ES2983467T3 - ROTARY COMPRESSOR - Google Patents

Abstract

The present invention provides a rotary compressor having increased efficiency while ensuring the reliability of the sliding bearings between the eccentric shaft portions and the rotors. This is achieved by reducing the axial width and diameter of the eccentric shaft portions and thereby reducing the shear loss of the oil film between the eccentric shaft portions and the rotors. A rotary compressor is provided in which a drive shaft 14 includes eccentric shaft portions 15, 16, and rotors 25, 26 rotatably movably mounted on the eccentric shaft portions 15, 16, respectively, are configured to rotatably move eccentrically along inner peripheral surfaces of cylinder chambers 17, 18 to thereby compress refrigerant gas or other gases, and further wherein bearing rings 33, 34 are provided between the eccentric shaft portions 15, 16 and the rotors 25, 26, and axial widths of the eccentric shaft portions 15, 16 and the bearing rings 33, 34 are smaller than axial widths of the rotors 25, 26.

Description

DESCRIPTION

Rotary compressor

Technical sector

The present invention relates to a rotary compressor in which support rings are provided between eccentric shaft portions of the drive shaft and respective rotors fitted to the eccentric shaft portions for rotatably moving within cylinder chambers.

State of the art

Rotary compressors include an eccentric shaft portion on the drive shaft and are configured to compress a refrigerant gas or other gases by eccentrically rotating a rotor, fitted to the eccentric shaft portion in a rotatably movable manner, along the inner peripheral surface of a cylinder chamber. In such rotary compressors, a sliding bearing is formed between the eccentric shaft portion of the drive shaft and the inner peripheral surface of the rotor, which is rotatably movably fitted to the eccentric shaft portion. The rotation of the drive shaft causes an oil film shear loss due to shearing of the lubricating oil film formed between the sliding bearing surfaces, which results in a reduction in efficiency by an amount corresponding to the associated power loss (mechanical loss). Such an oil film shear loss can be reduced by reducing the axial width and diameter of the eccentric shaft portion so that the shear loss can be reduced (the shear loss is reduced in proportion to the surface area of the sliding bearing). However, the lubricating oil film becomes thinner and the probability of contact between solids increases, which promotes wear and coolant leakage and leads to reduced reliability.

BP 1 describes a rotary compressor as follows. The rotary compressor includes a dual rotor structure having an annular inner rotor provided between an eccentric shaft portion and a rotor so that the number of revolutions of the outer rotor can be reduced. With this configuration, the oil holding capacity of the contact portion between the outer rotor and a blade (vane) can be increased. In addition, an edge notch is provided between the inner rotor and the outer rotor to form an intermediate pressure chamber so that the pressure difference can be reduced. As a result, refrigerant leakage can be reduced and, therefore, an improvement in compression efficiency can be achieved.

BP 2 describes a 2-cylinder rotary compressor including upper and lower cylinder bodies with a separator plate between them that partitions them. In this rotary compressor, in order to minimize refrigerant leakage through seal portions between the separator plate and the rotor edges, the upper eccentric shaft portion is configured to have a large outer diameter and the lower eccentric shaft portion is configured to have a small outer diameter relative to the diameter of the through hole formed in the separator plate. With this configuration, the drive shaft can be passed through the separator plate for mounting, and thus the need for a structure with separate drive shafts is eliminated. EP1850009, JP2014231752 and US 2011/058970 present known examples of compressors.

List of quotes

Patent Bibliography

BP 1

Japanese Unexamined Utility Model Application, Publication No. S60-92791

BP 2

Japanese National Republic of PCT International Publication No. WO2013/057946

Similar rotary compressors are also known from EP1850009 A2, US2011058970 A1 and JP 2014231752 A.

