Embodiment 1 including the parts arranged such that the directions of simple harmonic motion of the two Oldham rings are aligned with each other.

[Fig. 8] Fig. 8 is a graph illustrating inertial forces that act on two Oldham rings in the direction of offset during one revolution in a two-stage scroll compressor according to Embodiment 2 including parts arranged such that the directions of simple harmonic motion of the two Oldham rings are orthogonal to each other.

[Fig. 9] Fig. 9 is a schematic diagram illustrating a positional relationship between two orbiting scrolls and a balancer in a two-stage scroll compressor according to Embodiment 3.

[Fig. 10] Fig. 10 is a sectional view of a two-stage scroll compressor according to Embodiment 4.

Description of Embodiments

[0009] Embodiments of the present disclosure will be described below with reference to the drawings. Note that the embodiments described below should not be construed as limiting the present disclosure. Furthermore, note that the relationship between the sizes of components in the following figures may differ from that of actual ones.

[0010] Embodiment 1.

Fig. 1 is a sectional view of a two-stage scroll compressor 100 according to Embodiment 1.

[0011] The two-stage scroll compressor 100 according to Embodiment 1 has a function of sucking a fluid, such as refrigerant, compressing the fluid into a high-temperature, high-pressure state, and then discharging the fluid. As illustrated in Fig. 1, the two-stage scroll compressor 100 includes a sealed container 11, serving as a shell. The sealed container 11 contains a first compression mechanism 35, a second compression mechanism 36, a drive mechanism 37, and other components. In the sealed container 11, the first compression mechanism 35 is disposed above the drive mechanism 37, and the second compression mechanism 36 is disposed below the drive mechanism 37.

The two-stage scroll compressor 100 performs two-stage compression with the first compression mechanism 35 as a lower-stage compression element and the second compression mechanism 36 as a higher-stage compression element. In other words, the two-stage scroll compressor 100 is configured such that the fluid is compressed by the first compression mechanism 35 and is then further compressed by the second compression mechanism 36. An oil sump 20 is located at the bottom of the sealed container 11.

[0012] The sealed container 11 has three internal spaces: a low-pressure space 22 from which the fluid is sucked by the first compression mechanism 35; an intermediate-pressure space 23 into which the fluid compressed by the first compression mechanism 35 is discharged; and a high-pressure space 24 into which the fluid compressed by the second compression mechanism 36 is discharged.

[0013] The first compression mechanism 35 has a function of compressing the fluid sucked through a suction pipe 8 in communication with a pipe outside the sealed container 11 and discharging the fluid into the intermediate-pressure space 23 in the sealed container 11. The second compression mechanism 36 has a function of compressing the fluid sucked from the intermediate-pressure space 23 and discharging the fluid into the high-pressure space 24 located in a lower portion of the sealed container 11. Such a high-pressure fluid discharged in the high-pressure space 24 is discharged out of the sealed container 11 through a discharge pipe 9. The drive mechanism 37 has a function of driving a first orbiting scroll 2 included in the first compression mechanism 35 and a second orbiting scroll 5 included in the second compression mechanism 36 to compress the fluid. In other words, the drive mechanism 37 drives the first orbiting scroll 2 and the second orbiting scroll 5 through a crankshaft 7 to compress the fluid in the first compression mechanism 35 and the second compression mechanism 36.

[0014] The first compression mechanism 35 includes a first fixed scroll 1 and the first orbiting scroll 2. The first orbiting scroll 2 is disposed in a lower portion of the first compression mechanism 35, and the first fixed scroll 1 is disposed in an upper portion thereof. The first fixed scroll 1 includes a first fixed baseplate lc and a first fixed scroll wrap 1 b, which is a scroll wrap located on one surface of the first fixed baseplate lc.

The first orbiting scroll 2 includes a first orbiting baseplate 2c and a first orbiting scroll wrap 2b, which is a scroll wrap located on one surface of the first orbiting baseplate 2c. The first fixed scroll wrap lb and the first orbiting scroll wrap 2b each have a shape that extends along a curve, such as an involute or an algebraic spiral. The first fixed scroll 1 and the first orbiting scroll 2 are disposed in the sealed container 11 such that the first fixed scroll wrap lb and the first orbiting scroll wrap 2b mate with each other. The first fixed scroll wrap lb and the first orbiting scroll wrap 2b define therebetween a first compression chamber 12, which decreases in volume as the chamber moves inward in a radial direction of the scrolls.

[0015] The first fixed scroll 1 is fixed in the sealed container 11 by a first frame 3 fixed to the sealed container 11. The first fixed scroll 1 has, in its central part, a first discharge port la, through which the fluid compressed to an intermediate pressure is discharged. A first valve 15 including a flat spring is disposed at an outlet opening of the first discharge port la, and covers the outlet opening to prevent backflow of the fluid. At one end of the first valve 15, a first valve guard 14 is disposed to limit the amount of lift of the first valve 15. Specifically, when the fluid is compressed to an intermediate pressure in a central part of the first compression chamber 12, the first valve 15 is lifted against its elastic force, so that the compressed fluid is discharged from the first discharge port la into the intermediate-pressure space 23 through a passage 35a.

[0016] The first fixed scroll 1 has a sub-port ld, which is in communication with the intermediate-pressure space 23, in addition to the first discharge port la. A sub-port valve 29 including a flat spring is disposed at an outlet opening of the sub-port ld, and covers the outlet opening to prevent backflow of the fluid. At one end of the sub-port valve 29, a sub-port valve guard 28 is disposed to limit the amount of lift of the sub-port valve 29. Specifically, when the fluid that is being compressed in the first compression chamber 12 is compressed to or above an intermediate pressure, the sub-port valve 29 is lifted against its elastic force, so that the compressed fluid is discharged from the sub-port 1d into the intermediate-pressure space 23 through the passage 35a.

[0017] A first Oldham ring 25 causes the first orbiting scroll 2 to perform eccentric revolving motion relative to the first fixed scroll 1 without rotating. The first orbiting scroll 2 has, in its central part, a first orbiting bearing 2d to receive a driving force. The first orbiting bearing 2d has a recessed shape to fit an upper end of the crankshaft 7.

The first orbiting bearing 2d of the first orbiting scroll 2 fits a first eccentric portion 7a, which is the upper end of the crankshaft 7, which will be described later, such that a slight gap is left therebetween.

