JP5642375B2 - Manufacturing method of throttle valve - Google Patents

Description

  The present invention relates to a method for manufacturing a throttle valve disposed in a throttle device that controls the amount of intake air into an internal combustion engine.

  Conventionally, in internal combustion engines such as automobiles, peripheral parts are made of resin for the purpose of weight reduction. As part of this, a resin is also used for a throttle valve (butterfly valve) that is rotatably disposed in the intake passage of the throttle device and opens and closes the intake passage. As a method of manufacturing such a resin throttle valve, there is, for example, Patent Document 1. In Patent Document 1, a resin throttle valve is manufactured by injection molding, and a metal throttle shaft is insert-molded at the center of a disk-shaped resin valve body. That is, the valve body has a shaft covering portion that covers the outer periphery of the throttle shaft serving as a shaft rotation center, and a semicircular plate-like semicircular portion that extends in the opposite direction across the shaft covering portion. . And in patent document 1, a throttle valve is injection-molded by injection-filling molten resin from the cavity for shaft coating parts through two injection gates which oppose in the direction orthogonal to the axial direction of a throttle shaft. Yes. Each injection gate directly faces the top of the shaft covering portion, and two opposing injection gates are coaxial. After the molten resin is cured, the remaining gate trace protrusion is removed.

  On the other hand, Patent Document 2 discloses an injection molding method for a molded product that is not a throttle valve but is plated after injection molding. Patent Document 2 is a method for manufacturing a shutter button or the like of an electronic device such as a digital camera. A pedestal that protrudes from a surface of a main body of a molded product is provided, and an injection gate is provided in the pedestal portion. As a result, even if the gate trace protrusion is removed by folding after the molten resin is cured, it is said that the plating can be peeled off only at the pedestal portion.

  Similarly, there is Patent Document 3 as an injection molding method for precision plastic products, not for a throttle valve. In Patent Document 3, the shape of the injection gate is set to a triangular shape, and the gate trace protrusion is cut from a portion having a small width (on the top side).

Japanese Patent Laid-Open No. 2005-140061 JP 2009-34970 A JP-A-1-234220

  In Patent Document 1, since the injection gate directly faces the valve body, if the gate trace protrusion is removed after the molten resin is cured, the peripheral portion of the gate trace protrusion and the peripheral part thereof are also scraped together. So-called eating will occur. On the other hand, in patent document 2, the base is provided between the injection gate and the molded product. In Patent Document 2, attention is paid to the peeling of the plating when the gate trace protrusion is folded, and no particular consideration is given to eating. However, provision of a pedestal may be effective in preventing eating of the molded product body. . However, in Patent Document 2, the shape of the injection gate is not particularly taken into consideration, and in a conventional circular gate, stress is dispersed when the gate trace protrusion is folded, so that eating occurs in a wide range. there's a possibility that. In this case, there is a possibility that the eating will extend not only to the pedestal but also to the molded product main body. On the other hand, in Patent Document 3, since the shape of the injection gate is triangular, stress concentration may occur if the gate trace protrusion is folded. However, Patent Document 3 presupposes that the gate trace protrusion is cut only, and does not use the stress concentration when the gate trace protrusion is folded. In addition, since the pedestal is not provided, it is inevitable that if the gate trace protrusion is to be broken, the molded product body is eroded.

  In Patent Document 1, the injection gate is provided in the shaft covering portion, and the shaft covering portion is the thinnest portion due to the presence of the throttle shaft and the thickness limitation of the valve body. Therefore, the flow resistance of the injection-filled molten resin in the shaft covering portion is large. Moreover, since the injection gate is located at the top of the shaft cover, the molten resin injected from the injection gate flows so as to branch equally in both directions after colliding with the throttle valve. Is also big. In this case, since there is a limit to keeping the pressure in the cavity at the time of injection molding high, the resin density of the throttle valve which is an injection molded product also decreases. When the density of the throttle valve is low, the degree of shrinkage accompanying the hardening of the molten resin increases, and the dimensional accuracy deteriorates. Since the throttle valve controls the intake air amount by the size of the gap between the disc-shaped valve body and the throttle body, the deterioration of the dimensional accuracy of the throttle valve directly leads to poor control of the intake air amount.

