Reciprocating compressor

Abstract

To provide a reciprocating compressor that can reduce wear of a piston and a piston ring, and has high reliability.SOLUTION: A reciprocating compressor 50 according to the present invention comprises: a cylinder 1 constituting a compression chamber 40; a piston 4 in proximity to or in sliding contact with a cylinder inner wall surface 1n, and for making reciprocating motion and oscillating motion; and a connecting rod 2 fixed to the piston 4, and connecting the piston 4 and a crankshaft 5. A piston ring 6 in sliding contact with the cylinder inner wall surface 1n is fitted to the piston 4. In the piston 4, at least surfaces 4c and 4d in proximity to the cylinder inner wall surface 1n have an approximately spherical shape. The piston ring 6 is located at a position where a center line 6o of a width dimension s1 thereof and a spherical center 4o of the piston 4 approximately coincide, and is arranged at a center βho of an oscillating range βh of the piston 4.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a reciprocating compressor. 【Background Art】 【0002】 Conventionally, among compressors that compress fluids, there is a reciprocating compressor in which a piston reciprocates linearly. Reciprocating compressors include the following normal piston type and rocking piston type. The normal piston type has a bearing provided at the end of the connecting rod on the compression chamber side, and a piston supported by the bearing so as to be able to swing. The rocking piston type does not have a bearing on the compression chamber side of the connecting rod, and a piston integrated with the connecting rod has a sealing ring that elastically deforms to seal the compressed fluid. 【0003】 The rocking piston type has a number of advantages compared to the normal piston type, such as a simpler structure due to not having bearings or piston pins, no design limitations due to bearing temperature, and the ability to reduce the mass that reciprocates. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2021-055647 (FIG. 2, FIG. 3B, paragraph 0024, etc.) 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 However, on the other hand, especially in compressors with a large stroke, the range of the angle (swing angle) by which the connecting rod tilts during one rotation of the crankshaft becomes large, causing problems such as wear of the piston due to contact between the piston and the cylinder, an increase in vibration, and a decrease in sealing performance. In the rocking piston type, these are generally regarded as problems. For example, in patent documents 1As shown, a technique is known in which the piston (33) top is spherical in shape to prevent excessive contact and deterioration of sealing performance due to oscillating motion. 【0006】 In Patent Document 1, a piston ring (37) is installed on the outer circumference of the piston (33) to improve the sealing performance between the piston (33) and the cylinder (22). Since the piston ring (37) is installed approximately perpendicular to the connecting rod shaft (32), at angular positions where the oscillation angle is large, the spherical piston (33), not the piston ring (37), makes line contact with the cylindrical cylinder (22). Therefore, the piston (33) must be made of a material that simultaneously satisfies both lubrication characteristics for friction reduction and strength characteristics for wear reduction. 【0007】 Furthermore, airtightness inside and outside the compression chamber must be maintained by sealing through line contact between the piston and cylinder. However, in Patent Document 1, the central axis of the cylinder (22) is offset from the rotational center of the crankshaft (24), resulting in a configuration that reduces the oscillation angle during the compression stroke. As a result, the oscillation angle becomes larger during the intake stroke, increasing the contact area of ​​the piston (33), which raises concerns about problems such as piston (33) wear. Therefore, it may be necessary to replace the piston (33) along with the piston ring (37) to ensure reliability. 