Gas compressor

Abstract

To improve the sealability of a piston ring.SOLUTION: A gas compressor includes a cylinder, a piston 104 for reciprocating while oscillating inside the cylinder, a piston ring 149 provided on the outer periphery of the piston 104, and a crank chamber in which a driving mechanism is provided for driving the piston 104, the piston ring 149 having an inclined face 149e on the crank chamber side of the outer periphery of the piston ring 149, the inclined face 149e having an inclined face region of which an inclination angle θ2 as an angle to the axial center of the piston ring 149 is larger than a maximum oscillation angle β(270) in a step of compressing the piston 104.SELECTED DRAWING: Figure 10

Description

[Technical field]

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

[0002] Reciprocating compressors are widely used as air compressors and compressors for refrigeration and air conditioning. However, in a reciprocating compressor, if the working fluid being compressed leaks from the working chamber to the crank chamber, the compressor efficiency decreases. Therefore, as a method for preventing leakage of the working fluid from the gap between the piston and the cylinder, a method is known in which a piston ring is provided on the outer periphery of the piston and the piston ring is pressed against the inner periphery of the cylinder by using the pressure of the working chamber (see Patent Document 1).

[0003] Also, among reciprocating compressors, there is known a swing piston type reciprocating compressor as described in Patent Document 2. In a swing piston type reciprocating compressor, a piston reciprocates in a cylinder while performing a swing motion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2015 / 098924 [Patent Document 2] JP 2006-152960 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a piston ring that utilizes the pressure of the working chamber as described in Patent Document 1 is applied to a swing-piston reciprocating compressor, the force pressing the piston ring against the inner surface of the cylinder when the piston swings becomes insufficient, which may cause a problem in sealing performance. [Means for solving the problem]

[0006] A gas compressor according to one aspect of the present invention includes a cylinder, a piston that reciprocates while oscillating inside the cylinder, a piston ring provided on the outer periphery of the piston, and a crank chamber in which a drive mechanism that drives the piston is provided, wherein the piston ring has an inclined surface on the crank chamber side of the outer periphery of the piston ring, and the inclined surface has an inclined surface region where an inclination angle between the outer periphery of the piston ring and an axis of the piston ring is larger than a maximum oscillation angle during the compression stroke of the piston. Effect of the Invention

[0007] According to the present invention, it is possible to improve the sealing performance of piston rings in a rocking piston type gas compressor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing a configuration of a gas compressor. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a compressor body. [Diagram 3] FIG. 2 illustrates a piston and connecting rod configuration. [Figure 4] FIG. 4 is a diagram illustrating the relationship between a crank angle and a state of a piston. [Diagram 5] FIG. 4 is a schematic diagram showing the relationship between a crank angle and a swing angle. [Figure 6] FIG. [Figure 7] FIG. 2 is a perspective view of a piston ring. [Figure 8] FIG. 4 is a plan view showing the lower surface side of the piston ring. [Figure 9A] 8 is a diagram showing a cross section perpendicular to the circumferential direction at a position A1 of the piston ring in FIG. 7. FIG. [Figure 9B] 8 is a view showing a cross section perpendicular to the circumferential direction at a position A4 of the piston ring in FIG. 7. FIG. [Figure 10] FIG. 4 is a schematic diagram for explaining gas pressure acting on a piston ring. [Figure 11]FIG. 11 is a schematic view of the piston ring shown in FIG. 10 as viewed from a direction along the axis of a connecting rod. [Figure 12] FIG. [Figure 13A] FIG. 9B is a diagram showing a case where θ2<β(270) is set in FIG. 9A, and shows the case where β=0. [Figure 13B] FIG. 9B is a diagram showing a case where θ2<β(270) is set in FIG. 9A, and shows the case where β=0. [Figure 14A] FIG. 11 is a cross-sectional view of a piston ring according to a second embodiment, showing a cross section taken at a position A1. [Figure 14B] FIG. 11 is a cross-sectional view of a piston ring according to a second embodiment, showing a cross section taken at a position A4. [Figure 15] FIG. 13 is a diagram illustrating the contact position between the piston ring and the inner circumferential surface of the cylinder at the maximum swing angle β (270). [Figure 16A] FIG. 13 is a diagram showing a comparative example in the second embodiment, showing a case where the oscillation angle β is 0<β<β(270). [Figure 16B] FIG. 13 is a diagram showing a comparative example in the second embodiment, showing a case where the oscillation angle β is β=β(270). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) A first embodiment of the present invention will be described with reference to Figures 1 to 13B. Note that the same reference numerals are used for substantially the same or similar configurations, and duplicated descriptions may be omitted.

[0010] 1 is a diagram showing the configuration of a gas compressor 1. Gas compressor 1 includes a compressor body 10 that compresses a gas (e.g., air), an electric motor 2 that drives the compressor body 10, and a tank 3 that stores the gas discharged by compressor body 10.

[0011] The compressor body 10 and the electric motor 2 are installed on the tank 3. A compressor pulley 4 is fixed to a crankshaft (shown in the attached drawing) provided on the compressor 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 driven to rotate and the electric motor pulley 5 rotates, the compressor pulley 4 is driven to rotate and the crankshaft of the compressor body 10 rotates. As a result, the compressor body 10 performs a gas compression operation. The compressed gas is discharged from an exhaust chamber in a cylinder head 113 provided at the top of the cylinder 110 through a pipe 7 to the tank 3.

