compressor

Abstract

To provide a compressor capable of reducing blowby leaked from an abutment gap of a piston ring.SOLUTION: A compressor has: a piston 14 that has a piston ring groove 14b on an outer circumferential surface formed by a curved surface, and reciprocates while rocking within a cylinder 15; a piston ring 14c that is attached to the piston ring groove 14b, and slides on the inner peripheral surface of the cylinder 15; and a crankshaft 11 that reciprocates the piston 14 via a connecting rod 13. A center axis AX1 of the cylinder 15 is arranged at a position apart from a rotation axis AX2 of the crankshaft 11. The piston ring groove 14b is provided with a rotation stopper 14i for the piston ring 14c. In a compression step, abutment gaps 14hc, 14hd, 14he of the piston ring 14c are located on the side of an outer circumferential surface 14a of the piston 14 that is pressed against the inner circumferential surface of the cylinder 15.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a compressor.

Background Art

[0002] In recent years, with the acceleration of carbon neutrality, higher efficiency has been demanded in compressors. Particularly in reciprocating compressors using a rocking piston, reducing blow-by, which is the gas leaking from the compression chamber to the crank chamber side, has become an issue for higher efficiency. In Patent Document 1, blow-by is reduced by making the outer peripheral surface of the rocking piston a curved surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there is a risk that blow-by may leak from the gap between the piston rings mounted in the piston ring grooves of the piston, and there is room for improvement in the piston. An object of the present invention is to provide a compressor capable of reducing blow-by leaking from the gap between the piston rings.

Means for Solving the Problems

[0005] To achieve the above object, the present invention includes a piston having a piston ring groove on an outer peripheral surface formed by a curved surface and reciprocating while rocking in a cylinder, and a piston ring mounted in the piston ring groove and sliding on the inner peripheral surface of the cylinder The joint portion has a stepped joint with a step in the circumferential direction.The cylinder has a piston ring and a crankshaft that reciprocates the piston within the cylinder via a connecting rod, the central axis of the cylinder is positioned away from the axis of rotation of the crankshaft, and the piston ring groove is provided with a mechanism to prevent the piston ring from rotating. The gap portion of the piston ring is on the load side of the piston, which is the outer surface side of the piston that is pressed against the inner surface of the cylinder during the compression process in which the piston compresses the gas inside the cylinder. To be located. [Effects of the Invention]

[0006] According to the present invention, blow-by leaking from the gap between piston rings can be reduced. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0007] [Figure 1] This is a front view of a compressor according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view showing the configuration of the compressor body according to the first embodiment of the present invention. [Figure 3] This is a front view of a piston according to the first embodiment of the present invention. [Figure 4] This is a cross-sectional view of a piston according to the first embodiment of the present invention. [Figure 5] This is a plan view of a piston ring according to the first embodiment of the present invention. [Figure 6] This is a front view of a piston ring according to the first embodiment of the present invention. [Figure 7] This is a bottom view of a piston ring according to the first embodiment of the present invention. [Figure 8] This is a perspective view of a piston according to the first embodiment of the present invention. [Figure 9] Figure 8 is a schematic diagram of the AA section. [Figure 10] This is a partial cross-sectional perspective view showing the piston and cylinder in the compression process of a compressor body according to the first embodiment of the present invention. [Figure 11] This is a perspective view of a piston according to the first embodiment of the present invention. [Figure 12]It is a schematic cross-sectional view taken along line B-B of FIG. 11. [Figure 13] It is a plan view and a front view of a piston ring according to the third embodiment of the present invention. [Figure 14] It is a cross-sectional view and a longitudinal sectional view of a piston according to another embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, the configuration and operation of the compressor according to the first to third embodiments of the present invention will be described. In each figure, the same reference numerals indicate the same parts.

[0009] (First Embodiment) FIG. 1 is a front view of a compressor according to the first embodiment of the present invention. The compressor 10 according to the first embodiment of the present invention is a machine that compresses gas, and as shown in FIG. 1, it includes a compressor main body 1, an electric motor 2, a tank 3, an electric motor pulley 4, a compressor pulley 5, and a transmission belt 6.