【0008】 This invention was conceived in view of the above circumstances, and aims to provide a highly reliable reciprocating compressor that can reduce wear on the piston and piston rings. [Means for solving the problem] 【0009】 To solve the above problem, the reciprocating compressor of the present invention comprises a cylinder constituting a compression chamber and the CylinderThe device comprises a piston that reciprocates and oscillates in close proximity to or sliding contact with the inner wall of a cylinder, and a connecting rod fixed to the piston and connecting the piston to the crankshaft, wherein the piston is fitted with a piston ring that slides against the inner wall of the cylinder, the piston has a substantially spherical shape at least on the surface in close proximity to the cylinder, the piston ring is positioned such that the center line of its width dimension substantially coincides with the spherical center of the piston, and is positioned at the center of the piston's oscillating range. The cylinder is configured such that the central axis of the inner wall surface of the cylinder and the rotation axis of the crankshaft are offset, and the piston ring is mounted on the piston at an angle to a straight line perpendicular to the center line of the connecting rod such that the center line of the piston ring is located approximately in the middle of the oscillation range of the center line of the piston ring. It is. [Effects of the Invention] 【0010】 According to the present invention, it is possible to provide a highly reliable reciprocating compressor that can reduce wear on the piston and piston rings. [Brief explanation of the drawing] 【0011】 [Figure 1] A longitudinal cross-sectional view of the main part of an air compressor using a crank mechanism according to Embodiment 1 of the present invention. [Figure 2] A schematic diagram of the crankshaft, connecting rod, piston, and cylinder, showing the oscillation angle of the connecting rod during the compression stroke of an air compressor. [Figure 3] A perspective view of the piston of Embodiment 1. [Figure 4] A perspective view of the piston ring of Embodiment 1. [Figure 5] A schematic diagram of the crankshaft, connecting rod, piston, and cylinder, showing the oscillation angle of the connecting rod during the expansion stroke of an air compressor. [Figure 6] A schematic diagram of the piston and connecting rod of Embodiment 1. [Figure 7] A figure showing the time history change of the oscillation angle with respect to the crank angle in Embodiment 1. [Figure 8] A cross-sectional view of the cylinder section of an air compressor using a piston according to Embodiment 2 of the present invention. [Modes for carrying out the invention] 【0012】 The present invention relates to a reciprocating compressor in which a piston reciprocates within a cylinder. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same reference numerals are given to the same components, and the same description will not be repeated. 【0013】 <<Embodiment 1>> FIG. 1 shows a longitudinal sectional view of a main part of an air compressor 50 using a crank mechanism according to Embodiment 1 of the present invention. The air compressor 50 according to Embodiment 1 is a device that compresses air, which is a fluid. In the air compressor 50, a crankshaft 5 rotates by a driving source such as an electric motor (not shown). 【0014】 Crankshaft eccentric part 5a is connected to a large end portion 2b of one end portion of the connecting rod 2 via a large end bearing 9. Examples of the large end bearing 9 include a rolling bearing and a sliding bearing. The large end bearing 9 may be configured to be separate from the connecting rod 2 and the crankshaft 5, or may be configured to be integral. A piston 4 for compressing a fluid is joined to a small end portion 2e of the other end portion of the connecting rod 2. The piston 4 is composed of a member different from the connecting rod 2. 【0015】 The piston 4 is configured to reciprocate and oscillate within a cylindrical cylinder 1. In order for the piston 4 to smoothly reciprocate and oscillate within the cylindrical cylinder 1, the portion that is close to or in sliding contact with the inside of the cylindrical cylinder 1 has a substantially spherical shape. A compression chamber 40 in which the fluid is compressed is formed between the upper surface 4b of the leading edge of the piston 4 and the inner wall surface 1n of the cylindrical cylinder 1. 【0016】 When the crankshaft 5 rotates (arrow α11 in FIG. 1), the piston 4 reciprocates and oscillates within the cylinder 1 integrally with the connecting rod 2. By this series of operations, the compression chamber 40 in the cylinder 1 repeats expansion and compression and functions as a compressor. Expansion of compression chamber 40 、 As compression occurs, the volume inside the crankcase 3 also expands. 、 It compresses repeatedly. 、 The inside and outside of the crankcase 3 are connected by a shared structure. 