JP7576937B2 - Compressor - Google Patents

Description

The present invention relates to a compressor.

Conventionally, in reciprocating compressors that compress fluids, a structure is known in which a valve plate with a suction valve is attached to one end face of the cylinder. In this structure, when the pressure inside the cylinder falls below the pressure of the suction fluid while the piston is descending, the pressure difference causes the suction valve to open, and the suction fluid is drawn into the cylinder.

In other words, the suction valve repeatedly opens and closes with each reciprocating movement of the piston. This creates the problem of noise being unavoidable when the suction valve plate hits the valve seat that regulates the amount of opening (lift). This problem becomes more serious as the compressor capacity increases.

In addition, in reciprocating compressors, the smaller the volume of the gap remaining between the top surface of the piston and the valve plate surface at the end of the cylinder when the piston reaches top dead center, the greater the expected efficiency. However, if the gap is too small, there is a risk of contact due to thermal expansion of the components and processing variations, so there is a problem that a certain amount of gap must be provided.

This problem of clearance volume becomes particularly severe in reciprocating compressors that use the oscillating piston system, in which the piston itself oscillates and there is no bearing at the small end of the connecting rod.

In the oscillating piston system, unnecessary wear of the sliding parts is reduced by making the piston head a sphere whose diameter is approximately the same as the cylinder's inner diameter, rather than a cylinder whose piston head is approximately the same as the cylinder's inner diameter.

However, if the top surface is made flat along the inner surface of the cylinder and the side is made into a spherical piston head, the top surface will be circular and smaller than the cylinder diameter, meaning that the left and right ends of the top surface of the piston will protrude upward before and after the position of the piston at top dead center. This requires a larger gap than with a normal piston system.

As an example of a compressor that aims to extend the life of the suction valve by reducing wear on the valve, Patent Document 1 describes a suction valve receiving member that has an inclined upper surface on a stepped portion of the cylinder and is made of a self-lubricating material with a low coefficient of friction, and that abuts against the suction valve.

As an example of an inexpensive yet highly reliable reciprocating compressor, Patent Document 2 describes a spherical piston that slides back and forth inside a cylinder, and oscillates during the suction stroke, causing the piston spherical surface to be recessed at the location where it makes sliding contact with the inner circumferential surface of the cylinder, forming a suction port for sucking fluid into the compression chamber from the piston rod side.

JP 2005-291021 A Japanese Unexamined Patent Publication No. 62-253971

As mentioned above, reciprocating compressors are required to solve two problems: reducing suction valve noise and reducing the gap volume of the oscillating piston system.

Patent Document 1, which is one of the technologies for reducing noise from the suction valve plate and wear caused by collision of the valve plate, shows a structure in which a suction valve receiving member with a low friction coefficient is provided between the suction valve plate and the recess on the cylinder side that receives it, reducing wear on the valve plate and mitigating noise caused by collision. It also states that by adopting this structure, it is possible to eliminate the suction valve receiving member that was previously positioned opposite the suction valve plate, making it possible to reduce the gap volume accordingly.

However, when attempting to apply this type of structure to an oscillating piston, the reduction in the gap volume is limited to the space occupied by the suction valve receiver, so the reduction effect is insufficient, which remains an issue.

Next, Patent Document 2 describes a structure for a reciprocating compressor using a rocking piston system in which there is no intake valve on the valve plate, the piston is spherical, a recess is provided on part of the side, and air is drawn in from inside the crankcase using the rocking motion of the piston without providing an intake valve plate.

The structure of Patent Document 2 provides a fundamental solution to the noise that accompanies the opening and closing of the suction valve plate, but the recess in the spherical piston in this structure reduces the area that receives the pressure of the reciprocating inertial force that acts in the direction of pressing the piston against the inner circumferential surface of the cylinder. This problem creates new problems such as seizure and wear due to insufficient lubrication when the piston slides.

