Heater element and passenger compartment purification system

Abstract

To provide a heater element which can widen an area in a direction of extension of a flow channel capable of effectively being heated.SOLUTION: The present invention relates to a heater element which has a honeycomb structure and satisfies either condition of the following (i) or (ii): (i) a first electrode is provided on one end face, and a second electrode has an electrode part A provided on the other end face of the honeycomb structure, and an electrode part B coupled with the electrode part A and provided on a surface of a partition wall over a predetermined length in a direction of extension of a flow channel from the other end face; (ii) the first electrode has an electrode part A provided on one end face, and an electrode part B coupled with the electrode part A and provided on the surface of the partition wall over a predetermined length in a direction of extension of the flow channel from one end face, and the second electrode has an electrode part A provided on the other end face, and an electrode part B coupled with the electrode part A and provided on the surface of the partition wall over a predetermined length in a direction of extension of the flow channel from the other end face.SELECTED DRAWING: Figure 1C

Description

Technical Field

[0001] The present invention relates to a heater element and a vehicle interior purification system.

Background Art

[0002] In various vehicles such as automobiles, the demand for improving the vehicle interior environment is increasing. Specific requirements include reducing CO2 in the vehicle interior to suppress the driver's drowsiness, controlling the humidity in the vehicle interior, and removing harmful volatile components such as odor components and allergy-inducing components in the vehicle interior. Ventilation is cited as an effective measure for such requirements, but ventilation is a factor that greatly loses heater energy in winter and causes deterioration of energy efficiency in winter. In particular, in a battery electric vehicle (BEV), there is a problem that the cruising range is significantly reduced due to such energy loss.

[0003] As a method for solving the above problems, Patent Document 1 and Patent Document 2 disclose a vehicle interior purification system that captures components to be removed such as water vapor and CO2 in the air in the vehicle interior by a functional material such as an adsorbent, and then reacts or desorbs the components to be removed by heating and discharges them outside the vehicle to regenerate the functional material. In such a vehicle interior purification system, it is required that the contact between the air and the functional material is as much as possible to ensure the capture performance of the components to be removed, and that the functional material can be heated to a predetermined temperature to promote the regeneration of the functional material. Regeneration is performed, for example, by a method of removing the substance adsorbed on the functional material by an oxidation reaction, a method of desorbing and discharging the substance adsorbed on the functional material, etc. In any case, it is necessary to heat the functional material to an appropriate temperature according to the adsorbed substance.

[0004] On the other hand, Patent Document 3 discloses a columnar honeycomb structure part having an outer peripheral side wall and a partition wall disposed inside the outer peripheral side wall and partitioning a plurality of cells that form a flow path from a first end face to a second end face. The partition wall has PTC characteristics, the average thickness of the partition wall is 0.13 mm or less, and the opening ratio at the first and second end faces is 0.81 or more. This heater element is used for a heater for warming a vehicle interior.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The heater element described in Patent Document 3 is used for warming the vehicle interior. Since it has a honeycomb structure, the heating area can be increased, so it is an efficient heating means. Therefore, if such a heater element is used as a carrier for a functional material, it is considered that it can contribute to shortening the regeneration time of the functional material. In particular, since the heater element described in Patent Document 3 can be heated by energization and has PTC characteristics, while the functional material can be easily heated, it is also considered that excessive heat generation can be suppressed and thermal deterioration of the functional material can be suppressed. In addition, since the risk of reaching an excessive temperature is avoided, safety can be ensured even if the initial resistance is set small to increase the heating speed, and the temperature can be raised in a short time.

[0007] However, as a result of the inventor's study, when a functional material-containing layer is provided on the surface of the partition wall that forms the cells of the heater element described in Patent Document 3, it is difficult for the temperature to rise in the vicinity of the inlet side of the heater element, and it has been found that the region in the direction in which the flow path for effectively heating the functional material extends within the cell becomes narrow. That is, a part of the functional material supported on the heater element has low regeneration efficiency and cannot be effectively utilized. Further, when the functional material is a catalyst, heating may be required for catalyst activation, but if the temperature rise of the supported catalyst is insufficient, the catalyst cannot be effectively utilized. Providing a functional material-containing layer that cannot be effectively utilized is a factor that reduces the cost performance of the heater element.

[0008] The present invention has been created in view of the above circumstances, and in one embodiment, an object is to provide a heater element capable of widening the region in the extending direction of the flow path for effectively heating the functional material. Further, in another embodiment of the present invention, an object is to provide a vehicle interior purification system including such a heater element. In yet another embodiment of the present invention, an object is to provide a vehicle interior purification system useful for increasing the ratio of effective utilization of the functional material.

