JP4109276B2 - Joint boot manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a joint boot.

  One of the constant velocity joints provided on a drive shaft of an automobile is a tripod type constant velocity joint that can change its position in the axial direction and transmit rotational force. As shown in FIGS. 10 and 11, the constant velocity joint includes a tripod 33 configured by projecting three trunnions 31 having rollers 32 on one of the input side and output side shafts 3 in a direction perpendicular to the axis, The outer case 1 is provided at the end of the other shaft 40. The outer case 1 has three grooves 34 on which the rollers 32 roll on the inner periphery thereof in a distributed manner in the circumferential direction.

  A joint boot is attached to the constant velocity joint in order to prevent intrusion of dust and foreign matter and to retain grease. The joint boot is composed of a cylindrical large-diameter side attachment portion 2 attached to the outer case 1, a small-diameter side attachment portion 4 attached to the shaft 3, and a bellows portion 5 connecting them.

  In order to reduce the weight, the outer case 1 is provided with a plurality of concave portions 8 that are radially inwardly distributed in the circumferential direction. For this reason, the inner side of the large-diameter side mounting portion 2 of the joint boot is provided. The peripheral portion is provided with a plurality of convex portions 7 projecting radially inwardly in a circumferential direction. On the other hand, the outer peripheral surface of the large-diameter side attachment portion 2 is formed in a circular cross section for tightening by the ring-shaped band 9.

  Conventionally, a resin joint boot is generally manufactured by molding a bellows portion and a large diameter side mounting portion after molding a small diameter side mounting portion by injection molding (see, for example, Patent Document 1). However, the joint boot having the large-diameter side mounting portion 2 having the outer peripheral surface and the inner peripheral surface having different shapes as described above cannot be manufactured by general injection blow molding. This is because the thickness in the circumferential direction is uniform or almost uniform in blow molding, and therefore, if the large-diameter side attachment portion is blow-molded, the convex portion 7 of the inner peripheral portion cannot be molded.

  Therefore, in Patent Document 2, a drawing device having a cavity for forming a small-diameter side attachment portion is brought into contact with the outlet gap of the nozzle base, and the molten resin is injected into the cavity from the outlet gap, thereby attaching the small-diameter side. After forming the part, the molten resin is extruded through the outlet gap and the drawing device is separated to form a cylindrical parison, and then the uppermost part of the nozzle base is replaced with a blow mold to blow the bellows part. There has been proposed a method of manufacturing a tripart type joint boot as described above by molding and injection-molding the large-diameter side attachment portion with a lower nozzle cap.

  However, in the method described in Patent Document 2, the cavity for molding the large-diameter side mounting portion which has the highest dimensional accuracy and is difficult to be molded because the dimension is the largest is the small-diameter side mounting portion. It is used as a flow path for molten resin during the injection molding and extrusion of the parison. Therefore, it is necessary to keep this cavity part at a high temperature when using it as a flow path for molten resin, and to cool it at the time of injection molding, and there is a problem that temperature control is complicated and it is difficult to ensure high dimensional accuracy. .

  On the other hand, in Patent Document 3, a parison having a large-diameter side attachment portion, a small-diameter side attachment portion, and a hollow blow portion corresponding to the bellows portion is injection-molded, and after cooling, the molded parison is used as an injection mold. A method is described in which the bellows part is formed by taking it out together with the core mold, mounting it on a blow mold, and blowing air into the blow part from the core mold.

However, in this patent document 3, the core mold at the time of injection molding is used as it is as a support for supporting the inner peripheral side of the parison at the time of blow molding, and in that case, in order to inject gas into the core mold It is necessary to incorporate this mechanism, and the structure of the core type becomes complicated. Therefore, it is desirable to use a separate member from the core mold at the time of injection molding as the support at the time of blow molding. In that case, it is possible to prevent the gas injected inside the parison from leaking to the outside. However, it is important to accurately blow-mold the bellows. In particular, in the triport type joint boot as described above, since the large-diameter side mounting portion has an irregular shape in the circumferential direction, it is difficult to prevent gas leakage in the large-diameter side mounting portion.
JP-A-6-234150 JP 2002-361715 A JP 2003-222155 A

  The present invention has been made in view of the above points, and a method for manufacturing a joint boot capable of accurately manufacturing a joint boot having a large-diameter side mounting portion having an outer peripheral surface and an inner peripheral surface having different shapes. The purpose is to provide.