[0018] The second compression mechanism 36 includes a second fixed scroll 4 and the second orbiting scroll 5. The second orbiting scroll 5 is disposed in an upper portion of the second compression mechanism 36, and the second fixed scroll 4 is disposed in a lower portion thereof. The second fixed scroll 4 includes a second fixed baseplate 4c and a second fixed scroll wrap 4b, which is a scroll wrap located on one surface of the second fixed baseplate 4c. The second orbiting scroll 5 includes a second orbiting baseplate Sc and a second orbiting scroll wrap 5b, which is a scroll wrap located on one surface of the second orbiting baseplate Sc. The second fixed scroll wrap 4b and the second orbiting scroll wrap 5b each have a shape that extends along a curve, such as an involute or an algebraic spiral. The second fixed scroll 4 and the second orbiting scroll 5 are disposed in the sealed container 11 such that the second fixed scroll wrap 4b and the second orbiting scroll wrap 5b mate with each other. The second fixed scroll wrap 4b and the second orbiting scroll wrap 5b define therebetween a second compression chamber 13, which decreases in volume as the chamber moves inward in a radial direction of the scrolls.

[0019] The second fixed scroll 4 is fixed in the sealed container 11 by a second frame 6 fixed to the sealed container 11. The second fixed scroll 4 has, in its central part, a second discharge port 4a, through which the fluid compressed to an intermediate pressure is discharged. A second valve 17 including a flat spring is disposed at an outlet opening of the second discharge port 4a, and covers the outlet opening to prevent backflow of the fluid. At one end of the second valve 17, a second valve guard 16 is disposed to limit the amount of lift of the second valve 17. Specifically, when the fluid is compressed to a predetermined pressure in the second compression chamber 13, the second valve 17 is lifted against its elastic force. The compressed fluid is then discharged from the second discharge port 4a into the high-pressure space 24 in a chamber 30, which is attached to a rear surface of the second fixed scroll 4. The fluid is discharged out of the sealed container 11 through the discharge pipe 9. The chamber 30 and the rear surface of the second fixed scroll 4 define a space, which is the high-pressure space 24 in communication with the second discharge port 4a.

[0020] A second Oldham ring 26 causes the second orbiting scroll 5 to perform eccentric revolving motion relative to the second fixed scroll 4 without rotating. The second orbiting scroll 5 has, in its central part, a second orbiting bearing 5d to receive a driving force. The second orbiting bearing 5d has a vertically extending through-hole to fit a lower end of the crankshaft 7. The second orbiting bearing 5d of the second orbiting scroll 5 fits a second eccentric portion 7b, which is the lower end of the crankshaft 7, which will be described later, such that a slight gap is left therebetween.

[0021] The drive mechanism 37 includes a stator 19 fixed to and held in the sealed container 11, a rotor 18 fixed to the crankshaft 7 and disposed adjacent to an inner circumferential surface of the stator 19 such that the rotor 18 can rotate, and the crankshaft 7. The crankshaft 7 is contained in the sealed container 11, extends in a longitudinal direction of the sealed container 11, and rotates together with the rotor 18. The stator 19 has a function of driving and rotating the rotor 18 when energized. An outer circumferential surface of the stator 19 is fixed to the sealed container 11 by, for example, shrink fitting or spot welding, and is supported by the sealed container 11. The rotor 18 is driven and rotated when the stator 19 is energized, and has a function of rotating the crankshaft 7. The rotor 18 includes a permanent magnet. The rotor 18 is fixed to an outer circumferential surface of the crankshaft 7. The rotor 18 is held at a small distance from the stator 19.

[0022] The crankshaft 7 is rotated with the rotation of the rotor 18, thus driving and causing the first orbiting scroll 2 and the second orbiting scroll 5 to revolve. An upper part of the crankshaft 7 is supported by a bearing 3a located in a central part of the first frame 3, and a lower part thereof is supported by a bearing 6a located in a central part of the second frame 6 such that the crankshaft 7 can rotate. The lower end of the crankshaft 7 includes the second eccentric portion 7b, which is fitted in the second orbiting bearing 5d such that the second orbiting scroll 5 can revolve eccentrically. The upper end of the crankshaft 7 includes the first eccentric portion 7a, which is fitted in the first orbiting bearing 2d such that the first orbiting scroll 2 can revolve eccentrically.

The first eccentric portion 7a and the second eccentric portion 7b are located such that the direction of offset, i.e. eccentricity, of the first eccentric portion 7a is aligned with that of the second eccentric portion 7b. Such a configuration is to cause the first orbiting scroll 2 and the second orbiting scroll 5 to be offset from a central axis of, i.e. eccentric to, the crankshaft 7 in the same direction such that the direction of offset of the first orbiting scroll 2 is aligned with that of the second orbiting scroll 5.

[0023] The crankshaft 7 has a balancer 31 to remove unbalanced conditions caused by orbital motion of the first orbiting scroll 2 and the second orbiting scroll 5 and simple harmonic motion of the first Oldham ring 25 and the second Oldham ring 26. The balancer 31 is offset from the central axis of the crankshaft 7 in a direction opposite to the direction of offset of the first orbiting scroll 2 and the second orbiting scroll 5. In consideration of, for example, manufacturing errors, as long as an angle 0 formed by the balancer 31 and the direction of offset of the two orbiting scrolls is within a range of 180 degrees ± 5 degrees, the balancer 31 can be regarded as being offset from the central axis of the crankshaft 7 in the direction opposite to the direction of offset of the two orbiting scrolls. The angle e is formed by two straight lines drawn such that, as viewed from above the two-stage scroll compressor 100, one of the two straight lines extends from the central axis of the crankshaft 7 to the center of gravity of the balancer 31 and the other straight line extends from the central axis of the crankshaft 7 to an eccentric axis at the center of the eccentric portion for one of the two orbiting scrolls. [0024] The suction pipe 8 to suck the fluid, the discharge pipe 9 to discharge the fluid, and an injection pipe 10 to guide the fluid for cooling the intermediate-pressure space 23 are coupled to the sealed container 11.

