[Name of Document]

DESCRIPTION

[Title of Invention]

ROTARY COMPRESSOR

[Technical Field]

[0001]
The present invention relates to a rotary compressor for compressing a refrigerant gas, the rotary compressor being used in a refrigeration cycle of an air-conditioning apparatus or a refrigerating and air-conditioning apparatus, such as a refrigerator. [Background Art]

[0002]
A rotary compressor has been developed that includes a piston slidably attached to an offset portion of a crankshaft, a cylinder including a cylindrical cylinder chamber in which the piston is disposed, and a vane separating the cylinder chamber into a low-pressure side space and a high-pressure side space. In such a rotary compressor, an inner circumferential surface of the cylinder chamber, an outer circumferential surface of the piston, and the vane define a space that serves as a compression chamber. The piston is eccentrically rotated in the cylinder chamber, thereby compressing a refrigerant sucked into the cylinder chamber. Some of such related-art rotary compressors include a piston composed of a plurality of members.

[0003]
The related-art rotary compressors, each including a piston composed of a plurality of members, include a "rotary compressor including a piston that has a double structure composed of a first roller 16a, serving as an outer component, and a second roller 16b, serving as an inner component, and further has holes 24 through which an inner surface of the second roller 16b communicates with an outer surface thereof (refer to Patent Literature 1), this rotary compressor being intended to prevent wear on an outer circumferential surface of the piston caused by sliding of a vane on the outer crcurrrfereritial surface of the piston. [Citation List] [Patent Literature]

[0004]
[Patent Literature 1] Japanese Unexamined Patent Application Publication No.
5-256282 (Abstract, Figs. 1 and 2) [Summary of Invention] [Technical Problem]

[0005]
In the rotary compressor disclosed in Patent Literature 1, the inner piston component (referred to as the "second roller 16b" in Patent Literature 1) slidably attached to the offset portion is a cylindrical single piece. A main shaft or sub-shaft, next to the offset portion, of the crankshaft is inserted through the inner piston component and the inner piston component is then attached to the offset portion. The rotary compressor disclosed in Patent Literature 1 therefore has to be configured such that an outer circumferential surface of the offset portion on a counter-offset side (i.e., the outer circumferential surface thereof facing away from an offset direction of the offset portion) protrudes away from the outer circumferential surface of the main shaft or the sub-shaft. Alternatively, the counter-offset side outer circumferential surface of the offset portion has to be flush with the outer circumferential surface of the main shaft or the sub-shaft.

[0006]
Specifically, as illustrated in Fig. 7(a), a distance between an axis common to a main shaft 4a and a sub-shaft 4b and a counter-offset side outer circumferential surface of an offset portion 4c is expressed by Re-e, where Re denotes the radius of the offset portion 4c and e denotes the amount of offset of the offset portion 4c (or a distance between the axis common to the main shaft 4a and the sub-shaft 4b and the axis of the offset portion 4c). To attach an inner piston component 50 to the offset portion 4c from a main shaft 4a side in the rotary compressor disclosed in Patent Literature 1, therefore, a crankshaft 4 has to be formed such that Re-e > Rm, where Rm denotes the radius of the main shaft 4a. To attach the inner piston component 50 to the offset portion 4c from a sub-shaft 4b side in the rotary compressor disclosed in Patent Literature 1, the crankshaft 4 has to be formed such that Re-e > Ra, where Ra denotes the radius of the sub-shaft 4b.

The reason is as follows. Assuming that, as illustrated in Fig. 7(b), the counter-offset side outer circumferential surface of the offset portion 4c is recessed away from an outer circumferential surface of the main shaft 4a or the sub-shaft 4b (specifically, Re-e < Rm when the inner piston component 50 is attached to the offset portion 4c from the main shaft 4a side or Re-e < Ra when the inner piston component 50 is attached to the offset portion 4c from the sub-shaft 4b side), if the inner piston component 50 is attached to the offset portion 4c, the offset portion 4c will interfere with the inner piston component 50. Unfortunately, the inner piston component 50 cannot be attached to the offset portion 4c.