  Here, in Patent Document 2, a pedestal is provided between the injection gate and the molded product body. However, Patent Document 2 is a method for manufacturing a shutter button of a digital camera, and includes flow resistance and pressure during injection molding. This is not intended to improve loss, and cannot be directly applied to a method of manufacturing a throttle valve that is manufactured by inserting a throttle shaft and filling and forming resin around it. On the other hand, as a means for solving such a problem, it is conceivable to increase the flow resistance and holding pressure of the molten resin by increasing the cavity capacity in Patent Document 1 and increase the density of the throttle valve. It is necessary to increase the size of the mold, which increases the cost and is not realistic.

  Moreover, the side surface of the base of patent document 2 is a perpendicular | vertical surface with respect to the main-body part. Here, when the pedestal is to be cut with the rotary cutting tool after the molten resin is cured, a shearing force acts on the pedestal in the tangential direction of the rotary tool. However, since the side surface of the pedestal in Patent Document 2 is a vertical surface with respect to the main body, the thickness in the direction in which the shearing force acts is small. Therefore, the durability against the shearing force accompanying the rotary cutting is not sufficient, and the pedestal may be lost. If the defect remains in the pedestal portion, no major problem will occur. However, it is assumed that the defect extends beyond the pedestal and reaches the main body (a valve body in the case of a throttle valve). As described above, if the valve body is damaged by cutting the pedestal with the rotary cutting tool, the intake air amount may be poorly controlled.

  Accordingly, the present invention solves the above-described problem, and a throttle valve manufacturing method capable of manufacturing a throttle valve with high resin density and good dimensional accuracy that can avoid the loss of a valve body when removing gate trace protrusions. The purpose is to provide.

  The present invention is rotatably disposed in a throttle device that controls the amount of intake air to an internal combustion engine (engine), and extends in a direction opposite to the cylindrical shaft covering portion with the shaft covering portion interposed therebetween. The present invention relates to a throttle valve manufacturing method in which a throttle shaft serving as a rotation center is insert-molded into a resin valve body having a semicircular disk-shaped semicircular disk portion. That is, the throttle valve is injection molded. At this time, a mold cavity is formed so that a pedestal is formed on the surface of the shaft covering portion, and an injection gate for injecting and filling molten resin is communicated with the pedestal cavity. The injection gate has a cross-sectional shape having at least one corner. The term “corner” as used herein means a non-linear shape, and includes a sharp corner and a gently curved corner.

  According to this, the gate trace protrusion remains through the pedestal on the surface of the shaft covering portion immediately after the injection molding. Therefore, it is necessary to remove the gate trace protrusion as post-processing. Therefore, for example, when the gate trace protrusion is removed by folding, a problem of so-called eating out that the peripheral portion of the gate trace protrusion is simultaneously stripped off becomes a problem. However, in the present invention, since the gate mark protrusion is formed on the pedestal, it is possible to effectively avoid eating away from the pedestal portion and damaging the valve body itself. In addition, the gate trace protrusion has a cross-sectional shape having at least one corner. Therefore, stress concentration occurs in the corner portion, so that the range of eating and eating can be suppressed small. In this sense, the corner portion can also be referred to as a stress concentration portion. Thereby, the occurrence of eating can be stopped only at the pedestal portion, and the breakage of the valve body can be surely prevented. In this way, if the gate trace protrusion can be removed without problems, it is simpler than the case where the gate trace protrusion is excised, and the productivity is improved.

  The cross-sectional area of the injection gate may be equal to the cross-sectional area of the runner that supplies the molten resin to the injection gate, but is preferably smaller than the cross-sectional area of the runner. In other words, the injection gate is thinner than the runner. That the cross-sectional area of the injection gate is smaller than the cross-sectional area of the runner means that the tip of the runner is tapered. According to this, the stress or labor when removing the gate trace protrusion is reduced, and the gate trace protrusion is easily removed. Moreover, the occurrence range of eating can be suppressed smaller.

