Patent Description:
An inflation molding device that extrudes a melted molding material in a film shape from a discharge port of a die and that solidifies the molding material with cooling air from a cooling unit to mold into a film is known. In the related art, a film molding device that keeps a film thickness within a target range by adjusting the width of a discharge port and the air speed and air temperature of cooling air from a cooling unit is proposed.

The present invention is devised in such a situation, and one of exemplary objects of an aspect thereof is to provide an inflation molding device having an improved commercial value.

According to an aspect of the present invention, in order to solve the problems, there is provided an inflation molding device including a viscosity estimation unit that estimates a viscosity of a molding material discharged in a substantially cylindrical shape from a die, a temperature identification unit that identifies a temperature of the molding material, and a parameter estimation unit that estimates a viscosity parameter of the molding material based on the viscosity estimated by viscosity estimation and the temperature detected by a temperature detection unit.

In addition, according to another aspect of the present invention, there is provided an inflation molding device. The device includes a stress estimation unit that estimates a stress distribution of a molding material discharged in a substantially cylindrical shape from a die and a viscosity estimation unit that estimates a viscosity distribution of the molding material based on the stress distribution estimated by the stress estimation unit.

Any combination of the components described above and a combination obtained by switching the components and expressions of the present invention between methods, devices, and systems are also effective as an aspect of the present invention.

According to the present invention, the inflation molding device having an improved commercial value can be provided.

The present embodiment is an inflation molding device. Before specifically describing the present embodiment, problems to be solved by the present embodiment will be described.

In a case where molding conditions are changed for some reason in the inflation molding device, for example, a film breaks in some cases by changing the molding conditions. In a case where the film breaks, the inflation molding device should be started up again, and thus work efficiency decreases. In addition, a molding material is also wasted. Therefore, simulation of a case where the molding conditions are changed is desired.

In addition, the inflation molding device of the related art can estimate only average stress generated at bubbles. Even when the average stress generated at the bubbles is equal to or lower than a breakage threshold, the bubbles naturally break, for example, in a case where the highest stress generated at the bubbles (hereinafter, also referred to as maximum stress) exceeds the breakage threshold. That is, in a case where only the average stress can be estimated, highly accurate break prediction cannot be made. Therefore, estimation of a distribution of stress generated at bubbles is desired.

Hereinafter, an inflation molding device according to the present embodiment for solving the problems will be described.

<FIG> is a view showing a schematic configuration of an inflation molding device <NUM> according to the embodiment. The inflation molding device <NUM> includes a die <NUM>, a cooling unit <NUM>, a pair of guide units <NUM>, a pick-up machine <NUM>, a winding machine <NUM>, a pressure detector <NUM>, a temperature detection unit <NUM>, air supply means <NUM>, and a control device <NUM>.

Hereinafter, on a plane perpendicular to a center axis C, a direction along the circumference of a circle about the center axis C will be described as a circumferential direction.

A melted molding material is discharged in a cylindrical shape from a ring-shaped discharge port 102a formed in the die <NUM>. Inside the discharged molding material having the cylindrical shape, air is ejected at an appropriate timing from an air outlet 102b formed in a center portion of the die <NUM>, and a thin film (hereinafter, also called as a "bubble") that has been swollen into a cylindrical shape is molded.

The cooling unit <NUM> is disposed above the die <NUM>. The cooling unit <NUM> blows cooling air to a bubble and cools the bubble.

The pair of guide units <NUM> are disposed above the cooling unit <NUM>. The pair of guide units <NUM> guide the bubble to the pick-up machine <NUM>. The pick-up machine <NUM> is disposed above the guide unit <NUM>. The pick-up machine <NUM> includes a pair of pinch rolls <NUM>. The pair of pinch rolls <NUM> are driven and rotated by a motor (not shown) and fold the guided bubble flat while pulling up the guided bubble. The winding machine <NUM> winds the folded film and forms a film roll body <NUM>.

The temperature detection unit <NUM> detects a temperature distribution of a bubble surface. The temperature detection unit <NUM> is an infrared camera that detects the temperature distribution, such as a thermography. The temperature detection unit <NUM> is not limited to the infrared camera and may be, for example, a non-contact temperature sensor that detects the temperature of a spot (dot). In this case, by mounting the temperature detection unit <NUM> on, for example, a robot arm and detecting the temperature of the bubble surface while being moved in the surroundings of the bubble, the temperature distribution of the bubble surface may be detected. The temperature detection unit <NUM> transmits the detection result to the control device <NUM>.

