ACTUATOR FOR HIGH-PRESSURE VALVE

Abstract

Provided is an actuator including a ball-type thrust amplifier therein that controls a valve in which a high-pressure fluid flows, and having less wear between members and a long lifespan. This actuator for a valve includes a thrust amplification mechanism therein, in which the thrust amplification mechanism includes a disk, a ball presser, a stem, and a plurality of balls that are sandwiched by and in contact with an upper surface of the disk, a tapered surface of the ball presser, and a tapered surface of the stem and disposed to move outward as the stem moves downward, the surfaces of the parts constituting the thrust amplification mechanism are coated with grease containing an additive, and the additive of the grease includes at least chloroalkane.

Claims

1. An actuator for a valve comprising: a thrust amplification mechanism therein that increases thrust for pressing a valve body to open and close a flow path, wherein the thrust amplification mechanism includes a disk provided between an output end of the actuator and the valve body and configured to transmit the thrust for pressing the valve body, a ball presser disposed above the disk and having a conical tapered surface spreading outward and downward, a stem configured to pass through a through hole formed in a central portion of the ball presser and having a tapered surface whose tip end on the valve body side is tapered, and a plurality of balls sandwiched by and in contact with an upper surface of the disk, a tapered surface of the ball presser, and a tapered surface of the stem and disposed to move outward as the stem moves downward, a movement space of the balls is filled with grease containing an additive, and the additive includes at least chloroalkane in a group of sulfurized spam oil, sulfurized aliphatic ester, dibenzyl disulfide, alkyl polysulfide, olefin polysulfide, xanthic sulfide, chlorinated paraffin, methyl trichloro stearate, the chloroalkane, lead naphthenate, alkylthiophosphate amine, and chloroalkylxanthate.

2. The actuator for a valve according to claim 1, wherein the ball presser includes a contact member contacting with the balls, and a lid member configured to detachably press and fix the contact member from above.

3. The actuator for a valve according to claim 1, wherein the actuator is of a type that generates thrust by a piston driven by air, and an upper end of the stem is detachably engaged with a lower portion of the piston.

4. The actuator for a valve according to claim 2, wherein the actuator is of a type that generates thrust by a piston driven by air, and an upper end of the stem is detachably engaged with a lower portion of the piston.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 shows an actuator for a valve according to Embodiment 1 of the invention, which is attached to a valve.

[0022] FIG. 2 shows the actuator for a valve according to Embodiment 1 when the valve is in a closed state.

[0023] FIG. 3 shows the actuator for a valve according to Embodiment 1 when the valve is in an open state.

[0024] FIG. 4 shows a test result of a forward pressurization durability test.

[0025] FIG. 5 shows an actuator for a valve of the related art, which is attached to a valve.

DESCRIPTION OF EMBODIMENTS

[0026] Hereinafter, a preferred embodiment of the invention will be described in detail with reference to the drawings. Shapes, relative arrangements, and the like of components described in the embodiment are not intended to limit the scope of the invention unless particularly specified, and are merely illustrative examples. In addition, directions of members and the like may be referred to as, for convenience, up, down, left, and right depending on directions in the drawings, but these directions do not limit the scope of the invention.

[0027] FIG. 1 shows an actuator 1 for a valve, which is attached to a valve 2. A fluid inflow passage 11, a fluid outflow passage 12, and an annular valve seat 13 are formed in a body 10 of the valve 2. An upward protruding portion 15 is formed above the body 10, a recess portion is formed in the upward protruding portion 15, a diaphragm (valve body) 14 in contact with the annular valve seat 13 is disposed, and a diaphragm fixing member 18 fixing a peripheral edge of the diaphragm 14 is disposed. A through hole is formed in the center of the diaphragm fixing member in an upper-lower direction, a diaphragm presser 17 inserted through the through hole is disposed, and the diaphragm presser 17 includes a shaft portion 17a and a contact portion 17b. A screw thread is formed in an outer periphery of the upward protruding portion 15, and a bonnet 16 screwed with the screw thread is disposed, and a bonnet upper recess portion 16a and a bonnet lower recess portion 16b are formed.

[0028] A casing 20 includes an upper casing 22 and a lower casing 21, which are screwed with each other by the screw thread. A first piston 25 is disposed in an upper casing recess portion 22a inside the upper casing 22, a first piston recess portion 25b is provided in an upper portion of the first piston 25, and a compression coil spring 24 biasing the first piston 25 from above to below is disposed between a bottom surface of the recess portion and a ceiling lower surface of the upper casing recess portion 22a.

[0029] A counter plate 23 is disposed below the first piston 25, and an upper operation air introducing chamber 26 is formed between the first piston 25 and the counter plate 23. A second piston 28 is disposed inside the lower casing 21 below the counter plate 23.

