JP4305746B2 - Injection mold and injection molding machine equipped with the mold - Google Patents

Description

  The present invention relates to an injection mold for injection molding a material such as resin or rubber in a mold cavity and an injection molding machine using the mold.

  For example, by rotating a screw to plasticize the material, we measure one shot at the same time (referred to as “weighing process”), and then advance the screw to move the plasticized material through the mold sprue, runner, and gate. After injecting into the mold cavity (referred to as “injection process”), and after completion of the filling, the screw is further advanced to apply pressure so that the pressure of the resin in the mold can be maintained at a predetermined pressure. An injection molding machine that performs molding by controlling the speed (pressure-holding step) and then cools to obtain a product is known. Here, in the pressure holding step, after filling the material, pressure is applied to replenish the amount that the material cools and contracts in the cavity, thereby preventing sinking and cavities.

As described above, the conventional technique in which both the filling process of the molten material into the cavity and the pressure holding process are performed by the forward movement of the screw has the following problems.
(A) There are sprues, runners, gates and the like between the cavity and the screw, and the responsiveness is poor because the passage distance of the material is long.
(B) Since the gate cross-sectional area is extremely small with respect to the cross-sectional area of the mold cavity, the directionality (anisotropy) due to flow, residual stress, and material of the gate part solidify quickly in the molded product. Therefore, sink marks occur in the product part.

Therefore, such a problem of the prior art can be solved by separately performing the filling process of the molten material on the injection molding machine (screw) side and the pressure holding process on the mold side, respectively. As a prior art having a configuration that can be solved, for example, a material reservoir portion communicating with a cavity is provided, and the filling step of the molten material into the cavity and the material reservoir portion is performed by a screw of an injection molding machine, and the material It is known that the step of holding the pressure so as to replenish the molten material filled in the reservoir into the cavity is performed by a pressure holding pin that is capable of moving forward and backward in the material reservoir (for example, Patent Document 1, Patent Reference 2).
Japanese Patent Laid-Open No. 2001-300098 Japanese Patent Publication No. 3-77052

However, such prior art still has problems to be solved as follows.
“Problems of Patent Document 1”
The injection amount of the molten material filled in the cavity and the material reservoir is calculated and measured in advance, and the material filling space of the material reservoir corresponding to the filling material is determined.
In this case, for example, when a material supply shortage occurs during the material supply process from the injection molding machine, there may be a case where the material until the volume in the cavity is compressed is not filled in the material reservoir. That is, even if there is not enough material to compress the volume in the cavity due to a small amount of filling material in the material reservoir or a small amount of filling material in the cavity, A mechanism such as a hydraulic cylinder that presses the material into the cavity is activated, and there is a possibility that the holding pressure may be poor.
“Problems of Patent Document 2”
According to this prior art, a sensor for detecting the pressure of the molten material filled in the material reservoir is provided at the connecting portion between the rear end of the pressure holding pin and the ejector plate, and the rear end of the pressure holding pin. When the sensor detects the pressure applied to the pressure, the pressure holding amount is measured and filled. Accordingly, since the material can be pressed into the cavity by the advancement of the pressure holding pin after filling of the required pressure holding amount is detected, the above-described problem of poor pressure holding does not occur. It is very superior to
However, in the structure in which the pressure applied to the rear end of the pressure retaining pin is detected by a sensor as in this prior art, if there is a burr or the like on the inner wall of the material reservoir, its sliding resistance increases and the material It is also conceivable that the filling pressure cannot be detected accurately.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is an injection molding machine that performs a filling process and a pressure holding process by separate mechanisms. An object of the present invention is to provide an injection mold that can accurately and surely detect the metering / filling of a filling material in a material reservoir for storing the material to be performed, and to perform holding pressure, and an injection molding machine using the mold.

The technical means made by the present invention to achieve the above object is to inject and fill a molten material into a mold cavity and a material reservoir communicating with the cavity, and then press the molten material in the material reservoir into the cavity. This is a mold used for injection molding to hold the pressure and take out the molded product using the ejector pin after molding. It detects the molten material filling amount in the material reservoir and presses the filling material into the cavity after detection. A pressure holding pin that protrudes on the front surface, a pressure holding plate that drives the pressure holding pin to move forward and backward by connecting a drive mechanism to the rear surface, and a molten material filling amount in the material reservoir portion. when a predetermined amount, and a gate cut pin for blocking gate for filling the molten material into portion reservoir cavity and the material, the pressure-holding plate, the plate rear surface and gold Characterized by comprising providing a desired movable space between the inner.