Object of the invention

Technical problem

The rotary compressor described in BP 1 includes a dual-rotor structure having both inner and outer rotors to reduce the number of revolutions of the outer rotor compared with the case of using a single rotor (N > Ni > No, where N is the number of revolutions of the single rotor, Ni is the number of revolutions of the inner rotor, and No is the number of revolutions of the outer rotor), to thereby reduce the amount of refrigerant leakage. However, this compressor is not of the type in which the efficiency is increased by reducing the shear loss due to the oil film formed between the eccentric shaft portion of the driving shaft and the rotor and thus the associated loss (mechanical loss) is reduced.

The compressor described in BP 2 is designed to minimize refrigerant leakage through seal portions between the separator plate and the rotor edges by reducing the diameter of the lower eccentric shaft portion. However, BP 2 does not suggest an increase in efficiency by reducing the shear loss due to the oil film formed between the sliding bearing surfaces of the eccentric shaft portion and the rotor and thus reducing the associated power loss (mechanical loss) by reducing the diameter of the eccentric shaft portion.

The present invention has been developed under the circumstances described above. Accordingly, an object of the present invention is to provide a rotary compressor in which the efficiency is increased by reducing the axial width and diameter of the eccentric shaft portion and thereby reducing the oil film shear loss between the eccentric shaft portion and the rotor while ensuring the reliability of the sliding bearing between the eccentric shaft portion and the rotor.

Solution to the problem

In order to solve the problems described above, a rotary compressor of the present invention employs the following means. A rotary compressor according to one aspect of the present invention is defined in claim 1, and includes: a drive shaft including an eccentric shaft portion at a predetermined axial location; a cylinder body forming a cylinder chamber corresponding to the eccentric shaft portion; an upper bearing mounted on an upper surface of the cylinder body and a lower bearing mounted on a lower surface of the cylinder body, the upper and lower bearings defining the cylinder chamber and rotatably supporting the drive shaft; a rotor fitted to the eccentric shaft portion to rotatably move within the cylinder chamber; and a support ring which is a sliding bearing provided between the eccentric shaft portion and the rotor, wherein axial widths of the eccentric shaft portion and the support ring are smaller than an axial width of the rotor.

In this aspect, the rotary compressor is configured such that the drive shaft includes an eccentric shaft portion, and a rotor rotatably movably fitted to the eccentric shaft portion is rotatably eccentrically moved along the inner peripheral surface of the cylinder chamber to thereby compress a refrigerant gas or other gases, and further a support ring is provided between the eccentric shaft portion and the rotor. Furthermore, axial widths of the eccentric shaft portion and the support ring are reduced relative to the axial width of the rotor. Sufficiently reduced axial widths of the support ring and the eccentric shaft portion result in a reduced sliding bearing surface area between them and the rotor, so that the oil film shear loss is proportionally reduced. Furthermore, as a result of the interposition of the support ring between the eccentric shaft portion and the rotor, the support ring and the rotor each have an angular velocity that is lower than that of a rotor in the case where the rotor directly rotatably fits on the eccentric shaft portion. Accordingly, the use of the support ring reduces the sliding area of the sliding bearing surfaces to reduce the oil film shear loss and thereby improves the efficiency. Although the contact pressure P applied to the eccentric shaft portion increases by an amount corresponding to the reduction in the sliding area of the sliding bearing surfaces, the use of the support ring reduces the sliding speed V between the rotor and the eccentric shaft portion to thereby maintain a constant PV value, so that lubrication reliability is ensured while a reduction in the oil film shear loss is achieved.

In the first aspect described above, the rotary compressor is configured so that: the driving shaft is provided as two eccentric shaft portions at upper and lower locations with a predetermined spacing therebetween; two upper and lower compression mechanisms are provided with a separator plate therebetween, each of the compression mechanisms including a cylinder body forming a cylinder chamber corresponding to one of the eccentric shaft portions and a rotor fitted to the corresponding eccentric shaft portion to rotatably move within the corresponding cylinder chamber; and a support ring which is a sliding bearing is provided between each eccentric shaft portion and each rotor.