[0012] 2 is a diagram showing a schematic configuration of the compressor body 10. The compressor body 10 includes a crankshaft 160, a cylinder 110, a piston 104 that reciprocates in the cylinder 110, and a connecting rod 102 that connects the crankshaft 160 and the piston 104. The cylinder body 111 is connected to a crankcase 109, and a crank chamber 109a formed by the crankcase 109 communicates with the inside of the cylinder body 111. The crankcase 109 is formed with a ventilation hole 109b that connects the crank chamber 109a with the outside of the crankcase 109.

[0013] The crankshaft 160 connected to the above-mentioned compressor pulley 4 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 an axis Cs of the crank journal 161. 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.

[0014] When the crankshaft rotates around 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 end of the connecting rod 102 reciprocates while oscillating within the cylinder body 111. In other words, the piston 104 is an oscillating piston that reciprocates while oscillating within the cylinder together with the connecting rod 102. The position of the axis Cs of the crank journal 161 is offset to the left in the figure by an offset amount δ with respect to the axis Cc of the cylinder body 111.

[0015] A compression reaction force based on the gas pressure in the compression chamber 119 (see FIG. 2) is applied to the base end 121 of the connecting rod 102. For this reason, mechanical strength is required for the base end 121 of the connecting rod 102. Examples of materials with high mechanical strength include metal materials such as iron-based materials and aluminum-based materials.

[0016] 3 is a diagram showing the configuration of piston 104 and connecting rod 102. Connecting rod 102 includes cylindrical base end 121, hemispherical tip end 129, and straight rod portion 120 connecting base end 121 and tip end 129. Tip end 129 has a spherical side connected to straight rod portion 120, and piston 104 is fixed to its flat side. Note that piston 104 and tip end 129 are fixed to each other by bolting, welding, press fitting, or the like.

[0017] A bearing 128 is provided at the base end 121 of the connecting rod 102. A rolling bearing, a plain bearing, or the like is used as the bearing 128. The crank pin 162 shown in FIG. 2 is fixed to the inner ring of the bearing 128. The axis of the bearing 128 provided at the base end 121 is perpendicular to the plane of the paper in 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 in an annular groove 141 formed on the outer periphery of the piston body 140. The piston 104 will be described in detail later.

[0018] Returning to FIG. 2, the cylinder 110 will be described. The cylinder 110 includes a cylindrical cylinder body 111 and a valve plate 112. The cylinder 110 is fixed to a crankcase 109. The valve plate 112, which is provided to close the upper open end of the cylinder body 111, is sandwiched between the cylinder body 111 and a cylinder head 113. When the crankshaft 160 rotates, the piston 104, which is fixed to the tip of the connecting rod 102 connected by a crank pin 162, reciprocates while swinging within the cylinder body 111.

[0019] A compression chamber 119 is formed in the cylinder body 111 by the piston 104, the cylinder body 111, and the valve plate 112. An intake chamber 113a and an exhaust chamber 113b are formed in the cylinder head 113. The intake chamber 113a communicates with the compression chamber 119 formed in the cylinder body 111 through a suction 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.

[0020] Reed-type suction valve 112c and discharge valve 112d are attached to valve plate 112. Suction valve 112c is provided opposite the opening of suction hole 112a on the compression chamber 119 side and closes suction hole 112a. Discharge valve 112d is provided opposite the opening of discharge hole 112b on the exhaust chamber 113b side and closes discharge hole 112b.

[0021] When the piston 104 moves downward in the cylinder 110, 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, and the intake valve 112c opens due to the pressure difference. 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, 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, and the discharge valve 112d opens due to the pressure difference. As a result, the gas in the compression chamber 119 flows into the exhaust chamber 113b through the discharge hole 112b.

[0022] Fig. 4 is a diagram illustrating 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 is at top dead center in states (a) and (e), and at bottom dead center in state (c). The period from state (a) to state (c) is the intake stroke, and the period from state (c) to state (e) is the compression stroke.

[0023] During the intake stroke in which the piston 104 moves from the top dead center to the bottom dead center, the gas in the compression chamber 119 expands, and the intake valve 112c opens to draw the gas into the compression chamber 119, while the gas on the crank chamber 109a side is drawn into the compression chamber 119 through the gap between the piston 104 and the cylinder 110. During the compression stroke in which 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.

[0024] In the example shown in Fig. 2, the center of rotation of the crankshaft 160 (i.e., the axis Cs of the crank journal 161) is offset to the left side in the figure with respect to the axis Cc (y-axis) of the cylinder body 111. On the other hand, in Fig. 4, for simplicity of explanation, an example is shown in which the offset amount δ is 0.

[0025] The crankshaft 160 is driven to rotate counterclockwise in Fig. 2. For convenience of explanation, in Fig. 4, four regions separated 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.

[0026] In the state (a) where the crank angle α is 0 degrees, the crank pin 162 is located on the positive side of the y-axis, and the piston 104 is located at the top dead center. In the state (a), the piston 104 and the piston ring 149 are in a horizontal state.

[0027] When the crankshaft 160 rotates counterclockwise and the crank angle α increases from 0 degrees, the crank pin 162 moves from the y-axis to the second quadrant, and the volume of the compression chamber 119 increases. The movement of the piston 104 fixed to the end of the connecting rod 102 in a direction perpendicular to the axis of the cylinder body 111 is restricted by the inner wall 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 figure tilts downward in the figure (toward the crank chamber 109a in FIG. 2).

[0028] 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 during the intake stroke. Here, the swing angle β at the crank angle α is expressed as β(α). That is, the swing angle in state (b) is expressed as β(90). The swing center C0 is located approximately in the center of the piston 104, and the swing angle when the connecting rod 102 swings to the right in the figure with respect to the swing center C0 as in state (d) is considered to be positive, and conversely, the swing angle when the connecting rod 102 swings to the left in the figure as in state (b) is considered to be negative. That is, β(90)<0.