[0010] The compressor main body 1 is a device that compresses the gas sucked from the outside and discharges it to the tank 3. Details will be described later. The electric motor 2 is a power source that rotates the output shaft by supplying current and drives the compressor main body 1 via the electric motor pulley 4, the compressor pulley 5, and the transmission belt 6.

[0011] The tank 3 is a container that stores the compressed gas discharged from the compressor main body 1, and has a high sealing property so that the compressed gas can be stored inside without leakage, and a strong structure that can withstand the high pressure of the compressed gas. The compressor main body 1 and the electric motor 2 are fixed on the tank 3.

[0012] The electric motor pulley 4 is a pulley attached to the output shaft of the electric motor 2. The compressor pulley 5 is a pulley attached to a crankshaft 11 (to be described later) of the compressor main body 1 and has a larger diameter than the electric motor pulley 4. The compressor pulley 5 is provided with blades for air-cooling the compressor main body 1.

[0013] The drive belt 6 is wound around the motor pulley 4 and the compressor pulley 5, and is a belt that transmits the rotational force of the shaft of the motor 2 to the crankshaft of the compressor body 1. The output shaft of the motor 2 and the crankshaft 11 of the compressor body 1 are arranged substantially parallel to each other, and the rotational force of the motor 2 is transmitted to the compressor body 1 by the motor pulley 4, the compressor pulley 5, and the drive belt 6.

[0014] FIG. 2 is a cross-sectional view showing the configuration of the compressor body 1 according to the first embodiment of the present invention. The compressor body 1 includes a crankshaft 11, a crankcase 12, a connecting rod 13, a piston 14, a cylinder 15, a valve plate 16, and a cylinder head 17.

[0015] The crankshaft 11 is a shaft for converting the rotational force of the motor 2 transmitted from the compressor pulley 5 via the connecting rod 13 into the reciprocating motion of the piston 14, and includes a main shaft 11a, a crank pin 11b, and a pair of counterweights 11c.

[0016] The main shaft 11a is provided at both ends of the crankshaft 11 and is a rotating shaft supported by the crankcase 12 via bearings. A compressor pulley 5 is attached to the main shaft 11a, and the main shaft 11a rotates together with the compressor pulley 5.

[0017] The crank pin 11b is a pin disposed parallel to the main shaft 11a between the pair of counterweights 11c. The large end portion 13a of the connecting rod 13 described later is attached to the crank pin 11b.

[0018] The pair of counterweights 11c are weights having a center of gravity on the opposite side of the crank pin 11b. The movement of the center of gravity generated by the reciprocating motion of the piston 14 described later is accommodated within an allowable range by the counterweights 11c, and the vibration of the compressor body 1 is suppressed.

[0019] The crankcase 12 is a component that covers the crankshaft 11, and a crank chamber 12a is formed inside the crankcase 12. The crankcase 12 is provided with support holes for supporting the main shaft 11a via bearings, and through holes for allowing the connecting rod 13 to protrude into the cylinder 15.

[0020] The connecting rod 13 is a component that connects the crankshaft 11 to the piston 14, which will be described later. As mentioned above, one end of the connecting rod 13, the big end 13a, is attached to the crankpin 11b. The other end of the connecting rod 13 is fixed to the piston 14. The connecting rod 13 converts the rotational motion of the crankshaft 11 into oscillating motion and transmits it to the piston 14.

[0021] The piston 14 is a component that reciprocates within the cylinder 15, drawing in and compressing gas. More details will be provided later.

[0022] The cylinder 15 is a metal tube that houses the piston 14. The cylinder 15 is assembled to the crankcase 12 so as to communicate with the crank chamber 12a, and the connecting rod 13 is inserted into it. In addition, multiple cooling fins 15a are provided on the outer circumferential wall of the end of the cylinder 15.

[0023] Furthermore, the central axis AX1 of the cylinder 15 is positioned away from the rotation axis AX2 of the crankshaft 11 in order to reduce the oscillation angle of the connecting rod 13 during the compression stroke.

