Manufacturing method and jig for butterfly valve

Abstract

This invention provides a method for manufacturing a butterfly valve that can suppress valve stem deformation even when a welding pin is used, and can maintain the straightness of the valve stem to allow for smooth valve stem rotation. When a plate-shaped valve core (5) is configured to be rotatable and supported by a shaft in a fluid passage (2) formed across the valve body (1), a pin (10) having a head (11) and a shaft portion (12) is used. The pin (10) is inserted from its shaft portion (12) side into a through hole (7) on the valve stem side and a through hole (8) on the valve core side. Then, the front end of the shaft portion (12) of the pin (10) is welded to the surrounding area. When welding the pin (10), the concave pressing body (20) and / or convex pressing body (30) of the clamp (100) are moved toward each other, and the valve stem is pressed relative to the front end of the shaft portion (12) of the pin (10) from the head (11) side to deform it. After welding, the pressing of the valve stem is released.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a butterfly valve and a fixture for using it. Background Technology

[0002] Generally, such as Figure 10A , Figure 10B , Figure 11A and Figure 11B As shown, a butterfly valve V is known to open and close a fluid passage and control fluid by rotating a valve stem with a plate-shaped valve core fixed thereon. Examples include butterfly valves used in throttle valve devices of internal combustion engines (engines) and those driven by electric actuators such as motors via electronic control. This butterfly valve V has a valve stem 4 and a plate-shaped valve core 5. The valve stem 4 is positioned across a fluid passage 2 formed in the valve body 1 and is rotatably supported by a bearing portion 3. The valve core 5 is 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 via an electric actuator. The valve core 5 is inserted through a slit 6 formed in the valve stem 4 and is fixed by a pin 10 to a position symmetrically positioned to the left and right of the axial center portion of the valve stem 4 (see, for example, Patent Document 1). The pin 10 consists of a screw having a head 11 and a shaft portion 12 protruding from the head 11 and having external threads. A valve stem side through hole 7 is formed in the valve stem 4. The valve stem side through hole 7 has an axis orthogonal to the axis of the valve stem 4. A shaft portion 12 with a pin 10 is screwed in and inserted through it. A valve core side through hole 8 is formed in the valve core 5. The valve core side through hole 8 corresponds to the valve stem side through hole 7 and a shaft portion 12 with a pin 10 is screwed in and inserted through it.

[0003] However, in the conventional butterfly valve V, although the valve core 5 is fixed with a pin 10 made of screws, it may fall off due to loosening of the screws. Therefore, to prevent this, it is advisable to apply adhesive to the pin 10. However, when using adhesive, a durable adhesive is required when the fluid is high-temperature exhaust, which is expensive and not preferred. Therefore, for example, the technology described in Patent Document 2 can be considered, using a method of riveting the front end of the shaft portion 12 of the pin 10 protruding from the valve stem 4. However, when riveting the pin 10, since the riveted portion protrudes further into the fluid passage 2 than the valve stem 4, there is a disadvantage of correspondingly reducing the area of ​​the fluid passage.

[0004] To address these drawbacks, for example, a manufacturing method described in Patent Document 3, which involves welding the front end of the shaft portion 12 of the pin 10 to the valve stem 4, could be considered. This manufacturing method is as follows... Figure 11A , Figure 11B As shown, the valve stem 4 is supported on the bearing portion 3 of the valve body 1, and the valve core 5 is inserted through the slit 6 attached to the valve stem 4. Next, the pin 10 is screwed in from its shaft portion 12 side and inserted through the through hole 7 on the valve stem side and the through hole 8 on the valve core side. Afterwards, the front end of the shaft portion 12 of the pin 10 is welded to the surrounding area.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-112088 Patent Document 2: Japanese Patent Application Publication No. 2018-115699 Patent Document 3: Japanese Published Patent No. 53-19831 Summary of the Invention The problem the invention aims to solve However, when the pin 10 is welded to prevent it from falling off, residual stress or deformation will occur due to the welding. That is, when the heated welded part W cools, the welded part W of the valve stem 4 will laterally deform. Figure 11A The valve stem 4 contracts in the direction indicated by the black arrow. Therefore, the valve stem 4 contracts along... Figure 11B As indicated by the dashed arrow, the front end of the shaft portion 12 of the pin 10 is recessed, and the head 11 of the pin 10 is bent in a way that causes the straightness of the valve stem 4 to deteriorate, resulting in the valve stem 4 not rotating smoothly relative to the bearing portion 3 and causing an obstruction to the operation.

