JP2004074431A - Injection molding method for rubber roller and injection molding apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method capable of well keeping the shape and physical properties of a rubber roller constant. <P>SOLUTION: The injection molding method for the rubber roller uses an injection means having a plunger for metering a liquid rubber material to inject the same from the opening part provided to the leading end of the injection means, mounts a roller shaft body in a mold and injects the liquid rubber material in the mold to mold the rubber roller. In the injection molding method, the liquid rubber material is injected in the mold while keeping the injection pressure of the injection means almost constant. A drive means for moving the plunger and capable of continuously changing the moving speed of the plunger at a minute interval is provided to the injection means. A pressure detection means for detecting the pressure of the liquid rubber material is provided near the opening part of the injection means and a control unit performs the feedback control of the drive means on the basis of the pressure detected by the pressure detection means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rubber roller molding technique, and more particularly to a rubber roller injection molding method and an injection molding apparatus using liquid silicone rubber.
[0002]
[Prior art]
In order to mold a molded product of liquid silicone rubber, kneading is performed at room temperature by a static mixer from a pump that pumps the components A and B of the liquid rubber material, and the plunger is at the most advanced position. The liquid rubber material after kneading is pressure-fed from a raw material charging port installed in a plunger cylinder in which an injection hole is closed, and after the plunger is retracted to a position where a fixed amount is measured, the plunger moves forward, At that time, an injection molding apparatus having a mechanism for shutting off a flow path from a static mixer, opening an injection hole of a plunger cylinder, and injecting and molding into a heated mold is used.
[0003]
FIG. 3 is a vertical sectional view showing a schematic configuration of a conventional typical liquid silicone rubber injection molding apparatus.
[0004]
As shown in FIG. 3, in the conventional injection molding apparatus, a plunger 303 is disposed in a plunger cylinder 302 in the main body 301 of the injection molding apparatus. The plunger cylinder 302 is provided with a raw material charging port 304 for charging a liquid rubber material, and upstream of the raw material charging port 304, a backflow prevention for preventing a backflow of the liquid rubber material during injection. A valve 305 and a static mixer 306 for kneading the liquid rubber material are provided. Further, upstream of the static mixer 306, pipings 307 and 308 for pumping the A component and the B component of the liquid rubber material to the static mixer are provided.
[0005]
The raw materials A and B of the molded product are pumped by a material supply pump (not shown), kneaded at room temperature by a static mixer 306 via pipes 307 and 308, and sent to a raw material inlet 304. At this time, the plunger 303 is at the most distal position (the uppermost position in FIG. 3), and the injection hole of the shut-off nozzle 309 provided at the tip of the plunger cylinder 302 is closed. Thereafter, the kneaded liquid rubber material is introduced from a raw material introduction port 304 provided near the tip of the plunger cylinder 302, and the plunger 303 is retracted to a position where a predetermined amount is measured, and is filled in the measuring section. . Thereafter, the plunger 303 moves forward, and at that time, the flow path from the static mixer 306 is closed by the check valve 305, and the injection hole of the shut-off nozzle 309 provided at the tip of the plunger cylinder 302 is opened and heated. The raw material is injected into the mold 311. After the raw material is cured in the mold, it is taken out as a molded product.
[0006]
The plunger driving means 310 is generally of a hydraulic type or an electric type using a servomotor. In the case of a hydraulic type, a hydraulic cylinder is used, and in the case of an electric type, a servomotor is used as a driving source and driven by respective control means. In any case, a method is generally used in which the injection stroke of the plunger thrust and speed is increased from three to five and divided into five parts, and each is set while trial casting.