The method according to the present invention includes a cylindrical large-diameter side mounting portion in which a plurality of convex portions protruding from the inner peripheral portion are fitted and attached to the concave portion of the outer case, and a cylindrical small-diameter side mounting portion that is attached to the shaft. And a joint boot comprising a bellows part integrally connecting the two, wherein a first part forming a product shape of the large-diameter side attachment part and a product shape of the small-diameter side attachment part are formed. A parison molding step of injection-molding a parison with a thermoplastic resin, and a first portion, a second portion, and a third portion of the parison. A heating step of heating the third part to a set temperature with a heating device, and covering the outer peripheral side with a blow outer mold in a state where the inner peripheral side of the heated parison is supported by a support, and the third part The third part by injecting gas into the inside Against the low outer die; and a blowing step of forming the bellows portion. In the parison molding step, a sealing tubular portion is integrally extended from the opening end surface of the first portion to the parison, and in the heating step, the sealing tubular portion is heated together with the third portion. In the blowing step, by clamping the blow outer mold against the support supporting the parison, the sealing cylindrical portion is crushed between the support and the blow outer mold , At that time, in the clamping portion between the support body and the blow outer mold for sandwiching the cylindrical portion for sealing, the protrusion extending in the circumferential direction provided in the support body or the blow outer mold is axially moved by the crushing. outer side plastically deformed so bite into the sealing tubular portion extending in, thereby to perform the blow molding by injecting the gas while sealing the gap between the blow outer die and the support member A.

  According to this means, the large-diameter side mounting portion and the small-diameter side mounting portion are formed into a final product shape with high dimensional accuracy during parison injection molding, and the bellows portion is finally formed by subsequent blow molding. Therefore, even if the large-diameter side mounting portion and the small-diameter side mounting portion have different shapes, it can be accurately molded.

  Further, at the time of parison injection molding, a sealing cylindrical portion is provided on the opening end face of the first portion corresponding to the large-diameter side mounting portion, and after heating the sealing cylindrical portion, Since the sealing cylindrical part softened between the support and the blow outer mold by crushing is crushed to seal the gap between them, gas leakage from this part is prevented, and the bellows part is accurately Can be blow molded.

In the manufacturing method of the present invention, a protrusion extending in the circumferential direction is provided in a sandwiching portion between the support body and the blow outer mold for sandwiching the sealing tubular portion, and the sealing tubular shape is used during mold clamping. part be to collapse the can not bite into the sealing tubular portion that extends axially outward to said protrusion Runode, make them more reliable sealing of the gas.

  Moreover, in the said manufacturing method, the said cylindrical part for a seal | sticker may comprise the taper cylindrical shape of a large diameter, so that the axial direction outward side. Thus, when the cylindrical part for a seal | sticker is made into a taper cylindrical shape, it is excellent in the demolding property when demolding a boot from a support body after blow molding.

  As described above, according to the present invention, it is possible to accurately manufacture a joint boot having a large-diameter side mounting portion whose outer peripheral surface and inner peripheral surface are different shapes, and in particular, the large-diameter side during blow molding. Gas leakage at the attachment portion can be prevented, and the bellows portion can be blow-molded with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  8 and 9 show the joint boot in the embodiment. This joint boot is a thermoplastic resin boot that is attached to the above-described triport type constant velocity joint for automobiles shown in FIGS. 10 and 11, and has a cylindrical large-diameter side mounting portion 2 on one end side in the axial direction. The cylindrical small-diameter side mounting part 4 on the other end side, which is coaxially disposed apart from the large-diameter side mounting part 2, and the hollow bellows part 5 that integrally connects them. The large-diameter side attachment portion 2 is externally fitted on the outer case 1 and the small-diameter side attachment portion 4 is externally fitted on the shaft 3. The outer peripheral surface 2a of the large-diameter side mounting portion 2 is formed in a circular cross section, and the inner peripheral portion 2b is provided with three convex portions 7 projecting radially inwardly in the circumferential direction of 120 degrees. Each of the three convex portions 7 is provided so as to be able to be fitted onto the three concave portions 8 formed on the outer peripheral portion of the outer case 1.

