JPH0953561A - Piston seal mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of leakage, to suppress consumption of a piston ring, and to attain a high vacuum by arranging a seal in a piston ring groove. SOLUTION: A seal groove is formed in the surface, extending at right angles with the central line of the cylinder 1, of a piston ring groove and sealants 4 and 8, such as an O-ring, is inserted therein. When a piston 2 is moved downward, a piston ring 6 is pressed against the cylinder 1 side and the piston 2 is moved in such a state that a resistance force is exerted thereon, As a result, an O-ring 4 is compressed, and leakage through a gap between the piston ring 6 and the piston 2 is prevented from occurring by means of a seal 4. Reversely, when the piston 2 is moved upward, the piston ring 6 is pressed against a gap 7 and leakage is prevented from occurring by means of the O-ring 8. As a result, leakage from an upper vacuum chamber 13 to a lower vacuum chamber 9 amounts to a total of a gap 3 → a gap 12 → a gap 3 and a gap 3 → a gap 10 → a gap 3, and leakage through the inner surface of the piston ring does not occur and a high vacuum is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for vacuum evacuation of semiconductor manufacturing equipment, physics and chemistry equipment, and household equipment for the purpose of obtaining a high vacuum comparable to an oil rotary vacuum pump without using oil. This is a seal mechanism for the dry vacuum pump of.

[0002]

2. Description of the Related Art Conventionally, there is a piston type vacuum pump as a vacuum pump for exhausting a vacuum device, and a seal between a piston and a cylinder which reciprocates in a cylinder is usually a piston ring 6 as shown in FIG. Is done in
Leakage occurs from this seal, and this leakage greatly affects the ultimate pressure of the pump. The leakage from the upper nerve chamber 13 to the lower vacuum chamber 9 has three routes. That is, (1) gap 3 → gap 12 → gap 3, (2) gap 3 → head gap 10 → gap 3, and (3) gap 3 → gap 5 → gap 11 → gap 7 → gap 3, Gas leakage is this total value. Generally, (1) is small because the piston ring 6 is in contact with the cylinder 1,
As shown in the figure, the gap in (2) can be made smaller by making an L-shaped gap 10, but in (3), the piston ring 6 has thermal expansion of the piston ring and the piston 2 has Since it is necessary to absorb the runout, the gap 11 must be made large and the amount of leakage becomes large. As a result, the amount of leakage increases in the order of (1) <(2 <(3). As a method of keeping the amount of leakage of (3) small, as shown in FIG. There is a method of inserting the seal 8. In this method, the seal 8 is at least 5 to 5.
It must be compressed by 15%, and this becomes the force that pushes the piston ring 6 against the cylinder 1, and since this force is large,
The piston ring 6 wears out immediately, and as a result, the amount of leakage in (1) increases and the ultimate pressure deteriorates. If this uses lubricating oil, even if it is pressed with a large force, the piston ring 6 can be prevented from being consumed, but if the piston ring 6 is used as a dry vacuum pump with solid lubricating material and it is used in a vacuum without lubricating oil, The ring 6 is worn out immediately, and in a short time, the leakage becomes large and the ultimate pressure becomes poor.

[0003]

The present invention was carried out in order to suppress the leakage of the inner surface of the piston ring 6 of (3), which has the largest amount of leakage of the seal, and the leakage is small. The challenge was to reduce the wear of the piston ring and achieve a high vacuum.