[0025] The first frame 3 and the second frame 6 are fixed in the sealed container 11. The first frame 3 is fixed to an inner circumferential surface of the sealed container 11 such that the first frame 3 is located above the drive mechanism 37. The first frame 3 has, in its central part, a through-hole 3c to journal the crankshaft 7. The first frame 3 supports the crankshaft 7 such that the crankshaft 7 can rotate in the bearing 3a. The bearing 3a includes a sliding bearing. The second frame 6 is fixed to the inner circumferential surface of the sealed container 11 such that the second frame 6 is located below the drive mechanism 37. The second frame 6 has, in its central part, a through-hole 6d to journal the crankshaft 7. The second frame 6 includes a passage 6b to guide the fluid to the second compression chamber 13. The second frame 6 has, in its upper part, a second suction port 6c, serving as an inlet of the passage 6b. The second frame 6 supports the second orbiting scroll 5, and further supports the crankshaft 7 such that the crankshaft 7 can rotate in the bearing 6a. An outer circumferential surface of the second frame 6 may be fixed to the inner circumferential surface of the sealed container 11 by, for example, shrink fitting or spot welding. [0026] An oil pump 21 is fixed to the lower end of the crankshaft 7. The second fixed scroll 4 has a through-hole 4e so that a rotational force of the crankshaft 7 can be transmitted to the oil pump 21. The oil pump 21, which is a positive-displacement pump, is configured to, with the rotation of the crankshaft 7, supply refrigerating machine oil held in the oil sump 20 to the first orbiting bearing 2d, the bearing 3a, a thrust bearing 3b, the second orbiting bearing 5d, and the bearing 6a through an oil circuit (not illustrated) located in the crankshaft 7.

[0027] The sealed container 11 contains the first Oldham ring 25, which inhibits rotational motion of the first orbiting scroll 2 during eccentric revolving motion of the first orbiting scroll 2, and the second Oldham ring 26, which inhibits rotational motion of the second orbiting scroll 5 during eccentric revolving motion of the second orbiting scroll 5.

The first Oldham ring 25 is disposed between the first orbiting scroll 2 and the first frame 3, and is configured to inhibit rotational motion of the first orbiting scroll 2 and enable the first orbiting scroll 2 to perform orbital motion. The second Oldham ring 26 is disposed between the second orbiting scroll 5 and the second frame 6, and is configured to inhibit rotational motion of the second orbiting scroll 5 and enable the second orbiting scroll 5 to perform orbital motion.

[0028] Operation of the two-stage scroll compressor 100 will now be described in brief with reference to Fig. 1. In the following description, it is assumed that the fluid is refrigerant.

When power is supplied to a power supply terminal (not illustrated) provided in the sealed container 11, a torque is generated at the stator 19 and the rotor 18, thus rotating the crankshaft 7. The first eccentric portion 7a of the crankshaft 7 fits the first orbiting scroll 2 such that the first orbiting scroll 2 can revolve. The second eccentric portion 7b of the crankshaft 7 fits the second orbiting scroll 5 such that the second orbiting scroll 5 can revolve. The first orbiting scroll wrap 2b of the first orbiting scroll 2 and the first fixed scroll wrap lb of the first fixed scroll 1 mate with each other to define multiple first compression chambers 12. The second orbiting scroll wrap 5b of the second orbiting scroll Sand the second fixed scroll wrap 4b of the second fixed scroll 4 mate with each other to define multiple second compression chambers 13.

[0029] The first compression chambers 12 trapping gaseous refrigerant from the suction pipe 8 decrease in volume as the chambers move toward the center of the first orbiting scroll 2 from the periphery of the first orbiting scroll 2 with eccentric revolving motion of the first orbiting scroll 2, thus compressing the refrigerant. The refrigerant compressed in the first compression chambers 12 is carbon dioxide alone or a refrigerant mixture containing carbon dioxide. Since carbon dioxide alone, which has low global warming potential (GVVP), or a refrigerant mixture containing carbon dioxide is used as refrigerant that is compressed by the two-stage scroll compressor 100, the use of such refrigerant can contribute to suppressing global warming. The gaseous refrigerant compressed in the first compression chambers 12 is discharged against the first valve from the first discharge port la located in the first fixed scroll 1 into the intermediate-pressure space 23. The refrigerant compressed in the first compression chambers 12 is mixed with refrigerant flowing from the injection pipe 10.

[0030] The second compression chambers 13 trapping the gaseous refrigerant from the intermediate-pressure space 23 decrease in volume as the chambers move toward the center of the second orbiting scroll 5 from the periphery of the second orbiting scroll 5 with eccentric revolving motion of the second orbiting scroll 5, thus compressing the refrigerant. The gaseous refrigerant compressed in the second compression chambers 13 is discharged against the second valve 17 from the second discharge port 4a located in the second fixed scroll 4 and is then discharged out of the sealed container 11 through the discharge pipe 9. The first valve guard 14 and the second valve guard 16 respectively limit deformation of the first valve 15 and the second valve 17 so that the valves are not deformed more than necessary, thus preventing the first valve 15 and the second valve 17 from being broken.

[0031] Hereinafter, the first Oldham ring 25 and the second Oldham ring 26 will be collectively referred to as two Oldham rings. The other first and second components, serving as two components, will be collectively referred in a manner similar to the above.

[0032] Fig. 2 includes diagrams illustrating directions of simple harmonic motion of the two Oldham rings in the two-stage scroll compressor 100 according to Embodiment 1. Fig. 2(a) illustrates the direction of simple harmonic motion of the first Oldham ring 25.

Fig. 2(b) illustrates the direction of simple harmonic motion of the second Oldham ring 26. Fig. 2 includes the diagrams illustrating the two Oldham rings as viewed from above the two-stage scroll compressor 100. Fig. 2(a) and Fig. 2(b) illustrate the two Oldham rings such that the positions of first orbiting key grooves 2e in a circumferential direction coincide with the positions of second frame key grooves 6e in the circumferential direction.

[0033] The first Oldham ring 25 includes a ring portion 25a and two pairs of first Oldham keys 25b arranged on upper and lower surfaces of the ring portion 25a. The two first Oldham keys 25b on the upper surface are placed in the two first orbiting key grooves 2e located in the first orbiting scroll 2, and can slide in one direction. The two first Oldham keys 25b on the lower surface are placed in two first frame key grooves 3e located in the first frame 3, and can slide in a direction that intersects the above-described one direction. Such a configuration causes the first orbiting scroll 2 to perform orbital motion without rotating.