[0007]
To increase a displacement for enhancement of the capacity of the rotary compressor (high power achievement), the amount of offset (or the amount of offset from the main shaft and the sub-shaft of the crankshaft) of the piston has to be increased while an increase in outside diameter of the piston is suppressed. In other words, to increase the displacement for enhancement of the capacity of the rotary compressor, the amount of offset (or the amount of offset from the main shaft and the sub-shaft of the crankshaft) of the offset portion has to be increased while an increase in the outside diameter of the offset portion is suppressed. As the amount of offset of the offset portion is increased while an increase in the outside diameter of the offset portion is suppressed, the counter-offset side outer circumferential surface of the offset portion 4c is recessed away from the outer circumferential surface of the main shaft 4a or the sub-shaft 4b (namely, Re-e < Rm or Re-e < Ra).

As described above with reference to Fig. 7, however, the piston cannot be attached to the offset portion in the rotary compressor disclosed in Patent Literature 1 unless the relationship between the counter-offset side outer circumferential surface of the offset portion and the outer circumferential surface of the main shaft or the sub-shaft satisfies Re-e > Rm or Re-e > Ra. In the rotary compressor disclosed in Patent Literature 1, therefore, the amount of offset of the offset portion cannot be increased to such an extent that the counter-offset side outer circumferential surface of the offset portion 4c is recessed away from the outer circumferential surface of the main shaft 4a or the sub-shaft 4b while an increase in the outside diameter of the offset portion is suppressed. Disadvantageously, the enhancement of the capacity of the rotary compressor is limited.

[0008]
As regards a method of increasing the displacement of the rotary compressor, the height of each of the piston and the cylinder may be increased while the amount of offset of each of the offset portion and the piston is maintained. The contact between the outer circumferential surface of the piston on an offset side (or the outer circumferential surface of the offset portion facing in the offset direction) and the inner circumferential surface of the cylinder chamber functions as a sealing part that separates the cylinder chamber into the low-pressure side space and the high-pressure side space. Accordingly, increasing the height of each of the piston and the cylinder results in an increase in length of the sealing part. If the height of each of the piston and the cylinder is increased to enhance the capacity of the rotary compressor, therefore, the refrigerant gas may leak from the high-pressure side space to the low-pressure side space, thus reducing the weight flow rate of the refrigerant gas sucked into the compression chamber (cylinder chamber). Disadvantageously, this leads to significantly reduced efficiency of the rotary compressor.

[0009]
The present invention has been made to solve the above-described disadvantages and provides a rotary compressor that allows a displacement to be increased while preventing a reduction in sealing performance between a high-pressure side space and a low-pressure side space in a cylinder chamber. [Solution to Problem]

[0010]
The present invention provides a rotary compressor that includes a motor including a stator and a rotor, a crankshaft including a main shaft fixed to the rotor, a sub-shaft disposed on an opposite side of the crankshaft from the main shaft in an axial direction of the crankshaft, and at least one offset portion disposed between the main shaft and the sub-shaft, the crankshaft being driven by the motor, at least one compression mechanism including a piston slidably attached to the offset portion, a cylinder including a cylindrical cylinder chamber in which the offset portion and the piston are arranged, and a vane separating the cylinder chamber into a low-pressure side space and a high-pressure side space, and a sealed container accommodating the motor, the crankshaft, and the compression mechanism. The piston includes an inner piston component slidably disposed on an outer circumferential surface of the offset portion and an outer piston component disposed on an outer circumferential surface of the inner piston component. The inner piston component includes a plurality of arc-shaped members.

[Advantageous Effects of Invention]

[0011]
In the rotary compressor according to this invention, the piston includes the inner piston component slidably disposed on the outer circumferential surface of the offset portion and the outer piston component disposed on the outer circumferential surface of the inner piston component. The inner piston component includes the plurality of arc-shaped members. Accordingly, in the rotary compressor according to the invention, the arc-shaped members, or the inner piston component can be attached to the offset portion such that the offset portion is sandwiched between the arc-shaped members (in a direction perpendicular to the axis of the offset portion). Consequently, if the crankshaft is shaped such that the outer circumferential surface of the offset portion on a counter-offset side is recessed away from an outer circumferential surface of the main shaft or the sub-shaft, the inner piston component can be attached to the offset portion. The rotary compressor according to the present invention, therefore, allows a displacement to be increased without an increase in height of each of the piston and the cylinder.

