WO2022180974A1

WO2022180974A1 - Reciprocating compressor

Info

Publication number: WO2022180974A1
Application number: PCT/JP2021/044090
Authority: WO
Inventors: 修平永田; 伸之成澤
Original assignee: 株式会社日立産機システム
Priority date: 2021-02-25
Filing date: 2021-12-01
Publication date: 2022-09-01
Also published as: JP2022129786A

Abstract

A reciprocating compressor comprising: a crankshaft having a rotation axis offset with respect to the central axis of a cylinder; a piston that defines a compression chamber together with the cylinder and reciprocates in the cylinder; and a connecting rod that has one side pivotably coupled to the crankshaft and the other side fixed to the piston and is caused to swing by the rotational motion of the crankshaft. The piston has: a top surface that constitutes a wall surface of the compression chamber; a sliding surface that slides on the inner peripheral surface of the cylinder within a range defined according to the range of the swing angle of the connecting rod; and a first non-sliding surface having such a shape as to join the top surface and the sliding surface to each other and avoid contact with the inner peripheral surface of the cylinder. At least a part of the first non-sliding surface is positioned closer to the inner peripheral surface of the cylinder than the first virtual extended curved plane obtained by virtually extending the sliding surface toward the top surface side.

Description

reciprocating compressor

The present invention relates to a reciprocating compressor in which a piston reciprocates within a cylinder.

In a reciprocating compressor, a piston is connected to a crankshaft via a connecting rod, and the crankshaft converts the rotational force of a rotary drive source such as an electric motor into reciprocating motion of the piston to compress gas. be. In some reciprocating compressors, a piston is connected to the tip (small end) of a connecting rod via a bearing, and the piston swings with respect to the connecting rod and reciprocates without tilting with respect to the cylinder. there is something On the other hand, there is a type in which a piston is fixed to the tip of a connecting rod, and the piston swings and reciprocates with respect to the cylinder. That is, there is a reciprocating compressor provided with an oscillating piston that oscillates integrally with a connecting rod. Compared to the former, the latter can improve durability by reducing the number of moving parts, reduce weight and noise, and reduce costs by reducing the number of parts.

Patent Document 1 describes an example of a reciprocating compressor equipped with an oscillating piston. In the reciprocating compressor described in Patent Document 1, a spherical piston that reciprocates while sliding in a cylinder swings in a suction stroke, and the piston spherical surface at a portion that comes into sliding contact with the inner peripheral surface of the cylinder is recessed to form a piston rod. A suction port is formed for drawing fluid into the compression chamber from the (connecting rod) side.

JP-A-62-253971

The reciprocating compressor described in Patent Document 1 has a structure in which the rotation axis of the crankshaft and the central axis of the cylinder intersect. In this structure, when the swing angle of the piston (piston rod) is large, the force acting between the piston and the cylinder in the compression stroke (hereinafter referred to as side force) is correspondingly large. This increases the friction between the cylinder and the piston, leading to energy loss. Therefore, there is a demand to suppress the side force during the compression stroke. Therefore, it is possible to reduce the side force during the compression stroke by adopting an offset structure in which the rotation axis of the crankshaft is not intersected with the central axis of the cylinder, but shifted.

Further, in the reciprocating compressor described in Patent Document 1, by making the piston that swings integrally with the piston rod spherical, even if the swing angle of the piston with respect to the cylinder is large, Since it slides smoothly, it is possible to reduce the risk of damage to the piston. However, a spherical piston has a larger dead volume of a compression chamber than a cylindrical piston that is pivotably connected to a connecting rod via a bearing. Since the size of the dead volume causes deterioration in the discharge performance of the compressor (decrease in discharge flow rate and volumetric efficiency), there is a demand to reduce the dead volume.

Also, in the reciprocating compressor described in Patent Document 1, since the piston is spherical, it is necessary to maintain the airtightness of the compression chamber by line contact between the piston and the cylinder. With this configuration, there is a risk that the airtightness of the compression chamber will be lower than in the case of sealing by surface contact between the cylindrical piston and cylinder described above. Therefore, a method of attaching a piston ring to a piston can be considered. However, since the piston ring oscillates with respect to the cylinder with the oscillating motion of the piston, if the oscillating angle of the piston is large, the sealing performance of the piston ring may not be sufficiently exhibited. However, in a reciprocating compressor that uses an offset structure that reduces side force during the compression stroke, it is possible to suppress the oscillation of the piston ring during the compression stroke, thereby maintaining the sealing performance of the piston ring during the compression stroke. can do.

However, in the case of the offset structure, the piston's rocking motion is asymmetrical, so in order for the piston ring to exhibit its sealing performance, it is necessary to mount the piston ring so that it is inclined with respect to the top surface of the piston. When the piston ring is attached to the piston in this way, the area of the outer peripheral surface of the piston located on the top side of the piston ring increases, resulting in an increase in the dead volume of the compression chamber.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to reduce the side force acting between the piston and the cylinder during the compression stroke, and to reduce the dead volume. To provide a reciprocating compressor capable of

The present application includes a plurality of means for solving the above problems, one example of which is a cylinder having a central axis, a crankshaft having a rotation axis offset with respect to the central axis of the cylinder, and A piston, which forms a compression chamber together with a cylinder and reciprocates in the cylinder, is rotatably connected to the crankshaft at one side and fixed to the piston at the other side. a connecting rod that swings with respect to a cylinder; the piston has a top surface that constitutes a part of the wall surface of the compression chamber; A first sliding surface that slides on the inner peripheral surface of the cylinder within a range determined according to the above, and a first shape that connects the top surface and the sliding surface and avoids contact with the inner peripheral surface of the cylinder. At least a portion of the first non-sliding surface is closer to the cylinder than the first imaginary extended curved surface that virtually extends the sliding surface toward the top surface. is located near the inner peripheral surface of the

According to the present invention, by offsetting the crankshaft with respect to the cylinder, it is possible to reduce the swing angle of the piston during the compression stroke, and at least a portion of the first non-sliding surface of the piston is formed on the outer peripheral side (diameter direction outer side) of the first imaginary extended curved surface, the gap between the first non-sliding surface of the piston and the inner peripheral surface of the cylinder is reduced. Therefore, it is possible to reduce the dead volume while reducing the side force acting between the piston and the cylinder during the compression stroke.
Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a schematic cross-sectional view showing a first embodiment of a reciprocating compressor of the present invention; FIG. FIG. 4 is a characteristic diagram showing the characteristics of the offset structure in the first embodiment of the reciprocating compressor of the present invention; FIG. 4 is a characteristic diagram showing seal characteristics of piston rings in the first embodiment of the reciprocating compressor of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the piston which mounted|wore the piston ring in 1st Embodiment of the reciprocating compressor of this invention, and its peripheral structure. 1 is a perspective view showing a single piston in a first embodiment of a reciprocating compressor of the present invention; FIG. It is an explanatory view showing dead volume in a 1st embodiment of a reciprocating compressor of the present invention. FIG. 6 is a diagram showing a piston with a piston ring and its peripheral structure in a second embodiment of the reciprocating compressor of the present invention; FIG. 7 is a diagram showing a piston with a piston ring and its peripheral structure in a reciprocating compressor according to a third embodiment of the present invention; FIG. 5 is a schematic cross-sectional view showing a fourth embodiment of the reciprocating compressor of the present invention; FIG. 10 is a diagram showing a piston fitted with a piston ring and its peripheral structure in a fourth embodiment of the reciprocating compressor of the present invention; FIG. 11 is a perspective view showing a single piston in a reciprocating compressor according to a fourth embodiment of the present invention; It is an explanatory view showing dead volume in a 4th embodiment of a reciprocating compressor of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a reciprocating compressor of the present invention will be described below with reference to the drawings.
[First embodiment]
A configuration of a reciprocating compressor according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view showing a first embodiment of a reciprocating compressor of the present invention.

