US20230132581A1 - Scroll compressor - Google Patents

Scroll compressor Download PDF

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Publication number
US20230132581A1
US20230132581A1 US17/910,426 US202017910426A US2023132581A1 US 20230132581 A1 US20230132581 A1 US 20230132581A1 US 202017910426 A US202017910426 A US 202017910426A US 2023132581 A1 US2023132581 A1 US 2023132581A1
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United States
Prior art keywords
scroll
φos
tier
involute
orbital
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Abandoned
Application number
US17/910,426
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English (en)
Inventor
Yuji Takamura
Tomokazu Matsui
Kohei TATSUWAKI
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Filing date
Publication date
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Assigned to MITSUBISHI ELECTRIC CORPORATION reassignment MITSUBISHI ELECTRIC CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: TAKAMURA, YUJI, MATSUI, TOMOKAZU, TATSUWAKI, Kohei
Publication of US20230132581A1 publication Critical patent/US20230132581A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/02—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/02—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
    • F04C18/0207—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form
    • F04C18/0215—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form where only one member is moving
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/02—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
    • F04C18/0207—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form
    • F04C18/0246—Details concerning the involute wraps or their base, e.g. geometry
    • F04C18/0269—Details concerning the involute wraps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/02—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
    • F04C18/0207—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form
    • F04C18/0246—Details concerning the involute wraps or their base, e.g. geometry
    • F04C18/0269—Details concerning the involute wraps
    • F04C18/0276—Different wall heights
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00—Components
    • F04C2240/20—Rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2250/00—Geometry
    • F04C2250/20—Geometry of the rotor

Definitions

  • the present disclosure relates to a scroll compressor configured to compress a working medium.
  • Hitherto known scroll compressors are each configured to compress a working medium in a plurality of compression chambers defined between scroll wraps of a fixed scroll and an orbiting scroll that are made to mesh with each other.
  • the working medium is compressed when the orbiting scroll undergoes an orbital motion about the fixed scroll.
  • a scroll compressor is disclosed by Patent Literature 1, in which a scroll start portion, also regarded as a scroll center portion, of a scroll wrap has a tiered shape whose thickness is reduced from the base toward the tip.
  • Patent Literature 1 among a plurality of compression chambers, an innermost compression chamber and a second compression chamber on the radially outer side of the innermost compression chamber are made to communicate to each other in a graded manner by employing the tiered scroll start portion.
  • the stress generated at the base of the scroll start portion is reduced.
  • discussions on some issues have not been made specifically, including which region of the scroll start portion is to be shaped in tiers. Therefore, whether the stress is reduced satisfactorily is unclear.
  • the present disclosure is to solve at least one of the above problems and provides a scroll compressor in which the stress generated at the base of the scroll start portion is small.
  • a scroll compressor is configured to compress a working medium in a plurality of compression chambers defined between an orbital scroll wrap of an orbiting scroll and a fixed scroll wrap of a fixed scroll that are made to mesh with each other.
  • the working medium is compressed when the orbiting scroll driven through a main shaft undergoes an orbital motion about the fixed scroll.
  • the orbital scroll wrap and the fixed scroll wrap include respective scroll start portions each having a bulbous shape defined by connecting an involute start point of an outer-surface involute curve and an involute start point of an inner-surface involute curve to each other with a plurality of arcs.
  • At least one of the scroll start portions has a tiered shape in which an n number (where n ⁇ 2) of tiers each having the bulbous shape are stacked in an axial direction of the main shaft.
  • involute-start-point angles of the outer-surface involute curves in the respective tiers of the scroll start portion having the tiered shape be ⁇ os(1), ⁇ os(2), ⁇ os(3), . . . , and ⁇ os(n) in order from a tip toward a base of the scroll start portion, the following relationships are satisfied: ⁇ os(1)> ⁇ os(2)> ⁇ os(3)> . . . > ⁇ os(n); and 0.3 ⁇ os(1)- ⁇ os(n) ⁇ 0.7 ⁇ .
  • a scroll compressor is configured to compress a working medium in a plurality of compression chambers defined between an orbital scroll wrap of an orbiting scroll and a fixed scroll wrap of a fixed scroll that are made to mesh with each other.
  • the working medium is compressed when the orbiting scroll driven through a main shaft undergoes an orbital motion about the fixed scroll.
  • the orbital scroll wrap and the fixed scroll wrap include respective scroll start portions each having a bulbous shape defined by connecting an involute start point of an outer-surface involute curve and an involute start point of an inner-surface involute curve to each other with a plurality of arcs.
  • At least one of the scroll start portions has a tiered shape in which an n number (where n ⁇ 2) of tiers each having the bulbous shape are stacked in an axial direction of the main shaft.
  • the orbiting scroll and the fixed scroll are made of respective materials having different coefficients of linear expansion. Letting the tiers of the scroll start portion be defined as a first tier, a second tier, . . .
  • the scroll start portion since the scroll start portion has the tiered shape, among the plurality of compression chambers, the innermost compression chamber and the second compression chamber on the radially outer side of the innermost compression chamber are made to communicate with each other in a graded manner. Thus, the stress generated at the base of the scroll start portion is reduced. Furthermore, satisfying the relationship of 0.3 ⁇ os(1)- ⁇ os(n) ⁇ 0.7 ⁇ brings a satisfactory degree of strength improvement for the scroll start portion.
  • the scroll start portion of the scroll wrap made of the material having the greater coefficient of linear expansion is kept supported by the lateral face of the scroll wrap of the scroll made of the material having the smaller coefficient of linear expansion until the pressure is completely equalized between two of the compression chambers, namely the innermost compression chamber and the second compression chamber that are not made to communicate with each other before the scroll wraps go out of contact with each other.
  • Such a configuration suppresses the generation of a great stress at the base of the scroll start portion of the scroll wrap made of the material having the greater coefficient of linear expansion.
  • the scroll start portion of the scroll wrap made of the material having the smaller coefficient of linear expansion is designed such that, during operation, the gaps from the other scroll wrap made of the material having the greater coefficient of linear expansion become smaller than in a case where no relief is provided. Such a configuration suppresses the generation of a great stress at the base of the scroll start portion.
  • FIG. 1 schematically illustrates a longitudinal section of a scroll compressor according to Embodiment 1.
  • FIG. 2 includes diagrams illustrating a scrolling motion undergone by the scroll compressor according to Embodiment 1 in a compression process.
  • FIG. 3 schematically illustrates a lateral section of a compression portion included in the scroll compressor according to Embodiment 1.
  • FIG. 4 is an enlarged perspective view of a scroll start portion of a fixed scroll included in the scroll compressor according to Embodiment 1.
  • FIG. 5 is an enlarged perspective view of a scroll start portion of an orbiting scroll included in the scroll compressor according to Embodiment 1.
  • FIG. 6 is a further enlarged plan view of the scroll start portion of the fixed scroll included in the scroll compressor according to Embodiment 1.
  • FIG. 7 includes enlarged plan views of the scroll start portions of the fixed scroll and the orbiting scroll included in the scroll compressor according to Embodiment 1.
  • FIG. 8 illustrates how the pressure acts on a scroll start portion according to a comparative example at the start of pressure equalization.
  • FIG. 9 illustrates how the pressure acts on the scroll start portion of the scroll compressor according to Embodiment 1 at the start of pressure equalization.
  • FIG. 10 illustrates how the pressure acts on the scroll start portion of the scroll compressor according to Embodiment 1 after the completion of pressure equalization.
  • FIG. 11 illustrates the change in the stress generated at the base of the scroll start portion versus the change in the crank angle in the scroll compressor according to Embodiment 1.
  • FIG. 12 is an enlargement of the scroll start portion of the scroll compressor according to Embodiment 1 in a case where ⁇ os(1)- ⁇ os(n) is 0.2 ⁇ .
  • FIG. 13 is an enlargement of the scroll start portion of the scroll compressor according to Embodiment 1 in a case where ⁇ os(1)- ⁇ os(n) is 0.5 ⁇ .
