CN106567817A - Enclosed compressor and apparatus with the same - Google Patents

Abstract

The present invention provides a hermetic compressor capable of uniformly supplying lubricating oil to the inner peripheral surface of a cylinder and the outer peripheral surface of a piston and improving the retention force of the supplied lubricating oil, and a device including the hermetic compressor. The hermetic compressor has a piston reciprocating axially on the top dead center side and the bottom dead center side, and the piston has a groove surrounding a hole in which a piston pin is provided, wherein the groove has a groove located on the top dead center side of the hole and extending along the circumference. The boundary on the top dead center side, the bottom dead center side boundary located on the bottom dead center side of the hole and arranged in the circumferential direction, the first end side connecting the one end side of the top dead center side boundary and the one end side of the bottom dead center side boundary. The connecting boundary and the second connecting boundary connecting the other end side of the boundary on the top dead center side and the other end side of the boundary on the bottom dead center side, the axial length of the first connecting boundary or the second connecting boundary is equal to or greater than the axial length of the hole , the first connection boundary or the second connection boundary has a linear portion substantially parallel to the axial direction.

Description

Hermetic compressor and equipment including the hermetic compressor

technical field

The present invention relates to a hermetic compressor and a device including the hermetic compressor.

Background technique

In small-capacity hermetic compressors used in household refrigerators, there is a growing demand for energy-saving refrigerators, and low-speed operation of compressors controlled by inverters has been achieved. Therefore, further efficiency improvement and reliability improvement of a sliding part at the time of low-speed operation of the hermetic-type compressor for refrigerators are demanded.

It is described in Patent Document 1 that at least in the vicinity of the bottom dead center and in the portion communicating with the space in the closed container, the shape of the groove after planar development is a shape that does not form a parallel line with the piston axis (claim 1, FIG. 3).

prior art literature

Patent Document 1: Japanese Patent Laid-Open No. 2006-169998

In Patent Document 1, the shape of the grooves formed on the upper and lower sides of the outer circumference of the piston is a roughly half-moon shape protruding toward the skirt side of the piston, and the curvature ratio of the portion protruding toward the skirt side is equal to The curvature of the arc connecting the top side of the piston is small, so that sufficient lubricating oil cannot be supplied to the sliding surface of the skirt side of the piston, and the lubricity of the sliding part between the piston and the cylinder may decrease.

Contents of the invention

Therefore, it is an object of the present invention to provide a hermetic compressor and a device including the hermetic compressor: by uniformly supplying lubricating oil to the inner peripheral surface of the cylinder and the outer peripheral surface of the piston, and increasing the amount of lubricating oil supplied. The retention force, thus improving the compression efficiency and reliability.

The present invention, made in view of the above circumstances, is a hermetic compressor including a piston that reciprocates axially on the top dead center side and the bottom dead center side, and the piston has a piston that surrounds a hole in which a piston pin is provided. The groove, the hermetic compressor is characterized in that the groove has: a boundary on the top dead center side, which is located on the top dead center side of the hole, and is provided along the circumferential direction; The bottom dead center side is provided along the circumferential direction; the first connection boundary connects one end side of the boundary on the top dead center side and one end side of the boundary on the bottom dead center side; and a second connection boundary connects the above top dead center The other end side of the side boundary and the other end side of the bottom dead center side boundary, the axial length of the first connection boundary and/or the second connection boundary is greater than the axial length of the hole, the first connection boundary and /Or the said 2nd connection boundary has the linear part substantially parallel to an axial direction.

The effects of the invention are as follows.

According to the present invention, it is possible to provide a hermetic compressor and a device including the hermetic compressor in which lubricating oil is uniformly supplied to the inner peripheral surface of the cylinder and the outer peripheral surface of the piston and the retention force of the supplied lubricating oil is improved. , thus improving the compression efficiency and reliability.

Description of drawings

FIG. 1 is a longitudinal sectional view of a hermetic compressor according to Embodiment 1. FIG.

Fig. 2 is a cross-sectional view along line A-A of Fig. 1 .

FIG. 3( a ) is a plan view of the piston according to Embodiment 1, and FIG. 3( b ) is a side view of the piston.

4 is a plan development view of an upper (lower) groove in Embodiment 1. FIG.

Fig. 5 is a cross-sectional view taken along line B-B of Fig. 3(b) as viewed in the axial direction.

FIG. 6 is a perspective view of a piston according to Embodiment 1. FIG.