  The cross-sectional shape of the injection gate is not particularly limited as long as it has a shape having at least one corner, but for example, a bell shape is preferable. The bell shape is a shape in which one surface of a quadrangle is an arc surface. If the corner is an acute angle, the stress may be concentrated more than necessary, and the eating may increase, but if the stress is concentrated on the bell-shaped curved corner (top), the stress will be concentrated more than necessary. You can avoid that. Moreover, if it is a bell shape, compared with the shape which has an acute corner | angular part, the fluidity | liquidity of molten resin is good, and it is advantageous also in terms of flow resistance or pressure loss.

  The injection gate and the pedestal may be provided at only one place, but are preferably provided at two places facing each other across the throttle shaft from a direction orthogonal to the axial direction of the throttle shaft. At this time, the pedestal and the injection gate are allowed to face the top of the shaft covering portion. In this case, both injection gates are opposite to each other in the direction in which the semicircular disk portion extends, with the center line passing through the axial center of the throttle shaft and perpendicular to the extending direction of the semicircular disk portion. It is preferably provided at a position shifted (offset).

  When the molten resin is injected and filled from one injection gate to the shaft covering portion, it must be filled to the opposite side around the inserted throttle shaft, and the pressure loss increases. On the other hand, if the molten resin is injected and filled from two locations facing each other across the throttle shaft, it is not necessary to fill up to the opposite side of the throttle shaft, so the pressure loss can be reduced. At this time, since the injection gate faces the top of the shaft covering portion, the resin can flow in both directions in which the semicircular plate portion extends, and the shaft covering portion can be reliably formed. In addition, when the injection gate is displaced from the center line, most of the molten resin flows in the position displacement direction in the shaft covering portion, and the flow amount to the opposite side to the position displacement direction is reduced. As a result, the flow resistance in the direction of displacement is reduced, and the molten resin injected from the injection gate is also reduced from colliding with the throttle shaft, so that the pressure loss is also reduced. As a result, the holding pressure and holding time in the cavity can be increased as compared with the prior art. Thus, the resin density of the valve body can be improved, the degree of shrinkage due to curing is small, and the dimensional accuracy is also improved. At this time, the flow resistance or the like in one direction can only be reduced by one injection gate, but the flow resistance can be reduced in both directions by shifting the two injection gates to the opposite sides. The resin density can be reliably increased throughout the body.

  At this time, it is preferable that each of the pedestals is formed in a direction in which the injection gate is displaced from the top of the shaft covering portion. According to this, since the flow path width directly under the injection gate in the direction in which the molten resin mainly flows increases due to the presence of the pedestal, the flow resistance can be further reduced. Moreover, since there is a difference between the channel width in the direction in which the pedestal extends and the channel width to the opposite side, the flow rate to the opposite side can be effectively suppressed.

  The cross-sectional shape of the pedestal does not necessarily match the cross-sectional shape of the injection gate, but the cross-sectional shape of the pedestal and the cross-sectional shape of the injection gate are preferably the same. Thereby, the molten resin injected from the injection gate can smoothly flow through the pedestal, and flow resistance and pressure loss can be further reduced. The same shape includes a similar shape.

  In addition, both the semi-disc portions of the valve body can sufficiently obtain the above-described effects even if they are coaxial with each other (same plane) as in the conventional general throttle valve. The part is also preferably formed in a state of being shifted (offset) to opposite sides across the center line in the extending direction of the semicircular disk part passing through the axial center of the throttle shaft. In this case, the semicircular disk portions and the injection gates are displaced in directions close to each other. According to this, since the flow path width in the direction in which the molten resin mainly flows directly under the injection gate becomes larger, the flow resistance and the pressure loss can be further reduced.

  In addition, the throttle shaft can obtain the above-mentioned effects even when the throttle shaft has a uniform diameter in the entire axial direction as in a general throttle shaft, but the portion of the throttle shaft facing the injection gate is sufficient. It is preferable to make the shaft diameter smaller than other parts. According to this, since the thickness of the shaft covering portion at the portion facing the injection gate is increased, the flow path width immediately below the injection gate is further increased, and the flow resistance and pressure loss can be further reduced. Moreover, as the thickness of the shaft covering portion increases, the strength at that portion also increases. Thereby, since the plate | board thickness of a semicircular disk part can be made thin, in the fully open state of a throttle valve, the reduction | decrease of the flow-path opening area of intake air can be suppressed.