[0030] An operation air inlet 22b for driving the pistons is provided in an upper portion of the upper casing 22, and there are a route in which operation air passes through a first piston axial air passage 25c formed in the first piston 25, passes through a second piston radial air passage 28c, and enters the upper operation air introducing chamber 26, and a route in which the operation air passes through a second piston axial air passage 28b formed in the second piston 28, passes through a stem axial air passage 30a and a stem radial air passage 30b that are formed in the stem 30 connected to a lower portion of the second piston 28, and enters a lower operation air introducing chamber 27 formed below the second piston 28. In order to maintain airtightness, portions between the casings and the pistons and the like are sealed by O-rings 25a, 23a, 23b, 28a, and the like. A bottom wall 21a is formed at a lower portion of the lower casing 21, and a thrust amplification mechanism accommodating recess portion 21b accommodating a thrust amplification mechanism is formed in the bottom wall 21a.

[0031] A through hole penetrating in an upper-lower direction is formed in the center of the bottom wall 21a, and the stem 30 penetrates through the through hole. A portion between the stem 30 and the bottom wall 21a is sealed by the O-rings 30c to maintain airtightness.

[0032] A disk 60 is disposed on a bottom of the bonnet upper recess portion 16a, a disk recess portion 61 is formed in the center, and a stem tip end portion 31 at a tip end of the stem 30 penetrates along with downward movement of the stem 30. Balls 50 are disposed on an upper surface 62 of the disk 60. When the number of balls to be disposed is three, the balls are disposed at intervals of 120 degrees, and when the number of balls to be disposed is four, the balls are disposed at intervals of 90 degrees. Since a size of the actuator becomes large when the number of balls is too large, the number of balls is preferably three to four when a compact actuator is formed.

[0033] Ball pressers 40 each having a ball pressing tapered surface 43, which is a conical tapered surface expanding outward and downward, are disposed above the balls 50. Each of the ball pressers 40 includes a contact member 41 having a ball pressing tapered surface 43 and a lid member 42 having a through hole 42a. A male screw thread is formed in an outer periphery of the lid member 42 and screwed into a female screw thread formed in an inner wall of the thrust amplification mechanism accommodating recess portion. A tip end of a special tool is inserted into the through hole 42a, and the ball presser 40 is pressed from above by turning the lid member 42. The stem tip end portion 31 at the tip end of the stem 30 has a tapered surface 32. The tapered surface 32, the ball pressing tapered surface 43, and the upper surface 62 are in contact with surfaces of the balls 50.

[0034] Since the stem tip end portion 31, the contact member 41, the disk 60, and the balls 50 that constitute the thrust force amplification mechanism are subjected to friction wear, a material that is hard to wear is preferably used. In order to make it difficult to wear, a coating that cures the surfaces is applied. In particular, members requiring coating are the disk 60 and the contact member 41. The contact member 41 is separate from the lid member 42a in which the male screw thread is formed, and it is unnecessary to perform screw thread processing after coating processing is performed. In the following embodiment and comparative examples, the same coating is performed on the surfaces of these members in common.

[0035] The coating includes a base layer on the surface of each member and a coating layer coated on the base layer, the base layer is formed by co-depositing nickel and fluorine-based polymer compound fine particles that are subjected to electroless plating processing on the surface of the member by using a plating solution obtained by dispersing the fluorine-based polymer compound fine particles in a nickel plating solution with a surfactant, and the coating layer includes a first gold-based plating layer that is formed by performing gold plating processing on the base layer and a second gold-based plating layer that is formed by performing the electroless plating processing on a surface of the first gold-based plating layer by using a plating solution obtained by dispersing the fluorine-based polymer compound fine particles in a gold plating solution with a surfactant, and by co-depositing gold and the fluorine-based polymer compound fine particles. Here, PTFE was used as a fluorine-based polymer compound. In this way, hardness is increased, and a slip property is increased by blending the fluorine-based polymer compound.

[0036] In addition, the coating processing can be alloy coating processing. As an example of synthetic coating processing, a binary synthetic coating using cobalt and phosphorus exerts a large effect on prevention of galling between metals, in particular, between stainless steels. Further, coating processing using nickel and phosphorus, or using nickel, phosphorus, and tungsten can also be performed.

[0037] Further, a movement space of the balls 50 is filled with grease containing an additive, and the additive includes at least chloroalkane in a group of sulfurized spam oil, sulfurized aliphatic ester, dibenzyl disulfide, alkyl polysulfide, olefin polysulfide, xanthic sulfide, chlorinated paraffin, methyl trichloro stearate, chloroalkane, lead naphthenate, alkylthiophosphate amine, and chloroalkylxanthate.

