JP2022109861A - Ceramic body and manufacturing method thereof, heater element, heater unit, heater system, and purification system - Google Patents

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 The present invention relates to a ceramic body and its manufacturing method, a heater element, a heater unit, a heater system and a purification system.

Conventionally, as a material exhibiting PTC (Positive Temperature Coefficient) characteristics, a ceramic body having a composition represented by BaTiO ₃ to which various additive elements are added has been proposed. The PTC characteristic is a characteristic in which the resistance value increases sharply when the temperature rises above the Curie point. Ceramic bodies having PTC characteristics are used in PTC heaters, PTC switches, overcurrent protection elements, temperature detectors, and the like, and various characteristics have been improved depending on the application.

In Patent Document 1, Y, Ho, Er, and Yb are used in BaTiO ₃ , and La, Dy, Eu, and Gd are added in combination with Y, Ho, Er, and Yb in appropriate amounts, so that the change over time is small. , a ceramic composition for a PTC thermistor having practical values for room temperature resistivity and temperature coefficient of resistance can be obtained.

In Patent Document 2, the main component is a B _m TiO ₃ -based composition having a perovskite structure represented by the general formula A _m BO ₃ , and 0.05 mol % or more and 0.3 mol of 100 mol % of Ti % or less, W is substituted as a semiconducting agent, and m, which is the ratio 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%, the temperature at which the Ca content is 15 mol% or less and the resistance value is double the resistance value at 25 ° C. is 2 It describes a semiconducting ceramic having a double point of 100° C. or higher and a measured sintered density of 70% or more and 90% or less of the theoretical sintered density. The semiconductor ceramic is said to have stable PTC characteristics, a high double point, and a wide operating temperature range.

In Patent Document 3, in a barium titanate-based PTC thermistor, part of Ba is replaced with Bi and alkali metal A (Na or K) within a predetermined range instead of Pb, which has a high environmental load, and Ba site / By setting the molar ratio of the Ti site and the amount of Ca to be added within a predetermined range, it is easily converted to a semiconductor even in firing in the air or in a nitrogen atmosphere, the room temperature resistivity is low, and the Curie point is higher than 120 ° C. It is described that a PTC thermistor shifted to the high temperature side can be obtained. The document also describes that this PTC thermistor can reduce changes over time even when used as a heater element.

In Patent Document 4, 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, intragranular with respect to the reciprocal of Kelvin temperature By controlling the slope of the resistance change to be 135 or more and 340 or less and setting the average porcelain grain size after sintering to 0.8 μm or less, the room temperature specific resistance of the multilayer PTC thermistor is low, and the withstand voltage is high. It is stated that it can increase the

In Patent Document 5, barium titanate is the main component and a rare earth element is added, and the average grain size of the ceramic substrate is 0.3 [μm] or more and less than 0.5 [μm]. The lower limit of the relative density of the ceramic substrate is 70 [%], and the upper limit of the relative density of the ceramic substrate is -6.43d + 97.83 [%], where d is the average grain size of the ceramic substrate. A laminated PTC thermistor element using a substrate is described. The laminated PTC thermistor element is said to be able to achieve both low room temperature resistivity and high withstand voltage.

_In Patent Document 6, a BaTiO3 _- based composition having a perovskite structure represented by the general formula _AmBO3 is used as a main component, and a part of Ba constituting the A site is an alkali metal element, Bi, Ca, The content of Ca and Sr when the total number of moles of the elements that are substituted with Sr and the rare earth element and constitute the A site is 1 mol, and the molar ratio of Ca is x and the molar ratio of Sr is y. 0.05≦x≦0.20, 0.02≦y≦0.12, and 2x+5y≦0.7. there is The semiconducting ceramic is said to be excellent in reliability because its surface does not discolor even when it is energized for a long period of time, and its resistance value is suppressed from changing while maintaining a desired Curie point.

JP 2013-79160 A Japanese Patent No. 5510455 Japanese Patent No. 5930118 JP 2017-27980 A Japanese Patent No. 5970717 Japanese Patent No. 5327553

As described above, ceramic bodies having PTC characteristics have been improved from various viewpoints, but there is still room for further development.
For example, application of a honeycomb-shaped ceramic body to a heater element for heating is under study. A low electrical resistance at room temperature is required for this heater element to function at low voltages. In a heater element, a pair of electrodes is generally provided on the end face of a honeycomb-shaped ceramic body (a face perpendicular to the direction in which the cells extend). Corrosion of the pair of electrodes may occur. Therefore, it has been studied to provide a pair of electrodes on the side surfaces (surfaces parallel to the direction in which the cells extend) of the honeycomb-shaped ceramic body.
However, when a pair of electrodes is provided on the side surface of the ceramic body, the distance between the electrodes is larger than when the pair of electrodes is provided on the end face of the ceramic body, so it is required to lower the electrical resistance of the ceramic body at room temperature. be done. In particular, such a demand is great in the case of a honeycomb-shaped ceramic body having thin partition walls.

The present invention has been created in view of the above circumstances, and an object of the present invention is to provide a ceramic body having PTC characteristics, low electrical resistance at room temperature, and a method for producing the same. Another object of the present invention is to provide a heater element, a heater unit, a heater system, and a purifying system having such a ceramic body.

The inventors of the present invention conducted extensive research on ceramic bodies containing BaTiO ₃ -based crystal particles as a main component, and found that the presence of Ba ₆ Ti ₁₇ O ₄₀ crystal particles is closely related to the electrical resistance at room temperature. and completed the present invention.

That is, the present invention is a ceramic body containing, as a main component, BaTiO ₃ -based crystal particles in which a portion of Ba is replaced with a rare earth element, and Ba ₆ Ti ₁₇ O ₄₀ crystal particles in an amount of 1.0 to 10.0% by mass. .

In addition, the present invention is a method of forming a clay containing ceramic raw materials containing BaCO ₃ powder, TiO ₂ powder, and rare earth nitrate and/or hydroxide powder, and forming ceramics having a relative density of 60% or more. A molding step for producing a molded body;
and a sintering step of holding the ceramic compact at 1150 to 1250° C., then raising the temperature to a maximum temperature of 1360 to 1430° C. at a rate of 20 to 500° C./hour and holding the temperature for 0.5 to 5 hours. , a method for manufacturing a ceramic body.

Further, the present invention is a heater element comprising the ceramic body.

Further, the present invention is a heater unit including two or more of the heater elements.

Further, the present invention provides the heater unit,
an inflow pipe that communicates between an outside air introduction part or a vehicle compartment and an inflow port of the heater unit;
The heater system includes a battery for applying voltage to the heater unit, and an outflow pipe that communicates an outflow port of the heater unit and the vehicle interior.

Further, the present invention includes the ceramic body, 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. a heater element 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 communicating between the casing and the heater element or the inlet of the heater unit;
an outflow pipe that communicates with the outflow port of the heater element or the heater unit and the vehicle interior and the vehicle exterior; A purification system with a valve.