In FIG. 1, a reciprocating compressor 1 compresses gas such as air using a crank mechanism and discharges the compressed gas into a tank (not shown) or the like. Specifically, the reciprocating compressor 1 includes a crankshaft 2 that rotates by being driven by a rotary drive source (not shown) such as an electric motor, a crankcase 3 that rotatably accommodates the crankshaft 2, a crank It comprises a cylinder 4 attached to the case 3 , a piston 5 reciprocating within the cylinder 4 , and a connecting rod 6 connecting the piston 5 and the crankshaft 2 .

The crankshaft 2 rotates about the rotation axis Rs. The crankshaft 2 includes a crank journal 21 that is rotatably supported by bearings (not shown) arranged in the crankcase 3 and rotates around a rotation axis Rs, and a crank that is eccentric to the rotation axis Rs. It has a pin 22, a crank arm 23 connecting the crank journal 21 and the crank pin 22, and a balance weight 24 for adjusting the balance during rotation. The crankpin 22 is rotatably connected to one end (a large end 62 described later) of the connecting rod 6 via the bearing 7 . As the bearing 7, for example, it is possible to use a rolling bearing, a sliding bearing, or the like. Note that the bearing 7 can also be configured integrally with either the connecting rod 6 or the crankshaft 2 . The crankcase 3 is provided with a breathing hole 3a that communicates the inside and outside of the case 3 with each other.

The cylinder 4 has a central axis Cc, and is mounted so that an opening on one side (lower side in FIG. 1) communicates with the inside of the crankcase 3 . A cylinder head 8 is attached via a valve plate 9 to the end of the cylinder 4 on the other side (upper side in FIG. 1). The cylinder head 8 has an intake chamber 8a for taking in gas from the outside and an exhaust chamber 8b for discharging compressed gas to the outside. The valve plate 9 closes the opening on the other side of the cylinder 4, and has an intake hole 9a that communicates the inside of the cylinder 4 (compression chamber 14, which will be described later) with the intake chamber 8a of the cylinder head 8, and the opening of the cylinder 4. It has a discharge hole 9b that communicates the inside with the exhaust chamber 8b of the cylinder head 8 .

A reed valve type intake valve 10 and a discharge valve 11 are attached to the valve plate 9 . The intake valve 10 allows the gas in the intake chamber 8a of the cylinder head 8 to flow into the cylinder 4 through the intake hole 9a, while allowing the gas in the cylinder 4 to flow into the intake chamber 8a through the intake hole 9a. to prevent The discharge valve 11 allows the gas in the cylinder 4 to flow into the exhaust chamber 8b of the cylinder head 8 through the discharge hole 9b, while allowing the gas in the exhaust chamber 8b to flow into the cylinder 4 through the discharge hole 9b. to prevent

The piston 5 is fixed to the other end (the small end 63 described later) of the connecting rod 6 without a bearing, and is integrated with the connecting rod 6 . That is, the piston 5 is a rocking piston (locking piston) that reciprocates while rocking in the cylinder 4 integrally with the connecting rod 6 when the crankshaft 2 rotates. As a method for fixing the piston 5 and the connecting rod 6, fastening with bolts, welding, press-fitting, or the like is possible. The piston 5 is made of a material different from that of the connecting rod 6, for example, in order to ensure both the sliding characteristics of the piston 5 and the mechanical strength of the connecting rod 6 in an environment where lubricating oil is not used. . The piston 5 together with the cylinder 4 and the valve plate 9 form a compression chamber 14 for compressing gas. As the piston 5 reciprocates within the cylinder 4, the compression chamber 14 repeats expansion and contraction. The suction valve 10 and the discharge valve 11 are opened and closed according to the expansion and contraction of the compression chamber 14 . By adopting a configuration in which lubricating oil is not supplied to the piston 5, there is an advantage that lubricating oil does not mix with the gas in the compression chamber 14. FIG. If a large amount of lubricating oil flows into the compression chamber 14, there is a concern that reliability will be lowered, such as a decrease in compressor efficiency due to a decrease in the amount of intake air and damage to the valve body due to liquid compression. Details of the structure of the piston 5 will be described later.

A piston ring 12 is attached to the piston 5 to improve the airtightness of the compression chamber 14 . The piston ring 12 is formed so as to smoothly slide in the cylinder 4 when attached to the piston 5 and to keep the compression chamber 14 airtight during the compression stroke. Specifically, the piston ring 12 is a substantially C-shaped member having a substantially cylindrical outer peripheral surface, and has an abutment (not shown). The outer diameter of the piston ring 12 is set to be slightly larger than the inner diameter of the cylinder 4 in the natural state. Therefore, when the piston ring 12 attached to the piston 5 is inserted into the cylinder 4, the reaction force due to the deformation of the piston ring 12 causes the outer peripheral surface of the piston ring 12 to be in close contact with the inner peripheral surface 4a of the cylinder 4. By doing so, the airtightness of the compression chamber 14 is maintained.

The connecting rod 6 includes a straight rod portion 61 , a cylindrical large end portion 62 provided at one end of the straight rod portion 61 , and a hemispherical small end portion provided at the other end of the straight rod portion 61 . and end 63 . The straight rod portion 61 is tapered from the large end portion 62 side toward the small end portion 63 side. The large end portion 62 is a portion that is connected to the crank pin 22 of the crankshaft 2 via the bearing 7 and is rotatable about the center axis Cb of the bearing 7 as a rotation axis. The small end 63 has a spherical surface connected to the straight rod 61 and a circular flat surface connected to the piston 5 . A straight line connecting the rotation axis of the cylindrical big end 62 (center axis Cb of the bearing 7) and the center of the hemispherical small end 63 is the center line Cr of the connecting rod 6, and the straight rod 61 is connected It extends along the center line Cr of the rod 6.

