Reciprocating Compressor

Abstract

A reciprocating compressor includes a piston which compresses air by, while rocking, reciprocatingly moving in a cylinder and a sealing member which is fitted in a groove formed on the piston for sealing between the cylinder and the piston. In the reciprocating compressor: the sealing member has a bottom portion to be fitted in the groove formed on the piston and a side portion provided radially outwardly of the piston; and the side portion includes a bent portion so as to reduce a gap between an upper end portion thereof and the piston.

Description

BACKGROUND

The present invention relates to a reciprocating compressor.

A background technique in the present technical field is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2011-12603. In the patent literature, a multi-stage compressor is disclosed which includes a rocking piston provided with a lip ring having an upper sealing portion and a lower sealing portion with the former being more susceptible to elastic deformation than the latter.

SUMMARY

The upper sealing portion of the lip ring disclosed in the above-mentioned patent literature is designed to be easily elastically deformable, so that it tends to be excessively deformed to increase the stress applied to a curved portion of the lip ring. Furthermore, since a large gap is formed between the upper sealing portion of the lip ring and the piston when the piston tilts relative to the cylinder, the lip ring is pressed against the inner peripheral surface of the cylinder causing the stress applied to the curved portion of the lip ring to be further increased. Therefore, the life of the lip ring cannot be lengthened.

The present invention has been made in view of the above problem, and it is an object of the present invention to provide a reciprocating compressor in which the stress applied to the lip ring is reduced so as to lengthen the life of the lip ring.

To address the above problem, the present invention provides a reciprocating compressor having a piston which compresses air by, while rocking, reciprocatingly moving in a cylinder and a sealing member which is fitted in a groove formed on the piston for sealing between the cylinder and the piston. In the reciprocating compressor: the sealing member has a bottom portion to be fitted in the groove formed on the piston and a side portion provided radially outwardly of the piston; and the side portion includes a bent portion so as to reduce a gap between an upper end portion thereof and the piston.

The reciprocating compressor according to the present invention can reduce the stress applied to the lip ring used therein and can thereby lengthen the life of the lip ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the main body of a reciprocating compressor according to a first embodiment of the present embodiment;

FIG. 2 shows sectional views of a piston and a cylinder according to the first embodiment of the present invention;

FIG. 3A shows a sectional view of a lip ring according to the first embodiment of the present invention;

FIG. 3B shows sectional views of the lip ring according to the first embodiment of the present invention;

FIG. 4 shows sectional views of a lip ring according to a first example case for comparison with the present invention;

FIG. 5 shows sectional views of the lip ring in a rocking state according to the first example case for comparison with the present invention;

FIG. 6 shows sectional views of the lip ring in a rocking state according to a second example case for comparison with the present invention;

FIG. 7 shows sectional views of the lip ring in a rocking state according to the second example case for comparison with the present invention;

FIG. 8 shows a sectional view of a lip ring according to a second embodiment of the present invention;

FIG. 9 shows a sectional view of a lip ring according to a third embodiment of the present invention; and

FIG. 10 shows a sectional view of a lip ring according to the third embodiment of the present invention.

DETAILED DESCRIPTION

First Embodiment

A reciprocating compressor according to a first embodiment of the present invention will be described below with reference to FIG. 1 to FIGS. 3A and 3B.

FIG. 1 is a sectional view of the main body of the reciprocating compressor according to the present embodiment.

A crankcase 1 of the reciprocating compressor is for forming an internal crank chamber 2. The crankcase 1 is broadly comprised of a cylindrical case section 1A having a horizontal axis and a cylinder mounting seat 1B provided on the upper side of the cylindrical case section 1A. In the crank chamber 2 included in the crankcase 1, a crankshaft 5 is rotatably supported. The crankshaft 5 is integrally provided with a balance weight 6. The crankshaft 5 is connected to an output shaft 4 of an electric motor 3 and is driven by the electric motor to rotate eccentrically.

A cylinder 7 is mounted on the cylinder mounting seat 1B included in the crankcase 1. An inner peripheral surface 7A of the cylinder 7 serves as a sliding surface for a lip ring 22 being described later. A cylinder head 8 is mounted on the top side of the cylinder 7. A discharge chamber 10 for discharging compressed air is formed in the cylinder head 8.

