Ceramic body, method for producing the same, heater element, heater unit, heater system, and purification system

Abstract

To provide a ceramic body having a PTC property of low electric resistance at a room temperature.SOLUTION: A ceramic body comprises a BaTiO3-based crystal grain having a part of Ba replaced by a rare earth element as a main component, and includes 1.0-10.0 mass% of a Ba6Ti17O40 crystal grain.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a ceramic body, a method for manufacturing the same, a heater element, a heater unit, a heater system, and a purification system.

Background Art

[0002] Conventionally, as a material exhibiting PTC (Positive Temperature Coefficient) characteristics, a ceramic body obtained by adding various additive elements to a composition represented by BaTiO3 has been proposed. The PTC characteristic is a characteristic in which the resistance value rapidly increases at a high temperature above the Curie point. Ceramic bodies having PTC characteristics are used in PTC heaters, PTC switches, overcurrent protection elements, temperature detectors, etc., and various characteristic improvements have been made according to the applications.

[0003] Patent Document 1 describes that by using Y, Ho, Er, Yb in BaTiO3 and adding an appropriate amount of La, Dy, Eu, Gd in combination with Y, Ho, Er, Yb, a porcelain composition for a PTC thermistor with small change over time and both room temperature resistivity and temperature coefficient of resistance being practical values can be obtained.

[0004] Patent Document 2 discloses a perovskite-type structure represented by the general formula A m , m BO3, with a Ba m TiO3-based composition as the main component. Among 100 mol% of Ti, W as a semiconductor agent is substituted in the range of 0.05 mol% or more and 0.3 mol% or less. The ratio m of the A site mainly occupied by Ba and the B site mainly occupied by Ti is 0.99 ≦ m ≦ 1.002. When the total number of moles of the elements constituting the A site is 100 mol%, Ca is contained in the range of 15 mol% or less. When the temperature at which the resistance value becomes twice the resistance value at 25°C is defined as the doubling point, the doubling point is 100°C or higher, and the actually measured sintered density is 70% or more and 90% or less of the theoretical sintered density. The semiconductor ceramic is described as having stable PTC characteristics, a high doubling point, and a wide operating temperature range.

[0005] Patent Document 3 states that in a barium titanate-based PTC thermistor, part of Ba is replaced not with Pb, which has a high environmental impact, but with Bi and an alkali metal A (Na or K) within a predetermined range, and the molar ratio of the Ba site / Ti site and the addition amount of Ca are within a predetermined range, so that semiconductor conversion can be easily achieved in firing either in the air or in a nitrogen atmosphere, the room temperature specific resistance is low, and a PTC thermistor with a Curie point shifted to the higher temperature side than 120°C can be obtained. Further, this document states that this PTC thermistor can also reduce the change over time even when used as a heater element.

[0006] Patent Document 4 states that instead of cubic barium titanate powder, highly crystalline tetragonal barium titanate powder is used as a raw material, and at 123 Kelvin to 163 Kelvin, the slope of the change in intragranular resistance with respect to the reciprocal of the Kelvin temperature is controlled to be 135 or more and 340 or less, and by setting the average porcelain particle size after sintering to 0.8 μm or less, the room temperature specific resistance of the multilayer PTC thermistor can be lowered and the withstand voltage property can be increased.

[0007] Patent Document 5 describes a multilayer PTC thermistor element using a ceramic substrate composed mainly of barium titanate with rare earth elements added, where the average porcelain particle size of the ceramic substrate is 0.3 [μm] or more and less than 0.5 [μm], the lower limit value of the relative density of the ceramic substrate is 70 [%], and the upper limit value of the relative density of the ceramic substrate is -6.43d + 97.83 [%] when the average porcelain particle size is d. This multilayer PTC thermistor element is said to be able to achieve both a low room temperature specific resistance and a high withstand voltage.

[0008] Patent Document 6 has the general formula A mA BaTiO₃-based composition having a perovskite structure represented by BO₃ as the main component, wherein part of the Ba constituting the A site is substituted with an alkali metal element, Bi, Ca, Sr, and a rare earth element, and when the total number of moles of the elements constituting the A site is 1 mole, the contents of Ca and Sr, where the molar ratio of Ca is x and the molar ratio of Sr is y, satisfy 0.05 ≦ x ≦ 0.20, 0.02 ≦ y ≦ 0.12, and 2x + 5y ≦ 0.7, and a substantially lead-free non-lead semiconductor ceramic is described. The semiconductor ceramic does not discolor on the surface even when energized for a long time, and while ensuring a desired Curie point, the change in the resistance value is suppressed, so it is said to be excellent in reliability.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, although improvements have been made to the ceramic body having PTC characteristics from various viewpoints, there is still room for development. For example, applying a honeycomb-shaped ceramic body to a heater element for heating has been considered. When this heater element is to function at a low voltage, it is required to lower the electrical resistance at room temperature. Further, in a heater element, generally a pair of electrodes are provided on the end face of the honeycomb-shaped ceramic body (the face perpendicular to the direction in which the cells extend). However, since a pair of electrodes face the gas flow path, there is a risk of corrosion of the pair of electrodes. Therefore, providing a pair of electrodes on the side face of the honeycomb-shaped ceramic body (the face parallel to the direction in which the cells extend) has been considered. However, when providing a pair of electrodes on the side face of the ceramic body, the distance between the electrodes becomes larger compared to the case of providing a pair of electrodes on the end face of the ceramic body. Therefore, it is required to lower the electrical resistance of the ceramic body at room temperature. In particular, such a requirement is significant in the case of a honeycomb-shaped ceramic body with a small thickness of the partition walls.

[0011] The present invention has been created in view of the above circumstances, and an object thereof is to provide a ceramic body having PTC characteristics with a low electrical resistance at room temperature and a method for manufacturing the same. Further, an object of the present invention is to provide a heater element, a heater unit, a heater system, and a purification system including such a ceramic body.

Means for Solving the Problems

[0012] As a result of intensive research on a ceramic body mainly composed of BaTiO3-based crystal particles, the present inventors have found that the presence of Ba6Ti 17 O 40 crystal particles is closely related to the electrical resistance at room temperature, and have completed the present invention.

[0013] That is, the present invention mainly comprises BaTiO3-based crystal particles in which a part of Ba is La substituted, and contains 1.0 to 10.0 mass% of Ba6Ti 17 O 40 crystal particles and wherein the composition formula of the BaTiO 3-based crystalline particles is (Ba 1-x A x )TiO 3 (wherein A represents La and 0.001 ≦ x ≦ 0.010), the BaTiO 3 -based crystalline particles have a (Ba + La) / Ti ratio of 1.005 to 1.050, It is a ceramic body.

[0014] Moreover, the present invention a method for producing the ceramic body, BaCO3 powder, TiO2 powder, and La a ceramic raw material containing a powder of nitrate and / or hydroxide of is molded to produce a ceramic molded body having a relative density of 60% or more, and a molding step; After holding the ceramic molded body at 1150 to 1250 °C, it is heated to a maximum temperature of 1360 to 1430 °C at a heating rate of 20 to 500 °C / hour and held for 0.5 to 5 hours, including a firing step. and is a method.

[0015] Moreover, the present invention is a heater element including the ceramic body.

[0016] Moreover, the present invention is a heater unit including two or more of the heater elements.

[0017] Moreover, the present invention an inflow pipe that connects an outside air introduction part or a vehicle compartment and an inlet of the heater unit, a battery for applying a voltage to the heater unit, and an outflow pipe that connects an outlet of the heater unit and the vehicle compartment is a heater system including.

