Metal seal and sealing method using same

Abstract

The present invention comprises: a seal body (2) having an annular shape and a substantially rectangular cross section; a groove portion (3) recessed in an inner peripheral side or an outer peripheral side of the seal body; a pair of seal lip portions (4) forming an axial inner surface (3a) of the groove portion; and a pair of protrusions (5) protrusively provided on axial outer surfaces (3b) of the seal lip portions and respectively abutting first and second flanges (50, 51) that are a pair of sealed members. The present invention is configured such that, when sandwiched between the first and second flanges, only the pair of protrusions abut the first and second flanges, and a region between the first and second flanges is sealed in a state in which the pair of seal lip portions are deformed so as to approach each other in the axial direction.

Description

Metal seal and sealing method using same

[0001] The present invention relates to a metal seal used for pipe connections in semiconductor manufacturing equipment and a sealing method using the same.

[0002] 2. Description of the Related Art Conventionally, as disclosed in Patent Document 1, a hollow metal O-ring having a circular cross-sectional cavity in the center is known to seal the gap between a pair of flanges at a pipe connection portion of semiconductor manufacturing equipment.

[0003] Also, as disclosed in Patent Document 2, a metal seal is known that is annular in shape and is interposed between a pair of parallel flat surfaces, and includes an intermediate base, a first contact protrusion that abuts one of the flat surfaces, and a second contact protrusion that abuts the other of the flat surfaces, with the first contact protrusion protruding toward the inner diameter of the intermediate base and the second contact protrusion protruding toward the outer diameter of the intermediate base, so that when mounted and compressed, the pressure received from the pair of flat surfaces causes torsional elastic deformation that rotates around the intermediate base.

[0004] JP 2008-190675 A Japanese Patent No. 4091373 A

[0005] The metal seal of Patent Document 1 deforms the entire metal seal, so a large clamping force is required to maintain the sealing performance.

[0006] Furthermore, the metal seal of Patent Document 2 has a double seal structure in which a pair of contact protrusions is pressed against each of two parallel flat surfaces to be sealed, and therefore requires a large clamping force to exert sealing performance.

[0007] However, to make devices that use metal seals more compact and lightweight, and to reduce the bolt space required, it is necessary to reduce the size and number of bolts, which has led to a demand for a system that can provide the necessary sealing performance with a lower tightening force.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to reduce the tightening force required to exhibit the desired sealing performance in a metal seal.

[0009] In order to achieve the above object, in the present invention, the groove and the protrusions that are brought into pressure contact with the pair of sealed members are devised.

[0010] Specifically, the first invention comprises a seal body that is annular and has a generally rectangular cross section; a groove portion recessed into the inner or outer peripheral side of the seal body; a pair of seal lip portions that form the axially inner surface of the groove portion; and a pair of ridges that protrude from the axially outer surface of the seal lip portions and abut against a pair of sealed members, respectively; and is configured such that when sandwiched between the pair of sealed members, only the pair of ridges abut against the pair of sealed members, deforming the pair of seal lip portions so as to approach each other in the axial direction, thereby sealing between the pair of sealed members.

[0011] According to the above configuration, the pair of seal lip portions have a cantilever shape due to the presence of the groove on the axially inner side, and are therefore prone to deform around their bases, and only the protrusions provided on the pair of seal lip portions that are prone to deform come into contact with the pair of sealed members, with no contact at other portions. As a result, the pair of seal lip portions can be moderately deformed to exhibit sealing performance with a smaller tightening force than in the past.

[0012] In a second aspect of the present invention, in the first aspect, the cross section of the protrusion is semicircular, semielliptical, triangular, trapezoidal, or V-notch shaped.

[0013] According to the above configuration, the protrusions can be deformed into an optimum shape to exhibit the required sealing performance.

[0014] According to a third aspect of the present invention, in the first aspect, the ridge has a semicircular cross section with a radius r, the groove has a substantially rectangular or semicircular cross section, and the distance x from the bottom of the groove to the end of the ridge opposite the end of the seal lip portion is −0.2 mm or more and 3r or less, preferably −0.05 mm or more and 1r or less.

[0015] In this configuration, if x is smaller than −0.2 mm, the rigidity of the pair of seal lip portions decreases, and there is a risk that not only the protrusions but also the horizontal surfaces will come into contact with the pair of sealed members. However, by setting x to −0.2 mm or more, the horizontal surfaces will not come into contact with the pair of sealed members.

