Gas compressor

Abstract

To provide a gas compressor capable of reducing leakage of compressed air in an abutment part of a piston ring.SOLUTION: A gas compressor comprises a cylinder, a piston that reciprocates while oscillating inside the cylinder to compress gas in a compression chamber, and a piston ring 149 provided on an outer periphery of the piston. The piston ring 149 has an inclined surface 149j on the compression chamber side of the outer periphery of the piston ring 149. The inclined surface 149j has an inclined surface region whose inclination angle with an axial core J1 of the piston ring 149 is larger than a maximum oscillation angle in a compression process of the piston.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a gas compressor.

Background Art

[0002] Reciprocating compressors are widely used as air compressors and compressors for refrigeration and air conditioning. By the way, in a reciprocating compressor, if the working fluid being compressed leaks from the working chamber to the crank chamber, the efficiency of the compressor decreases. Therefore, as a method of preventing the leakage of the working fluid from the gap between the piston and the cylinder, a method of providing a piston ring on the outer periphery of the piston and pressing the piston ring against the cylinder is known (see, for example, Patent Document 1). The piston ring has a joint portion, and the diameter of the piston ring is expanded at the joint portion for mounting on the piston.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a swing piston type reciprocating compressor, the piston swings. Therefore, there is a problem that at a specific swing angle, the joint portion of the piston ring is pressed against the inner peripheral surface of the cylinder, and the high-pressure air in the working chamber leaks to the crank chamber through the joint portion.

Means for Solving the Problems

[0005] A gas compressor according to one aspect of the present invention includes a cylinder, a piston that reciprocates while oscillating inside the cylinder and compresses the gas in the cylinder compression chamber, and a piston ring provided on the outer periphery of the piston. The piston ring has an inclined surface on the cylinder compression chamber side of the outer periphery of the piston ring, and the inclined surface has an inclined surface region where the inclination angle, which is the angle formed with the axis of the piston ring, is larger than the maximum oscillation angle in the compression process of the piston.

Effect of the Invention

[0006] According to the present invention, leakage of compressed gas at the joint of the piston ring can be reduced.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Mode for Carrying Out the Invention

[0008] Embodiments of the present invention will be described with reference to FIGS. 1 to 14. In addition, substantially the same or similar configurations are denoted by the same reference numerals, and the description may be omitted when the description is redundant.

[0009] FIG. 1 is a diagram showing the configuration of the gas compressor 1. The gas compressor 1 includes a compressor main body 10 that compresses a gas (for example, air), an electric motor 2 that drives the compressor main body 10, and a tank 3 that stores the gas discharged from the compressor main body 10.

[0010] The compressor main body 10 and the electric motor 2 are installed on the tank 3. A compressor pulley 4 is fixed to a crankshaft (not shown) provided in the compressor main body 10. An electric motor pulley 5 is fixed to the rotating shaft of the electric motor 2. A transmission belt 6 is wound around the compressor pulley 4 and the electric motor pulley 5. When the electric motor 2 is rotationally driven and the electric motor pulley 5 rotates, the compressor pulley 4 is rotationally driven and the crankshaft of the compressor main body 10 rotates. As a result, a gas compression operation by the compressor main body 10 is performed. The compressed gas is discharged from the exhaust chamber in the cylinder head 113 provided at the top of the cylinder 110 to the tank 3 through the pipe 7.

[0011] FIG. 2 is a diagram showing a schematic configuration of the compressor main body 10. The compressor main body 10 includes a crankshaft 160, a cylinder 110, a piston 104 that reciprocates within the cylinder 110, and a connecting rod 102 that connects the crankshaft 160 and the piston 104. The cylinder main body 111 is connected to the crankcase 109, and a crank chamber 109a formed by the crankcase 109 communicates with the inside of the cylinder main body 111. A breathing hole 109b that connects the crank chamber 109a and the outside of the crankcase 109 is formed in the crankcase 109.

[0012] The crankshaft 160 connected to the compressor pulley 4 described above includes a crank journal 161, a crank pin 162, a crank weight 163, and a crank arm 164. The crank journal 161 is rotatably supported by the crankcase 109. The crankshaft 160 rotates about the axis Cs of the crank journal 161 as the center of rotation. A crank pin 162 connected to the connecting rod 102 is provided at one end of the crank arm 164 provided on the crank journal 161.

[0013] When the crankshaft rotates about the axis Cs of the crank journal 161, the axis Cb of the crank pin 162 moves on a circular locus P. For example, when the crankshaft 160 rotates counterclockwise, the axis Cb of the crank pin 162 moves counterclockwise on the circular locus P. As a result, the piston 104 fixed to the tip of the connecting rod 102 reciprocates while swinging within the cylinder main body 111. That is, the piston 104 is a swinging type piston that reciprocates while swinging within the cylinder integrally with the connecting rod 102. Note that the position of the axis Cs of the crank journal 161 is offset by an offset amount δ to the left side in the drawing with respect to the axis Cc of the cylinder main body 111.