In this aspect, the 2-cylinder rotary compressor is configured such that the two compression mechanisms are provided at upper and lower locations with a separator plate therebetween and such that a support ring is provided between the eccentric shaft portion and the rotor in each of the compression mechanisms. Two-cylinder rotary compressors can, in general, provide high efficiency due to, for example, reduced vibration, reduced noise, and higher speed operation, compared to single-cylinder rotary compressors. In such a 2-cylinder rotary compressor according to this aspect, the axial widths of the support rings and the eccentric shaft portions of the two compression mechanisms are reduced sufficiently to reduce the surface areas of the sliding bearing between the eccentric shaft portions and the rotors and, thereby, reduce the oil film shear loss. Furthermore, the use of the support ring reduces the sliding speed V between the rotor and the eccentric shaft portion so that the PV value, which is the product of the sliding speed and the contact pressure P applied to the eccentric shaft portion, is kept constant and thus the lubrication reliability is ensured. Consequently, the increased efficiency due to oil film shear loss and the ensured lubrication reliability are both achieved and thus even higher performance is provided for 2-cylinder rotary compressors.

In the first aspect, the rotary compressor is configured such that the eccentric shaft portion at the lower location has a diameter smaller than a diameter of the eccentric shaft portion at the upper location, the eccentric shaft portion at the lower location being positioned farther from an electric motor coupled to one end of the drive shaft, the eccentric shaft portion at the upper location being positioned closer to the electric motor.

In this aspect, the diameter of the eccentric shaft portion at the lower location, which is positioned farther from the electric motor coupled to one end of the drive shaft, is smaller than the diameter of the eccentric shaft portion at the upper location, which is closer to the electric motor. Accordingly, the eccentric shaft portion at the lower location has not only a reduced axial width but also a reduced diameter, and this reduces the oil film shear loss more effectively (the shear loss is reduced in proportion to the surface area of the sliding bearing). Consequently, the power loss due to the oil film shear loss is further reduced to achieve increased efficiency. In addition, the use of the support ring reduces the sliding speed V between the rotor and the eccentric shaft portion so that the PV value, which is the product of the sliding speed and the contact pressure P applied to the eccentric shaft portion, is kept constant, and thus the lubrication reliability is ensured. In addition, the reduced diameter of the eccentric shaft portion at the lower location makes it possible to reduce, by a corresponding amount, the inner diameter of the through hole formed in the separator plate for passing the eccentric shaft portion at the lower location therethrough for mounting. As a result, the lengths of the seal portions between the separator plate and the rotor of each of the compression mechanisms are increased, and the compression efficiency can also be increased by inhibiting refrigerant leakage through the seal portions.

Advantageous effects of the invention

With the present invention, sufficiently reduced axial widths of the support rings and the eccentric shaft portions result in reduced sliding bearing surface areas between them and the rotors, which reduces the oil film shear loss proportionally. Furthermore, as a result of the interposition of the support rings between the eccentric shaft portions and the rotors, the support rings and the rotors each have an angular velocity which is lower than that of the rotors in the case where the rotors directly rotatably fit the eccentric shaft portions. Accordingly, the use of support rings improves efficiency by reducing the sliding bearing surface areas, and thus the oil film shear loss is reduced. Although the contact pressure P applied to the eccentric shaft portion increases by an amount corresponding to the reduction in the sliding area of the sliding bearing surfaces, the use of the support ring reduces the sliding speed V between the rotor and the eccentric shaft portion to thereby maintain a constant PV value, so that lubrication reliability is ensured while a reduction in oil film shear loss is achieved.

Description of the figures

Figure 1 is a longitudinal cross-sectional view of a rotary compressor according to a first embodiment of the present disclosure which is not covered by the scope of the claims;

Figure 2A is an enlarged cross-sectional view of a portion of the compression mechanism of the rotary compressor, Figure 2B is a cross-sectional view of its upper cylinder body, and Figure 2C is a cross-sectional view of its lower cylinder body;

Figure 3 is a longitudinal cross-sectional view of a rotary compressor according to a second embodiment of the present invention; and

Figure 4A is an enlarged cross-sectional view of a portion of the compression mechanism of the rotary compressor, Figure 4B is a cross-sectional view of its upper cylinder body, and Figure 4C is a cross-sectional view of its lower cylinder body.