Specifically, the rotary compressor according to the invention allows a displacement to be increased without a significant reduction in efficiency caused by refrigerant leakage in the sealing part between the piston and an inner circumferential surface of the cylinder chamber. In other words, the rotary compressor according to the invention allows the piston and the cylinder to have a lower height than that in the related-art rotary compressor unless the displacement is changed. Thus, the refrigerant leakage in the sealing part between the piston and the inner circumferential surface of the cylinder chamber can be reduced more than the related art.

According to the invention, therefore, a rotary compressor capable of achieving higher power and higher efficiency than the related art can be provided.

[Brief Description of Drawings]

[0012]

[Fig. 1] Fig. 1 is a longitudinal sectional view illustrating a rotary compressor according to Embodiment of the invention.

[Fig. 2] Fig. 2 is a cross-sectional view illustrating a compression mechanism of the rotary compressor according to Embodiment of the invention.

[Fig. 3] Fig. 3 includes diagrams explaining an inner piston component of the rotary compressor according to Embodiment of the invention, (a) being a longitudinal sectional view illustrating a crankshaft and the inner piston component, (b) being a plan view of the inner piston component.

[Fig. 4] Fig. 4 is a diagram explaining a method of attaching a piston to an offset portion in the rotary compressor according to Embodiment of the invention, Fig. 4 being a perspective view illustrating a state before assembly of the inner piston component around the offset portion of the crankshaft.

[Fig. 5] Fig. 5 is a diagram explaining the method of attaching the piston to the offset portion in the rotary compressor according to Embodiment of the invention, Fig. 5 being a perspective view illustrating a state before an outer piston component is attached to the inner piston component after attachment of the inner piston component to the offset portion of the crankshaft.

[Fig. 6] Fig. 6 includes diagrams explaining the method of attaching the piston to the offset portion in the rotary compressor according to Embodiment of the invention, the diagrams illustrating a state in which the outer piston component is attached to the inner piston component after the attachment of the inner piston component to the offset portion of the crankshaft.

[Fig. 7] Fig. 7 includes diagrams illustrating details in the vicinity of an offset portion of a related-art rotary compressor.

[Description of Embodiments]

[0013] Embodiment
Fig. 1 is a longitudinal sectional view illustrating a rotary compressor according to Embodiment of the present invention. Fig. 2 is a cross-sectional view illustrating a compression mechanism of this rotary compressor. Fig. 3 includes diagrams explaining an inner piston component of the rotary compressor, (a) being a longitudinal sectional view illustrating a crankshaft and the inner piston component, (b) being a plan view of the inner piston component.

The configuration of the rotary compressor according to Embodiment will be described below with reference to Figs. 1 to 3.

[0014]
A rotary compressor 100 includes a sealed container 1, a motor 2 composed of a stator 2a and a rotor 2b, and a compression mechanism 3 driven by the motor 2 such that the motor 2 and the compression mechanism 3 are accommodated in the sealed container 1. Torque of the motor 2 is transmitted through a crankshaft 4 to the compression mechanism 3. Furthermore, lubricating oil (refrigerating machine oil) for lubricating the compression mechanism 3 is stored in the sealed container 1.

[0015]
The crankshaft 4 includes a main shaft 4a fixed to the rotor 2b of the motor 2, a sub-shaft 4b disposed on the opposite side of the crankshaft 4 from the main shaft 4a, and an offset portion 4c disposed between the main shaft 4a and the sub-shaft 4b.