According to the present invention, it is possible to provide a ceramic body having PTC characteristics and a low electrical resistance at room temperature, and a method for producing the same. Moreover, according to the present invention, it is possible to provide a heater element, a heater unit, a heater system, and a purification system, which are equipped with such a ceramic body.

1 is a schematic perspective view of a ceramic body according to an embodiment of the invention; FIG. Fig. 3 is a schematic cross-sectional view perpendicular to the central axis of a honeycomb joined body having five honeycomb segments. 1 is a schematic perspective view of a heater element according to an embodiment of the invention; FIG. FIG. 3 is a schematic cross-sectional view of the heater element of FIG. 2 perpendicular to the cell extending direction of the honeycomb structure; FIG. 4 is a schematic end view of another heater element in accordance with embodiments of the present invention; FIG. 6 is a schematic cross-sectional view of the heater element of FIG. 5 taken along the line aa'; Fig. 3 is a schematic front view of the heater unit according to the embodiment of the present invention viewed from the first end face side of the honeycomb structure; FIG. 4 is a schematic front view of another heater unit according to the embodiment of the present invention viewed from the first end face side of the honeycomb structure; FIG. 4 is a schematic front view of another heater unit according to the embodiment of the present invention viewed from the first end face side of the honeycomb structure; It is a mimetic diagram showing an example of composition of a heater system concerning an embodiment of the present invention. Fig. 3 is a schematic enlarged cross-sectional view orthogonal to the direction in which the cells of the honeycomb structure provided with the adsorbent are extended. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the structural example of the purification system which concerns on embodiment of this invention.

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 modifications and improvements can be made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. are also within the scope of the present invention.

<Ceramic body>
(1-1) Crystal Structure and Composition A ceramic body according to an embodiment of the present invention is mainly composed of BaTiO ₃ -based crystal grains in which a part of Ba is replaced with a rare earth element. By using BaTiO ₃ -based crystal particles as a main component, it is possible to obtain a ceramic body that is capable of being electrically heated and has PTC characteristics. Also, by substituting a part of Ba in the BaTiO ₃ -based crystal particles with a rare earth element, the electrical resistance at room temperature (25° C.) can be lowered.
As used herein, the term "main component" means that the proportion of the total component is 50% by mass or more.

The composition formula of BaTiO3 _- based crystal grains in which Ba is partially substituted with a rare earth element can be represented by (Ba1 _{- xAx} ) _TiO3 . In the composition formula, A represents one or more rare earth elements and satisfies 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, more preferably It is La. From the viewpoint of preventing the electrical resistance at room temperature from becoming too high, 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, x is preferably 0.010 or less, more preferably 0.009 or less, and still more preferably 0.008 or less from the viewpoint of suppressing insufficient sintering and excessively high electrical resistance at room temperature. .

The BaTiO ₃ -based crystal particles in which a part of Ba is replaced with a rare earth element preferably have a (Ba+rare earth element)/Ti ratio of 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 lowered. The element ratio of Ba, rare earth elements and Ti can be determined by, for example, fluorescent X-ray analysis, ICP-MS (inductively coupled plasma mass spectrometry), or the like.

BaTiO ₃ -based crystal grains in which Ba is partially substituted with a rare earth element preferably has 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 lowered.
The lattice volume of the BaTiO ₃ -based crystal particles can be measured using an X-ray diffractometer. Specifically, the lattice volume can be measured from the lattice constant obtained by analyzing the X-ray diffraction data by the Rietveld method.

BaTiO ₃ -based crystal particles in which a part of Ba is substituted with a rare earth element preferably have an average crystal grain size of 5 to 200 μm, more preferably 5 to 180 μm, 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 lowered.
The average grain size of the BaTiO ₃ -based crystal grains can be measured as follows. A square sample of 5 mm×5 mm×5 mm is cut out from the ceramic body and embedded in resin. The embedded sample is mirror-polished by mechanical polishing and observed with an SEM. For SEM observation, for example, model S-3400N manufactured by Hitachi High-Technologies Corporation is used at an acceleration voltage of 15 kV and a magnification of 3000. In the SEM observation image (30 μm long × 45 μm wide), four straight lines with a thickness of 0.3 μm are drawn at intervals of ₁₀ μm across the entire vertical direction of the field of view. count. The length of the straight line is divided by the number of BaTiO ₃ -based crystal grains, and the average of four or more SEM observation images is taken as the average crystal grain size.

The content of the BaTiO ₃ -based crystal particles in which Ba is partially substituted with a rare earth element in the ceramic body is not particularly limited as long as it is the amount that becomes the main component, but is preferably 90.0% by mass or more, more preferably 92% by mass. 0% by mass or more, more preferably 94.0% by mass or more. Although the upper limit of the content of BaTiO ₃ -based crystal particles is not particularly limited, it is generally 99.0% by mass, preferably 98.0% by mass.
The content of BaTiO ₃ -based crystal particles can be measured by, for example, fluorescent X-ray analysis and EDAX (energy dispersive X-ray) analysis. Other crystal grains can also be measured in the same manner as this method.

A ceramic body according to an embodiment of the present invention contains Ba ₆ Ti ₁₇ O ₄₀ crystal grains. The presence of Ba ₆ Ti ₁₇ O ₄₀ crystal grains in the ceramic body can reduce the electrical resistance at room temperature. While not intending to limit the invention by theory, the _Ba6Ti17O40 crystal grains _liquefy during the firing process to promote rearrangement, grain growth and densification of the _{BaTiO3 -} based crystal grains. Therefore, it is considered that the electrical resistance at room temperature is lowered.

The content of Ba ₆ Ti ₁₇ O ₄₀ crystal 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. is. By setting the Ba ₆ Ti ₁₇ O ₄₀ crystal particles to 1.0% by mass or more, the effect of the presence of the Ba ₆ Ti ₁₇ O ₄₀ crystal particles (that is, the effect of lowering the electrical resistance at room temperature) can be obtained. Also, by setting the Ba ₆ Ti ₁₇ O ₄₀ crystal particles to 10.0% by mass or less, the PTC characteristics can be ensured.

The ceramic body according to the embodiment of the present invention can further contain BaCO ₃ crystal grains. BaCO ₃ crystal particles are crystal particles derived from BaCO ₃ powder, which is the raw material of the ceramic body.
BaCO ₃ crystal grains do not need to be contained in the ceramic body because they have little effect on the electrical resistance of the ceramic body at room temperature. However, if the content of BaCO ₃ crystal grains in the ceramic body is too large, the electrical resistance at room temperature may be affected, and the other crystal grains may become too small to obtain desired characteristics. Therefore, the content of BaCO ₃ crystal particles in the ceramic body is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.5% by mass or less. Although the lower limit of the content of BaCO ₃ crystal particles is not particularly limited, it is generally 0.1% by mass, preferably 0.2% by mass.

