JP2008044110A - Rubber product molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber product molding method constituted so as to stabilize the density of a rubber material supplied into a cylinder. <P>SOLUTION: The back pressure to a screw 112 retracted by the reaction force of the rubber material 114 supplied into the cylinder 111 at the time of a metering process is set to a predetermined value to perform metering and operation for releasing the addition of injection pressure after the injection pressure is added to the screw 112 in a state that the tip of a nozzle is closed is subsequently repeatedly performed a plurality of times while stepwise enhancing the injection pressure. The ratio of the volume changes of the rubber material 114 in the cylinder 111 at the time of addition of the injection pressure and at the time of release of the injection pressure in the injections of respective stages is calculated from the position of the screw 112 after the injection pressure is added for a predetermined time and the position of the screw 112 after a predetermined time from the release of the injection pressure to evaluate the linearity of the relation between the values of the injection pressure and the values of the ratio of the volume change. In a case that the linearity of a predetermined value or above is recognized the set back pressure value is determined as a normal value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber product molding method for molding a rubber product by injection molding or injection compression molding.

  An injection molding apparatus or injection compression molding apparatus for molding a rubber product includes an injection apparatus for injecting a rubber material into a mold. In addition, this injection device is provided with a cylinder and a screw provided in the cylinder. A molding cycle for molding a rubber product using these molding apparatuses includes a measuring step for supplying a predetermined volume of rubber material into the cylinder.

  Here, in the weighing process, the density of the rubber material supplied into the cylinder is determined by the cylinder heating temperature, the viscosity of the rubber material, the friction between the screw and the cylinder inner wall, the local viscosity variation of the rubber material, It varies depending on various factors such as the bite of the dough. Such a variation in the density of the rubber material causes variations in the amount of the rubber material injected into the mold.

  The variation in the amount of the rubber material injected into the mold is a factor that deteriorates the quality of the rubber product to be molded. In particular, if the amount of the rubber material injected into the mold is small, poor filling occurs. Therefore, it is necessary to suppress such fluctuations in the density of the rubber material as much as possible.

  In order to stabilize the density of the rubber material supplied into the cylinder during the metering process, it is necessary to make the back pressure value appropriate for the screw retreating by the reaction force of the rubber material supplied into the cylinder during the metering process. One of the important elements.

  That is, if this back pressure value is too low, the density of the rubber material supplied into the cylinder will be low, the amount of rubber material injected into the mold will be less than desired, and filling failure will occur. End up. If the back pressure is too high, the rubber material may leak from the nozzle at the tip of the cylinder, the friction between the rubber material and the cylinder inner wall surface will increase, and the fabric may be burnt. Inconveniences such as a long time required for the process occur.

  In this way, it is important to make the back pressure value appropriate, but the method for setting the back pressure value is not well established, and the fact is that it relies on experience and effort through repeated adjustments. is there. However, repeated adjustments to make the back pressure value appropriate, such as having to adjust the amount of suckback each time the back pressure value is changed, are very time consuming and time consuming. Further, it may not always be said that the density distribution of the rubber material supplied into the cylinder becomes uniform just because the back pressure value is made appropriate.

In addition, as a related technique, there exists what was disclosed by patent document 1-patent document 11. FIG.
Japanese Patent Laid-Open No. 10-230538 JP 2001-239565 A JP 2000-15681 A JP 2004-154994 A Japanese Patent No. 3053518 Japanese Patent No. 3440406 Japanese Patent No. 3280792 JP-A-1-280523 JP 2000-167896 A JP-A-7-164492 JP 11-254495 A

  An object of the present invention is to provide a method for molding a rubber product in which the density of a rubber material supplied into a cylinder is stabilized.

  The present invention employs the following means in order to solve the above problems.

That is, the method for molding a rubber product of the present invention includes:
In a rubber product molding method, a rubber material is injected into a mold from a nozzle at the tip of a cylinder using an injection device including a cylinder and a screw provided in the cylinder, and the rubber product is molded by mold molding.
A metering step of supplying a rubber material into the cylinder;
An injection step of injecting a rubber material into the mold after the weighing step,
After measuring by setting the back pressure against the screw retreating by the reaction force of the rubber material supplied into the cylinder during the measuring process to a predetermined value, the nozzle tip is blocked and injected into the screw. The operation of releasing the injection pressure after applying the pressure is repeated a plurality of times while gradually increasing the injection pressure,
The rubber material in the cylinder at the time of injection pressure addition and release of injection pressure at each stage of injection pressure from the position of the screw after release of injection pressure after a predetermined time after releasing injection pressure for a predetermined time The volume change ratio of
Evaluate the linearity of the relationship between the value of the injection pressure and the ratio of volume change at each stage,
When linearity exceeding a predetermined value is recognized, the set back pressure value is determined as a normal value.