[0018] Furthermore, the present invention has a heater element having the ceramic body, an adsorbent provided on a surface of the partition wall of the ceramic body, and a pair of electrodes provided on the first end face and the second end face of the ceramic body, or a heater unit including two or more of the heater elements, A battery for applying a voltage to the pair of electrodes of the heater element An inflow pipe that communicates the passenger compartment with the inlet of the heater element or the heater unit An outflow pipe that communicates the outlet of the heater element or the heater unit with the passenger compartment and the outside of the vehicle, and A switching valve provided in the outflow pipe and capable of switching the flow of air flowing through the outflow pipe to the passenger compartment or the outside of the vehicle A purification system comprising the same

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a ceramic body having a PTC characteristic with a low electrical resistance at room temperature and a method for manufacturing the same. Further, according to the present invention, it is possible to provide a heater element, a heater unit, a heater system, and a purification system including such a ceramic body

Brief Description of the Drawings

[0020]

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Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements can be appropriately made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention, and such modified and improved embodiments also fall within the scope of the present invention.

[0022] <Ceramic body> (1-1) Crystal structure and composition The ceramic body according to an embodiment of the present invention mainly consists of BaTiO3-based crystal particles in which a part of Ba is substituted with a rare earth element. By using BaTiO3-based crystal particles as the main component, a ceramic body capable of generating heat by energization and having PTC characteristics can be obtained. Further, by substituting a part of Ba in the BaTiO3-based crystal particles with a rare earth element, the electrical resistance at room temperature (25°C) can be reduced. Here, in this specification, "main component" means that the proportion in all components is 50% by mass or more.

[0023] The composition formula of BaTiO3-based crystal particles in which a part of Ba is substituted with a rare earth element is (Ba 1-x A x)It can be represented by TiO3. In the composition formula, A represents one or more rare earth elements, and 0.001 ≤ x ≤ 0.010. A is not particularly limited as long as it is a rare earth element, but is preferably one or more selected from the group consisting of La, Ce, Pr, Nd, Eu, Gd, Dy, Ho, Er, and Yb, and more preferably La. From the viewpoint of suppressing the excessive increase in electrical resistance at room temperature, x is preferably 0.001 or more, more preferably 0.0015 or more, and still more preferably 0.002 or more. On the other hand, from the viewpoint of suppressing insufficient sintering and excessive increase in electrical resistance at room temperature, x is preferably 0.010 or less, more preferably 0.009 or less, and still more preferably 0.008 or less.

[0024] For BaTiO3-based crystal particles in which a part of Ba is substituted with a rare earth element, the (Ba + rare earth element) / Ti ratio is preferably 1.005 to 1.050. By controlling the (Ba + rare earth element) / Ti ratio within such a range, the electrical resistance at room temperature can be stably reduced. The elemental ratios of Ba, rare earth element, and Ti can be determined by, for example, fluorescent X-ray analysis, ICP-MS (inductively coupled plasma mass spectrometry), etc.

[0025] The BaTiO3-based crystal particles in which a part of Ba is substituted with a rare earth element preferably have a lattice volume of 64.0000 to 64.3750 Å 3 more preferably 64.4000 to 64.3650 Å 3 By controlling the lattice volume within such a range, the electrical resistance at room temperature can be stably reduced. The lattice volume of this BaTiO3-based crystal particle can be measured using an X-ray diffractometer. Specifically, the X-ray diffraction data can be analyzed by the Rietveld method, and the lattice volume can be measured from the obtained lattice constant.

[0026] In the BaTiO3-based crystalline particles in which part of Ba is substituted with rare earth elements, the average crystal grain size is preferably 5 to 200 μm, more preferably 5 to 180 μm, and still more preferably 5 to 160 μm. By controlling the average crystal grain size within such a range, the electrical resistance at room temperature can be stably reduced. The average crystal grain size of the BaTiO3-based crystalline particles can be measured as follows. A 5 mm × 5 mm × 5 mm cubic sample is cut out from the ceramic body and embedded in resin. The embedded sample is mirror-polished by mechanical polishing and observed by SEM. The SEM observation is performed, for example, using a model S-3400N manufactured by Hitachi High-Technologies Corporation, at an acceleration voltage of 15 kV and a magnification of 3000. In the SEM observation image (vertical 30 μm × horizontal 45 μm), four straight lines with a thickness of 0.3 μm spanning the entire vertical direction of the field of view are drawn at intervals of 10 μm, and the number of BaTiO3-based crystalline particles through which this straight line passes even partially is counted. The average of the results obtained by dividing the length of the straight line by the number of BaTiO3-based crystalline particles in four or more SEM observation images is taken as the average crystal grain size.

[0027] In the ceramic body of the BaTiO3-based crystalline particles in which part of Ba is substituted with rare earth elements, the content is not particularly limited as long as it is the main component amount, but it is preferably 90.0% by mass or more, more preferably 92.0% by mass or more, and still more preferably 94.0% by mass or more. The upper limit value of the content of the BaTiO3-based crystalline particles is not particularly limited, but is generally 99.0% by mass, preferably 98.0% by mass. The content of the BaTiO3-based crystalline particles can be measured, for example, by fluorescent X-ray analysis or EDAX (energy dispersive X-ray) analysis. Other crystalline particles can also be measured in the same manner as this method.

[0028] The ceramic body according to the embodiment of the present invention contains Ba6Ti 17 O 40 crystalline particles. In the ceramic body, Ba6Ti 17 O 40By introducing crystalline particles, the electrical resistance at room temperature can be reduced. Although the present invention is not intended to be limited by theory, Ba6Ti 17 O 40 The crystalline particles are considered to liquefy during the firing process, promoting the rearrangement, grain growth, and densification of BaTiO3-based crystalline particles, thereby reducing the electrical resistance at room temperature.

[0029] Ba6Ti 17 O 40 The content of the Ba6Ti 17 O 40 crystalline particles in the ceramic body is 1.0 to 10.0% by mass, preferably 1.2 to 8.0% by mass, more preferably 1.5 to 6.0% by mass. By setting the Ba6Ti 17 O 40 crystalline particles to 1.0% by mass or more, the effect of the Ba6Ti 17 O 40 crystalline particles (i.e., the effect of reducing the electrical resistance at room temperature) can be obtained. Also, by setting the Ba6Ti

[0030] crystalline particles to 10.0% by mass or less, the PTC characteristics can be ensured. The ceramic body according to an embodiment of the present invention may further contain BaCO3 crystalline particles. The BaCO3 crystalline particles are crystalline particles derived from the BaCO3 powder, which is a raw material of the ceramic body.

[0031] In addition to the above crystal particles, the ceramic body according to an embodiment of the present invention may further contain components that are conventionally added to PTC materials. Such components include additives such as shifters, property improvers, metal oxides, and conductor powders, as well as inevitable impurities.

[0032] From the viewpoint of reducing environmental impact, it is desirable that the ceramic body according to an embodiment of the present invention substantially does not contain lead (Pb). Specifically, in the ceramic body according to an embodiment of the present invention, the Pb content is preferably 0.01% by mass or less, more preferably 0.001% by mass or less, and still more preferably 0% by mass. When the Pb content is low, for example, when the ceramic body is used as a heater element, the heated air brought into contact with the ceramic body can be safely applied to organisms such as humans. In the ceramic body according to an embodiment of the present invention, the Pb content, in terms of PbO, is preferably less than 0.03% by mass, more preferably less than 0.01% by mass, and still more preferably 0% by mass. The lead content can be determined by, for example, fluorescent X-ray analysis, ICP-MS (inductively coupled plasma mass spectrometry), or the like.

[0033] It is preferable that the ceramic body according to an embodiment of the present invention substantially does not contain alkali metals that may affect the electrical resistance at room temperature. Specifically, in the ceramic body according to an embodiment of the present invention, the content of alkali metals is preferably 0.01% by mass or less, more preferably 0.001% by mass or less, and still more preferably 0% by mass. By controlling the content of alkali metals within such a range, the electrical resistance at room temperature can be stably reduced. The content of alkali metals can be determined by, for example, fluorescent X-ray analysis, ICP-MS (inductively coupled plasma mass spectrometry), or the like.

