WO2009088179A2

WO2009088179A2 - Reciprocating compressor

Info

Publication number: WO2009088179A2
Application number: PCT/KR2008/007893
Authority: WO
Inventors: Dong-Woo Park; Hyun-Suk Joo; Kyeong-Ho Kim; Jong-Mok Lee; Young-Hwan Kim
Original assignee: Lg Electronics Inc.
Priority date: 2008-01-10
Filing date: 2008-12-31
Publication date: 2009-07-16
Also published as: WO2009088179A3; CN101952594A; CN101952594B

Abstract

The present invention relates to a reciprocating compressor. According to the present invention, as an inner circumferential surface of a cylinder block or an outer circumferential surface of a piston is provided with a friction avoiding portion by a specific length and a specific depth or stepped surfaces forming the friction avoiding portion are indented, a friction area between the cylinder block and the piston is decreased and a compression chamber is effectively sealed. Accordingly it is capable of enhancing reliability of the compressor.

Description

RECIPROCATING COMPRESSOR

Technical Field

[1] The present invention relates to a piston of reciprocating compressor.

Background Art

[2] Generally, a reciprocating compressor is operated in a manner that a piston is linearly reciprocated in a compression chamber of a cylinder block and thus a refrigerant is sucked, compressed and discharged. The reciprocating compressors may be classified into a connection type reciprocating compressor and a vibration type reciprocating compressor according to a driving manner of a piston. The connection type reciprocating compressor is configured to compress a refrigerant in a manner that the piston is connected to a rotation shaft of a rotary motor through a connecting rod and then is reciprocated in a compression chamber of a cylinder block. Meanwhile, the vibration type reciprocating compressor is configured to compress a refrigerant in a manner that the piston is vibrated by being connected to a mover of a reciprocating motor and thus is reciprocated in a cylinder. Hereafter, the connection type reciprocating compressor is referred to as a reciprocating compressor and is applied to embodiments. However, the embodiments are not necessarily applied by the connection type reciprocating compressor.

[3] The reciprocating compressor includes a hermetic container, a driving motor installed at the hermetic container and generating a rotational force, and a compression mechanism unit in which a piston coupled to a rotation shaft of the driving motor converts a rotating motion of the driving motor into a linear motion and then is linearly reciprocated in a cylinder block so as to compress a refrigerant. Thus, a friction surface is generated between the piston and the cylinder block. The reciprocating compressor is configured to supply oil in the hermetic container to the friction surface in a pumping manner. Disclosure of Invention Technical Problem

[4] In the related reciprocating compressor, even though the oil is supplied toward between an inner circumferential surface of the cylinder block and an outer circumferential surface of the piston, it is not sufficient to decrease a friction loss because a friction area between the cylinder block and the piston is large. If the friction area becomes immoderately small, an oil film may be damaged, which may have a bad influence on reliability of the compressor. More concretely, a recess may be formed in the middle of the outer circumferential surface of the piston in a circular band shape so as to decrease the friction area between the cylinder block and the piston. In this case, if the recess is configured to lean to a front side of the piston, that is, in a direction toward a compression chamber, a sealing area of the piston is decreased and thus the refrigerant in the compression chamber may leak through the friction surface between the cylinder block and the piston. On the contrary, if the recess is configured to lean to a rear side of the piston, that is, in a direction opposite to the compression chamber, a faceted end surface of the recess may be locked by a front end surface of the cylinder block when the piston is backwardly moved. Thus, the piston may not be facilitatingly reciprocated, which may deteriorate reliability of the compressor.

[5] Therefore, it is an object of the present invention to provide a reciprocating compressor which is capable of maintaining reliability of the compressor by effectively sealing a compression chamber and stably reciprocating the piston, with decreasing a friction area between a cylinder block and a piston. Technical Solution

[6] To achieve the object, in accordance with one aspect of the present invention, there is provided a reciprocating compressor comprising a cylinder block forming a compressing chamber; and a piston performing reciprocating motions in the cylinder block so as to suck and compress a refrigerant in the compression chamber, wherein a friction avoiding portion is concavely formed at an outer circumferential surface of the piston in a range of approximately 1/10-1/2 of an entire length (L) of the piston.

[7] In accordance with another aspect of the present invention, there is provided a reciprocating compressor comprising a cylinder block forming a compressing chamber; and a piston performing reciprocating motions in the cylinder block so as to suck and compress a refrigerant in the compression chamber, wherein a front bearing portion and a rear bearing portion are respectively formed at an outer circumferential surface of front and rear sides of the piston to slidingly come in contact with the cylinder block and a friction avoiding portion having specific width and depth is formed in a stepped format along a circumferential direction of the piston between the front bearing portion and the rear bearing portion.

