Electrode sheet drying device

Abstract

To continuously and accurately detect the temperature of an electrode sheet.SOLUTION: An infrared heater (6a) is arranged on one side of an electrode sheet (2) conveyed along a conveying path, and a radiation temperature sensor (11) is arranged on the other side of an electrode sheet (2), and the temperature of the rear surface of the electrode sheet that is the rear side of the surface portion of the electrode sheet closest to the infrared heater is measured by the radiation temperature sensor (11). An electrode sheet drying device is configured such that the peak wavelength of the infrared rays irradiated to the electrode sheet surface by the infrared heater is not included in the detection wavelength range of the infrared rays detected by the radiation temperature sensor (11).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to an electrode sheet drying apparatus. [Background technology]

[0002] When manufacturing lithium-ion batteries, it is sometimes necessary to heat the workpiece for the lithium-ion battery, such as an electrode sheet. This heating is sometimes performed on a moving electrode sheet using an infrared heater. In this case, the temperature of the electrode sheet surface closest to the infrared heater becomes the highest, and it is often necessary to detect the temperature in the electrode sheet surface region with the highest temperature, i.e., the highest temperature region of the electrode sheet. Therefore, a temperature control system is known that estimates the temperature in the highest temperature region of a moving electrode sheet using a radiation temperature sensor (see, for example, Patent Document 1). This radiation temperature sensor is configured to detect infrared rays incident on the radiation temperature sensor and measure the temperature of the surface of the object that emitted the infrared rays. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-37762 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, when measuring the temperature of the electrode sheet in its highest temperature region using a radiation temperature sensor, if infrared radiation emitted from structures surrounding the electrode sheet enters the radiation temperature sensor, this infrared radiation becomes a disturbance, making it impossible to accurately detect the temperature of the electrode sheet in its highest temperature region. Therefore, in the above-mentioned temperature management system, radiation temperature sensors are placed at a distance downstream of the infrared heater in the direction of movement of the electrode sheet, and a partition is placed between the infrared heater and the radiation temperature sensor to prevent disturbing infrared radiation from entering the radiation temperature sensor. The radiation temperature sensor measures the temperature of the electrode sheet as it has decreased from its highest temperature, calculates the amount of temperature decrease from the highest temperature, and predicts the highest temperature of the electrode sheet based on this calculated amount of temperature decrease. However, even if we predict the maximum temperature of the electrode sheet based on these calculated values, there is a problem in that we cannot accurately determine the maximum temperature of the electrode sheet. [Means for solving the problem]

[0005] To solve these problems, the present invention provides an electrode sheet drying apparatus for drying electrode sheets transported along a transport path, comprising an infrared heater located on one side of the electrode sheet and a radiation temperature sensor located on the other side of the electrode sheet, wherein the radiation temperature sensor is positioned so as to be able to measure the temperature of the back surface of the electrode sheet, which is the back surface of the electrode sheet closest to the infrared heater, and the apparatus is configured such that the peak wavelength of the infrared radiation irradiated onto the electrode sheet surface by the infrared heater does not fall within the detection wavelength range of the infrared radiation detected by the radiation temperature sensor. [Effects of the Invention]

[0006] The radiation temperature sensor makes it possible to continuously and accurately determine the temperature in the highest temperature range of the electrode sheet. [Brief explanation of the drawing]

[0007] [Figure 1]FIG. 1 is a side view schematically showing a first embodiment of an electrode sheet drying apparatus. [Figure 2] FIG. 2 is a partial plan view of the electrode sheet drying apparatus shown in FIG. 1. [Figure 3] FIG. 3 is a partial cross-sectional side view of an infrared heater. [Figure 4] FIG. 4 is a side view schematically showing a second embodiment of an electrode sheet drying apparatus. [Figure 5] FIG. 12 is a side view schematically showing a third embodiment of an electrode sheet drying apparatus. [Figure 6] FIG. 5 is a partial plan view of the electrode sheet drying apparatus shown in FIG. 3. [Figure 7] FIG. 7 is a side view showing a modified example of the electrode sheet drying apparatus shown in FIG. 5. [Figure 8] FIG. 8 is a side view showing a modified example of the electrode sheet drying apparatus shown in FIG. 5. [Figure 9] FIG. 9 is a diagram showing an example of a correction value ΔT. [Figure 10] FIG. 10 is a diagram showing a list of correction values ΔT. [Figure 11] FIG. 11 is a diagram for explaining a drying process procedure. [Figure 12] FIG. 12 is a flowchart for performing drying control. [Figure 13] FIG. 13 is a diagram showing a neural network. [Figure 14] FIG. 14 is a diagram showing a list of training data sets.

DETAILED DESCRIPTION OF THE INVENTION

[0008] Figure 1 provides an overall diagram of the first embodiment of the electrode sheet drying apparatus. Referring to Figure 1, 1 represents the drying oven, 2 represents the electrode sheet, 3 represents the unwinding roll for the electrode sheet 2, 4 represents the winding roll for the electrode sheet 2, and 5 represents the drive device for rotating the winding roll 4. When the winding roll 4 is rotated by the drive device 5, the electrode sheet 2 is continuously conveyed through the drying oven 1 from the unwinding roll 3 to the winding roll 4. While the electrode sheet 2 is being continuously conveyed through the drying oven 1, the drying process for the electrode sheet 2 is continuously performed within the drying oven 1. Although not shown in Figure 1, rollers for guiding the electrode sheet 2 and rollers for applying tension to the electrode sheet 2 may be installed as needed. In this case, the electrode sheet 2 can also be conveyed by other methods.