[0034] (1-2) Open porosity The open porosity of the ceramic body according to the embodiment of the present invention is a factor that affects the electrical resistance at room temperature. Therefore, the open porosity of the ceramic body according to the embodiment of the present invention is preferably controlled to 5.0% or less, more preferably 4.9% or less. By controlling the open porosity within such a range, the ceramic body can be densified, so that the electrical resistance at room temperature can be stably reduced. The lower limit value of the open porosity is not particularly limited, but is generally 0.1%, preferably 0.5%. The open porosity of the ceramic body can be measured by the Archimedes method using pure water as a medium. The open porosity can be controlled by adjusting conditions such as the amount of pore-forming material and sintering aid used when manufacturing the ceramic body, and the firing atmosphere.

[0035] (1-3) Bulk density The bulk density of the ceramic body according to the embodiment of the present invention is a factor that affects the electrical resistance at room temperature. Therefore, the bulk density of the ceramic body according to the embodiment of the present invention is preferably controlled to 5.35 g / cm 3 or more. By controlling the bulk density within such a range, the electrical resistance at room temperature can be stably reduced. The upper limit value of the bulk density is not particularly limited, but is generally 7.00 g / cm 3 , preferably 6.00 g / cm 3 . The bulk density of the ceramic body can be measured by the Archimedes method using pure water as a medium, similar to the open porosity. The bulk density can be controlled by adjusting conditions such as the amount of dispersion medium, binder, plasticizer, dispersant, etc. used when manufacturing the ceramic body, and the firing atmosphere.

[0036] (1-4) Volume resistivity The volume resistivity of the ceramic body according to the embodiment of the present invention is preferably 150 Ω·cm or less, more preferably 100 Ω·cm or less, still more preferably 50 Ω·cm, and particularly preferably 30 Ω·cm or less when measured at 25°C. If the volume resistivity is within such a range, it can be said that the electrical resistance at room temperature is low. By reducing the electrical resistance at room temperature, it is possible to ensure the heat generation performance required for heating and suppress the increase in power consumption. Note that the lower limit value of the volume resistivity is not particularly limited, but is generally 0.1 Ω·cm, preferably 1.0 Ω·cm. The volume resistivity of the ceramic body can be measured as follows. Two or more test pieces having dimensions of 30 mm × 30 mm × 15 mm are randomly cut and collected from the ceramic body. Then, the electrical resistance at the measurement temperature is measured by the two-terminal method, and the volume resistivity is calculated from the shape of the test piece. The average value of the volume resistivity of all the test pieces is taken as the measured value at the measurement temperature.

[0037] (1-5) Applications The ceramic body according to the embodiment of the present invention is not particularly limited, but can be used, for example, in a PTC heater, a PTC switch, an overcurrent protection element, and a temperature detector. Among these, the ceramic body according to the embodiment of the present invention can be preferably used as a heater element for heating, particularly as a heater element for heating the passenger compartment of a vehicle. The vehicle is not particularly limited, but examples include an automobile and a train. The automobile is not particularly limited, but examples include a gasoline vehicle, a diesel vehicle, a fuel cell vehicle, an electric vehicle, and a plug-in hybrid vehicle. The heater element according to the embodiment of the present invention can be preferably used particularly in vehicles without an internal combustion engine such as electric vehicles and trains.

[0038] (1-6) Shape The shape of the ceramic body according to the embodiment of the present invention may be appropriately selected according to the application and is not particularly limited. For example, when considering using the ceramic body as a heater element, it can have a wall flow type or a flow-through type honeycomb shape, but a flow-through type honeycomb shape is preferred.

[0039] Here, FIG. 1 shows a schematic perspective view of a ceramic body (hereinafter referred to as a "honeycomb structure") according to an embodiment of the present invention having a flow-through type honeycomb shape. The honeycomb structure 10 according to the embodiment of the present invention has a honeycomb shape including an outer peripheral wall 11 and a partition wall 12 disposed inside the outer peripheral wall 11 and partitioning a plurality of cells 14 that form a flow path from the first end face 13a to the second end face 13b.

[0040] The shape of each end face (the first end face 13a and the second end face 13b) of the honeycomb structure 10 is not particularly limited, but can be any shape such as a polygon (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), a circle, an oval shape, an L shape, etc. When each end face is a polygon, the corners may be chamfered. It is preferable that the shape of each end face is the same as the shape of the cross section orthogonal to the direction in which the cell 14 extends.

[0041] There is no limitation on the shape of the cell 14 in the cross section orthogonal to the direction in which the cell 14 extends, but it is preferably a quadrilateral (rectangle, square), a hexagon, an octagon, or a combination of two or more of these. Among these, the shape of the cell 14 is preferably a square and / or a hexagon. By making the cell 14 have such a shape, the pressure loss when gas is passed through the honeycomb structure 10 can be reduced. In the honeycomb structure 10 of FIG. 1, the case where the shape of the cell 14 in the cross section orthogonal to the direction in which the cell 14 extends is a square is shown.

[0042] The average thickness of the partition walls 12 is not particularly limited, but is preferably 50 to 130 μm, more preferably 55 to 120 μm, and still more preferably 60 to 110 μm. By setting the average thickness of the partition walls 12 to 50 μm or more, it is possible to ensure the strength of the honeycomb structure 10 while reducing the electrical resistance at room temperature. Further, by setting the average thickness of the partition walls 12 to 130 μm or less, a compact honeycomb structure 10 can be obtained. Here, the thickness of the partition wall 12 refers to the length of the line segment connecting the centers of gravity of adjacent cells 14 when the cross section orthogonal to the direction in which the cells 14 extend intersects the partition wall 12. The average thickness of the partition walls 12 refers to the average value of the thicknesses of all the partition walls 12.

[0043] The cell density is not particularly limited, but is preferably 15 to 140 cells / cm 2 , more preferably 46 to 94 cells / cm 2 . By setting the cell density to 15 cells / cm 2 or more, it is possible to obtain a honeycomb structure 10 suitable for heating while reducing the electrical resistance at room temperature. Further, by setting the cell density to 140 cells / cm 2 or less, it is possible to suppress the ventilation resistance and the output of the blower. Here, the cell density can be obtained by dividing the number of cells by the area of each bottom surface of the honeycomb structure 10.

[0044] The honeycomb structure 10 shown in FIG. 1 can be used as a heater element and can generate heat when energized. Therefore, a gas such as outside air or air in the vehicle interior can be heated by heat transfer from the partition walls 12 that generate heat as the gas flows in from the first end face 13a, passes through the plurality of cells 14, and flows out from the second end face 13b.

[0045] The ceramic body according to an embodiment of the present invention may be a honeycomb joined body having a honeycomb segment and a joining layer that joins between a plurality of honeycomb segments. By using the honeycomb joined body, it is possible to increase the total cross-sectional area of the cells 14, which is important for ensuring the gas flow rate while suppressing the generation of cracks.

[0046] Here, as an example, FIG. 2 shows a schematic cross-sectional view orthogonal to the direction in which the cells of the honeycomb joined body having five honeycomb segments extend. As shown in FIG. 2, the honeycomb joined body 17 has five honeycomb segments 18 and a joining layer 19 that joins between the honeycomb segments 18. Each honeycomb segment 18 has an outer peripheral wall 11 and a partition wall 12 that is disposed inside the outer peripheral wall 11 and partitions and forms a plurality of cells 14 that form a flow path from the first end face 13a to the second end face 13b.

[0047] The joining layer 19 can be formed using a joining material. The joining material is not particularly limited, but a material obtained by adding a solvent such as water to a ceramic material to make it into a paste form can be used. The joining material may contain a ceramic having PTC characteristics, or may contain the same ceramic as the outer peripheral wall 11 and the partition wall 12. In addition to the role of joining the honeycomb segments 18, the joining material can also be used as an outer peripheral coating material after joining the honeycomb segments 18.