[0024] The valve plate 16 is a plate that closes the other opening of the cylinder 15. The gap inside the cylinder 15 sandwiched between the valve plate 16 and the piston 14 forms a compression chamber 15b. The valve plate 16 is provided with an intake port and intake valve for drawing in gas, and an exhaust port and exhaust valve for expelling gas. A cylinder head 17 is also provided above the valve plate 16.

[0025] In the above description, the compressor 10 according to the first embodiment of the present invention is a single-cylinder compressor comprising a pair of pistons 14 and a cylinder 15. However, the present invention is not limited to this embodiment, and the compressor 10 according to the first embodiment can be a multi-cylinder compressor having multiple pairs of pistons 14 and cylinders 15 arranged in series or radially with respect to the crankshaft 11.

[0026] Furthermore, in the above-described embodiment, the compressor 10 transmits the rotational force of the electric motor 2 to the compressor body 1 via the electric motor pulley 4, the compressor pulley 5, and the transmission belt 6. However, the invention is not limited to this embodiment, and in the compressor 10 according to the first embodiment, the crankshaft 11 of the compressor body 1 and the shaft of the electric motor 2 may be arranged on the same straight line and joined using a coupling or other coupling device to transmit the rotational force of the electric motor 2 to the compressor body 1.

[0027] Figure 3 is a front view of the piston 14 according to the first embodiment of the present invention. Figure 4 is a cross-sectional view of the piston 14 according to the first embodiment of the present invention.

[0028] The piston 14 is an oscillating piston, fixed to the end of the connecting rod 13 by a screw 13b, and reciprocates while oscillating within the cylinder 15 as the crankshaft 11 rotates.

[0029] The outer circumferential surface 14a of the piston 14 is formed as a curved surface in order to maintain a predetermined gap between the oscillating piston 14 and the inner circumferential surface of the cylinder 15. Preferably, the outer circumferential surface 14a of the piston 14 is formed as a spherical surface with an outer diameter slightly smaller than the inner diameter of the cylinder 15.

[0030] Furthermore, a piston ring groove 14b is provided on the outer circumferential surface of the piston 14, and a piston ring 14c is fitted thereon. Preferably, the outer circumferential surface 14a of the piston 14 is made of resin to suppress blow-by.

[0031] As shown in Figure 4, the piston 14 comprises a piston insert 14d having a screw hole and a piston head 14e covering the piston insert 14d.

[0032] The piston insert 14d is a disc-shaped member made of a metal such as an aluminum alloy, and is fixed to the upper end of the connecting rod 13 by a screw 13b. A hollow portion 14f opening towards the connecting rod 13 is provided in the center of the lower surface of the piston insert 14d.

[0033] The hollow section 14f is located at the center of the upper end of the connecting rod 13 and communicates with the hollow section 13c, forming a hollow space 134. The hollow space 134 allows for weight reduction of the connecting rod 13 and piston 14, suppressing vibration, and also prevents the accumulation of compression heat inside the piston insert 14d and the connecting rod 13.

[0034] Furthermore, a flange portion 14g is provided on the side of the piston insert 14d.

[0035] The piston head 14e is made of resin that covers the upper surface and flange portion 14g of the piston insert 14d, and is molded, for example, by molding. Since the piston head 14e covers the flange portion 14g on the side of the piston insert 14d, it is possible to suppress the separation of the piston head 14e from the piston insert 14d due to the reciprocating motion of the piston 14.

[0036] The piston head 14e is formed from a wear-resistant resin, such as PTFE (polytetrafluoroethylene), PPS (polyphenylene sulfide), phenolic resin, polyimide resin, or Copna resin, or a mixture thereof.

[0037] As described above, the outer circumferential surface of the piston head 14e is provided with a piston ring groove 14b, which is an annular groove for mounting the piston ring groove 14b. The piston ring groove 14b is provided with an anti-rotation device that prevents the piston ring 14c from rotating circumferentially within the piston ring groove 14b.

[0038] Figure 5 is a plan view of the piston ring 14c according to the first embodiment of the present invention. Figure 6 is a front view of the piston ring 14c according to the first embodiment of the present invention. Figure 7 is a bottom view of the piston ring 14c according to the first embodiment of the present invention.

