Temperature measuring device, inflation molding machine, and temperature measuring method

Abstract

The present invention provides a temperature measuring device, an inflation molding machine, and a temperature measuring method that can effectively measure the temperature of bubbles during inflation molding. [Solution] The temperature measuring device 31 of this invention measures the temperature of a bubble 51 in a non-contact manner during inflation molding, in which a molding material is extruded and expanded by supplying fluid to the inside of the molding material to form a bubble 51. The device has an infrared image sensor that images infrared rays in a temperature detection range 41 that includes the bubble 51, and when imaging the infrared rays, it focuses on a target area of ​​a part of the temperature detection range 41 and shifts the focus for at least a part of the remaining non-target area.

Description

Technical Field

[0001] This invention relates to a temperature measuring device, an inflation molding machine, and a temperature measuring method.

Background Art

[0002] Conventionally, as technologies related to inflation molding, there are, for example, those described in Patent Documents 1 to 4.

[0003] In Patent Document 1, it is stated that "a technique capable of detecting whether a tubular resin is in a stable state" is provided, and "a die that extrudes resin in a tubular shape from an annular discharge port, an acquisition unit that acquires data related to the extruded tubular resin, and a determination unit that determines whether the central position of the tubular resin at at least one height position is on the reference axis of the die are provided", and an inflation molding apparatus is proposed.

[0004] Patent Document 2 aims to "provide a frost line control device that accurately detects the frost line position of a cylindrical thin film resin using fuzzy inference based on the change in the resin surface temperature in the flow direction of the extruded cylindrical thin film resin, and controls the cooling air volume of the cooling device so that there is no change in the resin surface temperature at the accurately detected frost line position". In an inflation molding line where a continuous cylindrical thin film resin is extruded upward from a mold attached in front of the extrusion direction of an extrusion molding machine, and a cooling device for cooling the extruded cylindrical thin film resin from the outside is provided near the mold, it includes "temperature measuring means for measuring the change in the resin surface temperature in the flow direction of the cylindrical thin film resin extruded from the mold, position detecting means for detecting the frost line position of the cylindrical thin film resin based on the change in the resin surface temperature measured by this temperature measuring means, and control means for controlling the cooling air volume of the cooling device so as to keep the frost line position detected by this position detecting means constant", and a frost line control device in an inflation molding line is described.

[0005] Patent Document 3 describes a "plastic molding apparatus comprising an extruder that melts a resin material and extrudes the molten resin from an extrusion die, and a plastic molding apparatus that molds the molten resin extruded from the extrusion die, comprising a spectrophotometer that measures the absorbance of infrared light at each wavelength as it passes through the surrounding atmosphere of the molten resin extruded from the extrusion die, a measurement wavelength determination means that receives absorbance data for each wavelength from the spectrophotometer and determines the measurement wavelength of infrared light with low absorbance, an infrared radiation thermometer that measures the radiation temperature at the measurement wavelength determined by the measurement wavelength determination means, and a plastic molding apparatus characterized by measuring the surface temperature of the molten resin extruded from the extrusion die using the infrared radiation thermometer." According to this "plastic molding apparatus," "the effect is that by measuring the absorbance of infrared light using a spectrophotometer, the measurement wavelength determination means determines the measurement wavelength of infrared light with the optimal wavelength of low absorption, enabling the infrared radiation thermometer to perform accurate temperature measurements, and a practical infrared radiation thermometer can be used to construct a plastic molding apparatus."

[0006] Patent Document 4 states that it "provides an extrusion T-die apparatus that enables control of neck-in," and discloses "an extrusion T-die apparatus that extrudes molten resin into a film, characterized in that it is equipped with at least an infrared radiation sensor that simultaneously measures the width of the molten resin film in the die width direction after T-die discharge and the temperature distribution of the molten resin film, and a control device that controls the temperature inside the T-die by referring to the measured value of the molten resin film width and the measured value of the molten resin film temperature distribution obtained by the infrared radiation sensor." [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-163623 [Patent Document 2] Japanese Patent Application Publication No. 5-138733 [Patent Document 3] Japanese Patent Publication No. 2015-116687 [Patent Document 4] Japanese Patent Publication No. 2015-189113 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In inflation molding, from a quality control perspective, it is necessary to accurately measure the temperature over a relatively wide range in the bubbles formed by the extrusion and expansion of the molding material. In this respect, the technologies described in Patent Documents 1 to 4 all have room for further improvement.

