JP2015081558A - Enclosed compressor and equipment mounted with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the capacity to supply lubricating oil to a sliding part between a piston and a cylinder, by restraining a piston action from making the oil scatter peripherally, by a simple structure.SOLUTION: In an enclosed compressor, a piston is provided with an oil retention part that has a plurality of oil groove exposed from a cylinder in a bottom dead point position of a piston and positioned within the cylinder in a top dead point position of the piston, and the length of the oil retention part in the axial direction of the piston is equal to or shorter than the length of a sliding part belonging to a lower end side with respect to a lower end part of the oil retention part.

Description

  The present invention relates to a hermetic compressor and a device equipped with the same.

  The oil supply structure to the sliding surface that slides between the cylinder and the piston of the hermetic compressor is, for example, as described in Patent Document 1, from the end on the crankshaft side over the entire outer periphery of the piston. The structure which has the step part (non-sliding part) of the depth of 200 micrometers or less extended in the range of 0.2 to 0.4 times the full length of a piston is proposed.

  Further, in Patent Document 2, the space inside the sealed container and a part of the oil supply groove communicate with each other at the bottom dead center of the piston, and all of the oil supply groove is located in the cylindrical hole in other areas such as near the top dead center. An oil supply structure arranged as described above has been proposed.

JP 2006-161761 A Special table 2011-509365 gazette

  In the above-described hermetic compressor of Patent Document 1, a stepped portion (non-sliding portion) is set at the end on the crankshaft side of the outer periphery of the piston, so that the surface of the stepped portion when the piston is at bottom dead center. Lubricating oil is attached to the cylinder, and the lubricating oil adhering to the stepped portion is supplied between the piston and the cylinder during compression (near top dead center).

  Further, in Patent Document 2, at a bottom dead center, a part of the oil supply groove communicates with the space in the sealed container, so that the lubricating oil is scattered from the notch to the upper part of the piston that has come out into the space in the sealed container ( (Paragraphs 0047 and 0066, FIG. 2 etc.).

However, the above oil supply structure has the following problems.
When the compressor operating frequency is higher than the commercial power supply frequency, the oil pump has a high oil supply capacity and a large amount of lubricating oil is injected from the eccentric shaft at the top of the crankshaft toward the cylinder block and the sliding part of the piston outer periphery. Therefore, oil is supplied over the entire outer surface of the piston exposed from the cylinder block, so the amount of oil secured in the stepped portion of the outer periphery of the piston does not pose a problem in terms of compressor performance and reliability. When the machine operating frequency is lower than the commercial power supply frequency, the oil pump's oil supply capacity decreases and the amount of lubricating oil injected from the eccentric shaft above the crankshaft decreases, and the range of lubricating oil injected is reduced. Therefore, the lubricating oil will not be supplied over the entire outer surface of the piston exposed from the cylinder block. Oil amount to be secured in the stepped portion becomes a significant impact on the performance and reliability of the compressor of the low rotational speed.

  The oil supply structure described in Patent Document 1 has a function of supplying the lubricating oil secured in the stepped portion to the sliding portion between the piston and the cylinder, but the piston adheres in the compression and discharge stroke toward the top dead center. Most of the inertial force acting on the oil is scattered around and there is room for improvement in the oil supply efficiency. However, if the length of the stepped portion is increased in order to increase the amount of oil supplied to the sliding portion between the piston and the cylinder, the stepped portion of the piston is attached to the cylinder if the overall length of the piston is constant. Since it does not contact (does not slide), the length of the sliding portion (seal portion) of the piston is shortened (sliding area is reduced), and the surface pressure at the contact portion between the piston and the cylinder increases. Therefore, the oil film formation at the sliding portion between the piston and the cylinder becomes insufficient, the sealing performance decreases, the amount of compressed gas leaked from the compression chamber increases, the performance of the compressor deteriorates, and the sliding between the piston and the cylinder decreases. There is a problem in that the lubricity of the part is also lowered and the reliability of the compressor is likely to be lowered.

