JP3757816B2 - Injection molding equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding apparatus and an injection molding method for controlling an increase in temperature by controlling the supply of resin to a valve gate and performing injection molding without defects such as stringing.
[0002]
[Prior art]
A conventional hot runner type injection molding apparatus 1 'is shown in FIG. The injection molding apparatus 1 ′ includes a mold, a mold clamping device, an injection device, a drive source, and a control device. The molten resin supplied from an injection device (a hopper, an injection plunger, etc.) not shown in the drawing is used for the hot runner block 9. The molten resin is conveyed to the gate through the runner 10 and injected into the cavity according to the opening and closing of the gate. When a predetermined amount of molten resin is injected, the valve pin 11 closes the valve gate 4 at an appropriate timing during injection or after completion of the pressure holding process, and a molded product is obtained after cooling.
[0003]
The gate opening / closing method includes a heating control method using a spear tip extending into the gate or a valve gate method for mechanically opening and closing the gate. In the injection molding apparatus 1 ′ shown in FIG. The method is adopted.
[0004]
[Problems to be solved by the invention]
However, as shown in FIG. 7, the nozzle diameter of the tip portion of the nozzle flow path 6 is smaller than the nozzle diameter of the general portion of the nozzle flow path 6, so that when the molten resin passes through the narrowed portion of this flow path. As the pressure increases, the temperature in the vicinity of the valve gate 4 increases significantly. In particular, in the apparatus for molding a large molded product (bumper or the like) having a plurality of gate nozzles 61 shown in FIG. When only the gate is closed, the resin further flows into the tip of the flow path 6 of the nozzle where the gate is open, so that the pressure further increases and the temperature in the vicinity of the valve gate 4 becomes higher. In this way, if the mold is opened with the temperature near the valve gate 4 being high, a yarn drawing phenomenon occurs between the molded product and the gate chip 5, and if this yarn adheres to the molded product, the appearance quality of the product is degraded. There was a problem of inviting.
[0005]
Further, regarding this problem, there is a technique disclosed in Japanese Patent Laid-Open No. 5-177664 as a prior art for the purpose of controlling the temperature of the gate part. This technique forms an air heat insulation layer in the valve gate 4 part to insulate it. The problem that the temperature in the vicinity of the valve gate 4 becomes high has not been solved yet.
[0006]
The present invention has been made in view of such problems of the prior art, and provides an injection molding apparatus and an injection molding method in which the temperature rise at the nozzle tip is suppressed by controlling the resin supply to the valve gate. The purpose is to do.
[0007]
[Means for Solving the Problems]
(1) In order to achieve the above object, according to the present invention , a nozzle that injects a molten resin toward the inside of a cavity formed by a relatively approaching mold, and a molten resin toward the tip of the nozzle An injection molding apparatus having a runner for guiding, a first valve for opening and closing a nozzle tip, and a second valve for controlling a flow rate of a molten resin provided upstream of the first valve and guided toward the nozzle Is provided. In this invention, the second valve may fully open or fully close the runner flow path .
Furthermore, in order to achieve the above object, according to the present invention , a predetermined amount of molten resin is fed via a nozzle toward the inside of a cavity formed by a mold that is relatively approached by feeding molten resin via a runner. An injection molding method is provided in which the flow rate of the molten resin fed to the tip of the nozzle is controlled before and after the end of injection, and the injection port of the nozzle is closed.
[0008]
In the present invention, in addition to the first valve that opens and closes the nozzle tip, a second valve that controls the flow rate of the flow path of the nozzle is provided upstream of the first valve (resin supply source side). The second valve controls the flow rate of the molten resin supplied toward the nozzle tip (first valve) on the upstream side of the nozzle flow path. In the present invention, controlling the flow rate of the flow path of the nozzle means changing the flow rate of the molten resin guided by the runner at the second valve, that is, a part or all of the supplied molten resin. Sending to the tip of the nozzle. Specifically, the second valve controls the flow rate of the nozzle flow path by damming part or all of the nozzle flow path or opening and closing part or all of the nozzle flow path.
[0009]
With such a configuration, without providing new cooling means, the pressure applied to the nozzle tip is reduced by controlling the flow rate of the molten resin flowing into the nozzle tip during injection, thereby suppressing the temperature rise at the nozzle tip. Thus, there can be provided an injection molding apparatus for producing a resin molded product having a high appearance quality without causing any trouble such as stringing when the mold is opened. In particular, at the end of injection when the nozzle tip is closed and the resin pressure at the nozzle tip is increased, the temperature rise at the nozzle tip can be effectively suppressed.