Detailed description of the invention

Embodiments of the present invention will be described below with reference to the drawings.

First realization

The first embodiment of the present disclosure, which is not covered by the scope of the claims, will now be described with reference to Figures 1 and 2. Figure 1 is a longitudinal cross-sectional view of a rotary compressor according to a first embodiment of the present disclosure, which is not covered by the scope of the claims, Figure 2A is an enlarged cross-sectional view of its compression mechanism portion, Figure 2B is a cross-sectional view of its upper cylinder body, and Figure 2C is a cross-sectional view of its lower cylinder body. Although in the illustrated example a rotary compressor 1 of the present embodiment is a 2-cylinder rotary compressor, the present invention is not limited thereto and can be applied to a single-cylinder rotary compressor, as will be appreciated.

The rotary compressor 1 is an electric compressor of a sealed structure including a cylindrical sealed casing 2 sealed at upper and lower ends by covers 3, 4 with an electric motor 5 provided in an upper region in the casing and compression mechanisms 6 (rotary compression mechanisms) to be driven by the electric motor 5 provided in a lower region thereof. Multiple mounting feet 7 are provided on the lower outer periphery of the sealed casing 2. An outlet pipe 8 is provided in an upper region of the sealed casing 2 to pass through the upper cover 3. High-pressure refrigerant gas compressed by a compression mechanism 6 and discharged in the sealed casing 2 can be released to the outside of the compressor (refrigeration cycle) through the outlet pipe 8.

An accumulator 9 is integrally fixed to the outer periphery of the sealed casing 2 to separate the liquid fraction, such as oil, and liquid refrigerant, contained in the low-pressure refrigerant gas returned from the refrigeration cycle so that only the gas fraction can be sucked into the compression mechanism 6 through the inlet pipes 10, 11. The separated oil is returned to the compressor from the bottom of the accumulator 9 in small increments through small openings formed in the inlet pipes 10, 11.

The electric motor 5 includes a stator 12 and a rotor 13, and the stator 12 is secured to the inner peripheral surface of the sealed housing 2 by shrink fit, press fit, or other means. A drive shaft 14 is integrally coupled to the rotor 13 so that the rotary driving force can be transmitted to the compression mechanism 6 via the drive shaft 14. In lower regions of the drive shaft 14, an upper eccentric shaft portion 15 and a lower eccentric shaft portion 16 with a phase difference of 180 degrees are provided at upper and lower two locations with a predetermined axial spacing therebetween. The upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 correspond to an upper rotary compression mechanism 6A and a lower rotary compression mechanism 6B of the compression mechanism 6 described below, respectively.

The compression mechanism 6 (rotary compression mechanism) is a 2-cylinder rotary compression mechanism including the upper rotary compression mechanism 6A and the lower rotary compression mechanism 6B. The upper rotary compression mechanism 6A and the lower rotary compression mechanism 6B respectively include an upper cylinder body 19 and a lower cylinder body 20 which respectively form an upper cylinder chamber 17 and a lower cylinder chamber 18 and are secured within the sealed casing 2 to correspond respectively to the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 of the drive shaft 14.

The upper rotary compression mechanism 6A and the lower rotary compression mechanism 6B include: a spacer plate 21 interposed between the upper cylinder body 19 and the lower cylinder body 20 to define the upper cylinder chamber 17 and the lower cylinder chamber 18, the spacer plate 21 having a through hole 22 through which the lower eccentric shaft portion 16 can pass; an upper bearing 23 mounted on the upper surface of the upper cylinder body 19 to define the upper cylinder chamber 17 and support the drive shaft 14 in a manner allowing it to rotate; and a lower bearing 24 mounted on the lower surface of the lower cylinder body 20 to define the lower cylinder chamber 18 and support the drive shaft 14 in a manner allowing it to rotate.

