Method and jig for manufacturing a butterfly valve

Abstract

The present invention provides a method for manufacturing a butterfly valve that prevents deformation of the valve stem even when a pin is welded, maintains the straightness of the valve stem, and allows for smooth rotation of the valve stem. [Solution] When fixing a plate-shaped valve body 5 to a valve stem 4 that is rotatably supported and positioned across a fluid passage 2 formed in a valve casing 1, a pin 10 having a head 11 and a shaft 12 is used. The pin 10 is inserted through the valve stem side through hole 7 and the valve body side through hole 8 from the shaft 12 side, and then the tip of the shaft 12 of the pin 10 is welded around the periphery. When welding the pin 10, the concave pressing body 20 and / or convex pressing body 30 of the jig 100 are moved in a direction that brings them closer to each other, and the valve stem 4 is pressed relative to the tip of the shaft 12 of the pin 10 from the head 11 side to deform it. After welding is complete, the pressure on the valve stem 4 is released.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a butterfly valve and a jig used therefor.

Background Art

[0002] Generally, as shown in FIGS. 10 and 11, as a butterfly valve V that rotates a valve rod fixed with a plate-like valve body to open and close a fluid passage and control fluid, for example, it is used in a throttle device of an internal combustion engine (engine) and is driven by an electric actuator such as a motor under electronic control. This butterfly valve V is disposed across a fluid passage 2 formed in a valve box 1, and includes a valve rod 4 pivotally supported by a bearing portion 3 so as to be rotatable, and a plate-like valve body 5 fixed to the valve rod 4 within the fluid passage 2. The valve rod 4 is rotated by an electric actuator to control the opening degree of the fluid passage 2. The valve body 5 is inserted into a slit 6 formed in the valve rod 4 and is fixed by a pin 10 at symmetric positions on the left and right with respect to the axial center portion of the valve rod 4 (see, for example, Patent Document 1). The pin 10 is composed of a screw having a head portion 11 and a shaft portion 12 projecting from the head portion 11 and having a male thread formed thereon. The valve rod 4 is formed with a valve rod side through hole 7 having an axis in a direction orthogonal to the axial direction thereof and into which the shaft portion 12 of the pin 10 is screwed and inserted. The valve body 5 is formed with a valve body side through hole 8 corresponding to the valve rod side through hole 7 and into which the shaft portion 12 of the pin 10 is screwed and inserted.

[0003] By the way, in this conventional butterfly valve V, the valve body 5 is fixed with a pin 10 made of a screw, but there is a risk that the screw may loosen and fall off. Therefore, in order to prevent this from falling off, it is conceivable to apply an adhesive to the pin 10. However, when using an adhesive, when the fluid is like high-temperature exhaust gas, it is necessary to select a durable adhesive, which becomes expensive and is not preferable. Therefore, for example, using the technique described in Patent Document 2, it is also conceivable to use a technique of caulking the tip of the shaft portion 12 of the pin 10 protruding from the valve rod 4. However, when caulking the pin 10, since the caulking portion protrudes into the fluid passage

[0004] To overcome these shortcomings, a manufacturing method can be considered in which the tip of the shaft portion 12 of the pin 10 is welded to the valve stem 4, for example, using the technology described in Patent Document 3. In this manufacturing method, as shown in Figure 11, the valve stem 4 is pivotally supported in the bearing portion 3 of the valve body 1, and the valve body 5 is inserted through the slit 6 of the valve stem 4. Next, the pin 10 is screwed into the through hole 7 on the valve stem side and the through hole 8 on the valve body side from the shaft portion 12 side. After that, the tip of the shaft portion 12 of the pin 10 is welded around its periphery. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-112088 [Patent Document 2] Japanese Patent Publication No. 2018-115699 [Patent Document 3] Japanese Utility Model Publication No. 53-19831 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when the pin 10 is welded to prevent it from falling out, residual stress and deformation occur due to the welding. Specifically, when the heated welded area W cools, the welded area W side of the valve stem 4 contracts in the direction indicated by the black arrow in Figure 11(a), causing the valve stem 4 to deform. Consequently, along the direction indicated by the dashed arrow in Figure 11(b), the tip side of the shaft portion 12 of the pin 10 becomes concave and the head portion 11 of the pin 10 becomes convex, resulting in a deterioration of the straightness of the valve stem 4. This can cause the valve stem 4 to rotate stiffly relative to the bearing portion 3, potentially hindering its operation.