  The convex portion 7 includes an inner wall portion 71 projecting radially inward, and an arc-shaped outer wall portion 72 that constitutes a part of the outer peripheral surface 2a of the large-diameter side attachment portion 2, and these inner wall portions A central support wall 73 that connects the wall portions 71 and 72 at the center in the circumferential direction, and a pair of left and right sides that connect the wall portions 71 and 72 on the left and right sides of the hollow portion between the portion 71 and the outer wall portion 72. Side support walls 74, 74 are provided. The side support wall 74 supports the inner wall portion 71 at an intermediate position between the base portion 71a of the inner wall portion 71 with respect to the outer wall portion and the connecting portion 71b of the central support wall, and the center support wall 73 toward the outer side. By being inclined so as to approach the inner wall portion 71, the inner wall portion 71 is provided substantially perpendicularly. As a result, a plurality of hollow holes 75 a, 75 b, 75 c, 75 d, which are a plurality of hollow portions arranged in the circumferential direction, are provided in the convex portion 7 so as to open at the end face of the large-diameter side mounting portion 2.

  As shown in FIG. 8, a fixing recess 60 extending in the circumferential direction for receiving a ring-shaped band 9 (see FIG. 10) as a fastening member is provided on the outer peripheral surface 2 a of the large-diameter side attachment portion 2. ing. Further, two sealing ribs 61 extending in the circumferential direction are provided on the inner peripheral surface of the large-diameter side mounting portion 2. Similarly, in the small-diameter side mounting portion 4, a fixing recess 62 extending in the circumferential direction for receiving the ring-shaped band 9 that is a fastening member is provided on the outer peripheral surface thereof, and the inner peripheral surface thereof is also provided. Are provided with two sealing ribs 63 extending in the circumferential direction.

  This joint boot is manufactured through the following parison molding process, heating process and blow molding process.

[Parison molding process]
As shown in FIG. 1, a thermoplastic resin (for example, a polyester-based thermoplastic elastomer resin) is discharged from the nozzle 11 of the parison molding apparatus A, and the first portion 12 corresponding to the large-diameter side mounting portion 2 and the small-diameter side mounting A cylindrical parison 15 including a second portion 13 corresponding to the portion 4 and a third portion 14 corresponding to the bellows portion 5 is injection-molded.

  The injection mold 80 includes an injection outer mold 81 that can be divided into a plurality of circumferential directions for molding the outer peripheral side of the parison 15, and a core mold 82 that is mounted inside and molds the inner peripheral side of the parison 15. A cavity 83 is formed between the outer mold 81 and the core mold 82. In this embodiment, the injection outer die 81 is configured to be split into two on the left and right. The core mold 82 is provided so as to mold the second portion 13 at the top portion 82a, and a gate hole 84 leading to the nozzle 11 is provided on the upper surface portion of the outer mold 81 that covers the top of the top portion 82a. Yes.

  The first portion 12 is molded as the large-diameter side attachment portion 2 in the cavity 83, that is, injection-molded into the final product shape of the large-diameter side attachment portion 2. Accordingly, the first portion 12 is formed in a shape in which the outer peripheral surface has a circular cross section and includes a plurality of the convex portions 7 on the inner peripheral portion. 75d is molded. The fixing recess 60 is formed on the outer peripheral surface, and two ribs 61 are formed on the inner peripheral surface.

  The second portion 13 is molded as the small diameter side mounting portion 4 in the cavity 83, that is, is injection molded to the final product shape of the small diameter side mounting portion 4. At this time, the second portion 13 is formed in a cylindrical shape having a smaller diameter than the first portion 12, the fixing recess 62 is formed on the outer peripheral surface, and the two ribs 63 are formed on the inner peripheral surface. . Moreover, the opening surface of the upper end of the 2nd part 13 is obstruct | occluded by the obstruction | occlusion part 13a after injection molding, ie, the parison 15 is shape | molded in the shape of a dome.

  On the other hand, the third portion 14 is not a bellows shape corresponding to the final product shape, but is a parison portion interposed between the first portion 12 and the second portion 13, and is a tapered tube connecting the two. Injection molded into a shape. That is, the third portion 14 is formed in a tapered shape in which the diameter gradually decreases from the large-diameter attachment portion 2 toward the small-diameter attachment portion 4.