The ceramic body according to the embodiment of the present invention may further contain, in addition to the above-described crystal grains, components commonly added to PTC materials. Such components include additives such as shifters, property modifiers, metal oxides and conductor powders, as well as unavoidable impurities.

It is desirable that the ceramic body according to the embodiment of the present invention does not substantially contain lead (Pb) from the viewpoint of reducing environmental load. Specifically, the ceramic body according to the embodiment of the present invention preferably has a Pb content of 0.01% by mass or less, more preferably 0.001% by mass or less, and even more preferably 0% by mass. With a low Pb content, for example, when a ceramic body is used as a heater element, air heated by contacting the ceramic body can be safely applied to living organisms such as humans. In addition, in the ceramic body according to the embodiment of the present invention, the Pb content is preferably less than 0.03% by mass, more preferably less than 0.01% by mass, and still more preferably 0% by mass in terms of PbO. . The lead content can be determined by, for example, fluorescent X-ray analysis, ICP-MS (inductively coupled plasma mass spectrometry), or the like.

Preferably, the ceramic body according to the embodiment of the present invention does not substantially contain alkali metals that may affect electrical resistance at room temperature. Specifically, the ceramic body according to the embodiment of the present invention has an alkali metal content of 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 alkali metal content within such a range, the electrical resistance at room temperature can be stably lowered. The alkali metal content can be determined by, for example, fluorescent X-ray analysis, ICP-MS (inductively coupled plasma mass spectrometry), or the like.

(1-2) Open Porosity The open porosity of the ceramic body according to the embodiment of the present invention is a factor that affects 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 lowered. Although the lower limit of the open porosity is not particularly limited, it 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 the pore-forming material and sintering aid used when producing the ceramic body, and the firing atmosphere.

(1-3) Bulk Density The bulk density of the ceramic body according to the embodiment of the present invention is a factor that affects 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 higher. By controlling the bulk density within such a range, the electrical resistance at room temperature can be stably lowered. Although the upper limit of bulk density is not particularly limited, it 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, like the open porosity. The bulk density can be controlled by adjusting the amount of the dispersion medium, binder, plasticizer, dispersant, etc. used when producing the ceramic body, and the conditions such as the firing atmosphere.

(1-4) Volume Resistivity The ceramic body according to the embodiment of the present invention has a volume resistivity measured at 25° C. of preferably 150 Ω·cm or less, more preferably 100 Ω·cm or less, and even more preferably 50 Ω·cm. cm, particularly preferably 30 Ω·cm or less. 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 necessary for heating and to suppress the increase in power consumption. Although the lower limit of the volume resistivity is not particularly limited, it is generally 0.1 Ω·cm, preferably 1.0 Ω·cm.
The volume resistivity of a 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-probe method, and the volume resistivity is calculated from the shape of the test piece. Let the average value of the volume resistivity of all test pieces be the measured value at the measurement temperature.

(1-5) Applications The ceramic bodies according to the embodiments of the present invention can be used for, but not limited to, PTC heaters, PTC switches, overcurrent protection elements, and temperature detectors. Among these, the ceramic body according to the embodiment of the present invention can be suitably used as a heater element for heating, particularly as a heater element for heating the cabin of a vehicle. Vehicles include, but are not limited to, automobiles and trains. Vehicles include, but are not limited to, gasoline vehicles, diesel vehicles, fuel cell vehicles, electric vehicles, and plug-in hybrid vehicles. Heater elements according to embodiments of the present invention are particularly suitable for use in vehicles without internal combustion engines, such as electric vehicles and electric trains.

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

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 honeycomb shape. A honeycomb structure 10 according to an embodiment of the present invention includes an outer peripheral wall 11 and a plurality of cells 14 disposed inside the outer peripheral wall 11 and forming flow paths from a first end surface 13a to a second end surface 13b. It has a honeycomb shape including partition walls 12 that are connected to each other.

The shape of each end face (first end face 13a and second end face 13b) of the honeycomb structure 10 is not particularly limited, but may be polygonal (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), It can be of any shape, such as circular, oval, or L-shaped. If each end face is polygonal, the corners may be chamfered. It is preferable that the shape of each end surface and the shape of the cross section perpendicular to the direction in which the cells 14 extend are the same.

Although the shape of the cells 14 in a cross section perpendicular to the direction in which the cells 14 extend is not limited, it is preferably quadrangular (rectangular, square), hexagonal, octagonal, or a combination of two or more of these. Among these, the shape of the cells 14 is preferably square and/or hexagonal. By forming the cells 14 in such a shape, the pressure loss when the gas is caused to flow through the honeycomb structure 10 can be reduced. Note that the honeycomb structure 10 of FIG. 1 shows a case where the shape of the cells 14 in the cross section perpendicular to the extending direction of the cells 14 is square.

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, still more preferably 60 to 110 μm. By setting the average thickness of the partition walls 12 to 50 μm or more, the strength of the honeycomb structure 10 can be ensured while reducing the electrical resistance at room temperature. Moreover, 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 a line segment that crosses the partition wall 12 when connecting the centers of gravity of adjacent cells 14 in a cross section perpendicular to the direction in which the cells 14 extend. The average thickness of the partition walls 12 refers to the average thickness of all the partition walls 12 .

Although the cell density is not particularly limited, it is preferably 15-140 cells/cm ² , more preferably 46-94 cells/cm ² . By setting the cell density to 15 cells/cm ² or more, the honeycomb structure 10 suitable for heating can be obtained while reducing the electrical resistance at room temperature. Also, by setting the cell density to 140 cells/cm ² or less, the ventilation resistance can be suppressed and the output of the blower can be suppressed.
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 .

The honeycomb structure 10 shown in FIG. 1 can be used as a heater element, and can generate heat when energized. Therefore, the gas, such as outside air or vehicle interior air, flows from the first end surface 13a, passes through the plurality of cells 14, and flows out from the second end surface 13b. It is possible to heat by heat transfer.

The ceramic body according to the embodiment of the present invention may be a joined honeycomb body having honeycomb segments and joining layers for joining between the plurality of honeycomb segments. By using the honeycomb bonded body, it is possible to increase the total cross-sectional area of the cells 14, which is important for securing the gas flow rate, while suppressing the occurrence of cracks.

Here, as an example, FIG. 2 shows a schematic cross-sectional view perpendicular to the cell extending direction of a honeycomb joined body having five honeycomb segments.
As shown in FIG. 2 , the honeycomb joined body 17 has five honeycomb segments 18 and joining layers 19 that join between the honeycomb segments 18 . Each honeycomb segment 18 has an outer peripheral wall 11 and a partition wall 12 disposed inside the outer peripheral wall 11 and partitioning a plurality of cells 14 forming flow paths from the first end face 13a to the second end face 13b.

