Air-driven actuator and method for producing air-driven actuator

Abstract

Provided are: an air-driven actuator that is easy to machine, makes it easy to obtain a desired cylinder speed, and can easily be made more compact, particularly when making the air-driven actuator more compact while widening the interval between air ports in a double-action configuration; and a method for producing the air-driven actuator.　The air-driven actuator 1 has a cylinder 10 that is provided with at least one air port 15 on a rod-side end section 10a provided with a piston rod guide 50, and a piston reciprocating movement space 13 in which a piston 20 moves in a reciprocating manner is formed in the interior of said cylinder 10. The cylinder 10 has an enlarged diameter section 14 in which the inner diameter is enlarged in an area adjacent to the piston rod guide 50 in the direction of reciprocating movement of the piston 20. The air port 15 has a lower hole 15a including a non-passage section 15ab not passing through the interior of the cylinder 10 and a passage section 15aa that passes through the interior of the cylinder 10 as a result of overlapping a radial part of the piston 20 in the direction of reciprocating movement thereof and communicating with the enlarged diameter section 14.

Description

Air-driven actuator and method for manufacturing the same

[0001] The present invention relates to an air-driven actuator and a method for manufacturing an air-driven actuator, and more particularly to an air-driven actuator in which a piston reciprocates by drawing in and discharging air through an air port, and a method for manufacturing an air-driven actuator.

[0002] Conventionally, air-driven actuators operated by air pressure have been used as one of the drive sources for opening and closing valves. Two types of air-driven actuators are commonly used: a double-acting type that uses air pressure for both the opening and closing operations of the valve, and a single-acting type that uses the spring force of a spring for either the opening or closing operation of the valve.

[0003] For example, Patent Document 1 discloses a double-acting valve actuator in which two communication ports 43 provided in a cylinder portion 3 and communicating with the outside serve as intake and exhaust ports (air ports), and air pressure is alternately supplied to both sides of an internal piston 42 through these communication ports 43, causing the piston 42 to reciprocate. The reciprocating movement of the piston 42 rotates a Scotch yoke 33 via a piston rod 30 and a locking pin 31, which in turn rotates a shaft 32 integral with the Scotch yoke 33, thereby performing both opening and closing operations using air pressure. In the double-acting valve actuator described in Patent Document 1, as shown in Figure 8 of Patent Document 1, the communication port 43 on the piston rod 30 side does not pass linearly through the cylinder portion 3, but rather has a bent shape with a horizontal hole (a hole in the reciprocating direction of the piston 42) that communicates with the interior of the cylinder portion 3.

[0004] In the valve actuator described in Patent Document 1, a communication port 43 (air port) provided at the end of the cylinder section 3 on the side where the piston rod 30 is pulled out, i.e., the end on the rod side, is connected to the inside of the cylinder section 3 via a horizontal hole provided in the wall of the cylinder section 3.

[0005] Patent No. 6430173

[0006] However, in the valve actuator described in Patent Document 1, the communication port 43 (air port) provided at the rod-side end of the cylinder portion 3 has a curved shape with a horizontal hole in the direction of piston reciprocation. This requires drilling holes from two directions, which makes drilling complicated. Furthermore, the need for space for drilling the horizontal hole increases the dimension in the direction of piston reciprocation. Furthermore, the diameter of the horizontal hole is limited by the cylinder wall thickness, so the hole diameter must fit within the cylinder wall thickness. Depending on the cylinder wall thickness, it may be difficult to ensure a sufficient air intake and exhaust volume, which may result in difficulty in achieving the desired cylinder response speed. Furthermore, in the case of a double-acting actuator, considering the ease of assembling external devices such as a speed controller to the two communication ports 43 provided at the rod-side end and head-side end of the cylinder portion 3, it is desirable to increase the distance between the two communication ports 43, for example, by moving the rod-side communication port 43 as close as possible to the rod side. However, the demand for improved ease of assembly of such externally connected devices is in conflict with the demand for compactness of the device, and it has been difficult to satisfy both the demand for improved ease of assembly of externally connected devices and the demand for compactness of the device.

[0007] The present invention was developed to solve the problems of the past, and its purpose is to provide an air-driven actuator that is easy to process, makes it easy to obtain a desired cylinder response speed, and is also compact, particularly in the case of a double-acting type, where the distance between the two air ports can be increased while still achieving compactness, and a method for manufacturing such an air-driven actuator.

[0008] In order to achieve the above object, the invention of claim 1 is an air-driven actuator having a cylinder with at least one air port provided at an end of a rod side from which a piston rod is pulled out via a piston rod guide, and a piston reciprocating space formed therein in which the piston reciprocates by drawing in and exhausting air through the air port, the cylinder having an enlarged diameter portion provided by enlarging the inner diameter in an area adjacent to the piston rod guide in the reciprocating direction of the piston, and the air port provided at the end of the rod side has a pilot hole that includes a through portion that passes through into the cylinder by overlapping a radial portion on the rod side in the reciprocating direction of the piston and communicating with the enlarged diameter portion, and a non-through portion that does not pass through into the cylinder by not overlapping a radial portion on the enlarged diameter portion.

[0009] The invention according to claim 2 is an air-driven actuator in which the enlarged diameter portion has an inner diameter that gradually increases from the extended side of the piston rod toward the retracted side in the reciprocating direction of the piston.

[0010] The invention according to claim 3 is an air-driven actuator that has a drive space provided with a rotation conversion mechanism that converts the reciprocating motion of the piston into rotational motion and transmits it to an output shaft, has a housing that connects to the cylinder from the end on the rod side, and is used by being mounted on a valve with the output shaft and valve stem connected.