[0007] This invention has been made in view of the above-mentioned problems, and aims to provide a method for manufacturing a butterfly valve and a jig used therein, which suppresses deformation of the valve stem even when a pin is welded, maintains the straightness of the valve stem, and allows the valve stem to rotate smoothly. [Means for solving the problem]

[0008] To achieve this objective, the present invention provides a method for manufacturing a butterfly valve comprising: a valve body having a fluid passage inside; a valve stem rotatably provided within the valve body, straddling the fluid passage; and a valve body fixed to the valve stem within the fluid passage. A pin having a head and a shaft is used, the valve stem has a valve stem-side through hole through which the shaft of the pin is inserted, with an axis perpendicular to its axial direction, and the valve body has a valve body-side through hole corresponding to the valve stem-side through hole, through which the shaft of the pin is inserted. The valve body is attached to the valve stem by connecting the valve stem-side through hole and the valve body-side through hole to each other. Next, the pin is inserted through the valve stem-side through hole and the valve body-side through hole from its shaft side. Subsequently, when welding the tip of the shaft portion of the pin, the valve stem is pressed relative to the tip of the shaft portion of the pin from the head side of the pin to deform the valve stem, and after welding is completed, the pressure on the valve stem is released.

[0009] Here, the materials for the valve stem, valve body, and pin can include metals such as iron, brass, aluminum, and aluminum alloys, as well as resins. The pin can be any form, such as a screw or rivet, as long as it has a head and a smaller diameter shaft. The welding method can be appropriately selected according to the material requirements of the valve stem and pin, for example, arc welding (non-consumable or consumable electrode), electron beam welding, or laser welding.

[0010] Furthermore, in this invention, the valve stem is deformed during pin welding. This deformation may be plastic or elastic, and can be appropriately selected depending on the material and dimensional conditions of the valve stem, valve body, and pin, as well as the degree of deformation of the valve stem when welding is performed without pressure. The amount of deformation of the valve stem when pressure is applied (pressure applied to the valve stem) can also be appropriately determined according to these conditions. In other words, the valve stem is made straight when welding is completed, the pressure is released, and it returns to room temperature.

[0011] The timing for releasing the pressure after welding should be determined appropriately depending on the type of welding. For example, in the case of welding where heat is distributed evenly and cools slowly, it is desirable to release the pressure after the heat has cooled. On the other hand, in the case of microarc welding, for example, where heat is not distributed evenly and cools quickly, it is desirable to release the pressure immediately after welding.

[0012] As a result, when welding the tip of the pin shaft, the valve stem is pressed relative to the tip of the pin shaft from the head of the pin to deform the valve stem. In other words, welding is performed with the valve stem deformed in the opposite direction to the deformation of the valve stem caused by welding the pin. After welding is complete, the pressure is released as appropriate. In this case, when welding the pin, the weld area melts, and then as the weld area cools, the material solidifies and shrinks, causing the welded side of the valve stem to shrink and the tip of the pin shaft to become concave and the head of the pin to become convex. However, since the valve stem is pressed relative to the tip of the pin shaft from the head of the pin during welding, that is, the tip of the pin shaft is made convex and the head of the pin is made concave, the deformation is canceled out, and the valve stem can maintain its straightness even after welding. As a result, during product use, it is possible to prevent stiffness in the rotation of the valve stem and allow the valve stem to rotate smoothly, thereby improving product quality.

[0013] In this configuration, deformation of the valve stem is achieved by applying pressure to the valve stem from both the tip side of the pin's shaft and the head side of the pin. The concave pressing position on the valve stem, corresponding to the tip side of the pin's shaft, is located at both axial ends of the valve stem, facing the fluid passage. The convex pressing position on the valve stem, corresponding to the head side of the pin, is located in the axial middle of the valve stem, between the concave pressing positions. As a result, while simply pressing the valve stem from the head side of the pin to the tip side of the pin's shaft would place a load on the bearing and valve body, pressing the side ends of the valve stem prevents any load on the bearing and valve body. Therefore, adverse effects on the bearing can be prevented.

[0014] More specifically, when welding the tip of the shaft portion of the pin, a jig is used to press the valve stem. The jig is configured to include a concave pressing body and a convex pressing body. The concave pressing body is inserted into the fluid passage of the valve body and contacts two concave pressing positions on both axial ends of the valve stem facing the fluid passage, pressing the valve stem relatively from the tip of the shaft portion of the pin towards the head of the pin. The convex pressing body is inserted into the fluid passage of the valve body and contacts a convex pressing position in the axial middle portion of the valve stem between the concave pressing positions, pressing the valve stem relatively from the head of the pin towards the tip of the shaft portion of the pin.