[0034] The second Oldham ring 26 includes a ring portion 26a and two pairs of second Oldham keys 26b arranged on upper and lower surfaces of the ring portion 26a. The second Oldham keys 26b on the upper surface are placed in the second frame key grooves 6e located in the second frame 6, and can slide in one direction. The second Oldham keys 26b on the lower surface are placed in second orbiting key grooves 5e located in the second orbiting scroll 5, and can slide in a direction that intersects the above-described one direction. Such a configuration causes the second orbiting scroll 5 to perform orbital motion without rotating.

[0035] The first frame 3 is disposed such that the two first frame key grooves 3e are arranged horizontally in Fig. 2(a). The direction of simple harmonic motion of the first Oldham ring 25 is represented by arrows in Fig. 2(a). The second frame 6 is disposed such that the two second frame key grooves 6e are arranged vertically in Fig. 2(b) and are directed perpendicular to the two first frame key grooves 3e. The direction of simple harmonic motion of the second Oldham ring 26 is represented by arrows in Fig. 2(b). Thus, the directions of simple harmonic motion of the first Oldham ring 25 and the second Oldham ring 26 are orthogonal to each other.

[0036] Fig. 3 is a schematic diagram illustrating a positional relationship between the two orbiting scrolls and the two Oldham rings in the two-stage scroll compressor 100 according to Embodiment 1. For ease of explanation, it is assumed that the positions of the centers of gravity of the two orbiting scrolls are on an eccentric axis E2, and the two orbiting scrolls have the same orbital radius.

[0037] Fig. 3 illustrates a state in which the first eccentric portion 7a and the second eccentric portion 7b of the crankshaft 7 are located on the right of Fig. 3 during driving of the two-stage scroll compressor 100 as viewed in a direction in which the first orbiting key grooves 2e are arranged in a direction into the drawing sheet. The direction of simple harmonic motion of the first Oldham ring 25 is aligned with the horizontal direction in Fig. 3. The position, B, of the center of gravity of the first Oldham ring 25 always coincides with the eccentric axis E2 during revolution. The direction of simple harmonic motion of the second Oldham ring 26 is aligned with a direction perpendicular to the drawing sheet of Fig. 3. The position, D, of the center of gravity of the second Oldham ring 26 always coincides with the central axis, El, of the crankshaft 7 during revolution.

[0038] Fig. 4 is a graph illustrating an inertial force that acts on the orbiting scroll and the balancer 31 during one revolution in the two-stage scroll compressor 100 according to Embodiment 1. Although Fig. 4 illustrates one of the two orbiting scrolls, an inertial force acting on the other orbiting scroll can be similarly represented by a straight line. As illustrated in Fig. 4, a centrifugal force acts on the orbiting scroll and the balancer 31 during revolution, so that the inertial force acting on the orbiting scroll and the balancer 31 during one revolution is constant.

[0039] Fig. 5 is a graph illustrating an inertial force that acts on the Oldham ring in the direction of offset during one revolution in the two-stage scroll compressor 100 according to Embodiment 1. Although Fig. 5 illustrates one of the two Oldham rings, an inertial force acting on the other Oldham ring can be similarly represented by a waveform.

Unlike the orbiting scroll and the balancer 31, the Oldham ring performs simple harmonic motion. An inertial force acting on the Oldham ring during one revolution changes periodically, as illustrated in Fig. 5. Therefore, it is theoretically impossible to achieve perfect balance with the balancer 31, on which a constant inertial force always acts.

[0040] Fig. 6 is a graph illustrating inertial forces that act on the two Oldham rings in the direction of offset during one revolution in the two-stage scroll compressor 100 according to Embodiment 1 including the parts arranged such that the directions of simple harmonic motion of the two Oldham rings are orthogonal to each other.

As illustrated in Fig. 6, a simple harmonic motion period of the first Oldham ring 25 differs from that of the second Oldham ring 26 by 90 degrees. Thus, the sum of inertial forces acting on the two Oldham rings during one revolution is levelled.

[0041] Fig. 7 is a graph illustrating inertial forces that act on the two Oldham rings in the direction of offset during one revolution in the two-stage scroll compressor 100 according to Embodiment 1 including the parts arranged such that the directions of simple harmonic motion of the two Oldham rings are aligned with each other As illustrated in Fig. 7, the simple harmonic motion period of the first Oldham ring 25 coincides with that of the second Oldham ring 26. Thus, the sum of inertial forces acting on the two Oldham rings during one revolution is not levelled.

[0042] In the two-stage scroll compressor 100 according to Embodiment 1, the first compression mechanism 35 and the suction pipe 8 are arranged above the drive mechanism 37, whereas the second compression mechanism 36 and the discharge pipe 9 are arranged below the drive mechanism 37. The configuration is not limited to this example. The arrangement of these components may be inverted. In other words, the first compression mechanism 35 and the suction pipe 8 may be arranged below the drive mechanism 37, whereas the second compression mechanism 36 and the discharge pipe 9 may be arranged above the drive mechanism 37.

[0043] In the two-stage scroll compressor 100 according to Embodiment 1, the balancer 31 is disposed above the drive mechanism 37. The configuration is not limited to this example. The balancer 31 may be disposed below the drive mechanism 37.

[0044] In the two-stage scroll compressor 100 according to Embodiment 1, as illustrated in Fig. 2, the two Oldham rings each include the keys, and the two frames each have the key grooves. The configuration is not limited to this example. The two-stage scroll compressor 100 only has to have the capability to allow the two orbiting scrolls to perform orbital motion without rotating. For example, each of the two Oldham rings may have key grooves, and each of the two frames may include keys.

[0045] (Advantages of Embodiment 1) The above-described two-stage scroll compressor 100 according to Embodiment 1 includes the sealed container 11 serving as a shell, the drive mechanism 37 disposed in the sealed container 11 and serving as a driving source, the two compression mechanisms disposed above and below the drive mechanism 37 and each having a compression chamber defined by a combination of the fixed scroll fixed in the sealed container 11 and the orbiting scroll configured to be driven by the drive mechanism 37, the crankshaft 7 configured to transmit a driving force from the drive mechanism 37 to the two orbiting scrolls, and the balancer 31 disposed on the crankshaft 7 and configured to remove an unbalanced condition caused by the two orbiting scrolls. The two orbiting scrolls are offset from the central axis El of the crankshaft 7 in the same direction.