[0011] A fourth aspect of the present invention is a method for manufacturing an air-driven actuator, the method comprising the steps of: providing a cylinder having an enlarged diameter portion whose inner diameter is enlarged in a region adjacent to the piston rod guide in the direction of reciprocation of the piston, the cylinder having at least one air port provided at an end of the rod side from which the piston rod is pulled out, with a piston rod guide provided therein; and forming, as a pilot hole for the air port at the end of the rod pull-out side, a hole including: a through portion that passes through into the cylinder by overlapping a radial portion on the rod side in the direction of reciprocation of the piston with the enlarged diameter portion so that the enlarged diameter portion communicates with the enlarged diameter portion; and a non-through portion that does not pass through into the cylinder by not overlapping a radial portion with the enlarged diameter portion.

[0012] According to the invention of claim 1, a cylinder includes at least one air port provided at the rod-side end of the piston rod through which a piston rod guide is provided, and a piston reciprocating space is formed therein, in which the piston reciprocates by drawing in and exhausting air through the air port. The cylinder has an enlarged-diameter portion whose inner diameter is enlarged in a region adjacent to the piston rod guide in the direction of piston reciprocation. The air port provided at the rod-side end has a pilot hole including a through portion that passes through the cylinder by overlapping a radial portion of the rod-side portion in the direction of piston reciprocation with the enlarged-diameter portion, and a non-through portion that does not pass through the cylinder by not overlapping a radial portion of the enlarged-diameter portion. In this way, rather than directly penetrating the air port into the cylinder, a radial portion of the pilot hole is connected to the enlarged-diameter portion while the remaining portion is non-through, thereby eliminating the need for a separate hole for passing the air port into the cylinder. If the piston reciprocates along the inner wall surface of the cylinder and passes through the through hole of the air port provided in the cylinder wall, the piston or piston seal may be damaged. Therefore, a through hole must be provided outside the piston's stroke range, but the cylinder becomes larger by the distance. As described above, the invention of claim 1 allows the air port to communicate with the cylinder without providing a separate through-hole that directly connects the air port to the inside of the cylinder, thereby avoiding damage to the piston and piston seal and reducing the size of the cylinder. Furthermore, the invention of claim 1 allows the air port to communicate with the inside of the cylinder through the enlarged diameter section without a side hole, eliminating the need for complicated side hole machining and facilitating the machining of the air port. Furthermore, by adjusting the overlap between the enlarged diameter section and the pilot hole, a sufficient amount of air can be suctioned and exhausted. Furthermore, because no side hole is provided, and the area other than the area where the air port radially overlaps the enlarged diameter section can be used as the piston stroke area, the overall cylinder size can be reduced. In the case of a double-acting cylinder, the air port at the rod end of the cylinder can be located away from the air port at the head end of the cylinder.Therefore, machining is easy, the desired cylinder speed can be easily obtained, and furthermore, compactness can be achieved, particularly in the case of a double-acting type, by widening the distance between the two air ports while still achieving compactness.

[0013] According to the invention of claim 2, the enlarged diameter portion has an inner diameter that gradually increases from the extension side to the retraction side of the piston rod in the reciprocating direction of the piston, which makes it easier to mold the cylinder using a mold than an enlarged diameter portion formed as a groove of a fixed depth. Furthermore, with the invention of claim 2, the enlarged diameter portion gradually increases from the edge side of the enlarged diameter portion toward the inner diameter side, so that the diameter of the communicating portion can be easily adjusted by adjusting the depth of the pilot hole, and the amount of air intake and exhaust can also be easily set.

[0014] According to the invention of claim 3, the housing has a drive space formed with a rotation conversion mechanism that converts the reciprocating motion of the piston into rotational motion and transmits it to the output shaft, and is connected to the cylinder from the rod side end. By mounting the output shaft of the rotation conversion mechanism and the valve stem connected together and using the valve, the reciprocating motion of the piston within the compact cylinder is converted into rotational motion of the valve stem via the rotation conversion mechanism, opening and closing the valve, and the device can be used as a valve actuator that can be assembled compactly to the valve.

[0015] According to a fourth aspect of the present invention, a method for manufacturing an air-driven actuator includes a cylinder having at least one air port provided at a rod-side end of the piston rod through a piston rod guide, the cylinder having a piston reciprocating space formed therein, where the piston reciprocates by drawing in and exhausting air through the air port, the method comprising the steps of: providing an enlarged-diameter portion in the cylinder, the enlarged-diameter portion having an enlarged inner diameter in an area adjacent to the piston rod guide in the direction of piston reciprocation; and forming a pilot hole for the air port at the rod-side end of the cylinder, the pilot hole including a through portion that radially overlaps the enlarged-diameter portion in the direction of piston reciprocation and communicates with the enlarged-diameter portion, and a non-through portion that does not radially overlap the enlarged-diameter portion and does not penetrate the cylinder. This allows for easy and low-cost formation of the air port, for example, when using a molding technique such as casting to form the cylinder, by first forming the enlarged-diameter portion and then simply drilling a pilot hole that partially communicates with the enlarged-diameter portion. In particular, because the air port communicates with the interior of the cylinder through the enlarged-diameter portion without a lateral hole, the complicated machining of a lateral hole is eliminated, making machining of the air port easier. Furthermore, by adjusting the overlap between the enlarged diameter portion and the pilot hole, a sufficient amount of air can be suctioned and exhausted. Furthermore, since no side hole is provided, and the area other than the area where the air port radially overlaps the enlarged diameter portion can be used as the piston stroke area, the overall cylinder size can be reduced. In the case of a double-acting cylinder, the air port at the rod end of the cylinder can be spaced apart from the air port at the head end of the cylinder. This simplifies machining, makes it easy to achieve the desired cylinder speed, and allows for compactness, particularly in the case of a double-acting cylinder, by increasing the distance between the two air ports.