[0006] The present invention was made in view of the above-mentioned problems, and its object is to provide a method for manufacturing a butterfly valve and a fixture used in the manufacturing method, so as to suppress the deformation of the valve stem even when welding pins, maintain the straightness of the valve stem, and allow the valve stem to rotate smoothly.

[0007] means for solving problems To achieve this objective, the manufacturing method of the butterfly valve of the present invention is a method for manufacturing a butterfly valve having the following components: a valve body having a fluid passage inside; a valve stem rotatably disposed within the valve body, spanning the fluid passage; and a valve core fixed to the valve stem within the fluid passage. A valve stem-side through hole is formed in the valve stem using a pin having a head and a shaft portion. The valve stem-side through hole has an axis orthogonal to the axial direction of the valve stem, through which the shaft portion of the pin passes. A valve core-side through hole is formed in the valve core, corresponding to the valve stem-side through hole, through which the shaft portion of the pin passes. The valve stem-side through hole and the valve core-side through hole are interconnected, and the valve core is attached to the valve stem. Then, the pin is inserted from its shaft portion side into the valve stem-side through hole and the valve core-side through hole. Then, when welding the front end of the pin's shaft portion, the valve stem is pressed from the head side of the pin toward the front end of the pin's shaft portion to deform the valve stem. After welding is completed, the pressure on the valve stem is released.

[0008] Here, the materials for the valve stem, valve core, and pin can include metals such as iron, brass, aluminum, and aluminum alloys, as well as resin. Furthermore, for the pin, any component with a head and a shaft portion smaller than the head, such as a screw or rivet, is acceptable, regardless of its shape. Additionally, welding methods include, for example, arc welding (non-consumable electrode or consumable electrode), electron beam welding, and laser welding, which can be appropriately selected based on the material conditions of the valve stem and pin.

[0009] Furthermore, in this invention, the valve stem is deformed during the welding of the pin. This deformation can be either plastic or elastic, and can be appropriately selected based on the material and dimensional conditions of the valve stem, valve core, and pin, as well as the degree of deformation of the valve stem when welding is performed without pressure. Additionally, the amount of deformation of the valve stem during pressing (the pressing force on the valve stem) can also be appropriately determined based on these conditions. That is, after welding is completed and the pressure is released, the valve stem becomes straight when it reaches room temperature.

[0010] The timing of releasing the pressure after welding is appropriately determined according to the type of welding. For example, in the case of welding where heat is applied to the entire surface and is difficult to cool, it is preferable to release the pressure after the heat has cooled down. Alternatively, for example, in the case of micro-arc welding, since heat is relatively difficult to apply to the entire surface and is easy to cool down, it is preferable to release the pressure immediately after welding.

[0011] Therefore, when welding the front end of the pin's shaft, the valve stem is pressed against the front end of the pin's shaft from the head side to deform it. That is, welding is performed while the valve stem is deformed in the opposite direction to the deformation caused by welding the pin. After welding, the pressing is released at an appropriate time. In this case, the welded portion melts during pin welding, and then, as the welded portion cools, the material solidifies and shrinks, causing the welded portion of the valve stem to shrink, and the valve stem to bend and deform in a direction that is concave towards the front end of the pin's shaft and convex towards the head side of the pin. However, because the valve stem is deformed by pressing against the front end of the pin's shaft from the head side during welding—that is, by causing the front end of the pin's shaft to convex and the head side of the pin to bend and deform—this deformation is offset, and the valve stem can maintain its straightness after welding. As a result, when using the product, it is possible to prevent uneven rotation of the valve stem, ensuring smooth rotation and thus improving product quality.

[0012] In this structure, the deformation of the valve stem is achieved by applying pressure to the valve stem from both the front end side of the pin's shaft and the head side of the pin. The concave pressing positions on the front end side of the valve stem, corresponding to the pin's shaft, are located at two points on both axial ends of the valve stem and facing the fluid passage. The convex pressing positions on the head side of the valve stem are located at the axial middle of the valve stem and between the concave pressing positions. Therefore, when the valve stem is pressed only from the head side towards the front end side of the pin's shaft, a load is applied to the bearing or valve body; however, because the side ends of the valve stem are pressed, no load is applied to the bearing or valve body. Thus, adverse effects on the bearing are prevented.