  In the above technical means, the material reservoir portion is an ejector pin passage, and the pressure holding pin is also used as an ejector pin.

  Further, an injection molding machine using the mold, the position sensor for detecting the amount of displacement of the molten material in the cavity and the material reservoir by measuring the amount of displacement by the retracted position of the pressure holding plate or the driving mechanism. Further, it is possible to take technical means characterized in that the detection is performed by one or both of the pressure sensor that detects the pressure holding plate or the pressure applied to the driving mechanism.

  In the injection molding machine, a technical means in which the material reservoir portion is an ejector pin passage and the pressure holding pin also serves as an ejector pin can be taken.

  Since the present invention is configured as described above, it is an injection molding machine that performs the filling process and the pressure holding process by separate mechanisms, and accurately measures and fills the filling material in the material reservoir for storing the material for pressure holding. It is possible to provide an injection mold capable of reliably detecting and holding pressure and an injection molding machine using the mold.

  An embodiment of the present invention will be described with reference to the drawings. It should be noted that the present invention is not construed as being limited to these embodiments, and can be appropriately modified within the scope of the present invention.

[First embodiment]
FIG. 1 is a schematic diagram of a configuration according to the present embodiment, in which 10 is a mold, 21 is a hydraulic cylinder as a drive mechanism provided on the machine side and inserted into the mold 10, and an injection is shown in the upper part of the figure. A screw (not shown) of the molding machine is located. The drive mechanism is not limited to a hydraulic cylinder, and other drive mechanisms such as an air cylinder can be modified within the scope of the present invention. The present invention has a characteristic configuration in that a sensor for detecting metering / filling of a mold configuration and a material reservoir is provided on the machine side, and the components such as an injection molding machine main body are well-known configurations. Therefore, the characteristic components will be mainly described below.

As shown in FIG. 1, a mold 10 has a cavity 11 having a desired shape formed by a mating surface of a fixed mold 12 and a movable mold 13, and a material 14 is injected and filled into the cavity 11. A material reservoir 24 communicating with the inside of the mold cavity 11 and a material 14 filled in the material reservoir 24 are pressed into the cavity 11 to hold the pressure. The pressure pin 22 is provided.
In the present embodiment, the holding pin 22 is also used as an ejector pin.

The fixed mold 12 is attached to a fixed attachment plate 15, and one movable mold 13 is attached to the movable attachment plate 17 via a spacer block 16.
A material flow path is formed in the mold 10 by a sprue 18, a runner 19, and a gate 20.
The material 14 pushed out by a screw (not shown) passes through the material flow path and is filled into the cavity 11 and the material reservoir 24. In the present embodiment, the gate 20 is provided with a gate cut pin 20 a that blocks the gate 20.

  In the present embodiment, a space formed when the pressure retaining pin 22 is retracted in a passage (also referred to as a sliding passage) 23 of the pressure retaining pin 22 is used as the material reservoir 24, and the passage 23 is formed of the pressure retaining pin 22. The inner diameter slides with the outer diameter. Although not specifically shown, prevention of material leakage from the material reservoir 24 to the outside of the mold is achieved by a known technique.

  The pressure holding pin 22 is formed in a columnar shape having a desired length, for example, and the rear end 22a side is fixed to the front surface 29a of the pressure holding plate 29 and protrudes toward the cavity 11. The shape and quantity of the pressure retaining pins 22 and the material reservoirs 24 can be appropriately changed within the scope of the present invention according to the embodiment.

  The pressure holding plate 29 is provided in, for example, a space S1 formed between the movable mold 13 and the movable side mounting plate 17, and the pressure holding pins 22 are projected on the front surface 29a, and the hydraulic cylinder on the rear surface 29b. The rod tip 21a of 21 is connected, and the pressure retaining pin 22 is configured to be able to move forward and backward by moving forward and backward in the space S1.

Between the rear surface 29b of the pressure-holding plate 29 and the inner surface of the mold 10, for example, between the stopper 28 provided on the inner surface of the mold 10 located on the rear surface 29b of the pressure-holding plate, a desired amount is stored in the material reservoir 24. A movable space S <b> 2 is provided to the extent necessary for the pressure retaining plate 29 to retract when the material is filled and pressure is applied to retract the pressure retaining pin 22.
The movable space S <b> 2 is a space at least that allows the pressure holding pin 22 to move backward and the material accumulation / filling process to the material reservoir 24 can be performed. The width of the movable space S2 is not particularly limited, but it is preferable to change the design within a range that does not increase the mold size.