[0007]
When a roller-shaped molded product is manufactured, for example, as shown in FIG. 4, a cylindrical mold body 2, a roller shaft 4 provided therein, an upper piece 1 and a lower piece disposed at both ends thereof. A mold having a piece 3 is used. A liquid rubber material is injected into the gap 5 around the roller shaft from the injection hole 3a provided in the lower piece, and is solidified to obtain a rubber roller having an elastic body formed around the roller shaft. At this time, the flow path of the liquid rubber is narrow near the injection hole and wide in the gap around the roller shaft loaded in the mold. For this reason, it is difficult to keep the pressure applied to the injection material constant in the conventional device configuration that controls the driving of the plunger without being based on the material pressure. In some cases, it is difficult to keep the electrical resistance of the conductive rubber roller constant.
[0008]
In addition, since the rubber roller has a long and narrow mold space and is filled with the material in the longitudinal direction, the injection resistance continuously changes in the longitudinal direction. In such a molding, it is sometimes difficult to secure the uniformity of the shape and the physical properties for the same reason with the conventional apparatus configuration in which the drive control of the plunger cannot be performed at minute intervals.
[0009]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an injection molding method capable of maintaining a constant shape and physical properties of a rubber roller, and to provide an injection molding apparatus suitable for the injection molding method.
[0010]
[Means for Solving the Problems]
The present inventors have found that, by injecting an appropriate amount of a liquid rubber material to be injected at a constant pressure, a good rubber roller can be formed without worrying about its shape and physical properties. More specifically, the roller shaft is loaded into a mold by using an injection means having a plunger for measuring a liquid rubber material and injecting the liquid rubber material from an opening at the tip (hereinafter sometimes referred to as an “injection hole”). In a method of injection molding a rubber roller by injecting and forming a rubber material, a means for measuring a pressure applied to the liquid rubber material is provided near the injection hole, and a means for measuring a change in flow resistance of the flow path in the mold is provided. By feeding back the signal data of the corresponding pressure measuring means and injecting the liquid rubber material so that the pressure applied to the liquid rubber material in the plunger becomes constant, it is possible to obtain a good rubber roller. I found it. Further, in an injection molding method of a rubber roller, which uses an injection means having a plunger for measuring a liquid rubber material and injecting the liquid rubber material from an opening at the tip, loading a roller shaft into a mold and injecting and forming the liquid rubber material, It has been found that a good rubber roller can be obtained by injecting the liquid rubber material by continuously increasing or decreasing the speed of the plunger into which the liquid rubber material is injected at minute intervals. Further, as an apparatus, a rubber roller is used in which an injection means having a plunger for measuring and injecting the liquid rubber material from the opening at the tip is used, the roller shaft is loaded into a mold, and the liquid rubber material is injected and formed. In the injection molding apparatus, there is provided means for measuring pressure on the liquid rubber material in the vicinity of the injection hole, and means for feeding back signal data of the pressure measuring means corresponding to a change in flow resistance of the flow path in the mold. It has been found that a rubber roller injection molding apparatus having the liquid rubber material injecting means capable of continuously increasing or decreasing the speed at minute intervals is suitable for carrying out these injection molding methods. The present invention has been made based on these findings.
[0011]
That is, according to the present invention, a roller shaft is loaded into a mold, and the liquid rubber material is injected into the mold by using an injection means having a plunger for measuring and injecting the liquid rubber material from the opening at the tip. In an injection molding method of a rubber roller for molding a rubber roller,
There is provided an injection molding method of a rubber roller, characterized by injecting a liquid rubber material into a mold while keeping an injection pressure of the injection means substantially constant.
[0012]
In this method, the injection pressure can be maintained substantially constant by detecting the injection pressure and performing feedback control of the moving speed of the plunger based on the detected injection pressure.
[0013]
Further, by injecting the liquid rubber while continuously reducing the moving speed of the plunger at minute intervals, the injection pressure can be kept substantially constant.
[0014]
Further, according to the present invention, by using an injection means having a plunger for measuring and injecting the liquid rubber material from the opening at the tip, the roller shaft is loaded into the mold, and the liquid rubber material is injected into the mold. In an injection molding method of a rubber roller for molding a rubber roller,
A method of injection molding a rubber roller, characterized by injecting the liquid rubber while continuously changing the moving speed of the plunger at minute intervals, is provided.