[0029] When the crank angle α reaches 180 degrees (c), the position of the crank pin 162 is on the y-axis, and the oscillation angle β(180) is 0 degrees. Note that β(180) represents the oscillation 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 position. When the crank angle α exceeds 180 degrees, the volume of the compression chamber 119 starts to decrease, and the gas in the compression chamber 119 is compressed.

[0030] When the crank angle α reaches 270 degrees (d), the crank pin 162 is located on the positive side of the x-axis, and the swing angle β becomes the largest during the compression stroke. The connecting rod 102 swings to the right in the figure with respect to the swing center C0, so β(270)>0. In the example shown in Fig. 4, the offset amount δ of the axis of the crank journal 161 relative to the axis of the cylinder body 111 (y-axis) is 0, so the relationship β(270)=-β(90) holds.

[0031] When the crank angle α reaches 360 degrees, which is state (e), the piston 104 makes one reciprocating motion within the cylinder body 111 and returns to the top dead center, completing the discharge of the compressed gas.

[0032] Fig. 5 is a diagram showing a schematic relationship between the crank angle α and the oscillation angle β. In Fig. 5, the solid line L1 shows the case where the offset amount δ shown in Fig. 2 is not zero (in the case of the configuration shown in Fig. 2), and the dashed line L2 shows the case where the offset amount δ=0 (in the case of the configuration shown in Fig. 4). Here, the oscillation angle in Fig. 2 is represented as β1, and the oscillation angle in Fig. 4 is represented as β2.

[0033] Whether the offset amount δ is zero (Fig. 4) or not (Fig. 2), the oscillation angles β1 and β2 are minimum when the crank angle α is 90 degrees and maximum when it is 270 degrees. In other words, the absolute values ​​|β1| and |β2| of the oscillation angles β1 and β2 are maximum when α = 90 degrees during the intake stroke and maximum when α = 270 degrees during the compression stroke. Additionally, the crank angles α at which top dead center and bottom dead center occur are 0 degrees and 360 degrees, respectively, and 180 degrees, whether the offset amount δ is zero or not.

[0034] On the other hand, the crank angle α at which the oscillation angles β1 and β2 become zero is α=0 degrees when the offset amount δ is zero, but is 180 degrees-α1 and 360 degrees-α1 when the offset amount δ is not zero. Here, the angle α1 is the angle between the axis Cc and a straight line passing through the axes Cc and Cb when the axis Cb of the crank pin 162 is located on the axis Cc of the cylinder body 111 as shown in FIG.

[0035] 6 is an exploded perspective view of piston 104. Piston 104 is formed in a substantially disc shape, and an annular groove 141 in which piston ring 149 is fitted is formed on the outer periphery of piston 104. Piston ring 149 is a substantially C-shaped member and has abutment 149a where ends overlap one another. The range indicated by symbol B is the range of abutment 149a on the outer periphery side of the piston ring. As shown in FIG. 2, piston ring 149 functions as a seal member that seals between compression chamber 119 formed in the cylinder and a space on the crank chamber side.

[0036] As shown in Fig. 4, the piston 104 reciprocates while swinging within the cylinder body 111, while being restrained by the cylinder inner peripheral surface with respect to movement in a direction perpendicular to the axis Cc of the cylinder body 111. Therefore, the piston 104 is required to have a shape that allows it to swing relative to the cylindrical cylinder inner peripheral surface. The side peripheral surfaces 142a, 142b of the piston 104 are formed in a spherical shape so that the piston 104 smoothly swings and reciprocates relative to the cylindrical cylinder inner peripheral surface. For example, the side peripheral surfaces 142a, 142b are formed as parts of a sphere centered on the swing center C0 in Fig. 4.

[0037] In addition, as piston 104 oscillates, piston ring 149 is not only horizontal but also tilted with respect to the inner circumferential surface of the cylinder, so sufficient sealing performance is required even in such a tilted state. Therefore, piston ring 149 is shaped as described below to improve the airtightness of compression chamber 119 during the compression stroke.

[0038] In this embodiment, the piston body 140 of the piston 104 is formed of a material with excellent solid lubrication. One example of a material with excellent solid lubrication 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 with excellent solid lubrication for the piston body 140, it is possible to configure the piston without using lubricating oil. The configuration without using lubricating oil has the advantage that lubricating oil does not get mixed into the gas in the compression chamber 119. In this embodiment, the piston ring 149 is formed of the same material as the piston body 140.

[0039] The shape of piston ring 149 in the first embodiment will be described in detail with reference to Figs. 7 to 9B. Fig. 7 is a perspective view of piston ring 149. Fig. 7 shows piston ring 149 in the state (a) of Fig. 4, and coordinate axes x, y, and z are set in the same way as in Fig. 4. In piston ring 149 shown in Fig. 7, the direction along the x-axis is the oscillation direction of piston 104, and the direction along the z-axis is a direction perpendicular to the oscillation direction.

[0040] In the following, the negative direction of the x-axis in Figures 4 and 7 is defined as one of the rocking directions, and the positive direction of the x-axis is defined as the other of the rocking directions. In addition, in piston ring 149 in Figure 7, the region on the negative side of the x-axis is called one side of the rocking direction, and the region on the positive side of the x-axis is called the other side of the rocking direction. Furthermore, in piston ring 149 in Figure 7, the position corresponding to the positive side of the x-axis is called position A1, the position corresponding to the negative side of the x-axis is called position A2, the position corresponding to the positive side of the z-axis is called position A3, and the position corresponding to the negative side of the z-axis is called position A4.