  According to the present invention, since the measurement is performed with the back pressure value being appropriate, the density of the rubber material supplied into the cylinder can be stabilized. That is, as the density distribution of the rubber material in the cylinder becomes uniform, the relationship between the value of each injection pressure and the value of the specific volume change becomes linear. In the present invention, the linearity of these relationships is evaluated, and the measurement is performed using the back pressure value when a linearity of a predetermined level or more is recognized. It can be stabilized.

The method for molding a rubber product of the present invention includes:
In a rubber product molding method, a rubber material is injected into a mold from a nozzle at the tip of a cylinder using an injection device including a cylinder and a screw provided in the cylinder, and the rubber product is molded by mold molding.
A metering step of supplying a rubber material into the cylinder;
An injection step of injecting a rubber material into the mold after the weighing step,
After measuring by setting the back pressure against the screw retreating by the reaction force of the rubber material supplied into the cylinder during the measuring process to a predetermined value, the step is performed on the screw with the nozzle tip closed. To increase the injection pressure
Evaluate the linearity of the relationship between each injection pressure that is gradually increased and the position of the screw after each injection pressure has been applied for a predetermined time,
When linearity exceeding a predetermined value is recognized, the set back pressure value is determined as a normal value.

  Also according to the present invention, since the measurement is performed with the back pressure value being appropriate, the density of the rubber material supplied into the cylinder can be stabilized. That is, as the density distribution of the rubber material in the cylinder becomes more uniform, the relationship between each injection pressure that is gradually increased and the position of the screw after each injection pressure is applied for a predetermined time becomes linear. In the present invention, the linearity of these relationships is evaluated, and the measurement is performed using the back pressure value when a linearity of a predetermined level or more is recognized. It can be stabilized.

Here, in the determination of the normal value of the back pressure during the above weighing process,
The rubber material is supplied into the cylinder with the tip of the nozzle open, and the back pressure in a state in which the rubber material leaks slightly from the tip of the nozzle is temporarily set as an initial value.
It is good to gradually increase the value from the initial value until linearity of a predetermined value or more is recognized.

  Thereby, the value of the back pressure can be set within a proper range and as small as possible.

  In addition, the regular value of the back pressure may be determined again each time the type of rubber material is changed.

The method for molding a rubber product of the present invention includes:
In a rubber product molding method, a rubber material is injected into a mold from a nozzle at the tip of a cylinder using an injection device including a cylinder and a screw provided in the cylinder, and the rubber product is molded by mold molding.
A metering step of supplying a rubber material into the cylinder;
An injection step of injecting a rubber material into the mold after the weighing step,
The metering process starts at the timing when the rubber material of the gate part of the mold is cured after the injection process,
A compression step of compressing the rubber material in the cylinder by applying a pressure to the screw so that the hardened rubber material of the gate portion does not break after the metering step is completed;
Providing a compression release step for releasing the pressure in the compression step;
The position of the screw after the decompression process is used as a reference position in the next injection process, and in the injection process, control is performed to advance the screw by a fixed amount from the reference position.

  According to the present invention, by providing the compression step, the sparse part of the rubber material supplied into the cylinder in the weighing step can be reduced, and the density of the rubber material in the cylinder can be stabilized.

  In addition, said each structure can be employ | adopted combining as much as possible.

  As described above, according to the present invention, it is possible to stabilize the density of the rubber material supplied into the cylinder.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

(Example 1)
With reference to FIGS. 1-7, the molding method of the rubber product which concerns on Example 1 of this invention is demonstrated.

<Molding device>
With reference to FIG. 1, the shaping | molding apparatus which performs the shaping | molding method of the rubber product which concerns on Example 1 of this invention is demonstrated. The molding apparatus in the present embodiment is an apparatus applicable to injection molding or injection compression molding. Since the molding apparatus itself is a known technique, the outline is briefly described here. FIG. 1 is a schematic configuration diagram of a molding apparatus that performs a method of molding a rubber product according to Embodiment 1 of the present invention. In FIG. 1, the configuration of the hydraulic circuit is mainly shown.

  The molding apparatus includes a molding apparatus main body 100, a control unit 200 that performs various controls, and a hydraulic circuit unit 300.

  The molding apparatus main body 100 includes an injection apparatus 110 that injects a rubber material 114 and a mold 120 that molds a rubber product. The injection device 110 includes a cylinder 111 that can perform heating, a screw 112 provided in the cylinder 111, and a piston cylinder 113 that houses a piston portion 112a provided near the rear end of the screw 112. Yes. In the present embodiment, a blocking mechanism 130 is provided for closing the tip of the nozzle 111 a provided at the tip of the cylinder 111.

  The control unit 200 includes a CPU 201 that performs various types of control, an A / D converter 202 that converts analog signals into digital signals, an I / O 203 that performs input processing and output processing, and a D that converts digital signals into analog signals. / A converter 204.

  The hydraulic circuit unit 300 includes a back pressure hydraulic circuit unit 310 for controlling the back pressure against the screw 112 retracted by the reaction force of the rubber material 114 supplied into the cylinder 111 in the metering step, and the screw 112 in the injection step. An injection pressure hydraulic circuit section 320 for controlling the injection pressure for advancing the motor and a rotation control hydraulic circuit section 330 for controlling the rotation of the motor 331 for rotating the screw 112 are provided.