[0016] Figure 4 is a perspective view of an air-driven actuator according to an embodiment of the present invention. Figure 5 is a cross-sectional view of the air-driven actuator with the piston head at a stroke terminal position on the head side inside the cylinder. Figure 6 is a cross-sectional view of the air-driven actuator with the piston head at a stroke terminal position on the rod side inside the cylinder. Figure 7 is an enlarged perspective view of the periphery of an enlarged diameter portion of the air-driven actuator shown in Figure 3. Figure 8 is a view of the opening, viewed from the inner wall surface side of the cylinder, where the pilot hole of the air port provided at the end on the rod side communicates with the enlarged diameter portion. Figure 9 is a partially cutaway perspective view of the air-driven actuator with speed controllers attached to two air ports and assembled to a valve.

[0017] An embodiment of an air-driven actuator and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of an air-driven actuator 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the air-driven actuator with the piston head 22 at a stroke terminal position on the head side inside the cylinder 10. FIG. 3 is a cross-sectional view of the air-driven actuator 1 with the piston head 22 at a stroke terminal position on the rod side inside the cylinder 10. FIG. 4 is an enlarged perspective view of the enlarged diameter portion 14 and its surroundings of the air-driven actuator 1 shown in FIG. 3. FIG. 5 is a view of the opening 15ac, which is the portion where the pilot hole 15a of the air port 15 provided at the rod-side end 10a communicates with the enlarged diameter portion 14, viewed from the inner wall surface 12a side of the cylinder 10. FIG. 6 is a perspective view of the air-driven actuator 1 with speed controllers 200 attached to the two air ports 15, 16 and assembled to the valve 100, with a portion cut away. The air-driven actuator 1 according to the embodiment of the present invention is one of the drive sources for opening and closing a valve (not shown), and employs a double-acting system that uses air pressure for both the opening and closing operations of the valve.

[0018] The air-driven actuator 1 includes a cylinder 10, a piston 20 that reciprocates using air pressure, a housing 30 that is connected to the cylinder 10 and that is provided with a rotation conversion mechanism 60 that converts the reciprocating motion of the piston 20 into rotational motion, a housing cap 40 that closes one end opening of the housing 30, and a piston rod guide 50 that guides the piston rod 21 of the piston 20. The cylinder 10, the housing 30, and the housing cap 40 are axially connected to each other so as to be concentric with the axis of the piston rod 21, thereby forming the outer shell of the air-driven actuator 1 whose longitudinal direction is the axial direction of the piston rod 21. In this embodiment, the cylinder 10, the housing 30, and the housing cap 40 are manufactured by casting, but other manufacturing methods may be used, or various manufacturing methods may be combined. For example, the interior of the cylinder 10 may be machined after casting.

[0019] (Regarding the Cylinder 10) When the end of the cylinder 10 from which the piston rod 21 is pulled in the reciprocating direction of the piston 20 is defined as the rod-side end 10a and the end of the cylinder 10 toward which the piston rod 21 is retracted is defined as the head-side end 10b, the cylinder 10 forms a piston reciprocating space 13 inside in which air is taken in and exhausted through two air ports 15, 16 provided at the respective ends 10a, 10b, and in which the piston 20 reciprocates. The cylinder 10 has a peripheral side wall 12 and a closing wall 11 provided at the head-side end 10b, and is generally cylindrical with the rod-side end 10a facing the closing wall 11 and open.

[0020] The cylinder 10 has one air port 15 (hereinafter referred to as the "rod-side air port") at its rod-side end 10a and another air port 16 (hereinafter referred to as the "head-side air port") at its head-side end 10b. These two air ports 15, 16 are formed by drilling pilot holes 15a, 16a in the peripheral side wall 12 and then drilling tapped holes 15b, 16b. In this embodiment, as shown in FIG. 1 , the rod-side air port 15 is provided so as to partially overlap the flange portion 10aa of the cylinder 10. In this embodiment, external connection devices such as speed controllers (not shown) are attached to the two air ports 15, 16 by threading them into the tapped holes 15b, 16b. The two air ports 15, 16 are connected to the directional control valve via air piping connected to the speed controller.

[0021] An external device, for example, a speed controller 200 as shown in FIG. 6 , is attached to the two air ports 15, 16. The attachment space for the external device depends on the distance between the air ports 15, 16. For example, when attaching the speed controller by screwing it into a tapped hole provided in the air ports 15, 16, the speed controller, which has a rectangular parallelepiped shape as shown in the figure, must be rotated to screw it in. Therefore, when screwing it into each air port 15, 16, it is necessary to grasp and rotate the speed controller, and therefore the area in question must not simply have enough space to accommodate the device, but must have more room than that. Therefore, it is preferable to separate the two air ports 15, 16 as far as possible. In this embodiment, the pilot hole 15a of the air port 15 is connected to the enlarged diameter portion 14 provided in the cylinder 10, thereby enabling air to be supplied from the air port 15 to the inside of the cylinder 10. However, because this enlarged diameter portion 14 is provided in an area adjacent to the piston rod guide 50, the air port 15 that communicates with it can be provided as close as possible to the piston rod 21 side (for example, overlapping partially or completely with the flange portion 10aa). As a result, the air port 15 typically has to be provided midway on the wall of the cylinder 10 to communicate with the inside of the cylinder 10, making it difficult to provide a sufficient distance between the two air ports 15, 16. In contrast, in this embodiment, the distance between the air ports 15, 16 can be made as large as possible, which is advantageous for attaching external devices such as the speed controller 200.