  And in this embodiment, the cylindrical part 77 for a seal is integrally extended from the opening end surface (namely, axial direction end surface by the side of the 1st part 12 of the parison 15) 12a of the 1st part 12. As shown in FIG. Specifically, the sealing cylindrical portion 77 extends from the opening end surface 12a to the axially outer side (downward in the drawing) at the entire periphery of the opening end surface 12a of the first portion 12, and is outside the axial direction. It is formed in a tapered cylindrical shape with a larger diameter toward the side. Further, the sealing cylindrical portion 77 of this embodiment is provided on the opening end surface of the outer wall portion 72 in the region of the convex portion 7 in the circumferential direction. Further, as shown in FIG. 4A, the sealing cylindrical portion 77 includes a tapered cylindrical portion 77a having the tapered cylindrical shape, and an opening end surface 12a of the tapered cylindrical portion 77a and the first portion 12. It is comprised by the cutting part 77b which makes | forms the short cylinder shape parallel to the axial direction interposed, and is cut after blow molding in this cutting part 77b. The sealing cylindrical portion 77 is formed with a substantially constant thickness T1 in the axial direction.

  The parison 15 thus injection-molded is taken out from the injection mold 80, and is therefore removed from the core mold 82 and cooled (natural cooling) at room temperature.

[Heating process]
Next, as shown in FIG. 2, the cooled parison 15 is configured such that only the third portion 14 of the first portion 12, the second portion 13, and the third portion 14 is heated to a set temperature (for example, 160 ° C. to 160 ° C.). 200 ° C.).

  The heating device B includes a substantially columnar support 16 that supports the inner peripheral side 15a of the parison 15 in a vertical posture, and includes a rotation drive mechanism M that rotates the support 16 about the axis O thereof. The support 16 includes a lower first fitting portion 20 in which the first portion 12 is fitted concentrically, an upper second fitting portion 22 in which the second portion 13 is fitted concentrically, The intermediate part 21 surrounded by the 3rd part 14 and the support stand part 19 by the side of a lower end part are provided. The second fitting portion 22 constitutes the upper end portion of the support 16, and the tapered column-shaped intermediate portion 21 is provided between the second fitting portion 22 and the first fitting portion 20. The portion 21 has an outer shape that matches the inner peripheral surface of the third portion 14 so that the inner peripheral surface of the third portion 14 is in contact with and supported by the upper and lower intermediate portions 21 without a gap. A tapered surface portion 23 having a tapered surface shape with a smaller diameter is provided between the first fitting portion 20 and the support base portion 19, and the sealing tubular portion 77 is concentric with the tapered surface portion 23. It is comprised so that it may fit outside.

  The heating device B also supports a cylindrical cover member 24 suspended from above the support 16 so that it can be raised and lowered, and a pair of far-infrared heaters 45 are disposed on both lateral sides of the support 16. . The cover member 24 is a member that covers the parison 15 held on the support body 16 and restricts the location where the heat rays from the heater 45 are irradiated. The cover member 24 surrounds the outer periphery of the first portion 12 with a gap. The first cover portion 41 having a cylindrical diameter and the second cover portion 42 having a small diameter that surrounds the outer periphery of the second portion 13 with a gap are provided, and the first cover portion 41 and the second cover portion 42 are provided. The heating opening 44 is provided at a position corresponding to the third portion 14 connected by the connecting portion 43. As a result, the cover member 24 prevents the first portion 12 and the second portion 13 from being exposed to the heat rays from the heater 45, i.e. far infrared rays, and is therefore not heated, and to the third portion 14. The parison 15 is covered so that far infrared rays from the heater 45 are irradiated through the opening 44 over the entire height direction. Moreover, in this embodiment, the dimension of the height direction is set so that the heater 45 can also heat the said cylindrical part 77 for a seal | sticker exposed from the lower end of the 1st cover part 41. FIG.