[0015]
The above method can be suitably applied when the liquid rubber material is liquid silicone rubber.
[0016]
Further, according to the present invention, an injection means having a plunger for measuring and injecting the liquid rubber material from the opening at the tip, and a mold into which the liquid rubber material is injected in a state where the roller shaft is loaded, In a rubber roller injection molding device for molding a rubber roller by injecting a liquid rubber material into a mold,
The injection means is provided with a driving means for moving the plunger, the driving means capable of continuously changing the moving speed of the plunger at minute intervals,
A pressure detecting means for detecting the pressure of the liquid rubber material near the opening of the injection means,
There is provided an injection molding apparatus for a rubber roller, comprising a control device for performing feedback control of the driving means based on the pressure detected by the pressure detecting means.
[0017]
This device can be suitably used when the liquid rubber material is liquid silicone rubber.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of the present invention will be described with reference to FIG.
[0019]
The plunger 103 is connected to a servomotor 110 which is a driving source of the plunger via a ball screw 113 so as to convert a rotational motion into a reciprocating motion.
[0020]
A sensor 111 for measuring the injection pressure of the material is provided at the outlet of the tip of the plunger cylinder 102, and its output is connected to a control device 112 of a servomotor.
[0021]
In operation, after the material is filled in the plunger cylinder in the same manner as in the above-mentioned prior art, injection into the mold is performed by operation of the plunger. At this time, the servo motor is automatically controlled by the control device so as to automatically adjust the number of revolutions so that the pressure measured by the sensor becomes the set injection pressure.
[0022]
The range of the set injection pressure is preferably 2 to 5 MPa, and the set injection pressure is determined by an injection molded product. Particularly when the liquid silicone rubber is used as the liquid rubber material, the above pressure range is preferable.
[0023]
The injection pressure is substantially constant, but the pressure fluctuation at this time is preferably within ± 10%, more preferably within ± 5%. With such a pressure fluctuation range, it is possible to obtain a roller having excellent uniformity in shape and physical properties.
[0024]
When a roller-shaped molded product is molded, the space in the mold is narrow near the injection hole and wide at the portion where the elastic body is formed around the loaded roller shaft as described above.
[0025]
Therefore, if the injection resistance rises and the pressure rises, the rotation speed of the servomotor is decreased to lower the injection pressure, and if the injection resistance falls and the pressure falls, the rotation speed is increased and the injection pressure is increased. In this way, the injection pressure can be kept almost constant by repeating these steps with high precision from the beginning to the end of the injection.
[0026]
Next, another embodiment of the present invention will be described with reference to FIG.
[0027]
In the injection molding apparatus shown in FIG. 1, it is also possible to keep the injection pressure substantially constant without using the sensor 111, and this embodiment relates to this case.
[0028]
The present invention is based on the inventor of the present invention that when the rubber roller is formed, the mold space is elongated and the material is filled in the longitudinal direction, and when the injection is performed at a constant speed from the beginning to the end of the injection, the injection pressure increases almost linearly. This was understood by an examination by the group. In this case, in order to prevent the injection pressure from increasing, the moving speed of the plunger 103 may be continuously reduced at minute intervals (here, the rotational speed of the servomotor may be continuously decreased at minute intervals). For this purpose, it is possible to adopt a servo motor control means which can divide the injection process into, for example, 20 and set the speed for each. The minute interval can be, for example, an interval of 1 second or less.
[0029]
FIG. 2 shows the relationship between the injection speed and the injection pressure in this case (in the case of the above 20 divisions). After the start of the injection, the rotation speed of the motor becomes a predetermined rotation speed in a short time, and the injection speed and the injection pressure rise correspondingly. Thereafter, the motor speed gradually decreases, so that the injection pressure is kept almost constant. Although the injection speed gradually decreases in a stepwise manner when viewed in detail, it is shown by a straight line in FIG. 2 for simplicity. As the operation when changing the moving speed of the plunger by the servo motor, there are a method of temporarily changing the current speed to 0 and then changing to the next speed, and a method of directly changing from the original speed to the next speed. Here, the latter method was adopted. The minute intervals were 0.5 second intervals.