【0017】 A cylinder head 7, which has a reed valve type intake valve 10 and a discharge valve (not shown) attached to one end face of the cylinder 1, is assembled to the cylinder 1. The cylinder head 7 has an intake port 7a It has a discharge port 7b and a suction port. 7a The nozzle draws in air from the fluid to be compressed, and the outlet 7b discharges the compressed air from the fluid. In accordance with the expansion and compression of the compression chamber 40, the intake valve 10 and the discharge valve (not shown) open and close. 、 Outside air is drawn in through the intake valve 10. 7a It passes through and is taken into the compression chamber 40. on the other hand 、 The compressed air in the compression chamber 40 is discharged through the discharge valve. 、 Discharge port 7b Go through The fluid is discharged from the compression chamber 40 into a discharge space (not shown) consisting of the cylinder head 7 and the head cover 8. 【0018】 When the crankshaft 5 rotates (arrow α11 in Figure 1), the piston 4 is confined within the cylinder 1, and therefore has a reciprocating motion component in the direction of the cylinder 1 axis (central axis 1a) and a rotational motion component around the center 5a1 of the crankshaft eccentric portion. At this time, the rotational center of the connecting rod's small end 2e. 2a If (see Figure 2) is kept at a constant position relative to the connecting rod 2, the ideal shape of the piston 4's outer surface will be spherical. 【0019】 Figure 2 shows the crankshaft 5 and connecting rod 2, representing the oscillation angle β of the connecting rod 2 during the compression stroke of the air compressor 50. 、 Piston 4 、 A schematic diagram of cylinder 1 is shown. On the other hand, the rotational center of the connecting rod small end 2e depends on the rotation angle θ of the crankshaft 5 (see Figure 2). 2a It is also possible to design it so that it moves. In that case, the outer shape of the piston 4 is not a sphere, but the center of rotational motion. 2a The shape changes from a spherical to a distorted shape as it moves. The external shape of the piston 4 can be arbitrarily designed according to the sliding characteristics and sealing characteristics between the piston 4 and the cylinder 1. 【0020】 <Piston 4 and piston ring 6> Figure 3 shows a perspective view of the piston 4 of Embodiment 1. Figure 4 shows a perspective view of the piston ring 6 of Embodiment 1. 【0021】 A circular piston ring 6 is fitted to the center of the piston 4 shown in Figure 1. The piston 4 shown in Figure 3 has an annular groove for fitting the piston ring 6 (see Figure 4). 4a It is formed. 【0022】 The outer surface 6g of the piston ring 6 shown in Figure 4 is approximately cylindrical. The outer diameter D1 of the piston ring 6 is 、 piston Ring 6 When installing on piston 4 、 While sliding smoothly inside cylinder 1 、 During compression, the airtightness of the compression chamber 40 inside the cylinder 1 is maintained. 、 The dimensional relationship with the inner diameter d1 of cylinder 1 (see Figure 1) is defined. 【0023】 The piston ring 6 shown in Figure 4 has a roughly C-shape that forms a roughly annular shape. The piston ring 6 has a gap that forms the end of the roughly C-shape. 6a It has. In its natural state, without any external force applied, the piston ring 6 has an outer diameter slightly larger than the inner diameter d1 of the cylinder 1 (see Figure 1). However, the piston ring 6 is positioned in the annular groove of the piston 4. 4a (See Figure 3) 、As shown in Figure 1, when inserted into cylinder 1, the reaction force (expansion force) due to the contraction and deformation of the piston ring 6 along the inner wall surface 1n of cylinder 1 causes the outer surface 6g of the piston ring 6 to press against the inner wall surface 1n of cylinder 1, resulting in a near-close seal. This maintains the airtightness of the compression chamber 40 formed by the inner wall surface 1n of cylinder 1, the piston ring 6, and the piston 4. 【0024】 by the way 、 When piston ring 6 is not installed on piston 4 、 The contact between the piston 4 and the cylinder 1 is a line contact because the piston 4 has a substantially spherical shape and the inner wall surface 1n of the cylinder 1 is a cylindrical surface. 