[0039] The piston ring 14c is an annular sliding material fitted into the piston ring groove 14b and in contact with the inner circumferential surface of the cylinder 15. It is made of a resin material with excellent wear resistance, such as PTFE (polytetrafluoroethylene: tetrafluoroethylene resin). As the piston 14 reciprocates, the piston ring 14c slides against the inner circumferential surface of the cylinder 15. The piston ring 14c seals the gap between the outer circumference of the piston 14 and the inner circumferential surface of the cylinder 15, thereby preventing compressed gas from leaking from the compression chamber 15b into the crankcase 12a.

[0040] As shown in Figures 5-7, the piston ring 14c is provided with a gap portion 14h, which is a cut in the piston ring 14c. The gap portion 14h allows the piston ring 14c to be fitted into the piston ring groove 14b of the piston 14 and to expand and contract while maintaining sealing performance.

[0041] The joint portion 14h in this embodiment is a so-called stepped joint, and has a leak-cut shape comprising two plate-like portions (first plate-like portion 14ha and second plate-like portion 14hb) that are separated in the axial direction on the compression chamber 15b side and the crank chamber 12a side, and are able to overlap and slide. In the joint portion 14h, a first joint gap 14hc is formed on the compression chamber 15b side, and a second joint gap 14hd and a third joint gap 14he are formed on the crank chamber 12a side.

[0042] As shown in Figure 5, the first joint gap 14hc is surrounded by the first circumferential end face 14hf of the first plate-like portion 14ha, the second end face 14hg facing the first end face 14hf, and the first side surface 14hh, which is the side surface of the second plate-like portion 14hb on the compression chamber 15b side, and opens radially to the compression chamber 15b side.

[0043] As shown in Figure 7, the second joint gap 14hd is surrounded by the third end face 14hi, which is the outer diameter end face of the second plate-like portion 14hb; the fourth end face 14hj, which is the circumferential outer diameter end face of the second plate-like portion 14hb; the fifth end face 14hk, which is opposite the fourth end face 14hj; and the second side surface 14hl, which is the side surface of the first plate-like portion 14ha on the crank chamber 12a side, and opens outward in the direction toward the crank chamber 12a.

[0044] As shown in Figure 7, the third joint gap 14he is surrounded by the sixth end face 14hm, which is the inner diameter end face in the circumferential direction of the second plate-like portion 14hb, the seventh end face 14hn, which is opposite to the sixth end face 14hm, the eighth end face 14ho, which is opposite to the third end face 14hi, and the second side surface 14hl, which is the side surface of the first plate-like portion 14ha on the crank chamber 12a side, and opens in the inner diameter direction toward the crank chamber 12a side.

[0045] The second joint gap 14hd and the third joint gap 14he are formed at different positions in the circumferential direction. Therefore, when compressed gas presses against the inner and outer circumferential surfaces of the piston ring 14c, the third end face 14hi and the eighth end face 14ho are pressed together, thereby suppressing blow-by generated between the second joint gap 14hd and the third joint gap 14he.

[0046] Figure 8 is a perspective view of a piston 14 according to a first embodiment of the present invention. As shown in Figure 8, an anti-rotation device 14i is provided in the gap (first gap 14hc) of the piston ring 14c. More specifically, the anti-rotation device 14i in this embodiment protrudes from the side wall of the piston ring groove 14b on the compression chamber 15b side and is provided in the recessed first gap 14hc formed in the gap portion 14h, which is the stepped joint of the piston ring 14c.

[0047] In the above example, an embodiment was shown in which the anti-rotation device 14i is provided in the first joint gap 14hc. However, the embodiment is not limited to this. For example, an anti-rotation device may be provided not only in the first joint gap 14hc but also in the second joint gap 14hd. This can further reduce blow-by leakage from the joint gap and improve sealing performance.

[0048] Figure 9 is a schematic cross-sectional view of AA in Figure 8. In Figure 9, the piston insert 14d and the piston head 14e are schematically shown as a single unit.

[0049] As shown in Figure 9, the thickness of the piston ring 14c is thinner than the width of the piston ring groove 14b. Therefore, the piston ring 14c can be fitted into the piston ring groove 14b.