[0014] A compression reaction force based on the gas pressure in the compression chamber 119 (see FIG. 2) is applied to the proximal end portion 121 of the connecting rod 102. For this reason, mechanical strength is required for the proximal end portion 121 of the connecting rod 102. Examples of materials with high mechanical strength include metallic materials such as iron-based materials and aluminum-based materials.

[0015] FIG. 3 is a diagram showing the configurations of the piston 104 and the connecting rod 102. The connecting rod 102 includes a cylindrical proximal end portion 121, a hemispherical distal end portion 129, and a straight rod portion 120 that connects the proximal end portion 121 and the distal end portion 129. The spherical side of the distal end portion 129 is connected to the straight rod portion 120, and the piston 104 is fixed to the planar side. Note that for fixing the piston 104 and the distal end portion 129, bolt fastening, welding, press fitting, etc. are used.

[0016] A bearing 128 is provided at the proximal end portion 121 of the connecting rod 102. A rolling bearing, a sliding bearing, etc. are used for the bearing 128. The crank pin 162 is fixed to the inner ring of the bearing 128. The axis of the bearing 128 provided at the proximal end portion 121 is orthogonal to the plane of FIG. 3 and is disposed on the axis C1 of the connecting rod 102. The piston 104 has a piston body 140 and a piston ring 149. The piston ring 149 is fitted into an annular groove 141 formed on the outer periphery of the piston body 140. Details of the piston 104 will be described later.

[0017] Returning to FIG. 2, the cylinder 110 will be described. The cylinder 110 includes a cylindrical cylinder body 111, a valve plate 112, and a cylinder head 113. The cylinder 110 is fixed to the crankcase 109. The valve plate 112 provided so as to close the upper opening end portion of the cylinder body 111 is sandwiched between the cylinder body 111 and the cylinder head 113. When the crankshaft 160 rotates, the piston 104 fixed to the tip of the connecting rod 102 connected by the crank pin 162 reciprocates while swinging within the cylinder body 111.

[0018] Inside the cylinder body 111, a compression chamber 119 is formed by the piston 104, the cylinder body 111, and the valve plate 112. In the cylinder head 113, an intake chamber 113a and an exhaust chamber 113b are formed. The intake chamber 113a communicates with the compression chamber 119 formed in the cylinder body 111 through an intake hole 112a formed in the valve plate 112. On the other hand, the exhaust chamber 113b communicates with the compression chamber 119 formed in the cylinder body 111 through a discharge hole 112b formed in the valve plate 112.

[0019] A reed valve type intake valve 112c and a discharge valve 112d are attached to the valve plate 112. The intake valve 112c is provided facing the opening on the compression chamber 119 side of the intake hole 112a and closes the intake hole 112a. The discharge valve 112d is provided facing the opening on the exhaust chamber 113b side of the discharge hole 112b and closes the discharge hole 112b.

[0020] When the piston 104 moves downward in the cylinder 110 as shown in the figure, the gas in the compression chamber 119 expands and the pressure in the compression chamber 119 becomes lower than the pressure in the intake chamber 113a. Then, due to the differential pressure between them, the intake valve 112c opens. As a result, the gas in the intake chamber 113a flows into the compression chamber 119 through the intake hole 112a. Conversely, when the piston 104 moves upward in the cylinder 110 as shown in the figure, the gas in the compression chamber 119 is compressed and the pressure in the compression chamber 119 becomes higher than the pressure in the exhaust chamber 113b. Then, due to the differential pressure between them, the discharge valve 112d opens. As a result, the gas in the compression chamber 119 flows into the exhaust chamber 113b through the discharge hole 112b.

[0021] FIG. 4 is a diagram for explaining the relationship between the crank angle α of the crankshaft 160 and the state of the piston 104. In FIG. 4, state (a) shows the case where the crank angle α is 0 degrees, state (b) shows the case where α = 90 degrees, state (c) shows the case where α = 180 degrees, state (d) shows the case where α = 270 degrees, and state (e) shows the case where α = 360 degrees. The piston 104 reaches the top dead center in states (a) and (e), and reaches the bottom dead center in state (c). The period from state (a) to state (c) is the intake process, and the period from state (c) to state (e) is the compression stroke.

[0022] In the intake process where the piston 104 moves from the top dead center to the bottom dead center, the gas in the compression chamber 119 expands, and the pressure in the compression chamber 119 becomes lower than the pressures on the intake chamber 113a (see FIG. 2) and the crank chamber 109a sides. As a result, the intake valve 112c opens, and the gas in the intake chamber 113a is sucked into the compression chamber 119. At the same time, the gas on the crank chamber 109a side is sucked into the compression chamber 119 through the gap between the piston 104 and the cylinder 110. In the compression process where the piston 104 moves from the bottom dead center to the top dead center, the gas in the compression chamber 119 is compressed and discharged from the discharge valve 112d.

[0023] In the example shown in FIG. 2, the rotation center of the crankshaft 160 (i.e., the axis Cs of the crank journal 161) is offset to the left side in the drawing with respect to the axis Cc (y-axis) of the cylinder body 111. On the other hand, in FIG. 4, the case where the offset amount δ is 0 is shown as an example for simplicity of explanation.

