Butterfly valve

An eccentric butterfly valve includes a valve body formed therein with an internal flow passage extending in a direction of the flow passage axis, a disk-shaped valve member disposed in the internal flow passage and supported by the valve body through valve stems to be rotatable about a rotation axis R, and an annular valve seat portion provided on an inner periphery of the internal flow passage, and the internal flow passage is opened and closed by rotating the valve stem to bring a sealing surface of an outer peripheral edge portion of the valve member into and out of contact with the valve seat portion. The valve member is further provided in one of the principal surfaces with a groove portion extending in a direction across the rotation axis R, and both side walls of the groove portion are formed as convex curved surfaces extending in a convex shape.

RELATED APPLICATIONS

The present application is National Phase of International Application No. PCT/JP2019/000230 filed Jan. 8, 2019, and claims priority from Japanese Application No. 2018-001829, filed Jan. 10, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a butterfly valve, which is used for fluid transport piping lines in various industries, opening and closing a flow passage by rotating a valve member.

BACKGROUND ART

In various industries, such as a chemical factory, a semiconductor manufacturing field, a food field, and a biotechnology field, a butterfly valve is used for opening and closing or controlling a flow passage through which various kinds of fluid flow. In the butterfly valve, a disk-shaped valve member rotatably supported by a valve body with a valve stem is disposed in a tubular flow passage formed in the valve body. The valve stem is rotated by a handle or an actuator connected to the valve stem and an outer peripheral edge portion of the valve member is brought into and out of contact with an annular sheet member provided between the inner peripheral surface of the flow passage or the valve body and the outer peripheral edge portion of the valve member, thus opening and closing the flow passage.

The butterfly valve has a configuration as described above, and therefore, even when the valve is fully opened, the valve member is arranged at the center of the flow passage of the valve body such that the principal surface (the surface which is directed in the direction of the flow passage axis when the valve is closed) is substantially parallel to the flow passage direction. As a result, the valve member reduces the opening area and serves as a resistance against a fluid to thereby reduce the valve flow coefficient, such as a Cv value. Particularly, in an eccentric butterfly valve which has a stem connected to the valve member such that the rotation axis is offset in the thickness direction of the valve member from the center axis of the valve member, the valve member is increased in thickness due to the configuration. Therefore, the valve member greatly affects the reduction in the opening area or an increase in a fluid resistance. There are proposed, as one of measures against such problems, butterfly valves configured so that a groove portion linearly extending perpendicularly to the rotation axis is provided in the principal surface of the valve member to form the cross section of the valve member into a substantially C shape, thereby increasing the opening area in full open and reducing the flow passage resistance, as described, for example, in PTL1.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Technical Problem

As described above, the reduction in the thickness of a part of the valve member by forming the groove portion in the valve member is advantageous to the increase in the opening area or the reduction in the flow passage resistance. Since a fluid pressure acts on the valve member of the butterfly valve in valve closing, a predetermined thickness is required for the valve member in order to prevent deformation of the valve member against the fluid pressure. Therefore, the depth of the groove portion is limited, and thus an improvement of the valve flow coefficient is limited only by formation of the linear groove portion.

Accordingly, it is an object of the present invention to solve the problems existing in the prior art and improve a valve flow coefficient of a butterfly valve by devising a shape of a valve member.

Solution to Problem

In view of the above-described object, the present invention provides a butterfly valve including a valve body formed therein with an internal flow passage extending in a direction of a flow passage axis, a disk-shaped valve member disposed in the internal flow passage and supported by the valve body through a valve stem to be rotatable about a rotation axis perpendicular to the flow passage axis, and an annular valve seat provided on an inner periphery of the internal flow passage, the internal flow passage being opened and closed by rotating the valve stem to bring an outer peripheral edge portion of the valve member into and out of contact with the valve seat, in which the valve member is provided in one of two principal surfaces thereof opposite to each other with a groove portion extending in a direction across the rotation axis and both side walls of the groove portion are formed as convex curved surfaces extending in a convex shape toward each other in the direction of the rotation axis.