[0050] The outer diameter of the piston ring 14c is larger than the outer diameter of the piston 14. Furthermore, the inner diameter of the piston ring 14c is larger than the outer diameter of the piston ring groove 14b, creating a gap between the inner surface of the piston ring 14c and the bottom surface of the piston ring groove 14b. Additionally, the piston ring 14c is provided with a gap that can be expanded and contracted.

[0051] Therefore, the piston ring 14c mounted on the piston 14 can be inserted into the cylinder 15 by reducing its diameter through the narrowing of the gap between the bottom surface of the piston ring 14c and the gap at the joint. In addition, as the compressed gas presses against the inner circumferential wall of the piston ring 14c, the outer diameter of the piston ring 14c inserted into the cylinder 15 expands, so the piston ring 14c is pressed against the inner circumferential surface of the cylinder 15 and can exert its sealing performance.

[0052] Furthermore, it is preferable that the radial width Y of the piston ring 14c is smaller than the depth X of the piston ring groove 14b. In this case, during the compression stroke, the load-side piston ring 14c is pressed against the inner circumferential surface of the cylinder 15 and housed in the piston ring groove 14b, and the outer circumferential surface of the piston 14 slides against the inner circumferential surface of the cylinder 15.

[0053] Figure 10 is a partial cross-sectional perspective view showing the piston 14 and cylinder 15 in the compression process of the compressor body 1 according to the first embodiment of the present invention.

[0054] The piston 14 is an oscillating piston that reciprocates while oscillating within the cylinder 15. Therefore, as shown in Figure 10, during the compression stroke, the central axis AX3 of the piston 14 is tilted with respect to the central axis AX1 of the cylinder 15, and the piston 14 tilts upward along the central axis AX3 as indicated by the arrow. As a result, during the compression stroke, the piston 14 is pressed against the inner surface of the cylinder 15 on the side that tilts upward along the central axis AX2.

[0055] The first joint gap 14hc to the third joint gap 14he are positioned on the outer circumferential side of the piston 14, which is pressed against the inner circumferential surface of the cylinder 15 during the compression stroke, by the anti-rotation device 14i provided in the piston ring groove 14b. That is, in this embodiment, the anti-rotation device 14i provided in the first joint gap 14hc is provided in the piston ring groove 14b on the outer circumferential side of the piston 14, which is pressed against the inner circumferential surface of the cylinder 15 during the compression stroke.

[0056] Next, the effects of the compressor 10 according to this embodiment will be described in detail.

[0057] [effect] In a comparative example compressor that does not have a piston ring anti-rotation device on the piston, the piston ring gradually rotates as the piston repeatedly reciprocates. Therefore, during the compression process, there is a risk that the gap at the piston joint will be located on the opposite side (non-load side) from the side (load side) where the piston 14 tilts and rises along the central axis AX2.

[0058] On the non-load side, the inner circumferential wall of the piston ring 14c is pressed by the compressed gas. Therefore, if the gap between the piston rings is located on the non-load side, the gap expands, and the amount of blow-by leaking out from the gap increases.

[0059] In this embodiment, the piston ring 14c is fixed by an anti-rotation device 14i such that the gap between the piston ring 14c (first gap 14hc to third gap 14he) is located on the outer circumferential surface 14a side of the piston 14 which is pressed against the inner circumferential surface of the cylinder 15 during the compression process. That is, the position of the gap between the piston rings is fixed on the load side.

[0060] When the gap between piston rings is fixed to the load side, during the compression process, the piston ring 14c is pressed against the inner circumferential surface of the cylinder 15 on the load side, and the diameter of the piston ring 14c on the load side is reduced, thus narrowing the gap between piston rings. Also, since there is no gap between piston rings on the non-load side, blow-by leakage from the non-load side is suppressed. Therefore, in the compressor 10 according to this embodiment, the gap between piston rings 14c is narrowed, so blow-by leakage from the gap between piston rings can be reduced.