The upper rotary compression mechanism 6A and the lower rotary compression mechanism 6B include: an upper rotor 25 and a lower rotor 26 rotatably movably fitted to the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16, respectively, to rotatably eccentrically move within the upper cylinder chamber 17 and the lower cylinder chamber 18, and vanes 27, 28 (see Fig. 2) slidably fitted in vane grooves (not illustrated) formed in the upper cylinder body 19 and the lower cylinder body 20 to respectively partition the upper cylinder chamber 17 and the lower cylinder chamber 18 into the inlet side and the outlet side.

The low-pressure refrigerant gas can be sucked into the upper cylinder chamber 17 of the upper rotary compression mechanism 6A and the lower cylinder chamber 18 of the lower rotary compression mechanism 6B from the inlet pipes 10, 11 through the inlet ports 29, 30. The refrigerant can be compressed by the rotary motion of the upper rotor 25 and the lower rotor 26 to be discharged into the outlet chambers 31, 32 through outlet ports and outlet valves (not illustrated), and after being discharged from there into the sealed casing 2, the refrigerant is directed to the upper end of the sealed casing 2 so that it can be discharged to the refrigeration cycle through the outlet pipe 8.

In the 2-cylinder rotary compression mechanism 6, any one of the upper bearing 23, the upper cylinder body 19 and the lower cylinder body 20 is secured to the inner peripheral surface of the sealed casing 2 by plug welding, stamping or other means. The other components are integrally fitted and secured to any one of the secured upper bearing 23, upper cylinder body 19 and lower cylinder body 20 by bolts or other means. A predetermined amount of lubricating oil is stored in a lower portion within the sealed casing 2 and, accordingly, sliding regions within the compression mechanism 6 may be provided with the lubricating oil by oil supply holes formed in the drive shaft 14 as is known.

The above-described configuration is a typical configuration for the 2-cylinder rotary compressor 1. The present embodiment further employs the following configuration in order to reduce oil film shear loss that occurs as a result of shearing of lubricant films formed between the sliding bearing surfaces of the upper eccentric shaft portion 15 and the upper rotor 25 fitted to the eccentric shaft portion 15 and between the sliding bearing surfaces of the lower eccentric shaft portion 16 and the lower rotor 26 fitted to the eccentric shaft portion 16. Figures 2A, 2B and 2C are enlarged views of the main portion.

The upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 located in lower regions of the drive shaft 14, at upper and lower locations with a predetermined axial spacing therebetween, are provided with a phase difference of 180 degrees with respect to each other. The annular support rings 33, 34 rotatably fit on the outer peripheries of the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16, respectively. The upper rotor 25 and the lower rotor 26 rotatably fit on the outer peripheries of the support rings 33, 34, respectively. That is, the support ring 33 is interposed between the upper eccentric shaft portion 15 and the upper rotor 25 with the support ring 33 being rotatable with respect to each of them and the support ring 34 is interposed between the lower eccentric shaft portion 16 and the lower rotor 26 with the support ring 34 being rotatable with respect to each of them.

Therefore, the following relationship is satisfied:

col = co2 co3

where w is the angular velocity of rotors in the case where the rotors fit directly on the eccentric shaft portions; and w2 is the angular velocity of the support rings 33, 34 and «3 is the angular velocity of the rotors 25, 26, in the case where the rotors 25, 26 are fitted on the eccentric shaft portions with the support rings 33, 34 interposed between them. Consequently, the following relations hold:

The axial widths of the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 are each h1, and the axial widths of the support rings 33, 34 fitted to their outer peripheries have the same widths h1. On the other hand, the upper rotor 25 and the lower rotor 26, which are rotatably movable within the upper cylinder chamber 17 and the lower cylinder chamber 18, have a width h2, which is slightly smaller than the axial widths of the upper cylinder chamber 17 and the lower cylinder chamber 18. The width h2 is determined depending on the axial widths of the upper cylinder body 19 and the lower cylinder body 20, and the width h1 of the upper eccentric shaft portion 15, the lower eccentric shaft portion 16 and the support crowns 33, 34 is set to be sufficiently small with respect to the width h2 (h1 < h2).

