JPH10166403A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine capable of setting the temp. of a molding material in an injection pot high as compared with a conventional injection molding machine without generating scorch in the molding material by preventing the remaining of plasticized rubber on the inner wall surface of an injection passage by gradually reducing the inner diameter of the injection passage toward a nozzle, especially, a preplasticizing injection machine suitable for producing a vulcanized rubber molded product. SOLUTION: An injection pot 7 having a nozzle 6 provided on one end side thereof and having the plunger 9 arranged on the other end side thereof so as to be capable of being brought into slide contact with the inner wall surface 8 of the pot 7 are provided and, in the cross section containing the axial line 19 of the injection pot 7, the angle α of inclination of the inner wall surface of the injection passage 15 to the axial line is set within a range of 0.2-θ (θ is substantially 45 deg.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, and more particularly, to a molding material which is in a plasticized state by preventing it from remaining on an inner wall surface of an injection passage upon completion of injection. The present invention relates to a prepra-type injection molding machine capable of setting the temperature of the molding material in an injection pot higher than that of a conventional injection molding machine without causing burning or the like.

[0002] This injection molding machine is particularly suitable for producing a vulcanized rubber molded product. In this case, a rubber in a plasticized state put into an injection pot (hereinafter referred to as "plasticized rubber") is used. ) Can be set higher than that of a conventional injection molding machine, and accordingly, the rubber temperature at the time of injection into the mold cavity can be increased. Vulcanization time can be greatly reduced.

[0003]

2. Description of the Related Art A conventional injection molding machine, for example, a prepra-type injection molding machine used for producing a vulcanized rubber molded product, comprises a pre-plasticizing device for converting a rubber into a plasticized state, and a plasticizing device to be introduced. And an injection device for injecting and filling the rubber into the mold cavity. The injection device has an injection passage at one end and a nozzle provided with a nozzle through the injection passage, and an injection pot at the other end. It has a plunger slidably disposed on the inner wall surface, and has a configuration in which the plasticized rubber charged into the injection pot is injected from the nozzle into the mold cavity by the forward movement of the plunger toward the nozzle. .

In such an injection molding machine, the injection molding machine is located between the injection pot 7 'and the nozzle 6' and serves as a flow path of the plasticized rubber from the injection pot 7 'to the nozzle 6' at the time of injection. The passage 15 'is generally formed to have the same diameter as shown in FIG.

In addition, in the injection molding method for producing a vulcanized rubber molded product, the vulcanization time of the plasticized rubber injected and filled in the mold cavity is shortened from the viewpoint of improving productivity and reducing product cost. Considerations have been made widely.
As means for shortening the vulcanization time, by setting the temperature of the plasticized rubber in the injection pot as high as possible,
It is useful to increase the temperature of the rubber injected into the mold cavity.

However, if the temperature of the rubber in the injection pot is set too high, scorch may occur, and the scorched rubber or the like may be mixed into the rubber injected into the mold cavity. It is not preferable because it causes a defect. Here, scorch means a state at the start stage where the vulcanization reaction starts and plasticity is lost, that is, the physical properties are changed so that molding can no longer be performed.

[0007] In addition, the production of scorched rubber and the like is more likely to occur when the rubber adhered to the inner wall surface of the injection passage or the like remains at the place for a long time, so that the production of scorched rubber or the like is suppressed. For this purpose, as shown in FIG. 6, it is useful to reduce the number of injections N required for completely switching the plasticized rubber charged in the injection pot to the newly charged plasticized rubber.

That is, it is necessary to completely inject the remaining portion of the rubber within a small number of injections and switch to a new plasticized rubber. However, if this switching property is poor and the number of injections N for switching is large, When the temperature in the pot is raised, scorch occurs. Then, as the number of injections N required for this switching is smaller, the time during which the plasticized rubber remains on the inner wall surface such as the injection passage becomes shorter, and accordingly, the time during which the plasticized rubber is overheated on the inner wall surface also increases. As a result, the production of scorched rubber or the like can be suppressed.

Therefore, in order to increase the set temperature of the rubber in the injection pot, the time during which the plasticized rubber remains on the inner wall surface such as the injection passage is shortened as much as possible until the remaining plasticized rubber is completely injected. It is desirable to reduce the number of times N of injection of.

[0010]

However, in the conventional injection molding machine as described above, since the injection passage 15 'is formed with the same diameter, when the injection is completed, the cholesterol-like plasticized rubber is formed on the inner wall of the injection passage 15'. In order to extrude the residual plasticized rubber from the injection passage 15 ', it is necessary to repeatedly perform a considerable number of injections (at least six times), and the residual plasticized rubber remains on the inner wall portion. The plasticized rubber gradually accumulates in the place with the passage of time, and the injection passage 15 ′
In such a case, even if the injection is repeated, it is not easy to push out the plasticized rubber remaining on the inner wall surface of the injection passage 15 'from the injection passage 15'. Therefore, it is necessary for the operator to remove the rubber remaining in the injection passage 15 by removing the nozzle for every certain number of injections, which undesirably results in deterioration of workability and an increase in man-hours.