[0009] As can be seen from Figure 1 and Figure 2, which shows a plan view of the inside of the drying oven 1, the electrode sheet 2 extends in a strip shape in the transport direction with a uniform width. In the embodiments shown in Figures 1 and 2, this electrode sheet 2 consists of an electrode sheet used to manufacture lithium-ion secondary batteries, nickel-metal hydride batteries, etc. During the manufacture of these batteries, drying is required at various stages, and therefore, there are various forms of electrode sheets 2 to be dried depending on the manufacturing stage. In the embodiments of the present invention, these various forms of electrode sheets 2 are collectively referred to as electrode sheets 2.

[0010] That is, the electrode sheet 2 shown in FIGS. 1 and 2 is, for example, a metal foil with no electrode material coated on both sides thereof, a metal foil with an electrode material made of a positive electrode active material or a negative electrode active material coated on one side and no electrode material coated on the other side, or a metal foil with an electrode material made of a positive electrode active material coated on one side and an electrode material made of a negative electrode active material coated on the other side. In any case, if moisture adheres to the metal foil or is contained in the electrode material, the performance of the manufactured battery will be significantly deteriorated. Therefore, at the time of manufacturing the battery, a drying operation of the electrode sheet 2 is required to remove moisture, and the drying furnace 1 shown in FIGS. 1 and 2 is used for this drying operation of the electrode sheet 2.

[0011] Referring to FIGS. 1 and 2, the drying furnace 1 includes a plurality of infrared heaters 6a, 6b, 6c, 6d, 6e arranged on both sides of the electrode sheet 2. The infrared heaters 6a, 6b, 6c arranged above the electrode sheet 2 and the infrared heaters 6d, 6e arranged below the electrode sheet 2 are arranged at intervals along the conveyance path of the electrode sheet 2. In this case, in the examples shown in FIGS. 1 and 2, when viewed along the conveyance path of the electrode sheet 2, the infrared heaters 6d, 6e arranged below the electrode sheet 2 are located in the middle of the infrared heaters 6a, 6b, 6c arranged above the electrode sheet 2, and the infrared heaters 6a, 6b, 6c arranged above the electrode sheet 2 and the infrared heaters 6d, 6e arranged below the electrode sheet 2 are arranged alternately along the conveyance path of the electrode sheet 2.

[0012] In some electrode sheet drying devices, the electrode sheet 2 may be arranged so that it extends vertically. In this case, multiple infrared heaters are placed on both sides of the electrode sheet 2, spaced laterally from the electrode sheet 2. In the examples shown in Figures 1 and 2, when the electrode sheet drying device is viewed from above, one lower infrared heater 6d and 6e are placed between the upper infrared heaters 6a and 6b and the infrared heaters 6b and 6c, respectively. However, in this case, when the electrode sheet drying device is viewed from above, it is also possible to place multiple lower infrared heaters between the upper infrared heaters 6a and 6b and the infrared heaters 6b and 6c, and it is also possible to place multiple upper infrared heaters between the lower infrared heaters 6d and 6e, when the electrode sheet drying device is viewed from above.

[0013] Figure 3 shows a partial cross-sectional side view of the infrared heaters 6a, 6b, 6c, 6d, and 6e shown in Figures 1 and 2. Referring to Figure 3, the infrared heaters 6a, 6b, 6c, 6d, and 6e comprise a hollow cylindrical quartz tube 7, end casings 8 attached to both ends of the quartz tube 7, and a filament 9 placed inside the quartz tube 7 and extending from one end casing 8 to the other. The filament 9 is a filament that emits infrared rays with a peak wavelength of 4 μm or less, and this filament 9 is made of tungsten, carbon, Kanthal, etc. On the other hand, the quartz tube 7 is a quartz tube that does not transmit infrared rays with a wavelength of 5 μm or more. Note that the infrared heaters 6a, 6b, 6c, 6d, and 6e shown in Figure 3 are examples, and infrared heaters with other structures can also be used.

[0014] On the other hand, as shown in Figure 1, the electrode sheet drying apparatus is equipped with an electronic control unit 10 having a memory consisting of ROM and RAM and a microprocessor. The drive unit 5 and infrared heaters 6a, 6b, 6c, 6d, and 6e are connected to this electronic control unit 10, and the drive unit 5 and infrared heaters 6a, 6b, 6c, 6d, and 6e are controlled by the output signals of the electronic control unit 10. When power is supplied to the infrared heaters 6a, 6b, 6c, 6d, and 6e, infrared rays are emitted from each infrared heater 6a, 6b, 6c, 6d, and 6e, and the electrode sheets 2 that are continuously conveyed inside the drying oven 1 from the unwinding roll 3 to the winding roll 4 are heated by the infrared rays emitted from each infrared heater 6a, 6b, 6c, 6d, and 6e. This heating action by infrared rays removes moisture adhering to or retained on the electrode sheets 2, and the electrode sheets 2 are dried. When infrared radiation is emitted from each of the infrared heaters 6a, 6b, 6c, 6d, and 6e, the temperature of the surface area of ​​the electrode sheet 2 closest to each infrared heater 6a, 6b, 6c, 6d, and 6e becomes the highest. In this case, the higher the temperature of the electrode sheet 2, the more effectively the electrode sheet 2 can be dried. However, if the temperature of the electrode sheet 2 becomes too high, problems such as thermal degradation occur. Therefore, there is an optimal temperature for the electrode sheet 2 in its highest temperature range.