The bonding layer 19 can be formed using a bonding material. The bonding material is not particularly limited, but a paste made by adding a solvent such as water to a ceramic material can be used. The bonding material may contain ceramics having PTC properties, or may contain the same ceramics as the outer peripheral wall 11 and the partition walls 12 . In addition to the role of joining the honeycomb segments 18 together, the joining material can also be used as an outer peripheral coating material after the honeycomb segments 18 are joined.

(1-7) Manufacturing Method A method for manufacturing a ceramic body according to an embodiment of the present invention includes a forming step and a firing step. In addition, below, the case where the ceramics body (honeycomb structure 10) which has a honeycomb shape is manufactured is mentioned as an example, and is demonstrated.
In the molding step, a clay containing ceramic raw materials containing BaCO ₃ powder, TiO ₂ powder, and rare earth nitrate and/or hydroxide powder is molded to form a ceramic compact having a relative density of 60% or more. (hereinafter sometimes referred to as a "honeycomb molded body"). In particular, by using a rare earth hydroxide powder as a ceramic raw material, it is possible to suppress the aggregation of the BaCO ₃ powder in the clay, so that uniform liquid phase formation and grain growth can be promoted in the firing process. can. 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, preferably La.
A ceramic raw material can be obtained by dry-mixing powders to obtain a desired composition.
Clay can be obtained by adding a dispersion medium, a binder, a plasticizer and a dispersant to a ceramic raw material and kneading the mixture. Additives such as shifters, metal oxides, property improving agents, and conductive powders may be added to the clay, if necessary.
The amount of the components other than the ceramic raw material is not particularly limited as long as the relative density of the ceramic compact is 60%.

Here, the term "relative density of the ceramic compact" as used herein means the ratio of the density of the ceramic compact to the true density of the ceramic raw material as a whole. Specifically, it can be obtained by the following formula.
Relative density of ceramic compact (%) = Density of ceramic compact (g/cm ³ )/true density of entire ceramic raw material (g/cm ³ ) x 100
The density of the ceramic compact can be measured by the Archimedes method using pure water as a medium. Further, the true density of the entire ceramic raw material can be obtained by dividing the total mass value (g) of each raw material by the total actual volume value (cm ³ ) of each raw material.

Examples of the dispersion medium include water, a mixed solvent of water and an organic solvent such as alcohol, and the like, and water is particularly preferable.

Examples of binders include organic binders such as methylcellulose, hydroxypropoxylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. In particular, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose together. The binder may be used singly or in combination of two or more, but preferably does not contain an alkali metal element.

Examples of plasticizers include polyoxyalkylene alkyl ethers, polycarboxylic acid polymers, and alkyl phosphate esters.

Surfactants such as polyoxyalkylene alkyl ethers, ethylene glycol, dextrin, fatty acid soaps, and polyalcohols can be used as dispersants. Dispersants may be used singly or in combination of two or more.

A ceramic molded body can be produced by extruding clay. For extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

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 compact within such a range, it becomes possible to densify the ceramic compact and reduce the electrical resistance at room temperature. Although the upper limit of the relative density of the ceramic compact is not particularly limited, it is generally 80%, preferably 75%.

The ceramic molded body can be dried before the firing process. The drying method is not particularly limited, but conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying can be used. Among these, a drying method combining hot air drying with microwave drying or dielectric drying is preferable in that the entire molded body can be dried quickly and uniformly.

The firing step includes holding at 1150 to 1250° C., raising the temperature to a maximum temperature of 1360 to 1430° C. at a rate of 20 to 500° C./hour, and holding the temperature for 0.5 to 5 hours.
By holding the honeycomb formed body at a maximum temperature of 1360 to 1430° C. for 0.5 to ₅ hours, a ceramic body (honeycomb structure 10) can be obtained.
Also, by holding at 1150 to 1250° C., the Ba ₂ TiO ₄ crystal particles generated during the firing process are easily removed, so the honeycomb structure 10 can be densified.
Furthermore, by setting the rate of temperature increase from 1150 to 1250° C. to the maximum temperature of 1360 to 1430° C. to 20 to 500° C./hour, 1.0 to 10.0% by mass of Ba ₆ Ti ₁₇ O ₄₀ crystal particles are obtained. The honeycomb structure 10 can be generated.

The holding time at 1150 to 1250° C. is not particularly limited, but preferably 0.5 to 5 hours. By setting such a holding time, the Ba ₂ TiO ₄ crystal particles generated during the firing process can be stably removed easily.

The firing step preferably includes holding at 900-950° C. for 0.5-5 hours. By holding at 900 to 950° C. for 0.5 to 5 hours, BaCO ₃ is efficiently decomposed, making it easier to obtain a honeycomb structure 10 having a predetermined composition.

A degreasing step for removing the binder may be performed before the firing step. The atmosphere of the degreasing step is preferably an air atmosphere in order to completely decompose the organic components.
Also, the atmosphere in the firing process is preferably an air atmosphere from the viewpoint of control of electrical properties and manufacturing cost.
A firing furnace used in the firing process and the degreasing process is not particularly limited, but an electric furnace, a gas furnace, or the like can be used.

<Heater element>
A heater element according to an embodiment of the present invention includes the ceramic body (for example, the honeycomb structure 10).
3 is a schematic perspective view of a heater element according to an embodiment of the invention; FIG. 4 is a schematic cross-sectional view of the heater element of FIG. 3 orthogonal to the cell extending direction of the honeycomb structure.
A heater element 100 according to an embodiment of the present invention includes a honeycomb structure 10 and a pair of electrodes 20 arranged on the surface of the outer peripheral wall 11 of the honeycomb structure 10 .

The honeycomb structure 10 used for the heater element 100 preferably has a shape having a long axis and a short axis in a cross section perpendicular to the extending direction of the cells 14 . Moreover, the pair of electrodes 20 are formed in a band shape extending parallel to the direction in which the cells 14 extend, and are opposed to each other across the long axis passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the direction in which the cells 14 extend. It is preferable that it is arranged on the surface of the outer peripheral wall 11 so as to do so. Furthermore, the heater element 100 preferably further includes a plate-shaped external connection member 30 that is arranged on the end side of each electrode 20 and that is in contact with each electrode 20 in a plane. By arranging the electrodes 20 and the external connection members 30 in this way, the electrodes 20 and the external connection members 30 are in surface contact, and the amount of power supplied from the outside can be easily increased, so that the heat generation performance can be improved.

FIG. 5 is a schematic end view of another heater element according to an embodiment of the present invention (that is, a schematic front view of another heater element according to an embodiment of the present invention viewed from the first end face side of the honeycomb structure). Figure). 6 is a schematic cross-sectional view of the heater element of FIG. 5 taken along line aa' (that is, 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). be.
The heater element 200 according to the 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 on the first end surface 13a and the second end surface 13b of the honeycomb structure 10. and

The honeycomb structure 10 used for the heater element 200 preferably has a short length in the direction in which the cells 14 extend. With such a structure, the honeycomb structure 10 having a low electrical resistance at room temperature can be applied even to the heater element 200 having a structure in which the pair of electrodes 20 are arranged on the first end surface 13a and the second end surface 13b. It becomes possible. Moreover, the heater element 200 preferably further includes a plate-like external connection member 30 that is in contact with each electrode 20 in a plane at least part of the pair of electrodes 20 . By providing such an external connection member 30, it is possible to efficiently conduct electricity to the entire pair of electrodes 20, thereby improving heat generation performance.
Each constituent member of the heater elements 100 and 200 will be described in detail below.

