JP3045078B2 - Ejector pin with pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ejector pin with a pressure sensor capable of detecting the pressure of a resin filled in a cavity of a molding die.

[0002]

2. Description of the Related Art FIG. 11 shows an example of a conventional injection molding machine and its control system. The material supplied into the cylinder 100 is sent to the front of the cylinder 100 by the screw 102 while being heated by the heater 101, and is compressed, kneaded, and plasticized. The screw 102 retreats with an increase in the amount of plasticized resin that has been extruded and accumulated in the front part of the cylinder 100, and stops rotating when a predetermined amount is reached. (Plasticization
Measuring Step) Next, pressurized oil is sent to the injection cylinder 103 to advance the screw 102, and the plasticized resin is injected into the cavity of the mold 104 which has been clamped. (Injection Step) After cooling, the mold 104 is opened and the molded product is taken out. (Cooling process)

In the above-described injection molding, quality evaluation of products and classification of defective products are visually performed, and setting conditions are input from a control panel based on the result of the judgment. The setting conditions are a screw position, a screw speed, a resin temperature, a resin pressure, a cooling time, etc., which are injection molding elements. That is, this method is an open-loop control method in which the injection pressure, resin temperature, and injection speed are manipulated variables on the molding machine side, and includes an unsteady flow and heat conduction of a viscous fluid which is a variable element on the molding machine side. Complicated factors have a significant effect on the quality of the molded article.
This is considered to be because it is difficult to analyze the pressure, temperature, and the like in the cavity of the mold according to this method, and it is not possible to find optimal molding conditions.

FIG. 12 shows another example of a conventional injection molding machine and its control system. This system is a pressure waveform follow-up control, in which the pressure in the cylinder 100 is measured by strain detection by a load cell 105, and the optimum speed of the molding conditions is determined and fed back to a servomotor 106 for driving the screw 102. That is, the present system is a semi-closed loop control system that feeds back a change in the pressure in the cylinder 100. Therefore, the pressure is detected just before the mold 104, and the actual pressure inside the mold is not detected, so that a correct optimum speed cannot be set.

FIG. 13 is an enlarged sectional view of a mold in an example of a conventional injection molding machine. The mold includes a load cell 111 for directly detecting the pressure in the cavity 110, and a load cell 1 in contact with a base of an ejector pin 112 for projecting a molded product out of the cavity 110 after completion of molding.
13 is provided separately from the ejector pin 112. Each of the load cells 111 and 113 is attached to the die by performing a special hole processing and a groove processing.

[0006]

According to the control system of the injection molding machine shown in FIG. 11, many experiments are required to set the optimum conditions in view of the quality of the molded product and the like. In addition, the quality of a molded product varies due to a variable element on the molding machine side. Further, if the setting conditions on the molding machine side are incorrect, the mold may be damaged.

According to the control system of the injection molding machine shown in FIG. 12, since the pressure in the mold is not detected, it has the same problem as the control system of FIG.

According to the control system of the injection molding machine shown in FIG. 13, since the load cells 111 and 113 are large, they cannot be mounted unless the die is machined. Some molds cannot be machined, and in that case, mounting becomes impossible. Labor, labor,
Since the cost of the load cell itself is high, this structure is difficult to adopt and difficult to spread.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ejector pin with a pressure sensor which can be easily attached to an existing mold because machining of the mold is unnecessary, and can detect the pressure in the cavity of the mold. And

[0010]

An ejector pin with a pressure sensor according to claim 1 has a first cavity having a cavity.
And a second template having a core and movable relative to the first template, and a resin is filled between the cavity and the core to form a molded article. In an ejector pin which is applied to a molding die for molding and presses the molded product at the tip when the first and second template plates are relatively separated from each other and projects from the template plate, a housing and a lower surface thereof An iron plate provided with a pressure sensor and supported at both ends inside the housing, and the molded product protrudes at the tip and slidably penetrates the housing and protrudes out of the housing. A bar-shaped portion, a collar portion larger than the bar-shaped portion, provided at a rear end of the bar-shaped portion, and housed in the housing, and provided on a lower surface of the collar portion and smaller than a lower surface of the collar portion. projection and assembled to be in contact with the upper surface of the steel plate in the area It is characterized by having.