[0041] As shown in FIG. 7, the abutment 149a is formed on one side in the rocking direction (the positive side of the x-axis) including the position A2 of the piston ring 149. The inner peripheral surface 149c of the piston ring 149 is a cylindrical curved surface perpendicular to the upper surface 149b1 of the piston ring 149. The outer peripheral side of the piston ring 149 is composed of a cylindrical outer peripheral surface 149d perpendicular to the upper surface 149b1 and an inclined surface 149e inclined from the outer peripheral surface 149d toward the axial center of the piston ring 149. The inclined surface 149e is formed over a predetermined circumferential range including the position A1 of the piston ring 149. In the piston ring 149, the position A1 is the position farthest from the crank chamber 109a in the state (d) of FIG. 4.

[0042] FIG. 8 is a plan view showing the lower surface 149b2 side of the piston ring 149. Here, the lower surface 149b2 of the piston ring 149 is a surface facing the crank chamber 109a side opposite to the compression chamber 119 when the piston ring 149 is attached to the piston 104 as shown in FIG. 2. The inclined surface 149e is formed in a range of an angle θ1 larger than 180 degrees with the position A1 as a center position. One end 149e1 in the circumferential direction of the inclined surface 149e is located between a position A3 in a direction perpendicular to the rocking direction (z-axis direction) and an upper end of the range B of the gap 149a in the figure. The other end 149e2 in the circumferential direction of the inclined surface 149e is located between a position A4 in a direction perpendicular to the rocking direction (z-axis direction) and a lower end of the range B of the gap 149a in the figure.

[0043] Fig. 9A is a cross-sectional view of piston ring 149 in Fig. 7 at a position A1 perpendicular to the circumferential direction, as viewed from the positive direction of the z-axis. Fig. 9B is a cross-sectional view of piston ring 149 in Fig. 7 at a position A4 perpendicular to the circumferential direction, as viewed from the positive direction of the x-axis.

[0044] The dimension of piston ring 149 in the thickness direction (hereinafter referred to as the thickness dimension) is T. The inclination angle θ2 of inclined surface 149e with respect to outer circumferential surface 149d is set to a constant value over the entire region from end 149e1 to end 149e2 shown in FIG. 8. Note that although the inclination angle θ2 is referred to as the inclination angle with respect to outer circumferential surface 149d here, it is also the inclination angle with respect to the axis of piston ring 149. In other words, the angle between the axis and a straight line representing inclined surface 149e when piston ring 149 is cross-sectioned along a plane including the axis has the same value as the inclination angle.

[0045] Furthermore, the dimension t in the thickness direction of the inclined surface 149e (hereinafter referred to as the height dimension) is set to a maximum value tmax at the position A1, and decreases from the position A1 toward the ends 149e1 and 149e2. Of course, the height dimension t of the inclined surface 149e may be set to be the same from the position A1 to the ends 149e1 and 149e2.

[0046] Fig. 10 is a schematic diagram for explaining the gas pressure acting on piston ring 149 in state (d) of Fig. 4. Since state (d) is the compression stroke, piston 104 rises in the positive direction of the y axis and compresses the gas in compression chamber 119. As explained in Fig. 5, at crank angle α (= 270 degrees) in state (d), piston 104 has the largest absolute value of oscillation angle β in the compression stroke.

[0047] A groove width W of the annular groove 141 is set to be larger than a thickness dimension T (see FIG. 9A) of the piston ring 149. The gas in the compression chamber 119 enters the annular groove 141 through a gap between an upper surface 149b1 of the piston ring 149 and the annular groove 141. As a result, the pressure Pc of the gas in the compression chamber 119 is applied to an inner circumferential surface 149c of the piston ring 149.

[0048] 7 and 8, the outer periphery of the region on the negative side of the x-axis (one side in the rocking direction) of the piston ring 149 is formed by a cylindrical outer periphery surface 149d, and the outer periphery of the region on the positive side of the x-axis (the other side in the rocking direction) is formed by the outer periphery surface 149d and an inclined surface 149e. On the one side in the rocking direction of the piston ring 149, the upper end edge portion of the outer periphery surface 149d is in contact with the cylinder inner periphery surface 111a. Therefore, the piston ring 149 is pressed against the cylinder inner periphery surface 111a by the pressure difference between the crank chamber pressure P0 applied to the outer periphery surface 149d and the compression chamber 119 pressure Pc applied to the inner periphery surface 149c.

[0049] On the other hand, on the other side of the oscillation direction of the piston ring 149, the edge of the boundary between the outer peripheral surface 149d and the inclined surface 149e contacts the cylinder inner peripheral surface 111a. Therefore, the pressure Pc of the compression chamber 119 is applied to the outer peripheral surface 149d, and the pressure P0 of the crank chamber side is applied to the inclined surface 149e. In the cross section of FIG. 10, the pressure component in the direction perpendicular to the inner peripheral surface 149c of the pressure P0 applied to the inclined surface 149e is P0×cos(θ2). Since P0×cos(θ2) is smaller than Pc, the piston ring 149 is pressed against the cylinder inner peripheral surface 111a by the gas pressure difference on the other side of the oscillation direction as well.