  As described above, according to the manufacturing method of the present invention, the above-described effects can be obtained. Therefore, after the molten resin is cured, it is preferable to remove the gate trace protrusion by folding it. The removal by folding the gate trace protrusion is more efficient than the excision.

  Moreover, after making the side surface of the said base into the slope which spreads toward the shaft coating | coated part from the said injection gate side, the said base can also be cut with a rotary cutting tool after hardening of molten resin. The pedestal may be cut as a finishing process after the gate trace protrusion is folded, or the pedestal may be cut including the gate trace protrusion. If the pedestal is cut, the amount of protrusion of the pedestal becomes small and the cutting surface becomes flat, so that the flow of the intake air is hardly hindered. Also, when cutting with a rotary cutting tool, shear stress acts on the pedestal in the tangential direction of the rotary cutting tool, but if the side surface of the pedestal is a diverging slope, the length of the direction in which the shearing force acts is increased. The thickness (thickness) is increased, and it is possible to effectively prevent the base from being lost due to cutting.

  Note that the shape of the injection gate and the pedestal is not particularly limited as long as it is essential to cut the pedestal with a rotary cutting tool, and attention is paid only to prevention of the pedestal breakage. That is, the injection gate and the pedestal do not necessarily have a shape having a corner, and may be, for example, a circle. As an invention in this case, the throttle device for controlling the amount of intake air to the internal combustion engine is pivotally disposed and extends in a direction opposite to the cylindrical shaft covering portion with the shaft covering portion interposed therebetween. A method of manufacturing a throttle valve, which is obtained by insert-molding a throttle shaft serving as a rotation center in a resin valve body having a semi-disk-shaped semi-disk portion, and a base is provided on the surface of the shaft covering portion. A mold cavity is formed so that an injection gate for injecting and filling molten resin is communicated with the base cavity, and the side surface of the base extends from the injection gate side toward the shaft covering portion. It is also possible to propose a method for manufacturing a throttle valve, which has a slope that spreads toward the end, and the pedestal is cut with a rotary cutting tool after the molten resin is cured.

  According to the present invention, even if the gate trace protrusion remaining immediately after the injection molding is removed by folding, the range in which eating is caused by stress concentration based on the shape of the gate trace protrusion is narrowed. Therefore, even if eating occurs, the range remains only in the pedestal portion, so that the valve body can be prevented from being lost. In addition, since the flow resistance and pressure loss during injection filling of the molten resin are small, the holding pressure in the cavity can be increased, and the resin density of the valve body can be improved. At the same time, the time during which the internal pressure can be maintained at a high level also increases. Thus, a throttle valve having a high resin density and good dimensional accuracy can be manufactured. In addition, if the side surface of the pedestal is a slope that is widened toward the end, even if the pedestal is cut with a rotary cutting tool, the pedestal can be effectively prevented from being lost.

It is a perspective view of a throttle device. It is a perspective view of a throttle valve. It is sectional drawing of a metal mold | die. It is sectional drawing of the metal mold | die which looked at the injection gate from the front. It is a schematic diagram which shows the flow of molten resin. It is a side view of a throttle valve in the state where a gate mark projection remains. It is a schematic diagram in the case of cutting a base. 6 is a schematic diagram illustrating a flow of a molten resin in Example 2. FIG. 6 is a perspective view of a throttle valve according to Embodiment 3. FIG. 10 is an enlarged cross-sectional view of a main part of a mold in Example 4. It is a perspective view of the throttle valve of Example 4.

  Hereinafter, a plurality of typical embodiments of the present invention will be described. However, the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