[0013] More specifically, when welding the front end of the pin's shaft portion, a clamp for pressing the valve stem is used. The clamp is configured to have a concave pressing body and a convex pressing body. The concave pressing body is inserted into the fluid passage of the valve body, abutting against two concave pressing positions on the axial ends of the valve stem facing the fluid passage, pressing the valve stem from the front end of the pin's shaft portion toward the head of the pin. The convex pressing body is inserted into the fluid passage of the valve body, abutting against the convex pressing position on the axial middle portion of the valve stem between the concave pressing positions, pressing the valve stem from the head of the pin toward the front end of the pin's shaft portion.

[0014] Therefore, when welding the front end of the shaft of the pin, the convex pressing body and / or the concave pressing body are moved toward each other and the valve stem is pressed. There are three pressing forms: (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) The convex pressing body and the concave pressing body are moved toward each other in both directions.

[0015] During this pressing action, the concave pressing body presses down on both axial ends of the valve stem, while the convex pressing body presses down on the axial center of the valve stem from the side where the pin head is located, causing the valve stem to deform in the desired direction. Therefore, this clamp can reliably perform the aforementioned functions and effects.

[0016] Furthermore, in this invention, the convex-side pressing body is formed as a column capable of being inserted into the fluid passage of the valve body, and is configured to have a convex-side abutment portion formed at the center of one end of the convex-side pressing body, abutting against the convex-side pressing position of the valve stem. The concave-side pressing body is formed as a column capable of being inserted into the fluid passage of the valve body, and is configured to have: a concave-side abutment portion formed at both sides of one end of the concave-side pressing body, abutting against the concave-side pressing position of the valve stem; a recess formed between the concave-side abutment portions, allowing the valve stem to deform towards the front end of the pin's shaft portion; and a working hole formed through it so that a welding tool can pass through.

[0017] Therefore, if the axial central portion of the valve stem is pressed against the convex abutment portion of the convex pressing body from the side where the pin head is located, it will bend and deform in such a way that the pin head side bends into a convex shape. However, because a concave portion is formed in the concave pressing body, the bent portion enters the concave portion, and the valve stem will not collide with the concave pressing body, thus reliably forming the bending shape. In addition, during welding, since a welding tool can be inserted into the front end of the pin shaft through the working hole of the concave pressing body for welding, the welding operation of the front end portion can be reliably performed while applying a load to the valve stem.

[0018] Furthermore, in this invention, the convex abutment portion of the convex pressing body is formed as an arc along the outer periphery of the valve stem or a V-shape that contacts two points on the outer periphery of the valve stem. The concave abutment portion of the concave pressing body is formed as an arc along the outer periphery of the valve stem or a V-shape that contacts two points on the outer periphery of the valve stem.

[0019] Therefore, since the convex abutment portion of the convex pressing body and the concave abutment portion of the concave pressing body are shaped to match the outer periphery of the valve stem, the pressing force can be reliably transmitted to the valve stem, and the deformation of the valve stem can be reliably carried out.

[0020] Furthermore, in order to achieve the aforementioned objective, the present invention is configured as a fixture used in the manufacturing method described above. This fixture is configured to have: a convex pressing body that presses the valve stem relative to the front end of the pin's shaft portion from the head side of the pin; and a concave pressing body that presses the valve stem relative to the head side of the pin's shaft portion from the front end of the pin's shaft portion.

[0021] Invention Effects As explained above, according to the present invention, even if the pin for fixing the valve core is welded to the valve stem, deformation of the valve stem can be suppressed, and the straightness of the valve stem can be maintained so that the rotation of the valve stem can proceed smoothly. Attached Figure Description

[0022] Figure 1This is a diagram illustrating an example of a process in the manufacturing method of a butterfly valve according to an embodiment of the present invention, and a diagram illustrating the assembly process of the valve stem and valve core.

[0023] Figure 2 This is a diagram illustrating an example of a process in the manufacturing method of a butterfly valve according to an embodiment of the present invention, and is a cross-sectional view showing the state in which the fixture is installed.

[0024] Figure 3 This is a diagram illustrating an example of a process in the manufacturing method of a butterfly valve according to an embodiment of the present invention, and a cross-sectional view showing the welding process.

[0025] Figure 4 This is a diagram illustrating an example of a process in the manufacturing method of a butterfly valve according to an embodiment of the present invention, and a cross-sectional view showing the press-to-release process.

[0026] Figure 5 yes Figure 2 The AA-line sectional view shown.

