# Patent

## Title
Compressor

## Abstract

A compressor is provided that may include a cylinder including an outer cylinder portion and an inner cylinder portion, and a vane portion connected between the outer cylinder portion and inner cylinder portion, which is fixed to a casing. A rolling piston may be slidably coupled to the vane portion to form an outer compression space and an inner compression space while making a turning movement between the outer cylinder portion and the inner cylinder portion. Through this, a weight of a rotating body may be reduced to obtain low power loss with respect to a same cooling power and a small bearing area, thereby reducing refrigerant leakage as well as easily changing a capacity of a cylinder in an expanded manner. Moreover, refrigerant may be discharged in opposite directions in each compression space, thereby reducing vibration noise of the compressor. In addition, a back pressure groove may be formed on an upper surface of a drive transmission portion of the rolling piston, thereby reducing a friction area between the rolling piston and the upper bearing, as well as reducing a friction loss between the rolling piston and the upper bearing due to oil filled into the back pressure groove.

## Background
CROSS-REFERENCE TO RELATED APPLICATION(S)
This application claims priority to Korean Application No. 10-2012-0157207, filed in Korea on Dec. 28, 2012, which is herein expressly incorporated by reference in its entirety.
BACKGROUND
1. Field
A compressor is disclosed herein.
2. Background
In general, a compressor is applicable to a vapor compression type refrigeration cycle (hereinafter, abbreviated as a “refrigeration cycle”), such as a refrigerator, or air conditioner. For a refrigerant compressor, there has been introduced a constant speed compressor, which is driven at a predetermined speed, or an inverter type compressor, in which a rotation speed is controlled.
A compressor can be divided into a hermetic type compressor, in which an electric motor drive, which is a typical electric motor, and a compression unit or device operated by the electric drive are provided together at an inner space of a sealed casing, and an open type compressor in which an electric motor is separately provided outside of the casing. The hermetic compressor is mostly used for household or commercial refrigeration equipment.
The hermetic compressor may be divided into a single hermetic compressor and a multiple hermetic compressor according to a number of cylinders. The single hermetic compressor is provided with one cylinder having one compression space within the casing, whereas the multiple hermetic compressor is provided with a plurality of cylinders each having a compression space, respectively, within the casing.
The multiple hermetic compressor may be divided into a 1-suction, 2-discharge type and a 1-suction, 1-discharge type according to the refrigerant compression mode. The 1-suction, 1-discharge type is a compressor in which an accumulator is connected to a first cylinder among a plurality of cylinders through a first suction passage, and a second cylinder is connected to a discharge side of the first cylinder connected to the accumulator through a second suction passage, and thus, refrigerant is compressed by two stages and then discharged to an inner space of the casing. In contrast, the 1-suction, 2-discharge type is a compressor in which a plurality of cylinders are branched and connected to one suction pipe and refrigerant is compressed in the plurality of cylinders, respectively, and discharged to an inner space of the casing.
FIG. 1 is a longitudinal cross-sectional view of a related art 1-suction, 2-discharge type rotary compressor. As illustrated in the related art 1-suction, 2-discharge type rotary compressor, a motor drive 2 is provided within the casing 1, and a compressor unit or device 3 is provided at a lower side of the motor drive 2. The motor drive 2 and compressor unit 3 are mechanically connected through a crank shaft 23. Reference numerals 21 and 22 denote a stator and a rotor, respectively.
For the compressor unit 3, a main bearing 31 and a sub bearing 32 are fixed to the casing 1 at regular intervals to support the crank shaft 23, and a first cylinder 34 and a second cylinder 35 separated by an intermediate plate 33 are provided between the main bearing 31 and sub bearing 32. An inlet port 33a connected to a suction pipe 11 is formed at or in the intermediate plate 33, and a first suction groove 33b and a second suction groove 33c that communicate with each compression space (V1, V2) of the first cylinder 34 and second cylinder 35 are formed at an end of the inlet port 33a. 
A first eccentric portion 23a and a second eccentric portion 23b are formed on the crank shaft 23 along an axial direction with a distance of about 180° therebetween, and a first rolling piston 36 and a second rolling piston 37 to compress refrigerant are coupled to an outer circumferential surface of the first eccentric portion 23a and the second eccentric portion 23b, respectively. A first vane (not shown) and a second vane (not shown) welded to the first rolling piston 36 and the second rolling piston 37, respectively, to divide first compression space (V1) and second compression space (V2) into a suction chamber and a compression chamber, respectively, are coupled to the first cylinder 34 and the second cylinder 35. Reference numerals 5, 12, 31a and 32a denote an accumulator, a discharge pipe, and discharge ports, respectively.
According to the foregoing related art 1-suction, 2-discharge type rotary compressor, when power is applied to the motor drive 2 to rotate the rotor 22 and the crank shaft 23 of the motor drive 2, refrigerant is alternately inhaled into the first cylinder 34 and the second cylinder 35 while the first rolling piston 36 and the second rolling piston 37 revolve. The refrigerant is subjected to a series of processes of being discharged into an inner space of the casing 1 through the discharge ports 31a, 32a provided in the main bearing 31 and the sub bearing 32, respectively, while being compressed by the first vane of the first rolling piston 36 and the second vane of the second rolling piston 37.