  Using the heating device B, first, the first portion 12 is externally fitted to the first fitting portion 20 of the support 16 in a concentric manner with respect to the support 16, and the second portion 13 is the first of the support 16. 2 is fitted concentrically to the fitting portion 22, the third portion 14 is fitted concentrically to the intermediate portion 21 of the support 16, and the sealing cylindrical portion 77 is concentric to the tapered surface portion 23. The parison 15 is supported by the support body 16 so as to be in an externally fitted state. Next, as shown in FIG. 2, the cover member 24 is lowered to cover the entire parison 15 supported by the support body 16, and the third portion 14 and the sealing cylinder are rotated while the support body 16 is rotated around its axis O. The shaped portion 77 is heated by the heaters 45 on both lateral sides.

[Blow molding process]
After the above heating is completed, as shown in FIG. 3, the outer peripheral side 15b of the parison 15 is covered with a blow outer mold 51 having a bellows-like shape while the parison 15 is supported by the support 16, and the support Gas is injected from the injection port 52 provided in 16 to the inner peripheral surface of the third portion 14, and the third portion 14 is pressed against the blow outer mold 51 to form the bellows portion 5.

  The blow outer mold 51 is formed so as to be divided into a plurality of pieces in the circumferential direction. The blow outer mold 51 is formed by laminating a plurality of plate-shaped molds 54 in the vertical direction so that a mold matching surface 53 is provided for each peak of the bellows part 5 to be molded. The air in the mold can be exhausted through the mold matching surface 53. Further, the blow outer mold 51 is provided with a pipe 55 for flowing cooling water to each mold matching surface 53.

  The support body 16 that supports the parison 15 is a core mold that is mounted in the blow outer mold 51 during blow molding, and includes a gas passage 56 that extends in the vertical direction along the axis O. The gas passage 56 is connected to an injection port 52 provided on the outer periphery of the lower surface of the second fitting portion 22 of the support 16 and is connected to a pressure increase tank and an exhaust tank (not shown) in a switchable manner. The gas from the pressure boosting tank is sent to the injection port 52 and used to exhaust the gas in the mold by the action of the exhaust tank.

  The blow outer mold 51 includes a fitting mold part 57 that externally fits the support base part 19 of the support body 16 in a concentric manner. When the mold is closed with the support body 16, the support mold part 57 supports the support base part 19. It is comprised so that the outer periphery of may be held. A tapered surface portion 58 corresponding to the tapered surface portion 23 of the support body 16 is provided on the inner peripheral surface of the upper end portion of the fitting mold portion 57, and the taper surface portion 58 of the fitting mold portion 57 and the taper of the support body 16 are provided. The gap T2 with the surface portion 23 is set to be sufficiently smaller than the thickness T1 of the sealing cylindrical portion 77 (see FIGS. 4A and 4B).

  When the blow outer die 51 is closed with respect to the support 16, the upper end opening surface of the second portion 13 is closed by the closing portion 13 a, so that no gas sealing is required at the upper end portion of the parison 15. Therefore, it is only necessary to seal the first portion 12 at the lower end, and the sealing tubular portion 77 is provided as described above for the purpose of sealing.

  Specifically, in the state before the mold clamping by the blow outer mold 51, as shown in FIG. 4A, the sealing cylindrical portion 77 of the parison 15 that covers the tapered surface portion 23 of the support 16 is formed at the tip thereof. Is located in the tapered surface portion 23. When the blow outer die 51 is clamped from this state, as shown in FIG. 4B, the sealing cylindrical portion 77 is sandwiched between the tapered surface portion 58 of the blow outer die 51 and the tapered surface portion 23 of the support 16. Thus, the sealing cylindrical portion 77 softened by the heating is crushed. As a result, the gap T2 between the outer peripheral surface of the support 16 and the inner peripheral surface of the blow outer mold 51 is filled with the crushed seal cylindrical portion 77, so that high sealing performance is exhibited. That is, in this embodiment, the taper surface portion 58 of the blow outer mold 51 and the taper surface portion 23 of the support body 16 constitute a sandwiching portion 59 that sandwiches the seal tubular portion 77, and the softened tubular portion 77 for sealing is provided. The air is sealed by being pinched by the pinching portion 59 and plastically deforming so as to fill the gap T2.