[0027] Figure 6 This is a cross-sectional view showing a second example of the clamp according to an embodiment of the present invention in its installed state.

[0028] Figure 7 This is a cross-sectional view showing a third example of the clamp according to an embodiment of the present invention in its installed state.

[0029] Figure 8A , Figure 8B This is a diagram showing the fourth example of the clamp according to an embodiment of the present invention in its installed state. Figure 8A It is a front sectional view. Figure 8B yes Figure 8A The BB line section view shown.

[0030] Figure 9 This is a cross-sectional view illustrating an example of another butterfly valve to which the present invention is applicable.

[0031] Figure 10A , Figure 10B An example of a butterfly valve to which this invention is applicable is shown. Figure 10A This is a diagram showing the valve in the closed state. Figure 10B This is a diagram showing the valve in the open state.

[0032] Figure 11A , Figure 11B This is a cross-sectional view showing the key defects of a butterfly valve manufactured using conventional butterfly valve manufacturing methods. Figure 11A This is a diagram showing the welding process. Figure 11B This is a diagram showing how it is used.

[0033] Explanation of reference numerals in the attached figures V: Butterfly valve 1: Valve body 2: Fluid pathway 3: Bearing section 4: Valve stem 4a: Concave side pressing position 4b: Concave side pressing position 4c: Convex side pressing position 5: Valve core 6: Slit 7: Through hole on the valve stem side 7a: First hole 7b: Second hole 7c: Recess 8: Through hole on the valve core side 10: Sales 11: Head 12: Shaft 20: Concave side pressing body 21a: Concave side abutment portion 21b: Concave side abutment portion 22: concave part 23: Working Hole 30: Convex side pressing body 31: Convex side contact portion 40: Abutment 50: Base 51: Highlight the body 60: Concave 100: Fixture 200: Fixture 300: Fixture 400: Fixture Detailed Implementation Hereinafter, a method for manufacturing a butterfly valve according to an embodiment of the present invention and the fixture used in the manufacturing method will be described in detail based on the accompanying drawings. Furthermore, the same reference numerals will be used to denote the same parts as described above.

[0034] Figures 1 to 4 The invention illustrates a method for manufacturing a butterfly valve according to an embodiment of the present invention. For example... Figure 10A , Figure 10B As shown, the butterfly valve V manufactured by this method is used in the throttle valve device of an internal combustion engine (engine) and is driven by an electric actuator such as a motor via electronic control. The butterfly valve V includes: a valve body 1 forming a fluid passage 2; a valve stem 4 spanning the fluid passage 2 and rotatably supported by a bearing portion 3 within the valve body 1; and a plate-shaped valve core 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 via an electric actuator. The valve stem 4 is... Figure 1 The bearing part 3 shown in the left diagram and located in Figure 1The bearing portion on the right (not shown) is supported by the shaft in at least two places.

[0035] In detail, a slit 6 is formed in the valve stem 4 for the valve core 5 to be inserted. The valve core 5 is inserted into the slit 6 of the valve stem 4 and is fixed by a pin 10 at a symmetrical position bounded by the axial center portion of the valve stem 4 facing the fluid passage 2. The pin 10 is a screw having a head 11 and a shaft portion 12 protruding from the head 11 and having external threads. A valve stem side through hole 7 is formed in the valve stem 4, and the valve stem side through hole 7 has an axis orthogonal to the axial direction of the valve stem 4. The shaft portion 12 through which the pin 10 is inserted is screwed in. A valve core side through hole 8 is formed in the valve core 5, and the valve core side through hole 8 corresponds to the valve stem side through hole 7. The shaft portion 12 through which the pin 10 is inserted is screwed in. Two or more sets of valve stem side through holes 7 and valve core side through holes 8 are provided (two sets in the embodiment), and they are respectively set at symmetrical positions bounded by the axial center portion 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 through holes 8 on the valve core side (two in the embodiment), and the insertion direction of each pin 10 is set to the same direction.

[0036] Furthermore, the valve stem-side through hole 7 is configured such that a first hole 7a is coaxially formed on the head 11 side of the pin 10 and a second hole 7b is formed on the front end side of the shaft portion 12 of the pin 10. A recess 7c is formed in the first hole 7a for the head 11 of the pin 10 to enter. The valve core 5 is inserted into the slit 6 of the valve stem 4, communicating with the valve stem-side through hole 7 and the valve core-side through hole 8. The pin 10 is screwed in from its shaft portion 12 side and passes through the valve stem-side through hole 7 and the valve core-side through hole 8. The length of the shaft portion 12 of the pin 10 is set to a length such that its front end does not protrude from the second hole 7b when the pin 10 is inserted. In addition, the front end of the shaft portion 12 of the pin 10 is welded around it. The welded portion W of the pin 10 on the second hole 7b side is formed to be approximately coplanar with the outer surface of the valve stem 4.