[0010]
(2) In the above invention, according to the present invention , the valve includes a valve pin that is inserted into the flow path of the nozzle and opens and closes the tip of the nozzle by reciprocation along the insertion direction, and the first valve has a small diameter portion at the tip of the valve pin. Thus, the second valve is provided with an injection molding device having a large diameter portion on the proximal end side of the valve pin. In the present invention, the size and shape of the small diameter portion and the large diameter portion are not limited as long as the nozzle tip can be opened and closed, and the base end side of the valve pin on which the large diameter portion is provided is the two end portions of the valve pin. Of these, the side that is not the injection side is said, and its position is not limited.
[0011]
In the present invention, the second valve receives the molten resin in the region formed between the first valve and the second valve, and causes the received molten resin to flow to a runner other than the region. It is preferable to have. In addition, the relief portion is preferably a gap between the second valve and the nozzle formed by making the second valve thinner than the inner diameter of the flow path of the nozzle with which the second valve contacts. Moreover, it is preferable that this relief part is a groove | channel provided in the outer peripheral surface of a 2nd valve | bulb. This is because when the large-diameter portion that is the second valve is operated to control the flow rate of the nozzle flow path, the resin on the nozzle tip side may be pressed. In such a situation, the relief portion that receives the molten resin is provided. This is because by providing the second valve (large-diameter portion), it is possible to release the resin pressure newly generated when controlling the flow rate and prevent the pressure applied to the nozzle tip from being generated.
[0012]
In this invention, a valve pin is inserted into the flow path of the nozzle, and the reciprocating motion causes the small diameter portion at the tip of the valve pin to open and close the nozzle tip, and the large diameter portion on the base end side of the valve pin corresponds to the position of the nozzle. The flow rate of the molten resin is controlled by narrowing the contact area of the road or by fully closing or fully opening the road. At this time, since the position of the large diameter portion is interlocked with the movement of the valve pin, the flow control by the large diameter portion is related to the opening and closing of the nozzle tip by the small diameter portion. That is, the opening / closing timing of the first valve and the opening / closing timing of the second valve can be adjusted by the positional relationship between the first valve (small diameter portion) and the second valve (large diameter portion). By adjusting the position, the second valve can be closed before or simultaneously with the first valve, and the amount of resin to be accommodated between the first valve and the second valve is kept constant. be able to.
[0013]
Thereby, without providing a new cooling device or the like, the same effect as the above-described invention is achieved, the temperature rise at the tip of the nozzle is suppressed, there is no possibility of causing problems such as string drawing at the time of mold opening, and the appearance quality is high. An injection molding apparatus for producing a resin molded product can be provided.
[0014]
(3) In order to achieve the above object, according to the present invention, there is provided an injection molding apparatus having a control unit that controls the operation timing of the second valve according to the timing at which the first valve opens and closes the nozzle tip. Provided.
[0015]
In the above invention, since the second valve is provided upstream of the first valve, a sealable space is formed between them. In order to keep the pressure applied to the first valve constant by making the amount of the molten resin accommodated between the first valve and the second valve constant, the control unit Is controlled according to the opening / closing timing of the first valve.
[0016]
The opening / closing timing of the second valve relative to the opening / closing timing of the first valve is set as appropriate according to the physical properties of the molten resin, the melting temperature, and the injection conditions, but before or simultaneously with the closing of the first valve. It is preferable to close the second valve. Because, according to such control, the amount and pressure of the resin to be accommodated between the first valve and the second valve can be kept constant, and the temperature at the nozzle tip can be made constant. In addition, when the first valve is closed for a considerable period of time, it is preferable to perform the above control because the molten resin will flow in and increase the pressure at the tip of the nozzle.
[0017]
(4) In order to achieve the above object, according to the present invention , there is provided an injection molding apparatus in which a plurality of nozzles are provided in one runner.
[0018]
In the present invention, a plurality of nozzles are provided in one cavity, and the plurality of nozzles receive a supply of molten resin from one runner or runners communicating with each other. In general, since the opening and closing of a plurality of nozzles are controlled independently, injection may be performed with some of the plurality of nozzles closed and other nozzles open. At this time, the molten resin fed from the common runner is concentrated on the nozzle with the gate open, and the pressure at the tip of the nozzle is remarkably increased. Therefore, according to the present invention, there is provided an injection molding apparatus for producing a resin molded product having a high appearance quality, which suppresses an increase in pressure at the tip of each nozzle and thus a temperature increase, does not cause a problem such as string drawing at the time of mold opening. Can be provided.