  In the oil supply structure described in Patent Document 2, the oil supply groove provided in the piston communicates through a notch provided above the piston at the bottom dead center of the piston, and the remaining part of the oil supply groove is a cylinder. It exists in the block and does not communicate with the space inside the sealed container. According to this structure, even if lubricating oil is supplied through the notch provided above the piston, if there is gas in the oil supply groove, there is no escape of this gas. It is difficult to supply a sufficient amount of lubricating oil, and sufficient lubrication between the piston and the cylinder cannot be performed. Further, since the supplied lubricating oil needs to pass through the notch, the supply amount per cycle of the piston is limited.

  Insufficient lubrication due to sliding between the piston and the cylinder may cause a reduction in compressor performance and wear of the sliding part due to friction loss, etc. The area of non-sliding increases, the surface pressure rises and a strong force is applied, and the performance of the compressor is reduced due to friction loss and the like. For this reason, the structure which can hold | maintain lubricating oil efficiently, supplies oil between a piston and a cylinder, and can suppress the reduction | decrease in a sliding area is calculated | required.

  The present invention has been made in view of the above circumstances, and is a sealed type comprising a cylinder, a compression element having a piston that reciprocates in the cylinder, and an oil supply section that supplies lubricating oil to the compression element. An oil retaining portion that is exposed through the opening of the cylinder at the bottom dead center position of the piston and has a plurality of oil grooves located in the cylinder at the top dead center position of the piston; A hermetic compressor provided in a piston, wherein the length of the oil holding portion in the axial direction of the piston is equal to or less than the length of a sliding portion belonging to the lower end side from the lower end portion of the oil holding portion. is there.

  According to the present invention, an oil holding portion is formed in which a plurality of oil grooves that are opened (exposed) in the space inside the sealed container at the bottom dead center position of the piston are formed, and the length of the oil holding portion in the axial direction of the piston is reduced. The oil holding part has a relatively simple structure that is less than the length of the sliding part belonging to the lower end side of the oil holding part, and prevents the oil from splashing around the piston movement to the sliding part between the piston and cylinder. The lubricating oil supply capacity can be improved. As a result, oil film formation at the sliding part between the piston and the cylinder is ensured, the sealing performance is improved, and the performance of the compressor at the time of low speed operation can be improved particularly in the rotation speed control specification compressor having a large influence of leakage. In addition, a hermetic compressor with improved compressor reliability can be provided.

Hereinafter, the present invention will be described in detail by each embodiment. In addition, this invention is not limited to each following embodiment, A various well-known structure can be employ | adopted in the range which does not affect the thought of invention.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. First, the overall configuration will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of a hermetic compressor according to a first embodiment of the present invention, and FIG. 2 is an AA transverse sectional view of FIG.

  The hermetic compressor 50 according to the present embodiment accommodates an electric element 2 and a compression element 3 including a stator 2a and a rotor 2b in a hermetic container 1, and the compression element 3 is integrally formed with a bearing portion 5c and a frame portion 5b. In the cylinder 5a formed in the cylinder block 5, the piston 7 connected to the eccentric shaft 8b of the crankshaft 8 by a connecting rod (connecting rod) 6 reciprocates. The crankshaft 8 is fixed to the rotor 2b of the electric element 2 at the lower part of the main shaft 8a rotatably fitted to the bearing part 5c of the cylinder block 5, and the compression element 3 is fixed to the lower part of the frame part 5b. Is supported elastically on the bottom of the hermetic container 1 by a coil spring. When the rotor 2b of the electric element 2 rotates, the crankshaft 8 rotates, and the eccentric shaft 8b also rotates eccentrically, and the piston 7 reciprocates in the bore of the cylinder 5a via the connecting rod 6 connected to the eccentric shaft 8b. It is like that.

  The upper end portion of the cylinder 5 a is closed by a cylinder head 10 in which a suction valve and a discharge valve (not shown) are incorporated, and constitutes a compression chamber 12 between the piston 7. In the compression chamber 12, the refrigerant is sucked and compressed by the reciprocating motion of the piston 7 and discharged from the discharge valve.