Example 1
As shown in FIG. 1, the throttle valve 10 manufactured by the manufacturing method of the present invention is disposed on the throttle device 1 so as to be pivotable. The throttle device 1 is a device that is mounted on a vehicle such as an automobile and controls the amount of intake air into each cylinder of an internal combustion engine (engine) not shown. The throttle body 2 of the throttle device 1 is made of resin and has a cylindrical bore portion 3, a motor housing portion 4, and a gear box portion 5. The internal space of the bore portion 3 serves as an intake passage through which intake air flows, and the throttle valve 10 is disposed in the bore portion 3 so as to be rotatable forward and backward. Both ends of the shaft of the throttle valve 10 are supported by a bearing portion 6 provided at a position facing the bore portion 3. The throttle valve 10 is controlled to rotate according to the amount of depression of an accelerator pedal (not shown). As the throttle valve 10 rotates, the clearance (clearance) dimension between the outer peripheral edge of the throttle valve 10 and the inner wall surface of the bore 3 changes, and is introduced into the internal combustion engine by the size change of the clearance. The intake air intake amount is controlled. The state shown in FIG. 1 is a fully opened state of the throttle valve 10. On the other hand, when the throttle valve 10 is at an angle substantially perpendicular to the flow direction of the intake air (a substantially horizontal angle with respect to the direction shown in FIG. 1), the intake passage is fully closed. A motor (not shown) which is a driving means for rotating the throttle valve 10 is disposed inside the motor housing portion 4. A gear mechanism (not shown) that transmits the driving force of the motor to the throttle valve 10 is disposed inside the gear box portion 5.

  As shown in FIG. 2, the throttle valve 10 includes a substantially disc-shaped resin valve body 11 and a rod-shaped metal throttle shaft 12 serving as a shaft rotation center. The throttle shaft 12 penetrates in the radial direction in the plane of the disk at the central portion of the valve body 11, and both ends thereof are supported by bearing portions 6 provided in the bore portion 3 of the throttle body 2. The valve body 11 is formed by integrating a cylindrical shaft covering portion 13 that covers the throttle shaft 12 and semicircular plate portions 14 and 14 that extend in opposite directions across the shaft covering portion 13. Have. Bell-shaped pedestals 15 and 15 are integrally formed at the central part in the axial direction of the shaft covering portion 13 at both tops of the arc surface of the shaft covering portion 13 so as to protrude from the surface of the shaft covering portion 13. ing. Both pedestals 15 and 15 are formed toward the opposite sides in the extending direction of the semicircular disk portions 14 and 14 (vertical direction in the drawing standard). Although not shown, a plurality of reinforcing ribs are integrally arranged at equal intervals on the surfaces of the semicircular disk portions 14 and 14 in a direction orthogonal to the axial direction of the throttle shaft 12. .

  The throttle body 2 and the valve body 11 are injection-molded with a thermoplastic resin having good heat resistance such as polyphenylene sulfide (PPS), polyamide resin (PA), polypropylene (PP), polyetherimide (PEI).

  A method for manufacturing the throttle valve 10 will be described with reference to FIGS. Basically, as shown in FIG. 3, the valve body 11 is injection-molded with the throttle shaft 12 inserted into a molding die 40 having a cavity of a predetermined shape. The valve molding die 40 includes a stationary die 41, a movable die 42, slide cores 43 and 43, and the like, and a cavity is defined in a state where each of them is clamped. Specifically, each of the fixed mold 41 and the movable mold 42 includes a cavity 13c for the shaft covering portion 13 (hereinafter, simply referred to as the shaft covering portion 13c with respect to the description of the mold), and a semicircle continuous therewith. A cavity 14c for the plate portion 14 (hereinafter simply referred to as a semi-disc portion 14c with respect to the description of the mold) is formed. Therefore, when the fixed mold 41 and the movable mold 42 are abutted and clamped, they pass through the axial center of the throttle shaft 12 (axial center of the shaft covering portion 13c) and the extending direction of the semicircular plate portion 14c (this embodiment). A center line L1 in a direction orthogonal to the vertical direction in the example (horizontal direction in the present embodiment) coincides with the contact surface S between the fixed mold 41 and the movable mold 42. Also, cavities 15c for the base 15 (hereinafter simply referred to as the base 15c for the description of the mold) are formed on both tops of the shaft covering portion 13c.

  The fixed mold 41 is provided with two runners 44 and 44 serving as a flow path for the molten resin with the semicircular plate portion 14c interposed therebetween, and an injection gate 45 opened at the tip thereof is communicated with the base 15c. Then, it faces the top of the arc surface of the shaft covering portion 13c. That is, the injection gate 45 is provided at two locations so as to face each other across the throttle shaft 12 from a direction orthogonal to the axial direction of the throttle shaft 12 (shaft covering portion 13c) (left and right direction in this embodiment). Both injection gates 45 and 45 are also orthogonal to the extending direction of the semi-disc portion 14c. The tip of the runner 44 is tapered, and the cross-sectional area of the injection gate 45 is smaller than the cross-sectional area of the runner 44. Reference numeral 3 c is a cavity for forming the bore portion 3 of the throttle body 2. The cavity 3c for the bore 3 is filled with molten resin from another injection gate (not shown).