  With the above configuration, the control unit 200 drives the screw 112 and the like by controlling the hydraulic circuit unit 300 based on various input signals.

<Molding cycle>
The molding cycle will be described with reference to FIG. Since a molding cycle in injection molding or injection compression molding is a known technique, a brief description will be given here. FIG. 2 is an explanatory view showing a general molding cycle. In FIG. 2, (A) shows a weighing process, and (B) shows that the mold clamping is completed after the cylinder 111 of the injection apparatus 110 is separated from the mold 120, the mold is opened, and the rubber product is taken out. (C) shows a state in which the nozzle 111a at the tip of the cylinder 111 of the injection device 110 is brought into contact with the mold 120 after the mold clamping is completed, and (D) shows an injection process.

<< Weighing process (FIG. 2A) >>
In the measuring step, the rubber material 114 is supplied into the cylinder 111. During the metering, the screw 112 moves backward by the reaction force of the rubber material 114 supplied while rotating. Then, the screw 112 is controlled to stop when it is retracted to a predetermined position. Thus, since the rubber material 114 is supplied into the cylinder 111 while the screw 112 rotates, the rubber material 114 supplied into the cylinder 111 is plasticized and kneaded.

  Here, during the measurement, the back pressure is controlled by the back pressure hydraulic circuit section 310 so that the back pressure is applied to the screw 112 that moves backward by the reaction force of the rubber material 114 as described above.

  In addition, after the measurement process is completed, a suck back is performed in which the screw 112 is slightly retracted so that the rubber material 114 does not leak from the nozzle 111a of the cylinder 111.

<< After weighing process-Die opening-Clamping (Fig. 2 (B)) >>
After completion of the suck back, the cylinder 111 is separated from the mold 120, the mold 120 is opened (mold opening), and the rubber product as a molded product is taken out from the mold 120. This process is not shown in FIG. After removing the rubber product, the mold is clamped. Here, in FIG. 2, 121 indicates a cavity for molding a rubber product, and 122 indicates a gate portion.

<< Clamping to Injection Process (FIGS. 2C and 2D) >>
After the mold clamping is completed, the nozzle 111a at the tip of the cylinder 111 of the injection device 110 is again brought into contact with the mold 120 (FIG. 2C). The rubber material 114 is injected into the mold 120 by rotating the screw 112 while applying the injection pressure to the screw 112 by the hydraulic circuit 320 for injection pressure (FIG. 2D). ).

  Here, generally, after the measuring step, the position of the screw 112 before the suck back is set as a reference position, and the control to advance the screw 112 by a predetermined amount from the reference position is performed. Thus, the rubber material 114 is injected.

  After the injection process, the measurement is performed again at the timing when the rubber material 114 of the gate portion 122 in the mold 120 is cured (so-called gate seal).

<Determination procedure of back pressure value>
As described in the background art, in order to stabilize the density of the rubber material 114 supplied into the cylinder 111, it is important that the value of the back pressure in the measurement process is appropriate. A procedure for determining a normal value of the back pressure in the measuring step will be described with reference to FIGS. The normal value of the back pressure is re-determined every time the type of the rubber material 114 is changed, and also when the occurrence rate of defective products of the molded rubber product increases with continuous operation. Determine again.

  3 and 4 are schematic cross-sectional views showing a mechanism for closing the nozzle tip of the cylinder. FIG. 3 shows a case where a metal flat plate is used, and FIG. 4 shows a case where a shut-off mechanism is used. FIG. 5 is a graph showing the relationship between the injection pressure and the screw position in Example 1 of the present invention. 6 and 7 are graphs showing the relationship between the injection pressure and the volume change ratio (specific volume) in Example 1 of the present invention.

  First, a rubber material is supplied into the cylinder 111 with the tip of the nozzle 111a of the cylinder 111 opened. Then, the back pressure in a state where the rubber material 114 leaks a little from the nozzle 111a is temporarily set as the initial value P0. This initial value P0 corresponds to the sum of the frictional force between the screw 112 and the inner wall surface of the cylinder 111 and the resistance force due to the flow resistance of the rubber material 114 at the nozzle 111a, and is the minimum necessary for measurement. Pressure.

  Then, weighing is performed in a state where the back pressure is set to the initial value P0, and the screw 112 is stopped when the screw 112 is retracted to a preset position.

  Next, the tip of the nozzle 111a of the cylinder 111 is closed. Various mechanisms for closing the tip of the nozzle 111a can be used. Here, two types of mechanisms will be described with reference to FIGS. 3 and 4.

  FIG. 3 shows a mechanism using a metal flat plate 131. 3A shows a state where the tip of the nozzle 111a is opened, and FIG. 3B shows a state where the tip of the nozzle 111a is closed. The metal flat plate 131 is configured to be manually movable to a position for opening and closing a tip of the nozzle 111a. Thus, according to the mechanism using the metal flat plate 131, the tip of the nozzle 111a can be closed by moving the metal flat plate 131 manually.