[0009] This invention was devised to address these issues, and its purpose is to provide a temperature measuring device, an inflation molding machine, and a temperature measuring method that can effectively measure the temperature of bubbles during inflation molding. [Means for solving the problem]

[0010] One temperature measuring device that can achieve the above-mentioned objective is a temperature measuring device that measures the temperature of a bubble in a non-contact manner in inflation molding, in which a molding material is extruded and expanded by supplying fluid to the inside of the molding material to form a bubble, and has an infrared image sensor that images infrared rays within a temperature detection range including the bubble, and when imaging the infrared rays, focuses on a target area of ​​a part of the temperature detection range and shifts the focus for at least a part of the remaining non-target area.

[0011] The inflation molding machine is equipped with the temperature measuring device described above.

[0012] One temperature measurement method that can achieve the above-mentioned objective is a method for non-contactly measuring the temperature of a bubble in inflation molding, in which a molding material is extruded and expanded by supplying fluid to the inside of the molding material to form a bubble, and includes imaging infrared rays within a temperature detection range including the bubble with an infrared image sensor, wherein in imaging the infrared rays, the focus is set on a target area of ​​a part of the temperature detection range, and the focus is shifted for at least a part of the remaining non-target area. [Effects of the Invention]

[0013] According to the above-described temperature measuring device and temperature measuring method, the temperature of the bubbles during inflation molding can be effectively measured. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing an example of an inflation molding machine equipped with a temperature measuring device according to one embodiment of this invention. [Figure 2] This is a cross-sectional view along the line II-II in Figure 1. [Figure 3] Figure 1 is a perspective view showing the temperature detection range, including bubbles, from the viewpoint of the temperature measuring device. [Figure 4] This is a cross-sectional view similar to Figure 2, showing an inflation molding machine equipped with multiple temperature measuring devices according to one embodiment of this invention. [Figure 5] This is a block diagram showing control devices and other components that can be installed in an inflation molding machine. [Modes for carrying out the invention]

[0015] Embodiments of this invention will be described in detail below with reference to the drawings. The inflation molding machine 1 illustrated in FIG. 1 generally includes an extrusion device 11 that extrudes while melting a resin material or other molding materials, a recovery device 21 that recovers the bubble 51 formed of the molding material extruded from the extrusion device 11 as a film 54, and a temperature measurement device 31 that measures the temperature of the bubble 51.

[0016] The molding material is extruded from a die 12 as a nozzle or the like provided on the tip side of the extrusion device 11 into a cylindrical shape such as a thin film cylinder, and expands by supplying a fluid such as a gas inside thereof to become a bubble 51. The molten molding material extruded from the extrusion device 11 is cooled and solidified by a cooling device (not shown) when it becomes the bubble 51. The bubble 51 generally has a shape such as a cylinder with a diameter-expanded central region compared to the end regions in the extrusion direction (the vertical direction in FIG. 1), but is guided between the pinch rolls 23 by the guide portion 22 of the recovery device 21 and is overlapped in a sheet shape there to become the film 54. The film 54 is recovered in a roll form by being wound around a winder (not shown). According to the inflation molding machine 1, the film 54 can be continuously manufactured in this way.

[0017] To control the quality of the film 54 manufactured by the inflation molding machine 1, it is essential to grasp the stability of the bubble 51. For that purpose, it is desirable to appropriately measure and monitor the temperature in a relatively wide range of the bubble 51 formed of the molding material extruded from the extrusion device 11.

[0018] Generally, to measure the temperature of a moving object such as the bubble 51 non-contact, an infrared thermometer that uses infrared rays radiated from the moving object, such as thermography having an infrared imaging device or a radiation thermometer having a thermopile, is used.

[0019] Among these, thermography captures temperature information within the temperature detection range as an image and can measure the temperature of a wide range of the bubble 51. However, in simple thermography, when attempting to measure the temperature of the bubble 51 made of polyethylene or other polyolefins with a thin thickness and high infrared transmittance, not only the temperature of the portion that is originally intended to be detected but also the temperature of the object behind it is detected, making it difficult to accurately measure the temperature of the bubble 51. More specifically, as shown in FIGS. 1 and 2, when the bubble 51 is virtually divided into a front-side bubble portion 52, which is the half located closer to the infrared imaging element of the thermography along the center line CL (shown as a dashed line in FIGS. 1 and 2) in the shooting direction (the left-right direction in FIGS. 1 and 2), and a rear-side bubble portion 53, which is the half located farther from the front-side bubble portion 52 and separated from it by the infrared imaging element of the thermography, even if the portion where the temperature is to be measured by the thermography is the front-side bubble portion 52, the infrared information actually detected by the thermography may include not only the infrared information of the front-side bubble portion 52 but also the infrared information of the rear-side bubble portion 53 that passes through the front-side bubble portion 52. Therefore, with simple thermography, the temperature of the bubble 51 cannot be properly measured.