(2-1) Pair of electrodes 20 in heater element 100
A 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 band shape extending parallel to the direction in which the cells 14 of the honeycomb structure 10 extend. Also, the pair of electrodes 20 are arranged on the surface of the outer peripheral wall 11 so as to face each other across the long axis passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the direction in which the cells 14 of the honeycomb structure 10 extend. be. By applying a voltage through the pair of electrodes 20 arranged in this way, it becomes possible to generate heat in the honeycomb structure 10 by Joule heat.

Although 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 ohmic contact with the outer peripheral wall 11 and/or the partition wall 12 having PTC characteristics may 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 n-type semiconductors as a dopant. An ohmic electrode layer containing one can be used. Further, the electrode 20 may have one 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 of different types.

The thickness of the electrode 20 is not particularly limited, and can be appropriately set according to the method of forming the electrode 20 . Methods of forming the electrode 20 include metal deposition methods such as sputtering, vapor deposition, electrolytic deposition, and chemical deposition. Alternatively, the electrode 20 can be formed by applying an electrode paste and then baking it. Furthermore, the electrodes 20 can also be formed by thermal spraying.
The thickness of the electrode 20 is about 5 to 30 μm for baking electrode paste, about 100 to 1000 nm for dry plating such as sputtering and vapor deposition, about 10 to 100 μm for thermal spraying, and about 5 μm for wet plating such as electrolytic deposition and chemical deposition. It is preferable to set the thickness to about 30 μm.

(2-2) Pair of electrodes 20 in heater element 200
The pair of electrodes 20 can be provided on the surfaces of the outer peripheral wall 11 and the partition walls 12 on the first end surface 13 a and the second end surface 13 b 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 blocking the cell 14, and more preferably provided on the entire first end face 13a and the second end face 13b without blocking the cell 14. .
Other features of the electrode 20 are the same as in (2-1), so the description is omitted.

(2-3) External connection member 30 in 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 long axis passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the extending direction of the cells 14 of the honeycomb structure 10 . By providing such a plate-shaped external connection member 30, it becomes easier to increase the amount of power supplied to the electrode 20 from the outside, so that the heat generation performance can be improved.
Here, in the present specification, “the end portion side of each electrode 20” means that each electrode is positioned in the longitudinal direction passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the direction in which the cells 14 of the honeycomb structure 10 extend. It means the area from the end of 20 to 30% of the total length of each electrode 20 .
The external connection member 30 may be arranged on the end portion side of each electrode 20 and does not necessarily have to be in contact with the end portion 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 .

The external connection member 30 preferably has substantially the same width as the end portion of the electrode 20 on which the external connection member 30 is arranged. With such a configuration, the contact area between the electrode 20 and the external connection member 30 is increased, so that the effect of improving the heat generation performance is enhanced.
Here, in this specification, "a width substantially equal to the width of the end of the electrode 20" means within ±20% of the width of the end of the electrode 20. FIG.

Each of the external connection members 30 is preferably arranged on one end side of the electrode 20 parallel to the direction in which the cells 14 of the honeycomb structure 10 extend. One end side where the external connection member 30 is disposed may be the same side or different side in a cross section perpendicular to the extending direction of the cells 14 of the honeycomb structure 10 . One end side is more preferably the same side. It is preferable that each of the external connection members 30 extends outward in the same direction from its end side. With such a configuration, when the honeycomb structure 10 is applied to the heater element 100, the heater element 100 can be made compact.

The material of the external connection member 30 is not particularly limited, but can be metal, for example. As the metal, a single metal, an alloy, or the like can be employed, but from the viewpoint of corrosion resistance, electrical resistivity, and coefficient of linear expansion, for example, it is selected from the group consisting of Cr, Fe, Co, Ni, Cu, and Ti. An alloy containing at least one of them is preferable, 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.

The method of connecting the external connection member 30 and the electrode 20 is not particularly limited as long as they are electrically connected, and can be connected by, for example, diffusion bonding, mechanical pressure mechanism, welding, or the like.

(2-4) External connection member 30 in heater element 200
The external connection member 30 is plate-shaped and can be provided so as to be in contact with each electrode 20 in a plane.
The external connection member 30 is preferably arranged on the electrodes 20 provided on the outer peripheral wall 11 of the first end surface 13a and the second end surface 13b. With such a configuration, the entire electrode 20 can be efficiently energized.
Other features of the external connection member 30 are the same as in (2-3), so the description is omitted.

(2-5) Usage The heater elements 100 and 200 according to the embodiments of the present invention can be suitably used as heater elements for heating the cabin of a vehicle.
The heater elements 100 and 200 according to the embodiment of the present invention can generate heat by applying a voltage from an external power supply to the honeycomb structure 10 through the external connection members 30 and the electrodes 20 . The applied voltage is preferably 12 to 800V. Specifically, in the heater element 100, the applied voltage is preferably 100-800V. Moreover, in the heater element 200, the applied voltage is preferably 12 to 60V. By adjusting the applied voltage within this range, power consumption can be suppressed while performing rapid heating. Also, since the voltage is low, the safety is high. Furthermore, since the safety specifications are not heavy, the equipment around the heater can be manufactured at low cost.

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

Since the heater element 100 according to the embodiment of the present invention uses the honeycomb structure 10 having PTC characteristics and low electrical resistance at room temperature, it can be driven at a low voltage.
Moreover, the heater element 100 according to the embodiment of the present invention has a simpler structure than the existing heater element in which the PTC element and the aluminum fins are integrated via the insulating ceramic plate, and the heater unit is increased in size. can be suppressed. In addition, in the existing heater element, the PTC element does not come into direct contact with the gas, so the rate of temperature increase (heating time) of the gas is not sufficient. Since the honeycomb structure 10, in which the honeycomb structure 12 is made of a material having PTC properties, is in direct contact with the gas, the rate of temperature rise of the gas can be increased.
Furthermore, in the heater element 100 according to the embodiment of the present invention, by arranging the electrodes 20 and the external connection members 30 as described above, it becomes easier to increase the amount of power supplied to the electrodes 20 from the outside, thereby improving the heat generation performance. can be made

<Heater unit>
INDUSTRIAL APPLICABILITY A heater unit according to an embodiment of the present invention can be suitably used as a heater unit for heating a passenger compartment of a vehicle. In particular, since the heater unit according to the embodiment of the present invention uses a ceramic body (honeycomb structure 10) having PTC characteristics and low electrical resistance at room temperature for the heater elements 100 and 200, it can be driven at a low voltage. can be done. 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. Moreover, since the heater unit according to the embodiment of the present invention uses the 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 also possible to suppress an increase in the size of the heater unit.