  As the crankshaft 8 rotates, the lubricating oil 4 stored at the bottom of the sealed container 1 is pulled up by the centrifugal pump action of the oil pump 8c attached to the lower end of the crankshaft 8, and formed on the outer periphery of the main shaft 8a. The ball joint portion connected to the large end bearing portion of the connecting rod 6 and the piston 7 which are guided upward through the spiral groove 8d and further rotatably fitted in the oil supply groove 8ba of the eccentric shaft 8b is performed. The oil is injected from a lubricating oil radiation hole 8bb, which is one of the oil supply portions, provided in a form that partially penetrates the balance weight 9 attached to the upper end of the eccentric shaft 8b, and finally the eccentricity, which is one of the oil supply portions. It is sprayed around from the upper end of the shaft 8b. Lubrication and sealing of the sliding portion between the piston 7 and the cylinder 5a are mainly performed by the injected lubricating oil 4. The configuration of the oil supply unit is not limited to this as long as the lubricating oil can be supplied to the piston 7.

  The refrigerant flowing in through the suction pipe 16 connected in the sealed container 1 passes through the suction valve (not shown) of the cylinder head 10 from the plastic suction silencer 17 and is compressed in the cylinder 5a. The refrigerant that has entered into 12 and has been compressed here passes through a discharge valve (not shown) of the cylinder head 10 and enters a discharge chamber 11 a in the head cover 11, from which discharge is integrally formed with the cylinder block 5. It passes through the silencer 18, passes through the discharge pipe 14, and flows out from the discharge pipe 15 to the external refrigeration cycle.

  Next, the oil supply structure between the piston and the cylinder bore, which is a feature of the present embodiment, will be described in detail with reference to FIGS. 3A is an enlarged cross-sectional view of the main part of the hermetic compressor according to the present embodiment at the piston bottom dead center position, and FIG. 3B is a diagram of the hermetic compressor according to the present embodiment at the piston top dead center position. FIG. 4 is a cross-sectional view ((a) view) and a side view ((b) view) of the piston according to this embodiment, and FIG. 5 is an external front view of the piston according to this embodiment. 6 is an experimental result showing the friction loss reducing effect of the piston according to the present embodiment, and FIG. 7 is an external front view showing another oil holding portion shape of the piston according to the present embodiment.

  3 to 5, the piston sliding length Lp (the range of the piston 7 that slides with the cylinder 5a) on the outer periphery of the piston 7 of the present embodiment has an oil groove that opens (exposes) from the cylinder 5a at the bottom dead center. 3 as the oil retaining portion Lo (in this embodiment, the length from the uppermost end portion to the lowermost end portion of the plurality of annular oil grooves 7c, see FIG. 5). The annular oil groove 7c is recessed, and the oil holding portion represented by the symbol Lo is exposed to the space inside the sealed container 1 at the piston bottom dead center position (FIG. 3A). ing. The oil retaining portion Lo is preferably provided at substantially the center in the axial direction of the piston 7 from the viewpoint of uniformity of surface pressure due to sliding between the piston cylinders. The three annular oil grooves 7c are preferably provided at an equal pitch.

  The oil groove belonging to the oil holding part (in this embodiment, the plurality of annular oil grooves 7c belonging to the oil holding part) supplies the lubricating oil to the oil groove so that there is a gas escape space in the oil groove. It may be exposed from the cylinder 5a in an efficient manner, and includes, for example, an aspect in which substantially all, preferably all, of the oil grooves are exposed in the space inside the sealed container 1. In the present embodiment, the entire annular oil groove 7c is not inside the cylinder 5a at the bottom dead center, and all of the piston upper side, side side, and lower side are exposed in the space inside the sealed container 1 (FIG. 1). Thru 3 etc.). In addition, the shape of the oil groove belonging to the oil holding portion is not limited to the annular oil groove 7c, but is a narrow groove, a thick groove, a plurality of grooves and depressions arranged in a chain line shape in an arbitrary direction on the outer peripheral surface of the piston, and the like. These may or may not extend over the entire circumference of the piston outer peripheral surface in the radial direction, but it is preferable to extend over the entire circumference from the viewpoint of uniform and efficient oil supply. From the viewpoint of uniformity of surface pressure due to sliding between piston cylinders, the oil groove is preferably provided symmetrically with respect to a plane passing through the center of the piston, and in particular, the connecting rod 6 swings in the direction perpendicular to the paper surface in FIG. Therefore, it is preferable to be symmetric with respect to the horizontal plane in FIG. Further, from the viewpoint of uniformly and efficiently distributing the lubricating oil to the entire piston, a narrow groove, a thick groove, a plurality of grooves and depressions arranged in a chain line shape, an annular oil groove, and the like are preferable. Grooves are preferred.