With the above-described configurations, the present embodiment provides the following functions and advantages. In the above-described rotary compressor 1 (sealed type electric compressor), once the compression mechanism 6 is driven by rotation of the electric motor 5, low-pressure refrigerant gas is sucked into the upper cylinder chamber 17 of the upper rotary compression mechanism 6A and the lower cylinder chamber 18 of the lower rotary compression mechanism 6B of the accumulator 9 through the inlet pipes 10, 11 and the inlet ports 29, 30. The refrigerant gas is compressed by the eccentric rotary motion of the upper rotor 25 and lower rotor 26 and then discharged into the outlet chambers 31, 32 through the outlet ports and outlet valves (not illustrated).

The compressed gas is discharged from the outlet chambers 31, 32 into the sealed housing 2 for a time and then directed into an upper space within the sealed housing 2 through, for example, a coolant passage formed between the sealed housing 2 and the electric motor 5 and from there the compressed gas is discharged to the outside of the compressor (refrigeration cycle) through the outlet pipe 8.

During the compression operation, lubricating oil is supplied to sliding regions of the upper and lower rotary compression mechanisms 6A, 6B to provide lubrication, for example, between the drive shaft 14 and the upper bearing 23 and between the drive shaft 14 and the lower bearing 24, between the upper eccentric shaft portion 15 and the support ring 33 and between the lower eccentric shaft portion 16 and the support ring 34, between the support ring 33 and the upper rotor 25 and between the support ring 34 and the lower rotor 26, between the upper rotor 25 and the inner peripheral surface of the upper cylinder chamber 17 and between the lower rotor 26 and the inner peripheral surface of the lower cylinder chamber 18, between the vane 27 and the outer peripheral surface of the upper rotor 25 and between the vane 28 and the outer peripheral surface of the lower rotor 26, between the vanes 27, 28 and the respective vane slots ...es 27, 28 and the respective vane slots, between the upper rotor 25 and the inner peripheral surface of the lower rotor 26, and between the upper rotor 25 and the inner peripheral surface of the lower rotor 26. upper rotor 25 and upper bearing 23, between lower rotor 26 and lower bearing 24, and between rotors 25, 26 and spacer plate 21.

In ordinary rotary compressors, a sliding bearing is formed between the eccentric shaft portion of the driving shaft and the inner peripheral surface of the rotor, which is rotatably fitted into the eccentric shaft portion. The rotation of the driving shaft causes oil film shear loss due to shearing of the lubricating oil film formed between the sliding bearing surfaces, and the efficiency is reduced by a corresponding amount. Such oil film shear loss can be reduced by reducing the axial width and diameter of the eccentric shaft portion (the shear loss is reduced in proportion to the surface area of the sliding bearing). However, the contact pressure applied to the eccentric shaft portion increases and thus the lubricating oil film becomes thinner, resulting in a greater probability of contact between solids to promote wear and refrigerant leakage and consequently leading to reduced reliability. The present embodiment employs the configuration in which the support ring 33 is interposed between the upper eccentric shaft portion 15 and the upper rotor 25 with the support ring 33 being rotatable with respect to each of them and the support ring 34 is interposed between the lower eccentric shaft portion 16 and the lower rotor 26 with the support ring 34 being rotatable with respect to each of them. Furthermore, the axial width h1 of the support rings 33, 34, the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 is sufficiently small with respect to the axial width h2 of the upper rotor 25 and the lower rotor 26 (h1 < h2).