  • FIG. 14 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion in a known configuration taken as the comparative example and the thickness of the scroll start portion that receives the load.
  • FIG. 15 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.2 ⁇ .
  • FIG. 16 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.5 ⁇ .
  • FIG. 17 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.7 ⁇ .
  • FIG. 18 illustrates the result of a strength analysis conducted on the scroll start portion of the scroll compressor according to Embodiment 1.
  • FIG. 19 is a schematic enlargement of a longitudinal section of the scroll start portion of the scroll compressor according to Embodiment 1 and peripheries thereof.
  • FIG. 20 schematically illustrates a lateral section of a compression unit of a scroll compressor according to Embodiment 2.
  • FIG. 21 is a perspective view of one of reliefs provided in the scroll compressor according to Embodiment 2.
  • FIG. 22 schematically illustrates a lateral section of a compression unit according to a comparative example, with an orbiting scroll being made to uneccentrically mesh with a fixed scroll, and also illustrates gaps produced between an orbital-outer-surface involute and a fixed-inner-surface involute at room temperature.
  • FIG. 23 schematically illustrates a lateral section of the compression unit according to the comparative example, with the orbiting scroll being made to uneccentrically mesh with the fixed scroll, and also illustrates gaps produced between the orbital-outer-surface involute and the fixed-inner-surface involute during operation.
  • FIG. 24 illustrates the gap sizes, ⁇ 0 , of the respective gaps produced at room temperature in the compression unit according to the comparative example, with the orbiting scroll being made to eccentrically mesh with the fixed scroll.
  • FIG. 25 illustrates the changes, ⁇ a, in the sizes of the respective gaps produced in the compression unit according to the comparative example, between the gap sizes at room temperature and the gap sizes during operation.
  • FIG. 26 illustrates the gap sizes, ⁇ s, of the respective gaps produced during operation in the compression unit according to the comparative example.
  • FIG. 27 illustrates the gap sizes ⁇ 0 of the respective gaps produced at room temperature in the compression unit of the scroll compressor according to Embodiment 2, with the orbiting scroll being made to eccentrically mesh with the fixed scroll.
  • FIG. 28 illustrates the effect produced by the reliefs provided in the compression unit of the scroll compressor according to Embodiment 2, that is, the differences, ⁇ b, between the gap sizes at room temperature in the comparative example and the gap sizes during operation in Embodiment 2.
  • FIG. 29 illustrates the gap sizes ⁇ s of the respective gaps produced during operation in the compression unit of the scroll compressor according to Embodiment 2.
  • FIG. 30 schematically illustrates a lateral section of a compression unit of a scroll compressor according to Embodiment 3.
  • FIG. 1 schematically illustrates a longitudinal section of a scroll compressor according to Embodiment 1.
  • the scroll compressor, 1 is configured to suction a working medium such as refrigerant circulating through a refrigerant circuit; compress the working medium into a high-temperature, high-pressure medium; and discharge the high-temperature, high-pressure medium.
  • the scroll compressor 1 includes a compression unit 5 , a motor 4 , and other relevant elements.
  • the motor 4 drives the compression unit 5 through a main shaft 7 .
  • the foregoing elements are housed in a shell 2 , which serves as an outer shell.
  • the compression unit 5 is located in an upper part and the motor 4 is located in a lower part in the shell 2 .
  • the bottom of the shell 2 forms an oil sump 3 a , where lubricant is stored.
  • the shell 2 further houses a frame 6 and a sub frame 20 , which are located across the motor 4 from each other.
  • the frame 6 is located above the motor 4 and between the motor 4 and the compression unit 5 .
  • the sub frame 20 is located below the motor 4 .
  • the frame 6 and the sub frame 20 are fixed to the inner peripheral face of the shell 2 by a method such as shrink fitting or welding.
  • the frame 6 is provided in a central part thereof with a main bearing 8 a .
  • the sub frame 20 is provided in a central part thereof with a counterbearing 8 b .
  • the counterbearing 8 b is, for example, a ball bearing and is press-fitted to the sub frame 20 .
  • the main bearing 8 a and the counterbearing 8 b support the main shaft 7 while allowing the main shaft 7 to rotate.
  • the sub frame 20 is provided with a displacement oil pump 3 .
  • a pump shaft for transmitting a turning force to the oil pump 3 is integrated with the main shaft 7 .
  • the main shaft 7 has an oil hole 7 b .
  • the oil hole 7 b extends through the center of the main shaft 7 from the lower end of the pump shaft to the upper end of the main shaft 7 .
  • the lower end of the oil hole 7 b is connected to the oil pump 3 .
  • the shell 2 includes three parts: an upper shell 2 a , a middle shell 2 b , and a lower shell 2 c .
  • the shell 2 is provided with a suction pipe 11 , for suctioning the refrigerant; and a discharge pipe 12 , for discharging the refrigerant.
  • the refrigerant suctioned into the shell 2 through the suction pipe 11 flows through a suction port 6 a , provided in the frame 6 , and is suctioned into compression chambers 5 a , provided in the compression unit 5 and to be described separately below.
  • the compression unit 5 is configured to compress the refrigerant suctioned thereinto through the suction pipe 11 and to discharge the compressed refrigerant to a high-pressure section provided in an upper part of the shell 2 .
  • the compression unit 5 includes a fixed scroll 30 , an orbiting scroll 40 , an Oldham ring 15 , and other relevant elements.
  • the Oldham ring 15 is configured to prevent the orbiting scroll 40 from spinning on its own axis while the orbiting scroll 40 is undergoing an eccentric circular motion (swirling motion).
  • the fixed scroll 30 is located on the upper side and is fixed to the shell 2 with the frame 6 interposed therebetween.
  • the orbiting scroll 40 is located on the lower side and is supported by the main shaft 7 while being allowed to swirl.
  • the fixed scroll 30 includes a fixed base plate 30 a and a fixed scroll wrap 30 b .
  • the fixed scroll wrap 30 b has a scroll shape and is provided on one face of the fixed base plate 30 a .
  • the orbiting scroll 40 includes an orbital base plate 40 a and an orbital scroll wrap 40 b .
  • the orbital scroll wrap 40 b has a scroll shape and is provided on one face of the orbital base plate 40 a .
  • the fixed scroll wrap 30 b and the orbital scroll wrap 40 b are each shaped in conformity with, for example, an involute curve.
  • the fixed scroll 30 and the orbiting scroll 40 are arranged in the shell 2 such that the fixed scroll wrap 30 b and the orbital scroll wrap 40 b are in mesh with each other.
  • a plurality of compression chambers 5 a are defined between the fixed scroll wrap 30 b and the orbital scroll wrap 40 b . While the main shaft 7 is rotating, the capacities of the compression chambers 5 a decrease in the radial direction from the outer side toward the inner side.
  • the fixed scroll 30 has in a central part thereof a discharge port 30 f , through which the refrigerant having a high pressure by being compressed is discharged.
  • a discharge chamber 13 On the exit side of the discharge port 30 f is provided a discharge chamber 13 .
  • the discharge chamber 13 is provided at the outlet thereof with a discharge valve 13 a , which has a reed-valve structure.
  • a muffler 14 Above the discharge chamber 13 is provided a muffler 14 .
  • the muffler 14 suppresses the pulsation of the working medium discharged from the discharge chamber 13 .
  • the orbital base plate 40 a of the orbiting scroll 40 has an orbital bearing 40 f .
  • the orbital bearing 40 f is provided in a central part of the other face of the orbital base plate 40 a that is opposite the face having the orbital scroll wrap 40 b .
  • the orbital bearing 40 f has a bore, where a slider 9 to be described below is rotatably supported.
  • the center axis of the orbital bearing 40 f is parallel to the center axis of the main shaft 7 .
  • the Oldham ring 15 is located between the orbiting scroll 40 and the frame 6 .
  • the Oldham ring 15 includes a ring portion, a pair of Oldham keys provided on the upper face of the ring portion, and another pair of Oldham keys provided on the lower face of the ring portion.