  Of the two injection gates 45 and 45 and the pedestals 15c and 15c, one (right side in this embodiment) the injection gate 45 and pedestal 15c are formed in the fixed mold 41, and the other (left side in this embodiment). The injection gate 45 and the pedestal 15 c are formed on the movable mold 42. Thereby, one injection gate 45 and the base 15c are directly under the contact surface S of the fixed mold 41 and the movable mold 42, and the other injection gate 45 and the base 15c are the fixed mold 41 and the movable mold. 42 is just above the contact surface S with 42. Accordingly, the injection gates 45 and 45 and the pedestals 15c and 15c have a contact surface S between the fixed mold 41 and the movable mold 42, that is, a center line L1 passing through the axial center of the throttle shaft 12 (shaft covering portion 13c). It is in a relationship of being offset (offset) to the opposite sides to each other in the vertical direction in which the semicircular disk portion 14c extends. Both pedestals 15c and 15c are formed from the top of the shaft covering portion 13c, that is, from the center line L1 toward the direction (position shift direction) in which the injection gate 45 is formed. As shown in FIG. 4, the cross-sectional shape of the injection gate 45 is a bell shape, and the cross-sectional shape of the pedestal 15 c is also formed in the same bell shape as the cross-sectional shape of the injection gate 45. Precisely, the cross-sectional shape of the injection gate 45 is similar to the cross-sectional shape of the pedestal 15c. Further, the side surface of the pedestal 15c is a slope that expands from the injection gate 45 side toward the shaft covering portion 13c.

  Next, injection molding will be described. First, the throttle shaft 12 is inserted into the molding die 40 and fixed so as to be disposed at the central portion of the shaft covering portion 13c. Then, the fixed die 41, the movable die 42, etc. are clamped to form the cavity. Define. The molten resin supplied through the runner 44 is injected and filled into the cavity via the injection gate 45 facing the shaft covering portion 13c. Then, as shown in FIG. 5, the molten resin flows so as to branch in the shaft covering portion 13c. At this time, the presence of the pedestal 15c and the injection gate 45 and the pedestal 15c are displaced with respect to the center line L1, thereby causing a difference in the resin flow rate in the shaft covering portion 13c. Specifically, the molten resin injected from one (right side in this embodiment) injection gate 45 that is displaced to one side (downward in this embodiment) of the center line L1 is slightly below the throttle shaft 12. The flow direction becomes downward due to the collision, and the flow passage width is increased due to the presence of the pedestal 15c, so that the shaft flows mainly downward in the shaft covering portion 13c. Slightly. On the other hand, the molten resin injected from the injection gate 45 on the other side (left side in this embodiment) shifted to the other side of the center line L1 (upper side in this embodiment) collides with the upper part of the throttle shaft 12 slightly. The flow direction is upward and the flow path width is increased due to the presence of the pedestal 15c, so that the fluid flows mainly upward in the shaft covering portion 13c, and the downward flow amount is small. .

  As a result, one (right side in this embodiment) semicircular disk portion 14c is filled with the molten resin injected from one (right side) injection gate 45, and the other (upper side in this embodiment) half-disc. The disc portion 14c is filled with the molten resin injected from the other (left side) injection gate 45. In this case, the flow resistance and pressure loss are lower than when the molten resin injected from the injection gate 45 flows substantially evenly in the vertical direction and flows. Note that the injection gate 45 and the base 15c having the same bell shape also contribute to the flow resistance and prevention of pressure loss reduction. As a result, the inside of the cavity can be held at a higher pressure than before, and the pressure can be held at a higher level for a longer time, so that the resin density is improved and the dimensional accuracy of the valve body 11 is improved.