[0004]

To explain the structure of the present invention with reference to FIG. 1, a groove for inserting the piston ring 6 is provided with a seal groove on both sides or one side perpendicular to the center line of the cylinder 1, such as an O-ring. Then, the sealing materials 4 and 8 are inserted. Here, the clearances 5 and 7 between the piston ring 6 and the piston 2
Secures a gap in which the piston ring 6 can freely expand due to the tension. With such a configuration, the operating state of the piston 2 will be described with reference to the drawing. FIG. 1a shows an O-ring shaped bear when the piston 2 is moving downward, and FIG. , Shows the state of the O-ring when moving upward. The piston ring 6 is pressed against the cylinder 1 by the tension that the piston ring 6 has and the minute runout of the piston 2. Here, when the piston 2 moves downward, as shown in FIG. 1a, the piston ring 6 is pressed against the cylinder 1 side by the above-mentioned force, that is, the tension of the piston ring 6 and the center runout of the piston 2, and the piston 2 is It moves while receiving this resistance. As a result, the O-ring 4 is compressed by the force corresponding to this resistance force. As a result, the gap between the piston ring 6 and the piston 2 is sealed by the seal 4 to prevent leakage. On the contrary, when the piston 2 moves upward, as shown in FIG. 1b, the piston ring 6 is pressed into the gap 7 and the O-ring 8 prevents leakage. As a result, the leakage from the upper vacuum chamber 13 to the lower vacuum chamber 9 is the sum of (1) gap 3 → gap 12 → gap 3 and (2) gap 3 → gap 10 → gap 3, which is the largest piston ring. The leak (3) through the inner surface has been smeared and a high vacuum can be obtained. Here, there is a method of sealing only one side without attaching the O-rings on both sides, but in this case the piston 2
Since the seal is sealed only in one direction during the operation, the ultimate vacuum is deteriorated as a result.

[0005]

The clearances 5 and 7 between the piston ring 6 and the piston 2 have a clearance that allows the piston ring 6 to freely move under tension, and therefore the tension of the piston ring 6 has no effect on the sealing action on the cylinder 1. , And either O-ring during operation, ie 4 or 8
Since it is sealed by, the leakage from the vacuum chamber 13 to 9 is significantly reduced, and a high vacuum can be achieved.

[0006]

EXAMPLE When the diameter of the piston 2 is Φ40, the pumping speed is 1500 rpm, the evacuation speed is 20 l / min, and the ultimate vacuum obtained is a completely dry type without using oil and the seal of the present invention is used. The ultimate pressure is ≤10 by using
^-2 Torr.

[0007]

As a result of using the piston seal mechanism according to the present invention in the multi-stage dry vacuum pump, leakage of the vacuum time partitioned by the piston is reduced, and the ultimate vacuum obtained is 50 Torr of the conventional pump or less. 10
^It was possible to improve significantly by ^-2 Torr. Therefore, it can be used in place of the oil rotary pump that is currently a problem due to oil pollution, and industrial use becomes immeasurable.

[Brief description of drawings]

FIG. 1a is a sectional view of the invention piston seal mechanism, showing a state in which the piston is operating downward.

[Fig. 1b] Invention Piston seal mechanism state where piston is operating upward 1 cylinder 2 piston 3 piston-cylinder clearance 4 O-ring 5 piston ring groove upper surface clearance 6 piston ring 7 piston ring groove lower surface clearance 8 O-ring 9 Lower vacuum chamber 10 Piston ring clearance gap 11 Piston ring and same groove inner diameter gap 12 Piston ring and cylinder gap 13 Upper vacuum chamber

[Fig. 2] Cross-sectional view of conventional piston seal mechanism 1 Cylinder 2 Piston 3 Gap between piston and cylinder 5 Gap on top of piston ring 6 Piston 7 Gap on bottom of piston ring 8 O-ring 9 Lower vacuum chamber 10 Piston ring Abutment gap 12 Piston ring Cylinder clearance 13 Upper vacuum chamber

Claims (1)

[Claims] A cylinder is divided into a front stage (high vacuum side) and a rear stage (low vacuum side) with a partition plate as a boundary, and the piston in each cylinder is shared by one piston shaft, and
Each cylinder is further divided into a high vacuum chamber and a low vacuum chamber by a piston, and the exhausted gas flows from the high vacuum chamber of the preceding cylinder to the low vacuum chamber and then to the latter cylinder. In a vacuum pump, a piston seal mechanism in which a seal is provided on both or one side of the piston ring groove that is perpendicular to the cylinder center line.