  • the Oldham keys on the upper face are fitted in respective key grooves provided in the orbiting scroll 40 and are slidable in one direction.
  • the Oldham keys on the lower face are fitted in respective key grooves provided in the frame 6 and are slidable in a direction intersecting the one direction.
  • Such a configuration allows the orbiting scroll 40 to undergo an orbital motion without spinning on its own axis.
  • the motor 4 includes a stator 4 b and a rotor 4 a .
  • the stator 4 b is fixed to the inner periphery of the shell 2 .
  • the rotor 4 a is located on the inner side of the stator 4 b .
  • the rotor 4 a is fixed to the main shaft 7 by shrink fitting or any other method.
  • the stator 4 b receives electric power through a power terminal 21 , which is provided on the shell 2 . When electric power is supplied to the stator 4 b , the rotor 4 a rotates together with the main shaft 7 .
  • the main shaft 7 includes at the upper end thereof an eccentric shaft portion 7 a .
  • the eccentric shaft portion 7 a is shifted from the center axis of the main shaft 7 in a predetermined direction of eccentricity.
  • the eccentric shaft portion 7 a is slidably fitted in the slider 9 to be described below.
  • the slider 9 serves as a variable crank mechanism that makes the radius of the orbital motion of the orbiting scroll 40 vary along the lateral face of the fixed scroll wrap 30 b of the fixed scroll 30 .
  • the variable crank mechanism keeps the lateral face of the fixed scroll wrap 30 b and the lateral face of the orbital scroll wrap 40 b in contact with each other while the orbiting scroll 40 is undergoing the orbital motion.
  • low-pressure gas refrigerant is suctioned into the shell 2 through the suction pipe 11 , is drawn into the compression chambers 5 a through the suction port 6 a provided in the frame 6 , and is compressed in the compression chambers 5 a .
  • the compressed gas refrigerant now having a high pressure is discharged to the discharge chamber 13 through the discharge port 30 f .
  • the high-pressure gas refrigerant in the discharge chamber 13 pushes the discharge valve 13 a upward, flows into the space in the muffler 14 , and is discharged to the inside of the shell 2 through a discharge hole provided in the muffler 14 . Then, the refrigerant is discharged to the outside of the scroll compressor 1 through the discharge pipe 12 .
  • FIG. 2 includes diagrams illustrating a scrolling motion undergone by the scroll compressor according to Embodiment 1 in the compression process.
  • the compression process will now be described. Note that the detailed shape of a scroll center portion, also regarded as a scroll start portion, will be described separately below.
  • the innermost one is referred to as innermost compression chamber 5 a 1
  • the outermost ones are each referred to as outermost compression chamber 5 a 3
  • the ones between the innermost compression chamber 5 a 1 and the outermost compression chambers 5 a 3 are each referred to as second compression chamber 5 a 2 .
  • diagram (a) illustrates a position of the orbiting scroll 40 that is in mesh with the fixed scroll 30 where the outermost compression chambers 5 a 3 are defined at the completion of suction.
  • Diagram (b) illustrates a position of the orbiting scroll 40 that has undergone the orbital motion by 90 degrees from the position of suction completion illustrated in diagram (a).
  • Diagram (c) illustrates a position of the orbiting scroll 40 that has undergone the orbital motion by 180 degrees from the position of suction completion illustrated in diagram (a).
  • Diagram (d) illustrates a position of the orbiting scroll 40 that has undergone the orbital motion by 270 degrees from the position of suction completion illustrated in diagram (a).
  • the orbiting scroll 40 undergoes a swirling motion by taking the positions (a), (b), (c), (d), and (a) in that order. That is, the orbiting scroll 40 undergoes an orbital motion without undergoing a spinning motion. In such a motion, the capacities of the compression chambers 5 a decrease in order of the outermost compression chambers 5 a 3 , the second compression chambers 5 a 2 , and the innermost compression chamber 5 a 1 . Therefore, the suctioned refrigerant is compressed while being sent toward the center, and is discharged from the innermost compression chamber 5 a 1 to the outside of the scroll compressor 1 through the discharge port 30 f provided in the fixed scroll 30 .
  • the fixed scroll 30 and the orbiting scroll 40 each include a scroll start portion, which is also regarded as a scroll center portion of the scroll wrap.
  • the scroll start portion has a so-called bulbous shape defined by connecting the involute start points of respective involute curves forming the inner surface and the outer surface of the scroll start portion to each other with two arcs of a small circle and a large circle.
  • the scroll start portion according to Embodiment 1 has a tiered shape in which a plurality of tiers each having the bulbous shape are stacked in the axial direction of the main shaft 7 .
  • tiered bulbous shape such a shape of the scroll start portion is also referred to as tiered bulbous shape.
  • FIG. 3 schematically illustrates a lateral section of the compressor mechanical unit included in the scroll compressor according to Embodiment 1.
  • FIG. 4 is an enlarged perspective view of the scroll start portion of the fixed scroll included in the scroll compressor according to Embodiment 1.
  • FIG. 5 is an enlarged perspective view of the scroll start portion of the orbiting scroll included in the scroll compressor according to Embodiment 1.
  • the scroll start portion, 30 e of the fixed scroll wrap 30 b of the fixed scroll 30 has, for example, three tiers: a first tier 30 e 1 , a second tier 30 e 2 , and a third tier 30 e 3 in that order from the tip thereof.
  • the scroll start portion 30 e of the fixed scroll wrap 30 b of the fixed scroll 30 have small arc parts, whose positions are sequentially shifted in a direction toward the scroll-starting end and in order in a direction from the tip (the upper side in the drawing) toward the base (the lower side in the drawing).
  • the number of tiers only needs to be n (where n ⁇ 2). That is, the scroll start portion 30 e of the fixed scroll wrap 30 b only needs to have a tiered shape in which an n number (where n ⁇ 2) of tiers each having the bulbous shape are stacked in the axial direction.
  • the one that is nearest to the tip is defined as small arc part 301
  • another one that is closer to the base than the first one is defined as small arc part 301 a
  • the one that is nearest to the base is defined as small arc part 301 b .
  • the small arc part 301 a in the second tier is shifted from the small arc part 301 in the first tier in the direction toward the scroll-starting end.
  • the small arc part 301 b in the third tier is shifted from the small arc part 301 a in the second tier in the direction toward the scroll-starting end.
  • the radius of the large circle defining the scroll start portion 30 e of the fixed scroll wrap 30 b is the same for all of the first tier, the second tier, and the third tier. That is, large arc parts in the respective tiers of the scroll start portion 30 e form a shared large arc part 302 .
  • the fixed scroll 30 comes into contact with the inner surface of the scroll wrap of the orbiting scroll 40 with different timings in the first tier, the second tier, and the third tier in that order.
  • the scroll start portion, 40 e , of the orbital scroll wrap 40 b of the orbiting scroll 40 has, for example, three tiers: a first tier 40 e 1 , a second tier 40 e 2 , and a third tier 40 e 3 in that order from the tip thereof.
  • the scroll start portion 40 e of the orbital scroll wrap 40 b of the orbiting scroll 40 have small arc parts, whose positions are sequentially shifted in a direction toward the start of the scroll and in order in a direction from the tip (the upper side in the drawing) toward the base (the lower side in the drawing).
  • the number of tiers only needs to be n (where n ⁇ 2). That is, the scroll start portion 40 e of the orbital scroll wrap 40 b only needs to have a tiered shape in which an n number (where n ⁇ 2) of tiers each having the bulbous shape are stacked in the axial direction.
  • the one that is nearest to the tip is defined as small arc part 401
  • another one that is closer to the base than the first one is defined as small arc part 401 a
  • the one that is nearest to the base is defined as small arc part 401 b .
  • the small arc part 401 a in the second tier is shifted from the small arc part 401 in the first tier in the direction toward the scroll-starting end.
  • the small arc part 401 b in the third tier is shifted from the small arc part 401 a in the second tier in the direction toward the scroll-starting end.
