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`EX 1008
`EX 1008
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`(19) Japanese Patent Office (JP)
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`(12) Published Patent Gazette (A)
`
`(51) Int. C1.
`F26B 5/04 (2006.01)
`F26B 25/00 (2006.01)
`HO1M 4/04 (2006.01)
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`FI
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`F26B 5/04
`F26B 25/00
`F26B 25/00
`HO1M 4/04
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`A
`B
`Z
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`(11) Japanese Patent Application
`Publication No.
`Japanese Unexamined Patent Application
`Publication Official Gazette No. 2016-
`80284
`(P2016-80284A)
`(43) Publication date 5.16.2016
`Theme Code (Reference)
`3L113
`5H050
`
`Examination Request: Not yet made; Number of Claims: 16 OL (Total 14 pages)
`(21) Application No.: Patent Application No. 2014-213414
`(71) Applicant: 507317502
`(P2014-213414)
`ELIIY Power Co., Ltd.
`(22) Application Date: 10.20.2014
`1-6-4 Osaki, Shinagawa-ku, Tokyo, Japan
`100122426
`Patent Attorney: Kiyoshi Kato
`(72) Inventor: Yosuke Moriguchi
`1-6-4 Osaki, Shinagawa-ku, Tokyo, Japan
`Inside ELIIY Power Co., Ltd.
`F-Term (Reference) 3L113 AA01 AB10 AC23 AC67 BA04
`CA16 CA20 CB15 DA24
`5H050 AA19 BA16 BA17 GA02 GA27
`GA28 GA29 HA15
`
`(74) Agent:
`
`(54) [Title of Invention] Vacuum drying device, vacuum drying system, vacuum drying method and manufacturing method of battery
`electrodes
`
`(57) [Abstract]
`[Problem to be Solved] To complete vacuum drying in the optimal
`state.
`[Means for Solving the Problem] The vacuum drying device 1 is
`equipped with a drying furnace 11, a pressure measurement
`section 12, a determination section 13, a vacuum drying control
`section 14, and a judgment section 15, and it performs vacuum
`drying on battery electrodes arranged inside the drying furnace
`11. The pressure measurement section 12 measures the pressure
`inside the drying furnace 11. The determination section 13
`determines whether the pressure measured by the pressure
`measurement section 12 is below the target pressure. The vacuum
`drying control section 14 continues the vacuum drying for a first
`period of time after it has been determined by the determination
`section 13
`that
`the pressure measured by
`the pressure
`measurement section 12 is below the target pressure. The
`judgment section 15 concludes that the vacuum drying of the
`battery electrodes is complete when it is determined by the
`determination section 13 that the pressure measured by the
`pressure measurement section 12 is below the target pressure after
`the first period of time has elapsed.
`[Selected representative diagram] Fig. 1
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`[Scope of Patent Claims ]
`[Claim 1]
`A vacuum drying device that performs vacuum drying on an object to be dried arranged in a drying furnace, comprising:
`a pressure measurement means for measuring the pressure inside the aforementioned drying furnace;
`a determination means for determining whether the pressure measured by the aforementioned pressure measurement means
`has decreased to below or less than a predetermined target pressure;
`a vacuum drying control means that continues vacuum drying for a predetermined first period of time after it has been
`determined by the aforementioned determination means that the pressure measured by the aforementioned pressure
`measurement means is below or less than the aforementioned target pressure; and
`a judgment means that judges that the vacuum drying of the aforementioned object to be dried is complete when the
`pressure measured by the aforementioned pressure measurement means is determined by the aforementioned determination
`means to be below or less than the aforementioned target pressure after the aforementioned first period of time has elapsed.
`[Claim 2]
`A vacuum drying device described in Claim 1, comprising a time-counting means for measuring the time since the start of
`the vacuum drying of the aforementioned object to be dried, wherein during the period until the time measured by the
`aforementioned time-counting means exceeds a predetermined second period of time, the determination by the aforementioned
`determination means is suspended.
`[Claim 3]
`A vacuum drying device described in Claim 1 or 2, wherein if the environment in which the aforementioned object to be
`dried is placed after the completion of vacuum drying is referred to as the predetermined environment, the aforementioned
`target pressure is set lower than the saturation vapor pressure at the dew point in the aforementioned predetermined environment.