The hydraulic cylinder 21 interlocked with the pressure retaining pin 22 is provided with a pressure sensor 26 that detects the pressure applied to the hydraulic cylinder 21 and a position sensor 25 that detects the amount of movement (displacement) of the rod tip 21a of the hydraulic cylinder 21. It has been.
The pressure sensor 26 may detect pressure applied to the pressure holding pin 22 or the pressure holding plate 29, and the position sensor 25 detects the amount of displacement of the pressure holding pin 22 or the pressure holding plate 29. You may do.
Reference numeral 27 denotes a safety valve for setting a detection pressure in advance.
In the present embodiment, both the pressure sensor 26 and the position sensor 25 are provided, but it is of course possible to provide only one of the sensors.

  Next, an injection molding method using the mold having the above-described configuration will be described with reference to FIGS.

  As shown in FIG. 2A, FIG. 2A shows a state waiting for supply of material from the injection molding machine side, and the gate 20 is not closed. At this time, the pressure retaining pin 22 forms a material reservoir portion 24 that communicates with the cavity 11 with the sliding passage 23 of the pressure retaining pin 22 slightly retracted.

  Next, as shown in FIG. 2B, the material 14 is supplied from the gate 20 and filled in the cavity 11. When the material in the cavity 11 is filled in a molten state, the pressure retaining pin 22 moves backward in the sliding passage 23, so that part of the material 14 also flows into the material reservoir 24. As a result, when the material is filled in the cavity 11, the pressure retaining pins 22 and the pressure retaining plate 29 are retracted by the filling pressure of the material 14 until a predetermined amount of the material 14 is filled in the material reservoir 24. Will be.

Next, as shown in FIG. 2 (c), a predetermined pressure is detected and a predetermined displacement is detected by a pressure sensor 26 and a position sensor 25 installed in the hydraulic cylinder 21 interlocked with the pressure holding pin 22 and the pressure holding plate 29. When the amount is detected and it is detected that a predetermined amount of material 14 has flowed in, the gate 20 is shut off by the gate cut pin 20a, the flow of material is stopped, and the filling ends.
At the end of the filling, information from the pressure sensor 26 and / or the position sensor 25 is received by a control device (not shown), and the gate 20 is shut off with respect to the driving means (not shown) of the gate cut pin 20a. I am trying to issue a command.

  Thereafter, the pressure holding plate 29 is advanced by the forward operation of the hydraulic cylinder 21, whereby the pressure holding pin 22 is advanced and pressed toward the cavity 11 as shown in FIG. As a result, the material filled in the material reservoir 24 is pushed into the cavity 11 and a holding pressure is applied.

In the present invention, the plasticizing, rough weighing, and filling processes of the material 14 are performed on the screw side as in the past, but the weighing is detected by the amount of material filled in the cavity 11, and the holding pressure also serves as an ejector pin. Since the pressure is directly applied to the cavity 11 by the pressure holding pin 22, the material is rapidly supplied from the material reservoir 24 communicating with the cavity 11, and the pressure holding response is improved. The product becomes good and no sink marks occur in the product.
Even if burrs or the like are generated in the material reservoir 24, the amount of displacement of the molten material in the material reservoir 24 is detected by the retracted position of the holding plate 29 or the hydraulic cylinder 21 when the molten material is measured and filled. Since the detection is performed by one or both of the position sensor 25 and the pressure sensor 26 which is detected by the pressure applied to the pressure holding plate 29 or the hydraulic cylinder 21, accurate measurement can be performed ignoring sliding resistance due to burrs or the like. -The completion of filling can be detected.

  In this embodiment, the standby position of the pressure holding pin 22 before filling the material is retracted by a predetermined amount before filling the material. However, the standby position is appropriately changed depending on parameters such as the fluidity and curability of the material. It is possible to do so.

As described above, according to the present embodiment, since there is no sink, a precise molded product having excellent cavity shape transferability can be obtained.
Moreover, the effect can be exerted on a thermosetting resin, rubber, or the like, which is likely to generate burrs.
In addition, since the metering operation can be started immediately after the gate seal, the contribution to the manufacturing cycle is improved.
Further, since the pressure loss of the material flow path such as sprue and runner is small, the gate can be enlarged. Since the gate seal is performed after filling, the size of the gate at the time of filling can be made as large as possible. Therefore, the pressure loss in the sprue and runner is reduced and energy is saved.
Since the pressure holding operation can be performed quickly, the density of the molded product is increased and the product strength is improved. In addition, according to the present embodiment, it is possible to provide a plurality of material reservoirs, and in this way, a molded product that is more isotropic than the conventional method can be obtained, and the molded product density can be obtained. (Molded product strength) can also be controlled.