[8] In accordance with still another aspect of the present invention, there is provided a reciprocating compressor comprising a cylinder block forming a compressing chamber; and a piston performing reciprocating motions in the cylinder block so as to suck and compress a refrigerant in the compression chamber, wherein a friction avoiding portion having specific length and depth is concavely formed at an inner circumferential surface of the compression chamber of the cylinder block.

Advantageous Effects

[9] According to the reciprocating compressor of the present invention, as the inner circumferential surface of the cylinder block or the outer circumferential surface of the piston is provided with a friction avoiding portion by a specific length and a specific depth, the friction area between the cylinder block and the piston is decreased and it is prevented a damage of the oil film, accordingly it is capable of effectively sealing the compression chamber, thereby being capable of enhancing reliability of the compressor. Brief Description of the Drawings

[10] FIG. 1 is a longitudinal section view showing a reciprocating compressor in accordance with the present invention;

[11] FIG. 2 is a perspective view showing one example of a piston in the reciprocating compressor in accordance with FIG. 1;

[12] FIG. 3 is a section view showing a configuration of a friction avoiding portion in the piston in accordance with FIG. 2;

[13] FIGS. 4 and 5 are a section view and a perspective view schematically showing other embodiments of a friction avoiding portion in the reciprocating compressor in accordance with FIG. 1 ;

[14] FIG. 6 is a graph showing changes of an input power according to a length of the friction avoiding portion in the reciprocating compressor in accordance with FIG. 1 ;

[15] FIG. 7 is a graph showing changes of a thickness of an oil film according to a length of the friction avoiding portion in the reciprocating compressor in accordance with FIG. 1;

[16] FIGS. 8 and 9 are a perspective view and a section view showing another embodiment of a piston in the reciprocating compressor in accordance with FIG. 1;

[17] FIGS. 10 and 11 are a perspective view and a section view showing still another embodiment of a piston in the reciprocating compressor in accordance with FIG. 1;

[18] FIGS. 12 to 15 are perspective views showing other embodiments of a piston in the reciprocating compressor in accordance with FIG. 1 ; and

[19] FIG. 16 is section view schematically showing another embodiment of a friction avoiding portion in a reciprocating compressor in accordance with the present invention. Best Mode for Carrying Out the Invention

[20] Hereafter, description will now be given in detail of a reciprocating compressor according to the present invention with accompanying drawings.

[21] As shown in FIG. 1, the reciprocating compressor according to the present invention includes a gear mechanism unit 2 installed in a casing 1 and generating a rotation force by a power supplied from an outside, and a compression mechanism unit 3 coupled to the gear mechanism unit 2 in the casing 1 and compressing a refrigerant with being linearly reciprocated using the friction force from the gear mechanism unit 2.

[22] The gear mechanism unit 2 includes a stator 12 elastically supported by the casing 1 and wound with a coil 11, a rotor 13 rotatably disposed in the middle of the stator 12, and a rotation shaft 14 coupled to the center of the rotor 13 and transferring a friction force to the compression mechanism unit 3.

[23] The compression mechanism unit 3 includes a cylinder block 110 disposed in the casing 1 in a width direction and having one side provided with a compression chamber (Vl) in a radial direction, a sleeve 120 rotatably inserted with being eccentric to the rotation shaft 14 placed on an upper surface of the cylinder block 110, a connecting rod 130 coupled to an outer circumferential surface of the sleeve 120 and converting a rotating motion of the rotation shaft 14 into a reciprocating motion of a piston 140 to be explained, the piston 140 coupled to another end of the connecting rod 130 and reciprocated in a radial direction of the rotation shaft 14 in the compression chamber (Vl) of the cylinder block 110, a valve assembly 150 installed at a discharge side of the cylinder block 110 and controlling suctioning and discharging of a refrigerant, a discharge cover 160 installed at one side of the cylinder block 110 and fixed at the valve assembly 150 with having a specific discharge chamber (V2), a suction muffler 170 coupled to the discharge cover 160 to be communicated with a suction side of the valve assembly 150, and a discharge muffler 180 mounted at the cylinder block 110 to be communicated with the discharge side of the valve assembly 150 through the discharge cover 160.