[0048] (1-7) Manufacturing method The manufacturing method of the ceramic body according to an embodiment of the present invention includes a forming step and a firing step. Hereinafter, the case of manufacturing a ceramic body (honeycomb structure 10) having a honeycomb shape will be described as an example. In the forming process, a ceramic raw material containing BaCO3 powder, TiO2 powder, and a powder of a rare earth nitrate and / or hydroxide is used to form a clay, and a ceramic formed body (hereinafter sometimes referred to as a "honeycomb formed body") having a relative density of 60% or more is produced. In particular, by using a powder of a rare earth hydroxide as the ceramic raw material, aggregation of the BaCO3 powder in the clay can be suppressed, so that uniform liquid phase formation and grain growth can be promoted in the firing process. As a result, it is easy to obtain a honeycomb structure 10 having a low electrical resistance at room temperature. The rare earth is one or more selected from the group consisting of La, Ce, Pr, Nd, Eu, Gd, Dy, Ho, Er, and Yb, and preferably La. The ceramic raw material can be obtained by dry-mixing each powder so as to have a desired composition. The clay can be obtained by adding a dispersion medium, a binder, a plasticizer, and a dispersant to the ceramic raw material and kneading them. The clay may contain additives such as a shifter, a metal oxide, a property improver, and a conductive powder as necessary. The blending amount of components other than the ceramic raw material is not particularly limited as long as the relative density of the ceramic formed body is 60%.

[0049] Here, in this specification, the "relative density of the ceramic formed body" means the ratio of the density of the ceramic formed body to the true density of the entire ceramic raw material. Specifically, it can be obtained by the following formula. Relative density of ceramic formed body (%) = density of ceramic formed body (g / cm 3 ) / true density of entire ceramic raw material (g / cm 3 ) × 100 The density of the ceramic formed body can be measured by the Archimedes method using pure water as a medium. The true density of the entire ceramic raw material can be obtained by dividing the total value (g) of the masses of the respective raw materials by the total value (cm 3 ) of the actual volumes of the respective raw materials.

[0050] Examples of the dispersion medium include water or a mixed solvent of water and an organic solvent such as alcohol. In particular, water can be preferably used.

[0051] Examples of the binder include organic binders such as methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. In particular, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The binder may be used alone or in combination of two or more, but preferably does not contain an alkali metal element.

[0052] Examples of the plasticizer include polyoxyalkylene alkyl ether, polycarboxylic acid-based polymer, and alkyl phosphate ester.

[0053] As the dispersant, surfactants such as polyoxyalkylene alkyl ether, ethylene glycol, dextrin, fatty acid soap, and polyalcohol can be used. The dispersant may be used alone or in combination of two or more.

[0054] The ceramic molded body can be produced by extrusion molding of the clay. In extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0055] The relative density of the ceramic molded body obtained by extrusion molding is 60% or more, preferably 61% or more. By controlling the relative density of the ceramic molded body within such a range, it is possible to densify the ceramic body and reduce the electrical resistance at room temperature. The upper limit value of the relative density of the ceramic molded body is not particularly limited, but is generally 80%, preferably 75%.

[0056] The ceramic formed body can be dried before the firing process. The drying method is not particularly limited, and for example, conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, vacuum drying, freeze drying, etc. can be used. Among these, a drying method combining hot air drying with microwave drying or dielectric drying is preferable in that the entire formed body can be dried quickly and uniformly.

[0057] The firing process includes holding at 1150 - 1250°C and then raising the temperature to a maximum temperature of 1360 - 1430°C at a heating rate of 20 - 500°C / hour and holding for 0.5 - 5 hours. By holding the honeycomb formed body at a maximum temperature of 1360 - 1430°C for 0.5 - 5 hours, a ceramic body (honeycomb structure 10) mainly composed of BaTiO3 - based crystal particles in which part of Ba is substituted with rare earth elements can be obtained. Also, by holding at 1150 - 1250°C, Ba2TiO4 crystal particles generated during the firing process are easily removed, so that the honeycomb structure 10 can be densified. Furthermore, by setting the heating rate from 1150 - 1250°C to the maximum temperature of 1360 - 1430°C to 20 - 500°C / hour, 1.0 - 10.0 mass% of Ba6Ti 17 O 40 crystal particles can be generated in the honeycomb structure 10.

[0058] The holding time at 1150 - 1250°C is not particularly limited, but is preferably 0.5 - 5 hours. By setting such a holding time, Ba2TiO4 crystal particles generated during the firing process are stably and easily removed.

[0059] The firing process preferably includes holding at 900 - 950°C for 0.5 - 5 hours. By holding at 900 - 950°C for 0.5 - 5 hours, BaCO3 decomposes efficiently, and it becomes easy to obtain the honeycomb structure 10 having a predetermined composition.

[0060] Before the firing process, a degreasing process for removing the binder may be performed. The atmosphere of the degreasing process is preferably an air atmosphere in order to completely decompose the organic components. Also, the atmosphere of the firing process is preferably an air atmosphere from the viewpoints of controlling electrical characteristics and manufacturing cost. The firing furnace used in the firing process or the degreasing process is not particularly limited, and an electric furnace, a gas furnace, or the like can be used.

[0061] <Heater element> The heater element according to an embodiment of the present invention includes the above-described ceramic body (for example, the honeycomb structure 10). FIG. 3 is a schematic perspective view of a heater element according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of the heater element of FIG. 3 orthogonal to the direction in which the cells of the honeycomb structure extend. A heater element 100 according to an embodiment of the present invention includes a honeycomb structure 10 and a pair of electrodes 20 disposed on the surface of the outer peripheral wall 11 of the honeycomb structure 10.

[0062] The honeycomb structure 10 used for the heater element 100 preferably has a shape having a major axis and a minor axis in a cross section orthogonal to the direction in which the cells 14 extend. The pair of electrodes 20 are formed in a strip shape extending parallel to the direction in which the cells 14 extend, and in a cross section orthogonal to the direction in which the cells 14 extend, are preferably disposed on the surface of the outer peripheral wall 11 so as to face each other across the major axis passing through the center of gravity of the honeycomb structure 10. Further, the heater element 100 preferably further includes a plate-shaped external connection member 30 disposed on the end side of each electrode 20 and in planar contact with each electrode 20. By disposing the electrodes 20 and the external connection member 30 in this way, the electrodes 20 and the external connection member 30 are in surface contact, and it becomes easy to increase the power supply amount from the outside, so that the heat generation performance can be improved.

[0063] FIG. 5 is a schematic end view of another heater element according to an embodiment of the present invention (i.e., a schematic front view of another heater element according to an embodiment of the present invention as viewed from the first end face side of the honeycomb structure). Further, FIG. 6 is a schematic cross-sectional view taken along line a-a' of the heater element of FIG. 5 (i.e., a schematic cross-sectional view of the heater element of FIG. 5 parallel to the direction in which the cells of the honeycomb structure extend). The heater element 200 according to an embodiment of the present invention includes a honeycomb structure 10 and a pair of electrodes 20 disposed on the surfaces of the outer peripheral wall 11 and the partition wall 12 at the first end face 13a and the second end face 13b of the honeycomb structure 10.

[0064] The honeycomb structure 10 used for the heater element 200 preferably has a shorter length in the direction in which the cells 14 extend. With such a structure, it is possible to apply a honeycomb structure 10 having a low electrical resistance at room temperature even to the heater element 200 having a structure in which a pair of electrodes 20 are disposed on the first end face 13a and the second end face 13b. Further, the heater element 200 preferably further includes a plate-shaped external connection member 30 that is in planar contact with each of the electrodes 20 at at least a part of the pair of electrodes 20. By providing such an external connection member 30, it becomes possible to efficiently energize the entire pair of electrodes 20 and improve the heat generation performance. Hereinafter, each component of the heater elements 100 and 200 will be described in detail.

[0065] (2-1) A pair of electrodes 20 in the heater element 100 The pair of electrodes 20 can be provided on the surface of the outer peripheral wall 11 of the honeycomb structure 10. The pair of electrodes 20 are formed in a strip shape extending parallel to the direction in which the cells 14 of the honeycomb structure 10 extend. Further, the pair of electrodes 20 are disposed on the surface of the outer peripheral wall 11 so as to face each other with the major axis passing through the center of gravity of the honeycomb structure 10 in a cross section orthogonal to the direction in which the cells 14 of the honeycomb structure 10 extend. By applying a voltage to the pair of electrodes 20 arranged in this way, it becomes possible to energize and heat the honeycomb structure 10 by Joule heat.