[0046] In the two-stage scroll compressor 100 according to Embodiment 1, the two orbiting scrolls, which are the eccentric parts, are offset from the central axis El of the crankshaft 7 in the same direction. Such a configuration allows the balancer 31 to be disposed between the two compression mechanisms. This ensures a sufficient displacement, thus reducing or eliminating a decrease in efficiency of the compressor. This also reduces static and dynamic unbalanced conditions, thus reducing or eliminating an increase in vibration and noise. In consideration of, for example, manufacturing errors, as long as an angle 01 formed by the directions of eccentricity of the two orbiting scrolls is within a range of 0 degrees ± 5 degrees, the two orbiting scrolls can be regarded as being offset from the central axis El of the crankshaft 7 in the same direction. The reason is as follows. If the two-stage scroll compressors 100 are manufactured so that 01 is 0 degrees, there may be some variations between the compressors. However, as long as 01 is within a range of 0 degrees ± 5 degrees, the same advantages as those described above can be obtained.

[0047] Since the two eccentric portions of the crankshaft 7 are fitted in the bearings of the two orbiting scrolls, the angle formed by the directions of eccentricity of the two orbiting scrolls is the same as that formed by the two eccentric portions of the crankshaft 7. The angle 01 is identical to an angle formed by two straight lines drawn such that, as viewed from above the two-stage scroll compressor 100, the two straight lines extend from the central axis El of the crankshaft 7 to the eccentric axes at the centers of the two eccentric portions.

[0048] Consider a case where the two orbiting scrolls are not offset from the central axis El of the crankshaft 7 in the same direction.

For example, if 01 = 180 degrees, the balancer 31 would have to be disposed above the first compression mechanism 35 or below the second compression mechanism 36 to remove static and dynamic unbalanced conditions caused by the two orbiting scrolls. In other words, the balancer 31 could not be disposed between the two compression mechanisms.

[0049] If the balancer 31 were disposed above the first compression mechanism 35, the crankshaft 7 would have to extend through the first fixed scroll 1 and the first orbiting scroll 2 and beyond the first compression mechanism 35. In such a case, the central parts of the first fixed scroll 1 and the first orbiting scroll 2 were occupied by the crankshaft 7 and the bearings for the crankshaft 7. Therefore, if the balancer 31 were disposed above the first compression mechanism 35, a displacement could not be increased beyond a certain amount.

[0050] If the balancer 31 were disposed below the second compression mechanism 36, the balancer 31 would be placed in the refrigerating machine oil in the oil sump 20. Revolution of the balancer 31 placed in the refrigerating machine oil would cause oil churning loss, resulting in a decrease in efficiency of the compressor. If 0 degrees < 01 < 180 degrees, the central axis El of the crankshaft 7 and the two eccentric axes would not be on one straight line when viewed from above the two-stage scroll compressor 100. Therefore, static and dynamic unbalanced conditions caused by the two orbiting scrolls could not be removed by using a single balancer 31. Furthermore, the extent of static and dynamic unbalanced conditions in the case where 0 degrees < 01 < 180 degrees would be larger than that in the case where 91 = 0 degrees.

[0051] The two-stage scroll compressor 100 according to Embodiment 1 includes the two Oldham rings configured to inhibit rotation of the orbiting scrolls. The two Oldham rings are configured to perform simple harmonic motion in orthogonal directions.

[0052] In the two-stage scroll compressor 100 according to Embodiment 1, the two Oldham rings are configured to perform simple harmonic motion in orthogonal directions. Such a configuration allows the inertial forces acting on the two Oldham rings in the direction of offset to be levelled. This further reduces or eliminates an increase in vibration and noise. In consideration of, for example, manufacturing errors, as long as an angle 82 formed by the directions of simple harmonic motion of the two Oldham rings is within a range of 90 degrees ± 5 degrees, the directions of simple harmonic motion of the two Oldham rings can be regarded as being orthogonal to each other. The reason is as follows. If the two-stage scroll compressors 100 are manufactured so that 02 is 90 degrees, there may be some variations between the compressors. However, as long as 02 is within a range of 90 degrees ± 5 degrees, the same advantages as those described above can be obtained.

[0053] In the two-stage scroll compressor 100 according to Embodiment 1, the balancer 31 is offset from the central axis El of the crankshaft 7 in the direction opposite to the direction of offset of the two orbiting scrolls.

[0054] Since the balancer 31 is offset from the central axis El of the crankshaft 7 in the direction opposite to the direction of offset of the two orbiting scrolls in the two-stage scroll compressor 100 according to Embodiment 1, static and dynamic unbalanced conditions can be minimized, thus further reducing or eliminating an increase in vibration and noise.

[0055] Embodiment 2.

Embodiment 2 will be described below. In Embodiment 2, explanation of the previously described components in Embodiment 1 is omitted, and the same components as or components similar to those in Embodiment 1 are designated by the same reference signs.

[0056] In a two-stage scroll compressor 100 according to Embodiment 2, Mold1 is the mass of a first Oldham ring 25, R1 is the orbital radius of a first orbiting scroll 2, Mold2 is the mass of a second Oldham ring 26, R2 is the orbital radius of a second orbiting scroll 5, and the two Oldham rings satisfy Expression (1) described below.

[0057] 0.95 (Mold2 x R2/Moldl x R1) 1.05 (1) [0058] The product of the mass of a part and an orbital radius is defined herein as the amount of eccentricity. Moldl x R1 is the amount of eccentricity of the first Oldham ring 25, and Mold2 x R2 is the amount of eccentricity of the second Oldham ring 26. In other words, Expression (1) represents that the ratio of the amount of eccentricity of the second Oldham ring 26 to the amount of eccentricity of the first Oldham ring 25 is greater than or equal to 0.95 and is less than or equal to 1.05 and that the amount of eccentricity of the first Oldham ring 25 is substantially equal to that of the second Oldham ring 26.

[0059] Fig. 8 is a graph illustrating inertial forces that act on the two Oldham rings in the direction of offset during one revolution in the two-stage scroll compressor 100 according to Embodiment 2 including parts arranged such that the directions of simple harmonic motion of the two Oldham rings are orthogonal to each other.

For the two Oldham rings satisfying Expression (1), as illustrated in Fig. 8, inertial forces acting on the two Oldham rings in the direction of offset are identical. Therefore, the sum of inertial forces acting on the two Oldham rings during one revolution is constant.