[0015] As a result, when welding the tip of the pin shaft, the convex pressing body and / or concave pressing body are moved in a direction that brings them closer to each other to press the valve stem. There are three modes of pressing: (1) The convex pressing body is fixed and the concave pressing body is moved toward the convex pressing body. (2) The concave pressing body is fixed and the convex pressing body is moved toward the concave pressing body. (3) Both the convex and concave pressing bodies are moved in a direction that brings them closer to each other.

[0016] During this pressing process, the concave pressing body presses both axial ends of the valve stem, while the convex pressing body relatively presses the axial center of the valve stem from the side where the pin head is located, causing the valve stem to deform in the required direction. Therefore, this jig ensures that the aforementioned actions and effects are reliably achieved.

[0017] Furthermore, in the present invention, the convex pressing body is formed in a columnar shape that can be inserted into the fluid passage of the valve body, and is provided with a convex contact portion formed in the center of one end thereof that abuts against the convex pressing position of the valve stem. The concave pressing body is formed in a columnar shape that can be inserted into the fluid passage of the valve body, and is provided with concave contact portions formed on both side edges of one end thereof that abut against the concave pressing position of the valve stem, a recess formed between the concave contact portions that allows deformation of the pin shaft portion of the valve stem toward the tip, and a work hole formed through which a welding tool can pass.

[0018] As a result, when the central portion in the axial direction of the valve rod is relatively pressed by the convex-side contact portion of the convex-side pressing body from the side where the head of the pin is located, the head side of the pin is bent and deformed so as to be convex. However, since a recess is formed in the concave-side pressing body, this curved portion enters into this recess, and the valve rod does not abut against the concave-side pressing body, and the curved formation can be surely performed. Further, at the time of welding, since the welding tool can be inserted from the working hole of the concave-side pressing body to the tip of the shaft portion of the pin to perform welding, the welding work of this tip can be surely performed while applying a load to the valve rod.

[0019] Furthermore, in the present invention, the convex-side contact portion of the convex-side pressing body is formed in an arc shape along the outer peripheral shape of the valve rod or in a V shape that makes two-point contact with the outer periphery of the valve rod. The concave-side contact portion of the concave-side pressing body is formed in an arc shape along the outer peripheral shape of the valve rod or in a V shape that makes two-point contact with the outer periphery of the valve rod.

[0020] As a result, since the convex-side contact portion of the convex-side pressing body and the concave-side contact portion of the concave-side pressing body have a shape adapted to the outer periphery of the valve rod, the pressing force can be surely transmitted to the valve rod, and the deformation of the valve rod can be surely performed.

[0021] And also, in order to achieve the above object, the present invention lies in the configuration of the jig used in the above manufacturing method. This jig includes a convex-side pressing body that relatively presses the valve rod from the head side of the pin toward the tip side of the shaft portion of the pin, and a concave-side pressing body that relatively presses the valve rod from the tip side of the shaft portion of the pin toward the head side of the pin.

Effect of the Invention

[0022] As described above, according to the present invention, even when welding a pin for fixing a valve body to a valve rod, deformation of the valve rod can be suppressed, and the straightness of the valve rod can be maintained so that the rotation of the valve rod can be smoothly performed.

Brief Description of the Drawings

[0023] [Figure 1]It is a diagram showing an example of a process in a method for manufacturing a butterfly valve according to an embodiment of the present invention, and is a diagram showing a valve rod and valve body assembly process. [Figure 2] It is a diagram showing an example of a process in a method for manufacturing a butterfly valve according to an embodiment of the present invention, and is a cross-sectional view showing a state where a jig is attached. [Figure 3] It is a diagram showing an example of a process in a method for manufacturing a butterfly valve according to an embodiment of the present invention, and is a cross-sectional view showing a welding process. [Figure 4] It is a diagram showing an example of a process in a method for manufacturing a butterfly valve according to an embodiment of the present invention, and is a cross-sectional view showing a pressing release process. [Figure 5] Cross-sectional view taken along line A-A shown in Figure 2. [Figure 6] Cross-sectional view showing a second example of a jig according to an embodiment of the present invention in a state at the time of its attachment. [Figure 7] Cross-sectional view showing a third example of a jig according to an embodiment of the present invention in a state at the time of its attachment. [Figure 8] It is a diagram showing a fourth example of a jig according to an embodiment of the present invention in a state at the time of its attachment, (a) is a front cross-sectional view, and (b) is a cross-sectional view taken along line B-B shown in Figure 8(a). [Figure 9] Cross-sectional view showing an example of another butterfly valve to which the present invention is applied. [Figure 10] An example of a butterfly valve to which the present invention is applied is shown, (a) is a diagram showing a valve-closed state, and (b) is a diagram showing a valve-open state. [Figure 11] It is a main part cross-sectional view showing a defect of a butterfly valve manufactured by a conventional method for manufacturing a butterfly valve, (a) is a diagram showing the time of welding, and (b) is a diagram showing the time of use.