Accordingly, the sufficiently small axial width h1 of the support rings 33, 34, the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 reduces the sliding bearing surface areas therebetween and the upper and lower rotors 25, 26, so that the oil film shear loss is proportionally reduced. Furthermore, the support ring 33 is interposed between the upper eccentric shaft portion 15 and the upper rotor 25 and the support ring 34 is interposed between the lower eccentric shaft portion 16 and the lower rotor 26. As a result, the angular velocities of the support rings 33, 34 and θ3 of the upper rotor 25 and the lower rotor 26 are each smaller than the angular velocity θ1 of the rotors in the case where the rotors are directly rotatably fitted to the eccentric shaft portions as described above. Accordingly, an improvement in efficiency is achieved by the reduced oil film shear loss, which is achieved by sufficiently reducing the axial width h1 of the support rings 33, 34, the upper eccentric shaft portion 15 and the lower eccentric shaft portion 16 and thereby reducing the sliding areas of the sliding bearing surfaces. The reduction of the sliding areas of the sliding bearing surfaces increases, by a corresponding amount, the contact pressure P applied to the eccentric shaft portions. The use of the support rings 33, 34 reduces the sliding speed V between the eccentric shaft portions 15, 16 with the support rings 33, 34 and the upper and lower rotors 25, 26, so that the PV value is kept constant and the lubrication reliability is ensured. As a result, the increased efficiency due to a reduced oil film shear loss and the ensured lubrication reliability are both achieved. Second Embodiment

Next, the second embodiment of the present invention will be described with reference to Figures 3 and 4. The present embodiment differs from the first embodiment in that the diameter of the lower eccentric shaft portion 16A is smaller than the diameter of the upper eccentric shaft portion 15. The other features are the same as those of the first embodiment, and therefore, the description thereof is not repeated.

The present embodiment employs a configuration in which, of the upper and lower eccentric shaft portions of the drive shaft 14 arranged with a predetermined axial spacing therebetween, a lower eccentric shaft portion 16A, which is the lower one, has a diameter d2 which is smaller than a diameter d1 of the upper eccentric shaft portion 15 (d1 > d2) in addition to having the axial width h1, which is smaller than the axial width h2 of the upper and lower rotors 25, 26.

As will be appreciated, as a result of the reduction of the diameter d2 of the lower eccentric shaft portion 16A relative to the diameter d1 of the upper eccentric shaft portion 15, the inner diameter of the support ring 34A, which rotatably fits the lower eccentric shaft portion 16A, is correspondingly reduced. With respect to the angular velocities f>4 of the support ring 34A and <cu>5 of the rotor 26, the relationship ~ ,r)^ is maintained as in the first embodiment and the conditions described above are also satisfied in this embodiment. In this configuration, the diameter of a shaft end portion 14A, which extends downward from the lower end of the lower eccentric shaft portion 16A and is supported by the lower bearing 24, is also reduced. However, this does not present a particular problem since the lower bearing 24 is employed as an auxiliary bearing unlike the upper main bearing 23.

In this embodiment, not only the axial width h1 of the lower eccentric shaft portion 16A and the support ring 34A is reduced but also the diameter d2 of the lower eccentric shaft portion 16A is reduced, and therefore, the lower eccentric shaft portion 16A has the axial width h1 reduced and the diameter d2 reduced in combination, which reduces the oil film shear loss more effectively (the shear loss is reduced in proportion to the surface areas of the sliding bearing).

Therefore, a further reduction in power loss due to oil film shear loss is achieved, so that efficiency is increased. Furthermore, the use of the support rings 33, 34A reduces the sliding velocities V between the rotors 25, 26 and the eccentric shaft portions 15, 16A to thereby maintain the PV values, which are the product of the sliding velocities and the contact pressures P applied to the eccentric shaft portions 15, 16A, to be constant, so that suitable oil films are formed to ensure lubrication reliability and prevent wear and coolant leakage due to oil film depletion. As a result, both increased efficiency and lubrication reliability are achieved.