[0024] It is assumed that the crankshaft 160 is rotationally driven counterclockwise in FIG. 2. In FIG. 4, for convenience of explanation, the four regions divided by the x-axis and y-axis passing through the crank journal 161 are defined as the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant. The y-axis coincides with the axis of the cylinder body 111.

[0025] In state (a) where the crank angle α is 0 degrees, the crank pin 162 is located on the plus side axis of the y-axis, and the piston 104 is located at the top dead center. In state (a), the piston 104 and the piston ring 149 are in a horizontal state.

[0026] When the crankshaft 160 rotates counterclockwise and the crank angle α increases from 0 degrees, the crank pin 162 moves from above the y-axis to the second quadrant, and the volume of the compression chamber 119 increases. The piston 104 fixed to the tip of the connecting rod 102 is restricted by the inner wall of the cylinder body 111 from moving in a direction perpendicular to the axis of the cylinder body 111. Therefore, when the crank pin 162 moves to the second quadrant, the piston 104 swings so that the right side of the piston 104 in the drawing tilts downward in the drawing (in the direction of the crank chamber 109a in FIG. 2).

[0027] When the crank angle α reaches 90 degrees (state (b)), the crank pin 162 is located on the negative side of the x-axis, and the swing angle is the largest in the intake process. Here, the swing angle β at the crank angle α is represented as β(α). That is, the swing angle in state (b) is represented as β(90). The swing center C0 is located approximately at the center of the piston 104. The swing angle when the connecting rod 102 swings to the right side of the swing center C0 as in state (d) is taken as positive, and conversely, the swing angle when it swings to the left side as in state (b) is taken as negative. That is, β(90) < 0.

[0028] When the crank angle α reaches 180 degrees (state (c)), the position of the crank pin 162 is on the y-axis, and the swing angle β(180) becomes 0 degrees. Note that β(180) represents the swing angle when the crank angle is 180 degrees. The piston 104 reaches the bottom dead center position, and the piston 104 and the piston ring 149 are in a horizontal state. When the crank angle α exceeds 180 degrees, the reduction of the volume of the compression chamber 119 starts, and the gas in the compression chamber 119 is compressed.

[0029] When the crank angle α reaches 270 degrees to reach state (d), the crank pin 162 is located on the positive side of the x-axis, and the swing angle β becomes the largest in the compression process. Since the connecting rod 102 swings so as to swing to the right side in the drawing with respect to the swing center C0, β(270) > 0. In the example shown in FIG. 4, since the offset amount δ of the axis of the crank journal 161 with respect to the axis (y-axis) of the cylinder body 111 is 0, the relationship of β(270) = -β(90) holds.

[0030] When the crank angle α reaches 360 degrees to reach state (e), the piston 104 makes a round trip in the cylinder body 111 and returns to the top dead center, and the discharge of the compressed gas is completed.

[0031] FIG. 5 is a diagram schematically showing the relationship between the crank angle α and the swing angle β. In FIG. 5, the solid line L1 shows the case where the offset amount δ shown in FIG. 2 is not zero (the case of the configuration shown in FIG. 2), and the broken line L2 shows the case where the offset amount δ = 0 (the case of the configuration shown in FIG. 4). Here, the swing angle in the case of FIG. 2 will be represented as β1, and the swing angle in the case of FIG. 4 will be represented as β2.

[0032] In both the case of the solid line L1 where the offset amount δ is not zero (FIG. 2) and the case of the broken line L2 where it is zero (FIG. 4), the swing angles β1 and β2 are minimum when the crank angle α is 90 degrees and maximum when it is 270 degrees. That is, the absolute values |β1| and |β2| of the swing angles β1 and β2 are maximum when α = 90 degrees in the intake process and maximum when α = 270 degrees in the compression process. Also, the crank angles α at the top dead center and the bottom dead center are 0 degrees and 360 degrees for the top dead center and 180 degrees for the bottom dead center, whether the offset amount δ is zero or not.

[0033] On the other hand, the crank angles α at which the swing angles β1 and β2 become zero are α = 0 degrees in the case where the offset amount δ is zero (broken line L2), but are 180 degrees - α1 and 360 degrees - α1 in the case where the offset amount δ is not zero (solid line L1). Here, the angle α1 is the angle formed by the straight line passing through the axes Cc and Cb and the axis Cc when the axis Cb of the crank pin 162 is located on the axis Cc of the cylinder body 111 as shown in FIG. 2.

[0034] In the present embodiment, the piston ring 149 attached to the piston 104 has a characteristic shape, and having this shape produces a specific effect. First, regarding the shape and problems of the conventional piston ring, a comparative example shown in FIGS. 6 to 8 will be described with reference thereto.

[0035] FIG. 6 is an exploded perspective view showing the piston body 140 and the piston ring 249 in the comparative example. As described above, in the present embodiment, the shape of the piston ring 149 is different from the piston ring 249 shown in FIG. 6. The piston body 140 in FIG. 6 has the same shape as the piston body 140 shown in FIG. 3.