  FIG. 4 shows a shut-off mechanism. 4A shows a state in which the tip of the nozzle 111a is opened, and FIG. 4B shows a state in which the tip of the nozzle 111a is closed. In the case of this mechanism, a valve body 132 configured to be rotatable is provided inside the nozzle 111a. By controlling the rotation of the valve body 132, the tip of the nozzle 111a can be opened or closed.

  In this manner, after applying the injection pressure to the screw 112 in a state where the tip of the nozzle 111a is closed using some mechanism, a plurality of operations to release the injection pressure are performed while increasing the injection pressure stepwise. Repeat once.

  Here, the injection pressure is applied to the screw 112 for a predetermined time while maintaining a constant pressure at each stage. That is, since the screw 112 receives the repulsive force of the rubber material 114, a certain amount of time is required until the screw 112 stops after a certain injection pressure is applied. Therefore, the injection pressure is applied to the screw 112 while keeping the injection pressure constant at each stage for the time necessary for the screw 112 to stop (for example, 10 to 20 seconds). However, if the pressure is uniformly applied to the screw 112 for the same time while maintaining a constant pressure in each stage, time may be wasted. Therefore, the volume change rate of the rubber material 114 in the screw 112 may be detected, and the addition of the injection pressure may be canceled when the volume change rate falls below a predetermined value. However, even in this case, the time limit is set, and when the time limit elapses, the addition of the injection pressure is canceled even if the volume change rate is not lower than the predetermined value. Better.

  At each stage, the position of the screw 112 after the injection pressure is applied for a predetermined time is stored.

  Further, in each stage, when the injection pressure is released, the position of the screw 112 after a predetermined time (for example, 10 to 20 seconds) after releasing the pressure is similarly stored. The reason for memorizing the position of the screw 112 after a predetermined time has elapsed is that it takes a certain amount of time for the screw 112 to come to rest even when the pressure is released.

  In this way, after the injection pressure is applied for a predetermined time, the operation of releasing the injection pressure is performed stepwise (desirably until the injection pressure reaches a predetermined upper limit (200 MPa in this embodiment)). Is repeated while increasing to 10 steps or more).

FIG. 5A shows a case where measurement is performed in a state where the back pressure is set to the initial value P0, and thereafter, the operation of repeatedly adding the injection pressure and releasing the injection pressure is repeated as described above. This shows how the injection pressure and the position of the screw 112 change.

  In FIG. 5A, P indicates the injection pressure, S indicates the position of the screw 112 after the injection pressure is applied for a predetermined time, and S ′ indicates the position of the screw 112 after the predetermined time since the injection pressure is released. Is shown. Further, among the lower right subscripts in each symbol, 0 on the left side indicates that the back pressure was the initial value P0. Also, among the lower right subscripts in each symbol, the number on the right side indicates the number of stages in the injection pressure that is gradually increased.

  Then, from the screw position S after the injection pressure P is applied for a predetermined time in each stage and the screw position S ′ after the injection pressure is released, the injection pressure is applied at the injection pressure P in each stage. A ratio (specific volume) of volume change of the rubber material 114 in the cylinder 111 when the injection pressure is released is obtained. Note that neither the cylinder 111 nor the screw 112 changes in shape, and the rubber material 114 is filled in the region between the cylinder 111 and the screw 112 without any gap. From this position, the volume of the rubber material 114 is determined.

  Here, the ratio of volume change is obtained from (V−V ′) ÷ V. V is the volume of the rubber material 114 when the position of the screw 112 is S, and V ′ is the volume of the rubber material 114 when the position of the screw 112 is S ′.

  Then, the linearity of the relationship between the value of the injection pressure and the ratio of volume change (specific volume) at each stage is evaluated. 6 and 7 are graphs plotting the values of the injection pressures and the ratios of volume changes. The graph shown by A in FIG. 6 corresponds to the case where the back pressure is the initial value P0.

  The evaluation of linearity is not particularly limited, but a preferable example is a correlation coefficient. The determination of the linearity may be set as appropriate. When the correlation coefficient is used for evaluation, for example, when the correlation coefficient is 0.9 or more, it can be recognized as a straight line.

  When a linearity exceeding a predetermined value is recognized, the set back pressure value (initial value P0) is determined as a normal value. In the case of the present embodiment, when the back pressure value is the initial value P0, the ratio between the value of each injection pressure and the volume change becomes a curve as shown in the graph A in FIG. Therefore, the initial value P0 cannot be adopted as a normal back pressure.