A piston rod 14 is, at its base end, rotatably connected to the crankshaft 5 via a bearing 15. When the crankshaft 5 driven by the electric motor 3 eccentrically rotates, a piston 16 provided at an end portion of the piston rod 14 reciprocatingly moves while rocking in the cylinder 7 as shown in FIG. 2. In the cylinder 7, a compression chamber 17 is formed between the piston 16 and a valve seat plate 11. The piston 16 includes a piston main part 18, a retainer 19, and a ring receiving groove 21.

The piston main part 18 is integrally connected, at an underside central portion thereof, with an end portion of the piston rod 14. The retainer 19 is detachably attached to the upper side of the piston main part 18 so that it can hold the lip ring 22 between itself and the piston main part 18.

The lip ring 22 fitted on the outer circumferential side of the piston main part 18 is a sealing member for sealing between the piston 16 and the cylinder 7 so as to prevent air (pressure) leakage from the compression chamber 17. The lip ring 22 is made of, for example, an abrasion-resistant, self-lubricating resin material and has an L-shaped cross-section.

The lip ring 22 of the present embodiment will be described with reference to FIGS. 3A and 3B. FIG. 3A is a sectional view of the lip ring 22 without any pressure applied thereto. FIG. 3B is a sectional view of the lip ring 22 subjected to a pressure with the piston 16 in a tilted state. The lip ring 22 has an annular shape and includes a bottom portion 22A to be fitted in a groove on the piston 16 and a side portion 22B formed radially outwardly of the piston 16. The side portion 22B opens wider upwardly, i.e. toward the compression chamber 17 and slidingly contacts the inner peripheral surface 7A of the cylinder 7 for sealing between the cylinder 7 and the piston 16.

According to the present embodiment, the side portion 22B of the lip ring 22 has a top end portion 22B1, a base end portion 22B2, and a bent portion 22B3. The top end portion 22B1 is positioned on the upper end side of the side portion 22B. The base end portion 22B2 is positioned on the base end side (lower end side) of the side portion 22B and extends from the bottom portion 22A radially outwardly and diagonally upwardly of the piston 16 to be connected to the top end portion 22B1 via the bent portion 22B3. The bent portion 22B3 is positioned between the top end portion 22131 and the base end portion 22B2. The side portion 22B of the lip ring 22 includes plural bends (i.e. a flat surface is bent at plural angles or, in the case of a curved surface, its tangential angle is discontinuously changed).

An angle θ1 formed between the top end portion 22B1 and the axial direction of the piston 16 is smaller than an angle θ2 formed between the base end portion 22B2 and the axial direction of the piston 16. Namely, with the bent portion 22B3 formed, the gap between the top end portion 22B1 of the side portion 22B and the piston 16 is narrower than in cases where the bent portion 22B3 is not formed. This reduces deformation of the lip ring 22 caused when the piston 16 is tilted and pressed against the inner peripheral surface 7A of the cylinder 7, so that the stress applied to the lip ring 22 is reduced. In FIG. 3B, the magnitude of stress applied to the lip ring 22 is represented by the degree of shading. In FIG. 3B, compared with FIG. 5, there is almost no dark shading in portions expected to be subjected to stress concentration of the lip ring 22, indicating that the stress applied to the lip ring 22 is reduced.

Increasing the angle θ2 formed between the base end portion 22B2 and the axial direction of the piston 16 allows the base end portion 22B2 to be tilted more toward the radial direction of the piston 16 so as to cause the top end portion 22B1 to contact the inner peripheral surface 7A of the cylinder 7 at a location farther from the piston 16. In this way, a gap S between where the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 contact each other and the piston 16 can be widened as shown in FIG. 3B, so that the inner peripheral surface 7A of the cylinder 7 and the piston 16 can be prevented from contacting each other.

The angle θ2 formed between the base end portion 22B2 and the axial direction of the piston 16 is larger than the rocking angle θ (the angle formed between the axial direction of the piston 16 in a state most tilted relative to the cylinder 7 and the inner peripheral surface 7A of the cylinder 7). In this way, even when the piston 16 is most tilted relative to the cylinder 7, the base end portion 22B2 can move radially outwardly of the piston 16 allowing the contact between the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 to be radially outside the base end portion 22B2. Thus, the gap S can be adequately secured between where the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 contact each other and the piston 16. In this way, even when the piston 16 is most tilted relative to the cylinder 7, the inner peripheral surface 7A of the cylinder 7 and the piston 16 are prevented from contacting each other.