[0036] The piston body 140 is formed in a substantially disc shape, and an annular groove 141 for attaching the piston ring 249 is formed on the outer periphery of the piston body 140. As shown in FIG. 4, the piston 104 reciprocates while swinging within the cylinder body 111 in a state of being constrained by the inner peripheral surface of the cylinder with respect to movement in a direction orthogonal to the axis Cc of the cylinder body 111. Therefore, the piston body 140 is required to have a shape that can swing with respect to the cylindrical inner peripheral surface of the cylinder. The side peripheral surfaces 142a and 142b of the piston body 140 are formed in a spherical shape so as to reciprocate while smoothly swinging with respect to the cylindrical inner peripheral surface of the cylinder. For example, the side peripheral surfaces 142a and 142b are constituted by a part of a spherical surface centered on the swing center C0 in FIG. 4.

[0037] The piston body 140 is formed of a material having excellent solid lubricity. As an example of a material having excellent solid lubricity, there is a material in which a filler such as glass fiber is added to a fluororesin such as polytetrafluoroethylene to improve mechanical properties such as strength. By using a material having excellent solid lubricity for the piston body 140, it is possible to adopt a configuration that does not use lubricating oil. The configuration without using lubricating oil has the advantage that lubricating oil does not mix into the gas in the compression chamber 119. In the present embodiment, the piston ring 149 is formed of the same material as the piston body 140.

[0038] The piston ring 249 of the comparative example is a substantially C-shaped member having a rectangular cross section. Therefore, the outer surface 249d of the piston ring 249 forms a substantially cylindrical surface. The end portions 249a, 249b of the piston ring 249 are thin in thickness (axial dimension) and overlap each other. The total thickness of the end portions 249a, 249b is set to be equal to the thickness of the region other than the end portions 249a, 249b. Hereinafter, the region B of the end portions 249a, 249b that overlap each other will be referred to as the joint portion 249c.

[0039] FIG. 7 is an enlarged view of a portion of the joint portion 249c of the piston ring 249. In the joint portion 249c, a horizontal seal portion 249f where both end portions 249a, 249b overlap, and gap regions 249e, 249g where the end portions 249a, 249b at both ends of the horizontal seal portion 249f do not overlap are formed. Hereinafter, the gap regions 249e, 249g will be referred to as joint gaps 249e, 249g. The upper edge 249i of the outer surface 249d of the piston ring 249 is interrupted at the portion of the gap region 249e. Similarly, the lower edge 249m of the outer surface 249d is interrupted at the portion of the gap region 249e.

[0040] By shifting the end portions 249a, 249b in the circumferential direction at the joint portion 249c, the diameter of the piston ring 249 can be changed. When the piston 104 with the piston ring 249 mounted is inserted into the cylinder, the piston ring 249 in the natural state is elastically deformed so that its outer diameter is smaller than the cylinder inner diameter dimension and then inserted.

[0041] When the axial direction of the piston ring 249 coincides with the axial direction of the cylinder body 111, the entire outer surface 249d of the piston ring 249 is in close contact with the inner peripheral surface of the cylinder. Since the upper surface side of the piston 104 faces the compression chamber 119, the end portion 249a is pressed against the end portion 249b by the pressure of the compressed gas in the compression chamber, and is in close contact with the end portion 249b at the horizontal seal portion 249f. Therefore, even if there are gap regions 249e and 249g, the outer surface 249d of the piston ring 249 is in seamless close contact over the entire circumference of the inner peripheral surface of the cylinder, preventing gas leakage in the thickness direction of the piston ring 149.

[0042] However, as the piston body 140 swings, when the piston ring 249 is not only in a horizontal state but also tilted with respect to the inner peripheral surface of the cylinder, leakage occurs in the thickness direction of the piston ring 249. FIGS. 8 and 9 are schematic diagrams for explaining the leakage of compressed gas from the joint gap 249e of the piston ring 249. FIG. 8 shows the contact state between the piston ring 249 and the inner peripheral surface of the cylinder when the piston 104 is in the state (d) of FIG. 4, that is, when the crank angle α is 270 degrees and the absolute value of the swing angle β in the compression process is the largest.

[0043] In FIG. 8, the piston body 140 is tilted so that the left side in the drawing goes down. The coordinate axes x, y, and z in FIG. 8 are set in the same manner as in the case of FIG. 4. As shown in FIG. 4, the piston 104 swings in the x direction within the xy plane. The z direction perpendicular to the paper surface is the direction perpendicular to the swing direction. Hereinafter, the minus direction of the x-axis in FIG. 8 is defined as one of the swing directions, and the plus direction of the x-axis is defined as the other swing direction. In the example shown in FIG. 8, the piston ring 249 is attached to the piston body 140 such that the joint gap 249e is located on the x-axis.

[0044] When the piston body 140 tilts as shown in Fig. 8, the piston ring 249 also tilts, and only the upper edge 249i of the outer surface 249d of the piston ring 249 comes into contact with the inner peripheral surface 111a of the cylinder. Fig. 9 is a view of the piston ring 249 and the inner peripheral surface 111a of the cylinder as seen from the +y-axis side (compression chamber side) in Fig. 8. Fig. 9 is a view showing the contact state between the piston ring 249 and the inner peripheral surface 111a at the joint portion 249c. The inner peripheral surface 111a of the cylinder is shown by a two-dot chain line.