  The outer diameter Dp of the sliding portion of the outer peripheral surface of the piston 7 that slides with the inner peripheral surface of the cylinder 5a is formed to be about 10 μm smaller than the bore inner diameter of the cylinder 5a. The spherical bearing 7e is formed inside the piston 7, and the ball joint portion of the connecting rod 6 engages slidably. An annular oil groove 7b that does not belong to the oil holding part (is located in the cylinder 5a at the bottom dead center and is not exposed to the space inside the sealed container 1) is provided near the center of the piston top side sliding length Lu, and is compressed. It performs the function of oil retention during gas sealing and gas leakage processes. The outer peripheral surface of the piston 7 is subjected to a manganese phosphate treatment, which is an oleophilic surface treatment after grinding and finishing, thereby improving the initial familiarity of the piston sliding portion.

  An annular oil groove 7c formed in the oil retaining portion Lo is a concave groove having a groove width dimension w and a groove depth dimension δ. The annular oil groove 7c is formed by machining or the like when roughing the outer peripheral surface of the piston 7. It is designed to hold lubricating oil. The holding amount of the lubricating oil 4 is determined by the space volume of the annular oil groove 7c. For example, when the groove depth δ is about 100 μm, the groove width dimension is about 0.8 mm. It can be set arbitrarily according to operating conditions such as speed and load.

  From the condition that the oil holding portion Lo is exposed to the space inside the sealed container 1 at the piston bottom dead center position, the top side sliding length Lu of the piston 7 that is the length from the top of the piston 7 to the upper end of the oil holding portion is It is determined by subtracting the piston stroke St, which is the length that the piston top moves from the top dead center to the bottom dead center, from the sliding length Lc (FIG. 3) of 5a. Further, in the axial direction of the piston 7, the length from the lower end of the sliding portion where the piston 7 slides with the cylinder 5a to the lower end of the oil holding portion (the length of the sliding portion on the lower end side from the lower end portion of the oil holding portion) ) Is longer than the oil retaining portion Lo which is the distance between the upper end and the lower end of the oil retaining portion, which is advantageous for reducing piston friction loss. That is, the length of the oil retaining portion Lo is equal to or shorter than the length of the sliding portion Ls belonging to the lower end side from the lower end portion of the oil retaining portion.

  The upper surface of the outer periphery of the cylinder 5a of the present embodiment is provided with an oil reservoir 13 that is one of the oil supply portions that receives the lubricating oil 4 scattered from the eccentric shaft 8b of the crankshaft 8 by the partition wall 13a. Lubricating oil is supplied to the sliding surfaces of the cylinder 5 a and the piston 7 regardless of the rotational position of the crankshaft 8 by tilting the bottom surface of the oil reservoir 13 toward the crankshaft 8 side. The oil supply portion may be any one that can supply lubricating oil between the piston and the cylinder, and may be one or more of the above-described lubricating oil radiation hole 8bb, the upper end portion of the eccentric shaft 8b, and the oil sump portion 13. Any other known method may be used.

