JPH0517436B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas compression device that compresses or maintains pressure of gas using a piston inserted into a cylinder, such as a gas compressor, an air cylinder, a gas spring, or other gas pressure maintaining device. relates to a piston seal structure using piston rings.

In various gas compression devices in which a piston is inserted into a cylinder so that it can reciprocate and at least one of the chambers divided by the piston is used as a pressure chamber, the sliding surface of the piston must be airtightly sealed. There is. Piston rings are known as this type of seal structure, and since it is often not possible to supply lubricating oil to the sliding surfaces of the piston in this type of gas compression equipment, piston rings are made of polyimide mainly made of Teflon (trade name). A self-lubricating polymer material made of resin or the like is used.

However, piston rings made of self-lubricating polymer materials have a larger coefficient of thermal expansion than metal members such as cylinders and pistons, so they must be installed in the piston ring grooves, taking into account the expansion of the rings due to temperature rise during operation. In some cases, it is necessary to maintain a large gap at the cut portion along the circumferential direction of the piston ring, that is, at the abutment portion. Since such a gap causes leakage of compressed air, conventional piston rings have steps formed along the axial direction at both ends of the cut portion of the piston ring, and these steps overlap each other in the axial direction. A stepped opening is formed. However, even with such a stepped opening shape, air is likely to leak from the overlapped portion of the stepped portions, and the leakage becomes significant especially when the air pressure is high.

Accordingly, an object of the present invention is to provide a piston seal structure for a gas compression device that can completely prevent leakage from the stepped opening and maintain highly accurate airtightness.

That is, the present invention provides a tension ring whose diameter can be freely expanded between the inner circumferential surface of the piston ring and the bottom of the piston ring groove, and this tension ring is made of silicone rubber and has an annular shape continuous in the circumferential direction. In addition, the cross-sectional shape is semicircular or U-shaped with a flat outer surface and a curved inner surface, and the outer circumferential surface of this tension ring is brought into close contact with the inner circumferential surface of the piston ring to close the stepped joint opening. A gap is maintained between the inner peripheral surface of the tension ring and the bottom of the piston ring groove, and pressure gas is introduced into this gap to expand the diameter of the tension ring.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a sectional view showing the main parts of a known gas compressor. 1 is a cylinder made of aluminum subjected to hard alumite treatment, 2 is a cylinder head made of the same material as cylinder 1, and 3 is an inside view of cylinder 1. It shows an aluminum piston that reciprocates in the vertical direction shown in the figure.

A piston ring groove 4 is formed on the outer peripheral surface of the piston 3 over the entire circumference, and the groove bottom surface 4a of the piston ring groove 4 has a curved surface shape, so the groove 4 has a U-shaped cross section. . A piston ring 5 is fitted into the piston ring groove 4. The piston ring 5 is made of a self-lubricating synthetic resin such as polyimide resin mainly containing Teflon. As shown in FIG. 2, the piston ring 5 has a
It has step portions 5a and 5b which are superimposed on each other in the axial direction,
These stepped portions 5a and 5b are overlapped to form a stepped joint opening. The piston ring 5 has a rectangular cross-section, and its axial dimension, that is, the height _h1 , is smaller than the groove width l of the piston ring groove 4 (l>
h ₁ ) is formed. And the step portions 5a, 5b
In the case of the present embodiment, the heights are h ₁ /2.

A tension ring 6 is provided in the piston ring groove 4 between the piston ring 5 and the groove bottom 4a. tension ring 6
is made of silicone rubber and has a ring shape continuous in the circumferential direction, and its cross section is approximately semicircular or U-shaped. The outer diameter of the tension ring 6 is formed to match the inner diameter of the piston ring 5 or to be slightly larger than the inner diameter of the piston ring 5. A flat surface 6a is formed so as to be in close contact with the peripheral surface 5c. The height _h2 of this flat surface 6a is the height of the piston ring 5.
It is formed to be equal to or preferably smaller than h ₁ , but larger _than the height h ₁ /2 of the stepped portions 5a and 5b, and has the relationship h ₁ ≧h ₂ > h ₁ /2. ing. Further, a gap 7 is formed between the inner peripheral surface 6b of the tension ring 6 and the groove bottom surface 4a of the piston ring groove 4.

A fitting groove 8 is formed on the outer peripheral surface of the piston 3, and a bearing 9 made of a self-lubricating material is fitted into this fitting groove 8. This bearing 9
slides inside the cylinder 1 integrally with the piston 3. 10 is a compression chamber formed between the piston 3 and the cylinder head 2 side, 11 is an annular gap formed between the outer peripheral surface of the top of the piston 3 and the inner peripheral surface of the cylinder 1, and 12 is a compression chamber formed between the piston 3 and the cylinder head 2 side. An annular gap 13 surrounded by the inner peripheral surface of the cylinder, the piston ring 5, and the bearing 9 indicates a crank chamber.