Embodiments for Carrying Out the Invention

[0024] Hereinafter, based on the accompanying drawings, a method for manufacturing a butterfly valve according to an embodiment of the present invention and a jig used therefor will be described in detail. The same components as those described above will be denoted by the same reference numerals and described.

[0025] Figures 1 to 4 show a method for manufacturing a butterfly valve according to an embodiment of the present invention. The butterfly valve V manufactured by this method is used in the throttle device of an internal combustion engine, as shown in Figure 10, and drives an electric actuator such as a motor by electronic control. The butterfly valve V comprises a valve body 1 with a fluid passage 2 formed therein, a valve stem 4 that is rotatably supported by a bearing portion 3 within the valve body 1, straddling the fluid passage 2, and a plate-shaped valve body 5 fixed to the valve stem 4 within the fluid passage 2. The opening degree of the fluid passage 2 is controlled by rotating the valve stem 4 with an electric actuator. The valve stem 4 is supported at least at two points by a bearing portion 3 shown on the left side of Figure 1 and a bearing portion (not shown) located on the right side of Figure 1.

[0026] More specifically, the valve stem 4 has a slit 6 through which the valve body 5 is inserted. The valve body 5 is inserted through this slit 6 of the valve stem 4 and is secured by a pin 10 at a symmetrical position on either side of the axial center of the valve stem 4 facing the fluid passage 2. The pin 10 consists of a head 11 and a shaft 12 protruding from the head 11 with a male thread formed thereon. The valve stem 4 has a valve stem-side through hole 7 with an axis perpendicular to its axial direction through which the shaft 12 of the pin 10 is screwed in, and the valve body 5 has a valve body-side through hole 8 corresponding to the valve stem-side through hole 7 through which the shaft 12 of the pin 10 is screwed in. Two or more pairs of valve stem-side through holes 7 and valve body-side through holes 8 are provided (two pairs in this embodiment), and each is provided at a symmetrical position on either side of the axial center of the valve stem 4 facing the fluid passage 2. The number of pins 10 used corresponds to the number of through holes 7 on the valve stem side and 8 on the valve body side (two in this embodiment), and the insertion direction of each pin 10 is set to the same direction.

[0027] Furthermore, the valve stem through-hole 7 is constructed with a first hole 7a on the head 11 side of the pin 10 and a second hole 7b on the tip side of the shaft portion 12 of the pin 10, which are formed coaxially. A recess 7c is formed in the first hole 7a into which the head 11 of the pin 10 is receptacled. The valve body 5 is attached by inserting it into the slit 6 of the valve body 5, with the valve stem through-hole 7 and the valve body through-hole 8 communicating with each other, and the pin 10 is screwed into the valve stem through-hole 7 and the valve body through-hole 8 from its shaft portion 12 side. The length of the shaft portion 12 of the pin 10 is set so that when the pin 10 is inserted, its tip does not protrude beyond the second hole 7b. The tip of the shaft portion 12 of the pin 10 is welded around its circumference. The welded portion W of the pin 10 on the second hole 7b side is formed to be substantially flush with the outer surface of the valve stem 4.

[0028] Here, the materials for the valve stem 4, valve body 5, and pin 10 can include metals such as iron, brass, aluminum, and aluminum alloys, as well as resins. In this embodiment, the materials for the valve stem 4, valve body 5, and pin 10 are all stainless steel, but the material is not limited to stainless steel.

