JP2012077841A - Resin sheet manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a resin sheet from broken due to cold slag.SOLUTION: In the resin sheet manufacturing method, a capacity 53 in which the resin sheet is formed, a gate 51c in which resin is injected into the capacity 53, and a protrusion 52d for forming a groove of the resin sheet are formed in an injection molding die 50, the resin melted from nozzles 60, 61 of an injection molding machine is injected into the capacity 53 via the gate 51e, and thus the resin sheet with the groove is formed, The protrusion 52d is formed on a line on which the resin is injected to the capacity 53 from the gate 51c, a recess 52f is formed at the protrusion 52d, the recess 52f has a depth in a direction in which the resin is injected from the nozzles 60, 61 and also has a depth in such a level that the resin does reach a root of the protrusion 52d, the cold slag generated at tips of the nozzles 60, 61 is retained in the recess 52f, and after that, the molten resin is injected into the remaining part of the capacity 53.

Description

  The present invention relates to a method for producing a resin sheet used for a ball joint of an automobile.

  As shown in Patent Document 1, a ball joint of an automobile has a ball stud having a ball head at one end, a resin sheet that covers the ball head, and the ball stud that is tiltably connected via the resin sheet. It consists of a housing.

  The resin sheet is molded by an injection mold 100 as shown in FIG. The injection mold 100 includes a fixed mold 110 and a movable mold 120, and a space corresponding to the resin sheet, that is, a capacity 130 is provided between the fixed mold 110 and the movable mold 120. Is formed.

  In the injection mold 100, a runner 140, which is a resin passage for guiding the molten resin from the nozzle 150 of the injection molding machine to the capacity 130, is formed. The runner 140 is formed in a direction perpendicular to the first runner 141 and a first runner 141 formed in the same direction as the moving direction 120 of the movable mold 120 with respect to the fixed mold 110. A second runner 142 and a reservoir 143 formed in the movable mold 120 beyond the second runner 142 on the extended line of the first runner 141.

  A cold slug in which the resin has cooled and hardened is generated at the tip of the nozzle 150 at each injection molding. The cold slug is pushed into the pool portion 143 every time injection molding is performed, and the completely melted resin is injected into the capacity 130 through the second runner 142.

  When the resin in the injection mold 100 is cooled and solidified, the movable mold 120 is separated from the fixed mold 110, and a resin molded product is taken out from the injection mold 110. The resin sheet is taken out by separating the resin of the runner 140 portion from the resin molded product.

JP 2010-127368 A

  Since the resin of the runner 140 part is discarded, this part is extra material cost. As a countermeasure against this, there is a method of injecting resin directly into the capacity from the nozzle, but it is impossible to predict where the cold slug will stay, and if the cold slug is in contact with the ball head of the resin sheet If the slug stays, this part may break during use. The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing a resin sheet in which the resin sheet is not broken by a cold slug formed at the tip of a nozzle.

The invention according to claim 1 is provided with a capacity in which a resin sheet is molded, a gate into which resin is injected into the capacity, and a protrusion that forms a groove in the resin sheet, in the injection mold. In the resin sheet manufacturing method in which the resin melted from the nozzle of the injection molding machine is injected into the capacity through the gate, thereby forming a grooved resin sheet.
The protrusion is provided on a line through which resin is injected from the gate to the capacity, and a recess is provided in the protrusion. The recess has a depth in a direction in which the resin is injected from the nozzle, and the protrusion has a depth. The cold slug formed at the tip of the nozzle has a depth that does not reach the root, and the molten resin is injected into the remaining capacity after being held in the recess.

  According to the present invention, since the cold slug formed at the tip of the nozzle is embedded in the resin sheet, the waste of the resin can be reduced and the material cost can be reduced. In addition, since the cold slug can be held in a position slightly recessed from the outer surface of the resin sheet, the outer surface of the resin sheet may be broken even if the ball head is brought into sliding contact with the outer surface of the resin sheet. Absent.