Fig. 7 is an enlarged sectional view of main parts when the piston is at the bottom dead center.

Fig. 8 is a sectional view of the refrigerator.

In the picture:

1—closed container, 2—electric unit, 2a—stator, 2b—rotor, 3—compression unit, 4—lubricating oil, 5—cylinder, 5a—cylinder, 5b—frame, 5c—bearing, 6— Connecting rod, 7—piston, 8—crank shaft, 8a—main shaft, 8b—eccentric shaft, 8c—oil pump, 8ba—oil supply tank, 8bb—lubricating oil injection hole, 8c—oil pump, 8d—spiral groove, 9—piston Pin, 10—balance weight, 11—oil receiving part, 12—cutout portion, 12a—arc end face of cutout, 20—outer peripheral surface, 21—annular groove, 22a—upper groove, 22b—lower groove, 90—hole , 221a (221b)—top dead center boundary, 222a (222b)—first connection boundary, 223a (223b)—bottom dead center side boundary, 224a (224b)—second connection boundary, 225a (225b )—first connection boundary Connecting portion, 226a (226b)—the second connecting portion, 227a (227b)—the third connecting portion, 228a (228b)—the fourth connecting portion, 23—the groove with steps, 24—the lateral side, 25—the top side, 26—skirt side, 27—top surface, 28—skirt surface, 29—joint portion, 30—cylinder central axis, 31a (31b)—angle, 100—hermetic compressor, 200—refrigerator.

detailed description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same symbols are assigned to the same constituent elements, and the same descriptions are not repeated. In addition, this invention is not limited to these embodiment, Various modification examples are included.

(Embodiment 1)

[Overall structure of the hermetic compressor 100]

FIG. 1 is a vertical cross-sectional view of a hermetic compressor 100, and FIG. 2 is a cross-section taken along line A-A of FIG. 1 .

The hermetic compressor 100 accommodates an electric unit 2 and a compression unit 3 including a stator 2 a and a rotor 2 b in a hermetic container 1 . The compression unit 3 is a reciprocating type in which the piston 7 reciprocates in the cylinder 5a of the cylinder 5 integrally formed with the bearing part 5c and the frame part 5b, wherein the piston 7 is connected to the eccentric shaft of the crankshaft 8 through the connecting rod 6 8b link. The crankshaft 8 is fixed to the rotor 2 b of the electric unit 2 at a lower portion of a main shaft 8 a rotatably fitted to a bearing portion 5 c of the cylinder block 5 . The compression unit 3 is elastically supported on the bottom of the closed container 1 by coil springs via the stator 2a of the electric unit 2 fixed to the lower portion of the frame portion 5b.

When the rotor 2b of the electric unit 2 rotates, the crankshaft 8 rotates, and the eccentric shaft 8b rotates eccentrically, and the piston 7 reciprocates in the cylinder bore of the cylinder 5a via the connecting rod 6 connected to the eccentric shaft 8b. The reciprocating direction of the piston 7 is substantially parallel to the axial direction of the piston 7 .

In addition, the lubricating oil 4 stored in the bottom of the closed container 1 is lifted up by the viscous pump action of the oil pump 8 c attached to the lower end of the crankshaft 8 by the rotation of the crankshaft 8 . Furthermore, it is guided upward through the spiral groove 8d formed on the outer periphery of the main shaft 8a, and is fixedly fitted to the connecting rod 6 from the large end bearing part through the small end bearing part of the connecting rod 6 rotatably fitted on the eccentric shaft 8b. The lubrication of the piston pin 9 of the piston 7 is sprayed from the lubricating oil injection hole 8bb provided in the shape of a part penetrating the balance weight 10 installed on the upper end of the eccentric shaft 8b, and finally sprayed from the upper end of the eccentric shaft 8b to the surroundings. The injected lubricating oil 4 hits the oil receiving portion 11 , flows along the notch portion 12 , and is supplied to the outer peripheral surface 20 of the piston 7 .

[piston 7]

FIG. 3( a ) is a plan view of the piston 7 , FIG. 3( b ) is a side view of the piston 7 , and FIG. 4 is a plan view of the groove 22 .

In the piston 7, and on the outer peripheral surface 20 forming the side circumference of the piston 7, two annular grooves 21, grooves 22 (22a, 22b), a stepped groove 23, a lateral side 24, a top side 25, and a skirt are provided. side 26. Further, the piston 7 has a top surface 27 facing the piston 7 in the cylinder bore, and a skirt surface 28 facing the crankshaft 8 side.