As shown in FIG. 3A, when the lip ring 22 is subjected to no pressure, the lower end (bottom) of the lip ring 22 does not project outwardly from the piston 16. This reduces the outward projection of the lower end (bottom) of the lip ring 22 from the piston 16 in a state with a pressure applied to the lip ring 22. In this arrangement, the stress generated when the piston 16 bites into the lower end (bottom) of the lip ring 22 is reduced.

FIGS. 4 and 5 show enlarged sectional views of the lip ring 22 used in a first example case for comparison with the present embodiment. In the first example case for comparison, the side portion 22B of the lip ring 22 has a curved surface of a uniform curvature without any angled bend. With the side portion 228 having a curved surface of a uniform curvature, when the piston 16 rocks, the side portion 22B of the lip ring 22 is largely deformed as shown in FIG. 5 causing the bottom portion 22A and the side portion 22B to be subjected to a large stress. In FIG. 5, the magnitude of stress applied to the lip ring 22 is represented by the degree of shading. In FIG. 5 compared with FIG. 3B, large portions of the lip ring 22 are darkly shaded indicating stress concentration between the bottom portion 22A and the side portion 22B.

FIGS. 6 and 7 show sectional views of the lip ring 22 used in a second example case for comparison with the present embodiment. In the second example case, the lip ring 22 is formed to have an L-shaped section. In the second example case with the side portion 22B being flat-surfaced, deformation of the lip ring 22 caused by rocking of the piston 16 is smaller than in the first example case, so that the stress applied to the bottom portion 22A and side portion 22B is also smaller than in the first example case.

Referring to FIG. 6, a gap S between where the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 contact each other and the piston 16 is adequately secured so as to prevent the inner peripheral surface 7A of the cylinder 7 and the piston 16 from contacting each other. In this case, when the lip ring 22 is subjected to no pressure, the lower end (bottom) of the lip ring 22 projects outwardly from the piston 16. This increases the outward projection of the lower end (bottom) of the lip ring 22 from the piston 16 when a pressure is applied to the lip ring 22. In this arrangement, the stress applied to the bottom portion 22A of the lip ring 22 when the piston 16 bites into the lower end (bottom) of the lip ring 22 cannot be reduced.

Referring to FIG. 7, when the lip ring 22 is subjected to no pressure, the lower end (bottom) of the lip ring 22 does not project outwardly from the piston 16. This is to reduce the stress generated when the piston 16 bites into the lower end (bottom) of the lip ring 22. In this case, however, a gap S between where the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 contact each other and the piston 16 cannot be adequately secured.

Thickening the upper end side of the side portion 22B of the lip ring 22 makes it possible to reduce the stress applied to the lip ring 22 and prevent the inner peripheral surface 7A of the cylinder 7 and the piston 16 from contacting each other. Doing so, however, excessively increases the rigidity of the upper end side of the side portion 22B. This makes it less easy for the lip ring 22 to open wider upwardly for enhanced sealing.

As described above, according to the present embodiment, the side portion 22B of the lip ring 22 has the top end portion 2231, the base end portion 22B2, and the bent portion 22B3, and the gap between the side portion 22B and the piston 16 is smaller on the upper end side of the side portion 22B. In this way, the stress applied to the lip ring 22 is reduced. Also, the gap S between where the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 contact each other and the piston 16 can be widened, so that the inner peripheral surface 7A of the cylinder 7 and the piston 16 can be prevented from contacting each other. Furthermore, in this arrangement, the upper end side of the side portion 22B of the lip ring 22 does not become too rigid, so that the lip ring 22 can retain adequate sealing performance. This lengthens the life of the lip ring 22 making it possible to provide a reciprocating compressor which can maintain high reliability for a long period of time.

Second Embodiment

A reciprocating compressor according to a second embodiment of the present invention will be described with reference to FIG. 8. Parts identical to those described above in connection with the first embodiment will be denoted by identical reference numerals as used above and their description will be omitted.

In the second embodiment, the top end portion 22B1 of the side portion 22B of the lip ring 22 includes plural bends. As shown in FIG. 8, an angle θ1 formed between the top end portion 22B1 and the axial direction of the piston 16 is smaller than an angle θ2 also formed between the top end portion 22B1 and the axial direction of the piston 16. Namely, the angle formed on the upper end side of the top end portion 22131 is smaller than the angle formed on the base end side of the top end portion 22B1. In the second embodiment, too, like in the first embodiment, the angles θ1 and θ2 formed between the top end portion 22B1 and the axial direction of the piston 16 are smaller than an angle θ3 formed between the base end portion 22B2 and the axial direction of the piston 16.

