JP4081106B2 - Joint boot manufacturing method - Google Patents

Description

  The present invention connects a cylindrical large-diameter side mounting portion that is attached by fitting a plurality of convex portions protruding from the inner peripheral portion to the concave portion of the outer case, and a small-diameter side mounting portion that is attached to the shaft. The present invention relates to a method of manufacturing a joint boot including an accordion portion.

  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.

  The joint boot described at the beginning is provided with respect to such a constant velocity joint, prevents dust and foreign matter from entering the constant velocity joint, and holds grease around the constant velocity joint. On the outer periphery of the outer case 1, a plurality of recesses 8 that are recessed radially inward are provided in the circumferential direction so as to reduce the weight of the case. Correspondingly, a plurality of convex portions 7 projecting radially inward are provided on the inner peripheral portion of the large-diameter side attachment portion 2 of the joint boot 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 joint boot made of resin is generally manufactured by molding a small-diameter side attachment portion by injection molding and then blow-molding other bellows portions and a large-diameter side attachment portion (see, for example, Patent Document 1). ). However, it is necessary to make the large-diameter side mounting portion 2 as described above into an irregular shape having an outer peripheral surface that is a perfect circle and an inner peripheral surface that has convex portions at a plurality of locations in the circumferential direction. In this case, it cannot be produced by such general injection blow molding. This is because, in blow molding, the thickness in the circumferential direction is uniform or substantially uniform, and thus, such a deformed shape cannot be molded by blow molding the large-diameter side attachment portion.

  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 step of injection-molding a parison with a molding material, and covering the third part with a blow outer mold, and an inner side of the third part, comprising: a second part; and a third part connecting the first part and the second part; And a blowing step of forming the bellows portion by injecting gas into the blow outer mold and pressing the third portion against the blow outer mold. In the blowing step, the inner periphery of the parison is supported by a support, and the support has a lower fitting portion in which the first portion is fitted concentrically, and the second portion is concentric. An upper fitting portion that is externally fitted in a shape and an intermediate portion surrounded by the third portion are provided, and a seal ring made of an elastic body is provided on the outer peripheral surface of the lower fitting portion . In addition, the blow outer mold includes a fitting mold part that concentrically fits a cylindrical support base part on the lower end side of the support body, and the outer peripheral surface of the support base part is a convex extending in the circumferential direction. A strip is provided over the entire circumference, and a concave groove into which the convex strip is fitted is provided on an inner peripheral surface of the fitting mold portion, and an upper surface and a lower surface of the convex strip are in a direction perpendicular to the axis of the support. It is formed in an inclined tapered surface shape, and the upper and lower surfaces of the corresponding groove are formed in the same tapered surface shape, and when the blow outer mold and the support are closed, the groove groove The upper surface and the lower surface of the ridge are in contact with the upper surface and the lower surface, respectively, without gaps, and the ridges are fitted into the grooves so that a gap is secured between the tip of the ridges and the bottom of the grooves. Include. Then, blow molding is performed by injecting the gas in a state in which the blow outer mold is clamped to the support and the inner peripheral surface of the first portion is pressed against the seal ring.

  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.

In addition, a seal ring is provided on the outer peripheral surface of the first fitting portion of the support body to which the first portion of the parison is fitted, and the inner peripheral surface of the first portion is pressed against the seal ring by clamping the blow outer mold, Since the seal ring is compressed by elastic deformation, gas leakage from this portion is prevented, and the bellows portion can be blow-molded with high accuracy. Furthermore, when the blow outer mold and the support are closed, the support and the blow outer mold can be positioned in the vertical direction by fitting the protrusions of the support base and the concave grooves of the fitting mold. In addition, the blow outer mold and the support core can be prevented from being tilted so that the center can be centered between them. Even if the fitting length in the axial dimension is short, it can be centered.