  In particular, in this embodiment, a protrusion 90 extending in the circumferential direction is provided on the holding portion 59 over the entire circumference. As shown in FIG. 4A, the protrusion 90 is provided on the support 16 side, and more specifically, a corner (edge) extending from the tapered surface portion 23 of the support 16 to the cylindrical support base 19. Part). Then, as shown in FIG. 4B, when the mold is clamped, the sealing cylindrical portion 77 is crushed as described above so that it extends outward in the axial direction and bites into the ridge 90, thereby Higher sealing performance is exhibited.

  After the bellows portion 5 is blow-molded in this manner while ensuring the sealing performance, the joint boot is obtained by cutting off the closing portion 13a on the upper end opening surface of the second portion 13 and the cylindrical portion 77 for sealing. .

  In the present embodiment configured as described above, the large-diameter side mounting portion 2 and the small-diameter side mounting portion 4 are set to a final product shape with high dimensional accuracy by injection molding at the time of parison molding, and the bellows portion 5 Since the final product shape is formed by blow molding, not only the small-diameter side attaching portion 4 but also the large-diameter side attaching portion 2 whose shape of the inner peripheral portion 2b is greatly different from that of the outer peripheral portion can be accurately formed. it can.

  Also, a sealing cylindrical portion 77 is provided in the parison 15, and a sealing protrusion is formed between the outer peripheral surface of the support 16 and the inner peripheral surface of the blow outer die 51 by clamping the blow outer die 51 during blow molding. Since the strip 77 is crushed and sealed, the gas blown into the inside of the third portion 14 can be prevented from leaking outside through the inner peripheral side of the first portion 12. Blow molding can be performed with high accuracy.

  Further, the first portion 12 and the second portion 13 are heated without heating the third portion 14 that forms the bellows portion 5 to the set temperature with the heating device B, and then the third portion 14 is blow molded. The temperature distribution of the third portion 14 in the state before blow molding is less likely to vary, so that the third portion 14 can be uniformly expanded when blow molded, and thus the thickness of the bellows portion 5 can be made uniform. Can be molded. Further, since the support 16 used at the time of heating is used as it is and blow molding is performed, it is not necessary to newly support the parison with a member dedicated to blow molding having an injection port after the heating of the third portion 14 is completed. It is possible to reduce the labor required for blow molding.

  FIGS. 5-7 shows the example of a change of the said cylindrical part 77 for a seal | sticker.

  In the first modification, as shown in FIG. 5A, the sealing cylindrical portion 77 is formed in a cylindrical shape having a constant aperture in the axial direction. Therefore, the outer peripheral surface 16a of the support 16 that sandwiches the sealing cylindrical portion 77 and the inner peripheral surface 51a of the blow outer mold 51 are also formed in a cylindrical surface shape parallel to the axial direction. Further, the protrusion 90 is formed to protrude in the shape of a cross section on the outer peripheral surface 16 a of the support 16. Then, as shown in FIG. 5 (b), the sealing cylindrical portion 77 that is crushed between the outer peripheral surface 16a of the support 16 and the inner peripheral surface 51a of the blow outer die 51 at the time of clamping is downward. It extends and bites into the ridge 90, and is configured to exhibit high sealing performance.

  In the second modification, as shown in FIG. 6A, the sealing cylindrical portion 77 is formed in a cylindrical shape having a constant aperture in the axial direction. Therefore, the outer peripheral surface 16a of the support 16 that sandwiches the sealing cylindrical portion 77 and the inner peripheral surface 51a of the blow outer mold 51 are also formed in a cylindrical surface shape parallel to the axial direction. However, in this example, tapered surface portions 16b and 51b having larger diameters are respectively provided at the lower ends of the outer peripheral surface 16a and the inner peripheral surface 51a having a cylindrical surface shape. Further, the protrusions 90 are formed at the corners extending from the cylindrical inner peripheral surface 51a of the blow outer mold 51 to the tapered surface portion 51b. Then, as shown in FIG. 6 (b), a sealing cylindrical portion 77 that is crushed between the outer peripheral surface 16a of the support 16 and the inner peripheral surface 51a of the blow outer die 51 at the time of clamping is downward. It extends and bites into the ridge 90, and is configured to exhibit high sealing performance.