[0050] At this time, the pressing force acting on the piston ring 149 can be regarded as the difference between the force due to the pressure Pc in the region of the height dimension t of the inner circumferential surface 149c and the force due to the pressure component P0×cos(θ2) on the inclined surface 149e. Therefore, the pressing force is proportional to t / T. The value of the pressing force also depends on the pressure difference, but according to experiments, in order to obtain a sufficient pressing force by the pressure difference, it is preferable to set t / T to about > 1 / 4.

[0051] Fig. 11 is a schematic diagram of the piston ring 149 shown in Fig. 10, viewed from a direction along the axis C1 (see Fig. 3) of the connecting rod 102. The circle indicated by the dashed line indicates the bottom surface of the annular groove 141. Since the piston 104 is tilted by an oscillation angle β as shown in Fig. 10, the piston ring 149, which is pressed against the cylinder inner circumferential surface 111a due to the gas pressure difference, is deformed into an elliptical shape as shown in Fig. 11. The major axis of the elliptical shape is in the oscillation direction, and if the minor axis (= cylinder inner diameter) is DC, then the major axis is DC / cosβ.

[0052] As the piston 104 rises from the bottom dead center, the oscillation angle β also increases, and the dimension of the piston ring 149 in the oscillation direction (=DC / cosβ) also increases. As a result, the outer periphery of the piston ring 149 adheres closely to the cylinder inner periphery 111a without any gap. At this time, the portion (seal portion) of the outer periphery of the piston ring 149 that contacts the cylinder inner periphery 111a is the boundary region (see FIG. 10) between the inclined surface 149e and the outer periphery 149d on the other side of the oscillation direction (the right side in the figure), and is the upper edge portion of the outer periphery 149d on one side of the oscillation direction (the left side in the figure).

[0053] The direction perpendicular to the rocking direction (positions A3 and A4) is the region where the above-mentioned seal portion switches, and the pressing force is likely to become unstable. Therefore, by forming the inclined surface 149e up to the region perpendicular to the rocking direction as shown in Figures 7 and 8, the pressing force due to the pressure difference is reliably applied to the piston ring 149.

[0054] Furthermore, if the inclined surface 149e is provided up to the region of the abutment 149a, a gap will be generated between the cylinder inner peripheral surface 111a and the piston ring 149, so it is preferable to arrange the ends 149e1, 149e2 of the inclined surface 149e in the intermediate region between the abutment 149a and each of the positions A3, A4 in the direction perpendicular to the rocking direction. Moreover, since the position A1 on the other side in the rocking direction is set to be the center of the inclined surface 149e, it is preferable to arrange the abutment 149a at the position A2 which is the farthest position from the region of the inclined surface as shown in Figs. 7 and 8.

[0055] The state of pressure acting on one cross section has been described above with reference to Fig. 10. However, in the piston ring 149 of this embodiment having the shape shown in Figs. 7 to 9B, the piston ring 149 is pressed against the cylinder inner circumferential surface 111a due to the gas pressure difference also in other cross sections.

[0056] In addition, the inclination angle θ2 of the inclined surface 149e with respect to the outer circumferential surface 149d is set to be larger than the maximum swing angle β(270) in the state (d) of Fig. 7. By setting θ2>β(270), the inclined surface 149e does not come into contact with the cylinder inner circumferential surface 111a, and the above-mentioned pressure relationship for pressing the piston ring 149 against the cylinder inner circumferential surface 111a is always satisfied during the compression stroke.

[0057] 7 to 9B, the inclination angle of the inclined surface 149e is set to the same value from one end 149e1 to the other end 149e2, but the inclination angle may be gradually decreased as it moves away from position A1. However, even in this case, the inclination angle at each circumferential position is set to be larger than the maximum swing angle β(270) at that circumferential position, that is, the inclination angle θ2>β(270).

[0058] FIG. 12 is a diagram showing a comparative example of this embodiment. A piston ring 149B in the comparative example is constituted only by an outer peripheral surface 149d having a cylindrical outer periphery like a general piston ring. The other shapes of the piston ring 149B are the same as those of the piston ring 149 described above. In the case of the piston ring 149B, when the piston 104 swings as shown in FIG. 12, the upper end edge portion of the outer peripheral surface 149d comes into contact with the cylinder inner peripheral surface 111a in the region on the negative x-axis side of the piston ring 149 (one side in the swing direction). On the other hand, in the region on the positive x-axis side of the piston ring 149B (the other side in the swing direction), the lower end edge portion of the outer peripheral surface 149d comes into contact with the cylinder inner peripheral surface 111a.

[0059] Therefore, on one side of the oscillation direction of the piston ring 149B, the piston ring 149 is pressed against the cylinder inner circumferential surface 111a due to the pressure difference between the pressure Pc applied to the inner circumferential surface 149c and the pressure P0 applied to the outer circumferential surface 149d, as in the case of the piston ring 149 described above. On the other hand, on the other side of the oscillation direction of the piston ring 149, the pressure Pc is applied to both the inner circumferential surface 149c and the outer circumferential surface 149d, the pressing force due to the pressure difference becomes zero, and the pressing force of the piston ring 149 against the cylinder inner circumferential surface 111a is insufficient. Therefore, there is a possibility that compressed gas will leak from the compression chamber 119 to the crank chamber, and the sealing performance is inferior to that of the piston ring 149 described above.