[0066] The electrode 20 is not particularly limited. For example, a metal or alloy containing at least one selected from Zn, Cu, Ag, Al, Ni, and Si can be used. Also, an ohmic electrode layer capable of making ohmic contact with the outer peripheral wall 11 and / or the partition wall 12 having PTC characteristics can be used. The ohmic electrode layer contains, for example, at least one selected from Al, Au, Ag, and In as a base metal and at least one selected from Ni, Si, Ge, Sn, Se, and Te for an n-type semiconductor as a dopant, and an ohmic electrode layer can be used. Further, the electrode 20 may be a single layer or two or more layers. When the electrode 20 has two or more layers, the materials of the respective layers may be of the same type or different types.

[0067] The thickness of the electrode 20 is not particularly limited and can be appropriately set according to the formation method of the electrode 20. Examples of the formation method of the electrode 20 include metal deposition methods such as sputtering, vapor deposition, electrolytic deposition, and chemical deposition. Also, the electrode 20 can be formed by applying an electrode paste and then baking it. Further, the electrode 20 can be formed by thermal spraying. The thickness of the electrode 20 is preferably about 5 to 30 μm in the case of baking an electrode paste, about 100 to 1000 nm in the case of dry plating such as sputtering and vapor deposition, about 10 to 100 μm in the case of thermal spraying, and about 5 to 30 μm in the case of wet plating such as electrolytic deposition and chemical deposition.

[0068] (2-2) A pair of electrodes 20 in the heater element 200 The pair of electrodes 20 can be provided on the surfaces of the outer peripheral wall 11 and the partition wall 12 at the first end face 13a and the second end face 13b of the honeycomb structure 10. The pair of electrodes 20 is preferably provided on the first end face 13a and the second end face 13b without closing the cell 14, and more preferably provided on the entire first end face 13a and the second end face 13b without closing the cell 14. Since other features of the electrode 20 are the same as those in (2-1), the description thereof is omitted.

[0069] (2-3) The external connection member 30 in the heater element 100 The external connection member 30 is plate-shaped and can be provided on the end side of each electrode 20 so as to be in contact with each electrode 20 in a plane. The external connection member 30 preferably extends parallel to the major axis passing through the center of gravity of the honeycomb structure 10 in a cross section orthogonal to the direction in which the cells 14 of the honeycomb structure 10 extend. By providing such a plate-shaped external connection member 30, it becomes easier to increase the power supply amount from the outside to the electrode 20, so that the heat generation performance can be improved. Here, in this specification, the "end side of each electrode 20" means a region from the end of each electrode 20 to 30% of the total length of each electrode 20 in the major axis direction passing through the center of gravity of the honeycomb structure 10 in a cross section orthogonal to the direction in which the cells 14 of the honeycomb structure 10 extend. The external connection member 30 only needs to be disposed on the end side of each electrode 20 and does not necessarily have to be in contact with the end of each electrode 20. For example, a bent portion may be formed in the external connection member 30 and the bent portion may be connected to each electrode 20.

[0070] The external connection member 30 preferably has a width substantially the same as the width of the end of the electrode 20 on the side where the external connection member 30 is disposed. By adopting such a configuration, the contact area between the electrode 20 and the external connection member 30 becomes large, so that the effect of improving the heat generation performance is enhanced. Here, in this specification, the "width substantially the same as the width of the end of the electrode 20" means within ±20% of the width of the end of the electrode 20.

[0071] Each of the external connection members 30 is preferably disposed on one end side of the electrode 20 parallel to the direction in which the cells 14 of the honeycomb structure 10 extend. The one end side where the external connection member 30 is disposed may be on the same side or different sides in a cross section orthogonal to the direction in which the cells 14 of the honeycomb structure 10 extend. The one end side is more preferably on the same side. And each of the external connection members 30 preferably extends in the same direction from that end side toward the outside. By adopting such a configuration, when the honeycomb structure 10 is applied to the heater element 100, it is possible to make it more compact.

[0072] The material of the external connection member 30 is not particularly limited, and for example, it can be a metal. As the metal, a single metal, an alloy, etc. can also be adopted, but from the viewpoints of corrosion resistance, electrical resistivity, and linear expansion coefficient, for example, it is preferable to use an alloy containing at least one selected from the group consisting of Cr, Fe, Co, Ni, Cu, and Ti, and stainless steel, Fe-Ni alloy, and phosphor bronze are more preferable. The shape and size of the external connection member 30 are not particularly limited, and may be appropriately adjusted according to the structure of the heater unit to be manufactured.

[0073] The connection method between the external connection member 30 and the electrode 20 is not particularly limited as long as they are electrically connected, and for example, they can be connected by diffusion bonding, a mechanical pressing mechanism, welding, etc.

[0074] (2-4) External connection member 30 in the heater element 200 The external connection member 30 is plate-shaped and can be provided so as to be in planar contact with each electrode 20. The external connection member 30 is preferably disposed on the electrode 20 provided on the outer peripheral wall 11 of the first end face 13a and the second end face 13b. By adopting such a configuration, it is possible to efficiently energize the entire electrode 20. Since other features of the external connection member 30 are the same as those in (2-3), the description thereof is omitted.

[0075] (2-5) Usage method The heater elements 100 and 200 according to the embodiments of the present invention can be suitably used as heater elements for heating the passenger compartment of a vehicle. The heater elements 100 and 200 according to the embodiments of the present invention can be heated by applying a voltage from an external power source to the honeycomb structure 10 via the external connection member 30 and the electrodes 20. The applied voltage is preferably 12 to 800V. Specifically, for the heater element 100, the applied voltage is preferably 100 to 800V. For the heater element 200, the applied voltage is preferably 12 to 60V. By adjusting the applied voltage within this range, rapid heating can be performed while suppressing power consumption. Also, since the voltage is low, the safety is high. Furthermore, since the safety specifications do not become heavy, the devices around the heater can be manufactured at low cost.

[0076] When the honeycomb structure 10 is generating heat due to the application of voltage, the gas can be heated by flowing gas through the cells 14. The temperature of the gas flowing into the cells 14 can be, for example, -60°C to 20°C, and typically -10°C to 20°C.

[0077] The heater element 100 according to the embodiments of the present invention uses a honeycomb structure 10 having low electrical resistance at room temperature and PTC characteristics, so it can be driven at low voltage. In addition, the heater element 100 according to the embodiments of the present invention has a simpler structure than the existing heater element in which a PTC element and an aluminum fin are integrated via an insulating ceramic plate, and it is possible to suppress the enlargement of the heater unit. Also, in the existing heater element, since the PTC element does not directly contact the gas, the temperature increase rate (temperature increase time) of the gas is not sufficient. However, in the heater element 100 according to the embodiments of the present invention, since the honeycomb structure 10 in which the outer peripheral wall 11 and the partition wall 12 are made of a material having PTC characteristics directly contacts the gas, the temperature increase rate of the gas can be increased. Furthermore, by disposing the electrode 20 and the external connection member 30 as described above, the heater element 100 according to the embodiment of the present invention can easily increase the power supply amount from the outside to the electrode 20, so that the heat generation performance can be improved.

[0078] <Heater unit> The heater unit according to the embodiment of the present invention can be suitably used as a heater unit for heating a vehicle compartment. In particular, since the heater unit according to the embodiment of the present invention uses a ceramic body (honeycomb structure 10) having a PTC characteristic and a low electric resistance at room temperature for the heater elements 100 and 200, it can be driven at a low voltage. In particular, by arranging a plurality of heater elements 100 and 200 in parallel, a practical heater unit that can be used at a low voltage can be obtained. Further, since the heater unit according to the embodiment of the present invention uses heater elements 100 and 200 having high heat generation performance, the heat generation performance of the heater unit can be improved. Furthermore, since the heater elements 100 and 200 can be made compact, it is possible to suppress the enlargement of the heater unit.