[0019]
【The invention's effect】
According to the present invention , the flow rate of the molten resin flowing into the nozzle tip during injection is controlled to reduce the pressure applied to the nozzle tip, to suppress the temperature rise at the nozzle tip, and troubles such as string drawing when the mold is opened It is possible to provide an injection molding apparatus for producing a resin molded product having a high appearance quality. In particular, the temperature rise at the nozzle tip can be effectively suppressed at the end of the injection when the resin pressure at the nozzle tip is increased, or when a part of the nozzles performs injection.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3, the state of the injection molding apparatus 1 according to the present embodiment at the time of injection of the molten resin (FIG. 1), the state immediately before the injection of the molten resin is stopped (FIG. 2), the time of the injection stop of the molten resin ( FIG. 4 is a diagram showing a state of FIG. 3, FIG. 4 is a diagram showing a first example of the second valve (large diameter portion) 11b, and FIG. 5 is a second example of the second valve (large diameter portion) 11b. FIGS. 6A to 6B are views for explaining the relief portion 11c provided in the large diameter portion 11b.
[0021]
The injection molding apparatus 1 according to this embodiment includes a hopper, an injection cylinder, a plunger, a nozzle, and the like that have functions of plasticizing, weighing, and injecting resin. In FIGS. 1 to 3, a gate nozzle 61 having an injection function is provided. Is shown as the center.
[0022]
First, the overall configuration of the injection molding apparatus 1 according to the present embodiment will be described with reference to FIG. 1. The injection molding apparatus 1 according to the present embodiment includes at least a runner 10 for guiding a molten resin, and a communication with the runner 10. A fixed nozzle 22 in which the gate nozzle 61 is fitted, and a movable mold 21 that forms a cavity 3 in pairs with the fixed mold 22. By sealing the pair of movable mold 21 and fixed mold 22, a cavity 3 that can be sealed is formed between them. In this example, since the rigid injection molding apparatus 1 is used and the fixed mold 22 into which the gate nozzle 61 is fitted is fixed, the movable mold 21 is moved up and down with respect to the fixed mold 22 by a mold clamping device (not shown). . Of course, the mold 2 may be a horizontal mold, and the fixed mold 22 may be moved with respect to the movable mold 21. Incidentally, the cavity 3 shown in FIG. 1 is plate-shaped, but is actually shaped according to the shape of a molded product such as the body of an automobile.
[0023]
A plurality of valve gates 4 are formed in the fixed mold 22 that forms the cavity 3, and molten resin supplied from a hopper, a heating cylinder, etc. (not shown) is filled into the cavity 3 through the fixed gate 22. The molten resin is guided to the valve gate 4 by a runner 10 provided in the hot runner block 9. The runner 10 communicates with the flow path 6 of the nozzle and feeds an amount of resin necessary for injection.
[0024]
The gate nozzle 61 for injecting the molten resin is embedded in a fixed mold with the valve gate 4 at the tip of the gate nozzle 61 facing the opening of the cavity 3. A flow path 6 is disposed, and a valve pin 11 is inserted in the center of the flow path 6 of the nozzle. The valve pin 11 reciprocates within the range of the pin stroke q shown in FIG. 1, and the valve gate 4 is opened and closed by this reciprocation. The valve pin 11 is driven by compressed air fed from the cylinder 13. . Note that the length of the pin stroke q is slightly longer than the diameter of the nozzle channel 6 in order to ensure the fully closed state of the channel.
[0025]
By the way, in this injection molding apparatus 1, as shown in FIG. 1, since the tip of the nozzle flow path 6 is formed thinner than the general part, molten resin becomes narrower in the nozzle flow path 6 at the time of injection. Increase the pressure by concentrating on the part. In particular, the pressure at the tip of the nozzle flow path 6 immediately after each valve gate 4 is closed rises remarkably, and the temperatures of the tip valve gate 4 and the gate chip 5 in the nozzle flow path 6 rise excessively. Such a temperature rise naturally occurs not only in the case of the single gate nozzle 61 shown here, but also in the injection molding apparatus 1 in which a plurality of gate nozzles 61 are embedded in the fixed mold 22. When the gate nozzles 4 of some of the gate nozzles 61 perform injection and the gate nozzles 4 of some of the gate nozzles 61 are controlled to be closed, a part of the opened valve gates Since the resin concentrates on 4 and the pressure of the valve gate 4 becomes higher, it can be said that there is a particularly high demand for suppression of temperature rise. The single injection molding apparatus 1 shown in FIGS. It can also be used for the injection molding apparatus 1 having a plurality of 61 (see FIG. 8).