`[Claim 4]
`A vacuum drying device described in Claim 3, wherein if the dew point (in degrees Celsius) in the aforementioned
`predetermined environment is denoted as t, and predetermined constants are denoted as a and b, the saturation vapor pressure
`e at the dew point in the aforementioned predetermined environment is determined using the following mathematical formula
`(1):
`[Mathematical formula 1]
`
`[Claim 5]
`A vacuum drying device described in Claim 3 or 4, wherein how much lower than the saturation vapor pressure at the dew
`point in the aforementioned predetermined environment the aforementioned target pressure is set is determined according to
`the material of the aforementioned object to be dried.
`[Claim 6]
`A vacuum drying device described in any one of Claims 1 to 5, wherein the aforesaid determination means performs
`abnormality detection of the aforementioned vacuum drying device based on the pressure measured by the aforementioned
`pressure measurement means, and if an abnormality is detected, outputs an indication of the abnormality.
`[Claim 7]
`A vacuum drying device described in any one of Claims 1 to 6, wherein the objects to be dried are battery electrodes.
`[Claim 8]
`A vacuum drying system comprising a vacuum drying device according to any one of Claims 1 to 7, and a dry room where
`the aforementioned object to be dried is placed after the completion of vacuum drying by the aforementioned vacuum drying
`device, wherein after the vacuum drying of the aforementioned object to be dried is determined to be complete by the
`aforementioned judgment means, the object to be dried is transferred from the aforementioned drying furnace to the
`aforementioned dry room.
`[Claim 9]
`A vacuum drying method for performing vacuum drying on an object to be dried arranged in a drying furnace, comprising:
`a first step of measuring the pressure inside the aforementioned drying furnace;
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`a second step of determining whether the pressure measured in the aforementioned first step has decreased to below or less
`than a predetermined target pressure;
`a third step of continuing vacuum drying for a predetermined first period of time after it is determined in the aforementioned
`second step that the pressure measured in the aforementioned first step is below or less than the aforementioned target pressure;
`a fourth step of measuring the pressure inside the aforementioned drying furnace after the aforementioned first period of
`time has elapsed;
`a fifth step of determining whether the pressure measured in the aforementioned fourth step has decreased to below or less
`than the aforementioned target pressure;
`a sixth step of determining that the vacuum drying of the aforementioned object to be dried is complete when the pressure
`measured in the aforementioned fourth step is determined in the aforementioned fifth step to be below or less than the
`aforementioned target pressure; and
`a seventh step of transferring the object to be dried, which is judged to have completed vacuum drying in the
`aforementioned sixth step, from the aforementioned drying furnace to an area adjusted to a predetermined environment.
`[Claim 10]
`The vacuum drying method described in Claim 9, further comprising an eighth step of measuring the time since the start
`of vacuum drying of the aforementioned object to be dried, wherein during the period until the time measured in the
`aforementioned eighth step exceeds a predetermined second period of time, the determination in the aforementioned second
`step is suspended.
`[Claim 11]
`The vacuum drying method described in Claim 9 or 10, wherein the aforementioned target pressure is set lower than the
`saturation vapor pressure at the dew point in the aforementioned predetermined environment.
`[Claim 12]
`The vacuum drying method described in Claim 11, wherein if the dew point (in degrees Celsius) in the aforementioned
`predetermined environment is denoted as t, and predetermined constants are denoted as a and b, the saturation vapor pressure
`e at the dew point in the aforementioned predetermined environment is determined using the following mathematical formula
`(2):
`[Mathematical formula 2]
`
`
`
`[Claim 13]
`A vacuum drying method described in Claim 11 or 12, wherein how much lower than the saturation vapor pressure at the
`dew point in the aforementioned predetermined environment the aforementioned target pressure is set is determined according
`to the material of the aforementioned object to be dried.
`[Claim 14]
`A vacuum drying method described in Claim 9 to 13, wherein in the second step, the abnormality detection of the vacuum
`drying device that is used to perform vacuum drying on the aforementioned object to be dried is performed based on the pressure
`measured in the aforementioned first step.
`[Claim 15]
`A vacuum drying method described in any one of Claims 9 to 14, wherein the object to be dried are battery electrodes.