[0015] In the example shown in Figure 1, the filaments 9 of each infrared heater 6a, 6b, 6c, 6d, and 6e reach a high temperature of approximately 2100°C, and the optimal temperature T0 in the highest temperature region of the electrode sheet 2 is, for example, approximately 150°C. This optimal temperature T0 differs depending on the form of the electrode sheet 2 and the drying stage. However, in order to effectively dry the electrode sheet 2 without causing problems, it is necessary to control the temperature in the highest temperature region of the electrode sheet 2 to the optimal temperature T0, and for this purpose, it is necessary to accurately measure the temperature in the highest temperature region of the electrode sheet 2. In this case, it is practically difficult to measure the temperature in the highest temperature region of a moving electrode sheet 2 using a temperature sensor that directly contacts the electrode sheet 2, so it is necessary to measure the temperature in the highest temperature region of the electrode sheet 2 non-contact.

[0016] On the other hand, a low-temperature radiation temperature sensor that detects infrared radiation with a wavelength in the range of 8 μm to 14 μm to measure temperature is known and already commercially available as a sensor that can appropriately measure temperatures of around 150°C in a non-contact manner.Therefore, in the embodiment of the present invention, a radiation temperature sensor capable of detecting infrared radiation with a wavelength in the range of 8 μm to 14 μm to measure temperature is used to detect the temperature in the highest temperature region of the electrode sheet 2.This radiation temperature sensor incorporates, for example, a detection element that rises in temperature when it absorbs infrared radiation and generates an electrical signal corresponding to the temperature, and the temperature of the surface of an object emitting infrared radiation is measured by this detection element.That is, this radiation temperature sensor is configured to detect infrared radiation incident on the radiation temperature sensor and measure the temperature of the surface of an object emitting infrared radiation.

[0017] Incidentally, the thermal conductivity of the metal foil constituting the electrode sheet 2 is high, and the electrode sheet 2 is thin, so the temperature in the highest temperature region of the electrode sheet 2 is almost equal on both the upper and lower surfaces. Therefore, in the embodiment of the present invention, for example, when measuring the temperature in the highest temperature region of the electrode sheet 2 due to the heating action of the infrared heater 6b, the above-mentioned radiation temperature sensor 11 is placed directly below the infrared heater 6b and below the electrode sheet 2, that is, on the opposite side of the electrode sheet 2 from the infrared heater 6b. The reason why the radiation temperature sensor 11 can be placed in this way is that the infrared heaters 6a, 6b, and 6c placed above the electrode sheet 2 and the infrared heaters 6d and 6e placed below the electrode sheet 2 are arranged alternately along the transport path of the electrode sheet 2. In the example shown in Figure 1, the infrared heater 6b and the radiation temperature sensor 11 are placed on the same perpendicular line perpendicular to the surface of the electrode sheet 2. In this case, the upper surface of the radiation temperature sensor 11 is the infrared intake port 11a. By arranging the radiation temperature sensor 11 in this manner, even if the electrode sheet 2 moves vertically, it becomes possible to reliably measure the temperature of the back surface of the electrode sheet 2 that is closest to the infrared heater 6b.

[0018] On the other hand, as mentioned above, the quartz tubes 7 surrounding the filaments 9 of each infrared heater 6a, 6b, 6c, 6d, and 6e are made of quartz tubes that do not transmit infrared rays with wavelengths of 5 μm or longer. Therefore, the infrared rays emitted from the filaments 9 and passing through the quartz tubes 7 are infrared rays with wavelengths of 5 μm or less. However, as mentioned above, the filaments 9 of each infrared heater 6a, 6b, 6c, 6d, and 6e reach a high temperature of about 2100°C, and at this time, the temperature of the quartz tubes 7 is about 700°C. When the temperature of the quartz tubes 7 becomes this high, infrared rays are emitted from the quartz tubes 7 themselves, and at this time, infrared rays with wavelengths of 5 μm or longer are emitted from the quartz tubes 7. When these infrared rays enter the infrared intake port 11a of the radiation temperature sensor 11, these infrared rays become a disturbance, causing the radiation temperature sensor 11 to make a false detection.

[0019] Furthermore, when infrared radiation emitted from each infrared heater 6a, 6b, 6c, 6d, 6e is reflected by the furnace wall of the drying oven 1 or the surface of the electrode sheet 2, and the reflected infrared radiation is incident on the radiation temperature sensor 11, this infrared radiation becomes a disturbance and causes the radiation temperature sensor 11 to make a false detection. Therefore, in order to minimize such false detections, in the embodiment of the present invention, the peak wavelength of the infrared radiation irradiated onto the surface of the electrode sheet 2 by the infrared heaters 6a, 6b, 6c, 6d, 6e and the detection wavelength range of the infrared radiation detected by the radiation temperature sensor 11 are set so that the peak wavelength of the infrared radiation irradiated onto the surface of the electrode sheet 2 by the infrared heaters 6a, 6b, 6c, 6d, 6e is not included in the detection wavelength range of the infrared radiation detected by the radiation temperature sensor 11. In this case, in the embodiment of the present invention, the peak wavelength of the infrared radiation emitted from the infrared heaters 6a, 6b, 6c, 6d, 6e is set to 4 μm or less, and the detection wavelength range of the infrared radiation is set to the range of 8 μm to 14 μm.