In the above-described butterfly valve, the valve member is provided in at least one of the principal surfaces thereof with the groove portion extending in the direction across the rotation axis. Hence, when the valve member is rotated to a full open position, the opening area in the internal flow passage is increased by the area of the groove portion, so that a valve flow coefficient can be increased. Moreover, the present inventors have found that generation of vortex is suppressed, so that an effect of improving the valve flow coefficient is obtained, by forming both the side walls of the groove portion as the convex curved surfaces extending in a convex shape toward each other in the direction of the rotation axis to have such a shape that throttle portions are provided in the groove portions. Thus, the valve flow coefficient of the butterfly valve can be further improved.

In the above-described butterfly valve, it is preferable that the convex curved surfaces of both the side walls of the groove portion include curved surface portions having different curvature radii and connected with a top portion interposed therebetween, and it is more preferable that the convex curved surface of the groove portion is formed such that a curvature radius of a first curved surface portion disposed on a fluid outflow side in valve opening is larger than a curvature radius of a second curved surface portion disposed on a fluid inflow side in valve opening.

As one embodiment of the butterfly valve, the valve member may have outer edge remaining portions formed on both sides in the direction of the rotation axis with the groove portion interposed therebetween and the outer edge remaining portion may have convex curved surface curved in a convex shape in a direction away from the rotation axis. Such a configuration makes it possible to further improve the valve flow coefficient.

In this case, it is preferable that the convex curved surface of each of the outer edge remaining portions has convex curved surface portions having different curvature radii and connected to each other with a top portion interposed therebetween, and it is more preferable that the convex curved surface of the outer edge remaining portion is formed such that a curvature radius of a first curved surface portion disposed on a fluid outflow side in valve opening is larger than a curvature radius of a second curved surface portion disposed on a fluid inflow side in valve opening.

The butterfly valve may be configured so that the valve member has a spherical dent portion formed in the principal surface thereof opposite to the principal surface in which the groove portion is formed. Thus, the valve flow coefficient can be further improved.

Advantageous Effect of the Invention

According to the butterfly valve of the present invention, by providing the groove portion in at least one of the principal surfaces of the valve member, the opening area can be increased, thereby improving the valve flow coefficient. Furthermore, by forming the shapes of both the side walls of the groove portion or the surface shapes of the outer edge remaining portions on both sides of the groove portion into the convex curved surfaces, a further improvement of the valve flow coefficient due to suppression of generation of vortex can be achieved.

DESCRIPTION OF EMBODIMENTS

An embodiment of a butterfly valve11according to the present invention will be described below with reference to the drawings.

First, an overall configuration of the butterfly valve11according to the present invention will be described with reference toFIG. 1andFIG. 2.

The butterfly valve11includes a hollow cylindrical valve body13formed therein with an internal flow passage13aextending in a direction of a flow passage axis, a substantially disk-shaped valve member15disposed in the internal flow passage13aand rotatably supported by the valve body13, an annular seat ring17attached to the inner periphery of the internal flow passage13a, and an annular seat retainer19for fixing the seat ring17to the valve body13and is configured so that the internal flow passage13acan be opened and closed by bringing an outer peripheral edge portion of the valve member15and a valve seat portion17aformed on the seat ring17into and out of contact with each other.

The valve body13is provided, in a peripheral edge portion of a downstream end portion of the internal flow passage13athereof in the direction of the flow passage axis, i.e., an outer surrounding portion of the internal flow passage13ain the side surface of the valve body13on the downstream side in the direction of the flow passage axis, with an annular recessed portion21formed to extend in the radial direction to have substantially the same diameter as that of the outer diameter of the annular seat retainer19. The seat ring17and the seat retainer19are fitted into the annular recessed portion21. The seat retainer19includes an annular retainer body19aand an annular retainer cap19b. The retainer body19ais formed to have a step portion23(seeFIG. 7). The step portion23is configured to receive therein a retainer cap19band a fixing portion17bof the seat ring17such that the fixing portion17bof the seat ring17is arranged between the retainer cap19band the retainer body19a. Such a configuration makes it possible to fix the retainer body19ato the annular recessed portion21by an appropriate method and hold the fixing portion17bof the seat ring17between the retainer body19aand the retainer cap19barranged on the side surface of the annular recessed portion21in the direction of the flow passage axis, so that the seat ring17can be fixed to the annular recessed portion21.