In the present embodiment, with the top end portion 22B1 including plural bends, the top end portion 22E1 extends more closely along the axial direction of the piston 16 on the upper end side than on the base end side. This prevents the gap between the upper end side of the side portion 22B of the lip ring 22 and the piston 16 from becoming too wide. In this way, the stress applied to the lip ring 22 is further reduced compared with the first embodiment. Also compared with the first embodiment, the side portion 22B of the lip ring 22 and the inner peripheral surface 7A of the cylinder 7 contact each other at a location radially more outward from the piston 16, so that the inner peripheral surface 7A of the cylinder 7 and the piston 16 can be more securely prevented from contacting each other.

Even though, in FIG. 8, the top end portion 22B1 of the lip ring 22 is shown having two bends, it may include, for example, three or four bends. Increasing the number of bends included in the top end portion 22B1, however, decreases the rigidity of the top end portion 22B1 to shorten the life of the lip ring 22, so that the number of bends included in the top end portion 22B1 is preferably in a range of two to four.

Third Embodiment

A reciprocating compressor according to a third embodiment of the present invention will be described below with reference to FIGS. 9 and 10. Parts identical to those described above in connection with the first and second embodiments will be denoted by identical reference numerals as used above and their description will be omitted.

In the third embodiment, the lip ring 22 has a curved portion, denoted as R1 in FIG. 9, on the inner peripheral surface between the bottom portion 22A and the side portion 22B. Compared with the first embodiment, in the third embodiment with the curved portion R1 provided on the inner peripheral surface between the bottom portion 22A and the side portion 22B, the stress applied to the inner peripheral surface between the bottom portion 22A and the side portion 22B where stress concentration tends to occur is further reduced.

Also, as shown in FIG. 10, providing a curved portion R2 on the inner peripheral surface of the bent portion 22B3 included in the side portion 22B of the lip ring 22 can further decrease, as compared with the first embodiment, the stress applied to the inner peripheral surface of the bent portion 22B3 where stress concentration tends to occur.

The foregoing embodiments each represent a mere example of application of the present invention, and they do not define the technical scope of the present invention. The present invention can be applied in various manners without departing from the technical concept and main features thereof. The first to the third embodiments described above may also be combined in implementing the present invention.

Claims

1. A reciprocating compressor, comprising: a piston which compresses air by, while rocking, reciprocatingly moving in a cylinder; anda sealing member which is fitted in a groove formed on the piston for sealing between the cylinder and the piston,wherein the sealing member has a bottom portion to be fitted in the groove formed on the piston and a side portion provided radially outwardly of the piston, andwherein the side portion includes a bent portion so as to reduce a gap between an upper end portion thereof and the piston.

2. The reciprocating compressor according to claim 1, wherein an angle formed between a base end side of the side portion and the axial direction of the piston is larger than a rocking angle of the piston.

3. The reciprocating compressor according to claim 1, wherein the bottom portion of the sealing member is prevented from moving outwardly of the groove formed on the piston.

4. The reciprocating compressor according to claim 1, wherein the side portion includes a plurality of bends.

5. The reciprocating compressor according to claim 1, wherein the bent portion of the sealing member has a curved inner side surface.

6. The reciprocating compressor according to claim 1, wherein an inner side surface between the side portion and the bottom portion is curved.

7. A reciprocating compressor comprising: a piston which compresses air by, while rocking, reciprocatingly moving in a cylinder; anda sealing member which is fitted in a groove formed on the piston for sealing between the cylinder and the piston,wherein the sealing member has a bottom portion to be fitted in the groove formed on the piston and a side portion provided radially outwardly of the piston, andwherein the side portion includes a plurality of bends causing a first angle formed between an upper end side of the side portion and the axial direction of the piston to be smaller than a second angle formed between a base end side of the side portion and the axial direction of the piston.

8. The reciprocating compressor according to claim 7, wherein the second angle formed between the base end side of the side portion and the axial direction of the piston is larger than a rocking angle of the piston.

9. The reciprocating compressor according to claim 7, wherein the bottom portion of the sealing member is prevented from moving outwardly of the groove formed on the piston.

10. The reciprocating compressor according to claim 7, wherein the plurality of bends have a curved inner side surface.

11. The reciprocating compressor according to claim 7, wherein an inner side surface between the side portion and the bottom portion is curved.