FIG. 7 is a schematic front view of the heater unit according to the embodiment of the present invention viewed from the first end face side of the honeycomb structure.
As shown in FIG. 7, a heater unit 600 according to an embodiment of the invention includes two or more heater elements 100. As shown in FIG. Moreover, 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 surface 13a and the second end surface 13b, face each other. With such a configuration, a compact heater unit 600 can be manufactured.

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 thereof include metal and resin. Among them, it is preferable that the material of the housing 610 is resin. By using the housing 610 made of resin, electric shock can be suppressed 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.

The heater unit 600 according to an embodiment of the present invention may further include an insulating material 620 disposed between the stacked heater elements 100 . With such a configuration, electrical shorts between the plurality of heater elements 100 can be suppressed.
As the insulating material 620, a plate, mat, or cloth made of an insulating material such as alumina or ceramics can be used.

A heater unit 600 according to an embodiment of the present invention may have a wiring structure capable of controlling the heater element 100 . Specifically, the heater unit 600 according to the embodiment of the present invention may further include 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, a wiring structure in which each of the heater elements 100 can be independently controlled can be used. 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 supply (not shown). With such a wiring structure, each of the heater elements 100 can be controlled independently, so fine temperature adjustment is possible.

The wiring structure may be a parallel wiring structure capable of collectively controlling two or more heater elements 100, as shown in FIG. Specifically, one external connection member 30 of each heater element 100 is connected to the parallel wiring 640a, and the other external connection member 30 is connected to one parallel wiring 640b. With such a wiring structure, the power consumption of the heater unit 700 can be suppressed.

Further, as shown in FIG. 9, the electrodes 20 between the heater elements 100 arranged in layers are made into one electrode 20 common to the heater elements 100 arranged in layers, and two or more heater elements 100 are integrated. A parallel wiring structure that can be controlled by Specifically, the external connection member 30 is arranged at the end of the electrode 20, the parallel wiring 640a is connected to one external connection member 30 of each heater element 100, and one parallel wiring is connected to the other external connection member 30 of each heater element 100. 640b should be connected. With such a structure, the insulating material 620 does not have to be arranged between the heater elements 100 arranged in layers, so that the heater unit 800 can be made compact and power consumption can be reduced.

<Heater system>
INDUSTRIAL APPLICABILITY A heater system according to an embodiment of the present invention can be suitably used as a heater system for heating the cabin of a vehicle. In particular, since the heater system according to the embodiment of the present invention uses the heater unit 600 that can be driven at a low voltage, power consumption can be suppressed. In addition, since the heater system according to the embodiment of the present invention uses the heater unit 600 with high heat generation performance, 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 increase in size of the heater system.

FIG. 10 is a schematic diagram showing a configuration example of a heater system according to an embodiment of the present invention.
As shown in FIG. 10, the heater system 900 according to the embodiment of the present invention communicates the heater unit 600 according to the embodiment of the present invention, the outside air introduction part or the vehicle compartment 910, and the inlet 650 of the heater unit 600. Inflow pipes 920 a and 920 b , a battery 940 for applying voltage to the heater unit 600 , and an outflow pipe 930 connecting an outlet 660 of the heater unit 600 and the vehicle compartment 910 are provided. It is also possible to use the heater units 700 and 800 according to the embodiment of the present invention instead of the heater unit 600. FIG.

The heater unit 600 can be configured, for example, to be connected to the battery 940 by an electric wire 950 and turn on a power switch on the way to energize the heater unit 600 to generate heat.

A vapor compression heat pump 960 may be installed upstream of the heater unit 600 . In heater system 900, vapor compression heat pump 960 is configured as a main heating device, and heater unit 600 is configured as an auxiliary heater. The vapor compression heat pump 960 includes an evaporator 961 that absorbs heat from the outside and evaporates the refrigerant during cooling, and a condenser 962 that liquefies the refrigerant gas and releases heat during heating. An exchanger can be provided. Note that the vapor compression heat pump 960 is not particularly limited, and one known in the art can be used.

A blower 970 can be installed upstream and/or downstream of the heater unit 600 . From the viewpoint of ensuring safety by arranging high-voltage components as far away from the compartment 910 as possible, it is preferable to install the blower 970 upstream of the heater unit 600 . When the blower 970 is driven, air flows into the heater unit 600 from inside or outside the vehicle compartment 910 through the inflow pipes 920a and 920b. The air is heated while passing through the heat generating heater unit 600 . The heated air flows out of heater unit 600 and is sent into vehicle interior 910 through outflow pipe 930 . The outlet of the outflow pipe 930 may be arranged near the feet of the occupant so that the heating effect is particularly high even in the passenger compartment 910, or the pipe outlet may be arranged in the seat to heat the seat from the inside. Alternatively, it may be arranged in the vicinity of the window to have the effect of suppressing fogging of the window.

The inflow pipe 920a and the inflow pipe 920b join in the middle. Valves 921a and 921b can be installed in the inflow pipe 920a and the inflow pipe 920b, respectively, on the upstream side of the junction. By controlling the opening and closing of the valves 921 a and 921 b , it is possible to switch between a mode in which the outside air is introduced into the heater unit 600 and a mode in which the air inside the passenger compartment 910 is introduced into the heater unit 600 . For example, when the valve 921a is opened and the valve 921b is closed, a mode of introducing outside air into the heater unit 600 is entered. It is also possible to open both the valve 921a and the valve 921b to introduce the outside air and the air inside the vehicle interior 910 into the heater unit 600 at the same time.

<Purification system>
The purifying system according to the embodiment of the present invention can also be suitably used as a purifying system for removing harmful components in the interior of a vehicle. In particular, the purification system according to the embodiment of the present invention uses a heater element using a ceramic body with low electrical resistance at room temperature, or a heater unit including two or more heater elements, so that power consumption is suppressed and purification performance is improved. Obtainable.
The heater element used in the purification system according to the embodiment of the present invention includes the ceramic body (honeycomb structure 10), the adsorbent provided on the surface of the partition walls 12 of the honeycomb structure 10, and the honeycomb structure 10. It has a pair of electrodes 20 provided on the first end surface 13a and the second end surface 13b.