The retainer cap19bis preferably arranged such that the inner peripheral edge end thereof projects into the internal flow passage13a.

As a method of fixing the retainer body19ato the annular recessed portion21, a bayonet method disclosed in Japanese Unexamined Patent Publication No. H11-230372 can be adopted, for example. In this case, the retainer body19ais provided, in the outer peripheral surface thereof on the side of the valve body13, with a plurality of circular arc-shaped projection portions projecting in the radial direction and formed at equal intervals in the circumferential direction, and the annular recessed portion21is provided in an outer peripheral portion thereof with circular arc-shaped notch portions formed to be able to receive the circular arc-shaped projection portions and engagement grooves extending from the side of the side surface of the circular arc-shaped notch portions in the direction of the flow passage axis so as to guide the circular arc-shaped projection portions in the circumferential direction. Such a configuration makes it possible fix the retainer body19ato the annular recessed portion21, by turning the retainer body19ain the circumferential direction, in a state where the circular arc-shaped projection portions of the retainer body19aare fitted into the circular arc-shaped notch portions of the annular recessed portion21and then abut on the side surface of the annular recessed portion21in the direction of the flow passage axis, and then guiding the circular arc-shaped projection portions along the engagement grooves to engage the circular arc-shaped projection portions with the engagement grooves.

The seat ring17is formed of an elastic material and has the valve seat portion17aand the fixing portion17b. The valve seat portion17ais formed to project into the internal flow passage13awhen the seat ring17is attached to the annular recessed portion21in the state where the fixing portion17bis held between the retainer body19aand the retainer cap19b. Examples of suitable elastic materials forming the seat ring17include rubber elastic bodies, such as butyl rubber (BR), chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), and fluororubber (FRM), fluororesin, such as polytetrafluoroethylene (PTFE), and rubber elastic bodies coated with fluororesin, such as PTFE.

The valve member15has two principal surfaces15a,15bopposite to each other and an outer peripheral edge portion15cannularly extending so as to connect the two principal surfaces15a,15b. The valve member15is provided in one principal surface15athereof with a groove portion25extending therethrough in a direction across (preferably a direction orthogonal to) a rotation axis R, as well shown inFIG. 3. Both side walls25a,25bof the groove portion25are formed to be convex curved surfaces extending in a convex shape toward the rotation axis R and toward each other as shown inFIG. 2andFIG. 4A. Due to the formation of the groove portion25in the one principal surface15aof the valve member15, there are formed outer edge remaining portions27(27a,27b) on both sides in the direction of the rotation axis R across the groove portion25. The outer edge remaining portions27preferably have convex curved surfaces extending in a convex shape in a direction away from the rotation axis R as shown inFIG. 4BandFIG. 4C.

By providing the above-described groove portion25, when the valve member15is rotated to a full open state, the opening area in the internal flow passage13ais increased by the area of the groove portion25, so that valve flow coefficient Cv increases. Moreover, the present inventors have found that generation of vortex is suppressed to reduce a pressure loss, by forming both the side walls25a,25bof the groove portion25as convex curved surfaces mutually extending in the convex shape toward the rotation axis R to be like throttle portions or by forming the outer edge remaining portions27a,27bformed on both sides of the groove portion25to have the convex curved surfaces extending in the convex shape in the direction away from the rotation axis R. This makes it possible to obtain an effect of improving valve flow coefficient Cv.