However, according to the foregoing 1-suction, 2-discharge type rotary compressor, the first eccentric portion 23a and the second eccentric portion 23b are eccentrically formed at regular intervals with respect to an axial center in a lengthwise direction of the crank shaft 23, and thus, a moment due to an eccentric load is increased, thereby causing a problem of increasing vibration and friction loss of the compressor. Further, each vane is welded to each rolling piston 36, 37 to divide the suction chamber and the compression chamber, but according to operating conditions, refrigerant leakage is generated between each vane and each rolling piston 36, 37 while they are separated from each other, thereby reducing compressor efficiency.
Taking this into consideration, a 1-cylinder, 2-compression chamber type rotary compressor having two compression spaces in one cylinder has been introduced as disclosed in Korean Patent Registration No. 10-0812934. FIG. 2 is a longitudinal cross-sectional view of a related art 1-cylinder, 2-compression chamber type rotary compressor, and FIG. 3 is a transverse cross-sectional view of a cylinder and a piston in the 1-cylinder, 2-compression chamber type compressor of FIG. 2, taken along line “III-III” of FIG. 2.
As illustrated in FIG. 2, for a 1-cylinder, 2-compression chamber type rotary compressor (hereinafter, abbreviated as a “1-cylinder, 2-compression chamber compressor”) according to the related art, a first compression space (V1) and a second compression space (V2) are formed at an outer side and an inner side of the piston 44, respectively. Further, the piston 44 is fixedly coupled to an upper housing 41 and casing 1, and the cylinder 43 is coupled in a sliding manner, between the upper housing 41 and lower housing 42, to eccentric portion 23c of crank shaft 23 so as to be revolved with respect to the piston 44.
A long hole-shaped inlet port 41a is formed at one side of the upper housing 41 to communicate with each suction chamber of the first compression space (V1) and the second compression space (V2), and a first discharge port 41b and a second discharge port 41c are formed at the other side of the upper housing 41 to communicate with each compression chamber of the first compression space (V1) and the second compression chamber V2 and the discharge space (S2).
As illustrated in FIG. 3, the cylinder 43 may include an outer cylinder portion 45 that forms the first compression space (V1), an inner cylinder portion 46 that forms the second compression space (V2), and a vane portion 47 that connects the outer cylinder portion 45 and the inner cylinder portion 46 to divide the suction chamber and the compression chamber. The outer cylinder portion 45 and the inner cylinder portion 46 are formed in a ring shape, and the vane portion 47 is formed in a vertically raised flat plate shape.
An inner diameter of the outer cylinder portion 45 is formed to be greater than an outer diameter of the piston 44, and an outer diameter of the inner cylinder portion 46 is formed to be less than an inner diameter of the piston 44, and thus, an inner circumferential surface of the outer cylinder portion 45 is brought into contact with an outer circumferential surface of the piston 44 at one point, and an outer circumferential surface of the inner cylinder portion 46 is brought into contact with an inner circumferential surface of the piston 44 at one point, thereby forming the first compression space (V1) and the second compression space (V2), respectively.
The piston 44 is formed in a ring shape, and a bush groove 49 is formed to allow the vane portion 47 of the cylinder 43 to be inserted thereinto in a sliding manner, and a rolling bush 48 is provided at or in the bush groove 45 to allow the piston 44 to make a turning movement. The rolling bush 48 is disposed such that flat surfaces of a semicircular suction side bush 48a and a discharge side bush 48b are brought into contact with the vane portion 47 at both sides thereof.
On the drawing, unexplained reference numerals 43a and 44a are lateral inlet ports.
According to the foregoing related art 1-cylinder, 2-compression chamber compressor, the cylinder 43 coupled to the crank shaft 23 makes a turning movement with respect to the piston 44 to alternately inhale refrigerant into the first compression space (V1) and the second compression space (V2), and the inhaled refrigerant is compressed by the outer cylinder portion 45, the inner cylinder portion 46, and the vane portion 47, and thus, alternately discharged into an inner space of the casing 1 through the first discharge port 41b and the second discharge port 41c. 
As a result, the first compression space (V1) and the second compression space (V2) may be disposed adjacent to each other on the same plane, thereby reducing moment and friction loss. In addition, the vane portion 47, which divides the suction chamber and compression chamber, may be integrally coupled to the outer cylinder portion 45 and the inner cylinder portion 46, thereby enhancing sealability of the compression space.
However, according to the foregoing related art 1-cylinder, 2-compression chamber compressor, the piston 44 is fixed, but the relatively heavy cylinder 43 is rotated, and thus, a high power loss results with respect to the same cooling power and a large bearing area, thereby increasing concerns of refrigerant leakage.
Further, according to the related art 1-cylinder, 2-compression chamber compressor, part of an outer circumferential surface of the cylinder 43 may be closely adhered to an inner circumferential surface of the upper housing 41, and thus, a diameter of the upper housing 41 should be increased to change a volume of the cylinder 43 according to turning movement, and consequently, the casing 1 itself should be changed in an increasing manner, thereby causing a problem in which volume control of the compressor is not so easy.
Furthermore, according to the related art 1-cylinder, 2-compression chamber compressor, the first discharge port 41b and the second discharge port 41c may be formed to extend in the same direction, and thus, refrigerant being discharged first may lead to a so-called pulsation phenomenon, thereby aggravating vibration noise of the compressor.
In addition, according to the related art 1-cylinder, 2-compression chamber compressor, two compression chambers are formed at a same height, and thus, a torque load may be non-uniformly generated according to a change in pressure difference between the compression chambers to destabilize the behavior of the cylinder 43, thereby causing concerns of noise, abrasion, or refrigerant leakage.



BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:
FIG. 1 is a longitudinal cross-sectional view of a related art 1-suction, 2-discharge type rotary compressor;
FIG. 2 is a longitudinal cross-sectional view of a related art 1-cylinder, 2-compression chamber type rotary compressor;
FIG. 3 is a transverse cross-sectional view of a cylinder and a piston, taken along line “III-III” of FIG. 2;
FIG. 4 is a longitudinal cross-sectional view of a 1-cylinder, 2-compression chamber type rotary compressor according to an embodiment;
FIG. 5 is an exploded perspective view of a compression device in the compressor of FIG. 4;
FIG. 6 is a cross-sectional view, taken along line “VI-VI” of FIG. 4;
FIG. 7 is a longitudinal cross-sectional view of the compression device, taken along line “VII-VII” of FIG. 6;
FIG. 8 is a plan view illustrating the standard of a bush groove and a vane portion in the compressor of FIG. 7;
FIG. 9 is a plan view of a back pressure groove in the compression device of FIG. 7 according to an embodiment;
FIG. 10 is a graph illustrating a change in a back pressure area coefficient according to a pressure ratio in the compressor according to embodiments;
FIG. 11 is a graph illustrating a change in a gas power in an inner compression space according to an actual operating area pressure ratio in the compressor according to embodiments;
FIG. 12 is a plan view illustrating a back pressure groove according to another embodiment;
FIGS. 13A-13D are transverse cross-sectional views of a compression process of an outer compression space and an inner compression space in a compressor according to embodiments; and
FIG. 14 is a longitudinal cross-sectional view of a rolling piston and members thereof in a compressor according to another embodiment.