[0079] FIG. 7 is a schematic front view of a heater unit according to an embodiment of the present invention as viewed from the first end face side of the honeycomb structure. As shown in FIG. 7, the heater unit 600 according to the embodiment of the present invention includes two or more heater elements 100. In this heater unit 600, the heater elements 100 are stacked and arranged such that the surfaces of the outer peripheral wall 11 of the honeycomb structure 10 including the long sides of the first end face 13a and the second end face 13b face each other. By adopting such a configuration, a compact heater unit 600 can be manufactured.

[0080] The heater unit 600 according to the embodiment of the present invention can further include a housing (housing member) 610. The material of the housing 610 is not particularly limited, and examples include metal, resin, etc. Among them, the material of the housing 610 is preferably resin. By using a resin housing 610, it is possible to suppress electric shock without grounding. The shape and size of the housing 610 are not particularly limited, and can be the same as those of existing heater units.

[0081] The heater unit 600 according to the embodiment of the present invention can further include an insulating material 620 disposed between the heater elements 100 arranged in a stacked manner. With such a configuration, it is possible to suppress an electrical short between the plurality of heater elements 100. As the insulating material 620, a plate material, mat, cloth, etc. formed from an insulating material such as alumina or ceramics can be used.

[0082] The heater unit 600 according to the embodiment of the present invention can have a wiring structure capable of controlling the heater element 100. Specifically, the heater unit 600 according to the embodiment of the present invention can further include a wiring 630 connected to the external connection member 30 of the heater element 100. The wiring structure is not particularly limited, but as shown in FIG. 7, it can be a wiring structure capable of independently controlling each of the heater elements 100. Specifically, the wiring 630 can be connected to each of the external connection members 30 of the heater element 100. Note that the wiring 630 is connected to an external power source (not shown). With such a wiring structure, since each of the heater elements 100 can be independently controlled, fine temperature adjustment becomes possible.

[0083] As shown in FIG. 8, the wiring structure may be a parallel wiring structure capable of collectively controlling two or more heater elements 100. Specifically, a parallel wiring 640a may be connected to one external connection member 30 of each heater element 100, and one parallel wiring 640b may be connected to the other external connection member 30. By adopting such a wiring structure, the power consumption of the heater unit 700 can be suppressed.

[0084] Also, as shown in FIG. 9, the electrode 20 between the heater elements 100 arranged in a stacked manner may be a single electrode 20 common to the heater elements 100 arranged in a stacked manner, and a parallel wiring structure capable of collectively controlling two or more heater elements 100 may be adopted. Specifically, the external connection member 30 may be disposed at the end of the electrode 20, a parallel wiring 640a may be connected to one external connection member 30 of each heater element 100, and one parallel wiring 640b may be connected to the other external connection member 30. By adopting such a structure, it is not necessary to dispose an insulating material 620 between the heater elements 100 arranged in a stacked manner, so that the heater unit 800 can be made compact, and moreover, the power consumption can be suppressed.

[0085] <Heater system> The heater system according to the embodiment of the present invention can be suitably used as a heater system for heating a vehicle compartment. In particular, in the heater system according to the embodiment of the present invention, since the heater unit 600 that can be driven at a low voltage is used, the power consumption can be suppressed. Also, in the heater system according to the embodiment of the present invention, since the heater unit 600 having high heat generation performance is used, the heat generation performance of the heater system can be improved. Furthermore, since the heater unit 600 can be made compact, it is possible to suppress the enlargement of the heater system.

[0086] FIG. 10 is a schematic diagram showing a configuration example of the heater system according to the embodiment of the present invention. As shown in FIG. 10, a heater system 900 according to an embodiment of the present invention includes a heater unit 600 according to an embodiment of the present invention, inflow pipes 920a and 920b that communicate the outside air introduction part or the passenger compartment 910 with the inlet 650 of the heater unit 600, a battery 940 for applying a voltage to the heater unit 600, and an outflow pipe 930 that communicates the outlet 660 of the heater unit 600 with the passenger compartment 910. Instead of the heater unit 600, it is also possible to use heater units 700 and 800 according to embodiments of the present invention.

[0087] The heater unit 600 can be configured, for example, to be connected to the battery 940 by an electric wire 950 and to generate heat by being energized by turning on a power switch in the middle thereof.

[0088] A vapor compression heat pump 960 can be installed upstream of the heater unit 600. In the heater system 900, the vapor compression heat pump 960 is configured as a main heating device, and the heater unit 600 is configured as an auxiliary heater. The vapor compression heat pump 960 can include a heat exchanger including an evaporator 961 that functions to absorb heat from the outside and evaporate the refrigerant during cooling, and a condenser 962 that functions to liquefy the refrigerant gas and release heat to the outside during heating. Note that the vapor compression heat pump 960 is not particularly limited, and those known in the art can be used.

[0089] A blower 970 can be installed on the upstream side and / or the downstream side of the heater unit 600. From the perspective of ensuring safety by placing high-voltage components as far away from the passenger compartment 910 as possible, it is preferable to install the blower 970 on the upstream side of the heater unit 600. When the blower 970 is driven, air flows into the heater unit 600 from inside or outside the passenger compartment 910 through the intake pipes 920a and 920b. The air is heated while passing through the heater unit 600 that is generating heat. The heated air flows out of the heater unit 600 and is sent into the passenger compartment 910 through the outlet pipe 930. The outlet of the outlet pipe 930 may be arranged near the feet of the passengers so that the heating effect is particularly high inside the passenger compartment 910, or the pipe outlet may be arranged inside the seat cushion to warm the seat cushion from the inside, or it may be arranged near the window to also have the effect of suppressing fogging of the window.

[0090] The intake pipe 920a and the intake pipe 920b merge midway. Valves 921a and 921b can be installed in the intake pipes 920a and 920b, respectively, on the upstream side of the merging point. By controlling the opening and closing of the valves 921a and 921b, it is possible to switch between a mode of introducing outside air into the heater unit 600 and a mode of introducing the air inside the passenger compartment 910 into the heater unit 600. For example, when the valve 921a is opened and the valve 921b is closed, it becomes a mode of introducing outside air into the heater unit 600. It is also possible to open both the valve 921a and the valve 921b to simultaneously introduce outside air and the air inside the passenger compartment 910 into the heater unit 600.

[0091] <Purification System> The purification system according to the embodiment of the present invention can also be suitably used as a purification system for removing harmful components in the passenger compartment of a vehicle. In particular, the purification system according to the embodiment of the present invention uses a heater element made of a ceramic body having a low electrical resistance at room temperature, or a heater unit including two or more heater elements, so that purification performance can be obtained while suppressing power consumption. The heater element used in the purification system according to an embodiment of the present invention includes the above-described ceramic body (honeycomb structure 10), an adsorbent provided on the surface of the partition wall 12 of the honeycomb structure 10, and a pair of electrodes 20 provided on the first end face 13a and the second end face 13b of the honeycomb structure 10.

[0092] Here, FIG. 11 shows a schematic enlarged cross-sectional view orthogonal to the direction in which the cells 14 of the honeycomb structure 10 provided with the adsorbent extend. As shown in FIG. 11, an adsorbent 50 is provided on the surface of the partition wall 12 of the honeycomb structure 10. By providing the adsorbent 50 in this way, harmful volatile components can be adsorbed from the air flowing through the cells 14. Harmful volatile components are, for example, volatile organic compounds (VOCs), odor components, etc. Specific examples of harmful volatile components include ammonia, acetic acid, isovaleric acid, nonenal, formaldehyde, toluene, xylene, paradichlorobenzene, ethylbenzene, styrene, chlorpyrifos, di-n-butyl phthalate, tetradecane, di-2-ethylhexyl phthalate, diazinon, acetaldehyde, N-methylcarbamic acid-2-(1-methylpropyl)phenyl. The adsorbent 50 may be appropriately selected according to the volatile components to be adsorbed, and is not particularly limited. Examples of the adsorbent 50 include zeolite. Also, if an adsorbent 50 capable of adsorbing CO2 at room temperature and desorbing CO2 at high temperature is selected, the CO2 in the vehicle interior can be discharged to the outside of the vehicle. Furthermore, by using a combination of a noble metal such as Pt or an oxidation catalyst of a metal oxide together with the adsorbent 50, it becomes easier to remove harmful volatile components from the air flowing through the cells 14.