[0060] 13A and 13B show a case where the inclination angle θ2 of the inclined surface 149e in FIG. 9A is set so that θ2<β(270). FIG. 13A shows a case where the oscillation angle β is β=β(0)=0, and FIG. 13B shows a case where β=β(270)=0. In the case of FIG. 13A, the outer peripheral surface 149d contacts the cylinder inner peripheral surface 111a. When the oscillation angle β increases from β=0, the outer peripheral surface 149d moves away from the cylinder inner peripheral surface 111a, and the boundary E1 between the outer peripheral surface 149d and the inclined surface 149e comes into contact with the cylinder inner peripheral surface 111a. As a result, the pressure Pc on the compression chamber side is applied to the outer peripheral surface 149d above the boundary E1 in the figure, and the pressure P0 on the crank chamber side is applied to the inclined surface 149e below the boundary E1 in the figure.

[0061] As the rocking angle β increases further, the contact position between the piston ring 149 and the cylinder inner peripheral surface 111a changes from the boundary E1 to the lower end E2 of the inclined surface 149e. The state in which the lower end E2 contacts the cylinder inner peripheral surface 111a continues until the maximum rocking angle β (270) shown in FIG. 13B. In the state shown in FIG. 13B, the pressure Pc on the compression chamber side is applied to both the outer peripheral surface 149d and the inclined surface 149e. That is, the pressure load state becomes the same as in the comparative example shown in FIG. 12, and the pressing force of the piston ring 149 on the other end side of the rocking direction becomes insufficient.

[0062] As described above, in the first embodiment, the inclination angle θ2 of the inclined surface 149e is set to be constant regardless of the position on the inclined surface 149e and larger than the maximum swing angle β (270) in the compression stroke. For example, the first intersection line (straight line indicated by reference symbol 149e in FIG. 9A) between the plane including the axis of the piston ring 149 (e.g., the xy plane in FIG. 10) and the inclined surface 149e is a straight line, and the inclination angle θ2 with respect to the second intersection line (straight line indicated by reference symbol 149d in FIG. 9A) between the xy plane and the outer circumferential surface 149d is set to be larger than the maximum swing angle β (270) in the compression stroke.

[0063] Therefore, when the piston 104 is at the maximum swing angle β (270), the pressure P0 on the crank chamber side is applied to the inclined surface 149e of the piston ring 149. As a result, the piston ring 149 is pressed against the cylinder inner circumferential surface 111a by the gas pressure difference, and the sealing performance of the piston ring 149 can be improved.

[0064] Second Embodiment Figures 14 to 16 are diagrams for explaining a second embodiment of the present invention. Figures 14A and 14B show a cross section of a piston ring 149 in the second embodiment, and correspond to Figures 9A and 9B in the first embodiment. Figure 14A shows a cross section at position A1 (see Figure 7), and Figure 14B shows a cross section at position A4.

[0065] In the piston ring 149 shown in Figs. 9A and 9B, the cross-sectional shape of the inclined surface 149e is a straight line. On the other hand, in the piston ring 149 shown in Figs. 14A and 14B, the cross-sectional shape of the inclined surface 149f (the curve marked with the symbol 149f) is a curve convex toward the lower surface 149b2. For example, the cross-sectional shape of the inclined surface 149f is a circular arc. The inclination angle of the inclined surface 149f is the inclination angle of the tangent of the inclined surface 149f with respect to the outer circumferential surface 149d. In terms of the relationship with the axis of the piston ring 149, the angle between the tangent of the inclined surface 149f and the axis corresponds to the inclination angle.

[0066] The inclination angle of inclined surface 149f at position F0 in Fig. 14A is angle θ3 with respect to the tangent of inclined surface 149f at position F0 and outer circumferential surface 149d. The inclination angle θ3 increases from a first end portion (intersection with outer circumferential surface 149d) F10 of inclined surface 149f on the compression chamber side to a second end portion (intersection with lower surface 149b2) F20 on the crank chamber side. Although inclined surface 149f has a different surface shape from inclined surface 149e, the circumferential formation range centered on position A1 in Figs. 7 and 8 is set to be the same as inclined surface 149e.

[0067] The height dimension t of the inclined surface 149f is set to a maximum value tmax at the position A1, and decreases from the position A1 toward the circumferential end. Of course, the height dimension t of the inclined surface 149f may be set to the same from the position A1 to the circumferential end. The configuration other than the inclined surface 149f is the same as that of the piston ring 149 described in the first embodiment.

[0068] FIG. 15 is a diagram for explaining the contact position between the piston ring 149 and the cylinder inner peripheral surface 111a in the case of the state (d) in FIG. 4 where the rocking angle β is the maximum rocking angle β (270). At the maximum rocking angle β (270), the inclined surface 149f contacts the cylinder inner peripheral surface 111a at position F2. Therefore, the compression chamber pressure Pc is applied to the region between positions F1 and F2 of the inclined surface 149f and the outer peripheral surface 149d. Meanwhile, the crank chamber pressure P0 is applied to the region of the inclined surface 149f below position F1 in the figure. As a result, the piston ring 149 can obtain a pressing force due to the pressure difference between the gases.

[0069] On the other hand, when the piston 104 is at the bottom dead center or the top dead center, that is, when the oscillation angle β is 0 degrees, the contact position with the cylinder inner circumferential surface 111a is position F1. Therefore, when moving from state (c) to state (d) in FIG. 4, the contact position moves from position F1 to position F2. And when moving from state (d) to state (e) in FIG. 4, the contact position moves from position F2 to position F1. In the case of the inclined surface 149f, the pressing force is also proportional to t / T, so that the pressing force of the piston ring 149 in the compression stroke is maximum at the maximum oscillation angle β (270) and decreases as the contact position moves from position F2 to position F1.