[0060] (Advantages of Embodiment 2) In the two-stage scroll compressor 100 according to Embodiment 2, the two Oldham rings satisfy 0.95 (Mold2 x R2/Moldl x R1) 1.05 where Mo!di is the mass of the first Oldham ring 25 of the first compression mechanism 35, Mold2 is the mass of the second Oldham ring 26 of the second compression mechanism 36, R1 is the orbital radius of the first orbiting scroll 2 of the first compression mechanism 35, and R2 is the orbital radius of the second orbiting scroll 5 of the second compression mechanism 36. [0061] Since the two Oldham rings satisfy 0.95 (Mold2 x R2/Moldl x R1) 1.05 in the two-stage scroll compressor 100 according to Embodiment 2, inertial forces acting on the two Oldham rings in the direction of offset are identical. This allows the sum of inertial forces acting on the two Oldham rings during one revolution to be constant. Thus, the balancer 31 performing revolving motion enables the extent of a static unbalanced condition to reach zero.

[0062] Embodiment 3.

Embodiment 3 will be described below. In Embodiment 3, explanation of the previously described components in Embodiments 1 and 2 is omitted, and the same components as or components similar to those in Embodiments 1 and 2 are designated by the same reference signs.

[0063] In a two-stage scroll compressor 100 according to Embodiment 3, Morbl is the mass of a first orbiting scroll 2, R1 is the orbital radius of the first orbiting scroll 2, Morb2 is the mass of a second orbiting scroll 5, R2 is the orbital radius of the second orbiting scroll 5, and the two orbiting scrolls satisfy Expression (2) described below.

[0064] 0.95 (Morb2 x R2/Morb1 x R1) 1.05 (2) [0065] The product of the mass of a part and the orbital radius of the part is defined herein as the amount of eccentricity. Morb1 x R1 is the amount of eccentricity of the first orbiting scroll 2, and Morb2 x R2 is the amount of eccentricity of the first orbiting scroll 2. In other words, Expression (2) represents that the ratio of the amount of eccentricity of the second orbiting scroll 5 to that of the first orbiting scroll 2 is greater than or equal to 0.95 and is less than or equal to 1.05 and that the amount of eccentricity of the first orbiting scroll 2 is substantially equal to that of the first orbiting scroll 2.

[0066] Fig. 9 is a schematic diagram illustrating a positional relationship between the two orbiting scrolls and a balancer 31 in the two-stage scroll compressor 100 according to Embodiment 3.

[0067] To remove unbalanced conditions caused by the two orbiting scrolls in the two-stage scroll compressor 100, the balancer 31 may be disposed to satisfy Equation (3) described below, in terms of static balance and dynamic balance. As illustrated in Fig. 9, Lb is a height to the position, F, of the center of gravity of the balancer 31 with respect to the position, C, of the center of gravity of the second orbiting scroll 5, and Lorbl is a height to the position, A, of the center of gravity of the first orbiting scroll 2 with respect to the position C of the center of gravity of the second orbiting scroll 5.

[0068] Lb = Lorb1/(a + 1) (3) [0069] In Equation (3), a is the ratio of the product of the mass and the orbital radius of one of the two orbiting scrolls to that of the other orbiting scroll, as expressed by Equation (4) described below.

[0070] a = (Morb2 x R2)/(Morbl x R1) (4) [0071] In Embodiment 3, 0.95 (Morb2 x R2/Morb1 x R1) 1.05. When Morb1 x R1 = Morb2 x R2, a =1 in Equation (4). Thus, Lb = Lorb1/2 in Equation (3). In other words, to remove unbalanced conditions caused by the two orbiting scrolls in the two-stage scroll compressor 100, the balancer 31 may be disposed such that the position F of the center of gravity of the balancer 31 is at the midpoint between the positions of the centers of gravity of the two orbiting scrolls. In Embodiment 3, therefore, unbalanced conditions caused by the two orbiting scrolls can be removed without complicated design for balancing.

[0072] (Advantages of Embodiment 3) In the two-stage scroll compressor 100 according to Embodiment 3, the two orbiting scrolls satisfy 0.95 (Morb2 x R2/Morbl x R1) 1.05 where Morbl is the mass of the first orbiting scroll 2 of the first compression mechanism 35, Morb2 is the mass of the second orbiting scroll 5 of the second compression mechanism 36, Ri is the orbital radius of the first orbiting scroll 2 of the first compression mechanism 35, and R2 is the orbital radius of the second orbiting scroll 5 of the second compression mechanism 36.

[0073] In the two-stage scroll compressor 100 according to Embodiment 3, the two orbiting scrolls satisfy 0.95 (Morb2 x R2/Morb1 x R1) 1.05. To remove unbalanced conditions caused by the two orbiting scrolls in the two-stage scroll compressor 100, the balancer 31 may be disposed such that the position F of the center of gravity of the balancer 31 is at the midpoint between the positions of the centers of gravity of the two orbiting scrolls. Thus, unbalanced conditions caused by the two orbiting scrolls can be removed without complicated design for balancing.

[0074] Embodiment 4.

Embodiment 4 will be described below. In Embodiment 4, explanation of the previously described components in Embodiments 1 to 3 is omitted, and the same components as or components similar to those in Embodiments 1 to 3 are designated by the same reference signs.

[0075] In a two-stage scroll compressor 100 according to Embodiment 4, Morb1 is the mass of a first orbiting scroll 2, Ri is the orbital radius of the first orbiting scroll 2, Morb2 is the mass of a second orbiting scroll 5, R2 is the orbital radius of the second orbiting scroll 5, and the two orbiting scrolls satisfy Expression (5) described below.

[0076] 2 (Morb2 x R2)/(Morbl x R1) 3 (5) [0077] The product of the mass of a part and the orbital radius of the part is defined herein as the amount of eccentricity. Morbl x R1 is the amount of eccentricity of the first orbiting scroll 2, and Morb2 x R2 is the amount of eccentricity of the first orbiting scroll 2. In other words, Expression (5) represents that the ratio of the amount of eccentricity of the second orbiting scroll 5 to that of the first orbiting scroll 2 is greater than or equal to 2 and is less than or equal to 3.