  When the piston 7 is located at the bottom dead center, as shown in FIG. 3A, the plurality of annular oil grooves 7c provided in the oil holding portion Lo in the vicinity of the center of the sliding portion of the piston 7 are formed in the cylinder 5a. Is exposed to the inner space of the sealed container 1 through a chamfer 5aa which is an opening provided in two stages by changing the chamfer angle on the end surface on the crankshaft 8 side. The lubricating oil 4 pumped up by the rotation of the crankshaft 8 lubricates each bearing sliding portion of the crankshaft 8, and is then injected from the lubricating oil radiation hole 8bb of the eccentric shaft 8b, and is approximately the same height as the lubricating oil radiation hole 8bb. Is supplied to the outer peripheral surface of the piston exposed from the cylinder block 5 through the chamfer 5aa of the cylinder 5a located in the cylinder 5a, and particularly supplied to the plurality of annular oil grooves 7c of the oil retaining portion Lo to lubricate the inner space of the annular groove. Oil is secured.

  When the piston 7 is located at the top dead center, as shown in FIG. 3B, a plurality of oil holding portions Lo provided near the center of the sliding portion of the piston 7 that has taken in oil at the bottom dead center. The annular oil groove 7c is located on the inner periphery of the bore of the cylinder 5a, and the lubricating oil 4 secured in the annular oil groove 7c flows into the bore of the cylinder 5a.

  In the compression stroke in which the piston 7 moves from the bottom dead center to the top dead center, the seal between the piston and the cylinder is well maintained by the lubricating oil 4 held in the annular oil groove 7c belonging to the oil holding portion Lo of the piston 7. The lubricity of the sliding part between the piston 7 and the cylinder 5a can be improved.

  The effect of the oil supply structure of the present embodiment was confirmed by an element experiment of piston friction force measurement using an actual compressor. In FIG. 6, the test piston (A) has a stepped portion (non-sliding) having a length Ls ′ exposed from the cylinder 5a at the bottom dead center at the end on the crankshaft side (bottom dead center side) of the outer periphery of the piston. Part), the oil retaining part is the only annular oil groove exposed from the cylinder 5a at the bottom dead center, and Lo ≦ Ls. Example 1 in which the test piston (B) was formed with an oil holding portion comprising three annular oil grooves opened (exposed) to the space inside the sealed container at the piston bottom dead center position near the center of the sliding portion on the outer periphery of the piston. It is. The test piston (C) has three oil grooves belonging to the oil holding part, and the distance between the upper end and the lower end of the oil holding part Lo is set longer than the anti-top part side sliding length Ls (Lo> Ls). Example 2.

  All pistons were set so that all parts were located in the cylinder 5a at the top dead center. The experimental results were obtained under the same conditions except for the oil grooves provided on the outer peripheral surface of the piston.

The piston according to Example 1 in which the oil holding portion Lo is set to be equal to or shorter than the anti-top portion side sliding length Ls (Lo ≦ Ls), and a plurality of oil grooves are provided in the oil holding portion (test piston) (B)) is a low-speed rotation with a rotational speed n of 1300 min ⁻¹ , and the piston friction loss Lpf is about 0.5 W than the piston of the comparative example provided with a stepped portion that is an oil supply means that the piston of Example 1 does not have. It was confirmed that it can be reduced and contribute to the lubrication improvement of the piston sliding part. The fact that the piston of Example 1 has a lower friction loss than the piston in which the stepped portion is further removed from the configuration of the piston of Comparative Example 1 to form a sliding portion is described in paragraph 0026 of FIG. It is clear from the fact that 3 etc. show.

  In the first embodiment according to the present invention, the number of the annular oil grooves 7c belonging to the oil holding portion is increased to a plurality, and Lo ≦ Ls as will be described later, so that excellent lubrication performance can be obtained without providing the stepped portion Ls ′. Since the piston outer peripheral area that slides with the cylinder inner diameter can be expanded, the load on the piston 7 can be reduced, and the wear of the piston 7 can be suppressed.

  When the oil holding portion Lo becomes longer than the anti-top-side sliding length Ls, it takes a long time for the oil holding portion Lo to pass the sliding lower end of the cylinder 5a in the compression stroke in which the piston 7 moves from the bottom dead center to the top dead center. Thus, the annular oil groove 7c comes into contact with the cylinder 5a under the action of the piston side pressure due to the increase in the cylinder internal pressure, so that the piston behavior is likely to become unstable, leading to an increase in piston friction loss.