[0022] The cylinder 10 also has an enlarged-diameter portion 14, the inner diameter of which is enlarged in a region adjacent to the piston rod guide 50 in the reciprocating direction of the piston 20. The enlarged-diameter portion 14 is a groove formed in the inner wall surface 12a of the peripheral side wall 12 along the inner circumferential direction, and the inner diameter gradually increases from the extension side of the piston rod 21 toward the retraction side in the reciprocating direction of the piston 20. In this embodiment, the cylinder 10 and the housing 30 are connected via flange portions 10aa, 30aa provided on their respective ends 10a, 30a. Therefore, the thickness of the peripheral side wall 12 at the rod-side end 10a of the cylinder 10 is thicker than the surrounding area due to the combined thickness of the flange portion 10aa.

[0023] That is, the rod-side end 10a of the circumferential side wall 12 of the cylinder 10 is provided with a flange portion 10aa that protrudes radially outward beyond the portion of the circumferential side wall 12 other than the end 10a. The enlarged diameter portion 14 is provided in this thick-walled portion of the flange portion 10aa, and is provided so that its outermost diameter position is located radially outward beyond the outer wall surface 12b of the circumferential side wall 12 of the cylinder 10 other than the flange portion 10aa. That is, the enlarged diameter portion 14 is provided in the circumferential side wall 12 of the cylinder 10, effectively utilizing the portion of the wall thickened by the flange portion 10aa of the cylinder 10. Then, as described below, by providing the rod-side air port 15 with a pilot hole 15a that communicates with the enlarged diameter portion 14, it is not necessary to provide a separate through-hole for supplying air into the cylinder 10 in the portion of the circumferential side wall 12 of the cylinder 10 other than the flange portion 10aa.

[0024] In this manner, in this embodiment, the enlarged diameter portion 14 is provided in the flange portion 10aa of the cylinder 10, so that it does not interfere with the peripheral side wall 12 of the cylinder 10 excluding the flange portion 10aa, i.e., the normal range of reciprocation (stroke) of the piston head 22. As a result, an increase in the size of the cylinder 10 due to the provision of the enlarged diameter portion 14 is prevented. The enlarged diameter portion 14 may be provided by enlarging the inner diameter in a region adjacent to the piston rod guide 50 in the reciprocating direction of the piston 20, and may be, for example, a groove of a constant depth provided in the inner wall surface 12a of the peripheral side wall 12.

[0025] The rod-side air port 15 has a pilot hole 15a that communicates with the enlarged diameter portion 14. The pilot hole 15a includes a through portion 15aa that passes through the interior of the cylinder 10 by overlapping a portion of the diameter in the reciprocating direction of the piston 20 and communicating with the enlarged diameter portion 14, and a non-through portion 15ab that does not pass through the interior of the cylinder 10 by not overlapping a portion of the diameter with the enlarged diameter portion 14. The non-through portion 15ab of the pilot hole 15a does not pass through the peripheral side wall 12 of the cylinder 10, and therefore, as shown in FIGS. 2 to 4, the back side of the pilot hole 15a is an area A of the inner wall surface 12a on which the piston head 22 can slide.

[0026] Furthermore, the depth of the non-penetrating portion 15ab is set to a position that is the same as or shallower than the outer wall surface 12b of the circumferential side wall 12 of the cylinder 10 other than the flange portion 10aa. Here, "the depth of the non-penetrating portion 15ab is the same as or shallower than the outer wall surface 12b of the circumferential side wall 12 of the cylinder 10" means, for example, that the uniform portion of the pilot hole 15a, for example, the portion excluding the portion that tapers toward the tip when the pilot hole is drilled, is the same as or shallower than the outer wall surface 12b of the circumferential side wall 12 of the cylinder 10. By forming the non-penetrating portion 15ab in this manner, the strength of the circumferential side wall 12 of the cylinder 10 can be sufficiently maintained even when the pilot hole 15a is provided, and the operation of the piston 20 can be prevented from being impaired.

[0027] Furthermore, by overlapping a portion of the pilot hole 15a radially with the enlarged diameter portion 14 in the direction of reciprocation of the piston 20, the rod-side air port 15 can be located as close as possible to the rod-side end 10a of the cylinder 10, i.e., close to the piston rod guide 50. Furthermore, in this embodiment, the enlarged diameter portion 14 is located in the flange portion 10aa, i.e., in a portion that is originally outside the range of reciprocation of the piston 20, so it is possible to increase the distance from the head-side air port 16 without increasing the dimension of the piston 20 in the direction of reciprocation.

[0028] As shown in FIGS. 4 and 5 , the through-portion 15aa of the rod-side air port 15 penetrates the inner wall surface 12a of the cylinder 10, including the inclined surface 14a of the enlarged diameter portion 14, to form an opening. In other words, the pilot hole 15a penetrates the inner wall surface 12a of the cylinder 10, including the surfaces 14a and 14b that face in different directions to form the enlarged diameter portion 14, to form the opening 15ac. Therefore, the opening area of ​​the opening 15ac can be adjusted by adjusting the degree of overlap between the enlarged diameter portion 14 and the pilot hole 15a. Furthermore, because the opening 15ac is formed across multiple surfaces in different directions, the opening area can be made larger than when the opening 15ac is formed across a single surface. The opening area of ​​the opening 15ac can be adjusted to accommodate a wide variety of specifications, for example, by changing the degree of overlap between the enlarged diameter portion 14 and the pilot hole 15a in the radial and depth directions, as well as the shape of the enlarged diameter portion 14 or the pilot hole 15a. Therefore, the opening area of ​​the opening 15ac can be made larger than the opening area of ​​a conventional horizontal hole whose dimensions are determined by the thickness of the peripheral side wall 12 of the cylinder 10, and can also accommodate various opening shapes.

