JP2001170976A - Mold device for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mold device for injection molding which can mold even a large-diameter difference molding member having an undercut part. SOLUTION: A pinch angle θ made by two slide surfaces 10b contacting a center core 1 with the slide surface 10a of the guide means of the first slide core 2 pinched is set up within a range of 120-180 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die apparatus used for producing a plastic member having an undercut such as a screw on the inner surface by injection molding.
In particular, the present invention relates to one having a large diameter difference on the inner surface.

[0002]

2. Description of the Related Art Conventionally, when a plastic member having an undercut portion such as a screw or a cam groove on an inner peripheral surface is manufactured by injection molding, a slide core is widely used in an injection molding die apparatus. . The slide core is formed of a plurality of divided cores, the core forming a molded part together with a center core, and by moving the divided slide core in the center direction of the molded product when releasing the molded product, It can be separated from the undercut.

As means for guiding the movement of the slide core as described above, there are a guide pin and a guide hole, and a dovetail and a dovetail groove. FIG. 3 is a plan view showing a typical structure of such a six-part slide core, and FIG. 2 is a cross-sectional view when the core is used in an injection mold. This core is composed of a center core 31 and first slide cores 3 divided around the center core 31 and arranged alternately.
2 and the second slide core 33, between the center core 31 and the first slide core 32 and between the center core 31 and the second slide core 33, α degrees and β degrees (normally 2 degrees).
(α or more), and the center core 31 is moved downward to bring the first slide core 32 and the second slide core 33 closer to the center.

A dovetail / dovetail engagement is used as a slide guide, and a dovetail groove is provided at the center of the sliding surface of the center core 31 with the first slide core 32 and the second slide core 33, and the first slide is provided. Ants are provided at the center of the sliding surface of the core 32 with the center core 31 and at the center of the sliding surface of the second slide core 33 with the center core 31, respectively.

[0005]

In the conventional slide core as described above, a molded member having an undercut portion and a plurality of inner peripheral surfaces having different diameters (hereinafter, referred to as a molded member having a diameter difference) will be described. In this case, if the diameter difference is too large, the sliding surfaces of the first slide cores are too close to each other on the outer periphery, so that the first slide core cannot slide, or the thickness of the first slide core is reduced. Since the thickness is reduced, the strength of the core cannot be secured, and there is a problem that the slide core cannot be mounted and molded on the injection molding die apparatus.

Accordingly, an object of the present invention is to provide an injection molding die apparatus capable of molding a molded member having a large difference in diameter.

[0007]

According to the first aspect of the present invention, there is provided an injection molding apparatus having a slide core and a center core in order to form a molded member having an undercut. In the molding die apparatus, the slide cores include three first slide cores and three second slide cores alternately arranged around the center core, and the center core, the first slide core, and the center core A guide means for guiding and sliding along the direction in which the mold is opened is provided at substantially the center of each sliding surface of the first slide core and the second slide core between the first and second slide cores. The angle between the two sliding surfaces where the first slide core contacts the center core with the guide means interposed therebetween is larger than 120 degrees and smaller than 180 degrees, preferably 13 degrees. Less than greater 170 degrees than degrees, more preferably it is characterized by smaller than 170 degrees greater than 155 degrees.

According to a second aspect of the present invention, in the injection molding die apparatus according to the first aspect, the slide core and the center core of the molding portion are provided on the movable mold. According to a third aspect of the present invention, in the injection molding die apparatus according to the first aspect, the slide core and the center core of the molding portion are provided on the fixed mold.

According to a fourth aspect of the present invention, in the injection mold apparatus of any one of the first to third aspects, the guide means is a dovetail and a dovetail groove. Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. Here, in order to clarify an embodiment of the present invention, a description will be given in comparison with a conventional example. FIG. 2 is a cross-sectional view of an injection molding die apparatus for molding a molding member 50 having a diameter difference. The injection molding die apparatus according to the present invention has the same configuration as the conventional one, but differs in the shape of the slide core. First, the configuration of the mold apparatus will be described.