Sectional drawing of the ball joint which applied the resin sheet in embodiment of this invention Sectional drawing of the injection mold which shape | molds the resin sheet in embodiment of this invention The partially expanded sectional view of FIG. 2 in embodiment of this invention 2 is a view in the direction of arrow A in FIG. 2 according to the embodiment of the present invention. Sectional drawing of the resin sheet which carried out the cross section in the groove part in embodiment of this invention Sectional drawing of the resin sheet which carried out the cross section by the sliding surface in embodiment of this invention Sectional view of a conventional injection mold for resin sheets

  An embodiment of the present invention will be described with reference to FIGS. 1 to 6. 1 is a sectional view of a ball joint to which a resin sheet is applied, FIG. 2 is a sectional view of an injection mold for molding the resin sheet, FIG. 3 is a partially enlarged sectional view of FIG. 2, and FIG. 2 is a cross-sectional view of the resin sheet taken along the groove portion, and FIG. 6 is a cross-sectional view of the resin sheet taken along the sliding surface.

  The ball joint 10 shown in FIG. 1 is attached between a power steering device and a tire hub. The ball joint 10 is connected to the housing 20 so as to be tiltable through the housing 20 screwed and fixed to the rack shaft 90 of the power steering apparatus, the resin sheet 30 accommodated in the housing 20, and the resin sheet 30. The ball stud 40 is made of.

  The ball stud 40 has a spherical ball head 41 at one end, and the ball head 41 is slidably in contact with the resin sheet 30. The other end of the ball stud 40 is connected to the hub side of the tire. The housing 20 is caulked from a state indicated by a two-dot chain line to a state indicated by a solid line. This caulking prevents the ball stud 40 from coming off from the housing 20.

  As shown in FIG. 5, the resin sheet 30 includes a bottom portion 32 having a hole 31, a tapered portion 33 formed continuously with the bottom portion 32, and a cylindrical shape formed continuously with the tapered portion 33. It consists of a cylindrical part 34. On the inner periphery of the resin sheet 30, there are a sliding surface 35 on which the spherical head 41 is slidably slidable, an axial groove 36 formed in the axial direction at four locations on the circumference, a tapered portion 33 and a cylindrical portion. An annular groove 37 formed in the circumferential direction at the boundary of 34 is formed. Grease is held in the axial groove 36 and the annular groove 37, and the grease is supplied to the sliding surface 35 as the ball stud 40 tilts. Of the four axial grooves 36, a convex portion 38 is formed in one axial groove 36 on the bottom 32 side. The convex portion 38 protrudes from the bottom of the axial groove 36 to a position slightly recessed from the sliding surface 35. The convex portion 38 is formed from the hole 31 to the boundary between the bottom portion 32 and the tapered portion 33 in the radial direction.

  As shown in FIGS. 2 and 3, the injection mold 50 includes a fixed mold 51 and a movable mold 52 that approaches and separates from the fixed mold 51. A space having the same shape as the resin sheet 30, that is, a capacity 53 is formed between the fixed mold 51 and the movable mold 52.

  The fixed mold 51 is formed with a cup-shaped inner peripheral surface 51 a that forms the bottom portion 32, the taper portion 33, and the cylindrical portion 34 of the resin sheet 30.

  The movable mold 52 includes a small-diameter cylindrical portion 52 a that forms the hole 31 of the resin sheet 30, a hemispherical portion 52 b that forms a semispherical inner peripheral surface of the tapered portion 33 of the resin sheet 30, and the resin sheet 30. A large-diameter cylindrical portion 52c that forms a cylindrical inner peripheral surface of the cylindrical portion 34 is continuously formed.

  On the outer peripheral surfaces of the hemispherical portion 52b and the large-diameter cylindrical portion 52c, axial protrusions 52d forming the axial grooves 36 are formed in four directions on the circumference in the detaching direction N of the movable mold 52. Yes. An annular protrusion 52e that forms the annular groove 37 of the resin sheet is formed on the outer peripheral surface of the boundary between the hemispherical portion 52b and the large-diameter cylindrical portion 52c. The axial projection 52d is formed from one end of the hemispherical portion 52b on the small-diameter cylindrical portion 52a side to one end of the large-diameter cylindrical portion 52c opposite to the hemispherical portion 52b, and is divided by the annular projection 52e in the middle. ing.

  Of the four axial projections 52d, one axial projection 52d is formed with a recess 52f at one end on the small diameter cylindrical portion 52a side as shown in FIG. The recess 52f has a depth that does not reach the base of the axial projection 52d, and the recess 52f has a width narrower than the width of the axial projection 52d in the circumferential direction. In other words, the recess 52f is a substantially rectangular recess having only one surface opened and the remaining five surfaces closed. The protrusions 38 of the resin sheet 30 are formed by the recesses 52f.