In addition, when attempting to apply the structure of Patent Document 2 to an oil-lubricated reciprocating compressor that operates by supplying lubricating oil to the contact surface between the piston and cylinder, there is a problem in that oil droplets are sucked in when air is sucked in through the recess on the side of the piston. The oil droplets sucked into the top surface of the piston are carbonized by the heat of compression and adhere to the periphery of the plate, causing a problem in that they impair the sealing performance of the valve. Furthermore, there is a problem in that the lubricating oil itself is discharged and lost along with the fluid, resulting in increased oil consumption.

Considering this point of view, it can be said that the structure of Patent Document 1, in which the suction valve is provided on the valve plate side, has an advantage in terms of the placement of the suction port.

However, in terms of reducing the clearance volume mentioned above, Patent Document 2 employs a structure in which the concave shape of the ceiling surface is made closer to the spherical shape of the piston in order to reduce the clearance volume that remains between the piston and the valve plate surface when the spherical oscillating piston reaches top dead center.

Based on the above two technologies, it is believed that in a reciprocating compressor using a rocking piston system, if the suction valve structure of Patent Document 1 can be applied to the valve plate shape of Patent Document 2, it will be possible to achieve both noise reduction and efficiency improvement.

However, when the valve plate side is concave as in Patent Document 2, it is difficult to provide a suction valve on the piston side of the valve plate as in Patent Document 1. This is because the surface of the valve plate that comes into contact with the suction valve plate when the valve is closed is generally polished for sealing purposes, but when the outer periphery of the valve plate is made to protrude, it is impossible to polish the inner periphery with a general flat lapping machine.

Due to these circumstances, it is necessary to solve the above two problems using different methods.

The present invention provides a reciprocating compressor with a spherical oscillating piston that can reduce the impact noise caused by the opening and closing of the suction valve and reduce the clearance volume.

The present invention includes a number of means for solving the above problems. One example is a compressor that compresses a fluid by a piston reciprocating within a cylinder, the piston is of an oscillating type that reciprocates while oscillating within the cylinder, the tip of the piston is approximately flat, the side of the piston is a spherical surface with a diameter smaller than the inner diameter of the cylinder, and a ring-shaped member having a convex portion that protrudes radially outward is fitted onto one of the end faces of the cylinder on the side of a valve plate that closes the end of the cylinder , and the ring-shaped member is positioned so as to fill a gap between the piston and the cylinder .

According to the present invention, it is possible to reduce the impact noise caused by the opening and closing of the suction valve and to reduce the clearance volume. Other issues, configurations, and effects will be made clear by the explanation of the following examples.

1 is a diagram showing an example of the overall configuration of a compressor according to an embodiment of the present invention; FIG. 2 is a diagram showing a configuration example of a compressor body in the embodiment. FIG. 4 is a diagram showing a configuration example of a piston in an embodiment. FIG. 2 is a diagram showing an example of a cross-sectional configuration of a piston in an embodiment. 4 is an enlarged cross-sectional view of the upper surface of a cylinder of the compressor body in the embodiment when the piston is at the top dead center. FIG. 2 is an enlarged cross-sectional view of the compressor body in the embodiment, seen from the suction valve side when the piston is at top dead center. FIG. FIG. 2 is an exploded view of a compressor body according to the embodiment. FIG. 11 is an enlarged cross-sectional view of an upper surface of a cylinder in a compressor body according to another embodiment of the present invention when a piston is at top dead center. 10A and 10B are diagrams showing other forms of the ring-shaped member provided in the compressor body in the embodiment.

An embodiment of the compressor of the present invention will be described with reference to Figs. 1 to 9.

First, the compressor of the present invention can be applied to various compressors that can employ a rocking piston system among compressors that compress various fluids such as air and refrigerants, and there are no particular limitations on the type, model, or use.

In addition, in the drawings used in this specification, identical or corresponding components are given the same or similar reference numerals, and repeated explanations of these components may be omitted.

The overall configuration of the compressor of this embodiment will be described below with reference to Figures 1 and 2. Figure 1 is a schematic diagram of the compressor of this embodiment. Also, Figure 2 is a diagram showing the internal structure of the compressor body 1 in Figure 1.

The compressor 10 shown in FIG. 1 includes a compressor body 1, an electric motor 2 that drives the compressor body 1, and a tank 3 for storing the fluid discharged by the compressor body 1.