[0061] Furthermore, in the compressor 10 according to this embodiment, it is preferable that the width Y of the piston ring 14c is smaller than the depth X of the piston ring groove 14b. If the width Y of the piston ring 14c is larger than the depth X of the piston ring groove 14b, the piston ring 14c will protrude from the piston ring groove 14b and come into contact with and slide against the inner circumferential surface of the cylinder 15. In this case, as described above, the gap between the piston rings is on the load side, so the gap between the piston rings is narrowed, and blow-by can be suppressed.

[0062] On the other hand, if the width Y of the piston ring 14c is smaller than the depth X of the piston ring groove 14b, the piston ring 14c, including the gap at the joint on the load side, is pressed against the inner circumferential surface of the cylinder 15 and housed within the piston ring groove 14b during the compression stroke. In this case, the outer circumferential surface 14a of the piston 14, formed by the piston head 14e made of resin, slides against the inner circumferential surface of the cylinder 15 during the compression stroke. This reduces blow-by leakage from the gap at the joint of the piston ring 14c.

[0063] Furthermore, in this embodiment, a rotation stopper 14i is provided in the gap (first gap 14hc) of the piston ring 14c. Therefore, the rotation of the piston ring 14c can be suppressed by utilizing the first gap 14hc of the piston ring 14c, thereby reducing costs. In addition, blow-by leakage from the gap of the piston ring 14c can be reduced.

[0064] Furthermore, in this embodiment, the joint portion 14h of the piston ring 14c is a stepped joint having a step in the circumferential direction of the piston ring. Therefore, the axial opening of the piston ring can be reduced, and blow-by can be suppressed.

[0065] Furthermore, the anti-rotation device 14i protrudes from the side of the piston ring groove 14b toward the first gap 14hc of the stepped joint and is fitted into the first gap 14hc. That is, the anti-rotation device 14i is provided in the recessed first gap 14hc formed in the joint portion 14h, which is the stepped joint of the piston ring 14c. Therefore, the rotation of the piston ring 14c can be suppressed by utilizing the first gap 14hc of the piston ring, thereby reducing costs. In addition, blow-by leakage from the first gap 14hc can be further reduced.

[0066] Furthermore, in the piston ring 14c according to this embodiment, a first joint gap 14hc is formed on the compression chamber 15b side, and a second joint gap 14hd and a third joint gap 14he are formed on the crank chamber 12a side.

[0067] As the piston 14 tilts and rises, the outer surface of the piston 14 that is pressed against the inner surface of the cylinder 15 during the compression stroke is on the compression chamber 15b side. The anti-rotation device 14i in this embodiment is provided in the first joint gap 14hc on the compression chamber 15b side. Therefore, blow-by can be reduced compared to a piston with anti-rotation devices provided in the second joint gap 14hd and the third joint gap 14he on the crankcase 12a side.

[0068] Furthermore, since the purpose of the anti-rotation device 14i is to restrict the position of the gap between the piston rings from moving in the circumferential direction of the piston ring groove 14b, it may also be provided in the second gap 14hd and the third gap 14he on the crankcase 12a side. In addition, anti-rotation devices may be provided in the first gap 14hc and the second gap 14hd to increase the surface area of ​​the piston 14 that slides along the inner circumferential surface of the piston 14, thereby improving sealing performance.

[0069] (Second Embodiment) Figure 11 is a perspective view of a piston according to a second embodiment of the present invention. Figure 12 is a schematic cross-sectional view of the BB of Figure 11. In Figure 12, the piston insert 14d and the piston head 14e are schematically shown as a single unit.

[0070] The difference between the piston 24 of this embodiment and the piston 14 of the first embodiment is the shape of the joint portion 24h of the piston ring 24c and the shape of the anti-rotation stopper 24i.

[0071] Specifically, the joint portion 24h in this embodiment is a so-called right-angle joint, with a straight-cut shape that separates the piston ring 24c radially, and the joint gap 24ha opens radially to the compression chamber 15b side and the crank chamber 12a side.

[0072] Furthermore, similar to the first embodiment, it is preferable that a rotation stopper 24i is provided in the gap 24ha of the piston ring 24c. The gap 24ha of the piston ring 24c is located on the outer circumferential surface side 24a of the piston 24 that is pressed against the inner circumferential surface of the cylinder 15 during the compression stroke, similar to the first embodiment.