`[Claim 16]
`A manufacturing method of battery electrodes for performing vacuum drying on battery electrodes arranged in a drying
`furnace, comprising:
`a first step of measuring the pressure inside the aforementioned drying furnace;
`a second step of determining whether the pressure measured in the aforementioned first step has decreased to below or less
`than a predetermined target pressure;
`a third step of continuing vacuum drying for a predetermined first period of time after it is determined in the aforementioned
`second step that the pressure measured in the aforementioned first step is below or less than the aforementioned target pressure;
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`a fourth step of measuring the pressure inside the aforementioned drying furnace after the aforementioned first period of
`time has elapsed;
`a fifth step of determining whether the pressure measured in the aforementioned fourth step has decreased to below or less
`than the aforementioned target pressure;
`a sixth step of determining that the vacuum drying of the aforementioned battery electrodes is complete when the pressure
`measured in the aforementioned fourth step is determined in the aforementioned fifth step to be below or less than the
`aforementioned target pressure; and
`a seventh step of transferring the battery electrodes, which are judged to have completed vacuum drying in the
`aforementioned sixth step, from the aforementioned drying furnace to an area adjusted to a predetermined environment.
`[Detailed Explanation of the Invention]
`[Technical Field]
`[0001]
`This invention relates to a vacuum drying device, a vacuum drying system, a vacuum drying method, and a manufacturing
`method for battery electrodes.
`[Background Technology]
`[0002]
`Conventional techniques have been proposed for performing vacuum drying on objects to be dried (for example, refer to
`Patent Document 1).
`[Existing Technology Document]
`[Patent Document]
`[0003]
`[Patent Document 1] Japanese Unexamined Patent Application Publication Official Gazette No. 2005-140536.
`[Overview of the Invention]
`[Problems to be Solved by the Invention]
`[0004]
`The methods described in Patent Document 1, as well as those shown in the literature referenced therein, aim to accurately
`determine the completion of vacuum drying, thereby suppressing occurrences of excessive drying and insufficient drying.
`Although this challenge of optimally completing vacuum drying has existed historically, various improvements continue to be
`made, and no satisfactory technology for determining the completion of vacuum drying has emerged so far. In particular, when
`drying electrodes for secondary batteries such as lithium-ion batteries, if the electrodes are not sufficiently dried, there is a risk
`that the batteries produced using those electrodes will fail to demonstrate the desired performance.
`[0005]
`Therefore, this invention has been developed in light of the aforementioned issues, with the aim of completing vacuum
`drying under optimal conditions.
`[Means for Solving the Problems]
`[0006]
`This invention proposes the following measures to solve the aforementioned problems. Moreover, to facilitate
`understanding, reference numerals corresponding to embodiments of this invention are provided, but the invention is not limited
`to these embodiments.
`[0007]
`(1) This invention is a vacuum drying device (for example, corresponding to the vacuum drying device 1 in Fig. 1) for
`performing vacuum drying on an object to be dried (for example, corresponding to the battery electrodes mentioned later)
`arranged in a drying furnace (for example, corresponding to the drying furnace 11 in Fig. 1). It comprises: a pressure
`measurement means (for example, corresponding to the pressure measurement section 12 in Fig. 1) for measuring the pressure
`inside the aforementioned drying furnace; a determination means (for example, corresponding to the determination section 13
`in Fig. 1) for determining whether the pressure measured by the aforementioned pressure measurement means has decreased
`to below or less than a predetermined target pressure; a vacuum drying control means (for example, corresponding to the
`vacuum drying control section 14 in Fig. 1) for continuing vacuum drying for a predetermined first period after it is determined
`by the aforementioned determination means that the pressure measured by the aforementioned pressure measurement means is
`below or less than the aforementioned target pressure; and a judgment means (for example, corresponding to the judgment
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`section 15 in Fig. 1) for determining that the vacuum drying of the aforementioned object to be dried is complete when the
`pressure measured by the aforementioned pressure measurement means after the aforementioned first period is determined by
`the aforementioned determination means to be below or less than the aforementioned target pressure.
`[0008]
`According to this invention, the pressure measurement means is used to measure the pressure inside the drying furnace. In
`addition, the determination means is employed to ascertain whether the pressure measured by the pressure measurement means
`has fallen below or is less than the target pressure. Moreover, the vacuum drying control means continues vacuum drying over
`the first period of time once the pressure measurement means indicates that the pressure has dropped below or is less than the
`target pressure as determined by the determination means. For this reason, even after it is determined that the pressure inside
`the drying furnace has fallen below or is less than the target pressure, the vacuum drying will still continue over the first period
`of time, allowing for a suppression of drying insufficiencies without being greatly affected by the accuracy of the target pressure
`setting.
`[0009]
`In addition, according to this invention, by setting the first period of time, it is possible to prevent the duration of vacuum
`drying from becoming excessively prolonged, thereby suppressing the occurrence of excessive drying.