[0093] The heater element used in the purification system according to an embodiment of the present invention may be provided with an external connection member 30 on a pair of electrodes 20 provided on the first end face 13a and the second end face 13b (for example, the outer peripheral portion of the electrode 20 provided on the outer peripheral wall 11 of the honeycomb structure 10).

[0094] The heater element used in the purification system according to the embodiment of the present invention can be manufactured according to the above method. For example, after applying an electrode paste to the first end face 13a and the second end face 13b of the honeycomb structure 10 and baking it to form the electrodes 20, the heater element can be manufactured by coating the adsorbent 50 on the surface of the partition wall 12. The coating method of the adsorbent 50 is not particularly limited. For example, the honeycomb structure 10 is immersed in a slurry containing the adsorbent 50, an organic binder, and water, and the excess slurry on the end faces and the outer periphery of the honeycomb structure 10 is removed by blowing and wiping. Then, the adsorbent 50 can be provided on the surface of the partition wall 12 by drying at a temperature of about 550°C. This step may be performed once, but a desired amount of the adsorbent 50 can be provided on the surface of the partition wall 12 by repeating it a plurality of times. When providing the external connection member 30, the external connection member 30 may be arranged and joined at a predetermined position of the electrode 20.

[0095] FIG. 12 is a schematic diagram showing a configuration example of the purification system according to the embodiment of the present invention. As shown in FIG. 12, the purification system 1000 according to the embodiment of the present invention includes the above-described heater element or heater unit 1100, a battery (power source) 1200 for applying a voltage to a pair of electrodes 20 of the heater element or heater unit 1100, an inflow pipe 1300 that communicates the passenger compartment with the inlet 1110 of the heater element or heater unit 1100, an outflow pipe 1400 that communicates the outlet 1120 of the heater element or heater unit 1100 with the passenger compartment and the outside of the vehicle, and a switching valve 1500 provided in the outflow pipe 1400 and capable of switching the flow of air flowing through the outflow pipe 1400 to the passenger compartment or the outside of the vehicle.

[0096] The heater element or heater unit 1100 can be configured to be energized and generate heat by connecting it to the battery 1200 with an electric wire 1210 and turning on the power switch in the middle. The ON and OFF switching of the power switch can be performed by a control unit 1600 electrically connected to the power switch. Also, the switching of the switching valve 1500 can be performed by a control unit 1600 electrically connected to the switching valve.

[0097] In the purification system 1000 having the above structure, air from the passenger compartment is supplied to the heater element or heater unit 1100 from the inlet 1110 through the inflow pipe 1300. After the air is subjected to predetermined processing by the heater element or heater unit 1100, it is discharged from the outlet 1120 and returned to the passenger compartment through the outflow pipe 1400 or discharged to the outside of the vehicle. When the switching valve 1500 closes the flow path to the outside of the vehicle of the outflow pipe 1400 so that the air returns to the passenger compartment, the power switch is turned OFF to keep the heater element or heater unit 1100 at room temperature. By controlling in this way, harmful volatile components contained in the air from the passenger compartment can be removed by adsorbing them on the adsorbent 50 of the heater element or heater unit 1100. On the other hand, when the switching valve 1500 closes the flow path to the passenger compartment of the outflow pipe 1400 so that the air is discharged to the outside of the vehicle, the power switch is turned ON to heat the heater element or heater unit 1100. By controlling in this way, the harmful volatile components adsorbed on the adsorbent 50 of the heater element or heater unit 1100 can be desorbed, the function of the adsorbent 50 can be regenerated, and the harmful volatile components can be discharged to the outside of the vehicle. By repeating the switching of the power switch and the switching valve 1500 as described above in a certain cycle, it becomes possible to stably discharge harmful volatile components in the passenger compartment to the outside of the vehicle.

[0098] From the perspective of stably ensuring the above functions, it is desirable that the heater element or heater unit 1100 be arranged at a position close to the passenger compartment. Therefore, from the perspective of preventing electric shock, etc., it is preferable that the driving voltage be 60V or less. Since the honeycomb structure 10 used in the heater element or heater unit 1100 has a low electrical resistance at room temperature, it is possible to heat the honeycomb structure 10 at this low driving voltage. Note that the lower limit value of the driving voltage is not particularly limited, but it is preferably 10V. If the driving voltage is less than 10V, the current during heating of the honeycomb structure 10 increases, so the electric wire 1210 has to be thickened.

[0099] In the honeycomb structure 10 used in the heater element or heater unit 1100, a large amount of adsorbent 50 is provided on the surface of the partition wall 12. From the perspective of sufficiently ensuring its adsorption function, it is preferable that the aperture ratio of the cells 14, the cell density, and the surface area of the partition wall 12 be large. In a typical embodiment, in the honeycomb structure 10, the aperture ratio of the cells 14 is preferably 75% or more, more preferably 80% or more. Also, the cell density is preferably 15 to 94 cells / cm 2 , more preferably 31 to 70 cells / cm 2 . Further, the diameter of the minor axis (the thickness of the honeycomb structure 10) in the cross section orthogonal to the direction in which the cells 14 extend is preferably 3 to 15 mm, more preferably 4 to 10 mm.

[0100] If the diameter of the minor axis (the thickness of the honeycomb structure 10) in the cross section orthogonal to the direction in which the cells 14 extend is small, there is a risk that the amount of the adsorbent 50 is insufficient. Therefore, from the perspective of sufficiently ensuring the adsorption function, it is preferable to use the heater unit in the purification system 1000. As described above, the heater unit can be manufactured by arranging a plurality of heater elements in parallel. By using the heater unit, the amount of the adsorbent 50 can be increased, and the heating rate and cooling rate of the honeycomb structure 10 can be increased when the power switch is turned on and off. Therefore, the practicality of the purification system 1000 can be enhanced.

[0101] From the perspective of efficiently enhancing the adsorption function of the adsorbent 50, the thickness of the adsorbent 50 provided on the surface of the partition wall 12 should preferably not be too large. This is because if the adsorbent 50 is too thick, it will be difficult to come into contact with the air flowing in the cell 14, resulting in a decrease in the efficiency of the adsorption function. Therefore, the thickness of the adsorbent 50 is preferably 0.01 to 0.5 mm.

Example

[0102] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited by these examples in any way.

[0103] (1) Preparation of ceramic body <Examples 1 to 9, Comparative Examples 1 to 4> BaCO3 powder, TiO2 powder, and La(NO3)3·6H2O powder were prepared as ceramic raw materials. These powders were weighed so as to have the compositions shown in Table 1 after firing and dry-mixed to obtain a mixed powder. The dry mixing was carried out for 30 minutes. Next, with respect to 100 parts by mass of the obtained mixed powder, water, a binder, a plasticizer, and a dispersant were added in appropriate amounts in a total range of 3 to 30 parts by weight so that a ceramic molded body having a relative density shown in Table 1 could be obtained after extrusion molding, and kneaded to obtain a clay. Methyl cellulose was used as the binder. Polyoxyalkylene alkyl ether was used as the plasticizer and the dispersant. This clay was put into an extrusion molding machine and extrusion molded using a predetermined die to obtain a honeycomb molded body in the shape of a rectangular parallelepiped. Then, the density of the honeycomb molded body was measured according to the above method. Next, the obtained honeycomb molded body was subjected to dielectric drying and hot air drying, and then both bottom surfaces were cut to have a predetermined dimension to obtain a honeycomb dried body.

[0104] The shape of the honeycomb dried body is as follows. Overall shape: Rectangular parallelepiped shape of 45 mm × 45 mm × height (direction in which the cells extend) 200 mm Cell shape in the cross section orthogonal to the direction in which the cells extend: Square Cell density: 62 cells / cm2 Thickness of the adjacent wall: 4 mil (101.6 μm)

[0105] Next, after cutting so that the height of the honeycomb green body becomes 35 mm, it was degreased (450 °C × 4 hours) in an air atmosphere in a firing furnace, and then fired in an air atmosphere to obtain a ceramic body. The conditions of the firing process were as shown in Table 1. Specifically, in the firing process, holding process A, holding process B, and holding process C were sequentially performed. Note that holding process C is the holding process at the maximum temperature. The following evaluations were performed on the obtained ceramic body.