【0025】 In response to this 、 When the piston ring 6 is mounted on the piston 4, the outer surface 6g of the piston ring 6 is substantially cylindrical, and the inner wall surface 1n of the cylinder 1 is also cylindrical, resulting in substantially surface contact. Therefore 、 By using a piston ring 6 with an outer surface 6g that is approximately cylindrical, the contact with the cylinder 1 becomes approximately surface contact, thus enabling the compression chamber 40 to have a structure with excellent sealing properties. 【0026】 <Piston 4 and connecting rod 2> In the structure of Embodiment 1 、 The gas pressure (air pressure) in the compression chamber 40 is mainly applied to the upper surface 4b of the piston 4 (see Figure 1). The force applied to the piston 4 is generally applied in the axial direction of the connecting rod 2, which is approximately perpendicular to the upper surface 4b of the piston 4. A portion of the gas pressure in the compression chamber 40 acts between the inner wall surface 1n of the cylinder 1 wall and the piston 4. Here, as shown in Figure 1, the portion where the piston 4 can slide against the inner wall surface 1n of the cylinder 1 wall is 、 Figure 3 shows the upper curved surface 4c and the lower curved surface 4d of the piston. 【0027】 If the piston 4 is configured not to use lubricating oil, it is possible to make the piston 4 out of a material with excellent solid lubricity. 、This has the advantage of preventing lubricating oil from mixing with the compressed gas (air) in the compression chamber 40. As an example of a material with excellent solid lubricity to be used for piston 4 、 Fluorine resins such as polytetrafluoroethylene 、 Materials incorporating fillers such as fiberglass can be considered to improve mechanical properties such as strength and toughness. 【0028】 on the other hand 、 The connecting rod 2 shown in Figure 1 is the part to which a compressive reaction force is applied due to the compressed fluid (air) based on the gas pressure in the compression chamber 40. 、 Mechanical strength is required. 、 The connecting rod 2 should preferably be made of a material with high mechanical strength. An example of a material with high mechanical strength is... 、 Metal materials such as iron-based materials and aluminum-based materials are possible candidates. In Embodiment 1, in order to achieve both the mechanical strength of the connecting rod 2 and the sliding characteristics of the piston 4 in an environment without lubricant, 、 The piston 4 and the connecting rod 2 are made of different materials. 【0029】 <Angle of oscillation of connecting rod 2 β> Figure 5 shows the crankshaft 5 and connecting rod 2, representing the oscillation angle β of the connecting rod 2 during the expansion stroke of the air compressor 50. 、 Piston 4 、 A schematic diagram of cylinder 1 is shown. Next, we will explain the oscillation angle β of the connecting rod 2. The oscillation angle β is the central axis 1a of the cylinder 1 of the connecting rod 2 (Figure 2). 、 This is the angle it makes with respect to (see Figure 5). In Embodiment 1, as shown in Figures 2 and 5, the crankshaft rotation axis 5b and the cylinder central axis 1a do not intersect. 、 It has a structure that is offset by an offset amount δ. By offsetting, in the compression process, Cylinder 1 This reduces the external force perpendicular to the reciprocating motion of piston 4, enabling smooth reciprocating motion of piston 4. 【0030】 In Figure 2, the crankshaft 5 rotates counterclockwise (arrow α11 in Figure 2). 、 Cylinder central axis 1a This is relative to the crankshaft rotation axis 5b. 、 Crankshaft eccentricity during the compression stroke (Figure 2) 5a It is offset by an offset amount δ to the side where it is located (right side of the page). Here 、 Connecting rod 2 and cylinder central axis 1a We focus on the oscillation angle β, which is the angle formed by the connecting rod 2 and the cylinder center axis during the piston 4's cycle. 1a The angle formed by these two factors changes. Cylinder central axis 1a When the crankshaft rotation axis 5b intersects (when there is no offset and the offset amount δ is 0) 、 The maximum oscillation angle during the compression stroke (state shown in Figure 2) and 、 Inhalation stroke ( The maximum oscillation angle is the same in the state shown in Figure 5. 【0031】 In response to this 、 In the case where an offset (offset amount δ) is provided as in this embodiment 1, 、 The oscillating motion between the compression stroke (Figure 2) and the expansion stroke (Figure 5) is as shown in Figures 2 and 5, along the cylinder's central axis. 1a It becomes asymmetrical with respect to the left and right. In the case of Embodiment 1 、 The maximum oscillation angle βc during the compression stroke, shown in Figure 2, is smaller than the maximum oscillation angle βs during the intake stroke, shown in Figure 5. 