[0016]
In Embodiment, the crankshaft 4 is formed as follows. To increase a displacement of the rotary compressor 100 in Embodiment, the amount of offset (the amount of offset from the main shaft 4a and the sub-shaft 4b) of the offset portion 4c is increased while an increase in outside diameter of the offset portion 4c is suppressed. Accordingly, the crankshaft 4 is shaped such that an outer circumferential surface of the offset portion 4c on a counter-offset side (i.e., the outer circumferential surface thereof facing away from an offset direction of the offset portion 4c) is recessed away from an outer circumferential surface of each of the main shaft 4a and the sub-shaft 4b. In other words, a distance between an axis common to the main shaft 4a and the sub-shaft 4b and the counter-offset side outer circumferential surface of the offset portion 4c is expressed by Re-e, where Re denotes the radius of the offset portion 4c and e denotes the amount of offset of the offset portion 4c (or a distance between the axis common to the main shaft 4a and the sub-shaft 4b and the axis of the offset portion 4c). Accordingly, the crankshaft 4 of the rotary compressor 100 is formed such that Re-e < Rm and Re-e < Ra, where Rm denotes the radius of the main shaft 4a and Ra denotes the radius of the sub-shaft 4b.

[0017]
The crankshaft 4 formed as described above is journaled in a main bearing 5 and a sub-bearing 6. Specifically, the main bearing 5 is disposed on an upper surface of the compression mechanism 3 and is configured to journal the main shaft 4a of the crankshaft 4. The sub-bearing 6 is disposed on a lower surface of the compression mechanism 3 and is configured to journal the sub-shaft 4b of the crankshaft 4.

[0018]
The compression mechanism 3 includes a cylinder 7, a piston 20, and a vane 9.

[0019]
The cylinder 7 is fixed to an inner portion of the sealed container 1 and includes a cylindrical cylinder chamber in its central part. The cylinder chamber is provided with the piston 20 which slidably engages the offset portion 4c of the crankshaft 4. Both ends of the cylinder chamber of the cylinder 7 in its axial direction are closed by the main bearing 5 and the sub-bearing 6. The cylinder 7 is further provided with the vane 9 which reciprocates in response to rotation of the offset portion 4c. Specifically, an outer circumferential surface of the piston 20, an inner circumferential surface of the cylinder chamber, and the vane 9 define a space that serves as a compression chamber. Furthermore, the vane 9 separates the compression chamber (cylinder chamber) into a high-pressure side space and a low-pressure side space.

[0020]
In Embodiment, the piston 20 is configured as illustrated in Figs. 2 and 3. The piston 20 includes an inner piston component 21 slidably disposed on the outer circumferential surface of the offset portion 4c and an outer piston component 22 slidably disposed on an outer circumferential surface of the inner piston component 21. The inner piston component 21 is composed of a plurality of arc-shaped members 21a, formed by splitting the inner piston component 21 at a plane along the central axis of the offset portion 4c. In Embodiment, the two arc-shaped members 21a constitute the inner piston component 21.

[0021]
In the rotary compressor 100 configured as described above, the rotation of the rotor 2b allows the crankshaft 4 fitted in the rotor 2b to rotate. Consequently, the piston 20 slidably attached to the offset portion 4c of the crankshaft 4 is eccentrically rotated in the cylinder chamber of the cylinder 7. The capacity of the high-pressure side space in the cylinder 7 gradually decreases with the eccentric rotation of the piston 20, thus compressing a refrigerant gas in the high-pressure side space. The compressed refrigerant gas is discharged into the sealed container 1 and is then sent out of the sealed container 1 through a discharge pipe 11 to an external section. An accumulator 12 is disposed next to the sealed container 1. The accumulator 12 communicates with the cylinder chamber of the cylinder 7 through a suction connecting pipe 10. In other words, the refrigerant gas is supplied through the accumulator 12 and the suction connecting pipe 10 into the cylinder chamber of the cylinder 7.

[0022]
A method of attaching the piston 20 to the offset portion 4c of the crankshaft 4 will be described below with reference to Figs. 4 to 6.