Here, FIG. 11 shows a schematic enlarged cross-sectional view perpendicular to the extending direction of the cells 14 of the honeycomb structure 10 provided with the adsorbent.
As shown in FIG. 11 , an adsorbent 50 is provided on the surfaces of the partition walls 12 of the honeycomb structure 10 . By providing the adsorbent 50 in this manner, harmful volatile components can be adsorbed from the air flowing through the cell 14 . Harmful volatile components are, for example, volatile organic compounds (VOC) and odor components. 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, and di-2 phthalate. -ethylhexyl, diazinon, acetaldehyde, 2-(1-methylpropyl)phenyl N-methylcarbamate.
The adsorbent 50 may be appropriately selected depending on the volatile component to be adsorbed, and is not particularly limited. Examples of the adsorbent 50 include zeolite and the like. Also, if an adsorbent 50 capable of adsorbing CO ₂ at room temperature and desorbing CO ₂ at high temperature is selected, CO ₂ in the vehicle interior can be discharged to the outside of the vehicle. Furthermore, by using the adsorbent 50 in combination with a noble metal such as Pt or a metal oxide oxidation catalyst, it becomes easier to remove harmful volatile components from the air flowing through the cell 14 .

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

A heater element used in the purification system according to the embodiment of the present invention can be manufactured according to the method described above. For example, an electrode paste is applied to the first end surface 13a and the second end surface 13b of the honeycomb structure 10 and baked to form the electrodes 20, and then the surfaces of the partition walls 12 are coated with the adsorbent 50 to produce the heater element. be able to. The method of coating the adsorbent 50 is not particularly limited, but for example, the honeycomb structure 10 is immersed in a slurry containing the adsorbent 50, an organic binder, and water, and excess slurry on the end faces and outer periphery of the honeycomb structure 10 is blown off. and remove by wiping. Thereafter, the adsorbent 50 can be provided on the surface of the partition wall 12 by drying at a temperature of about 550.degree. This step may be performed once, but a desired amount of the adsorbent 50 can be provided on the surface of the partition walls 12 by repeating this step multiple times.
Moreover, when the external connection member 30 is provided, the external connection member 30 may be arranged at a predetermined position of the electrode 20 and joined.

FIG. 12 is a schematic diagram showing a configuration example of a purification system according to an embodiment of the present invention.
As shown in FIG. 12, a purification system 1000 according to an embodiment of the present invention includes the heater element or heater unit 1100 described above and a battery ( power source) 1200, an inflow pipe 1300 communicating between the vehicle compartment and the inflow port 1110 of the heater element or heater unit 1100, an outflow pipe 1400 communicating with the outflow port 1120 of the heater element or heater unit 1100, the vehicle compartment and the outside of the vehicle, and an outflow A switching valve 1500 is provided in the pipe 1400 and is capable of switching the flow of air flowing through the outflow pipe 1400 between the vehicle interior and the vehicle exterior.

The heater element or heater unit 1100 can be configured, for example, to be connected to the battery 1200 by an electric wire 1210 and turn on a power switch on the way to energize the heater element or heater unit 1100 to generate heat.
ON and OFF switching of the power switch can be performed by the control unit 1600 electrically connected to the power switch. Switching of the switching valve 1500 can also be performed by the control unit 1600 electrically connected to the switching valve.

In the purification system 1000 having the structure described above, air from the passenger compartment is supplied to the heater element or heater unit 1100 from the inlet 1110 through the inlet pipe 1300 . After being subjected to a predetermined treatment in the heater element or heater unit 1100, the air is discharged from the outlet 1120 and returned to the passenger compartment through the outlet pipe 1400 or discharged to the outside of the vehicle.
When closing the flow path of the outflow pipe 1400 to the outside of the vehicle with the switching valve 1500 so that the air returns to the vehicle interior, the power switch is turned off to keep the heater element or the heater unit 1100 at room temperature. By controlling in this manner, the harmful volatile components contained in the air from the passenger compartment can be removed by being adsorbed by the heater element or the adsorbent 50 of the heater unit 1100 .
On the other hand, when the flow path of the outflow pipe 1400 to the vehicle compartment is closed by the switching valve 1500 so that the air is discharged outside the vehicle, the power switch is turned on to heat the heater element or the heater unit 1100 . By controlling in this manner, the harmful volatile components adsorbed by the adsorbent 50 of the heater element or heater unit 1100 are desorbed, the function of the adsorbent 50 is restored, and the harmful volatile components are discharged outside the vehicle. can be done.
By repeating the switching of the power switch and switching valve 1500 as described above in a constant cycle, it is possible to stably discharge harmful volatile components in the vehicle interior to the outside of the vehicle.

In the purification system 1000, the heater element or the heater unit 1100 is desirably arranged at a position close to the passenger compartment from the viewpoint of stably ensuring the above functions. Therefore, it is preferable that the drive voltage is 60 V or less from the viewpoint of electric shock prevention. Since the honeycomb structure 10 used in the heater element or heater unit 1100 has a low electric resistance at room temperature, the honeycomb structure 10 can be heated with this low drive voltage. Although the lower limit of the drive voltage is not particularly limited, it is preferably 10V. If the driving voltage is less than 10 V, the current during heating of the honeycomb structure 10 becomes large, so the wire 1210 must be thick.

In the honeycomb structure 10 used in the heater element or heater unit 1100, a large amount of the adsorbent 50 is provided on the surface of the partition wall 12, and from the viewpoint of sufficiently securing the adsorption function, the opening ratio of the cells 14, the cell density and It is preferable that the partition walls 12 have a large surface area. In a typical embodiment, the honeycomb structure 10 preferably has an open area ratio of the cells 14 of 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 . Furthermore, the minor axis diameter (the thickness of the honeycomb structure 10) in a cross section perpendicular to the extending direction of the cells 14 is preferably 3 to 15 mm, more preferably 4 to 10 mm.

If the short axis diameter (the thickness of the honeycomb structure 10) in the cross section perpendicular to the extending direction of the cells 14 is small, the amount of the adsorbent 50 may be insufficient. A heater unit is preferably used in the purification system 1000 . The heater unit can be produced by arranging a plurality of heater elements in parallel as described above. 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 utility of the purification system 1000 can be enhanced.

From the viewpoint 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 not be too large. This is because if the adsorbent 50 is too thick, it will be difficult for it to come into contact with the air flowing through the cells 14, and the efficiency of the adsorption function will decrease. Therefore, the thickness of the adsorbent 50 is preferably 0.01-0.5 mm.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(1) Preparation of ceramic body <Examples 1 to 9, Comparative Examples 1 to 4>
BaCO ₃ powder, TiO ₂ powder and La(NO ₃ ) _{3.6H 2} O powder were prepared as ceramic raw materials. These powders were weighed so as to have the composition shown in Table 1 after sintering, and were dry-mixed to obtain a mixed powder. Dry mixing was performed for 30 minutes. Then, 3 to 30 parts by weight of water, a binder, a plasticizer and a dispersant in total are added to 100 parts by weight of the mixed powder so that a ceramic compact having a relative density shown in Table 1 is obtained after extrusion molding. and kneaded to obtain a kneaded clay. Methyl cellulose was used as a binder. A polyoxyalkylene alkyl ether was used as a plasticizer and dispersant.
This kneaded material was put into an extruder and extruded using a predetermined die to obtain a rectangular parallelepiped honeycomb molded body. Then, the density of the formed honeycomb body was measured according to the above method.
Next, after dielectric drying and hot air drying of the resulting formed honeycomb body, both bottom surfaces were cut to obtain a dried honeycomb body having predetermined dimensions.