In the reciprocating compressor 1 according to the present embodiment, the rotational axis Rs of the crankshaft 2 (crank journal 21) is offset (separated) from the central axis Cc of the cylinder 4 without intersecting it. It has an offset structure. In this offset structure, in order to reduce the force (hereinafter referred to as side force) acting between the piston 5 and the cylinder 4 during the compression stroke, the rotation axis Rs of the crankshaft 2 is shifted with respect to the central axis Cc of the cylinder 4 during the compression stroke. is offset in the pressing direction of the piston 5 against the inner peripheral surface 4a of the cylinder 4. As shown in FIG. For example, as shown in FIG. 1, when the cylinder 4 is positioned above the crankshaft 2 and the crankshaft 2 rotates counterclockwise, the rotation axis Rs of the crankshaft 2 is positioned relative to the central axis Cc of the cylinder 4. , and is arranged at a position separated by an offset amount δ to the left. Conversely, when the crankshaft 2 rotates clockwise, the rotation axis Rs of the crankshaft 2 is positioned rightwardly away from the center axis Cc of the cylinder 4 by the offset amount δ.

Next, the characteristics of the offset structure of the reciprocating compressor according to this embodiment will be described with reference to FIGS. 1 to 3. FIG. FIG. 2 is a characteristic diagram showing the relationship between the crank angle and the swing angle of the piston and connecting rod. FIG. 3 is a diagram showing the relationship between the inclination angle of the piston ring with respect to the cylinder and the amount of gas leakage. In FIG. 2, the horizontal axis .theta. indicates the crank angle, and the vertical axis .beta. indicates the swing angle of the piston and connecting rod. In FIG. 3, the horizontal axis indicates the inclination angle of the piston ring with respect to the cylinder, and the vertical axis indicates the leakage amount (mass flow rate) of the gas leaking from the gap between the piston ring and the cylinder.

In FIG. 1, the crank angle θ, which is the rotation angle of the crankshaft 2, is 0° when the crankpin 22 is at its lowest point, and the counterclockwise direction is the positive direction. The angle between the central axis Cc of the cylinder 4 and the central axis Cr of the connecting rod 6 (also coinciding with the central axis 5b of the piston 5 described later) on the acute side is defined as a swing angle β. The swing angle β has a positive value when the central axis Cb of the bearing 7 is positioned on the left side of the central axis Cc of the cylinder 4, and is a positive value when the central axis Cb of the bearing 7 is positioned on the right side of the central axis Cc of the cylinder 4. Negative value.

As a comparative example for the offset structure of the present embodiment, a configuration different from the offset structure is considered. That is, when the rotation axis Rs of the crankshaft 2 intersects the central axis Cc of the cylinder 4 (that is, when the offset amount δ is 0), the oscillating motion of the piston 5 and the connecting rod 6 does not cross the central axis Cc of the cylinder 4. symmetrical to In this case, the maximum value of the swing angle β during the compression stroke (while the piston 5 moves from the bottom dead center to the top dead center) and the swing angle β during the suction stroke (while the piston 5 moves from the top dead center to the bottom dead center) becomes equal to the maximum value of the dynamic angle β.

On the other hand, in the case of the offset structure of the present embodiment, the oscillating motion of the piston 5 and the connecting rod 6 is asymmetric with respect to the central axis Cc of the cylinder 4. That is, as shown in FIG. 2, the change of the swing angle β with respect to the crank angle θ is vertically asymmetric with respect to the horizontal axis. Specifically, the absolute value β1 of the maximum swing angle in the compression stroke is smaller than the absolute value β2 of the maximum swing angle in the intake stroke. Also, the absolute value β1 of the maximum swing angle in the compression stroke is smaller than the absolute value of the maximum swing angle in the compression stroke in the case of the comparative example in which the offset amount δ is zero. Thus, in the offset structure, compared to the comparative example in which the offset amount δ is 0, the absolute value of the maximum swing angle in the compression stroke can be kept small, and accordingly, the distance between the piston 5 and the cylinder 4 in the compression stroke can be reduced. It is possible to reduce the force (side force) acting on the

Also, by keeping the maximum value of the swing angle β during the compression stroke small, it is possible to reliably maintain the airtightness of the compression chamber 14 during the compression stroke by the piston ring 12 . This is for the following reasons. Sealing characteristics of the compression chamber 14 by the piston ring 12 are as shown in FIG. 3, for example. That is, when the inclination angle of the outer peripheral surface (substantially cylindrical surface) of the piston ring 12 with respect to the inner peripheral surface 4a (substantially cylindrical surface) of the cylinder 4 is within a small range from 0°, the ) can be suppressed to an extremely small amount. This is because when the inclination angle is small, the piston ring 12 is in substantially surface contact with the cylinder 4 , and the piston ring 12 appropriately seals the gap with the cylinder 4 . On the other hand, when the inclination angle of the piston ring 12 increases, the piston ring 12 comes into a state of one-sided contact with the inner peripheral surface 4a of the cylinder 4, and the contact state between the piston ring 12 and the cylinder 4 changes from surface contact to line contact. Or it will be in a state of point contact. As a result, the greater the inclination angle of the piston ring 12, the worse the sealing characteristics of the piston ring 12, and the more the amount of gas leaking from the compression chamber 14 increases. In this embodiment, the piston ring 12 is attached to the rocking piston 5 (locking piston). change by In the offset structure of the present embodiment, since the swing angle β during the compression stroke is small, the inclination angle of the piston ring 12 is also small. Therefore, the amount of gas leaked from the compression chamber 14 during the compression stroke is smaller than in the comparative example in which the offset amount δ is zero.

Next, the structure of the piston, which constitutes part of the first embodiment of the reciprocating compressor of the present invention, will be described with reference to FIGS. 1, 2, 4 and 5. FIG. FIG. 4 is a diagram showing a piston fitted with a piston ring and its peripheral structure in the first embodiment of the reciprocating compressor of the present invention. FIG. 5 is a perspective view showing a single piston in the first embodiment of the reciprocating compressor of the present invention.

4 and 5, the piston 5 is formed in a substantially disk shape and has an outer peripheral surface that can smoothly reciprocate while rocking within the cylinder 4 (see FIG. 1). . The piston 5 has a top surface 51 forming part of the wall surface of the compression chamber 14 (see FIG. 1), a sliding surface 52 and

non-sliding surfaces

53 and 54 as outer peripheral surfaces. The sliding surface 52 is a curved surface that slides against the inner peripheral surface 4a of the cylinder 4 during rocking and reciprocating motion. The non-sliding surfaces 53 and 54 are curved surfaces that are continuous with the sliding surface 52 and are formed in a shape that avoids contact with the inner peripheral surface 4 a of the cylinder 4 .