[0045] As shown in Fig. 8, since the joint gap 249e faces the compression chamber side, when the joint gap 249e is viewed from the compression chamber side as shown in Fig. 9, an opening 250 surrounded by the joint gap 249e, the inner peripheral surface 111a of the cylinder, and the end portion 249b will be observed. Therefore, as shown by the broken-line arrow C in Fig. 8, the compressed gas in the compression chamber 119 leaks from the compression chamber side to the crank chamber side through the opening 250, which becomes a factor in reducing the discharged air volume of the gas compressor 1. The dimension G is the x-direction distance from the upper edge 249i of the outer surface 249d that contacts the inner peripheral surface 111a of the cylinder to the edge on the horizontal seal portion side of the end portion 249b.

[0046] Figs. 10 and 11 are diagrams for explaining the piston ring 149 in the present embodiment. Fig. 10 is a plan view of the piston ring 149 and is a view seen from the upper side in the axial direction of the piston ring 149. Fig. 11 is a side view of the piston ring 149 in Fig. 10 as seen from the -x-axis direction. In Fig. 10, the x-axis direction coincides with the rocking direction, and the z-axis direction is a direction perpendicular to the rocking direction. The joint portion 149c of the piston ring 149 is attached to the piston body 140 so as to be arranged on one side in the rocking direction. In the example shown in Fig. 10, the joint gap 149e of the joint portion 149c is arranged to be located on the x-axis.

[0047] In the circumferential region including the joint portion 149c of the piston ring 149, an inclined surface 149j is formed. The inclined surface 149j is formed in a range of an angle 2φ centered on one x-axis in the rocking direction (i.e., the center of the joint gap 149e). In the example shown in FIG. 10, φ is set to be larger than 90 degrees, and the range of the inclined surface 149j extends to the right side (the other side in the rocking direction) of the direction (z-axis) perpendicular to the rocking direction. The inclined surface 149j is formed so as to notch the upper end of the outer surface 149d. In the circumferential angular range 2φ of the piston ring 149, an inclined surface lower end edge 149k, which is the intersection line of the inclined surface 149j and the outer surface 149d, is formed. That is, the inclined surface lower end edge 149k also constitutes the upper end edge of the outer surface 149d notched by the inclined surface 149j.

[0048] Note that, on the outer surface 149d, the upper end edge 149i of the region not notched by the inclined surface 149j and the lower end edge 149m of the outer surface 149d have the same shape as the corresponding regions of the upper end edge 249i and the lower end edge 249m of the piston ring 249.

[0049] In the overlapping portion of the end portions 149a and 149b of the piston ring 149, a horizontal seal portion 149f is formed in the same manner as in the case of the piston ring 249. The inclined surface 149j is formed such that the inclined surface lower end edge 149k is located axially above the horizontal seal portion 149f. That is, the inclined surface 149j is formed to include the angular range in which the joint portion 149c is formed and not to intersect the horizontal seal portion 149f.

[0050] FIG. 12 is a diagram for explaining the shape of the inclined surface 149j. The illustration of the closing portion 149c is omitted. In FIG. 12, the axis J1 of the piston ring 149 coincides with the intersection (origin O) of the x-axis and the z-axis. The point indicated by the reference numeral J2 shows the machining center axis when machining the inclined surface 149j, and is set at a position shifted in the positive direction on the x-axis with respect to the axis J1. The region E sandwiched by the circular lines indicated by the two-dot chain lines L11 and L12 is the machining region. The inclined surface 149j is formed in the overlapping region (the region with the dashed line) between the machining region E and the piston ring 149 having a ring shape centered on the axis J1. The inclined surface 149j is formed deepest at a position that coincides with the x-axis in the circumferential direction (that is, in one of the rocking directions). The larger the displacement amount of the machining center axis J2 with respect to the axis J1, the smaller the circumferential range in which the inclined surface 149j is formed.

[0051] The shape of the machined surface has a shape obtained by cutting a conical surface centered on the machining center axis J2 in a ring shape. The surface shape of the inclined surface 149j is the same conical surface as the shape of the machined surface. Hereinafter, the angle θ2 between the generatrix of the conical surface and the machining center axis J2 will be referred to as the inclination of the conical surface. The generatrix of the conical surface is, for example, the intersection line between the plane including the machining center axis J2 and the radial R2 in FIG. 12 and the conical surface. Further, regarding the intersection line between the plane including the axis J1 of the piston ring 149 (for example, the plane including the axis J1 and the radial R1) and the inclined surface 149j, the angle formed by the intersection line and the axis J1 will be referred to as the inclination angle θ1 of the inclined surface 149j.

[0052] As can be seen from FIG. 12, since the xy plane includes the axis J1 and the machining center axis J2, the inclination angle θ1 of the inclined surface 149j at the x-axis position is equal to the inclination θ2 of the conical surface. However, at other circumferential positions of the inclined surface 149j, the inclination angle θ1 of the inclined surface 149j and the inclination θ2 of the conical surface are not equal, and θ1 > θ2.