DETAILED DESCRIPTION
Hereinafter, a compressor according to embodiments will be described in detail with reference to the accompanying drawings. Where possible, like reference numerals have been used to indicate like elements, and repetitive disclosure has been omitted.
FIG. 4 is a longitudinal cross-sectional view of a 1-cylinder, 2-compression chamber type rotary compressor according to an embodiment. FIG. 5 is an exploded perspective view of a compression device in the compressor of FIG. 4. FIG. 6 is a cross-sectional view, taken along line “VI-VI” of FIG. 4. FIG. 7 is a longitudinal cross-sectional view of the compression device, taken along line “VII-VII” of FIG. 6. FIG. 9 is a plan view of a back pressure groove in the compression device of FIG. 7 according to an embodiment.
As illustrated in the drawings, according to a 1-cylinder, 2-compression chamber type rotary compressor in accordance with an embodiment, a motor drive 2 that generates a driving force may be provided in an inner space of casing 1, and a compression device 100 having two compression spaces (V1, V2) in one cylinder may be provided at a lower side of the motor drive 2.
The motor drive 2 may include a stator 21 fixed and installed on an inner circumferential surface of the casing 1, a rotor 22 rotatably inserted into an inner side of the 21, and a crank shaft 23 coupled to a center of the rotor 22 to transmit a rotational force to a rolling piston 140, which will be described hereinbelow. The stator 21 may be formed in such a manner that a lamination laminated with a ring-shaped steel plate is shrink-fitted to be fixed and coupled to the casing 1, and a coil (C) may be wound around the lamination. The rotor 22 may be formed in such a manner that a permanent magnet (not shown) is inserted into the lamination laminated with the ring-shaped steel plate. The crank shaft 23 may be formed in a rod shape having a predetermined length and formed with an eccentric portion 23c that eccentrically protrudes in a radial direction at a lower end portion thereof to which the rolling piston 140 may be eccentrically coupled.
The compression unit or device 100 may include an upper bearing plate (hereinafter, referred to as an “upper bearing”) 110 and a lower bearing plate (hereinafter, referred to as an “lower bearing”) 120 provided at predetermined intervals in an axial direction to support the crank shaft 23, a cylinder 130 provided between the upper bearing 110 and the lower bearing 120 to form a compression space (V), and the rolling piston 140 coupled to the crank shaft 23 to compress the refrigerant of the compression space (V) while making a turning movement in the cylinder 130. The upper bearing 110 may be adhered to an inner circumferential surface of the casing 1 in, for example, a welded and coupled manner, and the lower bearing 120 may be fastened to the upper bearing 110 along with the cylinder 130 by, for example, a bolt.
A first discharge port 112a that communicates with first compression space (V1), which will be described hereinbelow, may be formed on the upper bearing 110, and a second discharge port 122a that communicates with second compression space (V2), which will be described later, may be formed on the lower bearing 120. A discharge cover 150 may be coupled to the upper bearing 110 to accommodate the first discharge port 112a, and a lower chamber 160 may be coupled to the lower bearing 120 to accommodate the second discharge port 122a. A discharge passage (F) sequentially passing through the lower bearing 120, the cylinder 130, and the upper bearing 110 may be formed to communicate an inner space of the lower chamber 160 with an inner space of the discharge cover 150.
The upper bearing 110 and the lower bearing 120 may each be formed in a ring shape, and axle receiving portions 111, 121 having axle holes 111a, 121a, respectively, may be formed at a center thereof.
An inner diameter (D1) of the axle hole 111a of the upper bearing 110 may be formed to be greater than an inner diameter (D2) of the axle hole 121a of the lower bearing 120. In other words, the crank shaft 23 may be formed in such a manner that a diameter at a portion brought into contact with the upper bearing 110 may be greater than a diameter at a portion brought into contact with the lower bearing 120 so as to mostly support the upper bearing 110 close to a center of an eccentric load. Accordingly, the second discharge port 122a located at a relatively inner side between the first discharge port 112a and the second discharge port 122a may be formed on the lower bearing 120 not to intrude into the axle receiving portion 121 of the lower bearing 120.
If the rolling piston 140 is turned upside down such that a driving transmission portion 142 comes in contact with the lower bearing 120 and accordingly the first discharge port 112a is closer to the crankshaft 23 than the second discharge port 122a of the lower bearing 120, the first discharge port 112a may intrude into the axis receiving portion 111 of the upper bearing 110 having a relative large outer diameter, thereby lowering bearing strength of the axis receiving portion 111 of the upper bearing 110. By considering this, in order to compensate for the bearing strength as much as the intrusion of the first discharge port 112a, the axis receiving portion 111 of the upper bearing 110 should be lengthened, which may cause an increase a size of the compressor.
As illustrated in FIGS. 5 and 6, the cylinder 130 may include an outer cylinder portion 131 formed in a ring shape, an inner cylinder portion 132 disposed at a predetermined interval therefrom to form a compression space (V) at an inner side of the outer cylinder portion 131, and a vane portion 133 configured to divide the first compression space (V1) and the second compression space (V2) into a suction chamber and a compression chamber, respectively, while at the same time connecting the outer cylinder portion 131 and the inner cylinder portion 132 in a radial direction. The vane portion 133 may be formed between a first inlet port 131b, which will be described hereinbelow, and the first discharge port 112a. 
An outer circumferential surface of the outer cylinder portion 131 may be pressed onto an inner circumferential surface of the casing 1 in, for example, a welded and coupled manner, but an outer diameter of the outer cylinder portion 131 may be formed to be less than an inner diameter of the casing 1 and fastened between the upper bearing 110 and the lower bearing 120 by, for example, a bolt (B1), thereby preventing thermal deformation of the cylinder 130. However, in order to adhere a portion of the outer cylinder portion 131 to the inner circumferential surface of the casing 1, a protruded fixing portion 131a thereof may be formed in a circular arc shape, and the first inlet port 131b, which may pass through the protruded fixing portion 131a in a radial direction to communicate with the first compression space (V1) may be formed thereon. Refrigerant suction pipe 11 connected to accumulator 5 may be inserted and coupled to the first inlet port 131b. 
Further, an upper surface and a lower surface of the outer cylinder portion 131 may be adhered to the upper bearing 110 and the lower bearing 120, respectively, and a plurality of fastening holes 131c may be formed at regular intervals along a circumferential direction. Furthermore, a plurality of discharge guide holes 131d that form a discharge passage (F) may be formed between the plurality of fastening holes 131c. 
An axle hole 132a may be formed in the inner cylinder portion 132 to which the crank shaft 23 may be rotatably coupled to a central portion thereof. A center of the inner cylinder portion 132 may be formed to correspond to a rotational center of the crank shaft 23.