[0106] <Examples 10 and 11> A ceramic body was produced in the same manner as in Example 1 above, except that La(OH)3 powder was used instead of La(NO3)3·6H2O powder, and the following evaluations were performed.

[0107] (2) Chemical analysis The chemical composition of the ceramic body was analyzed by ICP emission spectrometry to determine the atomic ratios of elements such as La, Ba, and Ti. The atomic ratio (x value) of La and the (Ba + La) / Ti ratio of BaTiO3-based crystal particles obtained by this analysis are shown in Table 1. Also, from this analysis result, it was confirmed that the ceramic bodies produced in the examples and comparative examples do not contain Pb and alkali metals.

[0108] (3) Identification of crystal particles and lattice volume of BaTiO3-based crystal particles The crystal particles of the ceramic body were identified using an X-ray diffractometer. As the X-ray diffractometer, a multifunctional powder X-ray diffractometer (manufactured by Bruker, D8 Advance) was used. The conditions for X-ray diffraction measurement were CuKα radiation source, 10 kV, 20 mA, and 2θ = 5 to 100°. Then, the obtained X-ray diffraction data was analyzed by the Rietveld method using analysis software TOPAS (manufactured by Bruker AXS) to identify the crystal particles. The lattice volume of the BaTiO3-based crystal particles was determined by calculating from the lattice constants obtained by the analysis of the X-ray diffraction data. These results are shown in Table 1.

[0109] (4) Content of each crystal particle The content of each crystal particle was measured using an X-ray diffractometer. As the X-ray diffractometer, the same apparatus and analysis software as described above were used, and the content of each crystal particle was determined by the Rietveld method.

[0110] (5) Measurement of average crystal grain size The average crystal grain size of the ceramic body was measured according to the above method. SEM observation was performed using a model S-3400N manufactured by Hitachi High-Technologies Corporation at an acceleration voltage of 15 kV and a magnification of 3000. The results are shown in Table 1.

[0111] (6) Apparent porosity The apparent porosity of the ceramic body was measured according to the above method. The results are shown in Table 1.

[0112] (7) Bulk density The bulk density of the ceramic body was measured according to the above method. The results are shown in Table 1.

[0113] (8) Volume resistivity The volume resistivity of the ceramic body at room temperature (25 °C) was measured according to the above method. The measured value of the volume resistivity was taken as the average value of the measured volume resistivities. The results are shown in Table 1.

[0114]

Table 1

[0115] As shown in Table 1, the ceramic bodies of Examples 1 to 11 had a significantly lower volume resistivity at room temperature than the ceramic bodies of Comparative Examples 1 to 4. In particular, the ceramic bodies of Examples 4 and 6 to 11 were able to reduce the volume resistivity at room temperature to 30 Ω·cm or less.

[0116] As can be seen from the above results, according to the present invention, it is possible to provide a ceramic body having PTC characteristics with low electrical resistance at room temperature and a method for manufacturing the same. Further, according to the present invention, it is possible to provide a heater element provided with such a ceramic body.

Explanation of Signs

[0117] 10 Honeycomb structure 11 Outer peripheral wall 12 Partition wall 13a First end face 13b Second end face 14 Cell 17 Honeycomb joint 18 Honeycomb segment 19 Bonding layer 20 Electrode 30 External connection member 50 Adsorbent 100,200 Heater element 600,700,800 Heater unit 610 Housing 620 Insulating material 650,1110 Inlet 660,1120 Outlet 900 Heater system 910 Passenger compartment 920a,920b,1300 Inflow pipe 921a,921b Valve 930,1400 Outflow pipe 940,1200 Battery 950,1210 Electric wire 960 Vapor compression heat pump 961 Evaporator 962 Condenser 970 Blower 1000 Purification system 1100 Heater element or heater unit 1500 Switching valve 1600 Control unit

Claims

1. BaTiO with a part of Ba replaced by La 3 system crystal particles as the main component, Ba 6 Ti 17 O 40 contains 1.0 to 10.0% by mass of crystal particles The compositional formula of the BaTiO₃-based crystalline particles is represented by (Ba₁₋ₓAₓ)TiO₃ (where A represents La and 0.001 ≤ x ≤ 0.010), and the BaTiO₃-based crystalline particles are a ceramic body with a (Ba + La) / Ti ratio of 1.005 to 1.

050.

2. The above-mentioned BaTiO 3 The lattice volume of the crystalline particles in the system is 64.4000 to 64.3650 Å 3 The ceramic body according to claim 1, which is such.

3. The above-mentioned BaTiO 3 The ceramic body according to claim 1 or 2, wherein the average crystal grain size of the bound crystal particles is 5 to 200 μm.

4. The ceramic body according to any one of Claims 1 to 3, having an open porosity of 5.0% or less.

5. The bulk density is 5.35 g / cm 3 or more, the ceramic body according to any one of claims 1 to 4.

6. BaCO 3 The ceramic body according to any one of claims 1 to 5, containing 2.0% by mass or less of crystal particles.

7. The ceramic body according to any one of Claims 1 to 6, having a Pb content of 0.01% by mass or less.

8. The ceramic body according to any one of Claims 1 to 7, having an alkali metal content of 0.01% by mass or less.

9. The ceramic body according to any one of Claims 1 to 8, having a volume resistivity measured at 25°C of 150 Ω·cm or less.

10. The ceramic body according to Claim 9, having a volume resistivity of 30 Ω·cm or less.

11. A honeycomb-shaped ceramic body according to any one of Claims 1 to 10, including an outer peripheral wall and a partition wall disposed inside the outer peripheral wall and partitioning a plurality of cells that form a flow path from a first end face to a second end face.

12. The average thickness of the partition wall is 50 to 130 μm, and the cell density is 15 to 140 cells / cm 2 The ceramic body according to claim 11, which is such.

13. A method for manufacturing a ceramic body according to any one of Claims 1 to 12, BaCO 3 powder, TiO 2 powder, and a ceramic raw material containing a powder of a nitrate and / or hydroxide of La are molded to produce a ceramic green compact having a relative density of 60% or more; a molding step including a firing step of holding the ceramic green body at 1150 to 1250°C and then raising the temperature to a maximum temperature of 1360 to 1430°C at a heating rate of 20 to 500°C / h and holding for 0.5 to 5 hours, and the method includes this step.

14. The method according to Claim 13, having a holding time at 1150 to 1250°C of 0.5 to 5 hours.

15. The method according to Claim 13 or 14, wherein the firing step includes holding at 900 to 950°C for 0.5 to 5 hours.

16. The method according to any one of Claims 13 to 15, wherein the ceramic raw material includes a powder of the hydroxide of La.

17. A heater element including a ceramic body according to any one of Claims 1 to 12.

18. The heater element according to Claim 17, for heating a vehicle compartment.

19. A heater unit including two or more heater elements according to Claim 17 or 18.

20. The heater unit according to Claim 19, an inflow pipe that communicates an outside air introduction part or a vehicle compartment with an inlet of the heater unit. A battery for applying voltage to the heater unit, and An outflow pipe that communicates the outlet of the heater unit with the passenger compartment A heater system comprising the same.

21. A heater element having the ceramic body according to claim 11, an adsorbent provided on the surface of the partition wall of the ceramic body, and a pair of electrodes provided on the first end face and the second end face of the ceramic body, or a heater unit including two or more of the heater elements, A battery for applying voltage to the pair of electrodes of the heater element, An inflow pipe that communicates the passenger compartment with the inlet of the heater element or the heater unit, An outflow pipe that communicates the outlet of the heater element or the heater unit with the passenger compartment and the outside of the vehicle, and A switching valve provided in the outflow pipe and capable of switching the flow of air flowing through the outflow pipe to the passenger compartment or the outside of the vehicle A purification system comprising the same.

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