The present apparatus is composed of a fixed type above the parting line and a movable type below the parting line. The fixed-side mold includes a fixed-side mounting plate 11 and a fixed-side mold plate 12,
The movable type includes a movable mounting plate 21 and a movable receiving plate 22.
, The movable mold plate 23, the slide cores 32 and 33, and the center core 31. Here, the core is the center core 31
And a first slide core 32 and a second slide core 33 alternately arranged around the center core 31. FIG. 3 is a plan view of a core used in a conventional injection mold apparatus, and FIG. 1 is a plan view of a core used in an injection mold apparatus according to the present invention. FIG.
3 is a partially enlarged view of FIG.

Here, the radius of the small-diameter portion of the slide core for forming the inner peripheral surface is r, the radius of the large-diameter portion is R, the step between the surfaces of the small-diameter portion and the large-diameter portion is D, and from the center of the molded member to the dovetail. Is h on the small diameter surface and H on the large diameter surface. Also, the amount of sliding of the first slide core in the horizontal direction is set to S. In the slide core used in the conventional injection molding die apparatus shown in FIG. 3, the minimum distance n between the sliding surfaces 30b of the adjacent first slide cores 32 on the small diameter surface and the minimum distance N on the large diameter surface. Is equal to (1) so that H does not become 0 in each case.
Needs to satisfy the expression (2).

H> r / 2 + S (1) H> R / 2 + S (2) Further, from FIG. 4, H = h + D · tanα.
Equation (2) becomes equation (3). h> R / 2 + SD-tanα (3) On the other hand, in order to secure the mold strength, the slide core needs to have a certain thickness or more, and the thickness E is (4)
It is expressed by an equation.

E = r−H = r−h−D · tan α (4) Here, since the minimum dimension E generally needs to be 2 mm or more from empirical rules, the expression (4) is replaced by the expression (5). Becomes r−h−D · tanα ≧ 2 r−2−D · tanα ≧ h (5) Further, if the large / small diameter ratio K is set to K = R / r (K> 1), the following equation (3) is obtained. The relational expression (6) between K and r is obtained from the expression (5). That is, r-2-D · tan α ≧ h> R / 2 + SD · tan α r-2-D · tan α> K · r / 2 + SD−tan α 2- (4 + 2S) / r> K (6) Here, when the commonly used 2 mm is substituted into the equation (6) as the slide amount S, the equation (7) is obtained.
1 <K <2.

K <2-8 / r (7) This is shown by a graph in the hatched area B in FIG. It can be seen that the conventional slide core can cope with the diameter ratio relationship of the B region, but cannot cope with the region outside the B region. Next, in the slide core used in the injection molding die apparatus according to the present invention shown in FIG. 1, two sliding surfaces 10 b contacting the center core 1 with the sliding surface 10 a of the guide means of the first slide core 2 interposed therebetween. The included angle is θ degrees, and the end of the first slide core 2 on the large-diameter surface is point P (X, Y).

Here, considering the point P when the radius R of the large diameter portion takes the maximum value, it is necessary to satisfy the expression (8) in order to secure the sliding amount of the first slide core. Y = X · tan30 ° + S (8) Also, in order to secure the mold strength of the first slide core,
It is necessary that the thickness of the core is at least 2 mm to satisfy the expression (9).

Y = X · tan [(180 ° −θ) / 2] + r−2 (9) Further, the X coordinate of the point P is approximately represented by the following equation (10). X ≒ R · cos30 ° = K · r · cos30 ° (10) Accordingly, the relational expression (11) between K and r is obtained from the expressions (8), (9) and (10).