The inner cylinder portion 132 may be formed in such a manner that a height (H2) thereof is lower than a height (H1) of the outer cylinder portion 131. In other words, a lower surface of the inner cylinder portion 132 may be formed in a same plane as a lower surface of the outer cylinder portion 131 to be brought into contact with the lower bearing 120, whereas an upper surface thereof may be formed with a height at which the drive transmission portion 142 of the rolling piston 140, which will be described hereinbelow, may be inserted between the upper bearing 110 and the upper surface thereof.
The cylinder 130 may be fastened to fastening hole 112b of the upper bearing 110 and fastening hole 122b of the lower bearing 120 through the fastening hole 131c formed on the outer cylinder portion 131 of the cylinder 130.
As illustrated in FIGS. 5 through 7, the vane portion 133 may have a predetermined thickness to connect between an inner circumferential surface of the outer cylinder portion 131 and an outer circumferential surface of the inner cylinder portion 132, as described above, and formed in a vertically raised plate shape.
Further, a stepped portion 133a may be formed on an upper surface of the vane portion 133 in such a manner that the drive transmission portion 142 of the rolling piston 140, which will be described hereinbelow, may be placed on part of the inner cylinder portion 132 and the vane portion 133 in a covering manner. Accordingly, when a portion from the outer connecting end 133b to the stepped portion 133a is referred to as a first vane portion 135 and a portion from the inner connecting end 133c to the stepped portion 133a is referred to as a second vane portion 136, a height of the first vane portion 135 in an axial direction may be formed with the same height as a height (H1) of the outer cylinder portion 131 in the axial direction, and a height of the second vane portion 136 in the axial direction may be formed with the same height as a height (H2) of the inner cylinder portion 132 in the axial direction.
A length (L1) of the first vane portion 135 in a radial direction may be formed to be no greater than or substantially the same as an inner diameter (D3) of a bush groove 145 (or outer diameter of the rolling bush 140), which will be described hereinbelow, thereby preventing a gap from being generated between the inner circumferential surface of the outer cylinder portion 131 and the outer circumferential surface of the rolling piston 140 (or an outer circumferential surface of the rolling bush 140). Further, as illustrated in FIG. 8, the length (L1) of the first vane portion 135 in the radial direction may be formed to be greater than a length (L5) of the second vane portion 136 in the radial direction, thereby preventing the stepped portion 133a from being exposed out of the bush groove 145 of the rolling piston 140 when the rolling piston 140 is brought into contact with the inner connecting end 133c of the second vane portion 136.
The rolling piston 140 may include a piston portion 141 disposed between the outer cylinder portion 131 and the inner cylinder portion 132, and the drive transmission portion 142, which may extend from an upper end inner circumferential surface of the piston portion 141 and be coupled to the eccentric portion 23c of the crank shaft 23, as illustrated in FIGS. 5 through 7.
The piston portion 141 may be formed in a ring shape having a substantially rectangular cross section, and an outer diameter of the piston portion 141 may be formed to be less than an inner diameter of the outer cylinder portion 131 to form the first compression space (V1) at an outer side of the piston portion 141, and an inner diameter of the piston portion 141 may be formed to be greater than an outer diameter of the inner cylinder portion 132 to form the second compression space (V2) at an inner side of the piston portion 141. Further, a second inlet port 141a that passes through an inner circumferential surface of the piston portion 141 may be formed to communicate the first inlet port 131b with the second compression space (V2) may be formed, and the bush groove 145 may be formed between one side of the second inlet port 141a, namely, the second inlet port 141a and the second discharge port 122a formed on the lower bearing 120 in such a manner that the vane portion 133 passes through the rolling piston 140, which will be described hereinbelow, therebetween and is slidably inserted thereinto.
The bush groove 145 may be formed in a substantially circular shape, but an outer open surface 145a and an inner open surface 145b with a non-continuous surface on an outer circumferential surface and an inner circumferential surface of the piston portion 141 may be formed in such a manner that the vane portion 133 may pass through and be coupled to the bush groove 145 in a radial direction. The bush groove 145 may be formed in a substantially circular shape, but a portion thereof may be brought into contact with the outer circumferential surface and the inner circumferential surface of the piston portion 141 to have a non-continuous surface. The vane portion 133 may be inserted into the bush groove 145 in a radial direction, and an inlet side bush 171 and a discharge side bush 172 of rolling bush 170 may be inserted and rotatably coupled to both left and right sides of the vane portion 133, respectively. A flat surface of the rolling bush 170 may be slidably brought into contact with both lateral surfaces of the vane portion 133, respectively, and a round surface thereof may be slidably brought into contact with a main surface of the bush groove 145.
The drive transmission portion 142 may be formed as a ring-shaped plate shape having an eccentric portion hole 142a to be coupled to the eccentric portion 23a of the crank shaft 23. Further, a stepped back pressure groove 142b having a predetermined depth and area may be formed to form a back pressure space while at the same time reducing a friction area with a bearing surface of the upper bearing 110, around the eccentric portion hole 142a of the drive transmission portion 142, namely, on an upper surface of the drive transmission portion 142. Though not shown in the drawings, the back pressure groove may be formed on a bearing surface 112c of the upper bearing 110 in an axial direction.
As illustrated in FIG. 9, the back pressure groove 142b may be formed in a ring shape having a same radius with respect to a center (O) of the eccentric portion hole 142a. Further, the back pressure groove 142b may be formed in such a manner that an area of the back pressure groove 142b is less than an area of a bearing surface out of the back pressure groove 142b, thereby preventing refrigerant leakage in the second compression space (V2).
The minimum area (ABP) of the back pressure groove 142b (hereinafter, abbreviated as a “minimum back pressure area”) may be determined by a value in which an average gas power (FAVG) due to a suction chamber pressure (PS) and a compression chamber pressure (PC) of the inner compression space (V2) is divided by a pressure obtained by multiplying the suction chamber pressure with a pressure ratio (PR). In other words, for the minimum back pressure area (ABP), the average gas power (FAVG) may be obtained by the suction chamber pressure (PS) and the compression chamber pressure (PC) of the inner compression space (V2) with respect to the pressure ratio based on an actual operating area, and the minimum back pressure area may be obtained by a discharge pressure (PD). When a minimum pressure ratio (PR) is 1.58 and a maximum pressure ratio (PR) is 7.0, the minimum back pressure area according to an actual operating area pressure ratio may be obtained by the following equation.