  • the scroll start portion 40 e of the orbital scroll wrap 40 b of the orbiting scroll 40 is defined by large circles with respective radii.
  • the first tier has a large arc part 402 , which is defined by a large circle with the greatest radius.
  • the second tier has a large arc part 402 a , which is defined by a large circle with a radius smaller than the radius of the large circle defining the large arc part 402 .
  • the third tier has a large arc part 402 b , which is defined by a large circle with a radius smaller than the radius of the large circle defining the large arc part 402 a .
  • the involute-start-point angle of the inner-surface involute curve of the orbiting scroll 40 is the same for all of the first tier, the second tier, and the third tier. Accordingly, the radii of the large circles in the respective tiers of the orbiting scroll 40 vary with the radii of the small circles.
  • the orbiting scroll 40 comes into contact with the inner surface of the scroll wrap of the fixed scroll 30 with different timings in the first tier, the second tier, and the third tier in that order.
  • the tiers in the scroll start portion 30 e of the fixed scroll wrap 30 b and the tiers in the scroll start portion 40 e of the orbital scroll wrap 40 b do not need to be distinguished from each other, they are also simply referred to as the first tier, the second tier, and the third tier with no reference signs.
  • the first tier, the second tier, and the third tier of the fixed scroll 30 are defined by small circles having the same radius and large circles having the same radius, whereas the first tier, the second tier, and the third tier of the orbiting scroll 40 are defined by small circles having different radii and large circles having different radii.
  • the small circle defining the small arc part 401 in the first tier has the smallest radius
  • the small circle defining the small arc part 401 a in the second tier has a greater radius than the small circle defining the small arc part 401
  • the small circle defining the small arc part 401 b in the third tier has a greater radius than the small circle defining the small arc part 401 a .
  • the large circle defining the large arc part 402 in the first tier has the greatest radius
  • the large circle defining the large arc part 402 a in the second tier has a smaller radius than the large circle defining the large arc part 402
  • the large circle defining the large arc part 402 b in the third tier has a smaller radius than the large circle defining the large arc part 402 a .
  • the involute-start-point angle of the inner-surface involute curve of the orbiting scroll 40 is the same for all of the first tier, the second tier, and the third tier. Accordingly, the radii of the large circles in the respective tiers of the orbiting scroll 40 vary with the radii of the small circles.
  • FIG. 6 is a further enlarged plan view of the scroll start portion of the fixed scroll included in the scroll compressor according to Embodiment 1.
  • the involute angle (involute-start-point angle) at the point of connection (an involute start point 303 ) between the small arc part 301 in the first tier and the outer-surface involute curve is denoted by ⁇ os(1).
  • the involute angle (involute-start-point angle) at the point of connection (an involute start point 303 a ) between the small arc part 301 a in the second tier and the outer-surface involute curve is denoted by ⁇ os(2).
  • the involute angle (involute-start-point angle) at the point of connection (an involute start point 303 b ) between the small arc part 301 b in the third tier and the outer-surface involute curve is denoted by ⁇ os(3).
  • the involute-start-point angles in the respective tiers are expressed as ⁇ os(1)> ⁇ os(2)> ⁇ os(3). Since the number of tiers is n (where n ⁇ 2), the above expression regarding the involute-start-point angles in the respective tiers is generalized as ⁇ os(1)> ⁇ os(2) . . . > ⁇ os(n).
  • the above configuration of the fixed scroll 30 regarding the involute-start-point angles of the outer-surface involute curves also applies to the scroll center portion of the orbiting scroll 40 , which is not illustrated.
  • the involute-start-point angle of the outer-surface involute curve in the first tier be ⁇ os(1)
  • the involute-start-point angle of the outer-surface involute curve in the second tier be ⁇ os(2)
  • the involute-start-point angle of the outer-surface involute curve in the third tier be ⁇ os(3)
  • FIG. 7 includes enlarged plan views of the scroll start portions of the fixed scroll and the orbiting scroll included in the scroll compressor according to Embodiment 1.
  • Diagram (a) of FIG. 7 illustrates a state (at a crank angle ⁇ of 0) established when the second compression chambers 5 a 2 are just opened to the innermost compression chamber 5 a 1 located at the center.
  • Diagram (b) of FIG. 7 illustrates a state (at a crank angle ⁇ of 0+15 degrees) established when the orbiting scroll undergoes the orbital motion by 15 degrees after the opening.
  • FIG. 7 illustrates a state (at a crank angle ⁇ of 0+30 degrees) established when the orbiting scroll undergoes the orbital motion by 30 degrees after the opening.
  • Diagram (d) of FIG. 7 illustrates a state (at a crank angle of 0+45 degrees) established when the orbiting scroll undergoes the orbital motion by 45 degrees after the opening.
  • Diagram (e) of FIG. 7 illustrates a state (at a crank angle ⁇ of 0+60 degrees) established when the orbiting scroll undergoes the orbital motion by 60 degrees after the opening.
  • Diagram (f) of FIG. 7 illustrates a state (at a crank angle ⁇ of 0+90 degrees) established when the orbiting scroll undergoes the orbital motion by 90 degrees after the opening.
  • each contact point t is at the involute-start-point angle ⁇ os(1) of the involute curve in the first tier.
  • the fixed scroll wrap 30 b and the orbital scroll wrap 40 b go out of contact with each other in the first tier, whereby the second compression chamber 5 a 2 is made to communicate with the innermost compression chamber 5 a 1 through a passage 50 (see FIG. 9 to be referred to below).
  • the passage 50 is provided as a gap between the first tier and the second tier. Consequently, the high-pressure refrigerant in the innermost compression chamber 5 a 1 flows into the second compression chambers 5 a 2 , whereby the pressure starts to be equalized therebetween.
  • the contact point t further moves in the direction in which the involute angles of the involute curves decrease.
  • a passage 51 is further provided as the gap between the second tier and the third tier and makes the second compression chamber 5 a 2 opened to the innermost compression chamber 5 a 1 .
  • the second compression chamber 5 a 2 is made to communicate with the innermost compression chamber 5 a 1 in a graded manner: first in the first tier, subsequently in the second tier, and eventually in the third tier.
  • a known configuration employing a non-tiered scroll start portion and a variable crank mechanism will first be described as a comparative example.
  • the scroll start portion in the known configuration has a shape obtained by omitting the first tier and the second tier from the scroll start portion according to Embodiment 1, so that the third tier extends continuously from the base to the tip.
  • the following description relates to a case of a pressure acting on the scroll start portion of the orbital scroll wrap but also applies to a case of a pressure acting on the scroll start portion of the fixed scroll wrap.
  • FIG. 8 illustrates how the pressure acts on the scroll start portion according to the comparative example at the start of pressure equalization.
  • a load generated by the difference between the pressure in the second compression chamber 5 a 2 and the pressure in the innermost compression chamber 5 a 1 acts on the orbital scroll wrap 40 b .
  • the orbital scroll wrap 40 b and the fixed scroll wrap 30 b are out of contact with each other. Therefore, as illustrated in FIG.
  • the orbital scroll wrap 40 b is tilted by receiving the load generated by the above pressure difference, and a great stress is generated at the base of the orbital scroll wrap 40 b .
  • a stress is also generated in a compressor including no variable crank mechanism and that operates with the lateral faces of the respective scroll wraps being not kept in contact with each other.
  • Embodiment 1 since the scroll start portion has a tiered bulbous shape, the stress generated at the base of the scroll wrap is reduced. Such a mechanism will now be described with reference to FIGS. 9 , 10 , and 11 .
  • FIG. 9 illustrates how the pressure acts on the scroll start portion of the scroll compressor according to Embodiment 1 at the start of pressure equalization.
  • FIG. 10 illustrates how the pressure acts on the scroll start portion of the scroll compressor according to Embodiment 1 after the completion of pressure equalization.