[24] The cylinder block 110 is configured to have an inner circumferential surface of the compression chamber (Vl) which is formed in a circular shape. The piston 140 is configured to have an outer circumferential surface formed in a circular shape to correspond to the compression chamber (Vl) of the cylinder block 110. And, as shown in FIG. 2, a pin hole 141 is formed at a central portion of the piston 140 to be coupled to the connecting rod 130. And, a friction avoiding portion 142 having specific length and depth is formed at one side of the circumferential surface, that is, a side coupled to the connecting rod 130 (hereafter, referred to as a rear side end). A reference numeral 143 denotes a connecting rod coupling groove.

[25] As shown in FIGS. 2 and 3, the friction avoiding portion 142 is configured to be stepped to be intaglioed toward a front side from the rear side end of the piston 140. The friction avoiding portion 142 may be configured to have a length (Q) of approximately 1/10-1/2 of an entire length (L) of the piston and have a depth (H) of approximately 3-7/M, more precisely, approximately 5/M, preferably. In case the length of the friction avoiding portion 142 is immoderately short, friction may not be effectively decreased. On the contrary, in case the length (Q) of the friction avoiding portion 142 is excessively long, an oil film may be damaged and thus reliability may be deteriorated. The friction avoiding portion 142 had better be configured to be inclined toward the front side of the friction avoiding portion 142 or to be rounded so as to further decrease a friction loss.

[26] The friction avoiding portion 142 may be formed toward the front side from the rear side end as shown in FIG. 2. Alternately, the friction avoiding portion 142 may be formed to be intaglioed at the middle portion of the piston 140 as shown in FIG. 4. In this case, a diameter (D2) of an opposite side of the piston head, that is, the rear side had better be shorter than a diameter (Dl) of a piston head so as to further reduce a friction loss.

[27] The friction avoiding portion 142 may be formed in a circular section shape as shown in FIGS. 2 to 4. Alternately, the friction avoiding portion 142 may be implemented as a plurality of rectangular shaped recesses having a specific length in a length direction of the piston 140 and spaced from each other by a constant gap therebetween along a circumferential direction as shown in FIG. 5. In this case, the length (Q) of the friction avoiding portion 142 may be approximately 1/10-1/2 of the entire piston length (L). However, since a slippery surface exists between the friction avoiding portions 142, the length (Q) may be slightly longer comparing with a case that the friction avoiding portion is formed to have the circular section. And, the depth (H) of the friction avoiding portion 142 is approximately 5/M which is similar to the case that the friction avoiding portion 142 is formed to have the circular section, preferably.

[28] The reciprocating compressor according to the present invention has the following effects.

[29] Once a power is applied to the gear mechanism unit 2, the rotation shaft 14 is rotated by a reciprocal action between the stator 12 and the rotor 13 and the connecting rod 130 inserted into an eccentric portion 14b of the rotation shaft 14 together with the sleeve 120 of the compression mechanism unit 3 performs a linear motion with performing an orbiting motion. Thus, the piston 140 is reciprocated in the compression chamber (Vl) of the cylinder block 110. And accordingly, the refrigerant is sucked into the compression chamber (Vl) of the cylinder block 110 through a suction valve (not shown) of the suction muffler 170 and the valve assembly 150 and then discharged by sequentially passing through the discharge chamber (V2) and the discharge muffler 180 of the discharge cover 160 through a discharge valve (not shown) of the valve assembly 150. This process is repeatedly performed.

[30] Here, a friction loss may generate in the process that the piston 140 is reciprocated in the compression chamber (Vl) of the cylinder block 110. However, as the friction avoiding portion 142 having the specific depth (H) and length (Q) is formed at the outer circumferential surface of the piston 140 in the present invention, the friction loss between the piston 140 and the cylinder block 110 may be decreased. Particularly, as shown in FIG. 6, as a result of an experiment on changes of an input power by forming the friction avoiding portion 142 to have a circular section having the depth of 5/M and varying the length (Q) of the friction avoiding portion 142, a ratio (Q/L) between the entire length (L) of the piston 140 and the length (Q) of the friction avoiding portion decreases at a point that the ratio is approximately 1/10 and then increases from a point that the ratio (Q/L) is 1/2. Thus, the length (Q) of the friction avoiding portion had better be within a range of approximately 1/10-1/2 of the entire length (L) of the piston so as to prevent the input power from increasing, preferably.