The air supply means <NUM> sends surrounding air to an air supply path 102c, and the air blows from the air outlet 102b. That is, the air supply means <NUM> supplies air into the bubble.

The pressure detector <NUM> detects a pressure in the air supply path 102c. The pressure detector <NUM> may be provided in the bubble. The pressure detector <NUM> transmits the detection result to the control device <NUM>.

The control device <NUM> is a device that comprehensively controls the inflation molding device <NUM>. For example, based on data acquired during molding of a film, the control device <NUM> estimates a viscosity distribution of a molding material or estimates a viscosity parameter in a viscosity model formula of the molding material.

<FIG> is a block diagram schematically showing a function and a configuration of the control device <NUM>. Each block shown herein can be realized by an element or a mechanical device including a CPU of a computer as hardware and is realized by a computer program or the like as software, but is shown as a functional block realized in cooperation therewith herein. Therefore, it is clear for those skilled in the art that the functional blocks can be realized in various manners in combination with hardware and software.

<FIG> is a view for describing various types of variables related to a bubble. A lower view in <FIG> is a sectional view of the bubble cut by a plane including the center axis C, and an upper view is a sectional view of the bubble cut by a horizontal plane. In <FIG>, x is a bubble height. The bubble height is a height with an upper surface of the die <NUM> as a reference surface and can also be called a distance from the upper surface of the die <NUM> in a vertical direction. In addition to <FIG>, <FIG> will be referred to.

The control device <NUM> includes a communication unit <NUM> that executes communication processing with the temperature detection unit <NUM> or the pressure detector <NUM> in accordance with various communication protocols, a U/I unit <NUM> that receives an operation input by a user and that causes a display unit to display various types of screens, a data processing unit <NUM> that executes various types of data processing based on data acquired from the communication unit <NUM> and the U/I unit <NUM>, and a storage unit <NUM> that stores data referenced and updated by the data processing unit <NUM>.

The data processing unit <NUM> includes a receiving unit <NUM>, a strain speed calculation unit <NUM>, a bubble shape acquisition unit <NUM>, an internal and external pressure difference identification unit <NUM>, a viscosity estimation unit <NUM>, a temperature identification unit <NUM>, a parameter estimation unit <NUM>, a simulation unit <NUM>, an output processing unit <NUM>, and a stress estimation unit <NUM>.

The receiving unit <NUM> receives bubble surface temperature data from the temperature detection unit <NUM>. In addition, the receiving unit <NUM> receives in-bubble pressure data from the pressure detector <NUM>.

The bubble shape acquisition unit <NUM> acquires bubble shape data. The bubble shape acquisition unit <NUM> acquires the bubble shape data by analyzing an image of the temperature distribution of the bubble surface detected by the temperature detection unit <NUM>. As a modification example, the bubble shape acquisition unit <NUM> may acquire the bubble shape data by analyzing a bubble visible light image captured by a visible light camera.

The bubble shape data acquired by the bubble shape acquisition unit <NUM> includes a radius R of a bubble at each bubble height x, a curvature radius r<NUM> in a height direction of a bubble surface, and a curvature radius r<NUM> perpendicular to the curvature radius r<NUM>. The curvature radii r<NUM> and r<NUM> correspond to curvature radii represented by the following equations (<NUM>) and (<NUM>), respectively. <MAT> <MAT>.

The strain speed calculation unit <NUM> calculates a strain speed of a bubble at each bubble height x. Specifically, the strain speed calculation unit <NUM> calculates a flowing direction strain speed (ε<NUM> dot), a radial direction strain speed (ε<NUM> dot), and a film thickness direction strain speed (ε<NUM> dot) at each bubble height x. The strain speeds ε<NUM> dot, ε<NUM> dot, and ε<NUM> dot are calculated through the following equations (<NUM>) to (<NUM>), respectively. <MAT> <MAT> <MAT>.