  • the scroll compressor 1 since the scroll compressor 1 according to Embodiment 1 includes a variable crank mechanism, the lateral face of the orbital scroll wrap 40 b and the lateral face of the fixed scroll wrap 30 b are in contact with each other when the scroll compressor 1 is in operation. However, when the contact point t reaches the involute-start-point angle ⁇ os(1) of the involute curve in the first tier, as described above, the fixed scroll wrap 30 b and the orbital scroll wrap 40 b go out of contact with each other in the first tier, whereby the pressure starts to be equalized through the passage 50 . Immediately after the start of such pressure equalization, as illustrated in FIG.
  • the orbital scroll wrap 40 b is in contact with and is thus supported by the lateral face of the fixed scroll wrap 30 b . Therefore, the fixed scroll wrap 30 b exerts a reaction force R against the load, P, generated by the pressure difference between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 and acting on the orbital scroll wrap 40 b . Such a reaction force R reduces the stress generated at the base of the orbital scroll wrap 40 b.
  • FIG. 11 illustrates the change in the stress generated at the base of the scroll start portion versus the change in the crank angle in the scroll compressor according to Embodiment 1.
  • the horizontal axis represents crank angle
  • the vertical axis represents stress.
  • the solid line represents the stress generated at the scroll start portion according to Embodiment 1.
  • the broken line represents the stress generated at the scroll start portion in the known configuration.
  • Embodiment 1 as the crank angle increases as represented by the solid line in FIG. 11 , the stress generated at the scroll start portion increases.
  • the crank angle reaches the involute start point angle in the first tier (in this case, ⁇ of 0-0.3 ⁇ )
  • the first tier is opened, whereby pressure equalization starts.
  • the stress generated at the base of the scroll start portion starts to be reduced.
  • the stress keeps increasing as represented by the broken line.
  • the involute start point angle in this case, ⁇ is 0
  • pressure equalization starts, whereby the stress starts to be reduced.
  • the maximum stress generated at the base of the scroll start portion in the known configuration is ⁇ 2, whereas the maximum stress generated in Embodiment 1 is ⁇ 1, which is smaller than in the known configuration.
  • the involute-start-point angles in the respective tiers that define the tiered bulbous shape of the scroll start portion are in a relationship of ⁇ os(1)> ⁇ os(2) . . . > ⁇ os(n), as described above.
  • the tiered bulbous shape of the scroll start portion according to Embodiment 1 satisfies a relationship of 0.3 ⁇ os(1)- ⁇ os(n) ⁇ 0.7 ⁇ . Satisfying this relationship further reduces the stress generated at the base of the scroll start portion.
  • how the tiered bulbous shape of the scroll start portion varies with the value of “ ⁇ os(1)- ⁇ os(n)” will first be described.
  • FIG. 12 is an enlargement of the scroll start portion of the scroll compressor according to Embodiment 1 in a case where ⁇ os(1)- ⁇ os(n) is 0.2 ⁇ .
  • FIG. 13 is an enlargement of the scroll start portion of the scroll compressor according to Embodiment 1 in a case where ⁇ os(1)- ⁇ os(n) is 0.5 ⁇ .
  • FIG. 14 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion in the known configuration taken as the comparative example and the thickness of the scroll start portion that receives the load.
  • the arrows illustrated in FIG. 14 each represent the direction of the load, which is determined by integrating the differential pressure acting on the bulbous part.
  • the length of each arrow represents the thickness of the scroll start portion in a section of the scroll start portion that is taken along the arrow, in other words, the thickness of the scroll start portion in the direction of the load. What the arrow represents is the same for the diagrams in FIG. 15 to be referred to below.
  • FIG. 14 only the first tier and the n-th tier are illustrated, with the other tiers not illustrated, which also applies to FIGS. 15 to 17 to be referred to below.
  • the stress at the base of the scroll start portion increases in proportion to the working load divided by the section modulus. Therefore, making the section modulus in the direction of the load satisfactorily large is highly effective in terms of strength improvement for the scroll start portion.
  • the thickness of the scroll start portion in the direction of the load is to be made satisfactorily large.
  • the crank angle ⁇ increases from 0-0.5 ⁇ to 0-0.2 ⁇
  • the thickness of the scroll start portion in the direction of the load is reduced.
  • the second compression chamber 5 a 2 is made to communicate with the innermost compression chamber 5 a 1
  • the second compression chamber 5 a 2 is made to communicate with the innermost compression chamber 5 a 1 at a small section modulus. Therefore, a great stress is generated at the base of the scroll start portion.
  • FIG. 15 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.2 ⁇ .
  • FIG. 16 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.5 ⁇ .
  • FIG. 15 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.5 ⁇ .
  • FIG. 17 includes diagrams illustrating the relationship between the direction in which a load acts on the scroll start portion of the scroll compressor according to Embodiment 1 and the thickness of the scroll start portion that receives the load in the case where ⁇ os(1)- ⁇ os(n) is 0.7 ⁇ .
  • the first tier is opened to start pressure equalization at a crank angle ⁇ of 0-0.2 ⁇ , earlier than in the known configuration illustrated in FIG. 14 by 0.2 ⁇ . That is, by the time when the crank angle ⁇ reaches 0, pressure equalization is complete, generating no load.
  • the thickness of the scroll start portion in the direction of the load acting at the opening of the first tier is greater than the thickness at the crank angle ⁇ of 0 in the case illustrated in FIG. 14 . Therefore, the stress generated at the scroll start portion immediately before the opening is smaller than in the known configuration.
  • the difference in the crank angle established at the time of opening is 0.2 ⁇ , the difference in the thickness of the scroll start portion in the direction of the load acting immediately before the opening is small.
  • the effect of strength improvement to be achieved is small.
  • the first tier is opened to start pressure equalization at a crank angle ⁇ of 0-0.5 ⁇ , earlier than in the case illustrated in FIG. 15 by 0.3 ⁇ . Therefore, the stress generated at the scroll start portion is smaller than in the case illustrated in FIG. 15 . Since the thickness of the scroll start portion in the direction of the load acting immediately before the opening is significantly greater than in the known configuration illustrated in FIG. 14 , a high degree of strength improvement is achieved.
  • the first tier is opened to start pressure equalization at a crank angle ⁇ of 0-0.7 ⁇ , earlier than in the case illustrated in FIG. 16 by 0.2 ⁇ . Therefore, the stress generated at the scroll start portion is smaller than in the case illustrated in FIG. 16 .
  • the increment, obtained by changing ⁇ os(1)- ⁇ os(n) from 0.5 ⁇ to 0.7 ⁇ , in the thickness of the scroll start portion in the direction of the load acting immediately before the opening is smaller than the increment obtained by changing ⁇ os(1)- ⁇ os(n) from 0.2 ⁇ to 0.5 ⁇ .
  • the degree of strength improvement achieved by changing ⁇ os(1)- ⁇ os(n) from 0.5 ⁇ to 0.7 ⁇ is lower than by changing ⁇ os(1)- ⁇ os(n) from 0.2 ⁇ to 0.5 ⁇ .
  • a situation means as follows. If the difference in the involute-start-point angle between the first tier and the n-th tier ( ⁇ os(1)- ⁇ os(n)) is small, the increment in the section modulus is very small, resulting in a degree of strength improvement that does not meet the cost increase required for the fabrication of the tiered structure. Furthermore, as ⁇ os(1)- ⁇ os(n) is made greater, the degree of strength improvement becomes lower, that is, the strength does not infinitely increase.
  • FIG. 18 illustrates the result of a strength analysis conducted on the scroll start portion of the scroll compressor according to Embodiment 1.
  • the horizontal axis represents ⁇ os(1)- ⁇ os(n)
  • the vertical axis represents the ratio of stress reduction at the scroll start portion.
  • the stress is reduced significantly in a range of ⁇ os(1)- ⁇ os(n) from 0.3 ⁇ to 0.7 ⁇ , whereas the effect of stress reduction is substantially saturated in a range over 0.7 ⁇ .
  • the bulbous shape of the scroll start portion is designed to satisfy the relationship of 0.3 ⁇ os(1)- ⁇ os(n) ⁇ 0.7 ⁇ where the degree of reduction in the ratio of stress reduction is high, a satisfactory degree of strength improvement is achieved.