【0032】 In Embodiment 1, as shown in Figure 1, a piston ring 6 is attached to a piston 4 that performs an oscillating motion. The center 4o of the approximately spherical piston 4 lies on the center line 2o of the connecting rod 2. The center line 6o that bisects the width dimension s1 of the piston ring 6 passes through the center (spherical center) 4o of the approximately spherical piston 4. 【0033】 <Piston 4 and connecting rod 2> Figure 6 shows a schematic diagram of the piston 4 and connecting rod 2 of Embodiment 1. Let the straight line 2h be perpendicular to the center line 2o of the connecting rod 2. The piston ring 6 is mounted on the piston 4 such that it slides evenly against the inner wall surface 1n of the cylinder 1 relative to the center line 6o of the piston ring 6 while the connecting rod 2 is oscillating (between the compression stroke in Figure 2 and the expansion stroke in Figure 5). In other words, the annular groove of the piston 4 is inclined at an angle α with respect to the straight line 2h perpendicular to the center line 2o of the connecting rod 2. 4a (See Figure 3) The piston ring 6 is attached to the piston 4. In other words, the piston ring 6 is attached to the piston 4 with its center line 6o tilted at an angle α with respect to a straight line 2h perpendicular to the connecting rod 2 (center line 2o). 【0034】 If the oscillation range βh is defined as the center line 6o of the piston ring 6, then the piston ring 6 is tilted at an angle α with respect to a straight line 2h perpendicular to the center line 2o of the connecting rod 2 so that the center line 6o of the piston ring 6 is located in the middle or approximately middle of the oscillation range βh, and the piston ring 6 is positioned in the annular groove of the piston 4. 4a It is attached to (see Figure 3). As a result, the positional relationship between the piston 4 and the piston ring 6 during the compression process in Figure 2 and the expansion process in Figure 5 is as follows. 【0035】 While the connecting rod 2 oscillates (from the compression stroke in Figure 2 to the expansion stroke in Figure 5), the piston ring 6 slides (comes into contact with) the inner wall surface 1n of the cylinder 1 evenly with respect to the center line 6o of the piston ring 6. 【0036】 During the compression process shown in Figure 2, the maximum oscillation angle β = βc of the connecting rod 2 is observed. During the expansion process shown in Figure 5, the maximum oscillation angle β = βs of the connecting rod 2. Since the piston ring 6 is fixed to the piston 4, it oscillates together with the piston 4 relative to the cylinder 1. 【0037】 <Time history change of oscillation angle β with respect to crank angle θ> Figure 7 shows the cylinder 1 of the connecting rod 2. Cylinder Central axis 1a (Figure 2) 、This shows the time history change of the oscillation angle β, which is the angle it makes with respect to the crank angle θ (see Figure 5). The horizontal axis of the graph in Figure 7 represents the crank angle θ. 、 The vertical axis represents the oscillation angle β. The crank angle θ of the crankshaft 5 (see Figures 2 and 5) is defined as 0° (0 on the horizontal axis) when the connecting rod big end 2b is at its lowest point during the expansion stroke shown in Figure 5. 、 From there, the counterclockwise direction of crankshaft 5 is considered the positive direction. 【0038】 In Figure 5, the large end 2b of the connecting rod is aligned with the cylinder's central axis. 1a The oscillation angle β is assumed to be positive when it is located to the left of the position. As mentioned above 、 In Embodiment 1, the crankshaft rotation axis 5b and the cylinder central axis 1a And are offset by an offset amount δ. Therefore 、 Unlike the case without offset, the oscillating motion of connecting rod 2 is along the cylinder's central axis. 1a It becomes asymmetrical. 、 As shown in Figure 7, the time history change of the oscillation angle β is asymmetrical with respect to the horizontal axis (X-axis). 【0039】 In the case of Embodiment 1 、 As shown in Figure 2, the maximum oscillation angle βc during the compression stroke (the stroke in which the piston 4 moves from bottom dead center (maximum expansion) to top dead center (maximum compression)) is smaller than when the offset amount δ is 0. As a result, during compression when the pressure is highest, the cylinder 1 acting on the piston 4 Cylinder The force perpendicular to the central axis 1a and the force perpendicular to the reciprocating motion of the piston 4 are reduced. 