  Here, the reason why the ratio between the value of each injection pressure and the volume change becomes a curve will be briefly described. As described above, the initial value P0 is the minimum pressure required for measurement, and is usually lower than the appropriate back pressure value. Therefore, the rubber material 114 supplied to the cylinder 111 at the time of measurement has a non-uniform density distribution and has many sparse portions. When the injection pressure is applied to the screw 112 with the tip of the nozzle 111a of the cylinder 111 closed after measurement, the amount of movement of the screw 112 increases as the sparse part increases. Therefore, when the injection pressure is applied to the screw 112 while increasing the injection pressure stepwise, the moving amount of the screw 112 is initially large, and the moving amount decreases as the sparse part decreases. Therefore, when the back pressure value is a low initial value P0, the ratio of each injection pressure value to the volume change becomes a curve as shown in the graph of FIG. 6A.

  Then, as in the case of the present embodiment, when the initial value P0 does not show a linearity of a certain level or more in the relationship between the injection pressure value and the volume change ratio (specific volume) at each stage. The rubber material 114 in the cylinder 111 is discharged.

After the rubber material 114 is discharged, the back pressure value is set to a value P1 (P1 = P0 + ΔP) set higher by ΔP than the initial value P0, and the measurement is performed again. Here, ΔP is set to about 1% of the maximum hydraulic pressure output of the apparatus in consideration of both control resolution and work efficiency of the forming apparatus.

  Then, as in the case where the back pressure is set to the initial value P0, the operation of releasing the injection pressure after the injection pressure is applied to the screw 112 with the tip of the nozzle 111a closed is performed. Repeat several times while increasing the pressure stepwise. Similarly to the case where the back pressure is set to the initial value P0, the position of the screw 112 after the injection pressure is applied for a predetermined time in each stage and the position of the screw 112 after the predetermined time after the injection pressure is released. Is stored.

  FIG. 5 (B) shows the injection in the case where the measurement is performed with the back pressure set to P1, and then the operation of repeatedly adding the injection pressure and releasing the injection pressure is repeated as described above. This shows how the pressure and the position of the screw 112 change.

  The meanings of the numerals in FIG. 5B and the numbers on the right side of the subscripts at the lower right of the signs are the same as those shown in FIG. 5A in which the back pressure is set to the initial value P0. is there. Also, 1 on the left side of the subscript means that the back pressure was P1 (ΔP was added once for the initial value P0).

  Similarly to the case where the back pressure is set to the initial value P0, the ratio (specific volume) of the volume change of the rubber material 114 in the cylinder 111 when the injection pressure is applied and when the injection pressure is released at each stage of the injection pressure P is set. Determine the linearity of the relationship between the value of injection pressure and the ratio of volume change at each stage. When linearity exceeding a predetermined value is recognized, the set back pressure value P1 is determined as a normal value.

  The graph shown by B in FIG. 6 corresponds to the case where the back pressure value is P1. In the case of the present embodiment, as shown in this graph, even when the back pressure value is P1, the ratio between the value of each injection pressure and the volume change becomes a curve. Therefore, P1 cannot be adopted as a regular back pressure.

  Thus, when P1 cannot be adopted as a regular back pressure, the back pressure value is set to a value P2 (P2 = P1 + ΔP = P0 + 2 × ΔP) which is set higher than P1 by P1. Perform the work and evaluation.

  As described above, the value of the back pressure is increased by ΔP until it is recognized that the linearity of the relationship between the value of the injection pressure and the volume change ratio at each stage is not less than a predetermined value.

  FIG. 5 (C) shows the injection in the case where the measurement is performed with the back pressure set to Pi, and then the operation of repeatedly adding the injection pressure and releasing the injection pressure is repeated as described above. This shows how the pressure and the position of the screw 112 change.

  The meanings of the numerals in FIG. 5C and the numbers on the right side of the subscripts at the bottom right of each sign are the same as those shown in FIG. 5A in which the back pressure is set to the initial value P0. is there. Further, i on the left side of the subscript means that the back pressure is Pi (ΔP is added i times to the initial value P0).

  Further, the graph C in FIG. 6 corresponds to the case where the back pressure value is Pi.

As is apparent from the graph shown in FIG. 6, the higher the back pressure value in the measuring step, the later the operation of releasing the injection pressure after adding the injection pressure to the screw 112, When the injection pressure is repeatedly increased a plurality of times while increasing the injection pressure stepwise, the relationship between the injection pressure value and the volume change ratio in each step is gradually increased in linearity.

  FIG. 7 shows the relationship between the value of the injection pressure and the ratio of volume change at each stage when linearity of a predetermined value or more (here, the correlation coefficient is 0.9 or more) is recognized. .

  According to the above procedure, when the linearity exceeding a predetermined value is recognized in the relationship between the injection pressure value and the volume change ratio in each stage, the set back pressure value is determined as a normal value. If the measurement is performed with the back pressure value determined in this way, the rubber material 114 supplied to the cylinder 111 at the time of measurement has almost no sparse portion, and the density distribution becomes uniform. Therefore, the density of the rubber material 114 supplied into the cylinder 111 can be stabilized. Further, according to this embodiment, in order to obtain an appropriate back pressure value while gradually increasing the back pressure value from the initial value P0 that is the minimum necessary pressure for measurement, the back pressure value is It can be set within a proper range and as small as possible.