  In the present embodiment, the material reservoir portion 24 communicating with the cavity 11 is used as the passage 23 of the pressure retaining pin 22, and the pressure retaining pin 22 is also used as the ejector pin. However, the present invention is not limited to this. In addition, a material reservoir portion that communicates with the cavity 11 is formed separately, and a pressure holding pin 22 that presses the material accumulated in the material reservoir portion into the cavity 11 may be provided on the mold side separately from the ejector pin. Good.

  In addition, the pressure holding pin 22 that also serves as an ejector pin may hold pressure so as to be flush with the shape of the inner peripheral surface of the cavity 11, but may be pushed into the cavity 11. In particular, it is suitable when forming a recess or a hole in the product.

[Second Embodiment]
FIG. 3 is a configuration diagram of a mold according to the present embodiment. In this embodiment, the gate format is different from that of the first embodiment. In addition, since it is the same as 1st embodiment about another member, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
As shown in FIG. 3, the mold 10 according to the present embodiment is configured so that the flow path of the gate 20 that supplies the material 14 into the cavity 11 is blocked by the gate cut pin 32 interlocked with the gate cut cylinder 31. Yes.

  In the mold of the configuration of the present embodiment, an injection molding method will be described with reference to FIGS.

  FIG. 4A shows a state waiting for the material supply from the injection molding machine side as shown in the figure, and the gate 20 is not closed. In this embodiment, at this time, the pressure retaining pin 22 is located at the end of the sliding passage 23 of the pressure retaining pin 22 and is flush with the inner surface of the cavity 11.

  Next, as shown in FIG. 4B, the material 14 is supplied from the gate 20 and filled in the cavity 11. When the material 14 in the cavity 11 is filled in a molten state, the holding pressure pin 22 moves back in the sliding passage 23 due to the filling pressure of the material 14, so that the inside of the passage 23 becomes a material reservoir 24. A part of the material 14 also flows into this portion. As a result, the pressure holding pin 22 moves backward together with the pressure holding plate 29 until a predetermined amount of the material 14 is filled in the material reservoir 24.

Next, as shown in FIG. 4 (c), a predetermined pressure is detected by a pressure sensor 26 / position sensor 25 installed in the hydraulic cylinder 21 interlocked with the pressure retaining pin 22 / pressure retaining plate 29. When the amount of displacement is detected and it is detected that a predetermined amount of material 14 has flowed in, the gate 20 is shut off by the gate pin cut pin 32, the flow of material is stopped, and filling is completed.
At the end of the filling, information from the pressure sensor 26 and / or the position sensor 25 is received by a control device (not shown), and the gate 20 is shut off with respect to the hydraulic cylinder 31 which is a driving means of the gate cut pin 32. I am trying to issue a command.

  Thereafter, the pressure holding plate 29 is advanced by the forward operation of the hydraulic cylinder 21, whereby the pressure holding pin 22 is advanced and pressed toward the cavity 11 as shown in FIG. As a result, the material in the material reservoir 24 is pushed into the cavity 11 to apply a holding pressure.

As described above, according to the present embodiment, since there is no sink, a precise molded product having excellent cavity shape transferability can be obtained.
In addition, since the metering operation can be started immediately after the gate seal, the contribution to the manufacturing cycle is improved.

In each of the embodiments, the gate is cut off by the gate cut pin and then the holding pressure is applied. However, in the case of the so-called submarine gate method, this blocking step is unnecessary, and a predetermined pressure or position is set. After confirming that a predetermined amount of material is filled in the cavity and the material reservoir, a predetermined holding pressure may be applied to the cavity using a holding pin.
As described above, according to the present invention, the injection filling process is performed on the injection molding machine side, and the pressure-holding process is directly held in the cavity with the pressure-holding pins in the mold, so that sinking occurs. And a precise molded product with excellent cavity shape transferability could be obtained.
In addition, by applying the present invention, the effect can be exerted on a thermosetting resin, rubber, or the like which is likely to generate burrs.
In addition, in the injection molding method having a gate cutting step, the metering operation can be started immediately after the gate seal, which contributes to the improvement of the manufacturing cycle.