[0053] FIG. 13 shows a cross-section of the piston ring 149 taken in a plane including the radial diameter R1 (referred to as the R1 cross-section) and a cross-section of the piston ring 149 taken in a plane including the radial diameter R2 (referred to as the R2 cross-section). The shape of the inclined surface 149j, which is a conical surface, on the cross-section is represented by an inclined line segment. The angle formed between the inclined surface 149j and the machining center axis J2 in the R2 cross-section coincides with the inclination θ2 of the conical surface. On the other hand, the angle θ1 (i.e., the inclination angle) formed between the inclined surface 149j and the axis J1 in the R1 cross-section satisfies θ1 > θ2.

[0054] FIG. 14 is a schematic diagram for explaining the leakage of compressed gas from the joint gap 149e when the piston ring 149 is used. Also in the case of FIG. 14, it is a view showing a cross-section in the same rocking state (the state (d) in FIG. 4) as that of FIG. 8 described above. That is, it shows a state where the crank angle α is 270 degrees and the absolute value of the rocking angle β in the compression process is the largest. Hereinafter, this rocking angle β(270) will be referred to as the maximum rocking angle βmax.

[0055] Since the inclined surface 149j is formed on the piston ring 149, in the state where the piston ring 149 is inclined as shown in FIG. 14, the lower edge 149k of the inclined surface comes into contact with the inner peripheral surface 111a of the cylinder. On the other hand, in the case of the piston ring 249 shown in FIG. 8, the upper edge 249i of the outer surface 249d comes into contact with the inner peripheral surface 111a of the cylinder. That is, in the case of the piston ring 149, a location closer to the horizontal seal portion 149f on the outer surface 149d comes into contact with the inner peripheral surface 111a of the cylinder as compared with the case of the piston ring 249 of the comparative example.

[0056] When using the piston ring 149, the x-direction dimension G1 of the leakage opening (the opening corresponding to the opening 250 in FIG. 9) caused by the joint gap 149e is the x-direction distance from the lower end edge 149k of the inclined surface to the horizontal seal portion 149f which is the upper end edge of the end portion 149b. On the other hand, the dimension G (see FIG. 8) when using the piston ring 249 is the x-direction distance from the upper end edge 249i of the outer surface 249d to the horizontal seal portion 249f. As a result, the relationship G > G1 holds. That is, by using the piston ring 149 instead of the piston ring 249, the leakage opening caused by the joint gap 149e can be made smaller. As a result, the leakage of the compressed gas from the joint gap 149e can be reduced, and a decrease in the discharged air volume of the gas compressor 1 can be suppressed.

[0057] Incidentally, the inclination angle θ1 of the inclined surface 149j of the piston ring 149 is set to an angle such that the inclined surface 149j does not contact the inner peripheral surface 111a of the cylinder when the piston body 140 swings. As shown in FIG. 14, the angle formed by the extension surface on the compression chamber side of the outer surface 149d of the piston ring 149 and the inclined surface 149j is equal to the inclination angle θ1. Also, in the swinging direction shown in FIG. 14, the angle formed by the outer surface 149d of the piston ring 149 and the inner peripheral surface 111a of the cylinder is equal to the maximum swing angle βmax of the piston body 140. In the outer peripheral direction position other than the swinging direction, the angle formed by the outer surface 149d and the inner peripheral surface 111a of the cylinder becomes smaller than the maximum swing angle βmax. Therefore, in order to prevent the inclined surface 149j from contacting the inner peripheral surface 111a of the cylinder, the inclined surface 149j may be formed such that the angle θ1 (= θ2) in the swinging direction of FIG. 14 satisfies θ1 > βmax.

[0058] Further, the inclined surface 149j is formed such that the lower edge 149k of the inclined surface is located above the horizontal seal portion 149f in the thickness direction. For example, in FIG. 14, if the inclined surface 149j is formed such that the lower edge 149k of the inclined surface is located below the horizontal seal portion 149f in the thickness direction, the pressing force acting on the horizontal seal portion 149f due to the pressure of the compressed gas disappears, and the compressed air in the compression chamber 119 may leak from the horizontal seal portion 149f toward the crank chamber side. Therefore, it is preferable that the inclined surface 149j is formed such that the lower edge 149k of the inclined surface is above the horizontal seal portion 149f in the thickness direction.

[0059] In addition, in the compression process in which the piston ring 149 tilts as shown in FIG. 14, on one side in the rocking direction, the lower edge 149k of the inclined surface is in contact with the inner peripheral surface 111a of the cylinder and performs a sealing function. On the other hand, on the other side in the rocking direction, the lower edge 149m of the outer surface 149d is in contact with the inner peripheral surface 111a of the cylinder. And in the direction orthogonal to the rocking direction, the contact position of the piston ring 149 with the inner peripheral surface 111a of the cylinder transitions from the lower edge 149k of the inclined surface to the lower edge 149m of the outer surface 149d. Therefore, in order to appropriately perform the transition from the lower edge 149k of the inclined surface to the lower edge 149m, it is preferable that the circumferential end portion of the inclined surface 149j is located on the other side in the rocking direction as shown in FIG. 10. As a result, the inclined surface 149j is formed only in a part (range of angle 2φ) in the circumferential direction.