The valve member15has a spherical dent portion (hereinafter also referred to as “dimple”)29formed in a center portion of the other principal surface15b, as shown inFIG. 5. By providing the spherical dent portion29, similarly, the generation of vortex is suppressed, so that the effect of improving valve flow coefficient can be obtained due to reduction of pressure loss.

The valve member15has a valve member valve seat surface15dformed in the outer peripheral edge portion15cthereof. By rotating the valve member15about the rotation axis R to press the valve member valve seat surface15dagainst the valve seat portion17aof the seat ring17, a sealing plane sealing a space between the valve member valve seat surface15dand the valve seat17ais defined to close the internal flow passage13a, thereby resulting in a closed valve state. The valve member valve seat surface15dpreferably has a shape like a part of a spherical surface.

In the butterfly valve11of the embodiment shown in the figures, the valve member15is rotatably supported by the valve body13with a first valve stem31and a second valve stem33and is provided at positions thereof opposite to each other in the direction of the rotation axis R with a fitting hole35for coupling with the first valve stem31and an engagement groove37for coupling with the second valve stem33.

The first valve stem31is rotatably inserted through and supported in a first stem hole39formed in the valve body13to extend along the rotation axis R. The second valve stem33is inserted into and rotatably supported in a second stem hole41formed opposite to the first stem hole39across the internal flow passage13aalong the rotation axis R.

The first stem hole39is a stem through-hole extending through the valve body13from the outside to the internal flow passage13ain the direction of the rotation axis R. The first valve stem31is rotatably inserted through the first stem hole39so that both end portions thereof project from the first stem hole39. One end portion (upper end portion inFIG. 1) of the first valve stem31projecting to the outside is configured to allow a handle or a driving unit, not shown, to be attached thereto for operating or driving the valve member15. The other end portion (lower end portion inFIG. 1) of the first valve stem31projecting into the internal flow passage13ais formed to have a fitting portion31aof a shape complementary to the fitting hole35, so that the fitting hole35of the valve member15and the fitting portion31aare fitted into each other to be unrotatable about the rotation axis R. For example, by forming the fitting hole35of the valve member15and the fitting portion31aof the first valve stem31to have polygonal shapes, the fitting hole35and the fitting portion31acan be unrotatably coupled to each other.

On the other hand, the second stem hole41is a stem bottomed-hole (i.e., non-penetrating stem hole) extending in the direction of the rotation axis R from the internal flow passage13aof the valve body13. The second valve stem33is inserted into and rotatably supported in the second stem hole41, so that one end portion thereof projects from the second stem hole41. The second valve stem33includes a stem portion33arotatably supported in the second stem hole41, and an engagement portion33bwhich connects to the stem portion33aand is formed to project from the second stem hole41. The engagement portion33bis fitted into the engagement groove37. In detail, the engagement portion33bis formed as a rail-like portion extending in a direction perpendicular to the rotation axis R, as shown inFIG. 6AandFIG. 6B, one end of the rail-like portion projects and extends in the direction perpendicular to the rotation axis R from the outer peripheral surface of the stem portion33a, and the second valve stem33has a substantially L shape. The engagement groove37of the valve member15is formed to have a shape complementary to the rail-like portion as shown inFIG. 4A. The valve member15and the second valve stem33are coupled to each other to be unrotatable about the rotation axis R by inserting the engagement portion33b, which is the rail-like portion, into the engagement groove37of the valve member15in the direction perpendicular to the rotation axis R. The engagement portion33b, which is the rail-like portion, preferably has a wedge-shaped cross section expanding toward the tip from the root which is a portion connecting to the stem portion33a. Due to such a wedge shape, the removal of the valve member15in the direction of the rotation axis R from the second valve stem33can be prevented. However, the cross-sectional shape of the engagement portion33bis not limited insofar as the valve member15and the second valve stem33can be unrotatably coupled to each other and may be a polygonal shape, a circular shape, an oval shape, or the like.