  • the limit for completing the pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 before the n-th tier is opened is expressed by the relationship of ⁇ os(1)- ⁇ os(n)>0.3 ⁇ .
  • the n-th tier is opened before the completion of pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 .
  • the n-th tier that is opened before the completion of pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 is no longer supported by the counterpart scroll wrap. Therefore, the relationship of ⁇ os(1)- ⁇ os(n)>0.3 ⁇ is to be satisfied.
  • the n-th tier is kept supported by the counterpart scroll wrap until the pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 is complete to make the pressure difference between the two 0.
  • the sizes of the small circles in the respective tiers of the scroll start portion are determined with no restrictions.
  • the scroll start portion 40 e of the orbital scroll wrap 40 b overlaps the discharge port 30 f and therefore closes a part of the passage provided by the discharge port 30 f .
  • the small circle in the first tier of the scroll start portion 40 e of the orbital scroll wrap 40 b may be set to such a small value as not to close the discharge port 30 f . If the thickness of the first tier of the scroll start portion 40 e is reduced, the discharge port 30 f is not closed. Consequently, the discharge pressure loss is reduced, which produces a secondary effect of performance improvement.
  • FIG. 19 is a schematic enlargement of a longitudinal section of the scroll start portion of the scroll compressor according to Embodiment 1 and peripheries thereof.
  • the curvature radius, R 1 , at the base of the first tier is greater than the curvature radius, Rn, at the base of the n-th tier.
  • the reason the curvature radius R 1 at the base of the first tier can be made greater than the curvature radius at the base of the n-th tier is as follows. In the compression chamber 5 a , a passage that allows leakage tends to be formed at the base of the n-th tier. Therefore, if the curvature radius at the base of the n-th tier is made large, refrigerant leakage occurs, resulting in performance deterioration.
  • the curvature radius R 1 in the first tier can be made greater than the curvature radius Rn at the base of the n-th tier.
  • the curvature radius in each of the second to (n ⁇ 1)-th tiers can also be made greater than the curvature radius Rn at the base of the n-th tier for the same reason.
  • the ratio of the total height, Hn ⁇ 1, of the first to (n ⁇ 1)-th tiers of the scroll start portion to the total height, Hn, of the first to n-th tiers may be set to 25% to 50%. If the ratio is below 25%, the area of the passage for pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 is insufficient. In such a case, when the n-th tier is opened, there remains a pressure difference between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 , failing in achieving a satisfactory degree of strength improvement. If the ratio is above 50%, the stress generated at the base of each of the first to (n ⁇ 1)-th tiers increases. In such a case, the first to (n ⁇ 1)-th tiers may be damaged before the base of the n-th tier is damaged.
  • each of the fixed scroll 30 and the orbiting scroll 40 includes the tiered scroll start portion.
  • only one of the fixed scroll 30 and the orbiting scroll 40 may include the tiered scroll start portion.
  • the scroll compressor is configured to compress a working medium in the plurality of compression chambers 5 a defined between the orbital scroll wrap 40 b of the orbiting scroll 40 and the fixed scroll wrap 30 b of the fixed scroll 30 that are made to mesh with each other.
  • the working medium is compressed when the orbiting scroll 40 driven through the main shaft 7 undergoes an orbital motion about the fixed scroll 30 .
  • the orbital scroll wrap 40 b and the fixed scroll wrap 30 b include respective scroll start portions each having a bulbous shape defined by connecting the involute start point of the outer-surface involute curve and the involute start point of the inner-surface involute curve to each other with a plurality of arcs.
  • At least one of the scroll start portions has a tiered shape in which an n number (where n ⁇ 2) of tiers each having the bulbous shape are stacked in the axial direction of the main shaft 7 .
  • the involute-start-point angles of the outer-surface involute curves in the respective tiers of the scroll start portion having the tiered shape be ⁇ os(1), ⁇ os(2), ⁇ os(3), . . . , and ⁇ os(n) in order from the tip toward the base of the scroll start portion, the following relationships are satisfied: ⁇ os(1)> ⁇ os(2)> ⁇ os(3)> . . . > ⁇ os(n); and 0.3 ⁇ os(1)- ⁇ os(n) ⁇ 0.7 ⁇ .
  • the scroll start portion has the above tiered shape, among the plurality of compression chambers 5 a , the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 on the radially outer side of the innermost compression chamber 5 a 1 are made to communicate with each other in a graded manner. Thus, the stress generated at the base of the scroll start portion is reduced. Furthermore, satisfying the relationship of 0.3 ⁇ os(1)- ⁇ os(n) ⁇ 0.7 ⁇ brings a satisfactory degree of strength improvement for the scroll start portion that meets the cost increase required for the fabrication of the tiered structure. Furthermore, the n-th tier is kept supported by the counterpart scroll wrap until the pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 is complete to make the pressure difference between the two 0.
  • Embodiment 2 will now be described, except some of the features that are the same as those described in Embodiment 1.
  • the orbiting scroll 40 and the fixed scroll 30 each come to have a high temperature, specifically 100 degrees C. or higher. Accordingly, the orbital scroll wrap 40 b and the fixed scroll wrap 30 b undergo thermal expansion. If the orbiting scroll 40 and the fixed scroll 30 are made of respective materials having different coefficients of linear expansion: for example, one of the two is aluminum while the other is cast iron, a high pressure may be applied to the base of each of the scroll start portions as to be described in detail below.
  • Embodiment 2 relates to a technique of reducing the stress generated at the base of each of the scroll start portions because of the difference in the coefficient of linear expansion between the material forming the orbiting scroll 40 and the material forming the fixed scroll 30 .
  • the coefficient of linear expansion of the orbiting scroll 40 is greater than the coefficient of linear expansion of the fixed scroll 30 .
  • FIG. 20 schematically illustrates a lateral section of a compression unit of the scroll compressor according to Embodiment 2.
  • FIG. 21 is a perspective view of one of reliefs provided in the scroll compressor according to Embodiment 2.
  • the fixed scroll wrap 30 b has an inner-surface involute 30 c (hereinafter referred to as fixed-inner-surface involute 30 c ).
  • the fixed-inner-surface involute 30 c has the reliefs, 30 c 1 .
  • the reliefs 30 c 1 are depressions provided in the fixed-inner-surface involute 30 c and extend parallel to the axial direction.
  • the reliefs 30 c 1 are provided to make the fixed-inner-surface involute 30 c and an outer-surface involute 40 d , which is of the orbital scroll wrap 40 b , be partially out of contact with each other (the outer-surface involute 40 d is hereinafter referred to as orbital-outer-surface involute 40 d ).
  • the regions where the reliefs 30 c 1 are to be provided are defined by the following seven parameters:
  • the reliefs 30 c 1 are provided in regions where the following relationships are satisfied:
  • the reliefs 30 c 1 are provided in the fixed-inner-surface involute 30 c such that while the orbiting scroll 40 is undergoing the orbital motion from the crank angle at which the first tier is opened to the crank angle at which the n-th tier is opened, the orbital-outer-surface contact points, excluding the innermost one, on the orbital scroll wrap 40 b that is made of the material having the greater coefficient of linear expansion are out of contact.
  • FIG. 22 schematically illustrates a lateral section of a compression unit according to the comparative example, with an orbiting scroll being made to uneccentrically mesh with a fixed scroll, and also illustrates gaps produced between an orbital-outer-surface involute and a fixed-inner-surface involute at room temperature.
  • FIG. 23 schematically illustrates a lateral section of the compression unit according to the comparative example, with the orbiting scroll being made to uneccentrically mesh with the fixed scroll, and also illustrates gaps produced between the orbital-outer-surface involute and the fixed-inner-surface involute during operation.
  • FIG. 23 schematically illustrates a lateral section of the compression unit according to the comparative example, with the orbiting scroll being made to uneccentrically mesh with the fixed scroll, and also illustrates gaps produced between the orbital-outer-surface involute and the fixed-inner-surface involute during operation.