`[0010]
`In addition, according to this invention, if, after the first period of time has elapsed, the pressure measured by the pressure
`measurement means is determined by the determination means to have decreased below or less than the target pressure, it is
`concluded that the vacuum drying of the object to be dried is complete. As a result, even during the period when vacuum drying
`continues over the first period of time, if an unforeseen circumstance leads to the object being inadequately dried, it can be
`determined that the vacuum drying is not yet complete, thus preventing a misjudgment that the vacuum drying has been
`completed despite insufficient drying.
`[0011]
`(2) This invention proposes a vacuum drying device concerning (1), which includes time-counting means (for example,
`corresponding to the time-counting section 16 in Fig. 3) for measuring the time since the commencement of vacuum drying of
`the aforementioned object to be dried. During the period until the time measured by the aforementioned time-counting means
`exceeds a predetermined second period of time, the determination made by the aforementioned determination means is
`suspended.
`[0012]
`According to this invention, in the vacuum drying device of (1), the time-counting means measures the time since the start
`of vacuum drying of the object to be dried, and during the period until the time measured by the time-counting means exceeds
`the second period of time, the determination made by the determination means is suspended. Therefore, by setting the second
`period of time, it is possible to suspend the determination made by the determination means during a period when it is certain
`that the vacuum drying of the object to be dried is not yet complete.
`[0013]
`(3) This invention proposes a vacuum drying device concerning (1) or (2), wherein the environment where the
`aforementioned object to be dried will be placed after the completion of vacuum drying is referred to as a predetermined
`environment (for example, corresponding to the dry room 2 in Fig. 1). In this case, the pressure set as the aforementioned target
`pressure is lower than the saturation vapor pressure at the dew point in the aforementioned predetermined environment.
`[0014]
`According to this invention, in the vacuum drying device of (1) or (2), where the object to be dried will be placed in a
`predetermined environment after the completion of vacuum drying, the target pressure is set to be lower than the saturation
`vapor pressure at the dew point in the predetermined environment. Consequently, the accuracy of the target pressure as a
`criterion for determining the completion of vacuum drying can be improved, allowing for a more reliable suppression of
`inadequate drying and enabling a reduction in the first period of time during which vacuum drying is continued.
`[0015]
`In addition, it is conceivable to find the optimal value of the target pressure by repeating the procedures for appropriately
`setting the target pressure and measuring the moisture content contained in the object to be dried or evaluating its performance
`after the completion of vacuum drying. Therefore, according to this invention, in the vacuum drying device of (1) or (2), the
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`target pressure is set to be lower than the saturation vapor pressure at the dew point in the predetermined environment. Thus,
`when finding the optimal value of the target pressure, the initial value of the target pressure can be set using the saturation
`vapor pressure at the dew point in the predetermined environment as a reference. Accordingly, it becomes possible to set a
`more appropriate initial value for the target pressure compared to the situation where there is no reference, thus reducing the
`number of times these two procedures need to be repeated and enabling the optimal value of the target pressure to be determined
`in a shorter time.
`[0016]
`(4) This invention proposes a vacuum drying device concerning (3), wherein the dew point (in degrees Celsius) in the
`aforementioned predetermined environment is denoted as t, and the predefined constants are denoted as a and b. The saturation
`vapor pressure e at the dew point in the aforementioned predetermined environment is determined using the following
`mathematical formula (1).
`[0017]
`[Mathematical formula 1]
`
`
`
`[0018]
`According to this invention, in the vacuum drying device of (3), the saturation vapor pressure at the dew point in the
`predetermined environment can be determined using the aforementioned mathematical formula (1), known as the Tetens
`formula, without employing a complex method.
`[0019]
`(5) This invention proposes a vacuum drying device concerning (3) or (4), which determines how much lower than the
`aforementioned saturation vapor pressure at the dew point in the aforesaid predetermined environment the aforementioned
`target pressure should be set, depending on the material of the object to be dried.
`[0020]
`After the completion of vacuum drying, the object to be dried will absorb moisture during the period it is placed in the
`predetermined environment, depending on the material of the object to be dried. Therefore, according to this invention, in the
`vacuum drying device of (3) or (4), the decision of how much lower than the saturation vapor pressure at the dew point in the
`predetermined environment the target pressure should be set is made according to the material of the object to be dried. This
`allows for the setting of the target pressure based on the hygroscopicity of the object to be dried in the predetermined
`environment.