  In the manufacturing method of the present invention, after the parison is cooled, only the third portion for forming the bellows portion among the first portion, the second portion, and the third portion is set by the heating device from the radially outer side. It is preferable to perform the blow molding after heating to a temperature. Thereby, variation in the temperature distribution of the third portion in the state before blow molding can be made difficult to occur. Here, if a cylindrical parison is molded in the parison molding process, the temperature distribution of the parison varies, but if it is blow-molded as it is without being heated, However, it is difficult to swell the low-temperature portion, and it becomes difficult to uniformly mold the bellows portion. On the other hand, after the injection molding, after cooling once, only the third part is heated from the radially outer side as described above, thereby making it difficult to cause variations in the temperature distribution of the third part. Therefore, when the third portion is blow-molded, it can be uniformly expanded, and the thickness of the bellows portion can be uniformly formed.

  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 elastomer resin boot to be mounted on 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. And a cylindrical small-diameter-side attachment portion 4 on the other end side that is coaxially disposed apart from the large-diameter-side attachment portion 2 and a hollow bellows portion 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 walls 74 are formed so as to be inclined so as to approach the center support wall 73 toward the outside. More specifically, the side support wall 74 is configured so that the inner wall portion 71 is supported by the central support wall 73 and the side support walls 74 and 74 at equal intervals in the circumferential direction. The inner wall portion 71 is supported at an intermediate position between the base portion 71a and the connecting portion 71b of the central support wall, that is, connected to the inner wall portion 71 at the intermediate position. The connecting portion is provided so as to incline toward the center as it goes outward from the connecting portion so as to intersect the inner wall portion 71 substantially perpendicularly.

  With this configuration, the convex portion 7 is provided with a plurality of hollow holes 75 that are a plurality of hollow portions arranged in the circumferential direction. Specifically, the convex portion 7 is formed with two pairs of bottomed hollow holes 75a, 75b, 75c, and 75d that open at the end face of the large-diameter side attachment portion 2 and are symmetric with respect to the center line L in the circumferential direction. The depth of each of the hollow holes 75a to 75d is set to be the same.

  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, the molding material is discharged from the nozzle 11 of the parison molding apparatus A, the first portion 12 corresponding to the large diameter side mounting portion 2, the second portion 13 corresponding to the small diameter side mounting portion 4, A cylindrical parison 15 including the 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.

  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.).

  As shown in FIGS. 2 and 7, the heating device B has a stepped columnar support 16 with respect to the parison 15 arranged in a vertical posture and a rotation drive mechanism M that rotates the support 16 around its axis O. Is provided. The support 16 is a member that supports the inner peripheral side of the parison 15, and includes a lower fitting portion (first fitting portion) 20 in which the first portion 12 is fitted concentrically and a second portion 13. An upper fitting portion (second fitting portion) 22 that fits concentrically, an intermediate portion 21 surrounded by the third portion 14, and a support base portion on the lower end side that receives the opening end surface 12 c of the first portion 12. 19. The lower fitting portion 20 is provided at the upper end of the columnar support base 19 and has a smaller diameter than the support base 19. The upper fitting portion 22 constitutes the upper end portion of the support body 16, and the tapered column-shaped intermediate portion 21 is provided between the upper fitting portion 22 and the lower fitting portion 20. Has an outer shape that matches the inner circumferential surface of the third portion 14 so that the inner circumferential surface of the third portion 14 is supported in contact with the upper and lower intermediate portions 21 without a gap.

  The heating device B also includes a cylinder 25 that suspends and supports a cylindrical cover member 24 above the support body 16 and raises and lowers the cover member 24, and a pair of laterally outward sides of the support body 16. A far infrared heater 45 is provided. 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.

  Using the heating device B, first, the first portion 12 is externally fitted to the lower fitting portion 20 of the support body 16 with respect to the support body 16, and the second portion 13 is the upper side of the support body 16. The parison 15 is supported on the support body 16 so that the third section 14 is fitted on the intermediate portion 21 of the support body 16 in a concentric manner. reference). Next, the cover member 24 is lowered by the cylinder 25 and is put on the entire parison 15 supported by the support 16 (see FIG. 2). Then, the third portion 14 is heated by the heaters 45 on both lateral sides while rotating the support 16 around the axis O.