[0023]
Fig. 4 is a diagram explaining the method of attaching the piston to the offset portion in the rotary compressor according to Embodiment of the invention, Fig. 4 being a perspective view illustrating a state before assembly of the inner piston component around the offset portion of the crankshaft. Fig. 5 is a diagram explaining the method of attaching the piston to the offset portion in the rotary compressor, Fig. 5 being a perspective view illustrating a state before the outer piston component is attached to the inner piston component after attachment of the inner piston component to the offset portion of the crankshaft. Fig. 6 includes diagrams explaining the method of attaching the piston to the offset portion in the rotary compressor and illustrates a state in which the outer piston component is attached to the inner piston component after the attachment of the inner piston component to the offset portion of the crankshaft. More specifically, Fig. 6(a) is a longitudinal sectional view illustrating a state in which the outer piston component is attached to the inner piston component. Fig. 6(b) is a perspective view illustrating the state in which the outer piston component is attached to the inner piston component. Fig. 6(c) is a plan view illustrating the state in which the outer piston component is attached to the inner piston component. In Fig. 6(c), the crankshaft is not illustrated.

[0024]
In attachment of the piston 20 to the offset portion 4c of the crankshaft 4, the inner piston component 21 is first attached to the offset portion 4c as illustrated in Fig. 4. Specifically, the two arc-shaped members 21a (i.e., the inner piston component 21) are attached to the offset portion 4c such that the offset portion 4c is sandwiched by the two arc-shaped members 21a constituting the inner piston component 21. In other words, the two arc-shaped members 21a constituting the inner piston component 21 are attached to the offset portion 4c in a direction perpendicular to the central axis of the offset portion 4c.

[0025]
As described above, the inner piston component in the related-art rotary compressor is in one piece. In the related-art rotary compressor, therefore, the counter-offset side outer circumferential surface of the offset portion has to protrude away from the outer circumferential surface of the main shaft or the sub-shaft in order to attach the inner piston component to the offset portion of the crankshaft. Alternatively, the counter-offset side outer circumferential surface of the offset portion has to be flush with the outer circumferential surface of the main shaft or the sub-shaft. In other words, in the related-art rotary compressor, the inner piston component cannot be attached to the crankshaft 4 having the above-described shape in Embodiment (i.e., the crankshaft shaped such that the counter-offset side outer circumferential surface of the offset portion 4c is recessed away from the outer circumferential surface of each of the main shaft 4a and the sub-shaft 4b). According to Embodiment, however, since the inner piston component 21 is composed of the two arc-shaped members 21a, the inner piston component 21 can be attached to the crankshaft 4 which is shaped such that the counter-offset side outer circumferential surface of the offset portion 4c is recessed away from the outer circumferential surface of each of the main shaft 4a and the sub-shaft 4b.

[0026]
After the inner piston component 21 is attached to the offset portion 4c of the crankshaft 4 as illustrated in Fig. 4, the outer piston component 22 is attached to the outer circumferential surface of the inner piston component 21 as illustrated in Figs. 5 and 6. Specifically, the main shaft 4a or the sub-shaft 4b is inserted through the outer piston component 22 which is a substantially cylindrical one-piece member. After that, the outer piston component 22 is attached to the outer circumferential surface of the inner piston component 21.

[0027]
In Embodiment, Rp denote the radius of the inner piston component 21. As illustrated in Fig. 3, Rp-e is larger than the radius Rm of the main shaft 4a. Accordingly, the counter-offset side outer circumferential surface of the inner piston component 21 protrudes away from the outer circumferential surface of the main shaft 4a, provided that the inner piston component 21 is attached to the offset portion 4c. Consequently, the outer piston component 22 can be attached around the offset portion 4c from the main shaft 4a side. Furthermore, in Embodiment, as illustrated in Fig. 3, Rp denotes the radius of the inner piston component 21 and Rp-e is larger than the radius Ra of the sub-shaft 4b. Accordingly, the counter-offset side outer circumferential surface of the inner piston component 21 protrudes away from the outer circumferential surface of the sub-shaft 4b, provided that the inner piston component 21 is attached to the offset portion 4c. Consequently, the outer piston component 22 can be attached around the offset portion 4c from the sub-shaft 4b side.