[0078] To remove unbalanced conditions caused by the two orbiting scrolls in the two-stage scroll compressor 100, a balancer 31 may satisfy Equation (3) described in Embodiment 3, in terms of static balance and dynamic balance. Causing the balancer 31 to satisfy Equation (3) can remove unbalanced conditions caused by the two orbiting scrolls.

[0079] Fig. 10 is a sectional view of the two-stage scroll compressor 100 according to Embodiment 4.

In a case where the two orbiting scrolls satisfy Expression (5) and where the balancer 31 satisfies Equation (3), the balancer 31 is located closer to the second orbiting scroll 5 than to the first orbiting scroll 2, as illustrated in Fig. 10. This provides a large space above the balancer 31. For example, a drive mechanism 37 can be disposed in the large space. The space in a sealed container 11 can be effectively used.

[0080] In the two-stage scroll compressor 100 according to Embodiment 4, the two orbiting scrolls may satisfy Expression (5)' described below instead of Expression (5). [0081] 2 (Morbl x R1)/(Morb2 x R2) 3 (5)' [0082] In a case where the two orbiting scrolls satisfy Expression (5)' and where the balancer 31 satisfies Equation (3), the balancer 31 is located closer to the first orbiting scroll 2 than to the second orbiting scroll 5. This provides a large space below the balancer 31. For example, the drive mechanism 37 can be disposed in the large space. The space in the sealed container 11 can be effectively used.

[0083] (Advantages of Embodiment 4) In the two-stage scroll compressor 100 according to Embodiment 4, the two orbiting scrolls satisfy 2 5 (Morb1 x R1)/(Morb2 x R2) 5 3 or 2 5 (Morb2 x R2)/(Morbl x R1) 5 3 where Morb1 is the mass of the first orbiting scroll 2 of the first compression mechanism 35, Morb2 is the mass of the second orbiting scroll 5 of the second compression mechanism 36, R1 is the orbital radius of the first orbiting scroll 2 of the first compression mechanism 35, and R2 is the orbital radius of the second orbiting scroll 5 of the second compression mechanism 36.

[0084] In the two-stage scroll compressor 100 according to Embodiment 4, the two orbiting scrolls satisfy 2 5 (Morb1 x R1)/(Morb2 x R2) 5 3 or 2 5 (Morb2 x R2)/(Morbl x R1) 5 3. In the two-stage scroll compressor 100 with such a configuration, the balancer 31 to remove unbalance conditions caused by the two orbiting scrolls is located close to one of the two orbiting scrolls, thus providing a large space above or below the balancer 31. The space in the sealed container 11 can be effectively used. [0085] In the two-stage scroll compressor 100 according to Embodiment 4, the two orbiting scrolls satisfy 2 5 (Morb1 x R1)/(Morb2 x R2) 5 3 and the balancer 31 satisfies Lb > Lorb1/2, or the two orbiting scrolls satisfy 2 5 (Morb2 x R2)/(Morb1 x R1) 5 3 and the balancer 31 is disposed to satisfy Lb <Lorb1/2 where Lb is the height to the position of the center of gravity of the balancer 31 with respect to the position of the center of gravity of the second orbiting scroll 5 of the second compression mechanism 36 and Lorb1 is the height to the position of the center of gravity of the first orbiting scroll 2 of the first compression mechanism 35 with respect to the position of the center of gravity of the second orbiting scroll 5 of the second compression mechanism 36.

[0086] In the two-stage scroll compressor 100 according to Embodiment 4, the two orbiting scrolls satisfy 2 5 (Morb1 x R1)/(Morb2 x R2) 5 3, and the balancer 31 is disposed to satisfy Lb > Lorb1/2. Alternatively, the two orbiting scrolls satisfy 2 5 (Morb2 x R2)/(Morb1 x R1) 5 3, and the balancer 31 is disposed to satisfy Lb < Lorb1/2. In other words, in the two-stage scroll compressor 100, the balancer 31 to remove unbalanced conditions caused by the two orbiting scrolls is located close to one of the two orbiting scrolls, thus providing a large space above or below the balancer 31. The space in the sealed container 11 can be effectively used.

[0087] Embodiment 5.

Embodiment Swill be described below. In Embodiment 5, explanation of the previously described components in Embodiments 1 to 4 is omitted, and the same components as or components similar to those in Embodiments 1 to 4 are designated by the same reference signs.

[0088] A two-stage scroll compressor 100 according to Embodiment 5 includes a first orbiting scroll 2, which is made of an aluminum-based material such as aluminum, and a second orbiting scroll 5, which is made of a cast-iron-based material such as spheroidal graphite cast iron.

[0089] In comparison between fluid pressures in two compression chambers, a pressure that increases from a low pressure to an intermediate pressure in a first compression chamber 12 is lower than a pressure that increases from the intermediate pressure to a high pressure in a second compression chamber 13. In general, strength required for the first orbiting scroll 2 is lower than that for the second orbiting scroll 5. Therefore, the first orbiting scroll 2 can be made of an aluminum-based material, which has lower strength and lower density than those of a cast-iron-based material.

[0090] In the two-stage scroll compressor 100 according to Embodiment 5, Mb is the mass of a balancer 31, Rb is the orbital radius of the center of gravity of the balancer 31, Morbl is the mass of the first orbiting scroll 2, R1 is the orbital radius of the first orbiting scroll 2, Morb2 is the mass of the second orbiting scroll 5, R2 is the orbital radius of the second orbiting scroll 5, and the two orbiting scrolls satisfy Equation (6) described below.

[0091] Mb x Rb = Morbl x R1 + Morb2 x R2 (6) [0092] In comparison between the first orbiting scroll 2 made of a cast-iron-based material and the first orbiting scroll 2 made of an aluminum-based material, these orbiting scrolls having the same shape and the same orbital radius, the value of Morb1 of the first orbiting scroll 2 made of an aluminum-based material, which has lower density than that of a cast-iron-based material, is smaller than that of the first orbiting scroll 2 made of a cast-iron-based material. Therefore, the mass of the balancer 31, the orbital radius of the center of gravity of the balancer 31, or both of them can be reduced based on Equation (7).

[0093] The first orbiting scroll 2 may be made of a cast-iron-based material, whereas the second orbiting scroll 5 may be made of an aluminum-based material.

[0094] (Advantages of Embodiment 5) As described above, in the two-stage scroll compressor 100 according to Embodiment 5, one of the two orbiting scrolls is made of an aluminum-based material, and the other orbiting scroll is made of a cast-iron-based material.