Schematic of the metal mold | die concerning 1st embodiment. Schematic of the material filling / holding step according to the first embodiment. Schematic of the metal mold | die concerning 2nd embodiment. It is the schematic of the material filling and pressure holding process concerning 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mold 11 Cavity 12 Fixed mold 13 Movable mold 14 Material 18 Sprue 19 Runner 20 Gate 20a Gate cut pin 21 Drive device (hydraulic cylinder)
22 Holding pin (ejector pin)
23 Sliding passage 24 Material reservoir 25 Position sensor 26 Pressure sensor 29 Holding pressure plate S2 Movable space

Claims (6)

Injecting and filling molten material into the mold cavity and the material reservoir communicating with the cavity, then pressing the molten material in the material reservoir into the cavity and holding the pressure, and then ejecting the molded product using the ejector pin after molding A mold used for molding,
A pressure holding pin that detects the amount of molten material filled in the material reservoir and presses the filled material into the cavity after detection,
A pressure retaining plate for projecting the pressure retaining pin on the front surface and connecting the driving mechanism to the rear surface to drive the pressure retaining pin so as to freely advance and retract ;
A gate cut pin that shuts off a gate for filling the molten material into the cavity and the material reservoir when the molten material filling amount of the material reservoir reaches a predetermined amount ;
The pressure-holding plate is provided with a desired movable space between the rear surface of the plate and the inside of the mold.   2. The injection mold according to claim 1, wherein the material reservoir is an ejector pin passage, and the pressure holding pin is also used as an ejector pin. Injecting and filling molten material into the mold cavity and the material reservoir communicating with the cavity, then pressing the molten material in the material reservoir into the cavity and holding the pressure, and then ejecting the molded product using the ejector pin after molding A molding machine,
A pressure holding pin that detects the amount of molten material filled in the material reservoir and presses the filled material into the cavity after detection,
A pressure retaining plate for projecting the pressure retaining pin on the front surface and connecting the driving mechanism to the rear surface to drive the pressure retaining pin so as to freely advance and retract ;
A gate cut pin that shuts off a gate for filling the molten material into the cavity and the material reservoir when the molten material filling amount of the material reservoir reaches a predetermined amount ;
The pressure holding plate uses a mold configured to provide a desired movable space between the rear surface and the inside of the mold,
An injection molding machine characterized in that the completion of metering and filling of the molten material in the cavity and the material reservoir is detected by a position sensor that detects the amount of displacement by the retracted position of the holding plate or the drive mechanism. Injecting and filling molten material into the mold cavity and the material reservoir communicating with the cavity, then pressing the molten material in the material reservoir into the cavity and holding the pressure, and then ejecting the molded product using the ejector pin after molding A molding machine,
A pressure holding pin that detects the amount of molten material filled in the material reservoir and presses the filled material into the cavity after detection,
A pressure retaining plate for projecting the pressure retaining pin on the front surface and connecting the driving mechanism to the rear surface to drive the pressure retaining pin so as to freely advance and retract ;
A gate cut pin that shuts off a gate for filling the molten material into the cavity and the material reservoir when the molten material filling amount of the material reservoir reaches a predetermined amount ;
The pressure holding plate uses a mold configured to provide a desired movable space between the rear surface and the inside of the mold,
An injection molding machine characterized in that the completion of metering and filling of the molten material in the cavity and the material reservoir is detected by a pressure sensor that detects the pressure applied to the holding plate or the driving mechanism. Injecting and filling molten material into the mold cavity and the material reservoir communicating with the cavity, then pressing the molten material in the material reservoir into the cavity and holding the pressure, and then ejecting the molded product using the ejector pin after molding A molding machine,
A pressure holding pin that detects the amount of molten material filled in the material reservoir and presses the filled material into the cavity after detection,
A pressure retaining plate for projecting the pressure retaining pin on the front surface and connecting the driving mechanism to the rear surface to drive the pressure retaining pin so as to freely advance and retract ;
A gate cut pin that shuts off a gate for filling the molten material into the cavity and the material reservoir when the molten material filling amount of the material reservoir reaches a predetermined amount ;
The pressure holding plate uses a mold configured to provide a desired movable space between the rear surface and the inside of the mold,
Completion of the metering and filling of the molten material in the cavity and the material reservoir is detected by a position sensor that detects the amount of displacement based on the retracted position of the pressure-holding plate or the driving mechanism, and the pressure applied to the pressure-holding plate or the driving mechanism. An injection molding machine characterized by detecting by both pressure sensors. 6. The injection molding machine according to claim 3, wherein the material reservoir portion is an ejector pin passage, and the pressure holding pin is also used as an ejector pin.

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