The shape of the piston 5 has geometric constraints from the viewpoint of mechanism motion. Since the reciprocating compressor 1 of this embodiment has an offset structure in which the crankshaft 2 is offset with respect to the cylinder 4, the oscillating motion of the piston 5 and the connecting rod 6 is asymmetrical. Therefore, in response to its asymmetrical rocking motion, the piston 5 is moved relative to the plane containing the central axis 5b of the piston 5 and the rotation axis of the large end 62 of the connecting rod 6 (that is, the central axis Cb of the bearing 7). are formed asymmetrically (left-right asymmetrical with respect to the central axis 5b in FIG. 4). Here, the central axis 5b of the piston 5 is a straight line passing through the later-described central point 5a of the sliding surface 52 and the rotation axis of the large end 62 of the connecting rod 6 (the central axis Cb of the bearing 7). It also coincides with the center line Cr of the rod 6 .

The top surface 51 is, for example, planar. However, as shown in FIG. 4, the top surface 51 is not parallel to the orthogonal surface 5c of the piston 5 but is formed as an inclined surface that is inclined in accordance with the asymmetric rocking motion of the piston 5 with respect to the central axis Cc of the cylinder 4. It is Here, the perpendicular plane 5c of the piston 5 is a plane perpendicular to the central axis 5b of the piston 5 and including the center point 5a of the sliding surface 52, which will be described later. The top surface 51 is formed so as to be substantially parallel to the valve plate 9 when the piston 5 is positioned at the top dead center (see FIG. 6, which will be described later). Specifically, the top surface 51 is formed as an inclined surface that approaches the perpendicular surface 5c of the piston 5 in the same direction as the offset direction of the crankshaft 2 with respect to the cylinder 4 (leftward in FIG. 4). The top surface 51 is provided with a groove for avoiding contact with the intake valve 10 (see FIG. 1) and a projection that can be inserted into the discharge hole 9b (see FIG. 1) at a position facing the discharge hole 9b. is also possible.

The sliding surface 52 is formed in a spherical shape with a smaller diameter than the cylindrical diameter of the cylinder 4 so that the piston 5 can smoothly oscillate and reciprocate within the cylinder 4 . The center point 5 a of the spherical sliding surface 52 is located on the extension line of the center line Cr of the connecting rod 6 . The sliding surface 52 is a curved surface formed over the range of the sliding angle φ determined according to the range of the swinging angle β in the swinging motion of the connecting rod 6 . For example, as shown in FIG. 2, the maximum swing angle (absolute value) in the stroke (compression stroke) toward top dead center is β1, and the maximum swing angle (absolute value) in the stroke (intake stroke) toward bottom dead center ( When the absolute value) is β2, the sliding surface 52 shown in FIG. ) with respect to the orthogonal plane 5c of the piston 5, the range of the sliding angle φ on the top surface 51 side is β1 and the range of the sliding angle φ on the connecting rod 6 side is β2. Conversely, the sliding surface 52 on the side opposite to the offset direction with respect to the central axis 5b of the piston 5 (the right side in FIG. The range of φ becomes β2 and the range of the sliding angle φ on the side of the connecting rod 6 becomes β1.

The non-sliding surface is a curved surface formed outside the range of the sliding angle φ determined according to the range of the swinging angle β in the swinging motion of the connecting rod 6, and the top surface 51 and the sliding surface 52 are formed. It has a connecting first non-sliding surface 53 and a second non-sliding surface 54 extending from the sliding surface 52 toward the connecting rod 6 side. The first non-sliding surface 53 is a curved surface located on the outer peripheral side (outside in the radial direction) of a spherical first virtual extended curved surface 52V1 that virtually extends the sliding surface 52 toward the top surface 51 side. formed. That is, when the piston 5 is arranged in the cylinder 4, the first non-sliding surface 53 is closer to the inner peripheral surface 4a of the cylinder 4 than the first imaginary extended curved surface 52V1 of the sliding surface 52. formed to be located.

However, the first non-sliding surface 53 needs to be out of contact with the inner peripheral surface 4a of the cylinder 4 even when the swinging motion of the connecting rod 6 (piston 5) reaches the maximum swinging angle. be. That is, when the piston 5 is at the maximum swing angle, the first non-sliding surface 53 is required to be a curved surface located radially inward of the curved surface coinciding with the inner peripheral surface 4a of the cylinder 4 .

For example, as shown in FIG. 2, in the swing motion of the connecting rod 6 (piston 5), it is assumed that the maximum swing angle in the compression stroke is β1 and the maximum swing angle in the suction stroke is β2. . For convenience of explanation, of the first non-sliding surface 53, the portion on the same side as the offset direction of the crankshaft 2 (left side in FIG. 4) is the offset-side non-sliding surface 531, and the opposite side to the offset direction 4) is called an anti-offset side non-sliding surface 532. As shown in FIG. In order for the offset side non-sliding surface 531 to be a curved surface that matches the inner peripheral surface 4a of the cylinder 4, the first plane 5e that forms an angle β1 that is the same as the maximum swing angle in the compression stroke with respect to the orthogonal surface 5c of the piston 5 is This is the case where the first cylindrical surface 531c is perpendicular to each other. On the other hand, in order for the non-offset side non-sliding surface 532 to be a curved surface that coincides with the inner peripheral surface 4a of the cylinder 4, a second plane that forms an angle β2 that is the same as the maximum swing angle in the intake stroke with respect to the perpendicular surface 5c of the piston 5 is required. This is the case of the second cylindrical surface 532c orthogonal to 5f. In this case, since the shape of the offset-side non-sliding surface 531 and the shape of the anti-offset-side non-sliding surface 532 are different, normally the connecting portion between the offset-side non-sliding surface 531 and the anti-offset-side non-sliding surface 532 , a ridge line 533 is formed. However, the ridge line 533 is rounded, and the offset-side non-sliding surface 531 and the counter-offset-side non-sliding surface 532 are smoothly connected. That is, the edge line 533 disappears due to rounding. Therefore, in FIG. 4, the edge line 533 is indicated by a two-dot chain line for convenience of explanation, but the edge line 533 is not illustrated in other drawings. In FIG. 4, the ridge line 533 is positioned substantially at the center in the left-right direction, but it can be set at any position. That is, at which position in the circumferential direction the offset-side non-sliding surface 531 and the counter-offset-side non-sliding surface 532 are connected can be changed as necessary.

Thus, the first non-sliding surface 53 is a first cylindrical surface 531c orthogonal to the first plane 5e forming the same angle as the maximum swing angle β1 of the compression stroke with respect to the orthogonal surface 5c of the piston 5. , and a second cylindrical surface 532c orthogonal to the second plane 5f forming the same angle as the maximum swing angle β2 of the intake stroke with respect to the orthogonal surface 5c of the piston 5 (inward in the radial direction). By positioning, it is possible to avoid contact with the inner peripheral surface 4a of the cylinder 4 when the piston 5 swings. In addition, the first non-sliding surface 53 of the present embodiment is formed so as to be located on the outer peripheral side (diameter direction outside) of the first imaginary extended curved surface 52V1 of the sliding surface 52 .