[0095] In the two-stage scroll compressor 100 according to Embodiments, one of the two orbiting scrolls is made of an aluminum-based material, and the other orbiting scroll is made of a cast-iron-based material. Thus, the mass of the balancer 31, the orbital radius of the center of gravity of the balancer 31, or both of them can be reduced. This can reduce the cost of a material for the balancer 31 and increase the space in the sealed container 11. Reference Signs List [0096] 1: first fixed scroll, 1a: first discharge port, lb: first fixed scroll wrap, 1c: first fixed baseplate, 1d: sub-port, 2: first orbiting scroll, 2b: first orbiting scroll wrap, 2c: first orbiting baseplate, 2d: first orbiting bearing, 2e: first orbiting key groove, 3: first frame, 3a: bearing, 3b: thrust bearing, 3c: through-hole, 3e: first frame key groove, 4: second fixed scroll, 4a: second discharge port, 4b: second fixed scroll wrap, 4c: second fixed baseplate, 4e: through-hole, 5: second orbiting scroll, 5b: second orbiting scroll wrap, 5c: second orbiting baseplate, 5d: second orbiting bearing, 5e: second orbiting key groove, 6: second frame, 6a: bearing, 6b: passage, 6c: second suction port, 6d: through-hole, 6e: second frame key groove, 7: crankshaft, 7a: first eccentric portion, 7b: second eccentric portion, 8: suction pipe, 9: discharge pipe, 10: injection pipe, 11: sealed container, 12: first compression chamber, 13: second compression chamber, 14: first valve guard, 15: first valve, 16: second valve guard, 17: second valve, 18: rotor, 19: stator, 20: oil sump, 21: oil pump, 22: low-pressure space, 23: intermediate-pressure space, 24: high-pressure space, 25: first Oldham ring, 25a: ring portion, 25b: first Oldham key, 26: second Oldham ring, 26a: ring portion, 26b: second Oldham key, 28: sub-port valve guard, 29: sub-port valve, 30: chamber, 31: balancer, 35: first compression mechanism, 36: second compression mechanism, 37: drive mechanism, 100: two-stage scroll compressor

Claims

CLAIMS [Claim 1] A two-stage scroll compressor comprising: a sealed container serving as a shell; a drive mechanism disposed in the sealed container and serving as a driving source; two compression mechanisms disposed above and below the drive mechanism and each having a compression chamber defined by a combination of a fixed scroll fixed in the sealed container and an orbiting scroll configured to be driven by the drive mechanism; a crankshaft configured to transmit a driving force from the drive mechanism to the two orbiting scrolls; and a balancer disposed on the crankshaft and configured to remove an unbalanced condition caused by the two orbiting scrolls, the two orbiting scrolls being offset from a central axis of the crankshaft in a same direction.
[Claim 2] The two-stage scroll compressor of claim 1, wherein the balancer is offset from the central axis of the crankshaft in a direction opposite to the direction in which the two orbiting scrolls are offset.
[Claim 3] The two-stage scroll compressor of claim 1 or 2, further comprising: two Oldham rings configured to inhibit rotation of the orbiting scrolls, wherein the two Oldham rings are configured to perform simple harmonic motion in orthogonal directions.
[Claim 4] The two-stage scroll compressor of any one of claims 1 to 3, wherein the sealed container has three internal spaces including a low-pressure space from which a fluid is sucked by one of the two compression mechanisms, an intermediate-pressure space into which the fluid compressed by the one of the two compression mechanisms is discharged, and a high-pressure space into which the fluid compressed by an other one of the two compression mechanisms is discharged, and wherein the two compression mechanisms include: a first compression mechanism configured to compress the fluid sucked from the low-pressure space and discharge the compressed fluid into the intermediate-pressure space; and a second compression mechanism configured to compress the fluid sucked from the intermediate-pressure space and discharge the compressed fluid into the high-pressure space.
[Claim 5] The two-stage scroll compressor of claim 4 as dependent on claim 3, wherein the two Oldham rings satisfy 0.95 (Mold2 x R2/Mold1 x R1) 1.05 where Mold1 is a mass of the Oldham ring of the first compression mechanism, Mold2 is a mass of the Oldham ring of the second compression mechanism, R1 is an orbital radius of the orbiting scroll of the first compression mechanism, and R2 is an orbital radius of the orbiting scroll of the second compression mechanism.
[Claim 6] The two-stage scroll compressor of claim 4, wherein the two orbiting scrolls satisfy 0.95 (Morb2 x R2/Morbl x R1) 1.05 where Morb1 is a mass of the orbiting scroll of the first compression mechanism, Morb2 is a mass of the orbiting scroll of the second compression mechanism, R1 is an orbital radius of the orbiting scroll of the first compression mechanism, and R2 is an orbital radius of the orbiting scroll of the second compression mechanism.
[Claim 7] The two-stage scroll compressor of claim 4, wherein the two orbiting scrolls satisfy 2 (Morb1 x R1)/(Morb2 x R2) 3 or 2 (Morb2 x R2)/(Morb1 x R1) 3 where Morb1 is a mass of the orbiting scroll of the first compression mechanism, Morb2 is a mass of the orbiting scroll of the second compression mechanism, R1 is an orbital radius of the orbiting scroll of the first compression mechanism, and R2 is an orbital radius of the orbiting scroll of the second compression mechanism.
[Claim 8] The two-stage scroll compressor of claim 7, wherein the two orbiting scrolls satisfy 2 (Morbl x R1)/(Morb2 x R2) 3 and the balancer is disposed such that Lb > Lorb1/2 is satisfied, or the two orbiting scrolls satisfy 2 (Morb2 x R2)/(Morb1 x R1) 3 and the balancer is disposed such that Lb < Lorb1/2 is satisfied where Lb is a height to a position of a center of gravity of the balancer with respect to a position of a center of gravity of the orbiting scroll of the second compression mechanism and Lorbl is a height to a position of a center of gravity of the orbiting scroll of the first compression mechanism with respect to the position of the center of gravity of the orbiting scroll of the second compression mechanism.
[Claim 9] The two-stage scroll compressor of any one of claims 6 to 8, wherein one of the two orbiting scrolls comprises an aluminum-based material and an other one of the two orbiting scrolls comprises a cast-iron-based material.