[0020] As described above, in the embodiment of the present invention, an electrode sheet drying apparatus for drying an electrode sheet 2 transported along a transport path comprises an infrared heater 6b positioned on one side of the electrode sheet 2 and a radiation temperature sensor 11 positioned on the other side of the electrode sheet 2. The radiation temperature sensor 11 is positioned to measure the temperature of the back surface of the electrode sheet 2, which is the back surface of the electrode sheet 2 closest to the infrared heater 6b. The peak wavelength of infrared radiation irradiated onto the electrode sheet 2 surface by the infrared heaters 6a, 6b, 6c, 6d, and 6e is not included in the detection wavelength range of infrared radiation detected by the radiation temperature sensor 11.

[0021] Next, a second embodiment of the electrode sheet drying apparatus will be described with reference to Figure 4. Referring to Figure 4, in this second embodiment, in order to further prevent infrared rays reflected from the furnace wall and the surface of the electrode sheet 2 from entering the radiation temperature sensor 11, the radiation temperature sensor 11 is placed inside a housing 12 covered with a surrounding wall that does not transmit infrared rays. The top of this housing 12 is open in order to allow infrared rays emitted from the back surface of the electrode sheet 2, which is the back surface of the electrode sheet 2 closest to the infrared heater 6b, to enter the infrared intake port 11a of the radiation temperature sensor 11. It is preferable that the surrounding wall of the housing 12 be made of a heat insulating material.

[0022] When the radiation temperature sensor 11 is placed inside the housing 12 in this manner, infrared rays reflected from the furnace wall and the surface of the electrode sheet 2 are suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11. In other words, infrared rays that would disturb the detection wavelength range of the radiation temperature sensor 11 are suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11. As a result, it becomes possible to continuously and appropriately measure the temperature in the highest temperature region of the moving electrode sheet 2.

[0023] Next, a third embodiment of the electrode sheet drying apparatus will be described with reference to Figures 5 and 6. In this third embodiment, various further measures are taken to further prevent infrared rays reflected from the furnace wall and the surface of the electrode sheet 2 from entering the radiation temperature sensor 11. Referring to Figures 5 and 6, in this third embodiment, window materials 13a, 13b, 13c, 13d, and 13e that do not transmit infrared rays with a wavelength of 5 μm or longer are placed between each of the infrared heaters 6a, 6b, 6c, 6d, and 6e and the electrode sheet 2. These window materials 13a, 13b, 13c, 13d, and 13e are made of quartz glass or tempered glass that do not transmit infrared rays with a wavelength of 5 μm or longer.

[0024] In the example shown in Figure 5, the window materials 13a, 13b, 13c, 13d, and 13e are thin, flat plates positioned parallel to the electrode sheet 2 at a distance from it. Each window material 13a, 13b, 13c, 13d, and 13e extends along the entire width of the electrode sheet 2 and is rectangular in shape, extending by the same length from the corresponding infrared heaters 6a, 6b, 6c, 6d, and 6e in both the transport direction and the reverse direction of the electrode sheet 2. These window materials 13a, 13b, 13c, 13d, and 13e also serve to prevent the electrode sheet 2 from coming into contact with the infrared heaters 6a, 6b, 6c, 6d, and 6e.

[0025] On the other hand, as shown in Figure 5, the drying oven 1 is equipped with a blower 14 for flowing dry air with a dew point of, for example, -40°C or lower along the upper and lower surfaces of the electrode sheet 2. In the embodiment shown in Figure 5, the blower 14 is equipped with a pair of nozzles 14a and 14b at the downstream end of the electrode sheet 2 inside the drying oven 1, which blow dry air upstream along the upper and lower surfaces of the electrode sheet 2, and a blower 15 that supplies dry air to each nozzle 14a and nozzle 14b. Also, as shown in Figure 6, nozzle 14a extends along the entire width of the electrode sheet 2. Similarly, nozzle 14b also extends along the entire width of the electrode sheet 2. This blower 15 is connected to an electronic control unit 10, and the operation of the blower 15 is controlled by an output signal from the electronic control unit 10.

[0026] Dry air is circulated from each nozzle 14a and nozzle 14b along the upper and lower surfaces of the electrode sheet 2 toward the upstream side of the electrode sheet 2, removing moisture from the electrode sheet 2 and cooling each of the window materials 13a, 13b, 13c, 13d, and 13e. In the first embodiment shown in Figure 1 and the second embodiment shown in Figure 4, such a blower 14 is not provided, but in these first embodiment shown in Figure 1 and the second embodiment shown in Figure 4, a blower 14 as shown in Figure 5 can be provided.