`[0021]
`(6) This invention proposes a vacuum drying device concerning any one of (1) to (5), wherein the aforementioned
`determination means detects abnormalities in the vacuum drying device based on the pressure measured by the aforementioned
`pressure measurement means and outputs an indication of the abnormality when such an abnormality is determined.
`[0022]
`According to this invention, in any one of the vacuum drying devices from (1) to (5), the determination means performs
`abnormality detection of the vacuum drying device based on the pressure measured by the pressure measurement means, and
`if an abnormality is judged to exist, it issues an output indicating the abnormality. As a result, it becomes possible to detect and
`output abnormalities in the vacuum drying device while determining the completion of vacuum drying.
`[0023]
`(7) This invention proposes a vacuum drying device regarding any one of (1) to (6), wherein the objects to be dried are
`battery electrodes.
`[0024]
`According to this invention, in any one of the vacuum drying devices from (1) to (6), the object to be dried is specified as
`a battery electrode. This helps to suppress the occurrence of insufficient drying of the battery electrodes.
`[0025]
`(8) This invention proposes a vacuum drying system that includes any one of the vacuum drying devices from (1) to (7)
`and a dry room where the aforementioned object to be dried is placed after the completion of vacuum drying (for example,
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`corresponding to the dry room 2 in Fig. 1), wherein the object to be dried will be transferred from the aforementioned drying
`furnace to the aforementioned dry room after it has been judged as having completed vacuum drying by the aforementioned
`judgment means.
`[0026]
`According to this invention, in a vacuum drying system comprising any one of the vacuum drying devices from (1) to (7)
`and the dry room where the object to be dried is placed after the completion of vacuum drying, the object to be dried will be
`transferred from the drying furnace to the dry room after the judgment means has determined that the vacuum drying of the
`object to be dried has been completed. This allows for the vacuum drying device to perform vacuum drying on a new object to
`be dried after transferring the object to be dried from the drying furnace to the dry room.
`[0027]
`(9) This invention relates to a vacuum drying method that performs vacuum drying on an object to be dried (for example,
`corresponding to the battery electrodes described later) placed in a drying furnace (for example, corresponding to the drying
`furnace 11 in Fig. 1). The method includes a first step of measuring the pressure inside the aforementioned drying furnace; a
`second step of determining whether the pressure measured in the aforementioned first step has decreased to below or less than
`a predetermined target pressure; a third step of continuing vacuum drying for a predetermined first period of time after it is
`determined in the aforementioned second step that the pressure measured in the aforementioned first step is below or less than
`the aforementioned target pressure; a fourth step of measuring the pressure inside the aforementioned drying furnace after the
`aforementioned first period of time has elapsed; a fifth step of determining whether the pressure measured in the aforementioned
`fourth step has decreased to below or less than the aforementioned target pressure; a sixth step of determining that the vacuum
`drying of the aforementioned object to be dried is complete when the pressure measured in the aforementioned fourth step is
`determined in the aforementioned fifth step to be below or less than the aforementioned target pressure; and a seventh step of
`transferring the object to be dried, which is judged to have completed vacuum drying in the aforementioned sixth step, from
`the aforementioned drying furnace to an area adjusted to a predetermined environment (for example, corresponding to the dry
`room 2 in Fig. 1).
`[0028]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0029]
`(10) This invention proposes a vacuum drying method concerning the vacuum drying method of (9), which further includes
`an eighth step of measuring the time since the start of vacuum drying of the object to be dried, and during the period until the
`time measured in the eighth step exceeds a predetermined second period of time, it is characterized by suspending the
`determination made in the second step.
`[0030]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0031]
`(11) This invention proposes a vacuum drying method regarding the vacuum drying methods of (9) or (10), wherein the
`aforementioned target pressure is set to a pressure lower than the saturation vapor pressure at the dew point in the
`aforementioned predetermined environment.
`[0032]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0033]
`(12) This invention proposes a vacuum drying method regarding the vacuum drying method of (11), wherein when the
`dew point (in degrees Celsius) in the aforementioned predetermined environment is denoted as t, and predetermined constants
`are represented as a and b, the saturation vapor pressure e at the dew point in the aforementioned predetermined environment
`is determined using the following mathematical formula (2).
`[0034]
`
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`[Mathematical formula 2]
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`[0035]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0036]
`(13) This invention proposes a vacuum drying method concerning the vacuum drying methods of (11) or (12), wherein
`how much lower the target pressure is set from the saturation vapor pressure at the dew point in the aforementioned
`predetermined environment is determined depending on the material of the object to be dried.