  When the molten resin is cured, the mold is removed to obtain the throttle valve 10 in which the throttle shaft 12 is inserted. However, the gate trace protrusion 20 remains on the pedestal 15 as shown in FIG. 6 just by removing the die, and cannot be used as a product as it is. Therefore, the gate trace protrusion 20 is removed by folding. At this time, there is a case in which so-called eating is generated in which the gate trace protrusion 20 and its peripheral part are also scraped together. However, in this embodiment, since the gate trace protrusion 20 has a bell shape, stress concentration occurs at the top of the bell and the eating range is narrowed. Moreover, since the injection gate 45 has a smaller cross-sectional area than the runner 44, the stress itself is also small. In addition, the gate mark protrusion 20 is formed on the pedestal 15. Therefore, even if eating occurs, only the pedestal 15 part is lost, and the loss of the valve body 11 itself is reliably prevented.

  If the gate trace protrusion 20 can be removed, the throttle valve 10 can be incorporated into the throttle device 1 as it is. However, since the protrusion amount of the base 15 is large only by folding the gate trace protrusion 20, and the upper surface (fracture surface) thereof is not flat, the flow of the intake air may be hindered as it is. Therefore, it is preferable to cut the base 15 as a finishing process. For cutting the pedestal 15, it is preferable to use a rotary cutting tool that cuts the object by sliding while rotating. Typically, a known end mill 21 can be used as shown in FIG. At this time, a shearing force F acts on the pedestal 15 in the tangential direction of the end mill 21 due to the rotational cutting of the end mill 21, and the pedestal 15 may be chipped by the shearing force F. In the worst case, the pedestal 15 may be lost to the valve body 11. However, in this embodiment, the side surface of the pedestal 15 is a slope that spreads toward the end, so that the thickness in the direction in which the shearing force F acts increases, and the pedestal 15 is unlikely to be lost.

(Example 2)
In the first embodiment, the two semicircular disk portions 14 and 14 are formed coaxially (in the same plane). However, as in the second embodiment shown in FIG. The plate portions 14 and 14 are formed in a state of being shifted to the opposite sides with respect to the center line L2 in the extending direction (vertical direction in this embodiment) of the semicircular plate portion 14 passing through the axial center of the throttle shaft 12. It is preferable to do. In this case, the semicircular disk portions 14 and 14 are displaced in the direction in which the bases 15 and 15 are formed, respectively. That is, in the case of the cavity of the molding die 40, the semicircular disk portions 14c and 14c and the injection gates 45 and 45 are displaced in directions close to each other. According to this, the flow path width of the shaft covering portion 13c at the portion facing the injection gate 45 becomes larger than that of the first embodiment, and the flow resistance and pressure loss can be further reduced. The other parts are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

Example 3
In the first embodiment, the throttle shaft 12 having a uniform diameter is inserted over both axial ends. However, as in the third embodiment shown in FIG. 9, the axial center portion of the throttle shaft 12, that is, the injection gate. It is also preferable to insert the throttle shaft 12 having the small-diameter portion 12a having a smaller diameter than other portions at the portion where the 45 faces. According to this, the flow path width of the shaft covering portion 13c in the small diameter portion 12a facing the injection gate 45 becomes larger than that in the first embodiment, and the flow resistance and pressure loss can be further reduced. The other parts are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

Example 4
In addition, the first embodiment is a mode in which the resin density of the valve body 11 is simultaneously improved while assuming that the gate trace protrusion 20 is folded. If so, the shape of the injection gate and the pedestal is not particularly limited as long as the side surface of the pedestal is an inclined surface extending from the injection gate side toward the shaft covering portion. For example, the conventional technology such as Patent Document 1 may be provided only with a pedestal having a diverging slope. Example 4 is an example of such a form.

  In the fourth embodiment, as shown in FIG. 11, circular pedestals 16 and 16 are formed on the surface of the shaft covering portion 13. Specifically, as shown in FIG. 10, the injection gates 45 and 45 communicating with the top of the shaft covering portion 13c from the opposing position orthogonal to the axial direction of the shaft covering portion 13c via the base 16 are coaxial (center line L1). It is above. The cross-sectional shapes of both injection gates 45 are also circular. Both pedestals 16 and 16 are also formed with the center line L1 as the center, but the side surfaces of the pedestals 16 and 16 are slopes that widen toward the shaft covering portion 13c from the injection gate 45 side. In addition, the bases 16 and 16 are cut with a rotary cutting tool after the molten resin is cured. Also in this case, since the side surfaces of the pedestals 16 and 16 are slopes that widen toward the end, the thickness in the direction in which the shearing force F acts is increased as in FIG. 7 of the first embodiment.・ 16 is hard to lose. The other parts are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