The tension ring 6 having the above structure is fitted into the piston ring groove 4 before the piston 3 is fitted into the cylinder 1. Next, the piston ring 5 is fitted into the piston ring groove 4 so as to be located on the outer periphery of the tension ring 6. Then, the piston 3 is inserted into the cylinder 1 while reducing the diameter of the piston ring 5 and maintaining the outer diameter of the piston ring 5 to be approximately equal to the outer diameter of the piston 3.

When the piston 3 is inserted into the cylinder 1, the tension ring 6 attempts to return to its original state, and the flat outer peripheral surface 6a of the tension ring 6 comes into close contact with the inner peripheral surface 5c of the piston ring 5. Due to this close contact, the overlapping surfaces of the stepped portions 5a and 5b are closed by the tension ring 5. Note that during such close contact, the outer circumferential surface 5d of the piston ring 5 is pressed against the inner circumferential surface of the cylinder 1 by the expanding force of the tension ring 5, but it is desirable that this pressing force be extremely small in terms of reducing frictional force.

According to the configuration of such an embodiment, the piston 3
In the compression stroke in which the piston ring 5 is moved upward in the figure, the height _h1 of the piston ring 5 is smaller than the groove width l of the piston ring groove 4, and the outer circumferential surface 5d of the piston ring 5 is between the inner circumferential surface of the cylinder 1. Piston ring 5 due to frictional resistance generated in
The lower surface 5e of the piston ring groove 4 is in close contact with the lower surface 4b, and the upper surface 5f of the piston ring 5 is spaced apart from the upper surface 4c of the piston ring groove 4. The compressed gas generated in the compression chamber 10 flows into the gap 7 at the bottom of the groove through the annular gap 11 and between the upper surface 5f of the piston ring 5 and the upper surface 4c of the piston ring groove 4. Since the pressure within the gap 7 becomes high, the tension ring 6 receives back pressure on its inner surface due to this pressure and expands in diameter, and the outer circumferential surface 6a is pressed against the inner circumferential surface 5c of the piston ring 5. Therefore, the outer peripheral surface 6a of the tension ring 6 and the inner peripheral surface 5c of the piston ring 5 are brought into airtight contact. Furthermore, since sliding resistance occurs between the outer circumferential surface 5d of the piston ring 5 and the inner circumferential surface of the cylinder 1, the lower surface 5e of the piston ring 5 is brought into airtight contact with the lower surface of the piston ring groove. Since it forms a sealing surface, the high pressure gas in the gap 7 flows into the crank chamber 13.
There is no risk of it leaking to the outside. Since the outer circumferential surface 6a of the tension ring 6 covers the overlapping surface of the stepped portion of the piston ring 5, compressed gas will not leak from the overlapping surface of the stepped portions 5a and 5b.

Further, when the tension ring 6 pushes the piston ring 5, the outer peripheral surface 5d of the piston ring 5 is pressed against the inner peripheral surface of the cylinder 1 with an even force over the entire circumference. This pressing force improves the sealing performance between the piston ring outer circumferential surface 5d and the inner circumferential surface of the cylinder 1,
High pressure gas in the compression chamber 10 will not leak to the crank chamber 13 side. Furthermore, since the piston ring 5 is pressed against the cylinder inner circumferential surface with an even force over the entire circumference, uneven wear of the piston ring is prevented, and reliable airtightness can be maintained for a long period of time.

In the suction stroke in which the piston 3 is moved downward in the figure, when the pressure in the compression chamber 10 becomes negative pressure, the upper surface 5f of the piston ring 5 comes into contact with the upper surface 4c of the piston ring groove 4, and the piston ring 5 The lower surface 5e is the piston ring groove 4
away from the lower surface 4b of. Therefore, the gap 7 at the bottom of the groove
Gas from the crank chamber 13 side is introduced, but since the pressure of this gas is not high, the tension ring 6
The force urging the piston ring 5 in the diametrically expanding direction is weak, thus reducing the frictional force of the piston ring 5 against the cylinder wall and reducing wear on the piston ring 5.

Furthermore, since the tension ring 6 is made of silicone rubber, it is highly heat resistant, and the material does not harden due to thermal deterioration at high temperatures, and airtightness due to rubber elasticity is not impaired. Furthermore, since the tension ring 6 is made of silicone rubber, it can be formed into a continuous annular shape in the circumferential direction, and since there is no cut part in the circumferential direction, the stepped opening portions 5a and 5b of the piston ring 5 can be It can be closed reliably and the sealing performance is improved. Since the tension ring 6 has a cross-sectional shape with a flat outer peripheral surface, the piston ring 6
Therefore, even if the piston ring 5 has stepped opening portions 5a and 5b, these can be reliably sealed. In particular, when the tension ring 6 receives back pressure from the pressure gas introduced into the inner space 7, the tension ring 6 expands and deforms outward, so that the outer circumferential surface 6a of the tension ring 6 It is strongly pressed against the inner circumferential surface 5c, improving adhesion. Therefore, the sealing performance is further improved.