[0029] The opening area of ​​opening 15ac is adjusted so as to obtain a desired cylinder response speed. More specifically, the opening area of ​​opening 15ac is adjusted so as to be equal to or larger than the cross-sectional area of ​​the hole of the air piping connected to rod-side air port 15. In this way, since rod-side air port 15 is formed by communicating enlarged diameter portion 14 provided in cylinder 10 with pilot hole 15a, air and the like can be drawn into and exhausted from cylinder 10 more linearly than in the case where a horizontal hole is provided, and since opening 15ac is also adjusted to an opening area that obtains a desired cylinder response speed, the responsiveness for opening and closing the valve is also excellent.

[0030] For example, if only communication between the inside of the cylinder 10 and the outside were to be achieved using the enlarged diameter portion 14, a small air port having only the through portion 15aa communicating with the enlarged diameter portion 14 would suffice, but this could result in an insufficient amount of air being supplied to the cylinder 10. In contrast, according to this embodiment, by providing a rod-side air port 15 with a large diameter including the through portion 15aa and the non-through portion 15ab, it is possible to connect an air pipe capable of supplying a sufficient amount of air. Furthermore, by providing the opening 15ac with an appropriate opening area, it is possible to sufficiently supply air supplied from the air pipe to the inside of the cylinder 10. Furthermore, by having a sufficiently large diameter, the rod-side air port 15 has the through portion 15aa on the rod side and the non-through portion 15ab on the head side, which is farther from the rod side than the through portion 15aa, and therefore does not need a through hole that interferes with the stroke region of the piston 20. As a result, the air-driven actuator 1 is made compact in overall size, and is also able to maintain a sufficiently high response speed, which is essentially a performance that contradicts compactness.

[0031] (Regarding the Piston 20) The piston 20 has a piston rod 21 and a piston head 22 provided at one end of the piston rod 21. The piston head 22 reciprocates integrally with the piston rod 21 by intake and exhaust of air through two air ports 15, 16. A sealing O-ring 22a made of an elastic material is attached to the circumferential surface of the piston head 22 to prevent air from moving between the circumferential surface of the piston head 22 and the inner wall surface 12a of the cylinder 10. Therefore, the piston head 22 reciprocates in the axial direction while the sealing O-ring 22a is in sliding contact with the inner wall surface 12a of the cylinder 10, dividing the interior of the cylinder 10 into two air chambers. The stroke end position of the piston head 22 on the rod side within the cylinder 10 is adjusted to be near the enlarged diameter portion 14. That is, the piston head 22 is able to reciprocate within a range of reciprocation of the piston head 22, including an area A (see FIGS. 2 and 3) of the inner wall surface 12a, which is the non-penetrating portion 15ab of the pilot hole 15a of the rod-side air port 15. The stroke range of the piston 20 is limited by stoppers 17, 41 provided on the closing wall 11 of the cylinder 10 and the housing cap 40, respectively, so that the stoppers can abut against each end of the piston rod 21.

[0032] (Regarding the Housing 30) The housing 30 has a drive space 31 housing a rotation conversion mechanism 60 that converts the reciprocating motion of the piston 20 into rotational motion and transmits it to the output shaft. The housing 30 is connected to the cylinder 10 through the rod-side end 10a. The rotation conversion mechanism 60 provided within the housing 30 employs a so-called Scotch yoke mechanism, including a Scotch yoke 62 that engages with a pin 61 protruding radially outward from the piston rod 21, and a shaft 63 that is connected to the Scotch yoke 62 via a key 64 and rotates as an output shaft. In other words, the rotation conversion mechanism 60 converts the reciprocating motion of the piston 20 into rotational motion of the shaft 63 via the Scotch yoke 62. The shaft 63 extends in an axial direction perpendicular to the piston rod 21 and is connected to a valve stem (not shown). The rotational motion of the valve stem opens and closes a valve element such as a butterfly valve or a ball valve. Note that, although a Scotch yoke mechanism is employed as the rotation conversion mechanism 60 in this embodiment, the present invention is not limited thereto, and a rack-and-pinion mechanism, for example, may also be employed.

[0033] (Regarding the Housing Cap 40) The housing cap 40 has a guide portion that axially guides the piston rod 21 that reciprocates retractably relative to the housing 30, and is attached to the housing 30 from the end opening side of the housing 30.

[0034] (Regarding the piston rod guide 50) The piston rod guide 50 divides the piston reciprocating space 13 from the drive space 31 and guides the piston rod 21. The peripheral edge of the piston rod guide 50 is sandwiched and fixed between the cylinder 10 and the housing 30, with the peripheral edge overlapping the seal member 52, more specifically, between a flange portion 10aa provided on the rod-side end portion 10a of the cylinder 10 and a flange portion 30aa provided on the end portion 30a of the housing 30. The piston rod guide 50 has a through-hole 51 through which the piston rod 21 is inserted so as to be able to reciprocate freely, and guides the piston rod 21 in the axial direction.

[0035] Next, the operation of the air-driven actuator 1 will be described. Here, a series of reciprocating movements of the piston 20 will be described. That is, a series of movements in which the piston 20 moves from a state in which the piston rod 21 is retracted into the cylinder 10 to a state in which the piston rod 21 is pulled out of the cylinder 10, and then returns to a state in which the piston rod 21 is retracted into the cylinder 10 will be described.

[0036] 2 , when the piston rod 21 is retracted into the cylinder 10, i.e., when the piston head 22 is at the stroke terminal position on the head side of the cylinder 10, air is supplied into the cylinder 10 through the head-side air port 16, and the piston head 22 receives a thrust from the air and starts to move toward the rod-side end 10a of the cylinder 10. Note that when the piston head 22 is at the stroke terminal position on the head side of the cylinder 10, the piston rod 21 abuts against a stopper 17 provided on the closing wall 11 of the cylinder 10, causing the piston head 22 to stop at a position separated from the closing wall 11 of the cylinder 10. Therefore, when the piston head 22 is at the stroke terminal position on the head side of the cylinder 10, air flows into the air chamber between the closing wall 11 and the piston head 22 through the head-side air port 16, generating a thrust that moves the piston head 22 toward the stroke terminal position on the rod side of the cylinder 10.