[0028]
The rotary compressor 100 configured as described above in Embodiment provides the following advantages. As described above, the related-art rotary compressor includes the inner piston component formed in one piece. Accordingly, in the related-art rotary compressor, the counter-offset side outer circumferential surface of the offset portion has to protrude away from the outer circumferential surface of the main shaft or the sub-shaft in order to attach the inner piston component to the offset portion of the crankshaft. Alternatively, the counter-offset side outer circumferential surface of the offset portion has to be flush with the outer circumferential surface of the main shaft or the sub-shaft. Disadvantageous^, this configuration of the related-art rotary compressor limits the increase of the displacement. On the other hand, the rotary compressor according to Embodiment has no such limitation. The inner piston component 21 can be attached to the crankshaft 4 which is shaped such that the counter-offset side outer circumferential surface of the offset portion 4c is recessed away from the outer circumferential surface of each of the main shaft 4a and the sub-shaft 4b. Accordingly, the rotary compressor according to Embodiment allows the displacement to be increased (or can achieve high power) without being bound by the above-described limitation.

[0029]
As regards a method of increasing the displacement of the rotary compressor, the height of each of the piston and the cylinder may be increased while the amount of offset of each of the offset portion and the piston is maintained. The contact between the counter-offset side outer circumferential surface of the piston (or the outer circumferential surface of the offset portion facing in the offset direction) and the inner circumferential surface of the cylinder chamber serves as a sealing part that separates the cylinder chamber into the low-pressure side space and the high-pressure side space. Accordingly, increasing the height of each of the piston and the cylinder results in an increase in length of the sealing part. If the height of each of the piston and the cylinder is increased in order to enhance the capacity of the rotary compressor, therefore, the refrigerant gas may leak from the high-pressure side space to the low-pressure side space, thus reducing the weight flow rate of the refrigerant gas sucked into the compression chamber (cylinder chamber). Unfortunately, this leads to a significant reduction in efficiency of the rotary compressor. On the other hand, in the rotary compressor 100 according to Embodiment, the displacement can be increased without an increase in height of each of the piston 20 and the cylinder 7 as described above. In other words, in the rotary compressor 100 according to Embodiment, the displacement can be increased without a significant reduction in efficiency caused by refrigerant leakage in the sealing part between the piston 20 and the inner circumferential surface of the cylinder chamber.

[0030]
Specifically, it is important that the piston 20 and the cylinder 7 be allowed to have a low height and the amount of refrigerant gas leaking from the high-pressure side space to the low-pressure side space in the sealing part defined between the piston 20 and the cylinder 7 be reduced for enhancement of the efficiency of the rotary compressor without any change in displacement. To allow the piston and the cylinder to have a low height without changing the displacement, the amount of offset of the offset portion of the crankshaft has to be increased. In the related-art rotary compressor, however, the amount of offset of the offset portion cannot be increased much because of the above-described limitation. Accordingly, the extent of improvement of the efficiency of the related-art rotary compressor is small. On the other hand, since the rotary compressor 100 according to Embodiment is not bound by the above-described limitation, the amount of offset of the offset portion 4c can be larger than that in the related art. Advantageously, the rotary compressor 100 according to Embodiment can exhibit more improved efficiency than the related-art rotary compressor.

[0031]
Furthermore, it is important that the radius of the offset portion (i.e., the diameter thereof) be reduced in order to reduce the sliding speed of the inner circumferential surface of the piston on the outer circumferential surface of the offset portion for improvement of the efficiency of the rotary compressor without any change in displacement. In the related-art rotary compressor, however, if the amount of offset of the offset portion is increased, the radius of the offset portion cannot be reduced much because of the above-described limitation. The reason is that the reduction in radius of the offset portion causes the counter-offset side outer circumferential surface of the offset portion to be recessed away from the outer circumferential surface of the main shaft or the sub-shaft. Accordingly, the extent of improvement of the efficiency of the related-art rotary compressor achieved by reducing the radius of the offset portion is small. On the other hand, since the rotary compressor 100 according to Embodiment is not bound by the above-described limitation, the radius of the offset portion 4c can be less than that in the related-art rotary compressor even under the condition that the amount of offset of the offset portion 4c is substantially equal to that in the related-art rotary compressor. Advantageously, the rotary compressor 100 according to Embodiment can exhibit further more improved efficiency than the related-art rotary compressor.