<Annular groove 21>

The annular groove 21 is a groove provided over the circumference of the outer peripheral surface 20 and is provided on the top side surface 25 side of the piston 7 . In this embodiment, two annular grooves 21 are provided, but one or three or more may be provided.

＜Slot 22＞

As the grooves 22, there are an upper surface groove 22a provided on the upper surface of the piston 7, and a lower surface groove 22b provided on the lower surface. The shapes of the upper groove 22a and the lower groove 22b can be the same as each other, so the description as the lower groove 22b will not be repeated. The upper surface groove 22 a and the lower surface groove 22 b are separated from each other in the circumferential direction via the lateral surface 24 .

In the case of looking down on the piston 7, the upper groove 22a is an area surrounded by boundaries (top dead center side boundary 221a, bottom dead center side boundary 223a, first connecting boundary 222a, and second connecting boundary 224a), and is located at The concave portion of the outer peripheral surface 20 . In the respective areas of the upper groove 22a and the lower groove 22b, a hole 90 radially penetrating the side surface of the piston 7 is provided, and a cylindrical, for example cylindrical, piston pin 9 is fitted and fixed in the hole 90 .

The top dead center side boundary 221 a is located closest to the top surface 27 in the upper surface groove 22 a and is located closer to the skirt surface 28 than the annular groove 21 . The top dead center side boundary 221 a is provided along the circumferential direction of the piston 7 and is substantially linear when the outer peripheral surface 20 is planarly developed. This length is a length equal to or greater than the circumferential dimension when the dimension of the hole 90 provided with the piston pin 9 is projected on the outer peripheral surface 20 developed in a plane.

The bottom dead center side boundary 223a is located on the skirt surface 28 side most in the upper groove 22a. The bottom dead center side boundary 223a is provided along the circumferential direction of the piston 7, and is substantially linear when the outer peripheral surface 20 is planarly developed. This length is a length equal to or greater than the circumferential dimension when the dimension of the hole 90 is projected on the outer peripheral surface 20 developed in a plane. In addition, the lengths of the top dead center side boundary 221 a and the bottom dead center side boundary 223 a can be substantially the same in planar development.

The first connection boundary 222a exists to connect one end of the top dead center side boundary 221a and one end of the bottom dead center side boundary 223a. The first connection boundary 222a has a straight line portion 222a1 parallel to the reciprocating direction of the piston 7 . The length of the straight line portion 222a1 may be the entire length of the first connection boundary 222a, or may be a partial length as in the present embodiment. When the length of a part of the first connection boundary 222a includes the midpoint of the axial dimension of the first connection boundary 222a, it is easy to hold the lubricating oil 4 in the upper groove 22a, which is preferable. In addition, in the case of a length that is a part of the first connection boundary 222a, the first connection boundary 222a may have a shape that protrudes in a direction away from the second connection boundary 224a.

The second connection boundary 224a exists so as to connect the other end of the top dead center side boundary 221a and the other end of the bottom dead center side boundary 223a. The second connection boundary 224a has a straight line portion 224a1 parallel to the reciprocating direction of the piston 7, similarly to the first connection boundary 222a. The length of the straight line portion 224a1 may be the entire length of the second connection boundary 224a, or may be a partial length as in the present embodiment. When the length of a part of the second connection boundary 224a includes the midpoint of the axial dimension of the second connection boundary 224a, it is easy to hold the lubricating oil 4 in the upper groove 22a, which is preferable. In addition, in the case of a length that is a part of the second connection boundary 224a, the second connection boundary 224a may have a shape that protrudes in a direction away from the first connection boundary 222a. In addition, the lengths of the first connection boundary 222a and the second connection boundary 224a can be substantially the same as each other.

The top dead center side boundary 221a, the first connecting boundary 222a, the bottom dead center side boundary 223a, and the second connecting boundary 224a pass through the rounded connecting portion 29 (the first connecting portion 225a to the fourth connecting portion 225a) having a predetermined curvature. 228a) Connect.

The first connecting portion 225a is a portion connecting one end of the top dead center side boundary 221a and one end of the first connecting boundary 222a, and is provided at a position where the piston 7 can be recognized in plan view and side view.

The second connecting portion 226a is a portion connecting one end of the bottom dead center side boundary 223a and the other end of the first connecting boundary 222a, and is provided at a position where the piston 7 can be recognized in plan view and side view.

The third connection portion 227a is a portion connecting the other end of the bottom dead center side boundary 223a and the other end of the second connection boundary 224a, and is provided at a position where the piston 7 can be recognized in plan view and side view.