[0020] On the other hand, in a radiation thermometer, for example, since it detects the infrared absorption peak obtained from the infrared radiation characteristics of the front-side bubble portion 52 of the measurement target, it can shut out the infrared information from the rear-side bubble portion 53. However, because the radiation thermometer is a so-called point measurement, it cannot measure the temperature of a wide range of the bubble 51 at once.

[0021] In contrast, in this embodiment, the temperature of the bubble 51 is measured non-contact using a predetermined temperature measuring device 31. This temperature measuring device 31 has an infrared image sensor, similar to a thermograph, but when imaging the infrared radiation emitted from the bubble 51 within the temperature detection range 41 (see Figure 3) of the temperature measuring device 31 onto the imaging surface of the infrared image sensor, it is possible to focus on a part of the target area of ​​the temperature detection range 41 (for example, the front bubble portion 52) and defocus on at least a part of the remaining non-target area (for example, the back bubble portion 53). In other words, the temperature measuring device 31 can set the target area to a focused state and the non-target area to a defocused state. Here, it is sufficient that the imaging position of the infrared radiation from the non-target area is offset from the imaging surface of the infrared image sensor more than the imaging position of the infrared radiation from the target area.

[0022] As a result, even if the bubble 51 is made of a material with high infrared transmittance, when detecting the temperature of the bubble 51 within the temperature detection range 41, the inclusion of temperature information from non-target areas as noise is suppressed, allowing for accurate measurement of the temperature of the target area.

[0023] Furthermore, unlike the radiation thermometer described above, the temperature measuring device 31 measures temperature using an infrared image sensor, making it possible to acquire information on the heat distribution of a relatively wide area of ​​the bubble 51.

[0024] The target area focused by the temperature measuring device 31 can be a part of the temperature detection range 41 as shown in Figure 3, for example, at least a part of either the front bubble portion 52 or the rear bubble portion 53. In contrast, the non-target area for which the focus is shifted can be at least a part of the remaining portion of the temperature detection range 41 other than the target area, for example, at least a part of the other of the front bubble portion 52 or the rear bubble portion 53. After measuring the temperature with either the front bubble portion 52 or the rear bubble portion 53 as the target area and the other as the non-target area, it is also possible to measure the temperature with the other as the target area and the other as the non-target area. In this case, temperature information from at least a part of the front bubble portion 52 and at least a part of the rear bubble portion 53 can be obtained.

[0025] As an example, a temperature measuring device 31 may be constructed by attaching an optical element with a changeable focal length, such as a zoom lens made up of one or more convex and concave lenses, to a thermograph. By changing the focal length with such an optical element with a zoom function, for example, by swapping the front bubble portion 52 and the back bubble portion 53 for the target area and the non-target area, and measuring the temperature of each, it is possible to obtain temperature information for the front bubble portion 52 and the back bubble portion 53.

[0026] Furthermore, in the case of the temperature measuring device 31 having the optical element described above, the diameter of the bubble 51 can also be measured by focusing on the front bubble portion 52 and the back bubble portion 53 of the bubble 51, respectively. Therefore, by using such a temperature measuring device 31, not only the temperature but also the diameter of the bubble 51 can be determined, allowing for a more detailed evaluation of the stability of the bubble 51.

[0027] The temperature measuring device 31 can be positioned outside the bubble 51 in the radial direction (left-right direction in Figure 1), at a distance from the bubble 51, as shown in Figures 1 and 2, in order to measure the temperature of the bubble 51 without contact. In this case, of the bubble 51 having a front bubble portion 52 and a rear bubble portion 53 that are virtually separated as described above, at least a part of the front bubble portion 52 may be designated as the area to be measured for temperature, and at least a part of the rear bubble portion 53 may be designated as the area not to be measured. In this way, temperature information of the front bubble portion 52 can be effectively acquired while suppressing the inclusion of noise-inducing temperature information from the rear bubble portion 53 behind the front bubble portion 52.

[0028] Furthermore, in order to more effectively focus on the target area and defocus on the non-target area, it may be desirable to position the temperature measuring device 31 around the bubble 51 and bring it relatively close to the bubble 51, to reduce the aperture size to make the depth of field shallower if the optical element has a changeable focal length, and to use an optical element with an infrared light focal length of about 80mm to 1000mm (so-called medium telephoto lens, telephoto lens, etc.).