(Other variations)
In each of the above embodiments, the throttle valve 10 and the throttle body 2 are separately molded by different injection gates, but one runner 44 is communicated with the cavity for the valve body 11 and the cavity for the throttle body 2. At the same time, injection molding can be performed. The pedestal may be cut by the rotary cutting tool including the gate trace protrusions without breaking the gate trace protrusions. As the rotary cutting tool, a grinding tool such as a grindstone can be used in addition to the end mill.

  Moreover, each said Example is illustrated as a preferable form. Compared with these examples, the degree of the effect obtained is inferior, but the following forms are also possible. The cross-sectional shape of the injection gate is not limited to a bell shape, as long as it is a non-circular shape having at least one corner that becomes a stress concentration portion, and various shapes such as polygons such as triangles and quadrangles, fan shapes, oval shapes, etc. Can be. The cross-sectional area of the injection gate may be the same as the cross-sectional area of the runner. As long as at least the injection gates are displaced from each other, the pedestal may not be displaced at the same time. The cross-sectional shape of the injection gate and the cross-sectional shape of the pedestal may be different.

DESCRIPTION OF SYMBOLS 1 Throttle device 2 Throttle body 3 Bore part 6 Bearing part 10 Throttle valve 11 Valve body 12 Throttle shaft 12a Small diameter part 13 Shaft covering part 14 Semicircular disk part 15/16 Base 20 Gate trace protrusion 21 End mill 41 Fixed mold 42 Movable metal Mold 44 Runner 45 Injection gate F Shear force L1 Center line L2 in the direction orthogonal to the extending direction of the valve body Center line S in the extending direction of the valve body Contact surface

Claims (7)

A throttle device that controls the amount of intake air to the internal combustion engine is pivotally disposed, and has a cylindrical shaft covering portion and a semicircular plate-like half extending in the opposite direction across the shaft covering portion. A throttle valve manufacturing method in which a throttle shaft serving as a rotation center is insert-molded into a resin valve body having a disk portion,
A mold cavity is formed so that a pedestal is formed on the surface of the shaft covering portion, and an injection gate for injecting and filling molten resin is communicated with the cavities for the pedestal,
The injection gate has a bell-shaped cross section,
The injection gate and the pedestal are provided at two locations facing each other across the throttle shaft from a direction perpendicular to the axial direction of the throttle shaft, and both the injection gate and the pedestal face the top of the shaft covering portion,
The injection gates are positioned opposite to each other in a direction in which the semicircular plate portion extends, with a center line passing through the axial center of the throttle shaft and perpendicular to the extending direction of the semicircular disc portion. It is provided at a shifted position,
The both pedestals are formed in a direction in which the injection gate is displaced from the top of the shaft covering portion, respectively .   2. The method of manufacturing a throttle valve according to claim 1, wherein a cross-sectional area of the injection gate is smaller than a cross-sectional area of a runner that supplies molten resin to the injection gate.   The method for manufacturing a throttle valve according to claim 1 or 2, wherein a cross-sectional shape of the pedestal is the same shape as a cross-sectional shape of the injection gate. Both semi-disc parts of the valve body are formed in a state of being shifted to opposite sides with respect to the center line in the extending direction of the semi-disc part passing through the axial center of the throttle shaft,
The method for manufacturing a throttle valve according to any one of claims 1 to 3, wherein each of the semicircular disk portions and each of the injection gates are displaced from each other in directions close to each other.   The throttle valve manufacturing method according to any one of claims 1 to 4, wherein the portion of the throttle shaft facing the injection gate has a smaller shaft diameter than other portions.   6. The method for manufacturing a throttle valve according to claim 1, wherein after the molten resin is cured, the gate trace protrusion is removed by folding. The side surface of the pedestal is a slope that extends from the injection gate side toward the shaft covering portion,
The method for manufacturing a throttle valve according to any one of claims 1 to 6, wherein the base is cut with a rotary cutting tool after the molten resin is cured.

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