  • FIG. 24 illustrates the gap sizes, ⁇ 0, of the respective gaps produced at room temperature in the compression unit according to the comparative example, with the orbiting scroll being made to eccentrically mesh with the fixed scroll.
  • FIG. 25 illustrates the changes, ⁇ a, in the sizes of the respective gaps produced in the compression unit according to the comparative example, between the gap sizes at room temperature and the gap sizes during operation.
  • FIG. 26 illustrates the gap sizes, ⁇ s, of the respective gaps produced during operation in the compression unit according to the comparative example.
  • the horizontal axis represents the position of the gaps
  • the vertical axis represents the gap size ( ⁇ m).
  • the points denoted by i are the orbital-outer-surface contact points.
  • the orbital-outer-surface contact points refer to the points where the orbital-outer-surface involute 40 d comes into contact with the fixed-inner-surface involute 30 c when the orbiting scroll 40 is made eccentric to the fixed scroll 30 .
  • the points denoted by i2 are referred to as orbital-inner-surface contact points.
  • the orbital-inner-surface contact points refer to the points where the orbital-inner-surface involute 40 c comes into contact with the fixed-outer-surface involute 30 d when the orbiting scroll 40 is made eccentric to the fixed scroll 30 .
  • the number of gaps produced between the lateral faces of the orbital scroll wrap 40 b and the fixed scroll wrap 30 b when the orbiting scroll 40 is made to uneccentrically mesh with the fixed scroll 30 totals 2 ⁇ 3.
  • three gaps are produced between the orbital-outer-surface involute 40 d and the fixed-inner-surface involute 30 c
  • three gaps are produced between the orbital-inner-surface involute 40 c and the fixed-outer-surface involute 30 d .
  • the gaps at the 2 ⁇ 3 positions are of the same size at room temperature as illustrated in FIG. 22 . Referring to FIG.
  • the gaps between the orbital-outer-surface involute 40 d and the fixed-inner-surface involute 30 c are denoted by ⁇ o1, ⁇ o2, and ⁇ o3 in the direction from the scroll start portion toward the radially outer side. Furthermore, the gaps between the orbital-inner-surface involute 40 c and the fixed-outer-surface involute 30 d are denoted by ⁇ i1, ⁇ i2, and ⁇ i3 in the direction from the scroll start portion toward the radially outer side.
  • the orbiting scroll 40 and the fixed scroll 30 each come to have a high temperature, specifically 100 degrees C. or higher. Accordingly, the orbital scroll wrap 40 b and the fixed scroll wrap 30 b undergo thermal expansion.
  • the orbital scroll wrap 40 b which is made of a material having a greater coefficient of linear expansion than the fixed scroll wrap 30 b , expands to a greater extent than the fixed scroll wrap 30 b as illustrated in FIG. 23 .
  • the changes ⁇ a in the gap sizes during operation from the gap sizes at room temperature increase in the direction from the scroll start portion toward the radially outer side as illustrated in FIG. 23 .
  • the sizes of the gaps ⁇ o1, ⁇ o2, and ⁇ o3 are smaller during operation than at room temperature, and the degrees of reduction in the gap sizes increase toward the radially outer side. Therefore, for the gaps ⁇ o1, ⁇ o2, and ⁇ o3, the changes ⁇ a obtained by subtracting the gap sizes at room temperature from the gap sizes during operation are negative values as illustrated in FIG. 25 and increase toward the radially outer side.
  • the sizes of the gaps ⁇ i1, ⁇ i2, and ⁇ i3 are greater during operation, illustrated in FIG. 23 , than at room temperature, and the degrees of increase in the gap sizes increase toward the radially outer side. Therefore, for the gaps ⁇ i1, ⁇ i2, and ⁇ i3, the changes ⁇ a obtained by subtracting the gap sizes at room temperature from the gap sizes during operation are positive values as illustrated in FIG. 25 and increase toward the radially outer side.
  • the relationship of the sizes of the gaps during operation is expressed as ⁇ o3 ⁇ o2 ⁇ o1 ⁇ i1 ⁇ i2 ⁇ i3. What have been described above are the gaps at room temperature and the gaps during operation with the orbiting scroll 40 being made to uneccentrically mesh with the fixed scroll 30 . In the actual operation, however, the orbiting scroll 40 is made eccentric in the direction of the arrow illustrated in FIG. 23 .
  • the orbital-inner-surface involute 40 c is out of contact with the fixed-outer-surface involute 30 d , leaving gaps therebetween.
  • the gap size ⁇ s of the gaps produced with the orbiting scroll 40 illustrated in FIG. 23 being made eccentric in the direction of the arrow and being expanded during operation referring to FIG. 26 , the gap size ⁇ s of the gap ⁇ o3 is 0, whereas the gap sizes ⁇ s of the other gaps ⁇ o2, ⁇ o1, ⁇ i1, ⁇ i2, and ⁇ i3 are not 0 and increase in that order.
  • the gap ⁇ o1 and the gap ⁇ i1 are the gaps at the scroll start portion. If the scroll compressor is operated with the gap sizes ⁇ s of the gap ⁇ o1 and the gap ⁇ i1 being not 0, the following problem arises. Before the pressure is equalized between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 , the fixed scroll wrap 30 b and the orbital scroll wrap 40 b lose their respective supports at the respective scroll start portions. Therefore, great stresses are generated at the bases of the respective scroll start portions. Hence, the gap sizes ⁇ s of the gap ⁇ o1 and the gap ⁇ i1 at the scroll start portion are required to be 0 or small.
  • the inner-surface involute 30 c is designed in view of the expansion of the orbital scroll wrap 40 b that occurs during operation.
  • the gap ⁇ o3 and the gap ⁇ o2 produced at room temperature and when the orbiting scroll 40 is made to eccentrically mesh with the fixed scroll 30 are originally made satisfactorily large, as illustrated in FIG. 27 .
  • FIG. 27 illustrates the gap sizes ⁇ 0 of the respective gaps produced at room temperature in the compression unit of the scroll compressor according to Embodiment 2, with the orbiting scroll being made to eccentrically mesh with the fixed scroll.
  • FIG. 28 illustrates the effect produced by the reliefs provided in the compression unit of the scroll compressor according to Embodiment 2, that is, the differences, ⁇ b, between the gap sizes at room temperature in the comparative example and the gap sizes during operation in Embodiment 2.
  • the values in FIG. 28 are the sums of the values in FIG. 25 and the values in FIG. 27 .
  • FIG. 29 illustrates the gap sizes ⁇ s of the respective gaps produced during operation in the compression unit of the scroll compressor according to Embodiment 2.
  • the horizontal axis represents the position of the gaps
  • the vertical axis represents the gap size ( ⁇ m).
  • the above state where the gap size ⁇ s of the gap ⁇ o1 is 0 is maintained at least from when the first tier of the scroll start portion is opened until the n-th tier is opened. That is, before the pressure equalization between the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 is complete, the scroll start portion 40 e of the orbital scroll wrap 40 b is supported by the lateral face of the fixed scroll wrap 30 b . Therefore, the generation of a great stress at the base of the scroll start portion is suppressed. Thus, strength improvement is achieved.
  • the scroll start portion 30 e of the fixed scroll wrap 30 b that is deformed in such a manner as to be tilted is supported by the lateral face of the orbital scroll wrap 40 b when the scroll start portion 30 e is deformed by the amount equivalent to the above gap size ⁇ s.
  • the smaller the gap size ⁇ s the smaller the stress generated at the base of the scroll start portion. Comparing the gap size ⁇ s of the gap ⁇ i1 illustrated in FIG. 29 and the gap size ⁇ s of the gap ⁇ i1 in the case illustrated in FIG. 26 where no relief 30 c 1 is provided, the gap size ⁇ s of the gap ⁇ i1 in FIG. 29 is smaller. That is, providing the reliefs 30 c 1 produces an effect of strength improvement for the scroll start portion 30 e of the fixed scroll wrap 30 b as well.
  • the relief 30 c 1 is provided at each of all the contact points on the orbital-outer-surface involute but the innermost one.