Further, when the oil retaining portion Lo is partitioned in the vicinity of the center of the piston sliding length Lp, the pressure generated between the piston cylinders is uniform over the reciprocating motion of the piston, and the behavior of the piston 7 having a high degree of freedom of motion by the spherical bearing 7e. The lubricating oil can be secured in the annular oil groove 7c without adversely affecting the oil pressure. Thereby, the lubricity of the sliding part between piston 7 and cylinder 5a can be improved.
[Second and third embodiments]
The second and third embodiments have the same configuration as the first embodiment except for the following points.

FIG. 7 is an external front view showing another oil holding portion shape of the piston. (A) The figure relates to the second embodiment, and the number of the annular oil grooves 7c in the oil holding portion Lo is reduced by one compared to the first embodiment, thereby simplifying the oil groove processing and reducing the cost. Is intended. (B) The figure relates to the third embodiment, in which five narrow annular oil grooves 7c are formed at equal pitches in the oil retaining portion Lo in order to further stabilize the piston behavior.
[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The fourth embodiment is the same as the first embodiment except for the following points.

  FIG. 8 is an external front view showing the shape of the oil retaining portion of the piston according to the fourth embodiment of the present invention. In the present embodiment, the oil groove shape belonging to the oil retaining portion Lo is improved to improve the oil retaining property, and the behavior of the piston 7 is stabilized. At least two of the grooves or the like constituting each of the plurality of oil grooves belonging to the oil holding portion Lo according to the present embodiment are non-parallel to each other.

  The piston 7 of the present embodiment includes a broken line-shaped oil groove 7c ′ as an oil retaining portion Lo, preferably in the vicinity of the center of the piston sliding length Lp (FIGS. (A) and (b)) and cross hatching (ayame) ) -Shaped oil groove 7c "((c), (d)) is recessed.

  FIG. 8A is a diagram showing a broken line-shaped oil groove 7 c ′ which is an example of an oil groove belonging to the oil holding portion. The polyline-shaped oil groove 7c ′ is provided toward a plurality of grooves (first groove 7c′a) provided in the first direction and in a second direction that is not parallel to the first direction. A plurality of groove portions (second groove portion 7c'b) are included. In the present embodiment, each of the second groove portions is continuous with each of the substantially end portions of the first groove portion.

  FIG. 8C is a diagram showing an example in which a plurality of broken line-shaped oil grooves 7 c ′ are arranged. In the present embodiment, two broken line-shaped oil grooves 7 c ′ form a cross-hatched oil groove 7 c ″.

  FIG. 8B is a diagram illustrating an example in which the oil holding portion includes a broken line-shaped oil groove 7 c ′ and an annular oil groove. FIG.8 (d) is a figure which shows an example in which the oil holding | maintenance part contains the annular oil groove further in the oil groove which concerns on FIG.8 (c).

  By adopting such an oil groove shape, it is possible to more effectively suppress the lubricating oil accumulated in the oil grooves 7c ′ and 7c ″ from flowing down to the periphery due to the movement of the piston, thereby improving the oil retention. Here, the oil grooves 7c ′ and 7c ″ are formed by special processing such as machining (cutting or plastic working), electric discharge machining, or laser beam machining.

Also in this embodiment, the basic oil supply function between the piston and the cylinder bore is realized in the same manner as in the first embodiment by the action of the oil holding portion formed near the center of the piston sliding portion, and the sliding between the piston 7 and the cylinder 5a is achieved. It is possible to improve the lubricating performance of the compressor and improve the performance and reliability of the compressor.
[Fifth Embodiment]
The fifth embodiment is a refrigerator equipped with a hermetic compressor according to the first to fourth embodiments of the present invention. FIG. 9 is a longitudinal sectional view of a refrigerator equipped with a hermetic compressor according to the first to fourth embodiments.