On the other hand, the second non-sliding surface 54 is formed, for example, into a curved surface that coincides with a spherical second virtual extended curved surface 52V2 that virtually extends the sliding surface 52 toward the connecting rod 6 side. That is, the second non-sliding surface 54 is a spherical curved surface formed by extending the sliding surface 52 toward the connecting rod 6, and is configured as an outer peripheral surface that does not come into contact with the inner peripheral surface of the cylinder 4. there is

An annular groove 55 for mounting the piston ring 12 is provided on the outer peripheral surface of the piston 5, as shown in FIG. The annular groove 55 is provided, for example, within the region of the sliding surface 52 (the range of the sliding angle φ shown in FIG. 4). In addition, the annular groove 55 (piston ring 12) is formed with respect to the top surface 51 so as to approach the top surface 51 of the piston 5 as it goes in the same direction as the offset direction of the crankshaft 2 (leftward in FIG. 4), for example. is sloping. That is, the annular groove 55 is formed such that the portion on the same side as the offset direction is positioned closer to the top surface 51 than the portion on the opposite side to the offset direction. Part or all of the annular groove 55 (piston ring 12) can be provided outside the range of the sliding angle φ.

Next, the operation and effects of the reciprocating compressor according to the first embodiment of the present invention will be explained using FIGS. 1 to 6. FIG. FIG. 6 is an explanatory diagram showing the state when the piston is positioned at the top dead center in the first embodiment of the reciprocating compressor of the present invention.

In the reciprocating compressor 1 shown in FIG. 1, when the crankshaft 2 is rotated by a rotary drive source (not shown) such as an electric motor (counterclockwise rotation in FIG. 1), the connecting rod 6 swings. Due to the movement, the piston 5 reciprocates in the cylinder 4 while being oscillated with its movement in the radial direction restricted. In the intake stroke in which the piston 5 moves from the top dead center to the bottom dead center, the compression chamber 14 expands, the intake valve 10 opens, gas is sucked into the compression chamber 14 from the intake chamber 8a in the cylinder head 8, and the crank Gas is sucked into the compression chamber 14 from inside the case 3 through the gap between the piston 5 (piston ring 12 ) and the cylinder 4 . On the other hand, in the compression stroke in which the piston 5 moves from the bottom dead center to the top dead center, the compression chamber 14 contracts, the gas in the compression chamber 14 is compressed, the discharge valve 11 opens, and the gas flows through the exhaust chamber 8b in the cylinder head 8. It is discharged to the outside.

In the reciprocating compressor 1 according to the embodiment, as shown in FIG. The maximum value of the swing angle β of the piston 5 and the connecting rod 6 is made small. As a result, the force (side force) acting between the piston 5 and the cylinder 4 during the compression stroke can be reduced.

In addition, in the reciprocating compressor 1 according to the embodiment, a piston ring 12 is attached to the piston 5 . By reducing the swing angle β of the piston 5 during the compression stroke by the offset structure, the inclination angle of the piston ring 12 with respect to the cylinder 4 is reduced. Therefore, as shown in FIG. 3, the high airtightness of the compression chamber 14 can be ensured by the sealing performance of the piston ring 12 .

By the way, when the piston 5 is positioned at the top dead center, as shown in FIG. A gap (hereinafter referred to as top clearance ε) is provided. From the viewpoint of compressor performance, it is ideal that the volume of the compression chamber 14 becomes zero when the piston 5 is at the top dead center. However, in reality, there is a volume due to the top clearance ε and other gaps. The volume of the compression chamber 14 when the piston 5 is at the top dead center is called dead volume. The size of the dead volume is one of the factors of deterioration of compressor discharge performance (decrease in discharge flow rate and volumetric efficiency). In order to realize a highly efficient compressor, it is desirable to reduce the dead volume.

In addition to the top clearance ε, the gap between the outer peripheral surface of the piston 5 and the inner peripheral surface 4a of the cylinder 4 is one of the causes of the dead volume. In the present embodiment, since the piston ring 12 seals the gap between the piston 5 and the cylinder 4, the outer peripheral surface of the piston 5 and the inner peripheral surface 4a of the cylinder 4, which are located on the top surface 51 side of the piston ring 12, are separated from each other. The gap G between is one of the factors of the dead volume. Therefore, in order to reduce the dead volume, among the outer peripheral surfaces of the piston 5 shown in FIG. It is necessary to reduce the gap G (see FIG. 6) between a portion (the right portion in FIG. 5 and the first non-sliding surface 53) and the inner peripheral surface 4a of the cylinder 4.

As one of the measures to reduce the dead volume, the region (area ) can be reduced. This can be realized by setting the position of the annular groove 55 closer to the top surface 51 side. As the annular groove approaches the top surface 51, the thickness (thickness) of the disk-shaped portion sandwiched between the annular groove and the top surface 51 is correspondingly reduced. The thickness of the disk-shaped portion cannot be less than a predetermined value from the viewpoint of ensuring the strength necessary to hold the piston ring 12 in the annular groove.

In this embodiment, the top surface 51 is inclined toward the annular groove 55 as it goes in the same direction as the offset direction of the crankshaft 2 (leftward in FIGS. 4 and 5). The thickness of the disk-shaped portion is the thinnest on the same side as the offset direction (left side in FIGS. 4 and 5). For the thickness of the thinnest portion, the minimum possible value is determined from the viewpoint of material strength. On the other hand, the thickness of the disk-shaped portion on the side opposite to the offset direction (the right side in FIGS. 4 and 5) is thicker than the portion on the same side as the offset direction. From the standpoint of dead volume, the inclination of the top surface 51 with respect to the annular groove 55 puts the portion of the disk-shaped portion on the side opposite to the offset direction in an unfavorable situation. In other words, in the configuration in which the top surface 51 and the facing surface of the valve plate 9 are parallel at the top dead center of the piston 5, the thickness of a portion of the disk-shaped portion sandwiched between the annular groove and the top surface 51 is offset. Thick due to structure.

In the present embodiment, as shown in FIG. 6, the first non-sliding surface 53 located closer to the top surface 51 than the annular groove 55 (piston ring 12) is the first non-sliding surface 53 of the spherical sliding surface 52. , the gap G between the first non-sliding surface 53 of the piston 5 and the inner peripheral surface 4a of the cylinder 4 is reduced. can do. That is, the dead volume can be reduced without bringing the annular groove 55 (piston ring 12 ) closer to the top surface 51 .

The gap between the first non-sliding surface 53 of the piston 5 and the inner peripheral surface 4a of the cylinder 4 is one of the leakage paths of the compressed gas from the inside of the compression chamber 14 to the outside (inside the crankcase 3). be. Therefore, by forming the first non-sliding surface 53 so as to be located on the outer peripheral side of the spherical first imaginary extended curved surface 52V1, the first non-sliding surface 53 and the inner peripheral surface of the cylinder 4 Since the gap G with 4a becomes smaller, the amount of compressed air leakage in the compression stroke can also be reduced.