[0016] In a fourth invention, a metal seal is prepared which includes a seal body having an annular shape and a generally rectangular cross section, a groove recessed on the inner or outer peripheral side of the seal body, a pair of seal lip portions which form the axially inner surface of the groove portion, and a pair of ridges which protrude from the axially outer surface of the seal lip portions and abut against a pair of sealed members, respectively; the metal seal is sandwiched between the flat surfaces of the pair of sealed members, and the pair of ridges and the pair of seal lip portions are deformed so that only the pair of ridges abut against the pair of sealed members and the axially outer surface of the seal body does not abut against the pair of sealed members, thereby sealing the pair of sealed members.

[0017] According to the above configuration, the pair of seal lip portions have a cantilever shape due to the presence of the groove on the axially inner side, and are therefore prone to deform around their bases, and only the protrusions provided on the pair of seal lip portions that are prone to deform come into contact with the pair of sealed members, with no contact at other portions. As a result, the pair of seal lip portions can be moderately deformed to exhibit sealing performance with a smaller tightening force than in the past.

[0018] As described above, according to the present invention, it is possible to lower the tightening force required to achieve the desired sealing performance, thereby reducing the size and number of bolts required to achieve the required tightening force, and as a result, making it possible to reduce the size and weight of devices in which metal seals are used.

[0019] 1B is a cross-sectional view of a metal seal according to an embodiment of the present invention, with a portion cut away; FIG. 1C is a cross-sectional view of the metal seal before tightening, in which the metal seal is in contact with a pair of flat surfaces; FIG. 1D is a cross-sectional view of the upper half of the metal seal in a state in which the metal seal is in contact with a pair of flat surfaces and tightened; FIG. 1E is a cross-sectional view showing the dimensions of the metal seal; FIG. 1F is a cross-sectional view of the metal seal according to a first modified example of the present invention, equivalent to FIG. 1A; FIG. 1G is a cross-sectional view of the first modified example, equivalent to FIG. 1B; FIG. 1H is a cross-sectional view of the second modified example, equivalent to FIG. 1B; FIG. 1I is a graph showing the relationship between set height and compressive load according to Example 1; FIG. 1J is a graph showing the relationship between set height and compressive load according to Example 2; FIG. 1J is a cross-sectional view of the first comparative example, equivalent to FIG. 1B; FIG. 1J is a cross-sectional view of the first comparative example, equivalent to FIG. 1B; FIG. 1I is a cross-sectional view of the first comparative example, equivalent to FIG. 1B; FIG. 1J is a graph showing the relationship between set height and compressive load according to Example 1;

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] 1A to 1C show a metal seal 1 according to an embodiment of the present invention, which is used in pipe connections in semiconductor manufacturing equipment, vacuum equipment, liquid crystal panel manufacturing equipment, and the like. For example, the metal seal 1 is used to stop leaks between components of a flow meter. When the fluid is a gas, strict sealing performance is required, with no leakage permitted through the sealing material, and therefore metal seals are generally used in such applications. The metal seal 1 is made of, for example, stainless steel, copper alloy, or heat-resistant and corrosion-resistant alloy (Inconel, Hastelloy, etc.), and may be coated with a surface coating (gold, silver, copper, nickel, etc.).

[0022] The metal seal 1 includes a seal body 2 that is annular and has a generally rectangular cross section. As will be described in detail later, the dimensions are defined as shown in FIG. 1D . For example, in this embodiment, the seal body 2 has a radial cross-sectional width of 1.0 mm and an axial cross-sectional thickness A of 0.85 mm. The inner peripheral edge of the seal body is chamfered to a depth of, for example, 0.1 mm (C0.1).

[0023] A groove 3 is recessed on the outer periphery of the seal body 2. For example, the axial cross-sectional width of the groove 3 is 0.40 mm and the radial groove depth is 0.20 mm. Due to machining and other factors, the corners of the cross section of the groove 3 are rounded with a radius of 0.05 mm (R0.05), for example.

[0024] The formation of the groove 3 results in the provision of a pair of annular seal lip portions 4 that form the axially inner surface 3a of the groove 3. Due to the presence of the groove 3, the pair of seal lip portions 4 have a cantilever structure that is prone to deformation in the direction of approaching each other in the axially inner direction.

[0025] A pair of annular ridges 5 that come into contact with a pair of sealed members (first and second flanges 50, 51) are formed on the axially outer surface 3b of the seal lip portion 4. In this embodiment, the ridges 5 have a semicircular cross section with a radius r of 0.08 mm.

[0026] The lip thickness of the cantilever is, for example, T1 = T2 = 0.125 mm, and the distance x from the bottom of the groove to the end of the seal surface R is -0.04 mm. The distribution of T1 and T2 may vary slightly due to manufacturing errors, etc.