`[0037]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0038]
`(14) This invention proposes a vacuum drying method regarding any one of the vacuum drying methods from (9) to (13),
`which includes performing abnormality detection of the vacuum drying device that dries the object to be dried based on the
`pressure measured in the first step during the second step.
`[0039]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0040]
`(15) This invention proposes a vacuum drying method concerning any one of the vacuum drying methods from (9) to (14),
`wherein the objects to be dried are battery electrodes.
`[0041]
`According to this invention, similar effects as those mentioned above can be achieved.
`[0042]
`(16) This invention is a manufacturing method of battery electrodes that performs vacuum drying on battery electrodes
`placed in a drying furnace (for example, corresponding to the drying furnace 11 in Fig. 1). The method includes a first step of
`measuring the pressure inside the aforementioned drying furnace; a second step of determining whether the pressure measured
`in the aforementioned first step has decreased to below or less than a predetermined target pressure; a third step of continuing
`vacuum drying for a predetermined first period of time after it is determined in the aforementioned second step that the pressure
`measured in the aforementioned first step is below or less than the aforementioned target pressure; a fourth step of measuring
`the pressure inside the aforementioned drying furnace after the aforementioned first period of time has elapsed; a fifth step of
`determining whether the pressure measured in the aforementioned fourth step has decreased to below or less than the
`aforementioned target pressure; a sixth step of determining that the vacuum drying of the aforementioned battery electrodes is
`complete when the pressure measured in the aforementioned fourth step is determined in the aforementioned fifth step to be
`below or less than the aforementioned target pressure; and a seventh step of transferring the battery electrodes, which is judged
`to have completed vacuum drying in the aforementioned sixth step, from the aforementioned drying furnace to an area adjusted
`to a predetermined environment (for example, corresponding to the dry room 2 in Fig. 1).
`[0043]
`According to this invention, similar effects as those mentioned above can be achieved when manufacturing battery
`electrodes.
`[Effects of the Invention]
`[0044]
`According to this invention, vacuum drying can be completed under optimal conditions.
`[Brief Description of Drawings]
`[0045]
`[Fig. 1] It is a block diagram of the vacuum drying device according to the first embodiment of this invention.
`[Fig. 2] It is a diagram showing the state of water changing according to temperature and pressure.
`[Fig. 3] It is a block diagram of the vacuum drying device according to the second embodiment of this invention.
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`[Embodiments of the Invention]
`[0046]
`Below, the embodiments of this invention will be described in detail using the Drawings. Please note that the components
`in the following embodiments can be appropriately replaced with existing components and various combinations with other
`existing components are possible. Therefore, the description of the following embodiments does not limit the scope of the
`invention as stated in the Scope of Patent Claims.
`[0047]
`<First Embodiment>
`Fig. 1 is a block diagram of the vacuum drying system AA according to the first embodiment of this invention. The vacuum
`drying system AA includes a vacuum drying device 1 that performs vacuum drying on battery electrodes, and a dry room 2
`where the battery electrodes are placed after the completion of vacuum drying by the vacuum drying device 1.
`[0048]
`The vacuum drying device 1 comprises a drying furnace 11, a pressure measurement section 12, a determination section
`13, a vacuum drying control section 14, and a judgment section 15. It performs vacuum drying on the battery electrodes placed
`inside the drying furnace 11 to remove moisture contained in the battery electrodes.
`[0049]
`The pressure measurement section 12 measures the pressure inside the drying furnace 11.
`[0050]
`The determination section 13 determines whether the pressure measured by the pressure measurement section 12 has fallen
`below a predetermined target pressure. The setting of the aforementioned target pressure will be detailed below using Fig. 2.
`[0051]
`As shown in Fig. 2, the state of water changes according to temperature and pressure. Therefore, first, the dew point (in
`degrees Celsius) in the dry room 2, where the battery electrodes are placed after vacuum drying is completed, is substituted for
`t in the following mathematical formula (3) to obtain the saturation vapor pressure e at the dew point in the dry room 2.
`Moreover, in the mathematical formula (3), a and b are predetermined constants, which are uniquely determined for the case
`when the moisture in the battery electrodes is water and the case when it is ice.
`[0052]
`[Mathematical formula 3]
`
`
`
`[0053]
`Moreover, in the dry room 2, to prevent moisture from adhering to the transported battery electrodes, a threshold based on
`the dew point of the dry room 2 is set, and environmental adjustments are made through air conditioning to maintain the desired
`dew point. According to the af