[Blow molding process]
After the heating of the third portion 14 is completed, as shown in FIG. 3, while the parison 15 is supported by the support body 16, the mold surface is covered with the bellows-shaped blow outer mold 51, and the jet provided on the support body 16. Gas is injected from the mouth 52 onto 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. The blow outer mold 51 is provided with a pipe 55 for flowing cooling water. The pipe 55 is configured by providing the plate-shaped mold 54 with an arc-shaped groove extending along the outer periphery of the parison 15 on 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 upper 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 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. On the outer peripheral surface of the support base 19, convex ridges 58 extending in the circumferential direction are provided over the entire circumference, and on the inner peripheral surface of the fitting mold part 57, a concave groove 59 into which the ridges 58 are fitted extends over the entire circumference. Is provided.

  As shown in FIG. 6 (a), the ridge 58 has a tapered surface shape in which the upper surface 58a and the lower surface 58b are both inclined with respect to the axis P direction perpendicular to the support 16 (direction perpendicular to the axis O). In other words, the ridges 58 have a trapezoidal shape that is gradually narrowed toward the top on the radially outer side. Both the upper surface 59 a and the lower surface 59 b of the concave groove 59 are formed in a tapered surface shape similar to the ridge 58. As shown in FIG. 6B, the groove 59 is formed deeper than the protruding height of the ridge 58 so that a gap 95 is secured at the tip when the ridge 58 is fitted. .

  With this configuration, when the blow outer mold 51 and the support 16 are closed, the ridges 58 of the support base 19 fit into the grooves 59 of the fitting mold 57, and the upper and lower surfaces 59a and 59b of the grooves 59 The upper and lower surfaces 58a, 58b of the ridges 58 are fitted in a state where they are in contact with each other without any gap. Therefore, the support body 16 and the blow outer mold 51 can be positioned in the vertical direction, and the axial cores of the blow outer mold 51 and the support body 16 can be prevented from being tilted and centered between them. Further, by providing such a concave and convex fitting mechanism, it is possible to center even if the fitting length in the axial dimension between the support base 19 and the fitting mold portion 57 is short.

  Thus, when closing the blow outer mold 51 with respect to the support body 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. It is. Therefore, it is only necessary to seal the first portion 12 at the lower end, and for the sealing, the lower fitting portion 20 of the support 16 is provided with a seal ring 90 made of a rubber elastic body.

  The seal ring 90 is provided on the outer peripheral surface 20 a of the lower fitting portion 20. Specifically, as shown in FIG. 4, the shoulder on the intermediate portion 21 side of the lower fitting portion 20 is provided with a concave groove 91 that opens outward in the radial direction over the entire circumference. A seal ring 90 made of a rubber member having a circular shape as a whole and having a circular cross section is disposed in the concave groove 91 over the entire circumference. Since the plurality of convex portions 7 are provided on the inner peripheral portion of the first portion 12 as described above, the outer peripheral surface 20a of the lower fitting portion 20 is correspondingly formed in a concave shape at a plurality of locations in the circumferential direction. Therefore, the seal ring 90 is provided in the circumferential direction along the uneven shape (see a two-dot chain line in FIG. 9).

  A part of the seal ring 90 protrudes from the concave groove 91 before being clamped, and is pressed by the inner peripheral surface 12a of the first portion 12 by clamping. That is, by clamping the blow outer mold 51 against the support 16, the first portion 12 of the parison 15 is pressed radially inward by the blow outer mold 51 as shown in FIG. The inner peripheral surface 12a of the first portion 12 is pressed against the seal ring 90 and the seal ring 90 is compressed, so that the sealing performance is exhibited.

  The seal ring 90 may be in a position where it is compressed by such mold clamping. In the first portion 12 having the convex portion 7, a hollow hole 75 is provided in the convex portion 7. Since the support walls 73 and 74 are provided in this portion, the clamping force due to mold clamping is not increased. The seal ring 90 is exerted via the support walls 73 and 74, and the sealing performance is exhibited. In particular, in the present embodiment, prior to blow molding, only the third portion 14 is heated and the first portion 12 is not heated. Therefore, even if tightened as described above, deformation at the convex portion 7 is suppressed. .