In addition, since the tension ring 6 has a semicircular or U-shaped cross-sectional shape on the inner peripheral surface side, when the tension ring 6 is placed over the piston 3 and fitted into the piston ring groove 4, Since there are no corners, installation is easier and workability is improved.

FIGS. 4 and 5 show experimental results regarding the effects of the above embodiment. As can be seen from FIG. 4, the piston ring of this example has an increased discharge amount for the same discharge pressure compared to the conventional piston ring alone, and it can be seen that this effect is particularly noticeable in the high discharge pressure region. Also, from Figure 5, compared to the conventional piston ring alone, the compression resistance of this example increases due to the higher sealing performance, so the power consumption increases, but this increase is offset by the discharge amount. Therefore, it is understood that the discharge amount can be improved without causing a significant increase in power consumption.

In the above embodiment, an example was explained in which a piston ring 5 having a publicly known stepped joint opening shape was used, but the present invention is not limited to this, and can be implemented as long as it is a piston ring in which stepped portions are overlapped along the axial direction. . Furthermore, for example, the piston ring 60 shown in FIG. 6 can also be regarded as substantially having a stepped opening shape, and is used by stacking a plurality of rings 61 with right-angled openings in the axial direction. Each abutment 62... is arranged with different phases in the circumferential direction, and such a piston ring 6
The present invention can also be applied when a piston ring 0 is used by fitting into a single piston ring groove.

Further, the present invention is not limited to gas compressors, but can be applied to various gas compression devices equipped with cylinders and pistons.

As detailed above, according to the present invention, since the tension ring is made of silicone rubber, it is highly heat resistant, the material does not harden due to thermal deterioration at high temperatures, and airtightness due to rubber elasticity is not impaired. In addition, since it can be formed into an annular shape that is continuous in the circumferential direction, there is no cut portion in the circumferential direction, so that the stepped opening portion of the piston ring can be reliably closed. In this case, the cross-sectional shape of the tension ring has a flat outer circumferential surface, so it comes into surface contact with the inner circumferential surface of the piston ring, thus sealing the stepped opening of the piston ring more reliably. can do. Then, the inner circumferential surface of the tension ring receives back pressure from the pressure gas introduced into the gap formed between it and the bottom surface of the piston ring groove, causing the tension ring to expand and deform. As a result, the flat outer circumferential surface of the tension ring is strongly pressed against the inner circumferential surface of the piston ring, thereby improving their adhesion and achieving extremely high sealing performance.

In addition, since the tension ring has a semicircular or U-shaped cross-sectional shape on the inner peripheral surface, it is easier to fit into the piston ring groove, improving work efficiency. There are advantages.

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention, FIG. 1 is a sectional view showing the main parts of a gas compressor, FIG. 2 is a perspective view of a piston ring, and FIG. 3 is a tension ring. The perspective view, FIG. 4, and FIG. 5 are characteristic diagrams showing experimental results, respectively. Moreover, FIG. 6 is a perspective view showing another embodiment of the piston ring. 1... Cylinder, 3... Piston, 4... Piston ring groove, 5... Piston ring, 5a, 5
b...Step part, 6...Tension ring, 7...Gap, 10...Compression chamber.

Claims (1)

[Claims] 1. A piston ring groove is formed on the outer circumferential surface of a piston that is reciprocally inserted into a cylinder, and a stepped opening-shaped piston ring made of a self-lubricating synthetic resin material is provided in the piston ring groove. In the piston seal structure of the gas compression device, the piston ring is fitted into the piston ring and the piston ring's outer peripheral surface is in sliding contact with the cylinder's inner peripheral surface to maintain airtightness. is provided with a tension ring that can be elastically deformed in the direction of diameter expansion, and this tension ring is made of silicone rubber and has an annular shape that is continuous in the circumferential direction, and has a cross-sectional shape and an outer peripheral surface that is similar to the piston ring. It has a flat surface that contacts the inner circumferential surface of the tension ring and closes the stepped joint opening portion, and the inner circumferential surface is a semicircular or U-shaped curved surface, and the inner circumferential surface of the tension ring and the piston ring groove are connected to each other. A gap is provided between the bottom of the piston and the bottom of the piston, through which pressure gas pressurized by the piston is introduced through the side surface of the piston ring groove, the side surface of the piston ring, and the side surface of the tension ring. A gas compression device characterized in that the pressure of the gas introduced between the gaps acts as back pressure on the tension ring, thereby deforming the tension ring to expand its diameter and pressing it against the inner circumferential surface of the piston ring. Piston seal structure of the device.