[0029] Next, a method for manufacturing a butterfly valve according to an embodiment of the present invention will be described in detail. <Valve stem and valve body assembly process> As shown in Figure 1, the valve stem 4 is mounted on the valve body 1. In this mounting, the valve stem 4 is pivotally supported by the bearing portion 3. Next, the valve body 5 is attached to the valve stem 4. In this case, the valve body 5 is inserted through the slits 7 and 6 of the valve stem 4, and the through-hole 7 on the valve stem side and the through-hole 8 on the valve body side are connected to each other. Then, the valve body 5 is fixed to the valve stem 4 by screwing the pin 10 through the first hole 7a of the valve stem side through-hole 7, the through-hole 8 on the valve body side and the second hole 7b of the valve stem side through-hole 7 from its shaft portion 12 side.

[0030] <Welding Process> After fixing the valve body 5 to the valve stem 4 with the pin 10, the tip of the shaft portion 12 of the pin 10 is welded to the surrounding area. The welding method can be appropriately selected according to the material conditions of the valve stem 4, valve body 5, and pin 10, for example, arc welding (non-consumable or consumable electrode type), electron beam welding, laser welding, etc. In this embodiment, microarc welding was used.

[0031] Before welding, pressure is applied to the valve stem 4 from both the tip end of the shaft portion 12 of the pin 10 and the head end 11 of the pin 10 to deform the valve stem 4. Specifically, as shown in Figures 2 to 4, the valve stem 4 is deformed by relatively pressing it from the head end 11 of the pin 10 to the tip end of the shaft portion 12 of the pin 10. When deforming the valve stem 4, the concave pressing positions 4a and 4b on the valve stem 4, which correspond to the tip end of the shaft portion 12 of the pin 10, are located at both ends of the valve stem 4 in the axial direction and are two locations facing the fluid passage 2. The convex pressing position 4c on the valve stem 4, which corresponds to the head end 11 of the pin 10, is located in the middle of the valve stem 4 in the axial direction and is between the concave pressing position 4a and the concave pressing position 4b.

[0032] The deformation of the valve stem 4 is achieved using a jig 100 for pressing the valve stem 4. The jig 100 according to this embodiment consists of a concave pressing body 20 and a convex pressing body 30. The concave pressing body 20 is located at both axial ends of the valve stem 4 and contacts two concave pressing positions 4a and 4b facing the fluid passage 2, pressing the valve stem 4 relatively from the tip of the shaft portion 12 of the pin 10 towards the head portion 11 of the pin 10. The convex pressing body 30 is inserted into the fluid passage 2 of the valve body 1 and contacts a convex pressing position 4c between the concave pressing positions 4a and 4b in the axial middle portion of the valve stem 4, pressing the valve stem 4 relatively from the head portion 11 of the pin 10 towards the tip of the shaft portion 12 of the pin 10. The convex pressing position 4c of the valve stem 4 by the convex pressing body 30 is preferably an intermediate position of the valve stem 4 facing into the fluid passage 2.

[0033] More specifically, the concave pressing body 20 is formed in a substantially cylindrical shape that can be inserted into the fluid passage 2 of the valve body 1, and is configured to include concave contact portions 21a and 21b formed on both side edges of one end which abut the concave pressing positions 4a and 4b of the valve stem 4, a recess 22 formed between the concave contact portions 21a and 21b which allows deformation toward the tip end of the shaft portion 12 of the pin 10 of the valve stem 4, and a work hole 23 formed through which a welding tool can pass.

[0034] The convex pressing body 30 is formed in a substantially cylindrical shape that can be inserted into the fluid passage 2 of the valve body 1, and is configured to have a convex contact portion 31 formed in the center of one end which abuts against the convex pressing position 4c of the valve stem 4.

[0035] The concave contact portion 21b (21a) of the concave pressing body 20 is recessed along the outer circumference of the valve stem 4 when viewed from a cross section perpendicular to the axis of the valve stem 4, and is formed in an arc shape that provides line contact or surface contact (see Figure 5). Similarly, the convex contact portion 31 of the convex pressing body 30 is recessed along the outer circumference of the valve stem 4 when viewed from a cross section perpendicular to the axis of the valve stem 4, and is formed in an arc shape that provides line contact or surface contact.