[0026]
Next, the second valve provided specifically in the present embodiment will be described. In the present embodiment, the portion where the valve pin 11 is configured to be thick on the proximal end side of the valve pin 11, that is, the large diameter portion 11b is used as the second valve, and the relatively thin portion small diameter portion 11a at the tip portion of the valve pin 11 is used as the first valve. did. The large diameter portion 11 b controls the flow rate of the molten resin supplied toward the tip of the nozzle flow path 6 on the upstream side of the nozzle flow path 6. In this invention, controlling the flow rate of the flow path 6 of the nozzle means changing the flow rate of the molten resin guided by the runner 10 with the large diameter portion 11b as a boundary, that is, a part of the supplied molten resin or It means sending all to the tip of the flow path 6 of the nozzle. By controlling the flow rate of the molten resin fed to the tip of the nozzle flow path 6 by the large diameter portion 11b, the pressure rise applied to the tip of the nozzle flow path 6, that is, the small diameter portion 11a is suppressed. Suppresses the rise. Although the form of the large diameter part 11b is not particularly limited, the large diameter part 11b of this embodiment is a part of the valve pin 11 that is thick and integrated, but a cylindrical or ring-shaped member is coaxial with the valve pin 11 It may be pivotally supported and its shape is not limited. In this embodiment, the nozzle flow path 6 and the runner 10 are in contact with each other in a substantially T-shape, but the nozzle flow path 6 and the runner 10 are not limited to such a configuration and are in contact with each other. can do.
[0027]
The operation of the small diameter portion 11a and the large diameter portion 11b will be described with reference to FIGS. These are views showing a state when the molten resin is injected (FIG. 1), a state immediately before the injection of the molten resin is stopped (FIG. 2), and a state when the injection of the molten resin is stopped (FIG. 3). The position of the small-diameter portion 11a in the portion and the large-diameter portion 11b on the proximal end side of the valve pin 1 will be described. At the time of injection shown in FIG. 11a opens the valve gate 4, and the large-diameter portion 11b opens a communication path between the runner 10 and the nozzle flow path 6. In this state, the molten resin reaches the gate nozzle 4 and is injected toward the cavity 3.
[0028]
Subsequently, before the injection stop shown in FIG. 2, the valve pin 11 approaches the valve gate 4, the small diameter portion 11 a is positioned immediately before closing the valve gate 4, and the large diameter portion 11 b is the flow between the runner 10 and the nozzle. Immediately before closing the communication path with the road 6. In this state, the molten resin is blocked by the large-diameter portion 11b, and no new molten resin is sent between the large-diameter portion 11b and the small-diameter portion 11a, and the pressure in this portion is increased. Absent. As a result, the temperature rise at the tip of the nozzle flow path 6 can be suppressed, and resin leakage from the joints between the members can be prevented.
[0029]
Thus, the large diameter portion 11b reciprocates with the valve pin 11 provided on the central axis of the nozzle flow path 6, and the nozzle flow path 6 and the runner 10 according to the position of the large diameter portion 11b of the reciprocation. The flow rate of the molten resin flowing into the tip of the nozzle channel 6 is controlled by narrowing or fully closing the communication channel. At this time, the position of the large diameter portion 11b is interlocked with the movement of the valve pin 11, and the control of the flow rate by the large diameter portion 11b is related to the movement of the small diameter portion 11a, that is, the opening and closing of the valve gate 4. Thereby, the opening / closing timing of the first valve and the opening / closing timing of the second valve can be adjusted by the positional relationship (distance) between the small diameter portion 11a and the large diameter portion 11b. If this position adjustment is performed, the large-diameter portion 11b can control the flow rate of the nozzle flow path 6 before or almost simultaneously with closing the valve gate 4 described in FIG. 2, and the small-diameter portion 11a and the large-diameter portion 11b It is possible to keep the amount of resin, the pressure, and thus the temperature held constant between the two. On the contrary, when the valve gate 4 is closed first, after the valve gate 4 is closed, the molten resin flows into the front end side of the nozzle flow path 6 to increase the pressure, and the pressure at the front end of the nozzle flow path 6 is increased. The temperature will rise. In the present embodiment, the opening / closing timing of the first valve and the second valve according to the present invention is controlled in the positional relationship between the small diameter portion 11a and the large diameter portion 11b, but of course, a control unit that controls these timings. 15 may be provided to control the opening / closing timing by an electric signal or the like. The opening / closing timing of the large-diameter portion 11b with respect to the opening / closing timing of the small-diameter portion 11a is preferably set as appropriate according to the physical properties of the molten resin, the melting temperature, and the injection conditions.