Furthermore, the reduced diameter d2 of the lower eccentric shaft portion 16A makes it possible to reduce, by a corresponding amount, the inner diameter of the through hole 22, which is formed in the separator plate 21 to allow the eccentric shaft portion 16A to pass therethrough for mounting. As a result, the lengths of the seal portions formed between the separator plate 21 and the upper and lower rotors 25, 26 are increased, and by minimizing the leakage of refrigerant through the seal portions, the compression efficiency can also be increased.

The present invention is not limited to the embodiments described above, and may be modified appropriately without departing from the scope of the invention. For example, in the above embodiments, the descriptions have been provided by way of examples in which the present invention is applied to 2-cylinder rotary compressors 1, but it is apparent that the same advantages can also be obtained when the invention is applied to a single-cylinder rotary compressor having a single-cylinder chamber, and therefore, as will be appreciated, the present invention encompasses single-cylinder rotary compressors.

Also, as will be understood, the present invention is applicable to 2-stage compressors having two cylinders with one of the cylinder chambers arranged on the downstream side and the cylinder chamber of the other cylinder arranged on the upstream side.

List of reference signs

1 rotary compressor

5 electric motor

6 compression mechanism (rotary compression mechanism)

6A top rotating compression mechanism

6B lower rotating compression mechanism

14 motor shaft

15 upper eccentric shaft portion

16, 16A lower eccentric shaft portion

17 upper cylinder chamber

18 lower cylinder chamber

19 upper cylinder body

20 lower cylinder body

21 separator plate

23 upper bearing

24 lower bearing

25 upper rotor

26 lower rotor

33, 34, 34A support crown

h1 axial width of upper and lower eccentric shaft portions and support rings h2 axial width of upper and lower rotors

d1 diameter of upper eccentric shaft portion

d2 diameter of lower eccentric shaft portion

Claims (1)

1. A rotary compressor (1), comprising: a drive shaft (14) comprising an eccentric shaft portion (15, 16) at a predetermined axial location; a cylinder body (19, 20) forming a cylinder chamber (17, 18) corresponding to the eccentric shaft portion (15, 16); an upper bearing (23) mounted on an upper surface of the cylinder body (19, 20) and a lower bearing (24) mounted on a lower surface of the cylinder body (19, 20), the upper and lower bearings (23, 24) defining the cylinder chamber (17, 18) and rotatably supporting the drive shaft (14); a rotor (25, 26) fitted to the eccentric shaft portion (15, 16) for rotatably moving within the cylinder chamber (17, 18); and a support crown (33, 34) which is a sliding bearing provided between the eccentric shaft portion (15, 16) and the rotor (25, 26), where the axial widths of the eccentric shaft portion (15, 16) and the support ring (33, 34) are equal and are smaller than an axial width of the rotor (25, 26), wherein the drive shaft (14) comprises two eccentric shaft portions at upper and lower locations with a predetermined spacing therebetween, characterized by that two upper and lower compression mechanisms (6A, 6B) being provided with a separating plate (21) between them, each of the compression mechanisms (6A, 6B) comprising a cylinder body (19, 20) forming a cylinder chamber (17, 18) corresponding to one of the eccentric shaft portions (15, 16) and a rotor (25, 26) fitted to the corresponding eccentric shaft portion (15, 16) to move, in a rotatable manner, within the corresponding cylinder chamber (17, 18), and wherein a support ring (33, 34) which is a sliding bearing is provided between each eccentric shaft portion (15, 16) and each rotor (25, 26), and wherein the eccentric shaft portion (16) at the lower location has a smaller diameter than a diameter of the eccentric shaft portion (15) at the upper location, the eccentric shaft portion (16) at the lower location being positioned further away from an electric motor (5) coupled to one end of the motor shaft (14), the eccentric shaft portion (15) at the upper location being positioned closer to the electric motor (5).