The shape of the dried honeycomb body is as follows.
Overall shape: 45 mm × 45 mm × height (cell extending direction) 200 mm rectangular parallelepiped shape Cell shape in cross section orthogonal to cell extending direction: square Cell density: 62 cells/cm ²
Partition wall thickness: 4 mil (101.6 μm)

Next, after cutting the dried honeycomb body to a height of 35 mm, it is degreased in an air atmosphere in a firing furnace (450° C.×4 hours), and then fired in an air atmosphere to obtain ceramics. got a 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 the holding step C is a holding step at the maximum temperature.
The obtained ceramic body was evaluated as follows.

<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(NO ₃ ) ₃ .6H ₂ O powder, and the following evaluations were performed.

(2) Chemical Analysis The chemical composition of the ceramic body was analyzed by ICP emission spectroscopy, and the atomic ratios of elements such as La, Ba and Ti were obtained. Table 1 shows the La atomic ratio (x value) and the (Ba+La)/Ti ratio of the BaTiO ₃ -based crystal particles obtained by this analysis. Also, from the analysis results, it was confirmed that the ceramic bodies produced in Examples and Comparative Examples did not contain Pb and alkali metals.

(3) Identification of Crystal Particles and Lattice Volume of BaTiO ₃ Based Crystal Particles Crystal particles of the ceramic body were identified using an X-ray diffractometer. As the X-ray diffractometer, a multifunctional powder X-ray diffractometer (D8 Advance, manufactured by Bruker) was used. The conditions for the X-ray diffraction measurement were CuKα radiation source, 10 kV, 20 mA, and 2θ=5 to 100°. Crystal grains were identified by analyzing the obtained X-ray diffraction data according to the Rietveld method using analysis software TOPAS (manufactured by BrukerAXS).
The lattice volume of the BaTiO ₃ -based crystal particles was obtained by calculation from the lattice constant obtained by analyzing the X-ray diffraction data.
These results are shown in Table 1.

(4) Content of Each Crystal Particle The content of each crystal particle was measured using an X-ray diffractometer. Using the same X-ray diffractometer and analysis software as above, the content of each crystal grain was obtained by the Rietveld method.

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

(6) Open porosity The open porosity of the ceramic body was measured according to the method described above. Table 1 shows the results.

(7) Bulk Density The bulk density of the ceramic body was measured according to the method described above. Table 1 shows the results.

(8) Volume resistivity The volume resistivity of the ceramic body at room temperature (25°C) was measured according to the method described above. In addition, the measured value of volume resistivity was made into the average value of the measured volume resistivity. Table 1 shows the results.

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

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

REFERENCE SIGNS LIST 10 honeycomb structure 11 outer wall 12 partition wall 13a first end face 13b second end face 14 cell 17 honeycomb bonded body 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 cabin 920a, 920b, 1300 inlet piping 921a, 921b valve 930, 1400 outlet piping 940, 1200 battery 950, 1210 electric wire 960 steam 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 (24)

A ceramic body containing, as a main component, BaTiO ₃ -based crystal particles in which a part of Ba is replaced with a rare earth element, and Ba ₆ Ti ₁₇ O ₄₀ crystal particles in an amount of 1.0 to 10.0% by mass. The composition formula of the BaTiO ₃ -based crystal particles is represented by (Ba _1-x A _x )TiO ₃ (wherein A represents one or more rare earth elements, and 0.001≦x≦0.010). The ceramic body according to claim 1, wherein the ceramic body is 3. The ceramic body according to claim 1, wherein the BaTiO ₃ -based crystal particles have a (Ba+rare earth element)/Ti ratio of 1.005 to 1.050. 4. The ceramic body according to claim 2, wherein A is La. The ceramic body according to any one of claims 1 to 4, wherein the BaTiO ₃ -based crystal grains have a lattice volume of 64.4000 to 64.3650 Å ³ . 6. The ceramic body according to claim 1, wherein said BaTiO ₃ -based crystal particles have an average crystal grain size of 5 to 200 μm. 7. The ceramic body according to claim 1, which has an open porosity of 5.0% or less. 8. The ceramic body according to claim 1, which has a bulk density of 5.35 g/cm ³ or more. The ceramic body according to any one of claims 1 to 8, which contains BaCO ₃ crystal particles in an amount of 2.0% by mass or less. The ceramic body according to any one of claims 1 to 9, which has a Pb content of 0.01% by mass or less. The ceramic body according to any one of claims 1 to 10, wherein the alkali metal content is 0.01% by mass or less. The ceramic body according to any one of claims 1 to 11, which has a volume resistivity of 150 Ω·cm or less measured at 25°C. 13. The ceramic body according to claim 12, wherein said volume resistivity is 30 Ω·cm or less. 14. Any one of claims 1 to 13, having a honeycomb shape including an outer peripheral wall and a partition wall disposed inside the outer peripheral wall and partitioning and forming a plurality of cells forming a flow path from a first end surface to a second end surface. or the ceramic body according to item 1. 15. The ceramic body according to claim 14, wherein the partition walls have an average thickness of 50 to 130 μm and a cell density of 15 to 140 cells/cm ² . Molding to produce a ceramic molded body having a relative density of 60% or more by molding a clay containing ceramic raw materials including BaCO ₃ powder, TiO ₂ powder, and rare earth nitrate and/or hydroxide powder. process and
and a sintering step of holding the ceramic compact at 1150 to 1250° C., then raising the temperature to a maximum temperature of 1360 to 1430° C. at a rate of 20 to 500° C./hour and holding the temperature for 0.5 to 5 hours. , a method for producing a ceramic body. 17. The method for producing a ceramic body according to claim 16, wherein the holding time at 1150-1250° C. is 0.5-5 hours. 18. The method for producing a ceramic body according to claim 16, wherein said firing step includes holding at 900-950° C. for 0.5-5 hours. The method for producing a ceramic body according to any one of claims 16 to 18, wherein the ceramic raw material contains the rare earth hydroxide powder. A heater element comprising the ceramic body according to any one of claims 1 to 15. 21. The heater element according to claim 20, which is used for heating a passenger compartment. A heater unit comprising two or more heater elements according to claim 20 or 21. 23. The heater unit of claim 22,
an inflow pipe that communicates between an outside air introduction part or a vehicle compartment and an inflow port of the heater unit;
A heater system comprising: a battery for applying voltage to the heater unit; and an outflow pipe connecting an outflow port of the heater unit and the vehicle interior. 15. A heater comprising: the ceramic body according to claim 14; 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. element 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 communicating between the casing and the heater element or the inlet of the heater unit;
an outflow pipe that communicates with the outflow port of the heater element or the heater unit and the vehicle interior and the vehicle exterior; Purification system with valve.

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