The fourth connection portion 228a is a portion connecting the other end of the top dead center boundary 221a and one end of the second connection boundary 224a, and is provided at a position where the piston 7 can be recognized in plan view and side view.

One or more, preferably all, of the connecting portion 29 have a curvature greater than that of a circle whose diameter is the axial length of the piston pin 9, preferably a circle whose diameter is the distance between the upper dead center boundary 221a and the lower dead center boundary 223a. . The curvature of the connecting portion 29 is larger than that of the top dead center boundary 221a, the first connection boundary 222a, the bottom dead center boundary 223a, and the second connection boundary 224a of the upper surface groove 222a. More preferably, the curvature of the connecting portion 29 is greater than the curvature of a circle whose diameter is the axial distance between the upper dead center boundary 221a and the lower dead center boundary 223a.

The axial positions of the first connection portion 225 a and the fourth connection portion 228 a are located closer to the top surface 27 than the axial position of the end portion of the hole 90 . In addition, the axial positions of the second connecting portion 226 a and the third connecting portion 227 a are located closer to the skirt surface 28 than the axial position of the end portion of the hole 90 .

The upper surface groove 22a of the present embodiment has a substantially rectangular shape when the outer peripheral surface 20 is planarly developed. More specifically, the top dead center boundary 221 a and the bottom dead center boundary 223 a are substantially linear. In addition, all of the first connection boundary 222a and the second connection boundary 224a are substantially linear straight portions 222a1, 224a1, or a part of them are straight portions 222a1, 224a1, and the remaining part can be a curved line protruding toward the outside of the upper surface groove 22a.

＜Top side 25＞

The top surface 25 is disposed between the top surface 27 of the piston 7 and the annular groove 21 . The top side 25 is a sliding surface with the cylinder 5a.

＜Skirt side 26＞

The skirt surface 26 is provided between the skirt surface 28 of the piston 7 and the bottom dead center side boundary 223a. The skirt surface 26 has a structure protruding from the inside of the cylinder 5a when the piston 7 is at the bottom dead center.

＜Lateral side 24＞

The lateral surface 24 is provided between the upper groove 22a provided on the upper surface of the piston 7 and the lower groove 22b provided on the lower surface, and exists in two places in total. The lateral sides 24 fulfill the function of guiding the piston 7 when it enters the cylinder 5a.

＜Trough 23 with steps＞

The stepped groove 23 is provided on the edge of the skirt surface 26 and the skirt surface 28 of the piston 7 and has a smaller diameter than the piston outer diameter provided over the circumference of the outer peripheral surface 20 of the piston 7 . The stepped groove 23 improves the lubricant retention of the skirt side 26 . In addition, in the grinding process of the outer diameter of the piston 7, even if there is no roller processing machine, the stepped groove 23 can be clamped and processed.

[Slot 22 viewed axially]

FIG. 5 is a cross-sectional view taken along the line B-B in FIG. 3( b ), and FIG. 6 is a perspective view of the piston 7 . In the reciprocating direction (axial direction) of the piston 7, the angle formed by the straight line connecting the first connecting boundary 222a and the piston central axis 30 and the straight line connecting the second connecting boundary 224a and the piston central axis 30, and the upper groove 22a The opposing angle 31 a preferably has a lower limit of 120° or more and an upper limit of 150° or less.

[Drive of Piston 7 in Hermetic Compressor 100]

Fig. 7 is an enlarged sectional view of main parts when the piston 7 is at the bottom dead center. Above the piston 7, a notch 12 is provided. The notch portion 12 guides the lubricating oil dropped and transferred to the oil receiving portion 11 out of the lubricating oil 4 ejected from the lubricating oil injection hole 8 bb, and supplies the lubricating oil to the outer peripheral surface 20 of the piston 7 . As shown in FIGS. 2 and 7 , at the bottom dead center, the annular groove 21 and the upper surface groove 22 a are exposed through the notch 12 , so that the lubricating oil 4 that flows along the notch 12 and is supplied to the outer peripheral surface 20 of the piston 7 flows on the piston 7 . When reaching the bottom dead center, it is supplied to the annular groove 21 and the upper surface groove 22a. In addition, in the present embodiment, when the piston 7 is at the bottom dead center, the portion of the annular groove 21 that exists most in the bottom dead center direction is provided on the top dead center side with respect to the end surface 12 a of the cutout portion 12 . As a result, the lubricating oil 4 flowing along the notch portion 12 is effectively stored in the annular groove 21, thereby being able to lubricate between the piston 7 and the cylinder tube 5a.