0.123×ATOTAL≦ABP=FAVG/(PS×PR)≦0.776×ATOTAL 

where, 0.123 and 0.776 back pressure area coefficients, respectively. Further, the minimum back pressure area in case where the pressure ratio is 1.58 may be obtained by the following equation.

F=PS×AS+PC×AC, F=0.209 kN

FAVG=PS×PR×ABP, ABP=0.776ATOTAL 

where, ATOTAL is an area of the inner compression space.

Using the foregoing equation, the minimum back pressure area may be 0.776ATOTAL when the pressure ratio is 2.30, 0.776ATOTAL when the pressure ratio is 3.40, and 0.776ATOTAL when the pressure ratio is 7.0, respectively.
FIG. 10 is a graph illustrating a change in a back pressure area coefficient according to a pressure ratio in the compressor according to embodiments. As illustrated in the drawing, it is seen that the back pressure area coefficient is increased as the pressure ratio (PR) decreases, and the back pressure area coefficient decreases as the pressure ratio (PR) increases. The compression chamber pressure (PC) may be determined in advance by a standard of the compressor and the suction chamber pressure (PS) may vary according to an installation condition of a cooling cycle, and therefore, it is seen that the back pressure area coefficient increases as the suction chamber pressure (PS) increases, and the back pressure area coefficient decreases as the suction chamber pressure (PS) decreases. Accordingly, the area of the back pressure groove 142b may be relatively increased in a condition where the suction chamber pressure (PS) is high, and the area of the back pressure groove 142b may be relatively decreased in a condition where the suction chamber pressure (PS) is low.
On the other hand, FIG. 11 is a graph illustrating a change in a gas power in an inner compression space according to an actual operating area pressure ratio in the compressor according to embodiments. As illustrated in the drawing, taking into consideration a case where the pressure ratio (PR) is 3.40, it is seen that the gas power (F) is greatly changed according to a rotation angle of the crank shaft 23 (hereinafter, referred to as a “crank angle”). In other words, the gas power is less than the average gas power in a case where the crank angle is between 0° and about 100° (suction section), but the gas power is increased above the average gas power in a case where the crank angle is between about 100° and about 260° (compression section) and decreased again below the average gas power in a case where the crank angle is between about 260° and 360° (discharge section).
The gas power is the highest during the compression section, and accordingly, a highest torque load may be generated during the compression section. Accordingly, a highest back pressure to support the rolling piston 140 may be formed during the compression section, thereby effectively stabilizing a behavior of the rolling piston 140.
To this end, the back pressure groove 142b may be formed in an oval shape at a specific portion as illustrated in FIG. 12. In other words, the back pressure groove 142b may be formed in such a manner that a radius of the back pressure groove 142b, which is a length from geometric center (O) of the rolling piston 140 to a virtual line connected to a center of the back pressure groove in a radial direction, is different along the crank angle, but the largest crank angle is formed during the compression section. However, in this case, the total area and depth of the back pressure groove 142b may be formed similarly to those of the previous embodiment.
On the drawing, unexplained reference numerals 133d is sliding surface, 181 and 182 are first and second discharge valve, respectively.
Operation of a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing configuration according to embodiments will be discussed as follows.
When power is applied to coil (C) of the motor drive 2 to rotate the rotor 22 along with the crank shaft 23, the rolling piston 140 coupled to the eccentric portion 23c of the crank shaft 23 may be supported by the upper bearing 110 and the lower bearing 120 and at the same time guided by the vane portion 133 to alternately form the first compression space (V1) and the second compression space (V2) while making a turning movement between the outer cylinder portion 131 and the inner cylinder portion 132. More specifically, when the rolling piston 140 allows the first inlet port 131b of the outer cylinder portion 131 to be open, refrigerant is inhaled into the suction chamber of the first compression space (V1) and compressed while being moved in the direction of the compression chamber of the first compression space (V1) by the turning movement of the rolling piston 140, as illustrated in FIGS. 13A and 13B, and the refrigerant allows the first discharge valve 181 to be open and is discharged into an inner space of the discharge cover 150 through the first discharge port 112a, as illustrated in FIGS. 13C and 13D. At this time, an upper surface of the vane portion 133 is formed in a stepped manner, but the suction chamber and the compression chamber of the second compression space (V2) may be blocked by the rolling bush 170, thereby preventing leakage of refrigerant.
In contrast, when the rolling piston 140 allows the second inlet port 141a to be open, refrigerant is inhaled into the suction chamber of the second compression space (V2) through the first inlet port 131b and the second inlet port 141a and is compressed while being moved in the direction of the compression chamber of the second compression space (V2) by the rolling piston 140, as illustrated in FIGS. 13C and 13D, and the refrigerant allows the second discharge valve 182 to be open and is discharged into the lower chamber 160 through the second discharge port 122a, and the refrigerant is moved to an inner space of the discharge cover 150 through the discharge passage (F) and exhausted into an inner space of the casing 1, as illustrated in FIGS. 13A and 13B, so as to repeat a series of processes.
According to a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing configuration in accordance with embodiments, the cylinder 130 may be fixed and the rolling piston 140 may perform a turning movement at an inner side of the cylinder 130, and thus, it may be possible to obtain a low power loss with respect to the same cooling power and a small bearing area compared to the rotating movement of a relatively heavy and large cylinder, thereby reducing concerns of refrigerant leakage. Further, according to embodiments, the cylinder 130 may be fixed and the rolling piston 140 may make a turning movement whereas the protruded fixing portion 131a may be formed at one side on an outer circumferential surface of the outer cylinder portion 131 to form a free space (S) between an inner circumferential surface of the casing 1 and an outer circumferential surface of the cylinder 130, and thus, a diameter of the cylinder 130 may be increased using the free space (S), thereby easily changing a capacity of the cylinder 130 in an expanded manner.
Further, according to embodiments, the first discharge port 112a and the second discharge port 122a may be formed in opposite directions to each other, and thus, refrigerant being discharged may be absorbed with each other to reduce a pulsation phenomenon, thereby reducing vibration noise of the compressor.
Furthermore, according to embodiments, the back pressure groove 142b having a predetermined area and depth may be formed on an upper surface of the drive transmission portion 142 of the rolling piston 140 to reduce a friction area between the rolling piston 140 and the upper bearing 110. Moreover, the oiling piston 140 may be slightly pushed out by oil filled into the back pressure groove 142b, thereby reducing friction loss between the rolling piston 140 and upper bearing 110.