[0037] Thereafter, as shown in FIG. 3 , the piston head 22 moves to a position where the piston rod 21 is pulled out of the cylinder 10, i.e., to the stroke terminal position on the rod side of the cylinder 10. At this time, air inside the cylinder 10 is exhausted to the outside through the rod-side air port 15. More specifically, air inside the cylinder 10 is exhausted from the enlarged diameter portion 14 to the outside through the rod-side air port 15. The piston head 22 also moves to a position near the enlarged diameter portion 14 while the sealing O-ring 22a attached to its circumferential surface is in sliding contact with the inner wall surface 12a of the cylinder 10. At this time, the piston head 22 passes through region A (see FIGS. 2 and 3 ) of the inner wall surface 12a, where the pilot hole 15a does not pass through. Note that when the piston head 22 is at the stroke terminal position on the rod side, the piston rod 21 hits a stopper 41 provided on the housing cap 40, causing the piston head 22 to stop at a position separated from the enlarged diameter portion 14 of the cylinder 10.

[0038] Thereafter, air flows into the cylinder 10 through the rod-side air port 15, generating a thrust that moves the piston head 22 toward the head-side stroke terminal position, causing the piston head 22 to start moving toward the head-side stroke terminal position. The air supplied through the rod-side air port 15 flows into the air chamber between the piston rod guide 50 and the piston head 22 via the enlarged diameter portion 14. At this time, the air inside the cylinder 10 is exhausted to the outside through the head-side air port 16.

[0039] Thereafter, as shown in FIG. 2, the air-driven actuator 1 retracts the piston rod 21 into the cylinder 10, i.e., the piston head 22 moves to the stroke end position on the head side, completing a series of reciprocating movements of the air-driven actuator 1.

[0040] Next, a method for manufacturing the air-driven actuator 1 will be described. Here, a method for manufacturing the cylinder 10 will be described. First, an enlarged-diameter portion 14 with an enlarged inner diameter is provided in the area surrounding the rod-side end 10a of the cylinder 10. The process of providing the enlarged-diameter portion 14 in the cylinder 10 is included in the process of molding the cylinder 10 by casting. That is, in this process, the cylinder 10 having the enlarged-diameter portion 14 is molded by casting. Note that a portion corresponding to the enlarged-diameter portion 14 can be provided in a sand mold for casting the cylinder 10, and the cylinder 10 having the enlarged-diameter portion 14 can be molded using a typical sand casting procedure. That is, providing the enlarged-diameter portion 14 in the cylinder 10 imposes almost no workload. In this embodiment, the enlarged diameter portion 14 has an inner diameter that gradually increases from the extended side to the retracted side of the piston rod 21 in the reciprocating direction of the piston 20. Therefore, in sand casting, the molten metal flows on an inclined surface corresponding to the enlarged diameter portion 14 of the sand mold during pouring, which reduces turbulence and allows the poured metal to flow smoothly into the sand mold, preventing sand from peeling. As a result, quality defects such as sand inclusions are less likely to occur, and processing is easier. Furthermore, in casting using a mold, the molten metal flows on an inclined surface corresponding to the enlarged diameter portion 14 of the mold during pouring, which reduces turbulence and allows the poured metal to flow smoothly into the mold, reducing quality defects and facilitating processing. The enlarged diameter portion 14 may be formed by machining the interior of the cast cylinder 10. By combining casting and machining in this way, it is possible to form the enlarged diameter portion 14 in a wide variety of shapes depending on the air intake and exhaust volume.

[0041] Next, the rod-side air port 15 and the head-side air port 16 are machined. In this process, the rod-side air port 15 and the head-side air port 16 are formed by machining pilot holes 15a, 16a and then machining tapped holes 15b, 16b. The rod-side air port 15 is formed by machining the pilot hole 15a, which includes a through portion 15aa that penetrates into the cylinder 10 by overlapping a portion of the pilot hole 15a radially on the rod side with the enlarged diameter portion 14 in the reciprocating direction of the piston 20 and communicating with the enlarged diameter portion 14, and a non-through portion 15ab that does not penetrate into the cylinder 10 by not overlapping a portion of the pilot hole 15a radially with the enlarged diameter portion 14, and then machining the tapped hole 15b. In this way, the rod-side air port 15 is formed by forming the pilot hole 15a at a position that partially overlaps the enlarged diameter portion 14 in the radial direction, thereby forming an air flow path that penetrates into the cylinder 10 through the enlarged diameter portion 14 while leaving the non-through portion 15ab that does not penetrate into the cylinder 10. On the other hand, the head-side air port 16 is formed by machining a pilot hole 16a penetrating into the cylinder 10 and then machining a tapped hole 16b.