[0037] Here, the materials used for the valve stem 4, valve core 5, and pin 10 include metals such as iron, brass, aluminum, and aluminum alloys, as well as resin. In this embodiment, the valve stem 4, valve core 5, and pin 10 are all made of stainless steel, but the materials are not limited to this.

[0038] Next, the manufacturing method of the butterfly valve according to the embodiments of the present invention will be described in detail.

[0039] <Valve stem and valve core assembly process> like Figure 1As shown, a valve stem 4 is installed on the valve body 1. In this installation, the valve stem 4 is axially supported on the bearing portion 3. Next, the valve core 5 is attached to the valve stem 4. In this case, the valve core 5 is inserted through the slit 6 of the valve stem 4, so that the valve stem side through hole 7 and the valve core side through hole 8 are interconnected. Then, the valve core 5 is fixed to the valve stem 4 by screwing the pin 10 from its shaft portion 12 side and inserting it through the first hole 7a of the valve stem side through hole 7, the valve core side through hole 8, and the second hole 7b of the valve stem side through hole 7.

[0040] <Welding Process> After the valve core 5 is fixed to the valve stem 4 by the pin 10, the front end of the shaft portion 12 of the pin 10 is welded to the surrounding area. Welding methods include, for example, arc welding (non-consumable electrode or consumable electrode), electron beam welding, laser welding, etc., which can be appropriately selected according to the material conditions of the valve stem 4, valve core 5, and pin 10. In this embodiment, micro-arc welding is used.

[0041] Before welding, pressure is applied to the valve stem 4 from both the front end of the shaft portion 12 of the pin 10 and the head 11 of the pin 10 to deform the valve stem 4. Specifically, as follows... Figures 2 to 4 As shown, the valve stem 4 is deformed by pressing it against the front end of the shaft portion 12 of the pin 10 from the head 11 side. Furthermore, when deforming the valve stem 4, the concave pressing positions 4a and 4b of the valve stem 4, corresponding to the front end of the shaft portion 12 of the pin 10, are located at both axial ends of the valve stem 4 and face into the fluid passage 2. The convex pressing position 4c of the valve stem 4, corresponding to the head 11 side of the pin 10, is located at the axial middle of the valve stem 4 and lies between the concave pressing position 4a and the concave pressing position 4b.

[0042] The deformation of the valve stem 4 is achieved using a clamp 100 for pressing the valve stem 4. The clamp 100 in this embodiment includes a concave pressing body 20 and a convex pressing body 30. The concave pressing body 20 abuts against two concave pressing positions 4a and 4b on the axial ends of the valve stem 4 and facing the fluid passage 2, pressing the valve stem 4 relative to each other from the front end of the shaft portion 12 of the pin 10 towards the head 11 of the pin 10. The convex pressing body 30 is inserted into the fluid passage 2 of the valve body 1, abutting against a convex pressing position 4c on the axial middle portion of the valve stem 4 between the concave pressing positions 4a and 4b, pressing the valve stem 4 relative to each other from the head 11 of the pin 10 towards the front end of the shaft portion 12 of the pin 10. The convex pressing position 4c of the convex pressing body 30 on the valve stem 4 is preferably the middle position of the valve stem 4 facing the fluid passage 2.

[0043] In detail, the concave pressing body 20 is formed into a generally cylindrical shape that can be inserted into the fluid passage 2 of the valve body 1, and is configured to have: concave abutment portions 21a and 21b, formed on both sides of one end of the concave pressing body 20, abutting against the concave pressing positions 4a and 4b of the valve stem 4; a recess 22, formed between the concave abutment portions 21a and 21b, allowing the valve stem 4 to deform toward the front end of the shaft portion 12 of the pin 10; and a working hole 23, which is formed through so that welding tools can pass through.

[0044] The convex pressing body 30 is formed into a generally cylindrical shape that can be inserted into the fluid passage 2 of the valve body 1, and is configured to have a convex abutment portion 31 formed at the center of one end and abutting against the convex pressing position 4c of the valve stem 4.