[0027] On the other hand, in the example shown in Figure 5, the upper part of the housing 12 is covered by a top wall, and an opening 16 is formed in this top wall to allow infrared radiation emitted from the back surface of the electrode sheet 2, which is the back surface of the electrode sheet 2 closest to the infrared heater 6b, to enter the infrared intake port 11a of the radiation temperature sensor 11. That is, in the example shown in Figure 5, in addition to the infrared heater 6b and the radiation temperature sensor 11, the opening 16 is arranged on the same perpendicular line perpendicular to the surface of the electrode sheet 2. Also, in the example shown in Figure 5, a cooling device 17 is installed inside the housing 12 to supply cooling air to cool the inner wall surface of the housing 12 and the radiation temperature sensor 11. This cooling device 17 comprises a cooling air inlet 18 into the housing 12 and a blower 19 that supplies cooling air to the cooling air inlet 18, and the cooling air supplied into the housing 12 from the cooling air inlet 18 cools the inner wall surface of the housing 12 and the radiation temperature sensor 11. This blower 19 is connected to the electronic control unit 10, and the operation of this blower 19 is controlled by the output signal of the electronic control unit 10.

[0028] On the other hand, an infrared cut filter 20 is placed between the opening 16 formed in the top wall of the housing 12 and the electrode sheet 2 to cut infrared rays with wavelengths shorter than the detection wavelength range of the radiation temperature sensor 11, for example, infrared rays of 5 μm or less. This infrared cut filter 20 is made using CaF2, BaF2, etc. In the example shown in Figure 5, this infrared cut filter 20 is also a thin, flat plate that is spaced apart from the electrode sheet 2 and arranged parallel to the electrode sheet 2. The infrared cut filter 20 extends along the entire width of the electrode sheet 2 and is rectangular in shape, extending by the same length from the opening 16 in the direction of transport of the electrode sheet 2 and in the opposite direction. Note that the infrared cut filter 20 shown in Figure 5 is just one example, and it is sufficient for this infrared cut filter 20 to cover at least the opening 16 of the housing 12.

[0029] In the third embodiment shown in Figures 5 and 6, infrared rays with wavelengths of 5 μm or more emitted from the quartz tube 7 itself are blocked by each of the window materials 13a, 13b, 13c, 13d, and 13e. Furthermore, since each of the window materials 13a, 13b, 13c, 13d, and 13e is cooled by dry air, each of the window materials 13a, 13b, 13c, 13d, and 13e itself does not emit strong infrared rays with wavelengths of 5 μm or more. Consequently, the reflection of infrared rays with wavelengths of 5 μm or more from the surface of the electrode sheet 2 is suppressed, and infrared rays with wavelengths of 5 μm or more reflected from the surface of the electrode sheet 2, i.e., infrared rays that disturb the detection wavelength range of the radiation temperature sensor 11, are suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11.

[0030] On the other hand, some of the infrared radiation with a wavelength of 5 μm or less that reaches the surface of the electrode sheet 2 is reflected by the surface of the electrode sheet 2 and heats the surrounding structures such as the furnace wall. However, since the inside of the drying furnace 1 is cooled by dry air, strong infrared radiation with a wavelength of 5 μm or more is not emitted from the surrounding structures such as the furnace wall, and therefore, infrared radiation that would disturb the detection wavelength range of the radiation temperature sensor 11 is suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11.

[0031] Furthermore, if infrared radiation with a wavelength of 5 μm or less reflected from the surface of the electrode sheet 2 enters the housing 12 through the opening 16 formed in the top wall of the housing 12, the inner wall surface of the housing 12 will be heated by this infrared radiation. However, an infrared cut filter 20 that cuts infrared radiation with a wavelength shorter than the detection wavelength range of the radiation temperature sensor 11, for example, infrared radiation with a wavelength of 5 μm or less, is placed between the opening 16 and the electrode sheet 2, so that infrared radiation with a wavelength of 5 μm or less reflected from the surface of the electrode sheet 2 does not enter the housing 12. In addition, the inner wall surface of the housing 12 is cooled by the cooling air flowing in from the cooling air inlet 18. Therefore, strong infrared radiation with a wavelength of 5 μm or more is not emitted from the inner wall surface of the housing 12, and therefore, infrared radiation that would disturb the detection wavelength range of the radiation temperature sensor 11 is suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11. The infrared cut filter 20 is also cooled by the cooling air flowing out from the opening 16. Therefore, strong infrared radiation with a wavelength of 5 μm or more is not emitted from the infrared cut filter 20, and consequently, infrared radiation that would disturb the detection wavelength range of the radiation temperature sensor 11 is suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11. Furthermore, if a metal foil is used as the electrode sheet 2, a carbon coating layer can be formed on the metal foil to suppress the reflection of infrared radiation on the surface of the electrode sheet 2.

[0032] Thus, in this third embodiment, infrared radiation that disturbs the detection wavelength range of the radiation temperature sensor 11 is suppressed from entering the infrared intake port 11a of the radiation temperature sensor 11. Therefore, in this third embodiment, the radiation temperature sensor 11 can continuously and more accurately measure the temperature in the highest temperature region of the moving electrode sheet 2.