[0036] Furthermore, in this embodiment, the convex pressing body 30 is fixed to a base 40 (see Figure 5) which is placed on, for example, a workbench or a press plate. When deforming the valve stem 4, the valve stem 4 is pressed by the concave pressing body 20 while the valve stem 4 is in contact with the convex contact portion 31 of the convex pressing body 30 and the valve body 1 is free to move up and down, thereby deforming the valve stem 4. When deforming the valve stem 4, the valve body 1 itself also moves. By making it possible to deform the valve stem 4 simply by operating the jig 100 with, for example, a press machine, while the valve body 1 is free to move up and down, the device can be simplified. The base 40 is for the purpose of adjusting the height during work, etc., and it is not necessary to use it.

[0037] The deformation of the valve stem 4 may be plastic deformation or elastic deformation, and can be appropriately selected depending on the material and dimensional conditions of the valve stem 4, valve body 5, and pin 10, as well as the degree of deformation of the valve stem 4 when welded without pressure. Furthermore, the amount of deformation of the valve stem 4 when pressed (pressing force on the valve stem 4) can also be appropriately determined according to these conditions. In other words, as will be described later, the valve stem 4 should be straight when the welding is completed, the pressure is released, and it returns to room temperature.

[0038] Therefore, when welding using this jig 100, as shown in Figures 2 to 4, the valve stem 4 is pressed by the concave pressing body 20 while the valve stem 4 is in contact with the convex contact portion 31 of the convex pressing body 30 and the valve body 1 is free to move up and down. As a result, the valve stem 4 deforms while the valve body 1 itself moves. In the valve stem 4, the tip side of the shaft portion 12 of the pin 10 becomes convex, and the head side of the pin 10 becomes concave, resulting in a curved deformation. In this state, the tip of the shaft portion 12 of the pin 10 is welded around the periphery by microarc welding. That is, welding is performed with the valve stem 4 deformed in the opposite direction to the deformation of the valve stem 4 of the pin 10 after welding.

[0039] During this welding process, a welding tool is inserted through the work hole 23 of the concave pressing body 20 to perform the welding. This allows for reliable welding of the tip portion while applying a load to the valve stem 4 using the jig 100. Furthermore, as shown in Figure 4, in this welding process, the welded portion W of the pin 10 is made to be approximately flush with the outer surface of the valve stem 4.

[0040] Furthermore, when pressing the valve stem 4, if the valve stem 4 is simply pressed from the head 11 side of the pin 10 to the tip side of the shaft 12 of the pin 10, there is a risk that a load will be placed on the valve body 1 and the bearing 3, or that unintended deformation of the valve stem 4 may occur. In contrast, in this embodiment, the recessed contact portions 21a and 21b of the recessed pressing body 20 press both axial ends of the valve stem 4 facing the fluid passage 2 from the tip side of the shaft 12 of the pin 10, thereby preventing a load on the valve body 1 and the bearing 3 and unintended deformation of the valve stem 4.

[0041] Furthermore, during this pressing, the convex contact portion 31 of the convex pressing body 30 and the concave contact portions 21a and 21b of the concave pressing body 20 are recessed in an arc shape along the outer circumference of the valve stem 4, so that the pressing force can be reliably transmitted to the valve stem 4 and the deformation of the valve stem 4 can be reliably performed. Moreover, in the valve stem 4, the head 11 side of the pin 10 bends and curves, but since a recess 22 is formed in the concave pressing body 20, this curved portion fits into this recess 22, so the valve stem 4 does not come into contact with the concave pressing body 20 and the curvature can be reliably performed.

[0042] <Pressure release process> As shown in Figure 4, the pressure should be released promptly after welding is complete. In this embodiment, since microarc welding is performed, the heat is not distributed evenly and the material cools down quickly, so it is desirable to release the pressure immediately after welding.

[0043] As a result, as the welded area W cools, the material solidifies and shrinks, causing the welded area W side of the valve stem 4 to shrink and the tip side of the pin 10's shaft portion 12 to become concave and the head side of the pin 10 to become convex. However, during welding, the valve stem 4 is pressed relative to the tip side of the pin 10's shaft portion 12 from the head side of the pin 10, thus deforming the valve stem 4. In other words, the tip side of the pin 10's shaft portion 12 is made convex and the head side of the pin 10 is made concave, so the deformation cancels out, and the valve stem 4 can maintain its straightness even after welding.

[0044] With the butterfly valve V manufactured in this manner, the valve stem 4 maintains its straightness even after welding during use, so there is no stiffness in the rotation of the valve stem 4, and the valve stem 4 can be rotated smoothly. Furthermore, when welding the tip of the shaft portion 12 of the pin 10, the welded portion W of the pin 10 on the second hole 7b side is almost flush with the outer surface of the valve stem 4, so there is almost no part protruding from the valve stem 4, and the area of ​​the fluid passage is not reduced. Due to these effects, the flow rate of the butterfly valve V can be stably controlled. Therefore, the quality of butterfly valve products can be improved.