As shown inFIG. 1, in order to prevent a fluid in the internal flow passage13afrom entering into the fitting hole35or the second stem hole41which is a bottomed hole, annular sealing members43,45are disposed in annular grooves provided, on the outer peripheral surfaces of the first valve stem31and the stem portion33aof the second valve stem33, at positions facing the vicinity of an opening portion into the internal flow passage13aon the inner peripheral surface of the fitting hole35and the vicinity of an opening portion into the internal flow passage13aon the inner peripheral surface of the second stem hole41, thereby sealing a space between the inner peripheral surface of the fitting hole35and the outer peripheral surface of the first valve stem31and a space between the inner peripheral surface of the second stem hole41and the outer peripheral surfaces of the stem portion33aof the second valve stem33. Further, in order to prevent a fluid in the internal flow passage13afrom flowing out to the outside through the first stem hole39which is a stem through-hole, annular sealing members47a,47b,47cformed of a rubber elastic material, such as an O-ring, are disposed in annular grooves provided at a plurality of positions (three places in the embodiment shown in the figures) including a position facing the vicinity of an opening portion of the first stem hole39into the internal flow passage13aon the outer peripheral surface of the first valve stem31, thereby sealing a space between the inner peripheral surface of the first stem hole39and the outer peripheral surface of the first valve stem31. Furthermore, as shown in detail inFIG. 7, the first valve stem31is provided, in the vicinity of an end portion thereof on the side opposite to the fitting portion31a, with a flange portion31b, and the valve body13is provided, in a portion surrounding an opening portion of the first stem hole39to the outside, with an annular recessed portion13bfor receiving therein the flange portion31b. An annular plane sealing member47dformed of a rubber elastic material is fitted into an annular groove provided on the surface (hereinafter referred to as a bottom surface) facing the flange portion31bin the annular recessed portion13b. The sealing member47ddisposed as described above seals a space between the flange portion31band the bottom surface of the annular recessed portion13b. Thus, even when a fluid in the internal flow passage13aenters the first stem hole39, the fluid is prevented from leaking out to the outside from the first stem hole39. Such a sealing structure is particularly effective when a harmful fluid flows through the internal flow passage13a.

The butterfly valve11of the embodiment shown in the figures is a double eccentric butterfly valve having a double eccentric structure. Referring toFIG. 1andFIG. 2, in the double eccentric butterfly valve11, the valve seat portion17aof the seat ring17, the valve member valve seat surface15d, the first valve stem31, and the second valve stem33are provided such that the center, in the direction of the flow passage axis, of the sealing plane defined between the valve member valve seat surface15dof the valve member15and the valve seat portion17aof the seat ring17in valve closing is located eccentrically in the direction of the flow passage axis from the rotation axis R of the valve member15. Furthermore, as shown in detail inFIG. 2, the first valve stem31and the second valve stem33are connected to the valve member15such that the rotation axis R of the valve member15is located away from a center axis O, which extends in parallel to the rotation axis R so as to pass through the center of the cross section of the internal flow passage13a, by a distance d in the cross section of the internal flow passage13a. Such a configuration makes it possible to utilize the cam action due to the eccentricity to move the valve member15away from the seat ring17with a slight angle rotation of the valve member15in opening and closing the valve, resulting in a low friction between the seat ring17and the valve member15. Therefore, the wear of the seat ring17can be reduced and an operation torque can be decreased.

Moreover, the double eccentric butterfly valve11is configured so that the rotation axis R is located eccentrically from the center axis O of the internal flow passage13aas described above, and therefore the maximum width of the valve member15in the direction of the rotation axis R is different between one side and the other side in the radial direction across the rotation axis R. Utilizing this fact, in the double eccentric butterfly valve11of the embodiment shown in the figures, the retainer cap19bis disposed such that the inner peripheral edge end thereof projects into the internal flow passage13a. Thus, by setting the amount of the projection into the internal flow passage13aof the retainer cap19bsuch that, when the valve member15is rotated from a closed valve state into an opened valve state, the valve member15can be rotated in one direction about the rotation axis R without making the outer peripheral edge portion15cinterfere with the retainer cap19band cannot be rotated in the other direction about the rotation axis R because of the outer peripheral edge portion15cinterfering with the retainer cap19b, the rotating direction of the valve member15from a fully closed state can be restricted.