[31] And, FIG. 7 is a graph showing changes of a thickness of an oil film according to a length of the friction avoiding portion 142. As shown in the drawing, the oil film is thickest when the length (Q) of the friction avoiding portion occupies approximately 1/5 of the entire length (L) of the piston. And, the oil film becomes thinner as the length (L) of the friction avoiding portion becomes longer and then is damaged at a point of approximately 1/2L. Thus, the length (Q) of the friction avoiding portion is the same as or shorter than approximately 1/2L so as to prevent damage of the oil film, preferably. Mode for the Invention

[32] Meanwhile, another embodiment of the reciprocating compressor in accordance with the present invention will be explained as follows.

[33] In the abovementioned embodiment, a bearing portion is formed at the front side of the piston, that is, at a side coming in contact with the compression chamber and the friction avoiding portion is formed at the opposite side thereof, that is, at a side not coming in contact with the compression chamber. In this embodiment, a front bearing portion and a rear bearing portion are respectively formed at both front and rear sides of a piston and a friction avoiding portion having specific depth and length is formed between the front bearing portion and the rear bearing portion.

[34] As shown in FIGS. 8 to 15, a pin hole 241 is penetratingly formed at the middle portion of the piston in a radial direction so as to be coupled to a connecting rod 230. And, the front bearing portion 242 and the rear bearing portion 243 are respectively formed at both sides of a length direction of the pin hole 241, that is, in directions of the compression chamber and in the opposite direction, so that an outer circumferential surface of the piston 240 may slidably come in contact with an inner circumferential surface of the cylinder block 210. And, the friction avoiding portion 244 having specific width and depth are concavely formed between the front bearing portion 242 and the rear bearing portion 243. Here, the friction avoiding portion 244 may be formed to have a depth of approximately 3-7/M, more precisely, approximately 5/M, which is same as the abovementioned embodiment. A reference numeral 245 denotes a connecting rod coupling groove.

[35] As shown in FIGS. 8 to 11, a stepped surface 246 (hereafter, referred to as a first stepped surface) between the front bearing portion 242 and the friction avoiding portion 244 or another stepped surface 247 (hereafter, referred to as a second stepped surface) between the rear bearing portion 243 and the friction avoiding portion 244 may have a waveform section along a circumferential direction, respectively.

[36] Here, the first stepped surface 246 and the second stepped surface 247 may correspond to each other so that a width (W) of the friction avoiding portion 244 may be uniform in the circumferential direction as shown in FIGS. 8 and 9. Alternately, the first stepped surface 246 and the second stepped surface 247 may correspond to each other so that the width of the friction avoiding portion 244 may be not uniform in the circumferential direction as shown in FIGS. 10 and 11.

[37] And, a plurality of grooves 243a are formed on the outer circumferential surface of the rear bearing portion 243 with being spaced from each other by the same gap therebetween so as to further reduce the friction loss. The recesses 243a may be implemented as circular grooves as shown in FIG. 12. Alternately, the grooves 243a may be formed in a linear shape to penetrate both ends of the rear bearing portion 243, as shown in FIG. 13.

[38] And, the first stepped surface 246 and the second stepped surface 247 are formed in a concavo-convex shape as shown in FIG. 14. Alternately, the first stepped surface 246 may be formed in a straight line shape and the second stepped surface 247 may be formed in the concavo-convex shape. This may be applied same to the case of waveform.

[39] Effects of the reciprocating compressor having the piston in accordance with this embodiment is same as those of the aforementioned embodiment, thus the detailed explanation will be omitted. But, as at least one of the first stepped surface 246 and the second stepped surface 247 forming the friction avoiding portion 244 is indented, the substantial friction area is reduced and a bearing range, that is, a range supporting the reciprocating motion of the piston 240 when the piston 240 is slidingly reciprocated in the cylinder block 210, is extended to a portion that the first stepped surface 246 and the second stepped surface 247 are indented. Accordingly, the length of the front bearing portion 242 can be maintained up to a sealing length and the length of the rear bearing portion 243 can be maintained up to a safety length that the piston 240 are not locked by an end edge of the cylinder block 210.

[40] Meanwhile, still another embodiment of the reciprocating compressor in accordance with the present invention will be explained as follows.

[41] In the abovementioned embodiment, the friction avoiding portion is formed at the outer circumferential surface of the piston. In this embodiment, a friction avoiding portion is formed at an inner circumferential surface of a cylinder block. As shown in FIG. 16, the friction avoiding portion 111 is formed in a range of a bearing length (Ll) of the cylinder block and a length (Q) of the friction avoiding portion is formed in a range occupying approximately 1/2 of the bearing length (Ll) of the cylinder block so as to reduce loss of the input power and to prevent the oil film from being damaged, preferably.