[0045] Viewed from a cross section orthogonal to the axis of valve stem 4, the concave abutment portion 21b (21a) of the concave pressing body 20 is recessed along the outer periphery of valve stem 4, forming an arc shape of line contact or surface contact (see reference). Figure 5 Furthermore, when viewed from a cross section orthogonal to the axis of the valve stem 4, the convex abutment portion 31 of the convex pressing body 30 is recessed along the outer periphery of the valve stem 4, forming an arc shape of line contact or surface contact.

[0046] Furthermore, in the embodiment, the convex pressing body 30 is fixed, for example, to a base 40 mounted on a platform such as a worktable or a stamping machine (see reference). Figure 5 When deforming the valve stem 4, with the valve stem 4 in contact with the convex abutment portion 31 of the convex pressing body 30 and the valve body 1 free to move up and down, the valve stem 4 is deformed by pressing the valve stem 4 with the concave pressing body 20. When deforming the valve stem 4, the valve body 1 itself also moves. With the valve body 1 free to move up and down, the valve stem 4 can be deformed simply by using a clamp 100 such as a stamping machine, thus simplifying the device. The base 40 is used to adjust the height during operation, etc., and may not be used.

[0047] The deformation of valve stem 4 can be either plastic or elastic, and can be appropriately selected based on the material and dimensional conditions of valve stem 4, valve core 5, and pin 10, as well as the degree of deformation of valve stem 4 when welding is performed without pressure. Furthermore, the amount of deformation of valve stem 4 during pressing (the pressing force on valve stem 4) can also be appropriately determined based on these conditions. That is, as will be described later, after welding is completed and pressure is released, valve stem 4 becomes straight when the temperature returns to normal.

[0048] Therefore, when using the fixture 100 for welding, such as Figures 2 to 4As shown, with the valve stem 4 abutting against the convex contact portion 31 of the convex pressing body 30 and the valve body 1 moving freely up and down, the valve stem 4 is pressed by the concave pressing body 20. This causes the valve body 1 to move as well, and the valve stem 4 deforms. The valve stem 4 is bent and deformed such that the front end of the shaft portion 12 of the pin 10 becomes convex, and the head 11 of the pin 10 becomes concave. In this state, the front end of the shaft portion 12 of the pin 10 is welded around the valve stem 4 using micro-arc welding. That is, welding is performed while the valve stem 4 is deformed in the opposite direction to the deformation of the valve stem 4 after welding the pin 10. During welding, a welding tool is inserted through the working hole 23 of the concave pressing body 20 to perform welding. Therefore, welding of the front end can be reliably performed while applying a load to the valve stem 4 via the clamp 100. Additionally, as... Figure 4 As shown, in this welding, the welding part W of pin 10 is made to be approximately coplanar with the outer surface of valve stem 4.

[0049] Furthermore, when pressing the valve stem 4, if the valve stem 4 is pressed only from the head 11 side of the pin 10 towards the front end of the shaft portion 12 of the pin 10, it is possible to apply a load to the valve body 1 or the bearing portion 3, or cause unexpected deformation of the valve stem 4. In this embodiment, since the concave abutment portions 21a and 21b of the concave pressing body 20 press the valve stem 4 from the front end of the shaft portion 12 of the pin 10 towards both axial ends facing the fluid passage 2, it is possible to prevent the application of a load to the valve body 1 or the bearing portion 3 or unexpected deformation of the valve stem 4.

[0050] Furthermore, during the pressing process, because the convex abutment portion 31 of the convex pressing body 30 and the concave abutment portions 21a and 21b of the concave pressing body 20 are recessed into an arc shape along the outer periphery of the valve stem 4, the pressing force can be reliably transmitted to the valve stem 4, and the deformation of the valve stem 4 can be reliably carried out. Moreover, the valve stem 4 is bent and deformed in a convex shape by bending the head 11 side of the pin 10, but because the concave pressing body 20 has a recess 22, the bent portion enters the recess 22, and the valve stem 4 will not collide with the concave pressing body 20, so the bending formation can be reliably carried out.

[0051] <Press Release Procedure> like Figure 4 As shown, the pressure is released in a timely manner after welding. In this embodiment, because micro-arc welding is performed, the heat is relatively difficult to apply to the whole and it cools easily; therefore, it is preferable to release the pressure immediately after welding.