[0033] Figures 7 and 8 show modifications of the third embodiment shown in Figure 5. Referring first to the modification shown in Figure 7, in this modification, in addition to temperature detector A, which consists of a radiation temperature sensor 11, housing 12, opening 16, cooling air inlet 18 and infrared cut filter 20, similar to the third embodiment shown in Figure 5, temperature detectors B and C are installed above the electrode sheet 2. As can be seen from Figure 7, temperature detectors B and C have the same structure as temperature detector A, with the infrared cut filter 20 positioned to cover the opening 16.

[0034] Furthermore, in the modified example shown in Figure 7, temperature detector B is positioned to measure the temperature of the upper surface of electrode sheet 2, which is on the back side of the electrode sheet surface portion closest to the infrared heater 6e, using the radiation temperature sensor 11. Temperature detector C is positioned to measure the temperature of the upper surface of electrode sheet 2, which is on the back side of the electrode sheet surface portion closest to the infrared heater 6d, using the radiation temperature sensor 11. In this case, in temperature detector B, the infrared heater 6e and the radiation temperature sensor 11 are positioned on the same perpendicular line perpendicular to the surface of electrode sheet 2. In contrast, in temperature detector C, the housing 12 is positioned at an angle with respect to a perpendicular line perpendicular to the surface of electrode sheet 2 so that the highest temperature of electrode sheet 2 can be measured. That is, in this temperature detector C, the housing 12 is positioned at an angle so that the line Q passing through the infrared intake port 11a of the radiation temperature sensor 11 and the opening 16 of the housing 12 passes through the highest temperature point P on the upper surface of electrode sheet 2. In this way, multiple temperature detectors A, B, and C are positioned on both sides of electrode sheet 2 as needed.

[0035] Next, referring to the modified example shown in Figure 8, in this modified example, the window materials 13a, 13b, 13c, 13d, and 13e, which are placed between each infrared heater 6a, 6b, 6c, 6d, and 6e and the electrode sheet 2, have a curved shape that curves around the corresponding infrared heater 6a, 6b, 6c, 6d, and 6e. These window materials 13a, 13b, 13c, 13d, and 13e also extend along the entire width of the electrode sheet 2, and each window material 13a, 13b, 13c, 13d, and 13e is made of quartz glass or tempered glass that does not transmit infrared rays with a wavelength of 5 μm or longer.

[0036] However, even if the temperature in the highest temperature region of the moving electrode sheet 2 is continuously measured by the radiation temperature sensor 11, a discrepancy will actually occur between the measured temperature and the actual temperature. In this case, it is not a problem when the discrepancy is small, but it becomes a problem when the discrepancy is large. Next, we will explain a temperature estimation method that eliminates the discrepancy between the measured temperature and the actual temperature, and the drying control of the electrode sheet 2 based on this temperature estimation method, using the electrode sheet drying apparatus shown in Figure 5 as an example.

[0037] Figures 9 and 10 show an example of a temperature estimation method in which a correction value ΔT, which represents the difference between the measured temperature and the actual temperature, is determined in advance, and this correction value ΔT is used to estimate the temperature in the highest temperature region of the electrode sheet 2. Figure 9 shows the relationship between the correction value ΔT (vertical axis), which represents the temperature difference between the actual temperature in the highest temperature region of the electrode sheet 2 and the temperature measured by the radiation temperature sensor 11, and the average temperature (horizontal axis) of various components and structural elements such as the furnace wall around the radiation temperature sensor 11. In order to obtain this relationship, the temperature in the highest temperature region of the electrode sheet 2 is measured, for example, by a direct-contact thermocouple. Note that in Figure 9, the × marks indicate the case where the electrode sheet 2 is made of solid metal foil, the triangle marks indicate the case where a carbon coating layer is formed on the metal foil, and the circle marks indicate the case where an electrode material layer is formed on the metal foil.

[0038] Figure 9 shows that the correction value ΔT, which represents the temperature difference between the actual temperature and the temperature measured by the radiation temperature sensor 11, changes depending on the form of the electrode sheet 2 (solid metal foil, metal foil with a carbon coating layer, or metal foil with an electrode material layer, etc.) and the temperature of various components around the radiation temperature sensor 11 and structural elements such as the furnace wall. Therefore, in this temperature estimation method, for each form of the electrode sheet 2, for example, the correction value ΔT for each temperature range (T1-T2, T2-T3, ...) at the furnace wall temperature TX and each temperature range (T1-T2, T2-T3, ...) at the window material TY of 13a, 13b, 13c, 13d, or 13e is calculated. 11 ,ΔT 12 ...is determined in advance through experiments, and a list like the one shown in Figure 10 is created based on this.

[0039] In Figure 10, the furnace wall temperature TX and the window material temperatures TY 13a, 13b, 13c, 13d, or 13e are used as temperature factors influencing the correction value ΔT. However, other temperature factors also exist that affect the correction value ΔT. Therefore, in practice, a multidimensional list of the correction value ΔT is created as a function of numerous temperature factors, including the furnace wall temperature TX and the window material temperatures TY 13a, 13b, 13c, 13d, or 13e. This multidimensional list of the correction value ΔT is used to estimate the temperature in the highest temperature region of the moving electrode sheet 2. This multidimensional list of the correction value ΔT is stored in the memory of the electronic control unit 10.