K · r · cos30 ° · tan30 ° + S = K · r · cos30 ° · tan [(180 ° −θ) / 2] + r−2 K · r · cos30 ° (tan30 ° −tan [(180 ° −θ) / 2]) = r−2−S K = (r−2−S) / (r · cos30 ° {tan30 ° −tan [(180 ° −θ) / 2]}) = {(− 2) −S) / (cos30 ° · {tan30 ° −tan [(180 ° −θ) / 2]})} · 1 / r + 1 / (cos30 ° · {tan30 ° −tan [(180 ° −θ) / 2 ]}) (11) FIG. 5 shows a graph when the sliding amount: S = 2 mm in equation (11) and θ is changed to 170, 160, 150, and 140 degrees. As is apparent from this figure, when the included angle: θ is set to 170 degrees in the core of the present invention, it is possible to cope with the enlarged area A from the corresponding area B in the related art. (First Embodiment of the Invention) FIG. 1 shows an injection molding die apparatus according to the present invention, in which a molding portion has slide cores 2, 3 and a center core 1 for molding a molded member having an undercut portion. It is a schematic plan view showing an embodiment.
Since the structure of the device is as described above, description thereof will be omitted. Using the mold apparatus as described above, the radius of the small diameter portion: r = 21.65 mm, the radius of the large diameter portion: R = 36 mm, the step between the surfaces of the small diameter portion and the large diameter portion: D = 9.5 mm K (diameter) A molded article having a shape of (ratio coefficient) = 1.66 (= 36 / 21.65) was obtained by sandwiching the sliding surface of the first slide core 2 at an angle of θ = 170 ° and sliding amount of the slide core: S = 3.06 mm. Molded with a mold device. The molding material was a polycarbonate resin filled with 20% glass fiber.

As calculated from the equation (6), the molded article having this shape is expressed as follows: 2- (4 + 2.3.06) /2.65> R / 21.6
5 Therefore, R <33.18, and a member having a large diameter portion with a radius of 36 mm could not be formed by the conventional method.

However, according to the present invention, as calculated from equation (11), K = (21.65-2-3.06) / (21.65 · co.
s30 ° {tan30 ° -tan [(180 ° -170 °) / 2]}) = 1.81 Therefore, it is possible to cope with the case where R = 39.19 and the radius of the large diameter portion is 36 mm, and a plastic part is formed. I was able to.

[0021]

As described above, according to the present invention, the included angle θ between the two sliding surfaces in contact with the center core of the first slide core is set within a range of more than 120 degrees and 170 degrees or less. Thus, it is possible to mold even a molded member having a large diameter difference having an undercut portion, which cannot be handled by the conventional injection molding die apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a slide core used in an injection molding die apparatus according to the present invention.

FIG. 2 is a cross-sectional view of an injection molding die apparatus for molding a molding member having a diameter difference.

FIG. 3 is a schematic plan view of a slide core used in a conventional injection molding die apparatus.

FIG. 4 is a partially enlarged sectional view of FIG. 2;

FIG. 5 is a graph showing a relationship between a radius of a small diameter portion, a large diameter portion, and a small diameter portion of a slide core used in an injection mold device according to the present invention and a slide core used in a conventional injection mold device. It is a figure which shows the relationship of a ratio.

[Explanation of symbols]

 1, 31: Center core 2, 32: First slide core 3, 33: Second slide core 10a, 30a: Sliding surface of guide means 10b, 30b: Sliding surface 11. ..Fixed-side mounting plate 12 ... Fixed-side mold plate 21 ... Movable-side mounting plate 22 ... Movable-side receiving plate 23 ... Movable-side mold plate

Claims (4)

[Claims] 1. An injection molding apparatus in which a molding portion has a slide core and a center core for molding a molding member having an undercut portion, wherein the slide cores are alternately arranged around the center core. A guide comprising three first slide cores and three second slide cores, and a guide that slides between the center core and the first slide core and between the center core and the second slide core in a mold opening direction. Means are provided at substantially the center portions of the respective sliding surfaces of the first slide core and the second slide core so as to be engaged with each other, so that the first slide core is in contact with the center core across the guide means. 120 pinch angle
A mold device for injection molding, wherein the temperature is greater than 180 ° and less than 180 °, preferably greater than 130 ° and 170 ° or less, more preferably greater than 155 ° and 170 ° or less. 2. The injection molding die apparatus according to claim 1, wherein a slide core and a center core of the molding part are provided on the movable die. 3. The injection molding die apparatus according to claim 1, wherein the slide core and the center core of the molding part are provided on a fixed side die. 4. The injection molding die apparatus according to claim 1, wherein said guide means is a dovetail and a dovetail groove.