[0027] The metal seal 1 is configured so that when it is clamped between the first and second flanges 50, 51, only the corresponding protrusions 5 abut against the first and second flanges 50, 51, respectively, thereby deforming the pair of seal lip portions 4 so that they approach each other in the axial direction, thereby sealing between the first and second flanges 50, 51.

[0028] In this embodiment, the ridges 5 have a semicircular cross section, but may also have a semicircular, semielliptical, triangular, trapezoidal, or V-notch shape. The cross-sectional shape may be selected based on the size of the metal seal 1, the required tightening force, the amount of deformation, etc. Note that if the cross section of the ridges 5 is a pointed triangular shape, it is possible to obtain ridges that are easy to deform.

[0029] In this embodiment, the protrusion 5 is provided at the outer peripheral end of the seal lip portion 4, but it may also be provided at a slight distance radially inward from the outer peripheral end as in Modification 1 described below. However, in order to deform the pair of seal lip portions 4 so that they approach each other, it is important that at least a part of the groove portion 3 is located axially inward of them.

[0030] Next, a method of using the metal seal according to this embodiment will be described.

[0031] 1B, the metal seal 1 is placed so as to be sandwiched between the pair of flat surfaces 50a, 51a of the pair of first and second flanges 50, 51. For example, the metal seal 1 is placed so that the tip of the ridge 5 of the metal seal 1 abuts against the flat surface 51a of the lower second flange 51.

[0032] Next, the metal seal 1 is sandwiched from above by the first flange 50 having the flat surface 50a, whereby the corresponding ridges 5 come into contact with the pair of flat surfaces 50a, 51a.

[0033] Next, the pair of first and second flanges 50, 51 are fastened together with a predetermined tightening force using fastening bolts or the like. As a result, the pair of seal lip portions 4 are deformed so as to approach each other, as shown in Figure 1C. At this time, the pair of axially outer side surfaces 3b, excluding the pair of ridges 5, do not come into contact with the pair of flat surfaces 50a, 51a at all.

[0034] As a result, the metal seal 1 can be deformed appropriately with a smaller tightening force than conventional metal seals, and exhibits its sealing performance.

[0035] 2A and 2B show a metal seal 1' according to a first modification of the embodiment of the present invention, which differs from the above embodiment in that the position of the pair of ridges 5' is different. Note that in the following modifications, the same parts as those in FIGS. 1A to 1C are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0036] In this modification, the pair of ridges 5' are not provided at the outer circumferential ends of the pair of seal lip portions 4, but are provided slightly radially inward from the outer circumferential ends.

[0037] In this modification, the positions of the pair of ridges 5' are closer to the bases of the pair of seal lip portions 4 than in the above embodiment, so the bending moment applied to the bases tends to be relatively small.

[0038] In this modified example, only the pair of protrusions 5' are pressed against the pair of flat surfaces 50a, 51a and deform appropriately, so that the metal seal 1' deforms appropriately with a smaller tightening force than conventional metal seals, thereby demonstrating sealing performance.

[0039] -Modification 2- Figs. 3A and 3B show a metal seal 1'' according to Modification 2 of the embodiment of the present invention, which differs from the above embodiment in that a groove 3'' is formed on the inner circumferential side.

[0040] In this modified example, the grooves 3" are formed on the inner circumferential side, but not on the outer circumferential side. Therefore, the pair of ridges 5" also protrude slightly radially outward from the inner circumferential ends of the pair of seal lip portions 4". The seal body 2" is disposed on the outer circumferential side, and similarly has a chamfer 2a" formed thereon. Note that, although the pair of ridges 5" are provided slightly radially outward from the inner circumferential ends in modified example 2, they may also be provided at the inner circumferential ends.

[0041] In this modification, compared to the above embodiment in which the groove 3 and the pair of ridges 5 are provided on the outer periphery, the inner diameter of the pair of ridges 5'' is smaller, the circumferential length is shorter, and the contact area is smaller. Therefore, the tightening force required to exhibit sealing performance tends to be relatively smaller.

[0042] In this modified example, only the pair of ridges 5'' are pressed against the pair of flat surfaces 50a, 51a and deform appropriately, so that the metal seal 1'' deforms appropriately with a smaller tightening force than conventional metal seals, thereby demonstrating sealing performance.

[0043] Examples 1 and 2 were the metal seal 1 of the above embodiment, with the outer diameter of Example 1 being 6.4 mm and the outer diameter of Example 2 being 16.8 mm.