[0040] Next, the procedure for drying the electrode sheet 2 using the electrode sheet drying apparatus will be described with reference to Figure 11. Referring to Figure 11, as shown in S1, the shape of the object to be dried, i.e., the electrode sheet 2, is input to the electronic control unit 10. Once the object to be dried is input to the electronic control unit 10, the drying process of the electrode sheet 2 is started, as shown in S2. When the drying process of the electrode sheet 2 is started, the drying control routine for the electrode sheet 2 shown in Figure 12 is executed in the electronic control unit 10 by interrupts at regular intervals.

[0041] Referring to Figure 12, first, in step 50, a number of temperature factors, including the furnace wall temperature TX and the window material temperatures TY 13a, 13b, 13c, 13d, or 13e, are detected by the temperature sensor. Next, in step 51, a correction value ΔT is calculated from the number of temperature factors, including the furnace wall temperature TX and the window material temperatures TY 13a, 13b, 13c, 13d, or 13e, based on a multidimensional list of correction values ​​ΔT stored in the memory of the electronic control unit 10. Next, in step 52, the sensor-detected temperature Ts measured by the radiation temperature sensor 11 is read. Next, in step 53, the estimated temperature Tt in the highest temperature region of the electrode sheet 2 is calculated by subtracting the correction value ΔT from the sensor-detected temperature Ts.

[0042] Next, in step 54, it is determined whether the estimated temperature Tt in the highest temperature region of the electrode sheet 2 is greater than To + α, which is the optimal temperature To in the highest temperature region of the electrode sheet 2 plus a small constant value α. If it is determined that the estimated temperature Tt is greater than To + α, the process proceeds to step 56, where the drive control of the drive unit 5 is performed so that the transport speed V of the electrode sheet 2 is increased by ΔV. When the transport speed V of the electrode sheet 2 is increased, the temperature in the highest temperature region of the electrode sheet 2 decreases.

[0043] On the other hand, if in step 54 it is determined that the estimated temperature Tt is not greater than To + α, the process proceeds to step 55 to determine whether the estimated temperature Tt in the highest temperature region of the electrode sheet 2 is less than To - α, which is obtained by subtracting a constant value α from the optimal temperature To in the highest temperature region of the electrode sheet 2. If it is determined that the estimated temperature Tt is less than To - α, the process proceeds to step 57 to control the drive of the drive device 5 so that the transport speed V of the electrode sheet 2 is reduced by ΔV. When the transport speed V of the electrode sheet 2 is reduced, the temperature in the highest temperature region of the electrode sheet 2 rises. In this way, the temperature in the highest temperature region of the electrode sheet 2 is controlled to the optimal temperature To.

[0044] Figures 13 and 14 show another example of a temperature estimation method in which the temperature in the highest temperature region of the electrode sheet 2 is estimated based on the temperature measured by the radiation temperature sensor 11 and a number of temperature factors including the temperatures of the furnace wall and the window materials 13a, 13b, 13c, 13d or 13e using a neural network. Figure 13 shows the neural network 60. Referring to Figure 13, in the neural network 60, L = 1 represents the input layer, L = 2 and L = 3 represent the hidden layers, and L = 4 represents the output layer. Also, in Figure 13, the input values x1, x 2··· x n-1、 x n of the input parameters input to each node of the input layer (L = 1), and the output value y output from the node of the output layer (L = 4) are shown.

[0045] On the other hand, Figure 14 shows a training data set created using the input values x1, x 2··· x n-1、 x n of each input parameter and the teacher data, that is, the correct label yt, for learning the weights of the neural network 60. The training data set shown in Figure 14 lists m data from No. 1 to No. m, and this training data set is created for each form of the electrode sheet 2 (solid metal foil, metal foil having a carbon coat layer, or metal foil having an electrode material layer, etc.). As the input parameters, in addition to a number of temperature factors including the temperatures of the furnace wall and the window materials 13a, 13b, 13c, 13d or 13e, the temperature measured by the radiation temperature sensor 11 is used, and the estimated value of the temperature in the highest temperature region of the electrode sheet 2 becomes the output value y.

[0046] For example, the input values x1, x 2··· x n-1、 x nThese include, for example, the measured temperatures of the furnace wall when the temperature of the dry air blown out from nozzles 14a and 14b, and the temperature of the cooling air sent into the shade 12 from the cooling air inlet 18 are varied, the measured temperatures of the window materials 13a, 13b, 13c, 13d, or 13e, the measured temperatures of the quartz tubes 7 of the infrared heaters 6a, 6b, 6c, 6d, and 6e, the measured temperatures of the inner wall surface of the housing 12, the measured temperatures of the dry air blown out from nozzles 14a and 14b, the measured temperatures of the cooling air sent into the housing 12 from the cooling air inlet 18, the measured temperatures of the infrared cut filter 20, the measured transport speed of the electrode sheet 2, the measured temperature inside the drying oven 1, the measured humidity inside the drying oven 1, the measured atmospheric pressure, and the values ​​measured by the radiation temperature sensor 11, which are No. 1 to No. m in the training dataset. The training data up to this point, i.e., the correct label yt, is the measured temperature in the highest temperature region of electrode sheet 2 at that time.