<Excellent points of this embodiment>
As described above, according to the present embodiment, it is possible to obtain an appropriate value for the back pressure value without depending on experience and labor by repeated adjustment. Although an appropriate back pressure value can be obtained by manual calculation, it is preferable to obtain it automatically by using a computer or a control device.

  Further, the density of the rubber material 114 supplied into the cylinder 111 can be stabilized by setting the back pressure value to the value determined by the above procedure and performing the measurement. Thereby, in the injection process, the amount of the rubber material 114 injected into the mold 120 is stabilized, and the quality of the molded rubber product can be stabilized.

  In addition, since the back pressure value can be set within the proper range and as small as possible, the occurrence of drooling that causes the rubber material to leak from the nozzle at the tip of the cylinder is suppressed, and the rubber material and cylinder It is possible to suppress the friction with the inner wall surface from increasing and to shorten the time required for the weighing process as much as possible.

(Example 2)
FIG. 8 shows a second embodiment of the present invention. In the present embodiment, a case will be described in which the procedure for determining the back pressure value described in the first embodiment is simplified. Since other aspects are the same as those in the first embodiment, the description thereof is omitted.

  In the first embodiment, in the procedure for determining the value of the back pressure, after adding the injection pressure to the screw 112 in a state where the tip of the nozzle 111a is closed after the measurement, the operation of releasing the injection pressure is performed. It is repeated several times while increasing the injection pressure stepwise, and the value of the injection pressure at each step is determined from the ratio of the volume change of the rubber material 114 in the cylinder 111 when the injection pressure is applied and when the injection pressure is released at each step. The case where the linearity of the relationship between the volume ratio and the volume change ratio (specific volume) is evaluated has been described.

  In contrast, in this embodiment, the operation of canceling the addition of the injection pressure is omitted, and the linearity of the relationship between each injection pressure that is gradually increased and the position of the screw 112 after each injection pressure is added for a predetermined time. The case where is directly evaluated will be described.

FIG. 8 is a graph showing the relationship between the injection pressure and the screw position in Example 2 of the present invention. 8A corresponds to FIG. 5A described in the first embodiment, FIG. 8B corresponds to FIG. 5B, and FIG. 8C corresponds to FIG. 5C. To do. The meaning of each symbol in FIG. 8 and the subscript at the lower right of each symbol is the same as in FIG.

  As can be seen from FIG. 8, in this embodiment, in the determination procedure of the back pressure value, the injection pressure is increased stepwise with respect to the screw 112 with the tip of the nozzle 111a closed after measurement. Unlike the case of the first embodiment, the operation for releasing the addition of the injection pressure is not performed. However, the point at which the injection pressure is applied to the screw 112 for a predetermined time while maintaining a constant pressure at each stage, and the position of the screw 112 after the injection pressure is applied for a predetermined time at each stage are stored. This is the same as in the case of the first embodiment.

  In the present embodiment, unlike the case of the first embodiment, the injection pressures and the injection pressures that are increased in stages as shown in FIG. The linearity of the relationship with the screw position after addition is directly evaluated. And when the linearity more than predetermined is recognized, the value of the set back pressure is determined as a normal value.

  Note that the point of increasing the back pressure value by ΔP from the initial value P0 until a linearity equal to or greater than the predetermined value is recognized, and the method for evaluating the linearity is as described in the first embodiment.

  As described above, an appropriate back pressure value can be obtained also in this embodiment. Therefore, also in the case of the present embodiment, the same effect as in the first embodiment can be obtained. In addition, since the error which generate | occur | produced in each step | paragraph can be once removed if the addition of injection pressure is cancelled | released at each step like the said Embodiment 1, the accuracy in the case of the said Embodiment 1 is higher. However, in this embodiment, the procedure for determining an appropriate back pressure value can be simplified to the extent that there is no operation for canceling the addition of the injection pressure.

(Example 3)
9 to 11 show Embodiment 3 of the present invention. In this embodiment, a case where a compression process and a decompression process are added after the weighing process in the molding cycle will be described. In addition, since it is as having demonstrated the said Example 1 regarding the shaping | molding apparatus, the description is abbreviate | omitted here.

  FIG. 9 is an explanatory view showing a molding cycle according to Example 3 of the present invention. FIG. 10 is a graph showing the positional relationship between the elapsed time and the screw in a general molding cycle. FIG. 11 is a graph showing the positional relationship between the elapsed time and the screw in the molding cycle according to Example 3 of the present invention. In FIG. 11, a partly enlarged one is also attached.

  A molding cycle according to Example 3 of the present invention will be described. (A), (B), (C), and (D) in FIG. 9 are the same as (A), (B), (C), and (D) in FIG. 2 described above. That is, (A) shows the weighing process, and (B) shows the state in which the mold clamping is completed after the cylinder 111 of the injection device 110 is separated from the mold 120, the mold is opened and the rubber product is taken out. (C) shows the state where the nozzle 111a at the tip of the cylinder 111 of the injection device 110 is brought into contact with the mold 120 after the mold clamping is completed, and (D) shows the injection process. Since these details are as having demonstrated in the said Example 1, the description is abbreviate | omitted.