[0060] (Modification example) FIG. 15 is a diagram showing a modification example of the above-described embodiment, and shows a piston body 140 with a piston ring 149 mounted therein in the modification example. Also in FIG. 15, as in FIG. 14, a cross section in the rocking state shown in state (d) of FIG. 4 is shown. In the piston ring 149 shown in FIGS. 10 and 11, the inclined surface 149j is a conical surface and the cross-sectional shape is a straight line (line segment). On the other hand, the inclined surface 149n of the piston ring 149 in the modification example is a convex curved surface on the outside and the cross-sectional shape is also composed of a convex curve on the outside. Other configurations of the piston ring 149 are the same as those of the piston ring 149 shown in FIGS. 10 and 11, and the description thereof is omitted.

[0061] Figure 16 is an enlarged view of the piston ring 149 and the inner peripheral surface 111a of the cylinder shown in Figure 15. As described above, the cross-sectional shape of the inclined surface 149n, which is a convex surface, is a curve convex outward. In the example shown in Figures 15 and 16, the inclined surface 149n is formed of a convex surface such that the cross-sectional curve is an arc. The radius of the arc is t2, and in the rocking direction shown in Figure 16, the inclined surface 149n is formed in the range of dimension t2 from the upper end of the end portion 149a having a thickness t1. The position indicated by point P1 is the lower end of the inclined surface 149n. The dimension t2 is set such that t2 < t1. That is, the inclined surface 149n is formed such that its lower end is on the upper side in the thickness direction from the horizontal seal portion 149f.

[0062] When the rocking angle β is β = 0, the outer surface 149d of the piston ring 149 is in contact with the inner peripheral surface 111a of the cylinder. As the magnitude of the rocking angle β increases from zero, the piston ring 149 begins to tilt, and the contact position between the inclined surface 149n and the inner peripheral surface 111a of the cylinder moves in the direction from P1 to P2. Then, as shown in Figure 16, when the rocking angle β reaches the maximum rocking angle βmax, the contact position between the inclined surface 149n and the inner peripheral surface 111a of the cylinder becomes the position indicated by point P2.

[0063] The inclination angle θ1 of the inclined surface 149n is the angle formed by the tangent plane of the inclined surface 149n, which is a convex surface, and the axis J1 of the piston ring 149 (see Figure 12). For example, it is the angle formed by the tangent of the arc, which is the cross-sectional curve in Figure 16, and the axis J1. The inclination angle θ1 is zero at point P1, increases as it approaches point P2 from point P1, and becomes the maximum rocking angle βmax at point P2. Further, as it approaches the upper end (the end portion on the compression chamber side) of the piston ring 149 from point P2, the inclination angle θ1 becomes even larger than the maximum rocking angle βmax.

[0064] Also in the case of a modified example in which the inclined surface 149n is a convex surface, the dimension G1 becomes smaller than the dimension G in the case of Figure 8. As a result, leakage of the compressed gas from the gap 149e can be reduced, and a decrease in the discharged air volume of the gas compressor 1 can be suppressed.

[0065] According to the above-described embodiments, the following operational effects are achieved.

[0066] (1) As shown in FIGS. 2, 9 to 13, 16, etc., the gas compressor 1 includes a cylinder 110, a piston 104 that reciprocates while oscillating inside the cylinder 110 and compresses the gas in the compression chamber (cylinder compression chamber) 119, and a piston ring 149 provided on the outer periphery of the piston 104. The piston ring 149 has an inclined surface 149j on the cylinder compression chamber side of the outer periphery of the piston ring 149, and the inclined surface 149j has an inclined surface region where the inclination angle θ1, which is the angle formed with the axis J1 of the piston ring 149, is larger than the maximum oscillation angle βmax in the compression process of the piston 104.

[0067] For example, in the case of the inclined surface 149j formed in the plane shown in FIG. 12, the inclination angle θ1 is θ1 > βmax in the entire region of the inclined surface 149j. Also, in the case of the inclined surface 149n formed of a convex curved surface shown in FIG. 16, the inclination angle θ1 on the compression chamber side from the point P2 in FIG. 16 is θ1 > βmax. In the piston ring 149 having such inclined surfaces 149j, 149n, by forming the joint portion 149c provided on one side in the oscillation direction within the inclined surface range, leakage of the compressed gas through the joint gap 149e provided on the compression chamber side of the joint portion 149c can be reduced. As a result, a decrease in the discharged air volume of the gas compressor 1 can be suppressed.

[0068] (2) In the above (1), as shown in FIGS. 11, 14, etc., the inclined surface 149j is provided on the compression chamber side with respect to the horizontal seal portion 149f, which is the overlapping surface of the joint portion 149c of the piston ring 149, in the thickness direction of the piston ring 149. By adopting such a configuration, the horizontal seal portion 149f will be located on the crank chamber side (see FIG. 14). As a result, the horizontal seal portion 149f is closely adhered by the pressure of the compressed gas on the compression chamber side, and leakage of the compressed gas in the horizontal seal portion 149f is prevented.