In this manner, according to a 1-cylinder, 2-compression chamber type rotary compressor in accordance with embodiments, a cylinder having an outer cylinder portion and an inner cylinder portion may be fixed, and a rolling piston may perform a turning movement at an inner side of the cylinder, and thus, it may be possible to obtain a low power loss with respect to the same cooling power and a small bearing area compared to the rotating movement of a relatively heavy and large cylinder, thereby reducing concerns of refrigerant leakage. Further, the cylinder may be fixed and the rolling piston may make a turning movement whereas the protruded fixing portion may be formed at one side on an outer circumferential surface of the outer cylinder portion to form a free space between an inner circumferential surface of the casing and an outer circumferential surface of the cylinder, and thus, the diameter of the cylinder may be increased using the free space, thereby easily changing the capacity of the cylinder in an expanded manner.
Furthermore, the first discharge port, which communicates with the outer compression space, and second discharge port, which communicates with the inner compression space, may be formed in opposite directions to each other, and thus, refrigerant being discharged may be absorbed with each other to reduce a pulsation phenomenon, thereby reducing the vibration noise of the compressor. Also, the back pressure groove having a predetermined area and depth may be formed on the rolling piston or the upper bearing or lower bearing facing the rolling piston in an axial direction to stably support the axial direction of the rolling piston and due to this the behavior of the rolling piston may be stabilized, thereby preventing noise, abrasion or refrigerant leakage in advance.
A 1-cylinder, 2-compression chamber type rotary compressor according to another embodiment will be described hereinbelow. According to the foregoing embodiment, the drive transmission portion 142 of the rolling piston 140 may be formed to extend from an upper end of the piston portion, but according to this embodiment, the drive transmission portion 142 of the rolling piston 140 may be formed to be extend from a lower end of the piston portion 141, as illustrated in FIG. 14. Even in this case, the back pressure groove 142b may be formed on the drive transmission portion 142 to extend from the lower end of the piston portion 141, or the back pressure groove 142b may be formed on a thrust bearing surface of the lower bearing.
It may be possible to obtain a suitable depth and area of the back pressure groove 142b through the equation defined in the foregoing embodiment. Accordingly, detailed description has been omitted. On the other hand, the basic configuration and working effects thereof in which the drive transmission portion 142 extends from a lower end of the piston portion 141 may be substantially the same as the foregoing embodiment.
However, according to this embodiment, the drive transmission portion 142 may be formed to extend from the lower end of the piston portion 141, and thus, first discharge port 122d may be formed on the lower bearing 120, and second discharge port 112d on the upper bearing 110, respectively. Further, in this case, when the second discharge port 112d is formed in a vertical direction, the second discharge port 112d may interfere with an outer circumferential surface of axle receiving portion 111 of the upper bearing 110 to intrude into part of the outer circumferential surface of the axle receiving portion 111 of the upper bearing 110, and thus, as illustrated in FIG. 13, the second discharge port 112d may be formed to be inclined out of the axle receiving portion 111 of the upper bearing 110.
According to a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing embodiment, the drive transmission portion 142 may be formed at the lower end of the piston portion 141, thereby reducing a friction loss between the rolling piston 140 and the lower bearing 120. In other words, as illustrated, when the drive transmission portion 142 is formed to extend from the upper end of the piston portion 141, a lower surface of the piston portion 141 may receive an entire weight of the rolling piston 140, but the lower surface of the piston portion 141 may provide an adequate sealing area and as a result, a back pressure groove cannot be formed on a lower surface of the piston portion 141. Accordingly, in the previous embodiment, it may be difficult to reduce a friction loss between the lower surface of the piston portion 141 and the lower bearing 120, but as illustrated in this embodiment, when the drive transmission portion 142 is formed at a lower end of the piston portion 141, the back pressure groove 142b may be formed on a lower surface of the drive transmission portion 142, thereby reducing friction loss while the rolling piston 140 rises by a back pressure of oil that flows into the back pressure groove 142b without increasing a friction area.
Embodiments disclosed herein provide a compressor having a low power loss with respect to the same cooling power and a small bearing area capable of reducing a weight of a rotating body, thereby reducing refrigerant leakage.
Embodiments disclosed herein further provide a compressor capable of easily changing a capacity of a cylinder in an expanded manner.
Embodiments disclosed herein additionally provide a compressor in which refrigerant discharged from each compression space is absorbed with each other to reduce a pulsation phenomenon, thereby reducing vibration noise.
Embodiments disclosed herein also provide a compressor capable of enhancing an axial directional supporting force between the rotating body and a bearing that supports the rotating body in a thrust direction, thereby stabilizing a behavior of the rotating body.
Embodiments disclosed herein provide a compressor that may include a casing; a crank shaft configured to transmit a rotational force of a motor drive provided within the casing; a plurality of bearing plates configured to support the crank shaft; a cylinder fixed and coupled between the bearing plates, an outer cylinder portion and an inner cylinder portion of which may be connected to a vane portion to form a compression space; and a rolling piston slidably coupled to the vane portion between the outer cylinder portion and the inner cylinder portion to divide the compression space into an outer compression space and an inner compression space while making a turning movement by the crank shaft. A back pressure groove having a predetermined area and depth may be formed on at least either one surface of the rolling piston and a bearing plate with which the rolling piston is brought into contact.
Further, embodiments disclosed herein provide a compressor that may include a casing; a crank shaft configured to transfer a rotational force of a motor drive provided within the casing; a plurality of bearing plates configured to support the crank shaft; a cylinder fixed and coupled between the bearing plates, an outer cylinder portion and an inner cylinder portion which are connected to a vane portion to form a compression space; and a rolling piston slidably coupled to the vane portion between the outer cylinder portion and the inner cylinder portion to divide the compression space into an outer compression space and an inner compression space while making a turning movement by the crank shaft. A back pressure groove having a predetermined area and depth may be formed on at least either one surface of the rolling piston and a bearing plate with which the rolling piston is brought into contact, and the back pressure groove may be formed with at least one or more sections in which a virtual line connected to a center of a back pressure groove in a radial direction has a different radius from a geometric center of the rolling piston.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