[0038] The chloroalkane is not particularly limited as long as the chloroalkane is chlorinated paraffin, but in the present embodiment, medium-chain chlorinated paraffin having 14 to 17 carbon atoms (chloroalkane (C14 to C17)) is preferably used.

[0039] FIG. 2 shows the actuator 1 according to Embodiment 1 when the valve 2 is in a closed state. The second piston 28 is lowered to a lower end, and the stem tip end portion of the stem 30 is lowered to the lower end, thereby moving the balls 50 outward. When the balls 50 move outward, a downward force is applied to the upper surface 62, the disk 60 moves downward, the diaphragm presser 17 moves downward, the diaphragm 14 comes into close contact with the annular valve seat 13, and the valve 2 is in the closed state. By the mechanism, thrust generated by the pistons is amplified.

[0040] FIG. 3 shows the actuator 1 according to Embodiment 1 when the valve 2 is in an open state. Air is introduced into the upper operation air introducing chamber 26 and the lower operation air introducing chamber 27, the first piston 25 and the second piston 28 move upward, and accordingly, the stem 30 moves upward and the balls 50 move inwardly. The disk 60 also moves upward, the diaphragm presser 17 also moves upward, and the valve 2 is in the open state.

[0041] FIG. 4 is a diagram showing a result of the forward pressurization durability test of a valve seat close performance test. Here, in the forward pressurization durability test, a measurement is performed as follows. In the valve open state, an outlet of the fluid outflow passage 12 is closed, a pressure of the fluid (for example, nitrogen gas) flowing through the valve is increased to 23 MPa, an inlet of the fluid inflow passage 11 is closed, and the valve 2 is closed in this state. Thereafter, the outlet of the fluid outflow passage 12 is opened. At this time, if a close capability is high, a pressure on an inlet side of the fluid inflow passage 11 does not decrease, but actually slightly decreases and stops. Values of the pressure are shown in the diagram of the forward pressurization durability test of FIG. 4.

[0042] Mechanical structures of the actuators of the embodiment and the comparative examples in FIG. 4 are exactly the same, and only the grease is different. All the greases used in the embodiment and the comparative examples contain 79% to 81% by weight of the synthetic oil as the base oil, 5% to 6% by weight of the thickener, and 9% to 11% by weight of the additive, whereas the greases used in the comparative examples do not contain the chloroalkane. The grease used in the embodiment contains the chloroalkane.

[0043] In view of the result of the forward pressurization durability test in FIG. 4, in the comparative examples 1 to 3, the pressure decreases to near 15 MPa when the number of times of opening and closing is 50,000, and the pressure decreases to less than 15 MPa when the number of times of opening and closing exceeds 200,000. In contrast, in Embodiment 1, the pressure can be maintained at 15 MPa or higher even if the number of times of opening and closing exceeds 300,000.

INDUSTRIAL APPLICABILITY

[0044] According to the actuator for a valve according to the invention, wear between members constituting the thrust amplification mechanism can be reduced, and thus an actuator for a valve having a long lifespan can be provided.

REFERENCE SIGN LIST

[0045] 1 actuator [0046] 2 valve [0047] 10 body [0048] 11 fluid inflow passage [0049] 12 fluid outflow passage [0050] 13 annular valve seat [0051] 14 diaphragm (valve body) [0052] 15 upward protruding portion [0053] 16 bonnet [0054] 16a bonnet upper recess portion [0055] 16b bonnet lower recess portion [0056] 17 diaphragm presser [0057] 17a shaft portion [0058] 17b contact portion [0059] 18 diaphragm fixing member [0060] 20 casing [0061] 21 lower casing [0062] 21a bottom wall [0063] 21b thrust amplification mechanism accommodating recess portion [0064] 22 upper casing [0065] 22a upper casing recess portion [0066] 22b operation air inlet [0067] 23 counter plate [0068] 23a O-ring [0069] 23b O-ring [0070] 24 compression coil spring [0071] 25 first piston [0072] 25a O-ring [0073] 25b first piston recess portion [0074] 25c first piston axial air passage [0075] 26 upper operation air introducing chamber [0076] 27 lower operation air introducing chamber [0077] 28 second piston [0078] 28a O-ring [0079] 28b second piston axial air passage [0080] 28c second piston radial air passage [0081] 30 stem [0082] 30a stem axial air passage [0083] 30b stem radial air passage [0084] 30c O-ring [0085] 31 stem tip end portion [0086] 32 tapered surface [0087] 40 ball presser [0088] 41 contact member [0089] 42 lid member [0090] 42a through hole [0091] 43 ball pressing tapered surface [0092] 50 ball [0093] 60 disk [0094] 61 disk recess portion [0095] 62 upper surface