The compressor body 1 compresses the fluid, and as shown in FIG. 2, its internal structure includes a crankcase 21, one cylinder 22 protruding vertically from the crankcase 21, a valve plate 26 that closes the end (upper end) of the cylinder 22, a cylinder head 23, and the crankcase 21 that supports the crankshaft 24 in the center so that it can rotate.

In the compressor body 1, the crankshaft 24 inside the crankcase 21 rotates, applying a rotational force to one end of the connecting rod 32, causing the piston 33 installed inside the cylinder 22 to reciprocate vertically, resulting in the fluid being sucked in from outside the cylinder 22, compressed, and discharged into the tank 3.

In addition, for the sake of simplicity, in Figures 1 and 2, the compressor is shown as a one-cylinder, one-stage compressor with only one pair of pistons and cylinders, but it may also be a compressor with multiple pistons and cylinders arranged in series or radially around the crankshaft.

In the compressor body 1, the crankshaft 24 is arranged parallel to the rotating shaft of the electric motor 2 and is fixed on the tank 3. In addition, a compressor pulley 4 is fixed to the crankshaft 24, and an electric motor pulley 5 is fixed to the rotating shaft of the electric motor 2. The compressor pulley 4 attached to the compressor body 1 has blades, and as it rotates, it generates cooling air toward the compressor body 1, promoting heat dissipation from the compressor body 1.

A transmission belt 6 is wound around the compressor pulley 4 and the electric motor pulley 5 to transmit power between the compressor pulley 4 and the electric motor pulley 5. As a result, in accordance with the rotation of the electric motor 2, the crankshaft 24 of the compressor body 1 is rotated via the electric motor pulley 5, the transmission belt 6, and the compressor pulley 4, and the compressor body 1 compresses the fluid.

In FIG. 1, for the sake of simplicity, the compressor body 1 is connected to the electric motor 2 via a transmission belt 6, but the crankshaft 24 of the compressor body 1 and the rotating shaft of the electric motor 2 may be directly joined using a coupling or other connecting means to integrate the two.

Next, the surrounding structure of the piston will be explained using FIG. 2. The piston 33 shown in FIG. 2 is an oscillating piston type in which the piston 33 is integral with the connecting rod 32. In this type, the piston 33 reciprocates while oscillating within the cylinder 22 as the crankshaft 24 rotates.

The piston 33 is also positioned so that the horizontal position of its tip center 33d is offset to the left or right from the center of the rotation shaft 24a that rotates the piston 33.

Next, the detailed structure of the piston 33 and the connecting rod 32 will be described with reference to Figures 3 and 4. Figure 3 shows an example of the piston's configuration, and Figure 4 shows an example of the cross-sectional configuration of the piston.

The piston 33 shown in Figures 3 and 4 is a separate part from the connecting rod 32 that supports the piston 33, and at least the outer peripheral surface 33a that contacts the inner peripheral side of the cylinder 22 and the upper surface 33c on the valve plate 26 side are made of a resin having wear resistance. In this embodiment, the piston 33 is made of a resin having excellent wear resistance, except for the piston insert 41 described later.

An example of a resin material with excellent abrasion resistance is one in which polytetrafluoroethylene (PTFE) is used as the main body of the piston 33. Furthermore, when the thermal expansion coefficient is taken into consideration, the resin material for the piston 33 may be polyphenylene sulfide (PPS), etc.

The outer circumferential surface 33a of the piston 33 is a sphere with a diameter smaller than the inner diameter of the cylinder 22. In particular, it is desirable for the diameter to be slightly smaller.

Furthermore, the top surface 33c of the tip of the piston 33 is inclined with respect to the central axis 33f of the piston 33, and is generally flat except for the recessed portion 33e. The generally flat top surface 33c is generally parallel to the bottom surface of the valve plate 26 when the piston 33 is at top dead center. Note that "approximately" here means that it is sufficient to be considered substantially flat or parallel when viewed macroscopically, and it does not have to be completely flat or parallel.