It is known that a film movement speed v is represented by a triangular function having a bubble height as the horizontal axis, takes a lowest value immediately after exiting the discharge port 102a, and takes a highest value when reaching the pick-up machine <NUM>. Therefore, when a film movement speed at each of the discharge port 102a and the pick-up machine <NUM> is known, the film movement speed v at each bubble height x can be estimated. A film movement speed at the discharge port 102a can be calculated based on a molding material extrusion amount (mass flow rate), a molding material melt density, a radius R<NUM> of the discharge port 102a, and a lip width (the width of the discharge port 102a) H<NUM>. A film movement speed at the pick-up machine <NUM> is equal to a pick-up speed that is a speed at which the pick-up machine <NUM> picks up (pulls) a film and can be identified by detecting the number of rotations of the motor driving the pair of pinch rolls <NUM>.

A method of estimating (identifying) the film movement speed v at each bubble height x is not limited thereto, and the film movement speed may be estimated (identified) through other known methods.

The internal and external pressure difference identification unit <NUM> identifies an internal and external pressure difference ΔP(x) at each bubble height x, that is, a distribution of the internal and external pressure difference, which is represented by the following equation (<NUM>).

Since air has a weight, the density of the air changes depending on a height, and thereby a pressure changes depending on the height. In general, when the height is increased by <NUM>, the pressure decreases by <NUM> Pa. Therefore, the internal and external pressure difference identification unit <NUM> identifies an internal pressure Pin(x) at the bubble height x in consideration of a height difference between a detection position of the pressure detector <NUM> and the bubble height x at a pressure detected by the pressure detector <NUM>.

A cooling air pressure Pout(x) may be identified based on simulation of cooling air or may be detected using a pressure gauge.

The internal pressure Pin(x) and the cooling air pressure Pout(x) essentially depend on the bubble height x, but may be constant regardless of the bubble height x. For example, the internal pressure Pin may be a pressure detected by the pressure detector <NUM> or a pressure based thereon.

In addition, the cooling air pressure Pout(x) may be ignored, that is, the cooling air pressure Pout(x) = <NUM> may be satisfied.

The stress estimation unit <NUM> estimates stress, that is, a stress distribution at each bubble height based on a known relational equation related to stress generated at a bubble and a bubble internal and external pressure difference ΔP. The stress is uniform in the circumferential direction.

The viscosity estimation unit <NUM> estimates a viscosity η(x) at each bubble height x, that is, a viscosity distribution in the height direction. The viscosity estimation unit <NUM> makes estimation based on various types of known relational equations, the curvature radius r<NUM> and the curvature radius r<NUM> at each bubble height x acquired by the bubble shape acquisition unit <NUM>, and stress estimated by the stress estimation unit <NUM>. The viscosity of a bubble is uniform in the circumferential direction.

The temperature identification unit <NUM> identifies the temperature of a bubble at each bubble height x. For example, the temperature identification unit <NUM> may identify the temperature of the bubble at each bubble height x from a temperature distribution detected by the temperature detection unit. For example, the temperature of the bubble may be uniform in the circumferential direction, and a temperature at each bubble height x at a certain circumferential position may be a temperature at each bubble height.

In addition, for example, the temperature identification unit <NUM> may identify the temperature of the bubble at each bubble height x from the temperature of the die <NUM>. The more time has passed since the discharge of a molding material, that is, a bubble at a higher position is cooled. In consideration of this, the temperature identification unit <NUM> may identify the temperature of the bubble at each bubble height x from the temperature of the die <NUM>.

The parameter estimation unit <NUM> estimates viscosity parameters of a molding material. The viscosity parameters are parameters k<NUM>, A, B, C, m (mass flow rate), C1, C2, and Tref (reference temperature) in a viscosity model equation represented by the following equation (<NUM>).

In addition, a strain speed ε dot and strain ε are calculated through the following equations (<NUM>) and (<NUM>). <MAT> <MAT>.

The parameter estimation unit <NUM> estimates a viscosity parameter by fitting the viscosity model equation represented by the equation (<NUM>) to the viscosity distribution estimated by the viscosity estimation unit <NUM>.

The simulation unit <NUM> executes simulation using the estimated viscosity parameter. The simulation unit <NUM> calculates the shape and stress of a bubble by inputting molding conditions. The molding conditions include, for example, a molding material extrusion amount, a pick-up speed, a blow ratio, a die temperature, and a cooling air amount.