[0029] As described above, the temperature measuring device 31 can accurately measure the temperature, particularly in the central radial portion, of both the front bubble portion 52 and the rear bubble portion 53 as viewed from the temperature measuring device 31, by focusing or shifting its focus. On the other hand, there are cases where it is necessary to accurately measure the temperature around the entire circumference of the bubble 51, including the lateral portions located radially outside the front bubble portion 52 and the rear bubble portion 53 as viewed from the temperature measuring device 31.

[0030] In such cases, as shown in Figure 4, multiple temperature measuring devices, for example, two temperature measuring devices 31 and 32, may be arranged radially outside the bubble 51 and spaced apart from each other in the circumferential direction of the bubble 51.

[0031] In the example shown in Figure 4, two temperature measuring devices 31 are arranged around the bubble 51 such that, in a cross-sectional view perpendicular to the extrusion direction, the shooting direction of one temperature measuring device 31 (left-right direction in Figure 4) and the shooting direction of the other temperature measuring device 31 (up-down direction in Figure 4) form an angle of approximately 90°.

[0032] By arranging the two temperature measuring devices 31 and 32 in this manner, infrared information of the front bubble portion 52 and the back bubble portion 53 as viewed from each temperature measuring device 31 and 32 can be acquired, allowing for accurate measurement of the temperature around the entire circumference of the bubble 51. Note that measuring the temperature around the entire circumference of the bubble 51 using a simple thermograph would require three or more devices. However, although not shown in the illustration, in this embodiment of the invention, it is also possible to arrange three or more temperature measuring devices around the bubble 51, in which case these devices may be positioned at equal intervals in the circumferential direction of the bubble 51.

[0033] Incidentally, the extrusion device 11 shown in the illustration of the inflation molding machine 1 comprises a housing 13, a hopper 14 used to supply molding material into the housing 13, and a die 12 provided on the leading end side of the housing 13 in the extrusion direction. Although not shown here, the die 12 has a discharge port for discharging the molding material. Furthermore, the extrusion device 11 generally also includes a screw (not shown) provided inside the housing 13, a motor or other drive source for rotating the screw, and a heater for heating the molding material supplied into the housing 13. The molding material supplied into the housing 13 is melted by heating by the heater and rotation of the screw, and then extruded from the die 12.

[0034] In this example, the discharge port of die 12 is formed on the upper side in the vertical direction, and the molten molding material is discharged from this port in an upward direction in the vertical direction. However, the discharge port is not limited to this location; for example, it may be formed on the lower side in the vertical direction and discharge the molding material downward.

[0035] On the radially inner side of the discharge port of die 12, although not shown, there is an outlet for a gas such as air or other fluid to expand the molten molding material. A cooling device, also not shown, can be provided around die 12. The molten molding material discharged from die 12 expands into a cylindrical shape due to the fluid ejection from the outlet and solidifies as it is cooled by a gas such as air blown from the cooling device, forming a bubble 51.

[0036] The temperature of the bubbles 51 formed on the die 12 is measured using the aforementioned temperature measuring device 31.

[0037] The bubble 51 is then recovered as a film 54 by the recovery device 21. The illustrated recovery device 21 has two guide parts 22, such as plates, which are positioned on either side of the upper vertical end of the bubble 51 and are inclined to move toward each other upward, and a pinch roll 23 positioned above the guide parts 22. The bubble 51 is guided between the pair of pinch rolls 23 by being sandwiched from both sides by the guide parts 22 at its upper vertical end, where the front bubble portion 52 and the back bubble portion 53 overlap to form a sheet-like film 54.

[0038] The recovery device 21 is further equipped with a winding machine, although it is not shown in the diagram. The film 54 obtained between the pinch rolls 23 is wound up by the winding machine and recovered in a roll.

[0039] The inflation molding machine 1 described above may include a control device connected to various devices, as illustrated in Figure 5. The control device may consist of a processor, RAM (Random Access Memory), ROM (Read Only Memory), etc.

[0040] The control device may be connected to an input device used by the user of the inflation molding machine 1 to input information, a display device used to transmit information to the user, a storage device for storing information or data, various drive sources, various sensors, etc., and may be configured to enable the transmission and reception of data or signals between them via a bus. At least a part of the input device and the display device may be a touch panel. The storage device may include an HDD (Hard Disk Drive) or flash memory, etc.

[0041] The control device can perform the control described later by executing the control program recorded in the ROM or storage device mentioned above using the processor mentioned above.

[0042] The aforementioned temperature measuring devices 31 and 32 can be connected to a control device. In this case, the control device can use the temperature of the bubbles 51 in the target area measured by the temperature measuring devices 31 and 32, as well as the heat distribution including that temperature, as input information for various control purposes.