In FIG. 9, the hermetic compressor 50 includes a cooler 66 and is mounted on a refrigerator 60 using a natural refrigerant R600a having a small warming coefficient, and includes a refrigerator compartment 62, an upper freezer compartment 63, a lower freezer compartment 64, a vegetable compartment. The internal space consisting of 65 is cooled by operating a refrigeration cycle (not shown) by driving the hermetic compressor 50.
In the embodiment described in detail above, the formation of an oil film between the piston and the cylinder is ensured, the sealing performance is improved, and the performance of the compressor at the time of low speed operation in the rotation speed control compressor by the inverter having a large influence of leakage is improved. It is possible to provide a hermetic compressor in which the reliability of the compressor can be improved.

  The system to which the hermetic compressor of the present invention is applied is not limited to a refrigerator, and can be applied to various devices such as a room air conditioner and a refrigerator in a refrigeration and air conditioning application. System efficiency can be greatly improved.

1 is a longitudinal sectional view of a hermetic compressor according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. The principal part expanded sectional view ((a) figure) of the sealed compressor which concerns on 1st Embodiment in the piston bottom dead center position vicinity, and the sealed form which concerns on 1st Embodiment in the piston top dead center position vicinity. It is a principal part expanded sectional view ((b) figure) of a compressor. It is sectional drawing ((a) figure) and this side view ((b) figure) of the piston which concern on 1st Embodiment. It is an external appearance front view of the piston concerning a 1st embodiment. It is an experimental result which shows the friction loss reduction effect of the piston which concerns on 1st Embodiment. It is an external appearance front view which shows the other oil holding part shape of the piston which concerns on 2nd, 3rd embodiment. It is an external appearance front view which shows the oil holding | maintenance part shape of the piston which concerns on the 4th Embodiment of this invention. It is a longitudinal cross-sectional view of the refrigerator carrying the hermetic compressor which concerns on each embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Sealed container, 2 ... Electric element, 2a ... Stator, 2b ... Rotor, 3 ... Compression element, 4 ... Lubricating oil, 5 ... Cylinder block, 5a ... Cylinder, 5aa ... Chamfer (opening), 5b ... Frame part, 5c ... Bearing portion, 6 ... Connecting rod, 7 ... Piston, 7a ... Piston top, 7b, 7c ... Annular oil groove, 7c ', 7c "... Oil groove, 7e ... Spherical bearing, 8 ... Crankshaft, 8a ... Main shaft, 8b ... Eccentric shaft, 8ba ... oil supply groove, 8bb ... lubricating oil radiation hole, 8c ... oil pump, 8d ... spiral oil groove, 9 ... balance weight, 10 ... cylinder head, 11 ... head cover, 11a ... discharge chamber, 12 ... compression operation Chamber 13, Oil reservoir 13 a Partition wall 14 Discharge pipe 15 Discharge pipe 16 Suction pipe 17 Suction silencer 18 Discharge silencer 50 Sealed compressor 60 Built box, 61 ... refrigerator body, 62 ... refrigerating compartment, 63 ... upper freezing room, 64 ... lower freezer compartment, 65 ... vegetable compartment, 66 ... cooler

Claims (5)

A compression element having a cylinder and a piston reciprocating in the cylinder;
A hermetic compressor comprising an oil supply section for supplying lubricating oil to the compression element,
An oil holding portion that is exposed through the opening of the cylinder at the bottom dead center position of the piston and has a plurality of oil grooves located in the cylinder at the top dead center position of the piston is provided in the piston,
The length of the oil holding part in the axial direction of the piston is equal to or less than the length of the sliding part belonging to the lower end side from the lower end part of the oil holding part.   The hermetic compressor according to claim 1, wherein the oil retaining portion includes an annular oil groove.   The oil retaining portion includes an oil groove including a plurality of first groove portions provided in the first direction and a plurality of second groove portions provided in the second direction. The hermetic compressor according to claim 1 or 2.   The hermetic compressor according to any one of claims 1 to 3, wherein the oil retaining portion is provided at a substantially center in an axial direction of the piston.   An apparatus comprising the hermetic compressor according to any one of claims 1 to 4.