【0040】 <Operation of piston 4 during the intake stroke> next 、 The operation during the inhalation stroke shown in Figure 5 will be explained. In the intake stroke when piston 4 descends, the offset is by an offset amount δ, as shown in Figure 7. 、The oscillation angle β becomes larger compared to the compression stroke. In the range of large oscillation angles β shown in Figure 5, a portion of the outer surface 6g of the piston ring 6 does not contact the inner wall surface 1n of the cylinder 1, while the outer surface 4g of the piston 4 contacts the inner wall surface 1n of the cylinder 1. 【0041】 When the outer surface 4g of the piston 4 comes into contact with the inner wall surface 1n of the cylinder 1, wear and material degradation are more likely to occur at the contact point of the piston 4. This can lead to a decrease in the reliability of the air compressor 50. Furthermore, because the piston ring 6 does not come into contact with the inner wall surface 1n of the cylinder 1, the flow rate of gas leaking from between the piston ring 6 and the inner wall surface 1n of the cylinder 1 increases, and the sealing characteristics deteriorate. Furthermore, changes in the contact state of the piston 4 can easily lead to vibration and noise. These problems become even more pronounced as the wear on the contact surface 1n of the cylinder 1 between the piston 4 and the cylinder 1 increases. 【0042】 <Relationship between the oscillation angle β of the connecting rod 2 and the angle α at which the piston ring 6 is installed> Figure 6 illustrates the relationship between the oscillation angle β and the angle α at which the piston ring 6 is positioned. To reduce wear on the piston 4, the area in contact between the outer surface 4g of the piston 4 and the inner wall surface 1n of the cylinder 1 should be minimized, and the outer surface of the piston ring 6 6g Increase the contact area. Therefore, in Embodiment 1, the piston ring 6 is the rotational center of the connecting rod small end 2e. 2a It is positioned so that it roughly coincides with the spherical center 4o of the piston 4. 【0043】 Furthermore, the piston ring 6 is positioned at an angle α, which is the piston ring mounting angle, from a plane 2h perpendicular to the central axis 2o of the connecting rod 2. The angle α is matched to the average oscillation angle βm shown in Figure 7. Therefore, the piston ring 6 is positioned approximately at the center of the contact area of ​​the outer surface 4g of the piston 4 due to the oscillating motion of the connecting rod 2 to which the piston 4 is fixed. As a result, the contact surface between the outer surface 4g of the piston 4 and the inner wall surface 1n of the cylinder 1 is reduced, and wear of the piston 4 is reduced. This prevents or suppresses an increase in the leakage of compressed gas from inside the cylinder 1. Therefore, good sealing characteristics are maintained, and an increase in vibration and noise can also be prevented or suppressed. 【0044】 While the air compressor 50 requires occasional replacement of the piston rings 6 depending on their condition, the frequency of piston replacement can be significantly extended. As described above, according to Embodiment 1 、 It is possible to provide an air compressor 50 with a highly reliable and efficient reciprocating mechanism. Furthermore, the maintainability of the air compressor 50 is improved, and maintenance costs can be reduced. The reciprocating mechanism of this embodiment 1 is applicable to the air compressor 50 and other equipment. 【0045】 <<Embodiment 2>> Figure 8 shows a cross-sectional view of the cylinder section of the air compressor 50 according to Embodiment 2 of the present invention, using the piston 4. In Embodiment 2, 、 Unlike Embodiment 1 shown in Figure 1, the height 26h of the piston ring 26 (size or range of the piston ring 26) is greater than or equal to the oscillation range βh of the piston 4. 【0046】 In Embodiment 2, 、 Components similar to those in Embodiment 1 are denoted by the same reference numerals, while different components are denoted by reference numerals in the 20s. In Embodiment 2, the piston ring 26 is positioned at the rotational center of the connecting rod small end 2e. 2a and piss It is positioned so that it roughly coincides with the spherical center 4o of ton 4. The piston ring 26 is positioned at an angle α, which is the average oscillation angle βm, from a plane perpendicular to the central axis 2o of the connecting rod 2, and the oscillation range of the piston 4 is specified so as not to exceed the range of the piston ring 26h (size). In other words, the oscillation range βh of the piston 4 is kept within the range of the piston ring 26h height 26h. 