  In addition, in FIG. 10, the elapsed time in the general shaping | molding cycle and the positional relationship of a screw are shown. In FIG. 10, a period S corresponds to a weighing process, a period T corresponds to a process in which sackback is performed, and a period U corresponds to an injection process. Here, in the injection process, the position of the screw 112 after the weighing process and before the suck back is set as a reference position (H1 in FIG. 10), and the screw 112 is controlled to advance by a fixed amount from the reference position. .

  However, in the case of a general molding cycle, the density distribution of the rubber material 114 supplied to the cylinder 111 at the time of weighing may be non-uniform (there may be a sparse part). Therefore, when the position of the screw 112 after the weighing process is set as the reference position, the amount of the rubber material 114 injected into the mold 120 in the injection process may be insufficient.

  Therefore, in this embodiment, a compression process and a decompression process are added after the weighing process, and the position of the screw 112 after the decompression process and before sucking back is used as a reference position in the next injection process. The above problems were solved. This point will be described in more detail.

  In the present embodiment, after the metering step, a little pressure oil is once supplied to the piston cylinder 113, the injection pressure is applied, and the screw 112 is advanced a little to compress the rubber material 114 supplied in the cylinder 111. (Step A-1 in FIG. 9). The injection pressure applied to the screw 112 in this compression step is set to a pressure that does not break the hardened rubber material (gate seal) in the gate portion. Moreover, it is desirable to set the pressurization time in this compression process so short that it does not affect the molding cycle.

  After the injection pressure is applied to the screw 112 for a certain period of time, in order to relieve the internal pressure of the rubber material 114, the injection pressure is released and the compression is released (compression release process (FIG. 9 (A- See 2))).

  The subsequent steps are the same as in the case of the general molding cycle described in Example 1 above.

  FIG. 11 shows the positional relationship between the elapsed time and the screw in the molding cycle according to Example 3 of the present invention. In FIG. 11, the period S corresponds to the weighing process, the period T corresponds to the process of sucking back, and the period U corresponds to the injection process, as in FIG. In FIG. 11, a period V corresponds to the compression process, and a period W corresponds to the compression release process.

  In the case of the present embodiment, in the injection process, the position of the screw 112 after the compression release process and before the suck back is set as a reference position (H2 in FIG. 11), and the screw 112 is fixed by a certain amount from this reference position. Control to move forward. In this embodiment, in order to perform this control, it is necessary to memorize the position of the screw 112 after the compression release step and before sucking back each time. That is, in the present embodiment, the position where the screw 112 is stopped in the weighing process is a predetermined position every time, whereas the reference position in the injection process is changed every time.

  As described above, according to the present embodiment, by providing the compression process, the sparse part of the rubber material 114 supplied into the cylinder 111 in the weighing process is reduced, and the density of the rubber material 114 in the cylinder 111 is reduced. Can be stabilized. Thereby, in the injection process, the amount of the rubber material 114 injected into the mold 120 is stabilized, and the quality of the molded rubber product can be stabilized.

  Moreover, the rubber material 114 in the cylinder 111 is further set by setting the value of the back pressure in the measuring step in the present embodiment to a value determined using the method shown in the first embodiment or the second embodiment. The density of can be stabilized.

(Others (About evaluation of linearity))
In the invention according to claim 1 and the first embodiment described above, the linearity of the relationship between the value of the injection pressure and the ratio of the volume change is evaluated by converting the position of the screw into the volume of the rubber material. explained. However, in the invention according to claim 1 and Example 1, it is possible to evaluate the linearity of the relationship between the value of the injection pressure and the change ratio of the screw position without converting to the volume of the rubber material. Needless to say. The invention according to claim 1 includes such a case. On the other hand, in the invention according to claim 2 and Example 2 described above, the case where the linearity of the relationship between the value of the injection pressure and the position of the screw is evaluated has been described. However, in the invention according to claim 2 and the second embodiment, the linearity of the relationship between the value of the injection pressure and the ratio of the volume of the rubber material is evaluated by converting the position of the screw into the volume of the rubber material. It goes without saying that it is also good. The invention according to claim 2 includes such a case.

  Generally, even when the screw is stopped at the bottom dead center, the rubber material remains in the cylinder. In addition, the ratio of the screw position and the volume of the rubber material in the cylinder may not necessarily have a linear relationship. In these cases, if linearity is evaluated based on the value of the injection pressure and the position of the screw without converting to the volume of the rubber material, an error may occur. Therefore, in such a case, it is desirable to convert to the volume of the rubber material. On the other hand, when such an error does not occur or when the error is not a problem, it is not necessary to convert the volume of the rubber material. Thus, whether or not to convert to the volume of the rubber material is an actual product problem for avoiding an error. Therefore, even if the linearity is evaluated based on the position of the screw, or the linearity is evaluated based on the conversion from the position of the screw to the volume of the rubber material, the technical idea is Within the same range.