Furthermore, as described above, the upper surface groove 22 a and the lower surface groove 22 b communicate through the hole 90 . The lubricating oil 4 that flows along the hole 90 and is supplied to the upper surface groove 22a is also supplied to the lower surface groove 22b. The lubricating oil 4 after supply is supplied between the piston 7 and the cylinder 5a by reciprocating motion of the piston 7, and mainly performs lubrication and sealing. Since the upper surface groove 22 a and the lower surface groove 22 b are surrounded by the outer peripheral surface 20 , the lubricating oil 4 can be held without causing the supplied lubricating oil 4 to flow out to the outer peripheral surface 20 side more than necessary.

[Effect]

The piston 7 of this embodiment has the upper surface groove 22a of the above-mentioned structure, and the lower surface groove 22b which can have the same shape as the upper surface groove 22a. Thereby, the upper surface groove 22a can exhibit the following effect.

(1) The first connection boundary 222 a and the second connection boundary 224 a have linear portions 222 a 1 , 224 a 1 substantially parallel to the reciprocating direction (axial direction) of the piston 7 . Moreover, the axial length of the 1st connection boundary 222a and the 2nd connection boundary 224a is more than the axial length of the hole 90. As shown in FIG. Thereby, the lubricating oil 4 supplied to the upper surface groove 22a easily flows to the entire area of the hole 90, and the lubricating oil 4 supplied to the vicinity of the first connection boundary 222a and the second connection boundary 224a spreads substantially uniformly to the first connection boundary. 222a, the second connection boundary 224a. In order to make it diffuse approximately uniformly, the straight parts 222a1 and 224a1 may be provided over the entire lengths of the first connection boundary 222a and the second connection boundary 224a, or the straight parts 222a1 and 224a1 may be provided over a part, and the first connection boundary 222a , The second connection boundary 224a can also protrude, but due to the reciprocating motion of the piston 7, the lubricating oil 4 is easy to flow on the top dead center side boundary 221a of the top dead center side end and the bottom dead center side end of the upper groove 22a. , the vicinity of the bottom dead center side boundary 223a is concentrated, and preferably a part and the rest are also concentrated on the axial center side appropriately so as to form a convex curve. Therefore, the lubricating oil 4 can be spread substantially uniformly in the upper groove 22a, and the lubricating oil 4 can be uniformly supplied to the outer peripheral surface 20 (lateral side 24) across the first connection boundary 222a and the second connection boundary 224a.

(2) The boundary 221a on the side of the top dead center and the boundary 223a on the side of the bottom dead center are substantially parallel to the circumferential direction. Thus, when the lubricating oil 4 is moved by an axial force due to the reciprocating motion of the piston 7 and is supplied near the upper dead center boundary 221a or the lower dead center boundary 223a, the lubricating oil 4 is substantially evenly distributed on the upper dead center side. The boundary 221a and the bottom dead center side boundary 223a spread out. Therefore, the lubricating oil 4 is evenly supplied to the outer peripheral surface 20 across the top dead center side boundary 221 a and the bottom dead center side boundary 223 a.

(3) The axial lengths of the first connection boundary 222a and the second connection boundary 224a are larger than the axial length of the hole 90 , and the top dead center side boundary 221a and the bottom dead center side boundary 223a are substantially parallel to each other. This makes it easy to hold the lubricating oil 4 evenly over the entire circumference of the upper surface groove 22a, and by securing the area of the upper surface groove 22a, the supply amount of the lubricating oil 4 to the piston pin 9 can be increased.

(4) The upper surface groove 22a is a substantially rectangular shape with rounded corners, and the lower limit of the curvature of the connecting portion 29 is as described above. Thereby, it becomes easy to ensure the area of the upper surface groove 22a. In addition, by increasing the curvature beyond the lower limit, the area of the upper surface groove 22a can be ensured, thereby increasing the supply amount of lubricating oil and reducing the frictional loss due to the reduction of the sliding area. On the other hand, by rounding the corners of the upper surface grooves 22a instead of approximately right angles, the lubricating oil 4 after the supply does not stagnate at the corners of the upper surface grooves 22a, and can be evenly held at the boundary of the upper surface grooves 22a. the edge of.