In such a piston 33, a piston ring 34 is used as a seal ring that seals the compressed gas. This piston ring 34 is fitted with a certain gap into a ring (annular) groove 33b provided on the outer circumferential surface 33a of the piston 33. Note that it is possible to configure the piston 33 without using the piston ring 34 and the ring groove 33b.

As shown in FIG. 4, the piston 33 is molded with a piston insert 41 made of a metal such as an aluminum alloy embedded inside. The piston insert 41 has an edge 41a that is shaped to fit into the piston 33 in the circumferential direction so that it will not come out even if the piston 33 is subjected to a pulling load toward the cylinder head 23 due to reciprocating inertia force or friction force.

This piston insert 41 is fastened (fixed) to the connecting rod 32 with a screw 35 in a direction perpendicular to the crankshaft 24 from the crankcase 21 side.

As shown in Figure 4, the piston insert 41 described above is dish-shaped with the cylinder head 23 at the bottom, and the seating surface of the connecting rod 32 also has a recess 32b formed at a position corresponding to the recess in the center of the dish shape of the piston insert 41. With this structure, a hollow portion 41b is formed between the bottom surface of the piston insert 41 and the top surface of the connecting rod 32, thereby reducing the weight.

Next, the end face structure of the cylinder 22 will be described with reference to Figures 5 and 6. Figure 5 shows an enlarged view of the periphery of the piston 33 when the piston 33 reaches top dead center in the compressor 10 of Figure 2. Figure 6 shows a cross-sectional view of the compressor 10 in the same state in the crankshaft direction.

As shown in FIG. 5, the cylinder 22 has an annular groove 22b on the end face on the valve plate 26 side, and a ring-shaped member 51 is fitted into the annular groove 22b.

This ring-shaped member 51 is required to have dimensional precision to maintain a small gap with the piston outer circumferential surface 33a while being constantly exposed to compression heat during compression operation. It also needs to have the strength and cushioning to withstand repeated collisions with the suction valve plate 26a provided on the valve plate 26.

For this reason, it is desirable to construct the ring member 51 from a material that is heat resistant and has a small coefficient of thermal expansion, such as resin, and materials such as engineering plastics that have excellent coefficients of thermal expansion and high-temperature strength are particularly suitable. For example, phenolic resin and polyphenylene sulfide (PPS) are suitable. These resin materials can be injection molded, making them convenient for constructing the ring-shaped member 51, which has a complex shape and is difficult to machine.

It is desirable that the diameter of the inner circumference 51a of the ring-shaped member 51, in part or in its entirety, is smaller than the inner diameter of the cylinder 22, and that it protrudes inward from the cylinder inner wall surface 22a.

Furthermore, it is desirable that the inner periphery 51a of this ring-shaped member 51 has a small gap between it and the outer periphery 33a of the piston even when the piston 33 reaches top dead center, so that problems such as wear due to contact do not occur. In addition, when the spherical piston 33 reaches top dead center, the gap volume surrounded by the cylinder inner wall surface 22a, the valve plate 26, the outer periphery 33a of the piston, and the top surface 33c is narrowed.

Next, the detailed shape of the ring-shaped member 51 will be described using the development views of Figures 6 to 9. Figure 7 is a development view of the compressor body. Figure 8 is an enlarged cross-sectional view of the upper surface of the cylinder when the piston is at top dead center in a compressor body in another configuration of the embodiment. Figure 9 is a diagram showing the short form of the ring-shaped member.

As shown in FIG. 6, the ring-shaped member 51 has a recess 51b on its circumference where the thickness in the direction in which the cylinder 22 expands and contracts is partially thin, and a protrusion 51c provided in the recess 51b.

Of these, the recess 51b is inclined toward the center of the cylinder 22 and is arranged to be interposed between the tip of the suction valve plate 26a and the cylinder 22. The recess 51b of the ring-shaped member 51 is effective in reducing noise caused by collision with the suction valve plate 26a provided on the valve plate 26, and its depth dimension h and shape are important.