[0030]
When the injection is stopped as shown in FIG. 3, the small diameter portion 11a fully closes the valve gate 4, and the large diameter portion 11b fully closes the communication path between the runner 10 and the nozzle flow path 6. As a result, the region of the nozzle flow path 6 formed between the small diameter part 11a and the large diameter part 11b is closed, and the pressure at the tip of the nozzle flow path 6 is increased without supplying new molten resin. Does not occur. Here, looking at the relationship between the large-diameter portion 11b and the nozzle flow path 6 in FIG. 3, the large-diameter portion 11b exceeds the contact area between the runner 10 and the nozzle flow path 6 by a compression amount r. The flow passage 6 is inserted, and the inserted portion compresses the molten resin in the flow passage 6 of the nozzle.
[0031]
On the other hand, in this embodiment, the relief part 11c which receives molten resin in the large diameter part 11b was provided. An example of the large diameter portion 11b having the relief portion 11c provided in particular is shown in FIGS. The relief portion 11c shown in FIG. 4 is configured by a gap in which the diameter (bb) in the large diameter portion 11b is slightly narrower than the diameter of the nozzle flow path 6 (aa), and the small diameter portion 11a. And the large diameter portion 11b is allowed to flow to another region communicating with the flow path 6 of the nozzle such as the runner 10 to release the pressure applied by the large diameter portion 11b. Further, the relief portion 11c shown in FIG. 5 is constituted by a groove formed in the large diameter portion 11b, and accepts a molten resin between the small diameter portion 11a and the large diameter portion 11b, and similarly the large diameter portion 11b. Relieve the pressure applied.
[0032]
Examples of the specific shape of the relief portion 11c constituted by the gaps and grooves are shown in FIGS. 6 (a), 6 (b), and 6 (c). In the relief portion 11c shown in FIG. 6 (a), a gap is formed by making the diameter of the large diameter portion 11b smaller than the diameter of the flow path 6 of the nozzle, and the width t1 of the gap is about 1 mm or less. . The relief portion 11c shown in FIGS. 6B and 6C forms a groove in the large diameter portion 11b, and the depth of the groove indicated by t2 in FIG. 6B or the relief portion 11c in FIG. The width of the groove indicated by t3 was also about 1 mm or less. The reason why the thickness is 1 mm or less is that if it is 1 mm or more, a new molten resin flows in from this gap and presses the tip of the flow path 6 of the nozzle. After the resin cannot pass through the gap or groove and the large-diameter portion 11b (second gate) narrows the nozzle flow path 6, there is no possibility that further pressure is applied to the tip of the nozzle flow path 6, and the other side. Since the volume of the large-diameter portion 11b that fits into the nozzle flow path 6 (the product of the compression allowance r multiplied by the nozzle cross-sectional area) is not so large, a gap or groove of 1 mm or less can be accepted. Because it is. Thus, the relief part 11c can prevent a new temperature rise caused by the operation of the large diameter part 11b, and can strictly manage the temperature of the tip of the nozzle flow path 6.
[0033]
As described above, the injection molding apparatus 1 according to the present embodiment controls the flow rate of the molten resin flowing into the tip of the nozzle flow path 6 at the time of injection without providing a new cooling device or the like. The pressure applied to the tip of the nozzle 6 is reduced, and the temperature rise at the tip of the nozzle flow path 6 is suppressed. In particular, in the injection molding apparatus 1 that employs the elongated valve pin 11, it is difficult to embed a heater or add a cooling hole from the viewpoint of space and machining, but in this embodiment, without providing such equipment, The injection molding apparatus 1 for producing a resin molded product having a high appearance quality can be provided without causing a problem such as string drawing when the mold is opened. In particular, at the end of injection when the resin pressure at the tip of the nozzle flow path 6 increases, or when some of the nozzles 61 perform injection, the temperature rise at the tip of the nozzle flow path 6 is effectively suppressed. can do.