  • the relief 30 c 1 only needs to be provided in the fixed-inner-surface involute 30 c such that while the orbiting scroll 40 is undergoing the orbital motion from the crank angle at which the first tier is opened to the crank angle at which the n-th tier is opened, at least the outermost one of the orbital-outer-surface contact points on the orbital scroll wrap 40 b that is made of the material having the greater coefficient of linear expansion is out of contact with the fixed-inner-surface involute 30 c at the orbital-outer-surface contact points.
  • Providing the relief 30 c 1 only at the outermost contact point is regarded as limitedly providing the relief 30 c 1 in a region where the pressure difference is relatively small and refrigerant leakage is less likely to occur. Therefore, the occurrence of refrigerant leakage is suppressed, and high performance is achieved.
  • the number of regions where the reliefs 30 c 1 are to be provided may be determined flexibly in consideration of the strength and performance required for the final product.
  • Embodiment 2 does not necessarily need to be applied to the configuration according to Embodiment 1.
  • the scroll compressor is configured to compress a working medium in the plurality of compression chambers 5 a defined between the orbital scroll wrap 40 b of the orbiting scroll 40 and the fixed scroll wrap 30 b of the fixed scroll 30 that are made to mesh with each other.
  • the working medium is compressed when the orbiting scroll 40 driven through the main shaft 7 undergoes an orbital motion about the fixed scroll 30 .
  • the scroll compressor includes the variable crank mechanism that varies the radius of the orbital motion of the orbiting scroll 40 .
  • the orbital scroll wrap 40 b and the fixed scroll wrap 30 b include respective scroll start portions each having a bulbous shape defined by connecting the involute start point of the outer-surface involute curve and the involute start point of the inner-surface involute curve to each other with a plurality of arcs. At least one of the scroll start portions has a tiered shape in which an n number (where n ⁇ 2) of tiers each having the bulbous shape are stacked in the axial direction of the main shaft 7 .
  • the orbiting scroll 40 and the fixed scroll 30 are made of respective materials having different coefficients of linear expansion.
  • the tiers of the scroll start portion are defined as the first tier, the second tier, . . .
  • the situation where the orbital scroll wrap 40 b and the fixed scroll wrap 30 b go out of contact with each other in the n-th tier of the scroll start portion and, among the compression chambers, two compression chambers that are not made to communicate with each other before the scroll wraps 40 b and 30 b go out of contact with each other are made to communicate with each other is expressed as the n-th tier is opened.
  • the relief 30 c 1 is provided in the fixed scroll wrap 30 b such that while the orbiting scroll 40 is undergoing the orbital motion from the crank angle at which the first tier is opened to the crank angle at which the n-th tier is opened, the outer-surface involute of the scroll wrap of the scroll that is made of the material having the greater coefficient of linear expansion and the inner-surface involute of the scroll wrap of the scroll that is made of the material having the smaller coefficient of linear expansion are out of contact with each other at least at the outermost one of the plurality of contact points where the two involutes are to come into contact with each other.
  • the scroll start portion of the scroll wrap made of the material having the greater coefficient of linear expansion is kept supported by the lateral face of the scroll wrap of the scroll made of the material having the smaller coefficient of linear expansion until the pressure is completely equalized between two of the compression chambers, namely the innermost compression chamber 5 a 1 and the second compression chamber 5 a 2 that are not made to communicate with each other before the scroll wraps go out of contact with each other.
  • Such a configuration suppresses the generation of a great stress at the base of the scroll start portion of the scroll wrap made of the material having the greater coefficient of linear expansion.
  • an effect of strength improvement for the scroll start portion is produced.
  • the scroll start portion of the scroll wrap made of the material having the smaller coefficient of linear expansion is designed such that, during operation, the gaps from the other scroll wrap made of the material having the greater coefficient of linear expansion become smaller than in the case where no relief 30 c 1 is provided.
  • Such a configuration suppresses the generation of a great stress at the base of the scroll start portion.
  • an effect of strength improvement for the scroll start portion is produced.
  • Embodiment 3 will now be described, except some of the features that are the same as those described in Embodiment 1 or 2.
  • FIG. 30 schematically illustrates a lateral section of a compression unit of a scroll compressor according to Embodiment 3.
  • the fixed-inner-surface involute 30 c has the reliefs 30 c 1 .
  • the orbital-outer-surface involute 40 d has reliefs 40 d 1 .
  • the regions where the reliefs 40 d 1 are to be provided are defined by the following seven parameters:
  • the reliefs 40 d 1 are provided in regions where the following relationships are satisfied:
  • the reliefs 40 d 1 are provided in the orbital-outer-surface involute 40 d such that while the orbiting scroll 40 is undergoing the orbital motion from the crank angle at which the first tier is opened to the crank angle at which the n-th tier is opened, the orbital-outer-surface contact points, excluding the innermost one, on the orbital scroll wrap 40 b that is made of the material having the greater coefficient of linear expansion are out of contact with the fixed-inner-surface involute 30 c at the orbital-outer-surface contact points.
  • the relief 40 d 1 is provided at each of all the contact points on the orbital-outer-surface involute but the innermost one.
  • the relief 40 d 1 only needs to be provided in the orbital-outer-surface involute 40 d such that while the orbiting scroll 40 is undergoing the orbital motion from the crank angle at which the first tier is opened to the crank angle at which the n-th tier is opened, at least the outermost one of the orbital-outer-surface contact points on the orbital scroll wrap 40 b that is made of the material having the greater coefficient of linear expansion is out of contact with the fixed-inner-surface involute 30 c at the orbital-outer-surface contact points.
  • the orbiting scroll 40 and the fixed scroll 30 according to Embodiment 3 are made of respective materials having different coefficients of linear expansion.
  • the tiers of the scroll start portion are defined as the first tier, the second tier, . . . , and the n-th tier in order from the tip toward the base of the scroll start portion.
  • the situation where the orbital scroll wrap 40 b and the fixed scroll wrap 30 b go out of contact with each other in the n-th tier of the scroll start portion and the two compression chambers that are not made to communicate with each other before the scroll wraps 40 b and 30 b go out of contact with each other are made to communicate with each other is expressed as the n-th tier is opened.
  • the relief 40 d 1 is provided in the orbital scroll wrap 40 b such that while the orbiting scroll 40 is undergoing the orbital motion from the crank angle at which the first tier is opened to the crank angle at which the n-th tier is opened, the outer-surface involute of the scroll wrap of one of the scrolls that is made of the material having the greater coefficient of linear expansion and the inner-surface involute of the counterpart scroll wrap are out of contact with each other at least at the outermost one of the plurality of contact points where the two involutes are to come into contact with each other.
  • Embodiment 3 The effects produced by Embodiment 3 are the same as those produced by Embodiment 2.

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  • General Engineering & Computer Science (AREA)
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009174406A (ja) * 2008-01-24 2009-08-06 Panasonic Corp スクロール圧縮機
US20160131134A1 (en) * 2013-09-19 2016-05-12 Mitsubishi Electric Corporation Scroll compressor
US20180142687A1 (en) * 2015-06-10 2018-05-24 Mitsubishi Electric Corporation Scroll compressor

Family Cites Families (3)

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Publication number Priority date Publication date Assignee Title
JP2679155B2 (ja) * 1988-09-26 1997-11-19 三菱電機株式会社 スクロール圧縮機
JP3696955B2 (ja) * 1995-12-04 2005-09-21 三菱重工業株式会社 スクロール流体機械
JP2008309020A (ja) * 2007-06-13 2008-12-25 Panasonic Corp スクロール式流体機械

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009174406A (ja) * 2008-01-24 2009-08-06 Panasonic Corp スクロール圧縮機
US20160131134A1 (en) * 2013-09-19 2016-05-12 Mitsubishi Electric Corporation Scroll compressor
US20180142687A1 (en) * 2015-06-10 2018-05-24 Mitsubishi Electric Corporation Scroll compressor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
English Translation JP-2009174406-A (Year: 2009) *

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