[0070] In the examples shown in Figures 14A, 14B, and 15, a cylindrical outer peripheral surface 149d is provided in each cross-sectional view (i.e., at position A1), but the outer peripheral surface 149d may not be provided. That is, the position of the upper surface 149b1 of the piston ring 149 in the thickness direction may be set to position F1. This is the same as in the first embodiment, and the position of the upper surface 149b1 in Figure 9A may be set to the upper end position of the inclined surface 149e.

[0071] 16A and 16B are diagrams showing a comparative example in which inclined surface 149f is replaced with inclined surface 149f1. Inclined surface 149f1, the inclination angle of the tangent increases from the upper end to the lower end, but the inclination angle of the tangent at the lower end is set to be smaller than the maximum swing angle β(270).

[0072] 16A shows the relationship between the inclined surface 149f1 and the cylinder inner peripheral surface 111a when the oscillation angle β is 0<β<β(270). A position F30 on the inclined surface 149f1 is in contact with the cylinder inner peripheral surface 111a. Therefore, the compression chamber pressure Pc is applied to the area above the position F30 of the inclined surface 149f1 in the figure and to the outer peripheral surface 149d, and the crank chamber pressure P0 is applied to the area below the position F30 of the inclined surface 149f1 in the figure.

[0073] When β=0, the position F0 of the upper end of the inclined surface 149f1 comes into contact with the cylinder inner circumferential surface 111a. Therefore, the compression chamber pressure Pc is applied to the outer circumferential surface 149d, and the crank chamber pressure P0 is applied to the inclined surface 149f1.

[0074] 16B shows the relationship between the inclined surface 149f1 and the cylinder inner peripheral surface 111a when the oscillation angle β is β=β(270). The piston ring 149 is in contact with the cylinder inner peripheral surface 111a at the position F31 of the lower end of the inclined surface 149f1. Therefore, the compression chamber pressure Pc is applied to the entire outer periphery of the piston ring 149 (outer periphery surface 149d and inclined surface 149f1). That is, the pressure load situation is the same as in the comparative example shown in FIG. 12, and the pressing force of the piston ring 149 on the other end side in the oscillation direction is insufficient.

[0075] As described above, in the second embodiment, the inclination angle θ3 of the inclined surface 149f increases from the first end F10 on the opposite side of the crank chamber 109a to the second end F20 on the crank chamber side, and is set to be larger than the maximum swing angle β (270) at the second end F20.

[0076] In other words, when piston ring 149 is cross-sectioned along a plane (for example, the xy plane in FIG. 10) including the axis of piston ring 149, the intersection line between the xy plane and outer circumferential surface 149d (the straight line indicated by reference symbol 149d in FIG. 9A) and the intersection line between the xy plane and inclined surface 149e (the straight line indicated by reference symbol 149e) are defined as the first intersection line and the second intersection line, respectively. The second intersection line (149e) is set so that the inclination angle of the tangent of the second intersection line with respect to the first intersection line (149d) increases with increasing distance from the intersection point between the first intersection line and the second intersection line, and becomes larger than the maximum oscillation angle β at the end of the second intersection line.

[0077] As a result, during the compression stroke, the crank chamber pressure P0 is applied to the crank chamber side region of the outer periphery of the piston ring 149. Therefore, the piston ring 149 is pressed against the cylinder inner periphery 111a due to the pressure difference between the gas pressures applied to the inner and outer periphery, thereby improving the sealing performance.

[0078] According to the above-described embodiment, the following advantageous effects are obtained.

[0079] (1) As shown in Fig. 2, 10, 9A, 9B, 15, etc., the piston 104 reciprocates while oscillating inside the cylinder 110, a piston ring 149 provided on the outer periphery of the piston 104, and a crank chamber 109a in which a drive mechanism for driving the piston 104 is provided, the piston ring 149 has inclined surfaces 149e, 149f on the crank chamber side of the outer periphery of the piston ring 149, and the inclined surfaces 149e, 149f have an inclined surface region in which the inclination angles θ2, θ3, which are angles with the axis of the piston ring 149, are larger than the maximum oscillation angle β(270) in the compression stroke of the piston 104. For example, the region below the position F2 in the inclined surface 149e in Fig. 9A and the inclined surface 149f in Fig. 15 corresponds to the inclined surface region larger than the maximum oscillation angle β(270).

[0080] The pressure P0 on the crank chamber side is always applied to the inclined surface area larger than the maximum swing angle β (270) described above during the compression stroke. As a result, a pressing force is applied to the piston ring 149 against the cylinder inner peripheral surface 111a due to the difference in pressure applied to the inner and outer periphery of the piston ring 149. This gas pressure difference provides a sufficient pressing force, improving the sealing performance of the piston ring 149.

[0081] (2) In the above (1), as shown in Figs. 9A and 9B, the inclination angle θ2 of the inclined surface 149e is set to be constant regardless of the position on the surface of the inclined surface 149e and is set to be larger than the maximum swing angle β (270). In the compression stroke, the pressure Pc on the compression chamber side is applied to the outer peripheral surface 149d in Fig. 9A, and the pressure P0 on the crank chamber side is applied to the inclined surface 149e. As a result, a pressing force is generated due to the pressure difference, and a pressing force sufficient to press the piston ring 149 against the cylinder inner peripheral surface 111a is obtained.

[0082] (3) In the above (1), as shown in Figures 14A, 14B, 15, etc., the inclination angle θ3 of the inclined surface 149f increases from the first end F10 on the opposite side of the crank chamber 109a to the second end F20 on the crank chamber 109a side, and is set to be larger than the maximum swing angle β (270) at the second end F20.