[0052] As the welded portion W cools and the material solidifies and shrinks, the welded portion W of the valve stem 4 shrinks, causing the valve stem 4 to bend and deform in a direction that is concave towards the front end of the shaft portion 12 of the pin 10 and convex towards the head 11 of the pin 10. However, because the valve stem 4 is deformed by pressing it against the front end of the shaft portion 12 of the pin 10 during welding, i.e., by causing the front end of the shaft portion 12 of the pin 10 to convex and the head 11 of the pin 10 to bend and deform, this deformation is offset, and the valve stem 4 can maintain its straightness after welding.

[0053] The butterfly valve V manufactured in this way ensures smooth rotation of the valve stem 4 during use because the stem 4 maintains its straightness even after welding. Furthermore, when welding the front end of the shaft portion 12 of the pin 10, the welded portion W of the pin 10 on the second hole 7b side is approximately coplanar with the outer surface of the valve stem 4, resulting in virtually no protrusion from the stem 4 and no reduction in the fluid passage area. These effects enable stable control of the flow rate of the butterfly valve V. Therefore, the quality of the butterfly valve product can be improved.

[0054] The timing of releasing the pressure can be adjusted appropriately depending on the type of weld, the size of the valve stem or valve core, and the material of the valve stem or valve core. For example, if the type of weld is one that is easier to heat over a wide area, it is preferable to release the pressure after the weld has cooled down.

[0055] Figure 6 A second example of the fixture according to the embodiment is shown. Although this fixture 200 is constructed substantially the same as fixture 100, the difference lies in that, viewed from a cross-section orthogonal to the axis of the valve stem 4, the concave abutment portions 21a and 21b of the concave pressing body 20 and the convex abutment portion 31 of the convex pressing body 30 are each formed into a V-shape that contacts the outer periphery of the valve stem 4 at two points. The function and effect of fixture 200 are the same as those of fixture 100.

[0056] Figure 7 A third example of the clamp according to the embodiment is shown. Although the clamp 300 is constructed in a manner substantially the same as that of the clamp 100, the difference lies in that the concave abutment portions 21a and 21b of the concave pressing body 20 and the convex abutment portion 31 of the convex pressing body 30 are formed into flat shapes that make point contact with the outer periphery of the valve stem 4. Even with such flat shapes as the concave abutment portions 21a and 21b and the convex abutment portion 31, the clamp 300 can be expected to have the same function and effect as the clamp 100.

[0057] Figure 8A , Figure 8BA fourth example of the fixture according to the embodiment is shown. This fixture 400 has a different shape from the fixture 100, which is formed as a cylinder. The concave pressing body 20 of the fixture 400 is composed of a plate-shaped base 50 and a pair of rod-shaped protruding parts 51. The plate-shaped base 50 extends axially along the valve stem 4 and forms the same working hole 23 as described above. The pair of rod-shaped protruding parts 51 protrude from both ends of the base 50 and have concave abutment portions 21a (21b) at the front end. In addition, the convex pressing body 30 is formed as a rod with a convex abutment portion 31 at the front end. Viewed from a cross section orthogonal to the axis of the valve stem 4, the concave abutment portions 21a and 21b of the concave pressing body 20 and the convex abutment portion 31 of the convex pressing body 30 are respectively formed as arcs that make line contact or surface contact along the outer periphery of the valve stem 4. The function and effect are the same as those of the fixture 100.

[0058] In the fixture 400, viewed from a section orthogonal to the axis of the valve stem 4, any one of the concave abutment portions 21a and 21b of the concave pressing body 20 and the convex abutment portion 31 of the convex pressing body 30 can be formed into an arc shape that makes line contact or surface contact along the outer periphery of the valve stem 4, and any other one can be formed into a V-shape that makes two-point contact with the outer periphery of the valve stem 4. Appropriate modifications are also acceptable.

[0059] In the described embodiment, the convex pressing body 30 is fixed so that the concave pressing body 20 moves toward the convex pressing body 30, but this is not necessarily the case. Alternatively, the concave pressing body 20 may be fixed so that the convex pressing body 30 moves toward the concave pressing body 20. Or, both the concave pressing body 20 and the convex pressing body 30 may be moved toward each other; appropriate modifications are permissible.