【0047】 Therefore, the contact area between the outer surface 4g of the piston 4 and the inner wall surface 1n of the cylinder 1 (see Figure 1) due to the oscillating motion of the connecting rod 2 to which the piston 4 is fixed is limited to the area of ​​the piston ring 6. Therefore, the outer surface 4g of the piston 4 no longer comes into contact with the inner wall surface 1n of the cylinder 1, and wear of the piston 4 does not occur. As a result, there is no need to replace the piston 4 as a maintenance part. 【0048】 Therefore, according to Embodiment 2 、 Highly reliable reciprocating mechanism with low maintenance costs ( It is possible to provide an air compressor 50 having a reciprocating mechanism. 【0049】 <<Other Embodiments>> 1. In the embodiments 1 and 2 described above, air was used as an example of the fluid, but other fluids may also be used. 【0050】 2. The present invention is not limited to the configurations of Embodiments 1 and 2 described above, and various modifications and specific forms are possible within the scope of the appended claims. [Explanation of Symbols] 【0051】 1 cylinder 1a Cylinder central axis (central axis of the inner wall surface of the cylinder) 1n Inner wall surface of the cylinder (inner wall surface of the cylinder) 2 connecting rod 2a Center of rotation of the small end of the connecting rod 4 pistons 4c Upper curved surface of the piston (proximity surface of the piston) 4d Lower surface of piston (proximity surface of piston) 4o The center of the approximately spherical shape of piston 4 (the spherical center of the piston) 5 Crankshaft 5b Crankshaft rotation axis (axis of rotation of the crankshaft) 6 piston rings 60 Piston ring width dimension centerline 26h Piston ring height (piston ring size) 40 Compression Chamber 50. Air compressor (reciprocating compressor) s1 Piston ring width dimension α Piston ring mounting angle β oscillation angle βh Piston oscillation range βho is the center of the piston's oscillation range. δ offset amount

Claims

[Claim 1] The cylinders that make up the compression chamber, A piston that moves in close proximity to or sliding contact with the inner wall surface of the cylinder and moves in a reciprocating and oscillating motion, The system includes a connecting rod fixed to the piston and connecting the piston and the crankshaft, The piston is fitted with a piston ring that slides against the inner wall surface of the cylinder. The piston has a substantially spherical shape at least on the surface in close proximity to the inner wall surface of the cylinder. The piston ring is positioned such that its centerline is approximately aligned with the spherical center of the piston, and is located at the center of the piston's oscillation range. The cylinder is configured in a position where the central axis of the inner wall surface of the cylinder and the rotation axis of the crankshaft are offset from each other. A reciprocating compressor in which the piston ring is mounted on the piston at an angle to a straight line perpendicular to the center line of the connecting rod, such that the center line of the piston ring is located approximately in the middle of the oscillation range of the center line of the piston ring. [Claim 2] The device comprises a cylinder constituting a compression chamber, a piston that slides against the inner wall surface of the cylinder and moves back and forth and oscillates, and a connecting rod fixed to the piston and connecting the piston and the crankshaft. The piston is fitted with a piston ring. The piston has at least a substantially spherical sliding surface, The central axis of the inner wall surface of the cylinder and the rotation axis of the crankshaft are offset from each other. A reciprocating compressor in which the piston ring is mounted on the piston at an angle to a straight line perpendicular to the center line of the connecting rod, such that the center line of the piston ring is located approximately in the middle of the oscillation range of the center line of the piston ring. [Claim 3] In the reciprocating compressor according to claim 1 or claim 2, A reciprocating compressor in which the oscillation range of the piston does not exceed the range of the piston ring.

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