[42] And, the friction avoiding portion 111 may be formed to have a depth (H) of approximately 3-7/M, more precisely, approximately 5/M, same as the aforementioned embodiment. And, an inside diameter at a side of a valve assembly 150 may be smaller than that at the opposite side thereof centering the friction avoiding portion 111. The configuration and effects thereof are same as those of the aforementioned embodiment, thus detailed explanation will be omitted. Industrial Applicability

[43] The reciprocating compressor in accordance with the present invention may be applied to the connection type reciprocating compressor like this embodiment and also applied to a vibration type reciprocating compressor using linear motion of a piston. Such reciprocating compressor may be broadly used for a refrigerator or a freezing apparatus such as an air controller. [44] It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

[1] . A reciprocating compressor comprising: a cylinder block forming a compressing chamber; and a piston performing reciprocating motions in the cylinder block so as to suck and compress a refrigerant in the compression chamber, wherein a friction avoiding portion is concavely formed at an outer circumferential surface of the piston in a range of approximately 1/10-1/2 of an entire length (L) of the piston.

[2] The reciprocating compressor of claim 1, wherein the friction avoiding portion has a depth of approximately 3-7/M.

[3] The reciprocating compressor of claim 1 or 2, wherein the friction avoiding portion is formed in a waveform along a circumferential direction of the piston.

[4] The reciprocating compressor of claim 1 or 2, wherein the friction avoiding portion is lengthwise formed in plurality in number with distances therebetween along a circumferential direction of the piston.

[5] The reciprocating compressor of claim 1 or 2, wherein the friction avoiding portion is formed at an end of the piston in a length direction.

[6] A reciprocating compressor comprising: a cylinder block forming a compressing chamber; and a piston performing reciprocating motions in the cylinder block so as to suck and compress a refrigerant in the compression chamber, wherein a front bearing portion and a rear bearing portion are respectively formed at an outer circumferential surface of front and rear sides of the piston to slidingly come in contact with the cylinder block and a friction avoiding portion having specific width and depth is formed in a stepped format along a circumferential direction of the piston between the front bearing portion and the rear bearing portion.

[7] The reciprocating compressor of claim 6, wherein the front bearing portion and the rear bearing portion have diameters different from each other.

[8] The reciprocating compressor of claim 6, wherein at least one of stepped surfaces between both bearing portions and the friction avoiding portion is indented along a circumferential direction of the piston.

[9] The reciprocating compressor of claim 6, wherein the stepped surfaces forming the friction avoiding portion are formed to have a waveform section or a concavo-convex section. [10] The reciprocating compressor of claim 6, wherein the stepped surfaces between both bearing portions and the friction avoiding portion correspond to each other so that a width of the friction avoiding portion may be uniform along a circumferential direction. [11] The reciprocating compressor of claim 6, wherein the stepped surfaces between both bearing portions and the friction avoiding portion are symmetric to each other so that a width of the friction avoiding portion may not be uniform along a circumferential direction. [12] The reciprocating compressor of claim 6, wherein a plurality of grooves are further formed at an outer circumferential surface of a rear bearing portion not coming in contact with the compression chamber between both bearing portion of the piston. [13] The reciprocating compressor of claim 12, wherein a diameter of the grooves is smaller than a width of the rear bearing portion. [14] The reciprocating compressor of claim 12, wherein the grooves are formed to be linear so as to penetrate both ends of the rear bearing portion in a length direction thereof. [15] The reciprocating compressor of claim 6, wherein the friction avoiding portion has a depth of approximately 3-7/M. [16] A reciprocating compressor comprising: a cylinder block forming a compressing chamber; and a piston performing reciprocating motions in the cylinder block so as to suck and compress a refrigerant in the compression chamber, wherein a friction avoiding portion having specific length and depth is concavely formed at an inner circumferential surface of the compression chamber of the cylinder block. [17] The reciprocating compressor of claim 16, wherein the friction avoiding portion has a length shorter than approximately 1/2 of a length (Ll) of a bearing of the cylinder block. [18] The reciprocating compressor of claim 16, wherein the friction avoiding portion has a depth of approximately 3-7/M. [19] The reciprocating compressor of claim 16, wherein the friction avoiding portion is formed in a circular shape along a circumferential direction of the cylinder block. [20] The reciprocating compressor of claim 16, wherein the friction avoiding portion is lengthwise implemented in plurality in number with being spaced from each other by distances therebetween along a circumferential direction of the cylinder block.