[0044] The metal seal 101 shown in Fig. 5A was used as the comparative example 1 and comparative example 2 (see Patent Document 2). Comparative example 1 was a metal seal 101 with an outer diameter of 6.4 mm, and comparative example 2 was a metal seal 101 with an outer diameter of 16.8 mm.

[0045] (FEM Analysis) For simplification in the FEM analysis, the analysis conditions were a 1 / 2 axisymmetric analysis for Example 1 and an axisymmetric analysis for Comparative Examples 1 and 2. The material for each was SUS316L, and the pair of flat surfaces 50a, 51a was a rigid body.

[0046] As shown in FIG. 1C, it can be seen that the seal lip portions 4 are deformed from their bases so as to approach each other in the axial direction, and other portions are not in contact with each other.

[0047] As described above, in this embodiment, the metal seal 1 is sandwiched between the flat surfaces of the first and second flanges 50, 51, and only the pair of protrusions 5 abuts against the first and second flanges 50, 51, and the axial outer surface 3b of the seal body 2 does not abut against the first and second flanges 50, 51, so that the pair of protrusions 5 and the pair of seal lip portions 4 are deformed to seal the first and second flanges 50, 51.

[0048] On the other hand, in the metal seal 101 of Comparative Example 1, as described in Patent Document 2, a pair of contact protrusions 104 and 105 and a pair of contact protrusions 103 and 106 are pressed against a pair of flat surfaces 50a and 51a, respectively, forming a double seal structure (see FIG. 5B ). Therefore, in order to maintain the required sealing performance, the two annular portions on the inner and outer diameter sides must be in contact with the pair of flat surfaces 50a and 51a, and since the contact area is large, a large tightening force is required. Since Comparative Example 1 does not have the grooves like those in Example 1, the effect of the grooves making the protrusions more easily deformed was not achieved.

[0049] -Compression Load Test- Test specimens corresponding to the metal seals 1, 101 of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared, and each test specimen was placed on the lower second flange 51. The upper first flange 50 was pressed vertically downward at 0.2 mm / sec, and the change in displacement (set height) and compressive load at this time was examined.

[0050] As can be seen from the results of the compression load test shown in FIG. 4A, in Example 1, the compression load was about 1.8 kN at a set height of 0.7 mm, which was sufficient to exhibit the required sealing performance.

[0051] On the other hand, as shown in FIG. 6, in Comparative Example 1, which has an outer diameter similar to that of Example 1, when the set height is 0.7 mm, the compressive load is 12.5 kN, which is about seven times that of Example 1.

[0052] In Example 2, which has an outer diameter of 16.8 mm, which is about 2.6 times the outer diameter of Example 1, the compressive load is about 4 kN at a set height of 0.7 mm, as shown in FIG. 4B.

[0053] On the other hand, in Comparative Example 2, as shown in FIG. 7, a tightening force of about 29 kN, which is about seven times that of Example 1, is required.

[0054] As will be described later, if the depth of the groove portion 3 is too deep, the pair of seal lip portions 4 will be too prone to deformation, making it difficult to maintain the required tightening force, so it is advisable to set the thickness of the seal lip portions 4 and the depth of the groove portion to an appropriate value.

[0055] In this embodiment, the pair of seal lip portions 4 have the groove portion 3 on the inside in the axial direction, and therefore are prone to deformation around their bases, and only the ridges 5 provided on the pair of seal lip portions 4 that are prone to deformation come into contact with the first and second flanges 50, 51, and no other portions come into contact, so that the pair of seal lip portions 4 can be deformed and exhibit sealing performance with a smaller tightening force than in the past.

[0056] As described above, in this embodiment, it has been found that the projections 5 can be deformed into an optimum shape to exhibit the required sealing performance.

[0057] Therefore, with the metal seal 1 according to this embodiment, it is possible to lower the tightening force required to achieve the desired sealing performance, thereby reducing the size and number of bolts required to achieve the necessary tightening force, and as a result, making it possible to reduce the size and weight of the device in which the metal seal 1 is used.

[0058] 8A and 8B show a metal seal 1''' according to a third modification of the present invention, which differs from the first modification in that the shape of the U-shaped seal portion 3''' between the pair of seal lip portions 4''' is different. Note that the ridges 5''' are located in different positions than the ridges 5' of the first modification, but have the same shape.

[0059] In this modification, the cross section of the U-shaped seal portion 3''' is large, with R=0.2 mm, and forms a semicircular inner peripheral surface.