An ejector pin with a pressure sensor according to a second aspect is the ejector pin with a pressure sensor according to the first aspect, wherein the pressure sensor is a resistance wire strain gauge .

[0012]

[0013]

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. In the control system of the injection molding machine of the present embodiment shown in FIG. 1, a pressure sensor and a temperature sensor are provided on the molding die B side. Detect temperature. These signals are given to the feedback unit 1 and used for controlling the screw position, screw speed, resin temperature, resin pressure, cooling time, etc., which are injection molding elements.

FIG. 2 is a sectional view of a molding die B in the control system of the injection molding machine of the present embodiment. The molding die B has a fixed-side mounting plate 10 attached to a fixed-side holder of the molding machine and a movable-side attachment plate 11 attached to a movable-side holder of the molding machine. The fixed-side mounting plate 10 has a fixed-side mold plate 1 having a female cavity 12a.
2 are installed. The movable side mounting plate 11 includes:
A movable mold plate 13 having a male core 13 a is attached via a receiving plate 14 and a spacer block 15.

The molding die B can be divided between a fixed mold plate 12 and a movable mold plate 13. In accordance with the movement of the holder of the molding machine, the movable mold plate 13 moves relative to the fixed mold plate 12 in a direction perpendicular to the plate surface, thereby opening and closing the fixed mold plate 12 and the movable mold plate 13. Is performed. The fixed mold plate 12 is provided with a guide bush 19, the movable mold plate 13 is provided with a guide post 18, and the guide post 1 is provided.
8 is slidably inserted into the guide bush 19. Opening and closing of the fixed mold plate 12 and the movable mold plate 13 is guided by the guide bush 19 and the guide post 18.
When the fixed mold plate 12 and the movable mold plate 13 are closed, the cavity 12a and the core 13a are assembled at an accurate position.

A sprue 16 serving as a path for injecting molten resin into the molding die B from the nozzle of the cylinder 2 of the molding machine, and a molding die B A locating ring 17 serving as a positioning means when attaching to the nozzle of the cylinder 2 is attached.

An eject plate 21 is provided on the movable side mounting plate 11 side. Eject plate 21
Is provided with an ejector pin 24 which protrudes from the core 13a and protrudes the molded product out of the mold when the molding die B is opened. In addition, the eject plate 21 includes
By returning the eject plate 21 to a predetermined position when the molding die B is closed, the ejector pins 24
Is provided with a return pin 22 for retracting.

As shown in FIG. 3, the ejector pins 2
4 is a rod-like portion 25 having a circular cross section which protrudes the molded product at the tip end.
And a columnar flange 26 provided at the rear end of the rod 25.
And The outer diameter of the flange 26 is larger than that of the rod 25.

The ejector pin 24 has a pressure detecting means 3
0 is integrally attached. Pressure detecting means 3 of this example
Numeral 0 has a housing 31 for accommodating the flange 26 of the ejector pin 24, and a pressure sensor 32 provided inside the housing 31.

The housing 31 for accommodating the collar 26 has a cylindrical shape. The housing 31 includes a circular upper plate portion 33 elastically fixed to the upper surface of the collar portion 26, a circular lower plate portion 34 facing the lower surface of the collar portion 26 at a predetermined interval, and Cylindrical side plate 3 connecting plate 33 and lower plate 34
5 is provided. In this example, the ejector pin 2
4 is penetrated through the upper plate 33 of the housing 31, and the upper surface of the flange 26 and the lower surface of the upper plate 33 of the housing 31 are elastically fixed with the silicone resin 36. ing.

A pressure sensor 32 is fixed on the lower plate portion 34 inside the housing 31. A conducting wire from the pressure sensor 32 is led out through a through hole provided in the side plate portion 35. Pressure sensor 32 and collar 26
There is an appropriate gap between the lower surface of the device. When the resin is filled into the cavity 12a of the closed molding die B, the pressure is applied to the tip of the ejector pin 24. When a force is applied to the ejector pin 24 by this pressure, the silicone resin 36 fixing the ejector pin 24 and the housing 31 is elastically deformed, and the flange 26 of the ejector pin 24 comes into contact with the pressure sensor 32.