[0042] In the air-driven actuator 1 according to the embodiment of the present invention, the cylinder 10 has an enlarged diameter section 14 whose inner diameter is enlarged in a region adjacent to the piston rod guide 50 in the reciprocating direction of the piston 20, and the rod-side air port 15 provided at the rod-side end 10a has a pilot hole 15a that includes a through portion 15aa that passes through the interior of the cylinder 10 by partially overlapping radially with the enlarged diameter section 14 in the reciprocating direction of the piston 20 and communicating with the enlarged diameter section 14, and a non-through portion 15ab that does not pass through the interior of the cylinder 10 by partially not overlapping radially with the enlarged diameter section 14. In this way, rather than passing the rod-side air port 15 directly through the cylinder 10, a radial portion of the pilot hole 15a is connected to the enlarged diameter section 14 while the remaining portion is a non-through portion, thereby eliminating the need to provide a separate hole for passing the rod-side air port 15 through the cylinder 10. If the piston 20, which reciprocates along the inner wall surface 12a of the cylinder 10, passes through the through-hole of the rod-side air port 15 provided in the wall surface of the cylinder 10, there is a possibility that the piston 20 or a sealing O-ring 22a serving as a piston seal member will be damaged. Therefore, a through-hole must be provided outside the stroke range of the piston 20, but the cylinder 10 will be larger by that distance. As described above, the air-driven actuator 1 according to an embodiment of the present invention can communicate the rod-side air port 15 with the cylinder 10 without providing a separate through-hole that directly communicates with the interior of the cylinder 10. This prevents damage to the piston 20 or the sealing O-ring 22a and also prevents the cylinder 10 from becoming larger. Furthermore, because the rod-side air port 15 communicates with the interior of the cylinder 10 through the enlarged diameter portion 14 without a lateral hole, the complicated machining of a lateral hole is eliminated, and the machining of the rod-side air port 15 is simplified. Furthermore, by adjusting the overlap between the enlarged diameter portion 14 and the pilot hole 15a, a sufficient amount of air can be suctioned and exhausted. Furthermore, since no horizontal hole is provided, and the area other than the portion where the rod-side air port 15 radially overlaps the enlarged diameter portion 14 can be used as the stroke area of ​​the piston 20, the overall dimensions of the cylinder 10 can be reduced, and in the case of a double-acting type, the rod-side air port 15 of the cylinder 10 can be located away from the head-side air port 16 of the cylinder 10.Therefore, machining is easy, the desired cylinder speed can be easily obtained, and furthermore, compactness can be achieved, particularly in the case of a double-acting type, by widening the distance between the two air ports while still achieving compactness.

[0043] Furthermore, in the air-driven actuator 1 according to the embodiment of the present invention, by widening the distance between the two air ports 15, 16, when externally connected devices such as speed controllers are attached to the air ports 15, 16 by screwing them into the tapped holes 15b, 16b, the externally connected devices do not interfere with each other and get in the way, making it easy to assemble the externally connected devices to the air ports 15, 16.

[0044] Furthermore, according to the air-driven actuator 1 of the embodiment of the present invention, the enlarged diameter section 14 has an inner diameter that gradually increases from the extension side of the piston rod 21 toward the retraction side. Therefore, for example, in the case of sand casting, when pouring molten metal, the molten metal flows on an inclined surface corresponding to the enlarged diameter section 14 of the sand mold, which makes the flow less turbulent and prevents sand from peeling. As a result, quality defects such as sand inclusions are less likely to occur, and molding is easier than with an enlarged diameter section formed as a groove of a fixed depth. Furthermore, according to the air-driven actuator 1 of the embodiment of the present invention, the enlarged diameter section 14 gradually increases from the edge side of the enlarged diameter section 14 toward the inner diameter side. Therefore, by adjusting the depth of the pilot hole 15a, the diameter of the communication portion can be easily adjusted, and the amount of air intake and exhaust can be easily set.

[0045] Furthermore, the air-driven actuator 1 according to the embodiment of the present invention has a drive space 31 provided with a rotation conversion mechanism 60 that converts the reciprocating motion of the piston 20 into rotational motion and transmits it to the shaft 63, and has a housing 30 that connects to the cylinder 10 from the rod side end 10a. By mounting the actuator on a valve with the shaft 63 connected to the valve stem, the reciprocating motion of the piston 20 within the compact cylinder 10 is converted into rotational motion of the valve stem via the rotation conversion mechanism 60, opening and closing the valve, and the actuator can be used as a valve actuator that can be assembled compactly to a valve.

[0046] A manufacturing method for an air-driven actuator according to an embodiment of the present invention includes the steps of providing a cylinder 10 having an enlarged diameter section 14 whose inner diameter is enlarged in a region adjacent to the piston rod guide 50 in the reciprocating direction of the piston 20, and forming, as the pilot hole 15a for the rod-side air port 15, the pilot hole 15a which includes a through portion 15aa that penetrates into the cylinder 10 by overlapping a portion of its radial rod side in the reciprocating direction of the piston 20 and communicating with the enlarged diameter section 14, and a non-through portion 15ab that does not penetrate into the cylinder 10 by not overlapping a portion of its radial side with the enlarged diameter section 14. As a result, when applying a method of molding the cylinder 10 using a mold such as casting, for example, it is only necessary to form the cylinder 10 in advance so that the enlarged diameter section 14 is formed, and then form the predetermined pilot hole 15a so that it partially communicates with the enlarged diameter section 14, thereby enabling the rod-side air port 15 to be formed easily and at low cost. In particular, because the rod-side air port 15 communicates with the interior of the cylinder 10 through the enlarged diameter portion 14 without passing through a lateral hole, the complicated machining of a lateral hole is eliminated, and machining of the rod-side air port 15 is facilitated. Furthermore, by adjusting the degree of overlap between the enlarged diameter portion 14 and the pilot hole 15a, a sufficient amount of air can be suctioned and exhausted. Furthermore, because no lateral hole is provided, and the area other than the area where the rod-side air port 15 radially overlaps the enlarged diameter portion 14 can be used as the stroke area of ​​the piston 20, the overall dimensions of the cylinder 10 can be reduced. Furthermore, in the case of a double-acting cylinder, the rod-side air port 15 of the cylinder 10 can be located away from the head-side air port 16 of the cylinder. Therefore, machining is easy, the desired cylinder speed can be easily achieved, and compactness can be achieved, particularly in the case of a double-acting cylinder, by increasing the distance between the two air ports.