For example, the simulation unit <NUM> may execute simulation by inputting the current molding conditions during molding. When the current molding conditions during molding are input, it is possible to know whether or not there is a possibility in which a bubble during molding breaks. In a case where there is a possibility in which the bubble breaks, the user may be notified of the fact through screen display, voice, or other methods. In this case, the simulation unit <NUM> may calculate and present molding conditions under which a film that has no possibility of breakage and that has a high quality can be molded. In addition, the molding conditions may be automatically changed.

In addition, for example, the simulation unit <NUM> may calculate the shape and stress of the bubble in a case where molding conditions have changed, by inputting molding conditions planned to be changed. In this case, for example, it is possible to know whether or not there is a possibility of breakage by changing the molding conditions.

The output processing unit <NUM> displays various types of screens on a predetermined display. The various types of screens may be, for example, a screen showing a stress distribution of a bubble during molding, which is estimated by the stress estimation unit <NUM>, may be, for example, a screen showing a viscosity parameter of a bubble during molding, which is estimated by the parameter estimation unit <NUM>, or may be, for example, a diagram showing a screen related to simulation. As a modification example, the output processing unit <NUM> may perform printing using a predetermined printer or may transmit an e-mail to a predetermined e-mail address as output processing, instead of displaying on the display.

<FIG> is a diagram showing a simulation screen. The simulation screen includes a molding conditions field <NUM>, a calculation result field <NUM>, and a viscosity parameter field <NUM>.

The molding conditions field <NUM> includes an extrusion amount field <NUM>, a pick-up speed field <NUM>, a blow ratio field <NUM>, a die temperature field <NUM>, and a cooling air amount field <NUM>. A molding material extrusion amount (Kg/h) is input to the extrusion amount field <NUM>. The pick-up speed (m/min) of the pick-up machine <NUM> is input to the pick-up speed field <NUM>. A blow ratio is input to the blow ratio field <NUM>. A die setting temperature is input to the die temperature field <NUM>. The cooling air amount (m<NUM>/min) of the cooling unit <NUM> is input to the cooling air amount field <NUM>.

The viscosity parameters k<NUM>, A, B, C, m, C1, C2, and Tref estimated by the parameter estimation unit <NUM> are displayed in the viscosity parameter field <NUM>. The simulation unit <NUM> of the control device <NUM> calculates the shape and stress of a bubble using the viscosity parameters displayed in the viscosity parameter field <NUM> by inputting the molding conditions input to the molding conditions field <NUM>.

The calculation result field <NUM> includes a maximum stress field <NUM>, a melt tension field <NUM>, a moldability field <NUM>, and a shape display field <NUM>. The calculated maximum stress is displayed in the maximum stress field <NUM>. The calculated melt tension is displayed in the melt tension field <NUM>. The melt tension field <NUM> shows a force acting on a melted molding material in a film moving direction. Moldability is displayed in the moldability field <NUM>. A bubble shape is shown in the shape display field <NUM>. The color of a bubble to be displayed in the shape display field <NUM> may be changed according to information related to the bubble such as the radius of the bubble and stress generated at the bubble. For example, as in the shown example, the bubble may be displayed in a light color where the radius is small and in a dark color where the radius of the bubble is large. In addition, for example, the bubble may be displayed in a light color where generated stress is low and in a dark color where the generated stress is high.

When maximum stress becomes equal to or higher than a predetermined threshold, the bubble breaks. Therefore, by referring to the maximum stress field <NUM>, it is possible to check whether or not the bubble breaks and in a case where the bubble is estimated to break, to what extent the bubble exceeds the threshold.

When melt tension is not equal to or higher than a predetermined threshold, the bubble is not stretched taut, and thereby molding is impossible. Therefore, by referring to the melt tension field <NUM>, it is possible to check whether or not the bubble is stretched taut, that is, whether the bubble can be molded, and in a case where it is estimated that the bubble cannot be molded, to what extent the bubble falls below the threshold.

Next, an operation of the inflation molding device <NUM> configured as described above will be described.

The processing order is merely an example, and processing order may be changed, or some processing may be executed in parallel with other processing insofar as there is no inconsistency.