[0060] 10 shows the analysis results of the compressive load characteristics for Modification 3 when A = 0.85 mm, r = 0.08 mm, T1 = T2 = 0.125 mm, R = 0.2 mm, and x = 0.045 mm. The compressive load value was 6479 N at a set height of 0.7 mm and 5200 N at a set height of 0.76 mm, which was almost the same as Modification 1.

[0061] On the other hand, for Modification 1, which has a different shape of the groove portion 3, the analysis results of the compressive load characteristics when A = 0.85 mm, r = 0.08 mm, T1 = T2 = 0.125 mm, R = 0.05 mm, and x = 0.065 mm are shown in Figure 9. The compressive load value was 6489.4 N at a set height of 0.7 mm and 5250 N at a set height of 0.76 mm.

[0062] In addition, in order to investigate the characteristics of the shape of this modified example, the dimensions of modified examples 1 and 3 were changed and the rate of change in the reaction force was compared through analysis.

[0063] In variant 1, when the thickness balance between T1 and T2 was off by approximately 0.025 mm, the compression load was 5578.9 N at a set height of 0.7 mm and 4480 N at a set height of 0.76 mm. Compared to when T1 = T2, the thickness imbalance caused the compression load to decrease by approximately 14%, resulting in unstable sealing performance.

[0064] On the other hand, when analyzing variant 3 when the thickness balance between T1 and T2 was off by approximately 0.025 mm, the compression load was 6420 N at a set height of 0.7 mm and 5200 N at a set height of 0.76 mm, and it was found that the compression load was only about 1% lower than when T1 = T2, making the sealing performance less likely to become unstable.

[0065] As can be seen from these, in Modification 1, the sealing performance is likely to become unstable if the balance between the thicknesses T1 and T2 of groove portion 3 is disturbed, but in Modification 3, it was found that the sealing performance is less likely to become unstable even if the balance between the thicknesses T1 and T2 of groove portion 3''' is disturbed. Therefore, it was found that the shape of Modification 3 is advantageous over the shape of Modification 1 in that the sealing performance is not affected even if the processing of groove portion 3''' varies within the range of processing accuracy (dimensional tolerance).

[0066] Although no specific verification has been performed, the same applies to modified example 2 in which groove portion 3'' is arranged on the inner surface side, and it can be said that if groove portion 3 has a semicircular arc cross section with R = 0.2 mm, it will have no effect on sealing performance even if there is variation in processing compared to the shape of groove portion 3'' in modified example 2.

[0067] It should be noted that the above-described embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses.

[0068] 1, 1', 1'', 1''' Metal seal 2, 2'' Seal body 2a, 2a'' Chamfer 3, 3'', 3''' U-shaped seal portion 3a Axial inner surface 3b Axial outer surface 4, 4'', 4''' Seal lip portion 5, 5', 5'', 5''' Locking bulge portion 50 First flange (sealed member) 51 Second flange (sealed member) 50a, 51a Flat surface

Claims

1. A metal seal comprising: a seal body having an annular shape and a generally rectangular cross section; a groove recessed into the inner or outer peripheral side of said seal body; a pair of seal lip portions forming the axially inner surface of said groove portions; and a pair of ridges protruding from the axially outer surface of said seal lip portions and abutting against a pair of sealed members, wherein when sandwiched between said pair of sealed members, only said pair of ridges abut against said pair of sealed members, deforming said pair of seal lip portions so as to approach each other in the axial direction, thereby sealing between said pair of sealed members.

2. The metal seal according to claim 1, characterized in that the cross section of the protrusion is semicircular, semi-elliptical, triangular, trapezoidal or V-notch shaped.

3. The metal seal according to claim 1, wherein the ridge has a semicircular cross section with a radius r, the groove has a generally rectangular or semicircular cross section, and the distance x from the bottom of the groove to the end of the ridge opposite the end of the seal lip is not less than -0.2 mm and not more than 3r, and preferably not less than -0.05 mm and not more than 1r.

4. A sealing method using a metal seal comprising: a seal body having an annular shape and a generally rectangular cross section; a groove recessed into the inner or outer peripheral side of the seal body; a pair of seal lip portions forming an axially inner surface of the groove portion; and a pair of ridges protruding from the axially outer surfaces of the seal lip portions and abutting against a pair of sealed members, wherein the metal seal is sandwiched between flat surfaces of the pair of sealed members, and the pair of ridges and the pair of seal lip portions are deformed so that only the pair of ridges abut against the pair of sealed members and the axially outer surfaces of the seal body do not abut against the pair of sealed members, thereby sealing the pair of sealed members.

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