Therefore, in this conventional injection molding machine, the plasticized rubber tends to remain on the inner wall surface of the injection passage 15 'and the like. Injection pot because the operator must either remove the nozzle and remove the rubber.
At present, the rubber temperature in 7 'cannot be set higher.

An object of the present invention is to prevent the plasticized rubber from remaining on the inner wall surface of the injection passage by gradually reducing the inner diameter of the injection passage toward the nozzle, thereby causing a burning or the like in the molding material. In addition, the present invention provides an injection molding machine capable of setting the molding material temperature in an injection pot higher than that of a conventional injection molding machine, particularly a prepra-type injection molding machine suitable for manufacturing a vulcanized rubber molded product. It is in.

[0013]

To achieve the above object, an injection molding machine according to the present invention has an injection passage having an injection passage at one end and a nozzle provided through the injection passage, and an injection pot having the other end. A plunger slidably disposed on the inner wall surface, and injects the plasticized molding material injected into the injection pot from the nozzle into the mold cavity by advancing the plunger toward the nozzle. An injection molding machine for filling, wherein an inner diameter of an injection passage is gradually reduced toward a nozzle, and in a cross section including an axis of an injection pot,
The inclination angle of the inner wall surface of the injection passage with respect to the axis is 0.2 °.
Θθ.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a typical injection molding machine according to the present invention.
In the figure, 1 is an injection molding machine, 2 is a screw, 3 is a pre-plasticizing device, 4 is a mold, 5 is an injection device, 6 is a nozzle, 7 is an injection pot, 9 is a plunger, and 15 is an injection passage.

An injection molding machine 1 shown in FIG.
It is a pre-plastic injection molding machine, and is composed of a pre-plasticizing device 3 and an injection device 5.

The pre-plasticizer 3 converts the compounded rubber supplied from a hopper (not shown) through the supply port 11 into a plasticized state by rotating the screw 2 or heating from the outside. It has a structure to transfer in the screw tip direction.

The injection device 5 has an injection pot 7, a nozzle 6 is provided at one end through an injection passage 15, and a plunger 9 is provided at the other end so as to be able to slide on the inner wall surface 8 of the injection pot 7. A supply passage 16 for charging the plasticized rubber in the pre-plasticizing device 3 is communicated with a position of the injection pot 7 on the side of the injection passage 15.
Is injected into the injection pot 7 through the check valve 17 and the supply passage 16, and the plasticized rubber is
By the forward movement of the plunger 9 toward the nozzle 6,
It is ejected from the nozzle 6 through the injection passage 15, passes through the sprue 12, the runner 13, and the gate 14 of the mold 4 and the cavity 10.
Is filled in.

The feature of the present invention is that, as shown in FIG. 2A, the inner diameter of the injection passage 15 is gradually reduced toward the nozzle 6 and the injection passage 15 has a cross section including the axis 19 of the injection pot 7. The angle of inclination α of the inner wall surface 15 with respect to the axis 19 is set to 0.
2 ° to θ.

FIG. 3 shows the number of injections N required to switch the molding material when the inclination angle α is changed when injection molding is performed using a compounded rubber made of natural rubber.
Is plotted.

From this figure, it can be seen that when the inclination angle α is 0.2 ° or more, the number of injections N is halved to 3 or less as compared with the number of injections N (6 or more required) of the conventional injection molding machine. You can see that

The reason why the number of injections N is reduced when the inclination angle α is 0.2 ° or more is that the inclination angle α
This is considered to be because if the temperature is set to 0.2 ° or more, the flow on the inner wall surface becomes active and at least cholesterol-like and vulcanized substances disappear. Also, since the inclination angle of the bottom of the injection pot is generally 45 °,
It is structurally difficult to set the inclination angle α to more than 45 °, and if the inclination angle α is set to more than 45 °, the inclination angle of the pot bottom is also inevitable. However, this is not preferable because rubber remains on the inner wall surface.

From the above, in the present invention, the inclination angle α is limited to the range of 0.2 to θ (θ is substantially 45 °).

When the plasticized rubber easily remains on the inner wall surface of the injection pot 7, the forward movement of the plunger 9 in the injection pot 7 when the plasticized rubber in the injection pot 7 is injected is completed. At the position, the distance L between the plunger tip portion 18 and the inner wall surface portion 8a of the injection pot 7 substantially opposed thereto is preferably 1.0 mm or less.