[0045] The timing for releasing the pressure can be adjusted as appropriate depending on the type of welding, the size of the valve stem and valve body, the material of the valve stem and valve body, etc. For example, if the type of welding is one that easily applies heat over a wider area, it is preferable to release the pressure after the welded area has cooled completely.

[0046] Figure 6 shows a second example of the jig according to the embodiment. This jig 200 is configured in substantially the same way as jig 100, but differs in that the concave contact portions 21a and 21b of the concave pressing body 20 and the convex contact portion 31 of the convex pressing body 30 are each formed in a V-shape that makes two-point contact with the outer circumference of the valve stem 4 when viewed from a cross section perpendicular to the axis of the valve stem 4. The operation and effect of jig 200 are the same as those of jig 100.

[0047] Figure 7 shows a third example of a jig according to the embodiment. This jig 300 is configured in substantially the same way as jig 100, but differs in that the concave contact portions 21a, 21b of the concave pressing body 20 and the convex contact portion 31 of the convex pressing body 30 are formed in a flat shape that makes point contact with the outer circumference of the valve stem 4. Even with a jig 300 having such flat concave contact portions 21a, 21b and convex contact portion 31, the same operation and effect as jig 100 can be expected.

[0048] Figure 8 shows a fourth example of a jig according to the embodiment. This jig 400 has a different shape from the jig 100, which was formed in a cylindrical shape. The concave pressing body 20 of the jig 400 consists of a plate-shaped base 50 that extends in the axial direction of the valve stem 4 and has the same working hole 23 as described above, and a pair of rod-shaped protrusions 51 that protrude from both ends of the base 50 and have concave contact portions 21a (21b) at their tips. The convex pressing body 30 is also formed in a rod shape with a convex contact portion 31 at its tip. The concave contact portions 21a, 21b of the concave pressing body 20 and the convex contact portion 31 of the convex pressing body 30 are each formed in an arc shape that makes line contact or surface contact along the outer circumference shape of the valve stem 4 when viewed from a cross section perpendicular to the axis of the valve stem 4. The operation and effect are the same as those of the jig 100.

[0049] In the jig 400, either the concave contact portion 21a, 21b of the concave pressing body 20 or the convex contact portion 31 of the convex pressing body 30 may be formed in an arc shape that makes line contact or surface contact along the outer circumference shape of the valve stem 4 when viewed from a cross section perpendicular to the axis of the valve stem 4, and the other may be formed in a V shape that makes two-point contact with the outer circumference of the valve stem 4, and these can be modified as appropriate.

[0050] In the above embodiment, the convex pressing body 30 is fixed and the concave pressing body 20 is moved toward the convex pressing body 30, but the embodiment is not necessarily limited to this. The concave pressing body 20 may be fixed and the convex pressing body 30 may be moved toward the concave pressing body 20. Alternatively, both the concave pressing body 20 and the convex pressing body 30 may be moved toward each other, and the embodiment can be modified as appropriate.

[0051] In the above embodiment, an example was shown in which a screw was used as the pin 10 of the butterfly valve V. However, the invention is not necessarily limited to this, and a rivet-shaped pin without a male thread formed on the shaft portion 12 may also be used, and modifications may be made as appropriate. Furthermore, in the above embodiment, an example was shown in which the butterfly valve V was provided with two sets of through holes 7 on the valve stem side and through holes 8 on the valve body side. However, the invention is not necessarily limited to this. For example, it can also be applied to a type in which another set is provided at the axial center of the valve stem 4 facing the fluid passage 2, resulting in a total of three sets, or even four or more sets. Moreover, in the above embodiment, an example was shown in which the butterfly valve V was provided with a type in which the valve body 5 is inserted through a slit 6 formed in the valve stem 4. However, the invention is not necessarily limited to this. For example, as shown in Figure 9, it can also be applied to a type in which the valve body 5 is fitted into a recess 60 formed on one side perpendicular to the axis of the valve stem 4 and fixed with a screw pin 10, and modifications may be made as appropriate.