[0030]
In any of the above two embodiments, in forming the developing roller used in the developing device of the electrophotographic apparatus, the variation in the outer diameter over the entire length of the roller is 30 μm or less, the circularity is 5 μm or less, and the electric resistance unevenness is 10 μm or less. The use of this rubber roller in a developing device of an electrophotographic apparatus enabled formation of a high-quality image without image unevenness.
[0031]
In both of the above embodiments, since the injection pressure preferably follows the operation of the plunger with good response, a liquid rubber material having low viscosity and low compressibility is preferably used. From this viewpoint, the present invention is particularly suitable when the liquid rubber material is liquid silicone rubber.
[0032]
【The invention's effect】
As described above, according to the present invention, it has become possible to provide an injection molding method and an injection molding apparatus which are excellent in uniformity in the shape and physical properties of a molded product in molding a rubber roller.
[Brief description of the drawings]
FIG. 1 is a schematic view of an injection device according to a first embodiment of the present invention.
FIG. 2 is a graph showing a relationship between an injection speed and an injection pressure according to a second embodiment of the present invention.
FIG. 3 is a schematic view of a conventional general liquid rubber injection molding apparatus.
FIG. 4 is a schematic view showing a mold used for molding a rubber roller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Upper piece 2 Mold main body 3 Lower piece 3a Injection hole 4 Roller shaft 5 Air gap 101 Injection molding apparatus main body 102 Plunger cylinder 103 Plunger 104 Raw material inlet 105 Backflow prevention valve 106 Static mixer 107, 108 Pipe 109 Shut-off nozzle 110 Servo motor 111 Sensor 112 Servo motor control device 113 Ball screw 301 Injection molding device main body 302 Plunger cylinder 303 Plunger 304 Raw material inlet 305 Backflow prevention valve 306 Static mixer 307, 308 Pipe 309 Shut-off nozzle 310 Plunger driving means 311 Mold

Claims (7)

Using an injection unit having a plunger for measuring and injecting the liquid rubber material from the opening at the tip, the roller shaft is loaded into a mold, and the liquid rubber material is injected into the mold to form a rubber roller. In the rubber roller injection molding method,
A method of injection molding a rubber roller, wherein a liquid rubber material is injected into a mold while keeping the injection pressure of the injection means substantially constant. 2. The method according to claim 1, wherein the injection pressure is kept substantially constant by detecting the injection pressure and performing feedback control of the moving speed of the plunger according to the detected injection pressure. 2. The method according to claim 1, wherein the injection pressure is maintained substantially constant by injecting the liquid rubber while continuously reducing the moving speed of the plunger at minute intervals. Using an injection unit having a plunger for measuring and injecting the liquid rubber material from the opening at the tip, the roller shaft is loaded into a mold, and the liquid rubber material is injected into the mold to form a rubber roller. In the rubber roller injection molding method,
A method of injection molding a rubber roller, wherein the liquid rubber is injected while the moving speed of the plunger is continuously changed at minute intervals. The method according to any one of claims 1 to 4, wherein the liquid rubber material is a liquid silicone rubber. Injection means having a plunger for measuring and injecting the liquid rubber material from the opening at the tip, and a mold into which the liquid rubber material is injected in a state where the roller shaft is loaded, has a liquid in the mold. In a rubber roller injection molding apparatus for molding a rubber roller by injecting a rubber material,
The injection means is provided with a driving means for moving the plunger, the driving means being capable of continuously changing the moving speed of the plunger at minute intervals,
A pressure detecting means for detecting the pressure of the liquid rubber material near the opening of the injection means,
An injection molding apparatus for a rubber roller, comprising: a control device for performing feedback control of the driving means based on the pressure detected by the pressure detecting means. 7. The apparatus according to claim 6, wherein said liquid rubber material is liquid silicone rubber.

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