[0073] In other words, the outer circumferential surface 14a of the piston 14 is formed of resin, and it is preferable that the outer circumferential surface on the load side of the piston 14 slides against the inner surface of the cylinder during the compression process.

[0074] Specifically, the anti-rotation support 24i is preferably a protrusion that extends from the bottom surface of the piston ring groove 24b to the outer surface 24a of the piston 24, separating the piston ring groove 24b in the circumferential direction. The anti-rotation support 24i is located between the gap 24ha of the piston ring 24c fitted in the piston ring groove 24b.

[0075] In other words, the piston 24 of this embodiment has a piston ring groove 24b formed on the outer circumference of the load side of the piston 24, leaving only θ° of the outer circumference, and the θ° portion serves as an anti-rotation device 24i.

[0076] [effect] In this embodiment, the joint portion 24h of the piston ring 24c is a so-called right-angle joint, and the piston ring 24c is cut in a straight-cut shape in the radial direction. Therefore, the processing of the piston ring 24c is easy, and costs can be reduced.

[0077] Furthermore, the anti-rotation support 24i is provided between the gaps of the piston ring 24c mounted in the piston ring groove 24b, and is a protrusion that extends from the bottom surface of the piston ring groove to the outer surface of the piston, separating the piston ring groove in the circumferential direction. Therefore, the anti-rotation support 24i, which is a protrusion of the piston 24, is provided in the gap 24ha of the piston ring 24c, and the anti-rotation support 24i slides against the inner surface of the cylinder 15, thereby suppressing the amount of blow-by leaking from the gap 24ha of the piston ring 24c.

[0078] When the outer surface of the piston ring 24c contacts the inner surface of the cylinder 15, the contact area switches from a line to a surface and then back to a line, resulting in discontinuous contact and room for improvement in sealing performance. In the piston 24 of this embodiment, the outer circumferential surface of the piston 24, which is provided with the protrusion 24i, contacts the inner surface of the cylinder 15 continuously, thus improving sealing performance.

[0079] Furthermore, since the gap 24ha of a right-angle joint, which is originally formed in a straight-cut shape, is wider than the gap of a stepped joint, a larger amount of blow-by leaks out from the gap of the stepped joint. However, in the piston 24 of this embodiment, the gap 24ha is located on the load side, narrowing the gap 24ha, and a rotation stopper 14i is provided in the gap 24ha, sliding against the inner circumferential surface of the cylinder 15, thereby reducing the amount of blow-by leaking from the gap 24ha. Note that if the width of the gap 24ha is increased, the piston ring 24c pressed against the inner circumferential surface of the cylinder 15 becomes smaller, making it impossible to narrow the gap 24ha, so it is preferable that the width of the gap 24ha be small.

[0080] (Third embodiment) Figure 13 shows a plan view and a front view of a piston ring 34c according to a third embodiment of the present invention. The difference between the piston ring 34c according to this embodiment and the piston ring 24c according to the second embodiment is that the piston ring 34c is provided with a ridge portion 34ca that makes line contact with the inner surface of the cylinder 15 and slides along the inner surface of the cylinder 15 along its entire circumference.

[0081] Specifically, in the piston ring 34c of this embodiment, the outer circumferential surface of the piston ring 34 is inclined with respect to the inner circumferential surface of the cylinder 15, and the protruding portion 34ca is formed by the edge of the outer circumferential surface of the piston ring 34c.

[0082] In other words, the outer diameter on the crank chamber 12a side is larger than the outer diameter on the compression chamber 15b side, and the outer peripheral end on the crank chamber 12a side makes line contact with the inner surface of the cylinder 15 and forms a protruding portion 34ca that slides along the inner surface of the cylinder 15.

[0083] The protruding portion is not limited to the shape described above. For example, a curved surface that protrudes toward the inner surface of the cylinder 15 may be provided on the outer circumference of the piston ring 34c to serve as the protruding portion.