[0060] In the described embodiment, the pin 10 of the butterfly valve V is shown as an example of a pin suitable for use with a screw, but it is not necessarily limited to this. It could also be a rivet-like pin without external threads formed on the shaft portion 12; appropriate modifications are acceptable. Furthermore, in the described embodiment, the butterfly valve V is shown as an example of a butterfly valve with two sets of through holes 7 on the valve stem side and 8 on the valve core side, but it is not necessarily limited to this. For example, a third set could be provided in the axial center portion of the valve stem 4 facing the fluid passage 2, resulting in a total of three sets, or even four or more sets of butterfly valves could be used. Moreover, in the described embodiment, the butterfly valve V is shown as an example of a butterfly valve of the type where the valve core 5 is inserted through the slit 6 formed in the valve stem 4, but it is not necessarily limited to this. For example, as... Figure 9 As shown, this method is also applicable in the type where the valve core 5 is embedded in a recess 60 formed on a side orthogonal to the axis of the valve stem 4 and fixed with a pin 10 made of screws, and appropriate modifications are also acceptable.

[0061] Furthermore, in the described embodiment, butterfly valve V is specifically designed for use in the throttle valve mechanism of an internal combustion engine (engine), but it is not necessarily limited to this. For example, it can certainly be applied to various other types of butterfly valves, such as throttle valves, power valves, swirl control valves, and tilt control valves. In short, those skilled in the art can readily make numerous modifications to these examples, i.e., embodiments, without substantially departing from the new teachings and effects of the invention, and all such modifications are included within the scope of the invention.

Claims

1. A method for manufacturing a butterfly valve, the butterfly valve comprising: a valve body having a fluid passage inside; a valve stem rotatably disposed within the valve body, spanning the fluid passage; and a valve core fixed to the valve stem within the fluid passage. The manufacturing method of the butterfly valve is characterized by the following: A valve stem-side through hole is formed in the valve stem using a pin having a head and a shaft. The valve stem-side through hole has an axis orthogonal to the axial direction of the valve stem, through which the shaft of the pin is inserted. A valve core-side through hole is formed in the valve core, corresponding to the valve stem-side through hole, through which the shaft of the pin is inserted. The valve stem-side through hole and the valve core-side through hole are connected to each other, and the valve core is attached to the valve stem. Then, the pin is inserted through the valve stem-side through hole and the valve core-side through hole from its shaft side. After that, when welding the front end of the pin's shaft to the surrounding area, the valve stem is pressed from the head side of the pin towards the front end of the pin's shaft to deform the valve stem. After welding is completed, the pressure on the valve stem is released.

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

3. The method for manufacturing the butterfly valve according to claim 2, characterized in that, The valve stem is deformed using a clamp. The clamp is configured to have: A concave pressing body is inserted into the fluid passage of the valve body, abutting against two concave pressing positions on both axial ends of the valve stem and facing the fluid passage, pressing the valve stem relative to each other from the front end of the pin's shaft towards the head of the pin; and A convex pressing body is inserted into the fluid passage of the valve body and abuts against the convex pressing position between the axial middle portion of the valve stem and the concave pressing position, pressing the valve stem relative to the front end of the axial portion of the pin from the head side of the pin.

4. The method for manufacturing the butterfly valve according to claim 3, characterized in that, The concave side pressing body is formed as a column that can be inserted into the fluid passage of the valve body. The concave side pressing body is configured to have: a concave side abutting portion, formed on both sides of one end of the concave side pressing body, abutting against the concave side pressing position of the valve stem; A recess, formed between the concave abutment portions, allows the valve stem to deform toward the front end of the pin's shaft; and a working hole, formed through to allow welding tools to pass through. The convex side pressing body is formed as a column that can be inserted into the fluid passage of the valve body. The convex side pressing body is configured to have a convex side abutment portion, which is formed at the center of one end of the convex side pressing body and abuts against the convex side pressing position of the valve stem.

5. The method for manufacturing the butterfly valve according to claim 4, characterized in that, The concave side abutting portion of the concave side pressing body is formed as an arc shape along the outer periphery of the valve stem or a V-shape that contacts two points on the outer periphery of the valve stem. The convex side abutting portion of the convex side pressing body is formed as an arc shape along the outer periphery of the valve stem or a V-shape that contacts the outer periphery of the valve stem at two points.

6. A clamp used in the manufacturing method of the butterfly valve according to any one of claims 1 to 5, characterized in that, It is composed of having: A concave-side pressing body presses the valve stem relative to the head side of the pin from the front end of the pin's shaft portion; and The convex pressing body presses the valve stem relative to the front end of the pin's shaft from the head side of the pin.

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