[0032]
Although Embodiment has been described with respect to the case where the inner piston component 21 is composed of the two arc-shaped members 21a, the inner piston component 21 may be composed of at least three arc-shaped members 21a. Since increasing the number of arc-shaped members 21a constituting the inner piston component 21 results in a reduction in size of material used for manufacturing the inner piston component 21, the yields of materials are increased, thus improving .iced efficiency >n transport of raw materials. In other words, advantageously, a rotary compressor 100 of low production cost and yet high efficiency can be provided by increasing the number of art-shaped members 21a constituting the inner piston component 21.

[0033]
Furthermore, although Embodiment has been described with respect to the case where the rotary compressor 100 includes the single compression mechanism 3, the rotary compressor 100 may be configured as a multi-cylinder rotary compressor including a plurality of compression mechanisms 3. In this case, a plurality of offset portions 4c is arranged between the main shaft 4a and the sub-shaft 4b such that the offset portions 4c are connected by an intermediate shaft. Furthermore, a plurality of cylinders 7 is arranged so as to correspond to the offset portions 4c. Each end surface of corresponding cylinder chamber opening between the cylinders 7 is closed by a partition plate disposed between the cylinders 7. In the rotary compressor 100 configured as a multiple-cylinder rotary compressor, preferably, the offset portions 4c are arranged so as to be symmetrica] about the axis common to the main shaft 4a and the sub-shaft 4b. For example, if the rotary compressor 100 is configured as a two-cylinder rotary compressor, two offset portions 4c are preferably arranged about the axis common to the main shaft 4a and the sub-shaft 4b such that the offset portions 4c are 180 degrees out of phase relative to each other. This arrangement of the offset portions 4c can suppress, for example, vibrations caused by rotation of the crankshaft 4.

[0034]
Although the relationship between a "clearance between the outer circumferential surface of the offset portion 4c and the inner circumferential surface of the inner piston component 21" and a "clearance between the outer circumferential surface of the inner piston component 21 and the inner circumferential surface of the outer piston component 22" has not particularly been mentioned in Embodiment, for example, the clearances may be allowed to have substantially the same dimension (hereinafter, the expression " substantially the same", or "practically the same or equal" will mean "the same or equal": the expression "the same or equal" in Embodiment does not mean "exactly the same or equal"). For example, in cases where the "clearance between the outer circumferential surface of the offset portion 4c and the inner circumferential surface of the inner piston component 21" and the "clearance between the outer circumferential surface of the inner piston component 21 and the inner circumferential surface of the outer piston component 22" are significantly different in dimension from each other, the difference between "friction between the outer circumferential surface of the offset portion 4c and the inner
circumferential surface of the inner piston component 21" and "friction between the outer circumferential surface of the inner piston component 21 and the inner circumferential surface of the outer piston component 22" is increased. Accordingly, the inner piston component 21 may be significantly different in rotation speed from the outer piston component 22, thus increasing the sliding speed of the inner circumferential surface of the outer piston component 22 on the outer circumferential surface of the inner piston component 21. This may cause abnormal wear in this part. However, since the "clearance between the outer circumferential surface of the offset portion 4c and the inner circumferential surface of the inner piston component 21" and the "clearance between the outer circumferential surface of the inner piston component 21 and the inner circumferential surface of the outer piston component 22" are set to the same dimension, the sliding speed of the inner circumferential surface of the outer piston component 22 on the outer circumferential surface of the inner piston component 21 can be appropriately maintained. Thus, abnormal wear in this part can be prevented.