(5) The appropriate range of the angle 31a is as described above. If the angle 31a is made smaller than 120°, it becomes difficult for the lubricating oil 4 held in the upper surface groove 22a to spread over the lateral surface 20 . If the angle 31a is set to 150° or more, the area of the lateral surface 24 becomes small, and the behavior becomes unstable during the reciprocating motion of the piston 7 . The upper limit of the angle 31a can also be determined in consideration of the sum of the angle 31b with the lower surface groove 22b. For example, the sum of the angle 31a and the angle 31b is preferably 300° or less.

In addition, as mentioned above, since each constituent element of the lower surface groove 22b can be the same as each constituent element of the upper surface groove 22a, the lower surface groove 22b can also exhibit the same effect as above. The piston 7 may have only the upper surface groove 22a, may have only the lower surface groove 22b, and may have both of them.

[Equipment equipped with a hermetic compressor]

FIG. 8 is a cross-sectional view of a refrigerator 200 as an example of equipment equipped with the hermetic compressor 100 . Refrigerator 200 has a refrigeration cycle including a hermetic compressor 100 , a condenser (not shown), a decompression unit (not shown), and an evaporator 201 . In the hermetic compressor 100, the refrigerant is compressed to high temperature and high pressure, the refrigerant is released in the condenser, and the pressure of the refrigerant is lowered in the decompression section, and then the refrigerant is evaporated in the evaporator 201, Thereby, cold air can be obtained.

The device equipped with the hermetic compressor 100 is not limited to the refrigerator 200, and can be applied to various devices such as an air conditioner.

Claims (5)

1. a kind of hermetic motor compressor, it possesses the piston for moving back and forth in top dead centre side and lower dead center side vertically,

The piston has the groove that the hole to being provided with piston pin is surrounded,

Above-mentioned hermetic motor compressor is characterised by,

Above-mentioned groove possesses：

Top dead centre lateral boundaries, it is located at stop side more top than above-mentioned hole, and circumferentially arranged；

Lower dead center lateral boundaries, it is located at than above-mentioned hole stop side on the lower, and circumferentially arranged；

First links border, and it links a side of a side of above-mentioned top dead centre lateral boundaries and above-mentioned lower dead center lateral boundaries；With And

Second links border, and it links the other end of the another side of above-mentioned top dead centre lateral boundaries and above-mentioned lower dead center lateral boundaries Side,

It is above-mentioned first link border and/or it is above-mentioned second link border axial length be above-mentioned hole axial length with On,

Above-mentioned first links border and/or above-mentioned second link border has and approximately axially parallel line part.

2. hermetic motor compressor according to claim 1, it is characterised in that

The axial length on above-mentioned first link border and above-mentioned second link border is more than the axial length in above-mentioned hole,

Above-mentioned first links border and above-mentioned second link border has and approximately axially parallel line part,

Above-mentioned first links border to the direction protrusion for linking border away from above-mentioned second,

Above-mentioned second links border to the direction protrusion for linking border away from above-mentioned first.

3. hermetic motor compressor according to claim 1 and 2, it is characterised in that

Above-mentioned groove is generally rectangular, and has：

First connecting portion, one end of its above-mentioned top dead centre lateral boundaries of connection and above-mentioned first links border；

Second connecting portion, the other end of its above-mentioned first connecting portion of connection and one end of above-mentioned lower dead center lateral boundaries；

The other end on the 3rd connecting portion, the other end of its above-mentioned lower dead center lateral boundaries of connection and above-mentioned second link border；And

4th connecting portion, its connection above-mentioned second links the one end on border and the other end of above-mentioned top dead centre lateral boundaries,

The curvature of above-mentioned first connecting portion, above-mentioned second connecting portion, above-mentioned 3rd connecting portion and above-mentioned 4th connecting portion is than upper State the curvature on top dead centre lateral boundaries, above-mentioned first link border, above-mentioned lower dead center lateral boundaries and above-mentioned second link border Greatly,

Above-mentioned top dead centre lateral boundaries and above-mentioned lower dead center lateral boundaries are almost parallel.

4. according to the hermetic motor compressor described in any one of claims 1 to 3, it is characterised in that

In the case where above-mentioned piston is observed vertically, by the straight line of the center of above-mentioned piston and above-mentioned top dead centre lateral boundaries, With formed by the straight line of the center by the above-mentioned piston and above-mentioned lower dead center lateral boundaries and angle opposed with above-mentioned groove be 120 ° with On.

5. a kind of equipment, it is characterised in that

Possesses the hermetic motor compressor described in any one of Claims 1-4.