The gap between the pressure sensor 32 and the lower surface of the collar 26 is formed by elastically deforming the silicone resin 36 when the ejector pin 24 moves due to the pressure in the cavity 12a, so that the collar 26 contacts the pressure sensor 32. It is set to such an extent that appropriate pressure measurement can be performed with good sensitivity by contact. Without providing an appropriate gap as described above, the collar 26
If the pressure sensor 32 is always in contact with the pressure sensor 32, there is a possibility that the pressure sensor 32 may react due to the weight of the ejector pin 24, or the pressure sensor 32 may detect vibration or the like received by the ejector pin 24. is there.

If the flange 26 of the ejector pin 24 and the pressure sensor 32 are housed in the housing 31 as in this embodiment, the pressure sensor 32 is protected, the appearance is good, and the pressure is reduced as described above. A configuration in which an appropriate gap is provided between the sensor 32 and the collar portion 26 can be adopted.

FIG. 4A shows an external view, and FIG. 4B shows an enlarged sectional view of the pressure sensor 32. The pressure sensor 32 comprises two layers of molybdenum sulfides 40, 40, which are semiconductors, and a silver upper electrode 41
And a lower electrode 42, and the terminals 43 and 44 are respectively derived from the electrodes 41 and 42.
The whole is covered with an insulator 45 such as polyimide. The pressure sensor 32 is extremely thin and small, and can be formed, for example, to a thickness of about 0.08 mm and a diameter of about 5 mm.

The injection molding operation in the above configuration will be described. In FIG. 1, the material supplied into the cylinder 2 is sent to the front of the cylinder 2 by a screw 4 while being heated by a heater 3, and is compressed, kneaded and plasticized. The screw 4 retreats with an increase in the amount of plasticized resin pushed out and accumulated in the front part of the cylinder 2, and when a predetermined amount is reached, the screw 4 stops rotating. Next, the pressurized oil is sent to the injection cylinder 5 to advance the screw 4, and the plasticized resin is injected into the cavity 12a of the molding die B clamped as shown in FIG.

In the step of injecting the resin into the molding die B, the pressure in the cavity 12a is applied to the ejector pin 24, and this pressure is detected by the pressure sensor 32 provided on the flange 26 of the ejector pin 24. This signal is provided to the feedback unit 1 shown in FIG.
Screw position, screw speed,
Closed loop control of resin temperature, resin pressure, cooling time, etc. can be performed. After an appropriate cooling time has elapsed after the completion of the molding, the mold is opened and the molded product is taken out.

An example in which the pressure in the molding die is measured using the ejector pin 24 with the pressure sensor 32 described above will be described. FIG. 5 shows a test mold 50. The shape of the cavity (the shape of the molded product) of the test mold 50 is a spiral shape. A total of 12 ejector pins were used in the test die 50, and four of them were used as the ejector pins 24 having the pressure sensor 32 described above. The ejector pins 24 with the pressure sensors 32 are disposed at a point a immediately before the cavity into which the resin is injected, a point b at the entrance of the cavity, a point c at the middle of the cavity, and a tip of the cavity. There is a certain d point. The total length from point a to point d is 376.2 mm. The injection molding machine to which this mold is mounted and its control system are substantially the same as those shown in FIG.

FIG. 6 is a diagram showing a pressure cycle in the cavity detected by the pressure sensor 32 of the ejector pin 24 in the injection molding machine equipped with the test die 50. According to this pressure cycle diagram, in each of the first cycle and the second cycle, the pressure value becomes smaller in the order of points a, b, c, and d. Means that the resin has reached the end of. Since the flow velocity of the resin can be determined from the displacement of the pressure line at each point in each cycle, the flow analysis can be performed from this waveform diagram. If the waveform of the pressure cycle when correct molding is performed is experimentally recognized for each measurement point, the injection molding element can be controlled so that a good product is always obtained.