  Two capacities 53 are formed in the injection mold 50. A taper-shaped taper hole 51b is formed in the fixed mold 51 at a position corresponding to the recess 52f of each capacity 53, and a boundary between the taper hole 51b and the capacity 53 is a gate 51c as an entrance of the capacity 53. It becomes. The gate 51c is formed at a position facing the open surface of the recess 52f.

  The injection molding machine has two nozzles 60 and 61, and each nozzle 60 and 61 is provided at a position corresponding to the tapered hole 51b. The nozzles 60 and 61 are connected to a branch pipe 62, and the branch pipe 62 is connected to an unillustrated extrusion device for extruding resin. A heater 63 is wound around the branch pipe 62 so that the resin melted by heat does not cool and harden.

  Next, the operation of this embodiment will be described based on the configuration of the above-described embodiment.

  The movable mold 52 is pressed against the fixed mold 51 to form the capacity 53 between the fixed mold 51 and the movable mold 52. The nozzles 60 and 61 are brought close to the gate 51c, and molten resin is supplied to the nozzles 60 and 61 from an unillustrated extrusion device of the injection molding machine. As a result, the molten resin is injected from the nozzles 60 and 61 into the capacity 53 through the gate 51c. At this time, there is a small amount of cold slug that has cooled and solidified from one injection to the next at the tip of the nozzle 60, 61, and this cold slug is pushed into the recess 52f, and from above it is further completely removed. The resin melted in the resin is pushed in, and the completely melted resin fills the capacity 53.

  When the resin cools and hardens, the movable mold 52 is separated from the fixed mold 51 and the resin sheet 30 is taken out from the injection mold 50. In the resin sheet 30, the axial groove 36 is formed by the axial protrusion 52d, the annular groove 37 is formed by the annular protrusion 52e, and the convex portion 38 is formed by the recess 52f. Since the cold slug remains on the convex portion 38, the material can be saved. In addition, since the cold slug is fastened at a recessed position that does not slide on the ball stud 40, the resin sheet 30 breaks when the ball stud 40 slides on the sliding surface 35 of the resin sheet 30. There is no fear of doing.

  The resin sheet thus produced is assembled into the housing 20, and the housing 20 is caulked from the state shown by the two-dot chain line in FIG. 1 to the state shown by the solid line. When the ball stud 40 tilts with respect to the housing 20, the ball head 41 slides on the sliding surface 35 that does not include the cold slug. At this time, the convex portion 38 including the cold slug and the ball head 41 are not in sliding contact.

  The present invention is not limited to these embodiments, and can of course be implemented in various modes without departing from the gist of the present invention.

  Although the embodiment described above is applied to the resin sheet of the ball joint, as another embodiment, it may be applied to a cylindrical resin sheet. In this case, a plurality of axially extending grooves are formed on the inner peripheral surface of the cylindrical resin sheet in the circumferential direction, and a protrusion for accumulating cold slug is formed at the end of one of the grooves. Grease is held in the groove, and a cylindrical rotating shaft is slidably supported on the inner peripheral surface of the resin sheet.

  Further, in the above-described embodiment, the nozzle is brought close to the capacity, but the nozzle and the capacity are slightly separated in the movable mold separating direction, and a runner is provided between the nozzle and the capacity in the movable mold separating direction. good. In this case, the gate between the runner and the capacity can be made smaller than the gate between the nozzle and the capacity, and the gate can be sufficiently cooled as much as the capacity is away from the nozzle. Therefore, the finish of the gate portion of the resin sheet is improved.

  30: Resin sheet, 36: Axial groove (groove), 50: Injection mold, 51c: Gate, 52d: Axial protrusion (protrusion), 52f: Recess, 53: Capacity, 60: Nozzle, 61: Nozzle

Claims (1)

In the injection mold, a capacity for molding the resin sheet, a gate for injecting the resin into the capacity, and a protrusion for forming a groove in the resin sheet were provided and melted from the nozzle of the injection molding machine. In a resin sheet manufacturing method in which a resin sheet with grooves is formed by injecting resin into the capacity through the gate,
The protrusion is provided on a line through which resin is injected from the gate to the capacity, and a recess is provided in the protrusion. The recess has a depth in a direction in which the resin is injected from the nozzle, and the protrusion has a depth. A method for producing a resin sheet, which has a depth that does not reach the root, and a cold slug formed at the tip of the nozzle is retained in the recess, and then the molten resin is injected into the remaining capacity.

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