[0043] As an example, the control device can calculate the frost line height of the bubble 51 based on the temperature of the bubble 51, which is input information received from the temperature measuring devices 31 and 32. The frost line is the boundary line around the entire circumference of the bubble 51 between the region where the crystallization temperature of the molding material has not been reached and the region where the crystallization temperature has been reached, and it can sometimes be visually identified by the abrupt change in transparency that occurs when the molding material solidifies from a molten state. Depending on the heat distribution of the bubble 51, the frost line may have a shape that is not linear around the entire circumference but has irregularities in the height direction, and it can be used as an indicator to evaluate the stability of the bubble 51 or the molding process. The frost line height can be determined by extracting the measurement points of the crystallization temperature from the heat distribution related to the temperature of the bubble 51 measured by the temperature measuring devices 31 and 32.

[0044] Another example is that, if the control device detects from the temperature of the bubble 51, which is input information from the temperature measuring devices 31 and 32, that the heat distribution in the target area is non-uniform, it can control the operation of the inflation molding machine 1 to correct the non-uniformity of the heat distribution. Examples of this operation control include changing the rotation speed of the screw of the extruder 11, changing the heating temperature of the heater, changing the opening width of the die 12, changing the flow rate or temperature of the fluid for expansion or cooling of the molding material, changing the rotation speed of the pinch roll 23, and changing the winding speed of the winding machine. Whether the non-uniformity of the heat distribution has been corrected by such control can be determined, for example, by whether the temperature variation in the heat distribution has been reduced before and after the control. [Explanation of Symbols]

[0045] 1. Inflation molding machine 11 Extruder 12 dives 13 cabinets 14 Hopper 21 Recovery device 22 Guide section 23 Pinch Roll 31, 32 Temperature measuring device 41 Temperature detection range 51 Bubble 52 Front bubble section 53 Rear bubble section 54 film CL center line

Claims

1. In inflation molding, in which a molding material is extruded and expanded by supplying fluid to the inside of the molding material to form bubbles, a temperature measuring device for non-contactly measuring the temperature of the bubbles, It has an infrared imaging sensor that forms an image of infrared rays within a temperature detection range including the aforementioned bubble, A temperature measuring device that, when forming an image of infrared light, focuses on a portion of the target area within the temperature detection range and shifts the focus to at least a portion of the remaining non-target area.

2. The temperature measuring device according to claim 1, which is positioned and used on the radially outer side of the bubble.

3. The bubble has a front bubble portion located closer to the infrared image sensor and a back bubble portion located further away from the temperature measuring device, separated by the front bubble portion. The temperature measuring device according to claim 1, wherein at least a portion of either the front bubble portion or the rear bubble portion is the target area, and at least a portion of the other front bubble portion or the rear bubble portion is the non-target area.

4. The temperature measuring device according to claim 1, having an optical element with a changeable focal length.

5. The temperature measuring device according to claim 4, wherein the optical element is used to measure the diameter of the bubble.

6. An inflation molding machine equipped with a temperature measuring device according to any one of claims 1 to 5.

7. The inflation molding machine according to claim 6, wherein a plurality of the temperature measuring devices are arranged outside the bubble in the radial direction and spaced apart from each other in the circumferential direction of the bubble.

8. The inflation molding machine according to claim 6, further comprising a control device that uses the temperature of the bubble measured by the temperature measuring device as input information.

9. The inflation molding machine according to claim 8, wherein the control device calculates the frost line height of the bubble based on the temperature of the bubble as input information.

10. The inflation molding machine according to claim 8, wherein the control device controls the operation of the inflation molding machine based on the temperature of the bubble as input information so as to correct the non-uniformity of the heat distribution in the target area.

11. In inflation molding, in which a molding material is extruded and expanded by supplying fluid to the inside of the molding material to form bubbles, a method for non-contactly measuring the temperature of the bubbles, This includes forming an image of infrared light within a temperature detection range including the bubble using an infrared image sensor. A temperature measurement method comprising focusing on a portion of the target area within the temperature detection range and shifting the focus for at least a portion of the remaining non-target area when forming an image of the infrared radiation.

12. The bubble has a front bubble portion located closer to the infrared image sensor and a back bubble portion located further away from the infrared image sensor, separated by the front bubble portion. The temperature measurement method according to claim 11, wherein at least a portion of either the front bubble portion or the rear bubble portion is the target area, and at least a portion of the other of the front bubble portion or the rear bubble portion is the non-target area.

13. A method for measuring temperature according to claim 11 or 12, comprising changing the focal length.

14. The temperature measurement method according to claim 13, comprising measuring the diameter of the bubble by changing the focal length.

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