[0035]
In the rotary compressor 100 according to Embodiment, since the inner piston component 21 is composed of divided members and the outer piston component 22 is a single-piece member, these components may be formed of different materials. In such a case, it is preferable to select the materials such that the material for the inner piston component 21 and that for the outer piston component 22 have the same coefficient of linear expansion. During operation of the rotary compressor 100, the inner piston component 21 and the outer piston component 22 thermally expand. At this time, if these components are significantly different in coefficient of linear expansion from each other, the difference between a "clearance between the inner piston component 21 and each of the main bearing 5 and the sub-bearing 6" and a "clearance between the outer piston component 22 and each of the main bearing 5 and the sub-bearing 6" is increased. Consequently, the difference between "friction between the inner piston component 21 and each of the main bearing 5 and the sub-bearing 6" and "friction between the outer piston component 22 and each of the main bearing 5 and the sub-bearing 6" is increased. Accordingly, the inner piston component 21 may be significantly different in rotation speed from the outer piston component 22, thus increasing the sliding speed of the inner circumferential surface of the outer piston component 22 on the outer circumferential surface of the inner piston component 21. This may cause abnormal wear in this part. However, since the materials for the inner piston component 21 and the outer piston component 22 are selected such that the materials for these components have the same coefficient of linear expansion, the "clearance between the inner piston component 21 and each of the main bearing 5 and the sub-bearing 6" and the "clearance between the outer piston component 22 and each of the main bearing 5 and the sub-bearing 6" can be allowed to have the same dimension. Accordingly, the sliding speed of the inner circumferential surface of the outer piston component 22 on the outer circumferential surface of the inner piston component 21 can be maintained appropriately. Thus, abnormal wear in this part can be prevented. [Reference Signs List]

[0036]
1, sealed container; 2, motor; 2a, stator; 2b, rotor; 3, compression mechanism; 4, crankshaft; 4a, main shaft; 4b, sub-shaft; 4c, offset portion; 5, main bearing; 6, sub-bearing; 7, cylinder; 9, vane; 10, suction connecting pipe; 11, discharge pipe; 12, accumulator; 20, piston; 21, inner piston component; 21a, arc-shaped member; 22, outer piston component; 50, inner piston component (related art); and 100, rotary compressor.

[Name of Document]

CLAIMS

[Claim 1]

A rotary compressor comprising:

a motor including a stator and a rotor;

a crankshaft including a main shaft fixed to the rotor, a sub-shaft disposed on an opposite side of the crankshaft from the main shaft in an axial direction of the crankshaft, and at least one offset portion disposed between the main shaft and the sub-shaft, the crankshaft being driven by the motor;

at least one compression mechanism including a piston slidably attached to the offset portion, a cylinder including a cylindrical cylinder chamber in which the offset portion and the piston are arranged, and a vane separating the cylinder chamber into a low-pressure side space and a high-pressure side space; and

a sealed container configured to accommodate the motor, the crankshaft, and the compression mechanism,

wherein the piston includes an inner piston component slidably disposed on an outer circumferential surface of the offset portion and an outer piston component disposed on an outer circumferential surface of the inner piston component, and wherein the inner piston component includes a plurality of arc-shaped members.

[Claim 2]
The rotary compressor of claim 1, wherein the inner piston component includes at least three arc-shaped members.

[Claim 3]
The rotary compressor of claim 1 or 2, wherein the rotary compressor is configured such that Re-e < Rm < Rp-e, where Rm denotes the radius of the main shaft, Re denotes the radius of the offset portion, Rp denotes the radius of the inner piston component, and e denotes the amount of offset of the offset portion.

[Claim 4]
The rotary compressor of any one of claims 1 to 3, wherein the rotary compressor is configured such that Re-e < Ra < Rp-e, where Ra denotes the radius of the sub-shaft, Re denotes the radius of the offset portion, Rp denotes the radius of the inner piston component, and e denotes the amount of offset of the offset portion.

[Claim 5]
The rotary compressor of any one of claims 1 to 4, wherein the at least one offset portion of the crankshaft comprises a plurality of offset portions, and wherein the at least one compression mechanism comprises a plurality of compression mechanisms.

[Claim 6]
The rotary compressor of any one of claims 1 to 5, wherein a clearance defined between the outer circumferential surface of the offset portion and an inner circumferential surface of the inner piston component is equal to a clearance defined between the outer circumferential surface of the inner piston component and an inner circumferential surface of the outer piston component.

[Claim 7]
The rotary compressor of any one of claims 1 to 6, wherein the outer piston component has a coefficient of linear expansion equal to that of the inner piston component.