The valve body13, the valve member15, the seat retainer19, the first valve stem31, and the second valve stem33can be formed of metal materials, resin materials, metal materials coated with resin materials, metal materials formed by insert molding according to an injection molding method, and the like, depending on the intended use.

Next, a method for assembling the butterfly valve11will be described with reference toFIG. 8AtoFIG. 8E.

First, as shown inFIG. 8A, the stem portion33aof the second valve stem33is rotatably inserted into the second stem hole41of the valve body13. At this time, the second valve stem33is disposed such that the rail-like portion of the engagement portion33bof the second valve stem33extends in the direction of the flow passage axis and the side projecting in the direction perpendicular to the rotation axis R from the peripheral surface of the stem portion33ais directed to the mounting side (annular recessed portion21side) of the seat ring17.

Next, as shown inFIG. 8B, the valve member15is inserted into the internal flow passage13aof the valve body13in the direction of the flow passage axis from the side of the valve body13opposite to the annular recessed portion21in the direction of the flow passage axis, in a state where the engagement groove37of the valve member15is directed to the valve body13side, so that the engagement portion33bof the second valve stem33and the engagement groove37of the valve member15are fitted into each other and the engagement portion33bis received in the engagement groove37until the engagement portion33breaches an end portion of the engagement groove37. As shown inFIG. 8C, the first valve stem31is then inserted into the first stem hole39, so that the fitting portion31aof the first valve stem31is unrotatably fitted into the fitting hole35of the valve member15. Thus, the valve member15is supported in the internal flow passage13aof the valve body13to be rotatable about the rotation axis R.

By inserting the valve member15into the internal flow passage13ain the state where the second valve stem33is disposed in the direction described above, the valve member15can be inserted from the side close to the second valve stem33, which facilitates the work.

Next, as shown inFIG. 8D, the valve member15is rotated by 180° about the rotation axis R in the internal flow passage13a, and, as shown in FIG.FIG. 8E, the valve member valve seat surface15dof the valve member15is disposed to be directed to the side on which the seat ring17is mounted, i.e., the annular recessed portion21side. Thereafter, the seat ring17is attached to the annular recessed portion21by the seat retainer19, so that the assembling of the butterfly valve11is completed.

Next, a detailed configuration of the valve member15will be further described.

It is preferable that the convex curved surfaces of both side walls25a,25b, in the direction of the rotation axis R, of the groove portion25of the valve member15include curved surface portions which have different curvature radii and are connected with a top portion interposed therebetween, and it is more preferable that the convex curved surfaces of the side walls25a,25bare formed such that the curvature radius of a first curved surface portion disposed on an outflow side (i.e., seat ring17side) in valve opening is larger than the curvature radius of a second curved surface portion disposed on an inflow side in valve opening. Moreover, it is preferable that the convex curved surfaces of the outer edge remaining portions27formed on both sides of the groove portion25in the direction of the rotation axis have curved surface portions which have different curvature radii and are connected with a top portion interposed therebetween, and it is more preferable that the convex curved surfaces of the outer edge remaining portion27is formed such that the curvature radius of the first curved surface portion disposed on the outflow side (i.e., seat ring17side) in valve opening is larger than the curvature radius of the second curved surface portion disposed on the inflow side in valve opening. Such a configuration makes it possible to obtain an effect of further improving the valve flow coefficient Cv.

EXAMPLES

A table will be given below which illustrates a comparison among the valve flow coefficients Cv obtained by a simulation when the curvature radii of the convex curved surfaces of both the side walls25a,25bof the groove portion25and the curvature radii of the convex curved surfaces of outer edge remaining portions27a,27bare individually varied.