[0047] The above describes in detail the embodiments of the present invention, but the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the spirit of the invention described in the claims of the present invention.

[0048] In the above embodiment, a double-acting type is used as the air-driven actuator 1, but as long as there is a cylinder 10 in which the piston 20 reciprocates by intake and exhaust of air through one air port 15 on the rod side, a single-acting type may be used in which the spring force of a spring is used for one of the reciprocating movements of the piston 20. For example, it may be used as a retractable type single-acting air-driven actuator 1. The retractable type means that when air is supplied from one air port 15 on the rod side, the piston rod 21 is retracted into the cylinder, and when air is exhausted from that one air port 15, the piston rod 21 is pushed out of the cylinder by spring force.

[0049] Furthermore, in the above embodiment, the air-driven actuator 1 is used as a drive source for opening and closing a valve, but the air-driven actuator 1 may also be used as a drive source for devices other than valves. For example, it may be used as a drive source for an industrial robot.

[0050] DESCRIPTION OF SYMBOLS 1 Air-driven actuator 10 Cylinder 10a Rod-side end 10aa Flange portion 10b Head-side end 11 Blocking wall 12 Peripheral side wall 12a Inner wall surface 12b Outer wall surface 13 Piston reciprocating space 14 Enlarged diameter portion 14a, 14b Surface 15 Rod-side air port (air port) 15a Pilot hole 15aa Through portion 15ab Non-through portion 15ac Opening 15b Tapped hole 16 Head-side air port (air port) 16a Pilot hole 16b Tapped hole 17 Stopper 20 Piston 21 Piston rod 22 Piston head 22a Sealing O-ring 30 Housing 30a End 30aa Flange portion 31 Drive space 40 Housing cap 41 Stopper 50 Piston rod guide 51 Through hole 52 Seal member 60 Rotation conversion mechanism 61 Pin 62 Scotch yoke 63 Shaft (output shaft) 100 Valve 200 Speed ​​controller

Claims

1. An air-driven actuator having a cylinder with at least one air port provided at an end of a rod side from which a piston rod is pulled out by providing a piston rod guide, and a piston reciprocating space formed therein in which a piston reciprocates by drawing in and exhausting air through the air port, the cylinder has an enlarged diameter portion formed of a groove provided along an inner circumferential direction on an inner wall surface of the cylinder by enlarging an inner diameter in a region adjacent to the piston rod guide in a reciprocating direction of the piston, an air port provided at an end portion on the rod side has a pilot hole including a through portion that penetrates into the cylinder by overlapping a portion of the rod side in a radial direction in the reciprocating direction of the piston and communicating with the enlarged diameter portion, and a non-through portion that does not penetrate into the cylinder by not overlapping a portion of the enlarged diameter portion in the radial direction.

2. 2. The air-driven actuator according to claim 1, wherein the enlarged diameter portion is provided such that an inner diameter gradually increases from the extended side to the retracted side of the piston rod in the reciprocating direction of the piston.

3. The piston has a drive space provided with a rotation conversion mechanism that converts the reciprocating motion of the piston into rotational motion and transmits the rotational motion to an output shaft. The piston has a housing that is connected to the cylinder from an end of the rod side.

3. The air-driven actuator according to claim 1, wherein the output shaft and a valve stem are connected to each other and mounted on a valve.

4. A method for manufacturing an air-driven actuator having a cylinder with at least one air port provided at an end of a rod side from which a piston rod is pulled out by providing a piston rod guide, and a piston reciprocating space formed therein in which a piston reciprocates by drawing in and exhausting air through the air port, comprising: providing the cylinder with an enlarged diameter portion formed of a groove provided along an inner circumferential direction on an inner wall surface by enlarging an inner diameter in a region adjacent to the piston rod guide in a reciprocating direction of the piston; forming a hole as a pilot hole for an air port at an end on the rod side, the pilot hole including a through portion that penetrates into the cylinder by overlapping a portion of the rod side in a radial direction in the reciprocating direction of the piston and communicating with the enlarged diameter portion, and a non-through portion that does not penetrate into the cylinder by not overlapping the enlarged diameter portion in the radial direction.

5. A flange portion is provided at an end portion of the peripheral wall of the cylinder on the rod side, the flange portion protruding radially outward from a portion of the peripheral wall other than the end portion, the enlarged diameter portion is provided on the flange portion, and an outermost diameter position of the enlarged diameter portion is provided on the outer diameter side of an outer wall surface of the circumferential side wall other than the flange portion, 2. The air-driven actuator according to claim 1, wherein the non-penetrating portion of the pilot hole of the air port has a depth that is substantially the same as or shallower than an outer wall surface of the peripheral side wall other than the flange portion.

6. The through-hole is provided on the rod side, The air-driven actuator according to claim 1 , wherein the non-penetrating portion is provided on a side farther from the rod side than the penetrating portion.

7. An air-driven actuator having a cylinder with at least one air port provided at an end of a rod side from which a piston rod is pulled out by providing a piston rod guide, and a piston reciprocating space formed therein in which a piston reciprocates by drawing in and exhausting air through the air port, the cylinder has a flange portion that protrudes outward from an end portion of the cylinder on the rod side relative to a portion other than the end portion, and an enlarged diameter portion that enlarges an inner diameter of the flange portion, The cylinder is an air port provided at the end portion on the rod side is provided so as to overlap at least a portion of the flange portion, and has a through hole communicating with the enlarged diameter portion.

8. 2. The air-driven actuator according to claim 1, wherein the non-penetrating portion does not penetrate into the cylinder, and the rear side of the non-penetrating portion is an inner wall surface area on which a piston head provided at one end of the piston rod can slide.