For example, as shown in FIG. 6, if the suction valve is composed only of the suction valve plate 26a provided on the valve plate 26, the depth dimension of the recess 51b can be determined so that the suction valve plate 26a comes into contact with the recess 51b only when it is open. Furthermore, as shown in FIG. 6, if the recess 51b is inclined toward the center of the cylinder 22, the impact when the suction valve plate 26a collides can be softened.

The protrusion 51c protrudes from the recess 51b radially outward of the ring-shaped member 51, and serves to increase the area that receives the suction valve plate 26a of the valve plate 26. There are no particular limitations on its shape, and it is desirable for it to have a depth and shape that allows it to come into contact with the protrusion 51c only when the suction valve plate 26a is open.

The suction valve plate 26a must be long enough so that its end is positioned radially outward of the cylinder 22 relative to the inner diameter of the cylinder 22 and is in contact with the ring-shaped member 51. This prevents the suction valve plate 26a from being supported by only the bolts on one side of the cylinder 22 in FIG. 7, resulting in a cantilever structure that constantly vibrates, and suppresses vibration.

In the embodiment shown in Figure 6 etc., the suction valve plate 26a is configured as a single valve plate, but as shown in Figure 8, it is possible to configure the suction valve plate 26a to have a suction valve receiver 26b on the cylinder 22 side.

In the case of the embodiment shown in FIG. 8, the recess 51b of the ring-shaped member 51 is provided so as to be interposed between the suction valve receiver 26b provided on the valve plate 26 and the cylinder 22.

Also, when the suction valve is composed of a suction valve plate 26a and a suction valve receiver 26b as shown in FIG. 8, the recess 51b of the ring-shaped member may be in constant contact with the suction valve receiver 26b, or may be in contact only when the suction valve plate 26a is open. However, the former configuration has the advantage of preventing wear when the suction valve receiver 26b collides with the recess 51b of the ring-shaped member 51.

The shape of the ring-shaped member is not limited to the shapes shown in Figures 5 to 8. For example, the ring-shaped member 51A shown in Figure 9 has only a recess 51b at the position where it comes into contact with the suction valve plate 26a when it is open, and does not have a protrusion 51c. Even in such a shape, it is desirable that the recess 51b has a size and shape that allows it to come into contact with the recess 51b only when the suction valve plate 26a is open.

Although not shown in the figure, it is possible to provide only the convex portion 51c, no concave portion 51b, and a shape that contacts the upper surface of the ring-shaped member when the suction valve plate 26a is open. In such a shape, it is desirable to determine the shape and dimensions of the ring-shaped member so that the suction valve plate 26a contacts the upper surface of the ring-shaped member only when it is open.

Next, we will explain the effects of this embodiment.

In the compressor 10 of the present embodiment described above, which compresses a fluid by the reciprocating movement of the piston 33 inside the cylinder 22, the piston 33 is of an oscillating type that reciprocates while oscillating inside the cylinder 22, the tip of the piston 33 is substantially flat, the outer peripheral surface 33a of the piston 33 is a spherical surface with a diameter smaller than the inner diameter of the cylinder 22, and a ring-shaped member 51 is fitted to the end face of the cylinder 22 on the side of the valve plate 26 that closes the end of the cylinder 22, thereby filling the gap between the spherical piston 33 and the cylinder 22 at the top dead center and improving the volumetric efficiency. Also, a part of the ring-shaped member 51 can also serve as a valve receiver for the suction valve plate 26a, thereby reducing the impact noise accompanying the opening and closing of the suction valve plate 26a.

In addition, because part of, and even the entire inner diameter of, the ring-shaped member 51 is smaller than the inner diameter of the cylinder 22, the gap volume can be reduced more effectively, thereby further improving compression efficiency.

Furthermore, the ring-shaped member 51 has a recess 51b where the thickness in the direction in which the cylinder 22 expands and contracts is partially thinner, which minimizes the gap between the valve plate 26 and the ring-shaped member 51, maximizing the gap volume and more effectively receiving the suction valve plate 26a, thereby more effectively reducing noise.

In addition, the recess 51b is inclined toward the center of the cylinder 22, so that the suction valve plate 26a can be more effectively received when the suction valve plate 26a is opened and closed.