[0052] Furthermore, while the butterfly valve V in the above embodiments is one used in the throttle device of an internal combustion engine, it is not necessarily limited to this. For example, it is certainly applicable to various other types of butterfly valves, such as throttle valves, power valves, swirl control valves, and tumble control valves. In short, those skilled in the art will find it easy to make many modifications to these exemplary embodiments without substantially departing from the novel teachings and effects of the present invention, and many of these modifications fall within the scope of the present invention. [Explanation of Symbols]

[0053] V Butterfly Valve 1. Valve box 2 Fluid passage 3 Bearing section 4 valve stems 4a Concave side pressing position 4b Concave side pressing position 4c Convex side pressing position 5 Valve body 6 slits 7 Valve stem side through hole 7a First hole 7b Second hole 7c recess 8 Valve body side through hole 10 pins 11 Head 12 Shaft section 20 Concave side pressing body 21a Concave side contact part 21b Concave side contact part 22 recess 23 Working holes 30 Convex pressing body 31 Convex side contact part 40 bases 50 base 51 Protruding structure 60 recesses 100 jigs 200 jigs 300 jigs 400 jigs

Claims

1. A method for manufacturing a butterfly valve comprising a valve body having a fluid passage inside, a valve stem rotatably provided within the valve body straddling the fluid passage, and a valve body fixed to the valve stem within the fluid passage, A pin having a head and a shaft is used, the valve stem has a through hole on the valve stem side having an axis perpendicular to its axial direction, through which the shaft of the pin is inserted, and the valve body has a through hole on the valve body side corresponding to the through hole on the valve stem side, through which the shaft of the pin is inserted. A method for manufacturing a butterfly valve, characterized by: connecting the valve stem through-hole and the valve body through-hole to each other and attaching the valve body to the valve stem; inserting the pin through the valve stem through-hole and the valve body through-hole from its shaft side; then, when welding the tip of the shaft of the pin to the surrounding area, relatively pressing the valve stem from the head side of the pin to the tip of the shaft of the pin to deform the valve stem; and releasing the pressure on the valve stem after welding is completed.

2. The deformation of the valve stem is caused by applying pressure to the valve stem from both the tip side of the pin's shaft and the head side of the pin. The recessed pressing positions on the valve stem, corresponding to the tip end of the pin's shaft, are two locations on both axial ends of the valve stem, facing the fluid passage. The method for manufacturing a butterfly valve according to claim 1, characterized in that the convex pressing position on the head side of the pin in the valve stem is in the axial middle portion of the valve stem and is between the concave pressing positions.

3. The deformation of the valve stem is performed using a jig. The jig described above, A recessed pressing body is inserted into the fluid passage of the valve body and contacts two recessed pressing positions on both axial ends of the valve stem facing the fluid passage, thereby relatively pressing the valve stem from the tip of the shaft of the pin towards the head of the pin. A method for manufacturing a butterfly valve according to claim 2, characterized in that it comprises a convex pressing body inserted into the fluid passage of the valve body, which is located in the axial middle portion of the valve stem and contacts the convex pressing position between the concave pressing positions, thereby relatively pressing the valve stem from the head side of the pin towards the tip side of the shaft of the pin.

4. The recessed pressing body is formed in a columnar shape that can be inserted into the fluid passage of the valve body, and comprises recessed contact portions formed on both side edges of one end thereof that abut against the recessed pressing position of the valve stem, a recess formed between the recessed contact portions that allows deformation of the pin shaft portion of the valve stem toward the tip, and a working hole formed through which a welding tool can pass. The method for manufacturing a butterfly valve according to claim 3, characterized in that the convex pressing body is formed in a columnar shape that can be inserted into the fluid passage of the valve body, and is provided with a convex contact portion formed in the center of one end thereof that abuts against the convex pressing position of the valve stem.

5. The recessed contact portion of the recessed pressing body is formed in an arc shape that follows the outer circumference shape of the valve stem or in a V shape that makes contact with the outer circumference of the valve stem at two points. The method for manufacturing a butterfly valve according to claim 4, characterized in that the convex contact portion of the convex pressing body is formed in an arc shape that follows the outer circumference shape of the valve stem or in a V shape that makes two-point contact with the outer circumference of the valve stem.

6. A jig used in the method for manufacturing a butterfly valve according to any one of claims 1 to 5, A concave pressing body that presses the valve stem relative to the head side of the pin from the tip side of the shaft portion of the pin, A jig characterized by comprising a convex pressing body that presses the valve stem relative to the tip of the shaft portion of the pin from the head side of the pin.

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