Further, in the present embodiment, as shown in FIG. 4, the angle formed by the offset-side non-sliding surface 531 of the first non-sliding surfaces 53 with respect to the perpendicular plane 5c of the piston 5 is the compression stroke. is formed on a curved surface (but not in contact with the inner peripheral surface 4a of the cylinder 4) that substantially coincides with the first cylindrical surface 531c orthogonal to the first plane 5e that is the maximum swing angle β1 of the non-offset side non-sliding The angle formed by the moving surface 532 with respect to the orthogonal surface 5c of the piston 5 is a curved surface that substantially coincides with the second cylindrical surface 532c that is perpendicular to the second plane 5f, which is the maximum swing angle β2 of the intake stroke (however, the inner surface of the cylinder 4 is curved). (non-contact with the peripheral surface 4a). According to this configuration, the first non-sliding surface 53 of the piston 5 can be brought closest to the inner peripheral surface 4 a of the cylinder 4 without contacting the inner peripheral surface 4 a of the cylinder 4 . That is, by forming the offset-side non-sliding surface 531 into a curved surface that approximately matches the first cylindrical surface 531c and forming the anti-offset-side non-sliding surface 532 into a curved surface that approximately matches the second cylindrical surface 532c, Dead volume can be minimized.

As described above, the reciprocating compressor 1 according to the first embodiment includes the cylinder 4 having the central axis Cc and the crankshaft 2 having the rotation axis Rs offset from the central axis Cc of the cylinder 4. , a piston 5 which forms a compression chamber 14 together with the cylinder 4 and reciprocates in the cylinder 4 , and one side of which is rotatably connected to the crankshaft 2 and the other side of which is fixed to the piston 5 so that the crankshaft 2 rotates. and a connecting rod 6 which, when actuated, makes an oscillating motion with respect to the cylinder 4 . The piston 5 has a top surface 51 forming part of the wall surface of the compression chamber 14 and an inner peripheral surface 4a of the cylinder 4 within a range determined according to the swing angle β of the connecting rod 6 with respect to the central axis Cc of the cylinder 4. and a first non-sliding surface 53 that connects the top surface 51 and the sliding surface 52 and avoids contact with the inner peripheral surface 4a of the cylinder 4. there is At least part of the first non-sliding surface 53 is closer to the inner peripheral surface 4a of the cylinder 4 than the first imaginary extended curved surface 52V1 that virtually extends the sliding surface 52 toward the top surface 51 side. It is located.

According to this configuration, by offsetting the crankshaft 2 with respect to the cylinder 4, it is possible to reduce the swing angle β in the compression stroke of the piston 5, and the first non-sliding By forming at least part of the surface 53 on the outer peripheral side (diameter direction outer side) of the first imaginary extended curved surface 52V1, the first non-sliding surface 53 of the piston 5 and the inner peripheral surface 4a of the cylinder 4 The gap G between them becomes smaller. Therefore, the dead volume of the compression chamber 14 can be reduced while reducing the side force acting between the piston 5 and the cylinder 4 during the compression stroke. In addition, since the gap G between the first non-sliding surface 53 of the piston 5 and the inner peripheral surface 4a of the cylinder 4 is reduced, leakage of compressed gas from the compression chamber 14 through the gap G is prevented. can be suppressed.

Further, in the reciprocating compressor 1 according to the present embodiment, the entire first non-sliding surface 53 is positioned closer to the inner peripheral surface 4a of the cylinder 4 than the first imaginary extended curved surface 52V1. According to this configuration, the gap G between the first non-sliding surface 53 of the piston 5 and the inner peripheral surface 4a of the cylinder 4 is reduced over the entire circumference, so the dead volume of the compression chamber 14 is further reduced. In addition, leakage of the compressed gas from the compression chamber 14 can be further suppressed.

In the reciprocating compressor 1 according to the present embodiment, the rotation axis (the central axis Cb of the bearing 7) of the large end 62 side (one side) of the connecting rod 6 and the central axis 5b of the piston (the connecting rod The piston 5 is asymmetrical with respect to a plane including the center line Cr connecting the large end 62 side (one side) and the small end 63 side (the other side) of the piston 6 . According to this configuration, a piston having a shape corresponding to the asymmetrical rocking motion of the piston 5 and the connecting rod 6 with respect to the cylinder 4 due to the offset structure can be configured.

Further, in the reciprocating compressor 1 according to the present embodiment, the piston ring 12 is attached to the outer peripheral surface of the piston 5 , and the piston ring 12 is arranged in the offset direction of the rotation axis Rs of the crankshaft 2 with respect to the central axis Cc of the cylinder 4 . is inclined with respect to the top surface 51 so as to approach the top surface 51 of the piston 5 as it goes in the same direction as . According to this configuration, the airtightness of the compression chamber 14 by the piston ring 12 can be ensured in the offset structure.

[Second embodiment]
Next, a second embodiment of the reciprocating compressor of the present invention will be described with reference to FIG. FIG. 7 is a diagram showing a piston fitted with a piston ring and its peripheral structure in a second embodiment of the reciprocating compressor of the present invention. In FIG. 7, parts having the same reference numerals as those shown in FIGS. 1 to 6 are the same parts, so detailed description thereof will be omitted.

The second embodiment of the reciprocating compressor of the present invention shown in FIG. 7 differs from the first embodiment in that the shape of the second non-sliding surface 54A of the outer peripheral surface of the piston 5A is different. That is. Specifically, the second non-sliding surface 54 of the piston 5 according to the first embodiment is a second virtual extended curved surface obtained by virtually extending the spherical sliding surface 52 toward the connecting rod 6 side. 52V2 (see FIG. 4). On the other hand, the second non-sliding surface 54A of the piston 5A according to the present embodiment is formed as a curved surface located on the outer peripheral side (diameter direction outside) of the second imaginary extended curved surface 52V2. That is, when the piston 5A is arranged in the cylinder 4, the entire second non-sliding surface 54A is closer to the inner peripheral surface of the cylinder 4 than the second virtual extended curved surface 52V2 of the spherical sliding surface 52. It is formed so as to be located near 4a. As a result, the area in which the gap between the second non-sliding surface 54A of the piston 5A and the inner peripheral surface 4a of the cylinder 4 becomes smaller increases than in the first embodiment.

In the reciprocating compressor according to the second embodiment described above, similarly to the first embodiment, by offsetting the crankshaft 2 with respect to the cylinder 4, the swing angle of the piston 5A during the compression stroke is It is possible to reduce β, and by forming at least a part of the first non-sliding surface 53 of the piston 5A on the outer peripheral side (diameter direction outside) of the first virtual extended curved surface 52V1, The gap G between the first non-sliding surface 53 of the piston 5A and the inner peripheral surface 4a of the cylinder 4 becomes smaller. Therefore, the side force acting between the piston 5A and the cylinder 4 during the compression stroke can be reduced, and the dead volume of the compression chamber 14 can be reduced. Leakage of compressed gas can be suppressed.