  In the third modified example, as shown in FIG. 7A, the sealing cylindrical portion 77 is provided along the inner peripheral edge of the convex portion 7 in the region of the convex portion 7 in the circumferential direction. Therefore, the sealing tubular portion 77 is provided with a connecting portion 77 c extending in the radial direction between the tapered tubular portion 77 a and the cutting portion 77 b in the region of the convex portion 7. Other configurations are the same as those in the above embodiment, and as shown in FIG. 7B, the mold is crushed between the tapered surface portion 58 of the blow outer mold 51 and the tapered surface portion 23 of the support 16 at the time of clamping. The sealing cylindrical portion 77 extends downward and bites into the ridge 90 so that high sealing performance is exhibited.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for manufacturing a joint boot used for a constant velocity joint of an automobile.

Diagram showing the parison molding process Diagram showing the heating process Diagram showing blow molding process It is a principal part expanded sectional view at the time of blow molding, (a) shows before mold closing, (b) shows after mold clamping, respectively. It is a principal part expanded sectional view at the time of the blow molding which concerns on a 1st modification, (a) shows before mold closing, (b) shows after mold clamping, respectively. It is a principal part expanded sectional view at the time of blow molding concerning the 2nd modification, (a) shows before mold closing and (b) shows after mold clamping, respectively. It is a principal part expanded sectional view at the time of blow molding concerning the 3rd modification, (a) shows before mold closing and (b) shows after mold clamping, respectively. Partial cutaway view showing joint boots The figure which shows the large diameter side attachment part of the joint boot Vertical section showing constant velocity joint and joint boot Diagram showing constant velocity joint

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer case, 2 ... Large diameter side attaching part, 3 ... Shaft, 4 ... Small diameter side attaching part, 5 ... Bellows part, 7 ... Convex part, 8 ... Concave part, 12 ... 1st part, 12a ... Opening end surface, 13 ... 2nd part, 14 ... 3rd part, 15 ... Parison, 15a ... Inner circumferential side of parison, 15b ... Outer circumferential side of parison, 16 ... Support, 59 ... Clamping part, 77 ... Cylindrical part for sealing, 77a ... Tapered cylindrical portion, 90 ... ridge, T1 ... thickness of cylindrical portion for sealing, T2 ... clearance between support and blow outer mold

Claims (2)

A cylindrical large-diameter side mounting part that is fitted with a plurality of convex parts projecting from the inner peripheral part and fitted into a concave part of the outer case, and a cylindrical small-diameter side mounting part that is attached to the shaft, and both A method of manufacturing a joint boot comprising a bellows portion to be connected,
A parison comprising: a first part that forms a product shape of the large-diameter side attachment portion; a second part that forms a product shape of the small-diameter side attachment portion; and a third portion that connects the first portion and the second portion. A parison molding process of injection molding with thermoplastic resin,
Of the first part, the second part, and the third part of the parison, a heating step of heating the third part to a set temperature with a heating device;
The outer peripheral side is covered with a blow outer mold in a state where the inner peripheral side of the heated parison is supported by a support, and the third part is pressed against the blow outer mold by injecting gas into the third part. And a blowing step for forming the bellows part,
In the parison molding step, a cylindrical portion for sealing is integrally extended from the opening end surface of the first portion to the parison,
In the heating step, the cylindrical portion for sealing is heated together with the third portion,
In the blowing step, the sealing cylindrical portion is crushed between the support and the blow outer mold by clamping the blow outer mold against the support supporting the parison , At the time, the crushing portion extending in the circumferential direction provided on the support body or the blow outer mold at the holding portion between the support body and the blow outer mold sandwiching the sealing tubular portion causes the outer side in the axial direction by the crushing. Blow molding is performed by injecting the gas while the gap between the support and the blow outer mold is sealed by biting the sealing cylindrical portion that is plastically deformed and stretched to the side. A method for manufacturing joint boots. The sealing tubular portion, to name a more axially outward side large-diameter tapered tube, said support, and having a tapered surface portion of the tapered tube of the sealing tubular portion is fitted, the A cylindrical support base is provided on the outer side in the axial direction of the taper surface, and the protrusion is provided at a corner between the taper surface and the support base. The method for manufacturing a joint boot according to claim 1, wherein the tubular portion for use is extended outward in the axial direction so as to bite into the protrusion .

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