Furthermore, the ring-shaped member 51 has a convex portion 51c that protrudes radially outward, which increases the area that receives the suction valve plate 26a, thereby further softening the impact of the suction valve plate 26a and reducing noise. Also, by protruding radially outward, interference with the piston 33 can be avoided.

In addition, the horizontal position of the center 33d of the tip of the piston 33 is offset from the rotation axis 24a that rotates the piston 33, which makes it possible to suppress tilting of the piston ring 34 during the compression process and prevent deterioration of sealing performance.

Furthermore, the upper surface 33c is inclined with respect to the central axis 33f of the piston 33, and when the piston 33 is at top dead center, the upper surface 33c becomes approximately parallel to the valve plate 26, which makes it possible to minimize the gap volume and further improve the theoretical volumetric efficiency of the compressor body 1.

In addition, the ring-shaped member 51 is made of resin, particularly phenolic resin or polyphenylene sulfide, which means that it is made of a material with excellent thermal expansion coefficient and high-temperature strength, reducing problems such as wear of the ring-shaped member 51.

＜Other＞
The present invention is not limited to the above-mentioned embodiment, and various modifications and applications are possible. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to having all of the described configurations.

1...Compressor body 2...Electric motor 3...Tank 4...Compressor pulley 5...Electric motor pulley 6...Transmission belt 10...Compressor 21...Crankcase 22...Cylinder 22a...Cylinder inner wall surface 22b...Annular groove 23...Cylinder head 24...Crankshaft 24a...Rotary shaft 26...Valve plate 26a...Suction valve plate 26b...Suction valve receiver 32...Connecting rod 32b...Recess 33...Piston 33a...Piston outer circumferential surface (side surface)
33b... ring groove 33c... upper surface 33d... center 33e... recess 33f... central shaft 34... piston ring 35... screw 41... piston insert 41a... edge portion 41b... hollow portion 51, 51A... ring-shaped member 51a... inner circumference 51b... recess 51c... protrusion

Claims (10)

In a compressor that compresses a fluid by reciprocating a piston inside a cylinder,
The piston is of an oscillating type that reciprocates while oscillating within the cylinder,
The tip of the piston is substantially flat,
The side surface of the piston is a spherical surface with a diameter smaller than the inner diameter of the cylinder,
A ring-shaped member having a convex portion protruding radially outward is fitted to an end surface of the cylinder on the side of a valve plate that closes the end of the cylinder ,
The ring-shaped member is disposed so as to fill a gap between the piston and the cylinder . In a compressor that compresses a fluid by reciprocating a piston inside a cylinder,
The piston is of an oscillating type that reciprocates while oscillating within the cylinder,
The tip of the piston is substantially flat,
The side surface of the piston is a spherical surface with a diameter smaller than the inner diameter of the cylinder,
A ring-shaped member having a convex portion protruding radially outward is fitted to an end surface of the cylinder on the side of a valve plate that closes the end of the cylinder ,
The protrusion of the ring-shaped member also serves as a valve receiver for the valve plate . The compressor according to claim 1 or 2 ,
A portion of an inner diameter of the ring-shaped member is smaller than an inner diameter of the cylinder. 4. The compressor according to claim 3 ,
The ring-shaped member has an inner diameter that is smaller than the inner diameter of the cylinder as a whole. The compressor according to claim 1 or 2 ,
the ring-shaped member has a recess where a thickness in a direction in which the cylinder expands and contracts is partially thinner. 6. The compressor according to claim 5 ,
The recess is inclined toward the center of the cylinder. The compressor according to claim 1 or 2 ,
a horizontal position of a center of a tip of the piston is offset from a rotation axis that rotates the piston. The compressor according to claim 1 or 2 ,
The plane of the tip of the piston is inclined with respect to the central axis of the piston,
the plane is substantially parallel to the valve plate when the piston is at top dead center. The compressor according to claim 1 or 2 ,
The compressor, wherein the ring-shaped member is made of resin. 10. The compressor according to claim 9 ,
The compressor, wherein the ring-shaped member is made of phenol resin or polyphenylene sulfide.

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