FIGS. 7A to 7D show the first and second cycle pressure waveforms at points a to d, respectively. As shown in FIG.
In both cycles, when pressure is detected from point a to point c, but no pressure is detected at point d, it means that the resin has not reached the end of the cavity and correct molding has not been performed. Show.

In the ejector pin 24 with the pressure sensor 32 of this embodiment, since the main body of the ejector pin and the pressure sensor 32 are integrated, the ejector pin 24 can be replaced with a conventional ejector pin without performing special processing on a mold. The number of measurement points can be easily increased simply by installing the apparatus, whereby the waveform pattern of the pressure cycle can be grasped more precisely.

Second to fourth examples of the embodiment of the present invention will be described with reference to FIGS. These are examples in which a resistance wire strain gauge is used as a pressure sensor. A resistance wire strain gauge is a type of pressure sensor that detects pressure by utilizing a change in resistance value when a resistance wire is distorted by an external pressure.

A second example will be described with reference to FIG. FIG.
4 is an enlarged sectional view of a main part of the ejector pin 60. FIG. A large-diameter flange portion 62 is provided at the lower end of the rod portion 61 of the ejector pin 60. A projection 67 is provided substantially at the center of the lower surface of the collar portion 62. The rod portion 61 of the ejector pin 60 slidably penetrates an upper plate portion of the substantially cylindrical housing 63, and the collar portion 62 is housed inside the housing 63. An iron plate 64 is provided on the bottom inside the housing 63 via a spacer 66. A strain gauge 65 as a pressure sensor is provided on the lower surface side of the iron plate 64 supported by the spacer 66. The configuration of the parts other than those illustrated is substantially the same as that of the first example.

When a downward load is applied to the ejector pin 60 in the axial direction, a load is applied to a substantially central portion of the upper surface of the iron plate 64 by the protrusion 67 on the bottom surface of the flange 62. Iron plate 64
Since both sides are supported by the spacers 66, they are bent when a load is applied, and the strain gauge 65 detects the amount of the strain. The load can be obtained from the strain amount by the calculation formula of the bending moment.

A third example will be described with reference to FIG. FIG.
3 is an enlarged sectional view of a main part of the ejector pin 70. FIG. A large-diameter flange portion 74 is provided at the lower end of the rod portion 71 of the ejector pin 70. At least one pair of support legs 75 is attached to the outer edge of the lower surface of the flange 74 with the center of the ejector pin 70 sandwiched therebetween. The rod-shaped portion 71 of the ejector pin 70 slidably penetrates the upper plate of the substantially cylindrical housing 72, and the collar 74 and the support leg 75 are housed inside the housing 72. The sum of the thickness of the collar 74 and the height of the support legs 75
Corresponds to the height inside. A strain gauge 73 as a pressure sensor is provided on the lower surface side of the collar 74. The configuration of the parts other than those illustrated is substantially the same as that of the first example.

When a downward load is applied to the ejector pin 70 in the axial direction, a load is applied to the collar portion 74 and the strain is detected. The strain gauge 73 detects the amount of the strain. The load can be obtained from the strain amount by the calculation formula of the bending moment.

A fourth example will be described with reference to FIG. FIG. 10 is an enlarged sectional view of a main part of the ejector pin 80. A large-diameter flange portion 85 is provided at the lower end of the rod portion 81 of the ejector pin 80. The rod portion 81 of the ejector pin 80 slidably penetrates an upper plate portion of a substantially cylindrical housing 82, and the flange 85 is housed inside the housing 82. A spacer 84 is provided inside the housing 82, and the flange 85 is sandwiched between the upper lid of the housing 82 and the spacer 84. A strain gauge 83 as a pressure sensor is provided on a lower surface side of the flange portion 85. The configuration of the parts other than those illustrated is substantially the same as that of the first example.

When a downward load is applied to the ejector pin 80 in the axial direction, a load is applied to the flange portion 85 and the strain is detected. The strain gauge 83 detects the amount of the strain. The load can be obtained from the strain amount by the calculation formula of the bending moment.