[0047] Next, we will briefly explain how to learn the weights of the neural network 60 using this training dataset. This neural network 60 is created within the electronic control unit 10, and the learning of the weights of the neural network 60 is performed within the electronic control unit 10. For example, first, the input value x1...x of the first (No. 1) of the training dataset n This is input to each node of the input layer (L=1) of the neural network 60. At this time, the output value y is output from the nodes of the output layer (L=4) of the neural network 60. Next, the squared error E = 1 / 2(y-yt) is calculated, which represents the error between this output value y and the correct label yt. 2 The squared error E is calculated, and the weights of the neural network 60 are trained using backpropagation so that this squared error E is minimized.

[0048] Once the weight training of the neural network 60 based on the first (No. 1) data of the training dataset is complete, the weight training of the neural network 60 based on the second (No. 2) data of the training dataset is then performed using backpropagation. Similarly, the weight training of the neural network 60 is performed sequentially up to the mth (No. m) data of the training dataset. This weight training of the neural network 60 is repeated until the squared error E is less than or equal to a preset setting error, and finally, a maximum temperature model that estimates the temperature in the highest temperature region of the electrode sheet 2 is created by the neural network 60 in the electronic control unit 10. During the drying process of the electrode sheet 2, the input values ​​x1 and x of each input parameter measured are used. 2··· x n-1、 x n When this is input to the electronic control unit 10, an estimated temperature in the highest temperature region of the electrode sheet 2 is output using this maximum temperature model. When the neural network 60 is used, this estimated value is used as the estimated temperature Tt in the drying control routine of the electrode sheet 2 shown in Figure 12.

[0049] Thus, in the methods for estimating the temperature in the highest temperature region of the electrode sheet 2 shown in Figures 9 and 10, and the methods for estimating the temperature in the highest temperature region of the electrode sheet 2 shown in Figures 13 and 14, various temperatures are detected, including the temperature of the structure around the radiation temperature sensor 11, which affects the measurement value by the radiation temperature sensor 11. Based on the detected values ​​of various temperatures, including the temperature of the structure around the radiation temperature sensor 11, the temperature of the back surface of the electrode sheet, which is the back side of the electrode sheet surface closest to the infrared heater, is estimated. [Explanation of symbols]

[0050] 1 Drying oven 2 electrode sheets 6a, 6b, 6c, 6d, 6e Infrared Heater 11. Radiation temperature sensor 12 Housing

Claims

1. An electrode sheet drying apparatus for drying electrode sheets transported along a transport path, comprising an infrared heater positioned on one side of the electrode sheet and a radiation temperature sensor positioned on the other side of the electrode sheet, wherein the radiation temperature sensor is positioned so as to be able to measure the temperature of the back surface of the electrode sheet, which is the back surface of the electrode sheet portion closest to the infrared heater, and the apparatus is configured such that the peak wavelength of the infrared radiation irradiated onto the electrode sheet surface by the infrared heater does not fall within the detection wavelength range of the infrared radiation detected by the radiation temperature sensor.

2. The electrode sheet drying apparatus according to claim 1, wherein the infrared heater and the radiation temperature sensor are arranged on the same perpendicular line perpendicular to the surface of the electrode sheet.

3. The electrode sheet drying apparatus according to claim 1, wherein the peak wavelength of infrared radiation emitted from the infrared heater is 4 μm or less, and the detection wavelength range of infrared radiation detected by the radiation temperature sensor is in the range of 8 μm to 14 μm.

4. The electrode sheet drying apparatus according to claim 1, wherein the infrared heater has a hollow cylindrical quartz glass tube extending in the width direction of the electrode sheet and a filament disposed inside the quartz glass tube that emits infrared rays, and a flat or curved window material is disposed between the infrared heater and the electrode sheet to cut infrared rays with wavelengths greater than the peak wavelength of infrared rays emitted from the infrared heater, and the window material extends over a certain width in the direction of transport of the electrode sheet and the opposite direction from the infrared heater.

5. The electrode sheet drying apparatus according to claim 4, further comprising a blower for flowing dry air along the surface of the electrode sheet, wherein the window material is cooled by the dry air.

6. The electrode sheet drying apparatus according to claim 1, wherein the radiation temperature sensor is disposed within a housing having a surrounding wall that does not transmit infrared rays, and the housing has an opening for allowing infrared rays emitted from the back surface of the electrode sheet, which is on the back side of the electrode sheet surface portion closest to the infrared heater, to enter the radiation temperature sensor.

7. The electrode sheet drying apparatus according to claim 6, wherein an infrared filter is placed between the opening and the electrode sheet to cut out infrared rays with wavelengths shorter than the detection wavelength range of infrared rays detected by the radiation temperature sensor.

8. The electrode sheet drying apparatus according to claim 6, further comprising a cooling device for cooling the radiation temperature sensor.

9. The electrode sheet drying apparatus according to claim 1, wherein a plurality of infrared heaters are arranged on both sides of the electrode sheet at intervals along the transport path of the electrode sheet, and in the transport direction of the electrode sheet, the infrared heaters arranged on one side of the electrode sheet are arranged between the infrared heaters arranged on the other side of the electrode sheet.

10. The electrode sheet drying apparatus according to claim 1, which detects various temperatures, including the temperature of a structure around the radiation temperature sensor that affects the measurement value by the radiation temperature sensor, and estimates the temperature of the back surface of the electrode sheet, which is on the back side of the electrode sheet surface portion closest to the infrared heater, based on the detected values ​​of various temperatures, including the temperature of the structure around the radiation temperature sensor.

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