In addition, the plunger 9 has a tip 18
Is preferably formed in a conical shape.
The inner wall surface portion 8a of the injection pot 7 substantially facing 18
It is preferable to form the tip 17 substantially parallel to the conical surface. Specifically, in the cross section of the plunger 9 and the injection pot 7, the angle β between the conical surface 18a of the plunger tip 18 and the axis 19 of the injection pot 7 is set to 45 °, and the inner wall portion of the injection pot 7 is formed. It is preferable that the angle between 8a and the axis 19 is also the same as the angle β.

The above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims. For example, FIG. 1 shows a case where two cavities 10 are provided, but the number of cavities 10 can be increased or decreased, and a case where plasticized rubber easily remains on the inner wall surface of the supply passage 16. In order to prevent this, the inner diameter may be formed so as to gradually decrease toward the injection pot 7, as shown in FIG.

[0026]

Next, injection molding is performed by using the above-described injection molding machine (FIG. 1) according to the present invention using three types of vibration-proof rubbers A to C as molding materials. The relationship between the temperature of the rubber and the formation of scorched rubber was investigated and is described below. Rubber cushion A~C are respectively heated at 155 ° C. with vulcanization tester (Curelastometer), this time obtained vulcanization curve at (Fig. 4), conveniently T ₁₀ values of FIG. 4 when the a vulcanization degree of 10%, vulcanization time T ₁₀ at the time of the vulcanization degree 10%, one minute each, 2 minutes, a rubber having a vulcanization properties is 3 minutes. In this exam,
The rubber starts scorching when the degree of vulcanization is 10%,
A longer vulcanization time at a vulcanization degree of 10% means that a scorched rubber is less likely to be generated. Specifically, if the number of injections N required for rubber switching is assumed to be constant, the vibration-proof rubber A
The rubber rubber in the injection pot can be set higher with the vibration-proof rubber C than with the rubber. Incidentally, vulcanization time T _10, the maximum torque Fmax., When the minimum torque Fmin. To, (Fma
x.-Fmin.) x 0.1 + Fmin. In the embodiment, the inclination angle α is set to 7.9 °, and in the conventional example, the inclination angle α is set to 0 °. Table 1 shows that, for each of the anti-vibration rubbers A to C, the temperature of the rubber charged into the injection pot was changed within the range of 80 to 125 ° C., and only the maximum temperature when the temperature range in which scorch did not occur was measured. It is shown.

[0027]

[Table 1]

From the results shown in Table 1, in each case of the vibration isolating rubbers A to C, in the embodiment, the temperature of the rubber charged into the injection pot is set higher by 15 to 25 ° C. than in the conventional example. I was able to. In addition, when the vulcanization time of the rubber injected and filled into the mold cavity was also measured, the vulcanization time of all rubbers A to C was 6 minutes or more in the conventional example. In each case, the vulcanization time was 3 minutes or less.

[0029]

According to the present invention, it is possible to provide a pre-plastic injection molding machine in which the temperature of the molding material in the injection pot can be set higher than that of a conventional injection molding machine without causing the molding material to be burned. It became. In particular, if this injection molding machine is used for the production of vulcanized rubber molded products, the temperature of the plasticized rubber put into the injection pot can be set higher than that of the conventional injection molding machine, As a result, the rubber temperature at the time of injection into the mold cavity can be increased, so that the vulcanization time of the rubber in the mold cavity can be significantly reduced, and the productivity and product cost are greatly reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for illustrating a structure of an injection molding machine according to the present invention.

2 (a) is an enlarged view of a main part mainly showing an injection passage 15 of FIG. 1, and FIG. 2 (b) is a view showing another modification.

FIG. 3 is a diagram in which the number of injections N required for rubber switching is plotted against the inclination angle α of the inner wall surface of the injection passage 15 with respect to the axis 19;

FIG. 4 is a diagram showing an example of a vulcanization curve when a relationship between torque and vulcanization time is measured using a curast meter.

FIG. 5 is a diagram for explaining the number of injections N required for rubber switching.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Injection molding machine 2 Screw 3 Pre-plasticizer 4 Mold 5 Injection device 6 Nozzle 7 Injection pot 8 Inner wall of injection pot 7 Plunger 10 Cavity of mold 4 11 Supply port 12 Sprue 13 Runner 14 Gate 15 Injection passage 16 Supply passage 17 Check valve 18 Tip of plunger 9 19 Injection pot 7 (or plunger 9) axis 20 Gap 21 Residual rubber

Claims (1)

[Claims] 1. An injection pot having an injection passage on one end side and a nozzle provided through the injection passage, and a plunger disposed on the other end side so as to be slidably in contact with the inner wall surface. The molding material in the plasticized state put in the pot,
In an injection molding machine that injects and fills a mold cavity from a nozzle by a forward movement of a plunger toward a nozzle, an inner diameter of the injection passage is gradually reduced toward the nozzle, and a cross section including an axis of the injection pot has a cross section of the injection passage. An injection molding machine, wherein an inclination angle of an inner wall surface with respect to the axis is in a range of 0.2 ° to θ.