[0039]

According to the present invention, since the pressure detecting means is provided integrally with the rear end of the ejector pin, the following effects can be obtained. (1) There is no need to process the mold to install the pressure sensor, and labor is not required.

(2) Since the ejector pin itself, which is a part of the mold, has a function as a pressure sensor, mounting is easy and the number of parts is reduced.

(3) Appropriate molding conditions can be set by detecting the pressure in the cavity.

(4) By displaying the detected pressure in the cavity, a pressure waveform line can be obtained. By analyzing the pressure waveform line, an appropriate gate sealing time can be confirmed. Can be set.

(5) The flow analysis can be performed by arranging a large number of ejector pins of the present invention in the cavity.

(6) Since the ejector pins themselves function as pressure sensors, breakage of the ejector pins generated during molding can be easily detected.

(7) Since the pressure sensor can be attached without processing the mold, the strength of the mold is not reduced.

(8) Since the pressure in the cavity can be detected, the injection pressure can be appropriately suppressed to prevent the mold from being damaged.

(9) Since the pressure sensors can be arranged at various places in the cavity, it can be confirmed from the pressure in the cavity that the resin is filled in the cavity.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of an injection molding machine according to a first example of an embodiment of the present invention.

FIG. 2 is a sectional view of a molding die according to a first example of an embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a main part of an ejector pin according to a first example of an embodiment of the present invention.

FIG. 4 is a sectional view of a pressure sensor used in a first example of an embodiment of the present invention.

FIG. 5 is a plan view of a test mold to which the ejector pin according to the first embodiment of the present invention is applied.

FIG. 6 is a diagram showing pressure cycles at various points in the mold in the injection molding performed using the test mold shown in FIG.

FIG. 7 is a diagram showing pressure cycles of each point in the mold in the injection molding performed using the test mold shown in FIG. 5 separately for each point.

FIG. 8 is an enlarged sectional view of a main part of an ejector pin according to a second example of the embodiment of the present invention.

FIG. 9 is an enlarged sectional view of a main part of an ejector pin according to a third embodiment of the present invention.

FIG. 10 is an enlarged sectional view of a main part of an ejector pin according to a fourth example of an embodiment of the present invention.

FIG. 11 is a block diagram showing an overall configuration of an example of a conventional injection molding machine.

FIG. 12 is a block diagram showing the overall configuration of another example of a conventional injection molding machine.

FIG. 13 is a sectional view of a molding die in another example of the conventional injection molding machine.

[Explanation of symbols]

 12 Fixed-side template as a first template 12a Cavity 13 Movable-side template 13a as a second template 13a Core 24,60,70,80 Ejector pins 25,61,71,81 Rod-shaped parts 26,62, 74, 85 Collar part 30 Pressure detecting means 31, 63, 72, 82 Housing 32, 65, 73, 83 Pressure sensor 36 Silicon resin B Mold for molding

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Chisato Akinari 629 Oshiba, Mobara-shi, Chiba Futaba Electronics Industry Co., Ltd. (JP, A) JP-A-51-50357 (JP, A) JP-A-4-75930 (JP, U) Swiss patent invention 679469 (CH, A5) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) B29C 45/40 B29C 33/44 B22D 17/22

Claims (2)

(57) [Claims] 1. A combination of a first template having a cavity and a second template having a core and movable relative to the first template, wherein the cavity and the core are combined. An ejector which is applied to a molding die for molding a molded product by filling a resin between them, and which pushes the molded product at a tip and protrudes from the template when the first and second template plates are relatively separated from each other. In the pin, a housing, a pressure sensor provided on a lower surface thereof, an iron plate provided with both ends supported inside the housing, and a molded product protruding at a tip end and allowing the housing to slide. A rod portion that penetrates and protrudes out of the housing, a collar portion that is larger than the rod portion and is provided at a rear end of the rod portion and is housed in the housing, and is provided on a lower surface of the collar portion. It is in the upper surface of the steel plate with a smaller area than the lower surface of the flange portion Ejector pins with a pressure sensor and a projection assembled in contact. 2. The pressure sensor is a resistance strain gauge.
The ejector pin with a pressure sensor according to claim 1.