A conventional example is a butterfly valve in which a groove portion is provided as with the butterfly valve11while both side walls of the groove portion in the direction of the rotation axis R are configured by planes parallel to the flow passage axis and the surfaces of outer edge remaining portions are configured only by non-curved planes. Example 1 to Example 4 are butterfly valves according to the present invention in which the groove portion25is provided as with the butterfly valve11and the curvature radii of the convex curved surfaces of both the side walls25a,25bof the groove portion25, the curvature radii of the convex curved surfaces of the outer edge remaining portions27a,27b, and the presence or absence of a dimple29are variously varied as parameters. The simulation was performed under a setting where the butterfly valve11having a nominal diameter D=150 mm is connected on the upstream side thereof to a linear inlet flow passage having a length of 2D and is connected on the downstream side thereof to a linear outlet flow passage having a length of 6D and where a differential pressure between the inlet flow passage and the outlet flow passage is set to 1 kPa.FIG. 9AtoFIG. 9Cillustrate parameters R1to R12used in the simulation. The arrows inFIG. 9AtoFIG. 9Cillustrate the fluid flow direction.

R1and R2designate the curvature radii of the convex curved surface portions disposed at the inflow side (inlet side) and the outflow side (outlet side) with the top portion interposed therebetween in valve opening, respectively, on the upper side wall25aof the groove portion25inFIG. 9A. R3, R4designate the curvature radii of the convex curved surface portions disposed at the inflow side (inlet side) and the outflow side (outlet side) on the lower side wall25bof the groove portion inFIG. 9A, respectively, with the top portion interposed therebetween in valve opening. Further, as shown inFIG. 9B, the surface of the upper outer edge remaining portion27ainFIG. 9Ahas such a configuration that: a convex curved surface portion of a curvature radius R6located on the inflow side (inlet side) in valve opening and a convex curved surface portion of a curvature radius R7located on the outflow side (outlet side) in valve opening are connected with the top portion interposed therebetween; a concave curved surface portion of a curvature radius R5is further connected to the upstream side of the convex curved surface portion of the curvature radius R6on the inflow side; and a concave curved surface portion of a curvature radius R8is further connected to the downstream side of the convex curved surface portion of the curvature radius R7on the outflow side, i.e., a configuration in which two S-shaped curved surface portions are connected with the top portion interposed therebetween. Similarly, as shown inFIG. 9C, the surface of the lower outer edge remaining portion27binFIG. 9Ahas such a configuration that: a convex curved surface portion of a curvature radius R10located on the inflow side (inlet side) in valve opening and a convex curved surface portion of a curvature radius R11located on the outflow side (outlet side) in valve opening are connected with the top portion interposed therebetween; a concave curved surface portion of a curvature radius R9is further connected to the upstream side of the convex curved surface portion of the curvature radius R10on the inflow side; and a concave curved surface portion of a curvature radius R12is further connected to the downstream side of the convex curved surface portion of the curvature radius R11on the outflow side, i.e., a configuration in which two S-shaped curved surface portions are connected with the top portion interposed therebetween.

The valve flow coefficient was calculated by the following expression.

Water was used as the fluid, and the fluid density was set to 997.561 kg/m3, which is the water density.

Example 2 and Example 3 are examples of butterfly valves in cases where the groove portion25is provided, both the side walls25a,25bof the groove portion25in the direction of the rotation axis R are formed to be convex curved surfaces extending in a convex shape toward each other, and the surfaces of the outer edge remaining portions27a,27bare formed as planes as with the prior art. When the prior art is compared with Example 2 and Example 3, it is found that an effect of improving the valve flow coefficient Cv is obtained by forming both the side walls25a,25bof the groove portion25in the direction of the rotation axis R as the convex curved surfaces extending in a convex shape toward each other.