[0069] (3) In the above (1), as shown in FIG. 10 etc., the inclined surface 149j is provided in a range wider than a circumferential half turn (range of an angle 2φ) with respect to the circumferential position of the piston ring 149. Therefore, the circumferential formation region of the inclined surface 149j can also be arranged in a direction orthogonal to the rocking direction, and the sealing performance of the piston ring 149 in the direction orthogonal to the rocking direction can be ensured.

[0070] (4) In the above (1), as shown in FIGS. 10, 11, 14 etc., the inclined surface 149j is provided so as to include the side farther from the compression chamber 119 (the minus x-axis side in FIG. 10) among one side and the other side in the rocking direction with respect to the circumferential position of the piston ring 149. Since the joint portion 149c is provided on one side in the rocking direction, the inclined surface 149j is provided in the region of the joint portion 149c, and leakage of the compressed gas from the joint gap 149e can be reduced.

[0071] (5) In the above (1), as shown in FIGS. 10, 11 etc., the piston ring 149 includes the joint portion 149c in the circumferential range where the inclined surface 149j is provided. By providing the joint portion 149c in the circumferential range where the inclined surface 149j is formed, leakage of the compressed gas from the joint gap 149e can be reduced. In the example shown in FIG. 10, the joint portion 149c is arranged such that the joint gap 149e is on the x-axis, but it is not necessarily limited to this circumferential position. Even when the joint portion 149c is arranged at a position shifted in the clockwise direction or the counterclockwise direction from the position in FIG. 10, leakage from the joint gap 149e can be reduced.

[0072] (6) In the above (1), as shown in FIGS. 10 to 13 and the like, the inclined surface 149j is a conical surface formed in a predetermined circumferential range of the piston ring 149, and the inclination angle θ1 is preferably set to be larger than the maximum swing angle βmax at the center of the predetermined range and to increase as it approaches the end from the center of the predetermined range. By providing the closing portion 149c in the circumferential range of the inclined surface 149j configured in this way, leakage of the compressed gas in the closing gap 149e can be reduced. Also, like the inclined surface 149n shown in FIGS. 15 and 16, it may be a convex curved surface with a larger inclination angle on the side closer to the compression chamber (cylinder compression chamber) 119.

[0073] As described above, the embodiments of the present invention have been explained. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Explanation of Reference Numerals

[0074] 1... Gas compressor, 2... Electric motor, 10... Compressor main body, 102... Connecting rod, 104... Piston, 109... Crankcase, 109a... Crank chamber, 110... Cylinder, 111... Cylinder main body, 111a... Inner circumferential surface of cylinder, 112... Valve plate, 113... Cylinder head, 119... Compression chamber (cylinder compression chamber), 140... Piston main body, 141... Annular groove, 149, 249... Piston ring, 149a, 149b, 249a, 249b... Ends, 149c, 249c... Closing portions, 149d, 249d... Outer surfaces, 149e, 149g, 249e, 249g... Closing gaps, 149f, 249f... Horizontal seal portions, 149i, 249i... Upper end edges, 149j, 149n... Inclined surfaces, 149k... Lower end edge of inclined surface, 149m, 249m... Lower end edges, 160... Crankshaft, 250... Opening, J1... Axis, J2... Machining center axis, α... Crank angle, β, β(α)... Swing angle, β(270), βmax... Maximum swing angle, θ1... Inclination angle, θ2... Inclination of conical surface

Claims

1. A cylinder, A piston that reciprocates while oscillating inside the cylinder and compresses the gas in the cylinder compression chamber, And a piston ring provided on the outer periphery of the piston, The piston ring has an inclined surface on the cylinder compression chamber side of the outer periphery of the piston ring, The inclined surface has an inclined surface region where the inclination angle, which is the angle formed with the axis of the piston ring, is larger than the maximum oscillation angle in the compression process of the piston, a gas compressor.

2. In the gas compressor according to Claim 1, The inclined surface is provided on the cylinder compression chamber side rather than the horizontal seal portion, which is the overlapping surface of the joint portion of the piston ring, in the thickness direction of the piston ring, a gas compressor.

3. In the gas compressor according to Claim 1, The inclined surface is provided in a range wider than the circumferential half - circle with respect to the circumferential position of the piston ring, a gas compressor.

4. In the gas compressor according to Claim 1, The inclined surface is provided so as to include the side farther from the cylinder compression chamber in one side and the other side in the oscillation direction with respect to the circumferential position of the piston ring, a gas compressor.

5. In the gas compressor according to Claim 1, The piston ring includes a joint portion in the circumferential range where the inclined surface is provided, a gas compressor.

6. In the gas compressor according to Claim 1, The inclined surface is a conical surface formed in a predetermined circumferential range of the piston ring, The inclination angle is set to be larger than the maximum oscillation angle at the center of the predetermined range and to increase as it approaches the end from the center of the predetermined range, a gas compressor.

7. In the gas compressor according to claim 1, the inclined surface is a convex surface, and in the convex surface, the inclination angle increases as it gets closer to the cylinder compression chamber in the thickness direction of the piston ring. A gas compressor.

Images