[0083] By setting it in this way, the pressure P0 on the crank chamber side is always applied to the area of ​​the inclined surface 149f where the inclination angle θ3 is greater than the maximum swing angle β (270). As a result, the piston ring 149 is pressed against the cylinder inner circumferential surface 111a by the pressure difference between the gas pressures applied to the inner and outer periphery, thereby improving the sealing performance.

[0084] (4) In the above (1), as shown in Figures 7, 8, 14A, 14B, etc., it is preferable that the range in which the inclined surfaces 149e, 149f are formed is centered on the circumferential position A1 that is the farthest from the crank chamber 109a in the case of the maximum swing angle β (270), and that the inclined surfaces 149e, 149f are formed in a circumferential predetermined angle range (θ1) that includes the center (position A1). Since the pressing force due to the gas pressure difference is smallest at position A1, by forming the inclined surfaces 149e, 149f in the circumferential predetermined angle range (θ1) centered on position A1, it is possible to reliably eliminate the shortage of pressing force.

[0085] (5) In the above (4), as shown in Figs. 7 and 8, the predetermined circumferential angle range (θ1) is set to be greater than 180 degrees. Positions A3 and A4 in the direction perpendicular to the rocking direction (z-axis direction) in Figs. 7 and 8 are regions where the seal portion of piston ring 149 switches, and the pressing force is likely to become unstable. Therefore, by setting the predetermined circumferential angle range (θ1) of inclined surface 149e to be greater than 180 degrees, the pressing force due to the pressure difference is reliably applied to piston ring 149, and the sealing performance in the direction perpendicular to the rocking direction is reliably secured.

[0086] (6) In the above (4), as shown in Figures 7, 8, etc., piston ring 149 has abutment 149a at a position shifted by 180 degrees in the circumferential direction from the center of the predetermined circumferential angle range (θ1). In the circumferential direction of piston ring 149, the predetermined circumferential angle range (θ1) and a formation region (B) of abutment 149a are separated. By forming abutment 149a in this manner, abutment 149a does not form inclined surface 149e, and sealing performance at abutment 149a is ensured.

[0087] (7) In the above (4), as shown in Figures 9A, 14A, etc., the dimensions of the inclined surfaces 149e, 149f in the axial direction of the piston ring are set to be largest at the center (position A1) of a predetermined circumferential angle range (θ1). By setting them in this manner, the pressing force of the piston ring 149 at position A1 (the other side in the swinging direction) becomes large, and sealing performance is reliably ensured.

[0088] (8) In the above (1), as shown in Figures 9A, 14A, etc., it is preferable to set the first dimension t, which is the dimension of the inclined surfaces 149e, 149f in the axial direction of the piston ring, and the second dimension T, which is the dimension of the piston ring in the axial direction of the piston ring, to be (t / T) > 1 / 4. By setting them in this way, a sufficient pressing force can be obtained by the pressure difference.

[0089] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0090] 1...gas compressor, 2...electric motor, 3...tank, 4...compressor pulley, 5...electric motor pulley, 6...transmission belt, 7...piping, 10...compressor body, 102...connecting rod, 104...piston, 109...crankcase, 109a...crank chamber, 110...cylinder, 111...cylinder body, 111a...cylinder inner surface, 112...valve plate, 113...cylinder head, 119...compression chamber, 128...bearing, 140 ...Piston body, 141...Annular groove, 149, 149B...Piston ring, 149a...Abutment, 120...Straight rod portion, 160...Crankshaft, 161...Crank journal, 162...Crank pin, 163...Crank weight, 164...Crank arm, F10...First end, F20...Second end, α...Crank angle, β, β(α)...Oscillation angle, β(270)...Maximum oscillation angle, θ2, θ3...Inclination angle

Claims

1. A cylinder; A piston that reciprocates while oscillating inside the cylinder; A piston ring provided on an outer periphery of the piston; a crank chamber in which a drive mechanism that drives the piston is provided, The piston ring has an inclined surface on the crank chamber side of an outer periphery of the piston ring, the inclined surface has an inclined surface region in which an inclination angle, which is an angle with an axis of the piston ring, is larger than a maximum swing angle of the piston during a compression stroke.

2. 2. The gas compressor according to claim 1, a tilt angle of the inclined surface that is constant regardless of a position on the inclined surface and that is set to be larger than the maximum swing angle;

3. 2. The gas compressor according to claim 1, a first end of the inclined surface opposite the crank chamber, the inclination angle of the inclined surface increasing from a first end of the inclined surface opposite the crank chamber to a second end of the inclined surface on the crank chamber side, and the inclination angle at the second end is set to be larger than the maximum swing angle.

4. 2. The gas compressor according to claim 1, a range in which the inclined surface is formed is set to a predetermined circumferential angular range including a circumferential position farthest from the crank chamber in the case of the maximum swing angle, the center of the range being a circumferential position farthest from the crank chamber in the case of the maximum swing angle;

5. 5. The gas compressor according to claim 4, The predetermined circumferential angular range is set to be greater than 180 degrees.

6. 5. The gas compressor according to claim 4, The piston ring has a joint at a position shifted by a circumferential angle of 180 degrees from the center of the predetermined circumferential angular range, the predetermined circumferential angular range and a region where the gap is formed are spaced apart in a circumferential direction of the piston ring.

7. 5. The gas compressor according to claim 4, a dimension of the inclined surface in an axial direction of the piston ring is set to be largest at the center of the predetermined circumferential angular range.

8. 2. The gas compressor according to claim 1, a first dimension t that is a dimension of the inclined surface in the piston ring axial direction and a second dimension T that is a dimension of the piston ring in the piston ring axial direction are set to be (t / T) > 1 / 4.

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