Example 4 is an example of a butterfly valve in a case where the groove portion25is provided, both the side walls25a,25bof the groove portion25in the direction of the rotation axis R are formed to be convex curved surfaces extending in a convex shape toward each other, and the upper and lower outer edge remaining portions27a,27bare formed to have curved surfaces curved in a convex shape in a direction perpendicular to the rotation axis R. A comparison among Example 2 to Example 4 shows that the valve flow efficient Cv is largest when the convex curved surfaces of both the side walls25a,25bof the groove portion25are formed such that the curvature radius R2of the convex curved surface portion disposed at the outflow side (outlet side) in valve opening is larger than the curvature radius R1of the convex curved surface portion disposed at the inflow side (inlet side) in valve opening and R1=75 mm, R2=150 mm, R3=75 mm, and R4=150 mm, i.e., ratios of R1:R2=1:2 and R3:R4=1:2 are established.

Moreover, a comparison among Example 2 to Example 4 shows that an effect of improving the valve flow coefficient Cv is obtained when the surfaces of the outer edge remaining portions27a,27bare formed such that the curvature radii R7, R11of the convex curved surface portions disposed at the outflow side (outlet side) in valve opening are larger than the curvature radii R6, R10of the convex curved surface portions disposed at the inflow side (inlet side) in valve opening and R6=40 mm, R7=50 mm, R10=21.5 mm, and R11=40 mm are set in both the upper outer edge remaining portion27aand the lower outer edge remaining portion27b. Furthermore, it is found that an effect of improving the valve flow coefficient Cv is obtained when the surface of the upper outer edge remaining portion27ais formed such that the curvature radius R5of the concave curved surface portion disposed at the inflow side in valve opening and the curvature radius R6of the convex curved surface portion disposed at the inflow side in valve opening have a relation of R5=40 mm and R6=40 mm, i.e., R5:R6=1:1 and the curvature radius R7of the convex curved surface portion disposed at the outflow side in valve opening and the curvature radius R8of the concave curved surface portion disposed at the outflow side in valve opening have a relation of R7=50 mm and R8=40 mm, i.e., R7:R8=1.25:1. Similarly, it is found that an effect of improving the valve flow coefficient Cv is obtained when the surface of the lower outer edge remaining portion27bis formed such that the curvature radius R9of the concave curved surface portion disposed at the inflow side in valve opening and the curvature radius R10of the convex curved surface portion disposed at the inflow side in valve opening have a relation of R9=50 mm and R10=21.5 mm, i.e., R9:R10=2.3:1, and the curvature radius R11of the convex curved surface portion disposed at the outflow side in valve opening and the curvature radius R12of the concave curved surface portion disposed at the outflow side in valve opening have a relation of R11=40 mm and R12=30 mm, i.e., R11:R12=1.3:1.

Example 1 is an example of a butterfly valve in the case where a spherical dent portion (dimple) having a curvature radius of 400 mm is further provided in the form of the valve member of Example 4 on the other principal surface15bopposite to the principal surface15aof the valve member15where the groove portion25is formed. A comparison between Example 1 and Example 4 shows that an effect of further improving the valve flow coefficient Cv is obtained by providing the spherical dimple on the other principal surface15bopposite to the principal surface15aof the valve member15where the groove portion25is formed.

While the butterfly valve11according to the present invention has been described above with reference to the embodiment shown in the figures, the present invention is not limited to the embodiment shown in the figures. For example, in the above-described embodiment, the present invention has been described based on the embodiment in which the present invention is applied to the double eccentric butterfly valve11. However, the application of the present invention is not limited to the double eccentric butterfly valve and the present invention may be applied to a single eccentric butterfly valve or a multiple eccentric butterfly valve. Moreover, the present invention may be also applicable to a so-called center-type butterfly valve in which the rotation axis R extends through the center of the sealing plane and the center of the internal flow passage13aand the like.

DESCRIPTION OF REFERENCE NUMERALS

13ainternal flow passage

15couter peripheral edge portion

15dvalve member valve seat surface

17avalve seat portion

27,27a,27bouter edge remaining portion