[0084] [effect] In piston rings without the protruding portion 34ca, when switching from the compression stroke to the intake stroke, the portion of the piston ring that contacts the inner circumferential surface of the cylinder switches from the outer edge on the compression chamber 15b side to the side and then to the outer edge on the crankcase 12a side. As a result, blow-by may occur. Also, when the piston ring makes surface contact with the inner circumferential surface of the cylinder 15, the pressure is lower than when it makes line contact, which may reduce the sealing performance.

[0085] In this embodiment, the entire outer circumference of the piston ring 34c is provided with a ridge portion 34ca that makes line contact with the inner surface of the cylinder 15 and slides along the inner surface of the cylinder 15. Therefore, the sealing performance of the piston ring 34c can be improved, and the leakage of blow-by from the compression chamber 15b into the crankcase 12a can be suppressed.

[0086] Furthermore, in the piston ring 34c of this embodiment, the outer circumferential surface of the piston ring 34 is inclined with respect to the inner circumferential surface of the cylinder 15, and the ridge portion is formed by the large-diameter edge 34ca of the outer circumferential surface of the piston ring 34c. Therefore, the processing cost of the piston ring 34c can be reduced, the strength of the ridge portion can be improved, and the durability of the piston ring can be improved.

[0087] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0088] Furthermore, embodiments of the present invention may also be as follows. For example, as shown in Figure 14, a recess 44ca may be provided in the piston ring 44c in a portion different from the joint portion, and a rotation stopper 44i may be provided so as to protrude from the bottom surface of the piston ring groove 44b into the recess 44ca. In addition, the thickness of the rotation stopper 44i may be thinner than that of the piston ring 44c. [Explanation of symbols]

[0089] 1... Compressor body, 2... Electric motor, 3... Tank, 10... Compressor, 11... Crankshaft, 12... Crankcase, 12a... Crank chamber, 13... Connecting rod, 14, 24, 34... Piston, 14a, 24a... Outer surface, 14b, 24b, 44b... Piston ring groove, 14c, 24c, 34c, 44c... Piston ring, 14e... Piston head, 14h, 24h... Joint, 14ha... First plate-like part, 14hb... Second plate-like part, 14hc, 14hd, 14he, 24ha... Joint gap, 15... Cylinder, 15b... Compression chamber, 24ha... Joint gap, 24i... Protrusion, 34ca... Ridge (outer end), 44ca... Recess

Claims

1. A piston has a piston ring groove on its outer surface formed by a curved surface and reciprocates while oscillating within the cylinder, A piston ring is fitted into the piston ring groove, slides on the inner circumferential surface of the cylinder, and has a stepped joint portion with a step in the circumferential direction, The piston is reciprocated within the cylinder via a connecting rod and a crankshaft, The central axis of the cylinder is positioned at a distance from the rotation axis of the crankshaft. The piston ring groove is provided with a mechanism to prevent the piston ring from rotating. The gap portion of the piston ring is located on the load side of the piston, which is the outer surface side of the piston that is pressed against the inner surface of the cylinder during the compression process in which the piston compresses the gas inside the cylinder.

2. The compressor according to Claim 1, A gap is formed in the joint portion on the compression chamber side. The aforementioned gap is located on the load side of the piston, and is situated on the outer circumferential surface of the piston ring in a direction perpendicular to the rotation axis of the crankshaft.

3. A compressor according to claim 1, The outer surface of the piston is formed of resin. A compressor in which, during the compression process, the outer surface of the piston slides against the inner surface of the cylinder.

4. A compressor according to claim 1, A compressor in which a ridge is provided around the entire circumference of the piston ring, which makes line contact with the inner surface of the cylinder and slides along the inner surface of the cylinder.

5. The compressor according to claim 4, A compressor in which the outer circumferential surface of the piston ring is inclined with respect to the inner circumferential surface of the cylinder, and the protruding portion is formed by the edge of the outer circumferential surface of the piston ring.

6. A compressor according to claim 1, A compressor in which the anti-rotation device is provided in the gap between the piston rings.

7. The compressor according to claim 6, A compressor in which the gap of the piston ring is a recessed gap formed in a stepped gap having a step in the circumferential direction of the piston ring.

8. The compressor according to claim 3, A compressor in which the radial width of the piston ring is smaller than the depth of the piston ring groove.

Images