FIG. 1 is a schematic configuration diagram of a molding apparatus that performs a method of molding a rubber product according to Embodiment 1 of the present invention. FIG. 2 is an explanatory view showing a general molding cycle. FIG. 3 is a schematic cross-sectional view showing a mechanism for closing the nozzle tip of the cylinder. FIG. 4 is a schematic cross-sectional view showing a mechanism for closing the nozzle tip of the cylinder. FIG. 5 is a graph showing the relationship between the injection pressure and the screw position in Example 1 of the present invention. FIG. 6 is a graph showing the relationship between the injection pressure and the volume change ratio (specific volume) in Example 1 of the present invention. FIG. 7 is a graph showing the relationship between the injection pressure and the volume change ratio (specific volume) in Example 1 of the present invention. FIG. 8 is a graph showing the relationship between the injection pressure and the screw position in Example 2 of the present invention. FIG. 9 is an explanatory view showing a molding cycle according to Example 3 of the present invention. FIG. 10 is a graph showing the positional relationship between the elapsed time and the screw in a general molding cycle. FIG. 11 is a graph showing the positional relationship between the elapsed time and the screw in the molding cycle according to Example 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Molding apparatus main body 110 Injection apparatus 111 Cylinder 111a Nozzle 112 Screw 112a Piston part 113 Piston cylinder 114 Rubber material 120 Mold 121 Cavity 122 Gate part 130 Shut-off mechanism 131 Metal flat plate 132 Valve body 200 Control part 201 CPU
202 A / D converter 203 I / O
204 D / A converter 300 Hydraulic circuit section 310 Back pressure hydraulic circuit section 320 Injection pressure hydraulic circuit section 330 Rotation control hydraulic circuit section 331 Motor

Claims (5)

In a rubber product molding method, a rubber material is injected into a mold from a nozzle at the tip of a cylinder using an injection device including a cylinder and a screw provided in the cylinder, and the rubber product is molded by mold molding.
A metering step of supplying a rubber material into the cylinder;
An injection step of injecting a rubber material into the mold after the weighing step,
After measuring by setting the back pressure against the screw retreating by the reaction force of the rubber material supplied into the cylinder during the measuring process to a predetermined value, the nozzle tip is blocked and injected into the screw. The operation of releasing the injection pressure after applying the pressure is repeated a plurality of times while gradually increasing the injection pressure,
The rubber material in the cylinder at the time of injection pressure addition and release of injection pressure at each stage of injection pressure from the position of the screw after release of injection pressure after a predetermined time after releasing injection pressure for a predetermined time The volume change ratio of
Evaluate the linearity of the relationship between the value of the injection pressure and the ratio of volume change at each stage,
A method for molding a rubber product, characterized in that when a linearity exceeding a predetermined value is recognized, a set back pressure value is determined as a normal value. In a rubber product molding method, a rubber material is injected into a mold from a nozzle at the tip of a cylinder using an injection device including a cylinder and a screw provided in the cylinder, and the rubber product is molded by mold molding.
A metering step of supplying a rubber material into the cylinder;
An injection step of injecting a rubber material into the mold after the weighing step,
After measuring by setting the back pressure against the screw retreating by the reaction force of the rubber material supplied into the cylinder during the measuring process to a predetermined value, the step is performed on the screw with the nozzle tip closed. To increase the injection pressure
Evaluate the linearity of the relationship between each injection pressure that is gradually increased and the position of the screw after each injection pressure has been applied for a predetermined time,
A method for molding a rubber product, characterized in that when a linearity exceeding a predetermined value is recognized, a set back pressure value is determined as a normal value. In determining the normal value of back pressure during the weighing process,
The rubber material is supplied into the cylinder with the tip of the nozzle open, and the back pressure in a state in which the rubber material leaks slightly from the tip of the nozzle is temporarily set as an initial value.
The method for molding a rubber product according to claim 1 or 2, wherein the value is gradually increased from the initial value until linearity of a predetermined value or more is recognized.   The method for molding a rubber product according to claim 1, 2 or 3, wherein the regular value of the back pressure is determined again each time the type of the rubber material is changed. In a rubber product molding method, a rubber material is injected into a mold from a nozzle at the tip of a cylinder using an injection device including a cylinder and a screw provided in the cylinder, and the rubber product is molded by mold molding.
A metering step of supplying a rubber material into the cylinder;
An injection step of injecting a rubber material into the mold after the weighing step,
The metering process starts at the timing when the rubber material of the gate part of the mold is cured after the injection process,
A compression step of compressing the rubber material in the cylinder by applying a pressure to the screw so that the hardened rubber material of the gate portion does not break after the metering step is completed;
Providing a compression release step for releasing the pressure in the compression step;
A method for molding a rubber product, wherein the position of the screw after the decompression step is used as a reference position in the next injection step, and in the injection step, control is performed to advance the screw by a fixed amount from the reference position.

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