## Claims

1. A compressor, comprising
a casing;
a crank shaft configured to transmit a rotational force of a motor drive provided within the casing to a rolling piston;
a plurality of bearing plates configured to support the crank shaft;
a cylinder fixed and coupled between the plurality of bearing plates, an outer cylinder portion and an inner cylinder portion of which are connected to a vane portion to form a compression space; and
the rolling piston, which is slidably coupled to the vane portion between the outer cylinder portion and the inner cylinder portion to divide the compression space into an outer compression space and an inner compression space while making a turning movement by the crank shaft, wherein a back pressure groove having a predetermined area and depth is formed on the surface of the rolling piston, and wherein the back pressure groove is formed in such a manner that a virtual line connected to a center of the back pressure groove in a radial direction has a different radius from a geometric center of the rolling piston along a rotation angle of the crank shaft.

2. The compressor of claim 1, wherein the back pressure groove is formed in a ring shape.

3. The compressor of claim 1, wherein the back pressure groove is formed in such a manner that the virtual line connected to the center of the back pressure groove in the radial direction has a largest radius from the geometric center of the rolling piston during a compression section of rotation of the crank shaft.

4. The compressor of claim 1, wherein a minimum area (ABP) of the back pressure groove is determined by a value in which an average gas power (FAVG) due to a suction chamber pressure (PS) and a compression chamber pressure (PC) of the inner compression space is divided by a pressure obtained by multiplying the suction chamber pressure with a pressure ratio (PR).

5. The compressor of claim 4, wherein the minimum area (ABP) of the back pressure groove is determined by the following equation:


0.123×ATOTAL≦ABP≦0.776×ATOTAL,

wherein 0.123 and 0.776 are back pressure area coefficients, respectively, and ATOTAL is an area of the inner compression space.

6. The compressor of claim 1, wherein the rolling piston includes:
a piston portion formed in a ring shape and provided between the outer cylinder portion and the inner cylinder portion; and
a drive transmission portion that extends from the piston portion and is coupled to an eccentric portion of the crank shaft.

7. The compressor of claim 6, wherein the back pressure groove is formed on at least one lateral surface of the drive transmission portion that faces the bearing plate or the bearing plate corresponding to the at least one lateral surface of the drive transmission portion.

8. The compressor of claim 7, wherein the drive transmission portion extends from an upper end or a lower end of the piston portion in an axial direction.

9. The compressor of claim 6, wherein the vane portion includes:
a first vane portion connected to an inner circumferential surface of the outer cylinder portion; and
a second vane portion connected to an outer circumferential surface of the inner cylinder portion, and wherein a height of the first vane portion is different from a height of the second vane portion.

10. The compressor of claim 9, wherein the first vane portion and second vane portion are connected to each other at a stepped portion.

11. The compressor of claim 10, wherein a length of the first vane portion in a radial direction is less than or equal to a thickness of the rolling piston in a radial direction.

12. The compressor of claim 10, wherein a length of the first vane portion in a radial direction is formed to be greater than a length of the second vane portion.

13. The compressor of claim 1, wherein the back pressure groove is formed in an upper surface of the rolling piston.

14. The compressor of claim 1, wherein the back pressure groove is formed in a lower surface of an upper bearing plate of the plurality of bearing plates.

15. A compressor, comprising:
a casing;
a crank shaft configured to transfer a rotational force of a motor drive provided within the casing to a rolling piston;
a plurality of bearing plates configured to support the crank shaft;
a cylinder fixed and coupled between the plurality of bearing plates, an outer cylinder portion and an inner cylinder portion of which are connected to a vane portion to form a compression space; and
the rolling piston, which is slidably coupled to the vane portion between the outer cylinder portion and the inner cylinder portion to divide the compression space into an outer compression space and an inner compression space while making a turning movement by the crank shaft, wherein a back pressure groove having a predetermined area and depth is formed on the surface of the rolling piston, wherein the back pressure groove is formed with one or more sections for which a virtual line connected to a center of the back pressure groove in a radial direction has a different radius from a geometric center of the rolling piston, and wherein the back pressure groove is formed in such a manner that the virtual line connected to the center of the back pressure groove in the radical direction has a largest radius from the geometric center of the rolling piston during a compression section of rotation of the crank shaft.

16. The compressor of claim 15, wherein a minimum area (ABP) of the back pressure groove is determined by the following equation:


0.123ΔATOTAL≦ABP≦0.776×ATOTAL,

wherein 0.123 and 0.776 are back pressure area coefficients, respectively, and ATOTAL is an area of the inner compression space.

17. The compressor of claim 15, wherein the rolling piston includes:
a piston portion formed in a ring shape and provided between the outer cylinder portion and the inner cylinder portion; and
a drive transmission portion that extends from the piston portion and is coupled to an eccentric portion of the crank shaft.

18. The compressor of claim 15, wherein the vane portion includes:
a first vane portion connected to an inner circumferential surface of the outer cylinder portion; and
a second vane portion connected to an outer circumferential surface of the inner cylinder portion, and wherein a height of the first vane portion is different from a height of the second vane portion.

19. The compressor of claim 18, wherein the first vane portion and second vane portion are connected to each other at a stepped portion.

20. The compressor of claim 15, wherein the back pressure groove is formed in an upper surface of the rolling piston.

21. The compressor of claim 15, wherein the back pressure groove is formed in a lower surface of an upper bearing plate of the plurality of bearing plates.