  More preferably, as shown in FIG. 5, a seal ring 90 is provided at an axial position where the hollow hole 75 does not exist. In the example of FIG. 5, a thin wall portion 77 that does not have a hollow hole on the outer periphery is provided on the inner side in the axial direction (the bellows portion 5 side) of the region where the thin hole 75 is provided, and corresponds to the thin wall portion 77. A seal ring 90 is provided at the position. Then, by pressing the outer peripheral surface of the thin wall portion 77 by the blow outer mold 51, the seal ring 90 is compressed by the inner peripheral surface of the wall portion 77, and the sealing performance is exhibited. With this configuration, it is not necessary to press the hollow hole 75 portion, which requires strict dimensional accuracy, at the time of clamping, so even if the first portion 12 is heated, The deformation | transformation in the convex part 7 to have can be suppressed reliably.

  After the bellows portion 5 is blow-molded in this way while ensuring the sealing performance, the joint boot is obtained by cutting off the closed portion 13a of the upper end opening surface of the second portion 13.

  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.

  Further, a seal ring 90 is provided on the outer peripheral surface 20a of the lower fitting portion 20 to which the first portion 12 of the parison 15 is externally fitted, and the inner peripheral surface of the first portion 12 is clamped by the blow outer die 51 during blow molding. 12a is pressed against the seal ring 90 to compress the seal ring 90, so that the gas blown into the inside of the third portion 14 leaks outside through the inner peripheral side of the first portion 12. Can be prevented, and the bellows portion 5 can be blow-molded with high accuracy. In particular, the arc-shaped portion 76 of the large-diameter side mounting portion 2 has a problem that gas is likely to leak because it is easy to move due to the blow pressure as compared with the convex portion 7. Leakage can be reliably prevented.

  Moreover, since only the 3rd part 14 which shape | molds the bellows part 5 is heated to preset temperature with the heating apparatus B, and this 3rd part 14 is blow-molded after that, the temperature of the 3rd part 14 in the state before blow-molding The distribution is less likely to vary, so that the third portion 14 can be uniformly expanded when blow-molded, and therefore the thickness of the bellows portion 5 can be uniformly 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.

  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 3 is an enlarged cross-sectional view of the main part of FIG. Sectional drawing which shows the state at the time of blow molding which concerns on other embodiment It is a partially expanded sectional view of a blow molding die, (a) shows before mold closing and (b) shows after mold closing, respectively. Diagram showing heating device 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 ... Inner peripheral surface, DESCRIPTION OF SYMBOLS 13 ... 2nd part, 14 ... 3rd part, 15 ... Parison, 16 ... Support body, 20 ... Lower side fitting part (1st fitting part), 20a ... Outer peripheral surface, 21 ... Middle part, 22 ... Upper side fitting Joint part (second fitting part), 51 ... blow outer mold, 90 ... seal ring

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 process of injection molding with a molding material;
A blow step of covering the third portion with a blow outer mold and forming the bellows portion by pressing the third portion against the blow outer mold by injecting gas into the third portion;
In the blowing step,
The parison is supported by a support on the inner peripheral side, and the support includes a lower fitting portion in which the first portion is fitted concentrically and an upper fitting in which the second portion is fitted concentrically. Comprising a joint portion and an intermediate portion surrounded by the third portion, and provided with a seal ring made of an elastic body on the outer peripheral surface of the lower fitting portion,
The blow outer mold includes a fitting mold part that externally fits a cylindrical support base part on the lower end side of the support body in a concentric manner, and a convex strip extending in the circumferential direction is formed on the outer peripheral surface of the support base part. In addition to being provided over the entire circumference, the inner peripheral surface of the fitting mold part is provided with a concave groove into which the convex stripe is fitted, and the upper and lower surfaces of the convex stripe are inclined with respect to the direction perpendicular to the axis of the support The upper surface and the lower surface of the corresponding groove are formed in the same tapered surface shape, and when the blow outer mold and the support are closed, the upper surface and the lower surface of the groove are formed. The upper surface and the lower surface of the ridge are in contact with the lower surface without any gap, and the ridge is fitted into the groove so that a gap is secured between the tip of the ridge and the bottom of the groove,
A joint boot characterized in that blow molding is performed by injecting the gas in a state in which the blow outer mold is clamped to the support and the inner peripheral surface of the first portion is pressed against the seal ring. Manufacturing method.   After the parison is cooled, only the third portion of the first portion, the second portion, and the third portion is heated to a set temperature with a heating device from the radially outer side, and then blow molding is performed. The method for manufacturing a joint boot according to claim 1.

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