[0034]
Further, in the injection molding apparatus 1 for a large molded article in which a plurality of gate nozzles 61 are provided in one runner, the molten resin concentrates on the open valve gate 4 among the plurality of valve gates 4, and the pressure and temperature are particularly high. Although it rises remarkably, by controlling the flow rate of the molten resin by the first valve 11a and the second valve 11b particularly provided in this embodiment, the pressure and temperature rise at the tip of the nozzle flow path 6 are effectively suppressed. The injection molding apparatus 1 for producing a resin molded product with high appearance quality can be provided.
[0035]
The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element and each numerical value disclosed in the above embodiment are intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a view showing a state at the time of injection of molten resin in an injection molding apparatus according to the present embodiment.
FIG. 2 is a diagram showing a state immediately before stopping injection of molten resin in the injection molding apparatus according to the present embodiment.
FIG. 3 is a view showing a state of the injection molding apparatus according to the present embodiment when the injection of molten resin is stopped.
FIG. 4 is a diagram showing a first example of a second valve (large diameter portion) according to the present embodiment.
FIG. 5 is a view showing a second example of a second valve (large diameter portion) according to the present embodiment.
FIGS. 6A to 6B are diagrams showing examples of a relief portion having a large diameter portion.
FIG. 7 is a view showing a conventional injection molding apparatus.
FIG. 8 is a view showing an injection molding apparatus having a plurality of conventional nozzles.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 1 '... Injection molding apparatus 2 ... Type | mold 21 ... Movable type | mold 22 ... Fixed type | mold 3 ... Cavity 4 ... Valve gate 5 ... Gate chip 6 ... Nozzle flow path 61 ... Gate nozzle 7 ... Thermal insulation ring 8 ... Color 9 ... Hot Runner block 10 ... Runner 11 ... Bubble pin 11a ... Small diameter part, first valve 11b ... Large diameter part, second valve 11c ... Relief part 12 ... Bubble pin bush 13 ... Cylinder 14 ... Heater 15 ... Control part

Claims (6)

A nozzle for injecting a molten resin toward the inside of a cavity formed by a relatively close mold,
A runner for guiding the molten resin toward the tip of the nozzle;
A first valve for opening and closing the nozzle tip;
A second valve provided upstream of the first valve for controlling the flow rate of the molten resin guided toward the nozzle ;
A relief portion formed in a gap between the second valve and the nozzle, which is formed by making the diameter of the second valve smaller than the inner diameter of the flow path of the nozzle in contact with the second valve; Have
The relief portion receives the molten resin in a region formed between the first valve and the second valve when the first valve fully closes the tip of the nozzle ; An injection molding apparatus, wherein the received molten resin is caused to flow to a runner other than a region formed between the first valve and the second valve . A nozzle for injecting a molten resin toward the inside of a cavity formed by a relatively close mold,
A runner for guiding the molten resin toward the tip of the nozzle;
A first valve for opening and closing the nozzle tip;
A second valve provided upstream of the first valve for controlling the flow rate of the molten resin guided toward the nozzle ;
A relief part formed in a gap between the second valve and the nozzle, formed by providing a groove on the outer peripheral surface of the second valve,
The relief portion receives the molten resin in a region formed between the first valve and the second valve when the first valve fully closes the tip of the nozzle ; An injection molding apparatus, wherein the received molten resin is caused to flow to a runner other than a region formed between the first valve and the second valve . The injection molding apparatus according to claim 1, wherein the second valve fully opens or fully closes the runner. A valve pin that is inserted into the flow path of the nozzle and opens and closes the tip of the nozzle by a reciprocating motion along the insertion direction;
The injection molding apparatus according to any one of claims 1 to 3, wherein the first valve is a small-diameter portion at a distal end of the valve pin, and the second valve is a large-diameter portion on a proximal end side of the valve pin. The injection molding apparatus according to any one of claims 1 to 4 , further comprising a control unit that controls an operation timing of the second valve in accordance with a timing at which the first valve opens and closes a nozzle tip. The injection molding apparatus according to claim 1, wherein a plurality of the nozzles are provided in the one runner.

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