Further, the piston 5A in the reciprocating compressor according to the present embodiment extends from the sliding surface 52 to the opposite side of the top surface 51, and has a shape that avoids contact with the inner peripheral surface 4a of the cylinder 4. and a non-sliding surface 54A. At least part of the second non-sliding surface 54A is closer to the inner peripheral surface 4a of the cylinder 4 than the second virtual extended curved surface 52V2, which virtually extends the sliding surface 52 to the opposite side of the top surface 51. Located in

According to this configuration, at least a part of the second non-sliding surface 54A is formed on the outer peripheral side (diameter direction outside) of the second imaginary extended curved surface 52V2, thereby providing the second non-sliding surface of the piston 5A. Since the gap between the moving surface 54A and the inner peripheral surface 4a of the cylinder 4 is reduced, gas leakage from the compression chamber 14 during the compression stroke can be further suppressed.

Further, in the reciprocating compressor according to the present embodiment, the entire second non-sliding surface 54A of the piston 5A is positioned closer to the inner peripheral surface 4a of the cylinder 4 than the second imaginary extended curved surface 52V2. . According to this configuration, since the gap between the second non-sliding surface 54A of the piston 5A and the inner peripheral surface 4a of the cylinder 4 becomes small over the entire circumference, leakage of compressed gas from the compression chamber 14 can be prevented. can be further suppressed.

[Third Embodiment]
Next, a third embodiment of the reciprocating compressor of the present invention will be described with reference to FIG. FIG. 8 is a diagram showing a piston fitted with a piston ring and its peripheral structure in a third embodiment of the reciprocating compressor of the present invention. In FIG. 8, parts having the same reference numerals as those shown in FIGS. 1 to 7 are the same parts, and detailed description thereof will be omitted.

The third embodiment of the reciprocating compressor of the present invention shown in FIG. 8 differs from the first embodiment in that the shape of the first non-sliding surface 53B of the outer peripheral surface of the piston 5B is different. is. The first non-sliding surface 53 of the piston 5 according to the first embodiment is located on the outer peripheral side (radial direction outer side) of the first imaginary extended curved surface 52V1 of the sliding surface 52 whose entirety (entire circumference) is spherical. ) (see FIG. 4). On the other hand, the first non-sliding surface 53B of the piston 5B according to the second embodiment is formed so that only a part thereof is located on the outer peripheral side of the first imaginary extended curved surface 52V1. .

Specifically, of the first non-sliding surface 53B of the piston 5B, the counter-offset side located on the opposite side (right side in FIG. 8) to the offset direction of the crankshaft 2 (left direction in FIG. 8) Only the non-sliding surface 532 is formed so as to be located on the outer peripheral side of the first imaginary extended curved surface 52V1 of the sliding surface 52 . On the other hand, among the first non-sliding surfaces 53B, an offset-side non-sliding surface 531B located on the same side as the offset direction (left side in FIG. It is formed into a curved surface that coincides with the Due to the inclination of the top surface 51 with respect to the piston ring 12, the volume of the gap G between the non-offset side non-sliding surface 532 of the first non-sliding surface 53B and the inner peripheral surface 4a of the cylinder 4 is offset. It is larger than the volume of the gap G between the side non-sliding surface 531B and the inner peripheral surface 4a of the cylinder 4. In other words, the non-offset side non-sliding surface 532 causes an increase in dead volume more than the offset side non-sliding surface 531B. Therefore, in the present embodiment, the gap G between the non-offset side non-sliding surface 532 and the inner peripheral surface 4a of the cylinder 4 is made small.

In the reciprocating compressor according to the third embodiment described above, similarly to the first embodiment, by offsetting the crankshaft 2 with respect to the cylinder 4, the swing angle of the piston 5B during the compression stroke is It is possible to reduce β, and by forming at least a part of the first non-sliding surface 53B of the piston 5B on the outer peripheral side (diameter direction outside) of the first virtual extended curved surface 52V1, The gap G between the first non-sliding surface 53B of the piston 5B and the inner peripheral surface 4a of the cylinder 4 is reduced. Therefore, the side force acting between the piston 5B and the cylinder 4 during the compression stroke can be reduced, and the dead volume of the compression chamber 14 can be reduced. Leakage of compressed gas can be suppressed.

Further, in the reciprocating compressor according to the present embodiment, the first non-sliding surface 53B of the piston 5B is located on the side opposite to the offset direction of the rotation axis Rs of the crankshaft 2 with respect to the central axis Cc of the cylinder 4. Only the non-offset side non-sliding surface 532 (portion) located at is located closer to the inner peripheral surface 4a of the cylinder 4 than the first imaginary extended curved surface 52V1. According to this configuration, it is possible to reduce the amount of material used for manufacturing the piston 5B while reducing the dead volume of the compression chamber 14 and suppressing gas leakage from the compression chamber 14 .

[Fourth Embodiment]
Next, a fourth embodiment of the reciprocating compressor of the present invention will be described with reference to FIGS. 9 to 12. FIG. FIG. 9 is a schematic sectional view showing a fourth embodiment of the reciprocating compressor of the present invention. FIG. 10 is a diagram showing a piston fitted with a piston ring and its peripheral structure in a fourth embodiment of the reciprocating compressor of the present invention. FIG. 11 is a perspective view showing a single piston in the fourth embodiment of the reciprocating compressor of the present invention. FIG. 12 is an explanatory diagram showing dead volume in the fourth embodiment of the reciprocating compressor of the present invention. 9 to 12, the parts having the same reference numerals as those shown in FIGS. 1 to 8 are the same parts, and detailed description thereof will be omitted.

The fourth embodiment of the reciprocating compressor of the present invention shown in FIG. 9 differs from the first embodiment in that the piston 5C does not have a piston ring. Specifically, as shown in FIGS. 10 and 11, the piston 5C of the present embodiment has an annular groove 55 (see FIG. 5) formed on the outer peripheral surface unlike the piston 5 of the first embodiment. It is a configuration that is not As shown in FIG. 11, a valley line 56 (broken line in FIG. 11) as a boundary between the sliding surface 52 and the first non-sliding surface 53 appears on the outer peripheral surface of the piston 5C over the entire circumference. ing. On the other hand, in the piston 5 of the first embodiment, due to the formation of the annular groove 55, the valley line 56 (broken line in FIG. 5) as the boundary between the sliding surface 52 and the first non-sliding surface 53 is partially only appear. Other configurations and structures of the piston 5C of the present embodiment are the same as those of the first embodiment.