Next, effects of the present embodiment will be described. In the present embodiment, stress generated at a bubble is estimated based on a bubble internal and external pressure difference ΔP. In this case, an estimation error becomes smaller compared to a case where stress is estimated based on torque of the motor driving the pinch roll <NUM>. That is, a more accurate stress distribution is estimated. Herein, even when average stress generated at the bubble is equal to or lower than the breakage threshold, the bubble naturally breaks when maximum stress exceeds the breakage threshold. That is, as the maximum stress can be more accurately estimated, more accurate break prediction becomes possible.

In addition, in the present embodiment, a stress distribution of a bubble is estimated, and a viscosity distribution of the bubble is estimated based thereon. The estimated viscosity distribution can be useful for adjusting molding conditions. For example, in a case where the quality of a molded film is poor, when the current viscosity distribution and a viscosity distribution when the quality of the film is good are compared to each other and it is known that both are different from each other, for example, it is possible to know that adjustment such as raising and lowering the temperature of a resin is preferable.

In addition, in the present embodiment, a viscosity parameter of a molding material can be estimated, and the shape and stress of a bubble can be calculated by inputting molding conditions. Accordingly, for example, in a case where molding conditions are appropriately set and molding is started in a situation where appropriate molding conditions are not known, whether the molding conditions are to be kept as it is or whether the molding conditions are to be changed since there is a possibility of breakage or the like can be determined. In addition, the molding conditions under which a film that has no possibility of breakage and that has a high quality can be molded can be presented. It is also possible to automatically change the molding conditions.

In addition, for example, in a case where molding conditions are changed for some reason, whether there is no problem with molding conditions planned to be changed or whether a change into the molding conditions planned to be changed is not appropriate since there is a possibility of breakage or the like can be determined.

In addition, in the present embodiment, stress generated at a bubble is estimated based on a bubble internal and external pressure difference ΔP. In this case, an estimation error becomes smaller compared to a case where stress is estimated based on torque of the motor driving the pinch roll <NUM>.

The present invention has been described hereinbefore based on the embodiment. The embodiment is an example. It is clear for those skilled in the art that various modification examples are possible for a combination of each component and each processing process, and such modification examples are also within the scope of the present invention. Hereinafter, such modification examples will be described.

Although stress generated at a bubble, a viscosity of the bubble, a bubble temperature, and the like are uniform in the circumferential direction in the embodiment, each of the values at positions in the circumferential direction may be estimated assuming that these may not be uniform in the circumferential direction.

Unlike the embodiment, the stress estimation unit <NUM> may estimate stress based on torque of the motor driving the pinch roll <NUM>, instead of an internal and external pressure difference ΔP. Then, the viscosity estimation unit <NUM> may estimate a viscosity, and the parameter estimation unit <NUM> may estimate a viscosity parameter, assuming that the stress has been uniformly generated at a valve in the height direction. In this case, a viscosity distribution of a bubble cannot be estimated, but the viscosity parameter of the bubble can be estimated although the viscosity parameter is a value in a case where stress estimated based on a pick-up speed has been uniformly generated at the bubble in the height direction.

Unlike the embodiment, the parameter estimation unit <NUM> may estimate a viscosity parameter assuming that the temperature of a bubble is uniform in the height direction. In this case, it is sufficient that the temperature detection unit <NUM> is a non-contact temperature sensor that detects the temperature of a spot (dot). Alternatively, a uniform bubble temperature may be estimated based on the temperature of the die <NUM>. In this case, the temperature detection unit <NUM> is unnecessary. The bubble shape acquisition unit <NUM> may acquire bubble shape data by analyzing a bubble visible light image captured, for example, by a visible light camera. In addition, in a case where the shape of the bubble is acquired through a method not using an image of a temperature distribution of a bubble surface, for example, the bubble shape acquisition unit <NUM> acquires bubble shape data from a visible light image, the temperature of the bubble is unnecessary in estimating the viscosity distribution of the valve. Thus, the temperature detection unit <NUM> is unnecessary in estimating the viscosity distribution of the bubble.

Claim 1:
An inflation molding device comprising:
a viscosity estimation unit that estimates a viscosity of a bubble discharged in a substantially cylindrical shape from a die;
a temperature identification unit that identifies a temperature of the bubble; and
a parameter estimation unit that estimates a viscosity parameter of the bubble based on the viscosity of the bubble estimated by the viscosity estimation unit and the temperature of the bubble detected by the temperature identification unit.