As described above, one cause of dead volume is the gap between the outer peripheral surface of the piston 5C and the inner peripheral surface 4a of the cylinder 4 shown in FIG. In this embodiment, the gap between the piston 5C and the cylinder 4 is sealed by line contact between the sliding surface 52 of the piston 5C and the inner peripheral surface 4a of the cylinder 4. As shown in FIG. Therefore, when the piston 5C is positioned at the top dead center, the top surface 51 is closer to the top surface 51 than the portion (annular portion) where the spherical sliding surface 52 of the piston 5C and the cylindrical inner peripheral surface 4a of the cylinder 4 contact. A gap G between the outer peripheral surface (a part of the sliding surface 52 and the first non-sliding surface 53) of the piston 5C located at , and the inner peripheral surface 4a of the cylinder 4 is one factor of the dead volume. A gap between the outer peripheral surface of the piston 5C and the inner peripheral surface 4a of the cylinder 4 is one of the leakage paths of the compressed gas from the inside of the compression chamber 14 to the outside (inside the crankcase 3).

In the reciprocating compressor according to the fourth embodiment described above, similarly to the first embodiment, by offsetting the crankshaft 2 with respect to the cylinder 4, the swing angle of the piston 5C during the compression stroke is It is possible to reduce β, and by forming at least a part of the first non-sliding surface 53 of the piston 5C on the outer peripheral side (diameter direction outside) of the first virtual extended curved surface 52V1, The gap G between the first non-sliding surface 53 of the piston 5C and the inner peripheral surface 4a of the cylinder 4 becomes smaller. Therefore, the side force acting between the piston 5C and the cylinder 4 during the compression stroke can be reduced, and the dead volume of the compression chamber 14 can be reduced. Leakage of compressed gas can be suppressed.

Further, the reciprocating compressor according to the present embodiment has a configuration in which the piston ring 12 is not attached to the outer peripheral surface of the piston 5C. According to this configuration, it is possible to simplify the configuration of the reciprocating compressor while reducing the dead volume of the compression chamber 14 and suppressing gas leakage from the compression chamber 14 .

[others]
The present invention is not limited to the first to fourth embodiments described above, and includes various modifications. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. For example, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

For example, in the above-described first to fourth embodiments, the sliding surfaces 52 of the

pistons

5, 5A, 5B, and 5C are spherical. However, if the sliding surface of the piston can smoothly oscillate and reciprocate within the cylinder 4, the curved surface that can be geometrically defined other than a spherical shape, for example, a curved surface approximating a spherical surface. can also be adopted.

In addition, in the first to fourth embodiments, the

pistons

5, 5A, 5B, 5C have shown the configuration examples in which the second non-sliding surfaces 54, 54A are provided. However, it is also possible for the piston to have no outer peripheral surface (second non-sliding surface) on the connecting rod 6 side of the sliding surface 52 . That is, it is possible to configure the outer peripheral surface of the piston only with the sliding surface 52 and the first non-sliding surfaces 53, 53B.

Further, in the second embodiment, an example of a configuration in which the entire second non-sliding surface 54A of the piston 5A is formed on the outer peripheral side (radial direction outer side) of the second imaginary extended curved surface 52V2 is shown. . However, a configuration is also possible in which only a part of the second non-sliding surface is formed on the outer peripheral side of the second imaginary extended curved surface 52V2.

Further, in the third embodiment, of the first non-sliding surface 53B of the piston 5B, only the anti-offset side non-sliding surface 532 (the right side portion in FIG. 8) is formed into the first imaginary extended curved surface 52V1. 8, and the offset-side non-sliding surface 531B (the left-hand portion in FIG. 8) is formed into a curved surface that coincides with the first imaginary extended curved surface 52V1. However, of the first non-sliding surfaces of the piston, only the offset-side non-sliding surface is formed on the outer peripheral side of the first imaginary extended curved surface 52V1, while the anti-offset-side non-sliding surface is formed on the first imaginary curved surface 52V1. It is also possible to form a curved surface that coincides with the extended curved surface 52V1. Also in this case, it is possible to arbitrarily set the position of the ridgeline, which is the connecting portion between the offset-side non-sliding surface and the anti-offset-side non-sliding surface.

1... reciprocating compressor, 2... crankshaft, 4... cylinder, 4a... inner peripheral surface, 5, 5A, 5B, 5C... piston, 6... connecting rod, 12... piston ring, 14... compression chamber, 51... top Surface 52 Sliding surface 52V1 First imaginary extended curved surface 52V2 Second imaginary extended

curved surface

53, 53B First non-sliding surface 532 Anti-offset side non-sliding surface (offset

direction

54, 54A... second non-sliding surface, Cc... center axis, Rs... rotation axis, β... rocking angle, Cb... rotation axis, Cr... center line

Claims

a cylinder having a central axis;
a crankshaft having an axis of rotation offset with respect to the central axis of the cylinder;
a piston that forms a compression chamber together with the cylinder and reciprocates within the cylinder;
a connecting rod whose one side is rotatably connected to the crankshaft and whose other side is fixed to the piston and which swings with respect to the cylinder by the rotational movement of the crankshaft;
The piston is
a top surface forming part of the wall surface of the compression chamber;
a sliding surface that slides on the inner peripheral surface of the cylinder within a range determined according to the swing angle range of the connecting rod with respect to the central axis of the cylinder;
a first non-sliding surface that connects the top surface and the sliding surface and has a shape that avoids contact with the inner peripheral surface of the cylinder;
At least part of the first non-sliding surface is positioned closer to the inner peripheral surface of the cylinder than a first imaginary extended curved surface obtained by virtually extending the sliding surface toward the top surface. A reciprocating compressor that is.
A reciprocating compressor according to claim 1,
A reciprocating compressor according to claim 1, wherein the first non-sliding surface is entirely located closer to the inner peripheral surface of the cylinder than the first imaginary extended curved surface.
A reciprocating compressor according to claim 1,
Of the first non-sliding surface, only the portion located on the side opposite to the offset direction of the rotation axis of the crankshaft with respect to the central axis of the cylinder is located on the cylinder relative to the first imaginary extended curved surface. A reciprocating compressor located near the inner peripheral surface.
A reciprocating compressor according to claim 1,
The piston further has a second non-sliding surface extending from the sliding surface to the opposite side of the top surface and shaped to avoid contact with the inner peripheral surface of the cylinder,
At least part of the second non-sliding surface is closer to the inner peripheral surface of the cylinder than a second imaginary extended curved surface that virtually extends the sliding surface to the opposite side of the top surface. A reciprocating compressor that is located.
A reciprocating compressor according to claim 4,
A reciprocating compressor, wherein the second non-sliding surface is positioned closer to the inner peripheral surface of the cylinder than the second imaginary extended curved surface.
A reciprocating compressor according to claim 1,
A reciprocating compressor, wherein the piston is asymmetrical with respect to a plane including a rotation axis of the one side of the connecting rod and a center line connecting the one side and the other side of the connecting rod.
A reciprocating compressor according to claim 1,
A piston ring is attached to the outer peripheral surface of the piston,
The piston ring is inclined with respect to the top surface so as to approach the top surface of the piston in the same direction as the offset direction of the rotation axis of the crankshaft with respect to the central axis of the cylinder. reciprocating compressor.