Means for Solving the Problems

[0009] [Aspect 1] A honeycomb structure having an outer peripheral wall and a partition wall disposed inside the outer peripheral wall and partitioning and forming a plurality of cells that form a flow path extending from one end face to the other end face, wherein at least the partition wall is made of a material having PTC characteristics; and A pair of electrodes composed of a first electrode and a second electrode; Comprising The heater element in which the first electrode and the second electrode satisfy any one of the following conditions (i) or (ii): (i) The first electrode is provided on the one end face, The second electrode has an electrode portion A provided on the other end face, and an electrode portion B provided on the surface of the partition wall over a predetermined length in the direction in which the flow path extends from the other end face and connected to the electrode portion A; (ii) The first electrode has an electrode portion A provided on the one end face, and an electrode portion B provided on the surface of the partition wall over a predetermined length in the direction in which the flow path extends from the one end face and connected to the electrode portion A, The second electrode has an electrode portion A provided on the other end face, and an electrode portion B provided on the surface of the partition wall over a predetermined length in the direction in which the flow path extends from the other end face and connected to the electrode portion A. [Aspect 2] The heater element according to Aspect 1, wherein the predetermined length of the electrode portion B is an average length of 1 / 200 or more and less than 1 / 2 with respect to the length in the extending direction of the flow path of the honeycomb structure. [Aspect 3] The heater element according to Aspect 1 or 2, wherein the electrode portion B is continuously provided over the predetermined length on the entire surface of all the partition walls that partition and form the plurality of cells. [Aspect 4] The heater element according to Aspect 1 or 2, wherein the electrode portion B is continuously provided over the predetermined length on the surface of a part of the partition walls that partition and form the plurality of cells. [Aspect 5] The heater element according to any one of Aspects 1 to 4, wherein the material having PTC characteristics is composed of a material mainly containing barium titanate and substantially free of lead. [Aspect 6] The heater element according to any one of Aspects 1 to 5, wherein the volume resistivity of the material having PTC characteristics at 25°C is 0.5 Ω·cm or more and 20 Ω·cm or less. [Aspect 7] The heater element according to any one of Aspects 1 to 6, wherein the average thickness of the electrode portion B is 1 / 10000 or more and 1 / 10 or less of the hydraulic diameter of the cell. [Aspect 8] The honeycomb structure has a partition wall thickness of 0.125 mm or less, a cell density of 100 cells / cm 2 or less, and a cell pitch of 1.0 mm or more, and is the heater element according to any one of Aspects 1 to 7. [Aspect 9] The honeycomb structure has a partition wall thickness of 0.08 mm or more and 0.36 mm or less, a cell density of 2.54 cells / cm 2 or more and 140 cells / cm 2 or less, and an aperture ratio of the cell of 0.70 or more, and is the heater element according to any one of Aspects 1 to 7. [Aspect 10] The first electrode and the second electrode are made of the same material, and is the heater element according to any one of Aspects 1 to 9. [Aspect 11] The heater element according to any one of Aspects 1 to 10, comprising a functional material-containing layer on the surface of the partition wall. [Aspect 12] The heater element according to Aspect 11, wherein the functional material-containing layer contains a functional material having a function of adsorbing one or more selected from water vapor, carbon dioxide, and odor components. [Aspect 13] The heater element according to Aspect 11 or 12, wherein the functional material-containing layer contains a catalyst. [Aspect 14] At least one heater element according to any one of Aspects 1 to 13, a power supply for applying a voltage to the heater element, an inflow pipe communicating the passenger compartment with an inlet end face of the heater element, an outflow pipe having a first path communicating an outlet end face of the heater element with the passenger compartment, a ventilator for causing air from the passenger compartment to flow into the inlet end face of the heater element through the inflow pipe, and The heater element is arranged such that the inlet end face is the one end face and the outlet end face is the other end face, or the inlet end face is the other end face and the outlet end face is the one end face. Passenger compartment purification system. [Aspect 15] The passenger compartment purification system according to Aspect 14, wherein the heater element is arranged such that the inlet end face is the one end face and the outlet end face is the other end face. [Aspect 16] In addition to the first path, the outflow pipe has a second path that communicates the outlet end face of the heater element with the outside of the vehicle. The outflow pipe has a switching valve capable of switching the flow of air flowing through the outflow pipe between the first path and the second path. A first mode in which the applied voltage from the power source is turned off, the switching valve is switched so that the air flowing through the outflow pipe passes through the first path, and the ventilator is turned on. A second mode in which the applied voltage from the power source is turned on, the switching valve is switched so that the air flowing through the outflow pipe passes through the second path, and the ventilator is turned on. The passenger compartment purification system according to Aspect 14 or 15, comprising a control unit capable of performing switching between the above. [Aspect 17] A honeycomb structure having 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 extending from an inlet end face to an outlet end face; and A functional material-containing layer provided on the surface of the partition wall; The passenger compartment purification system according to any one of Aspects 14 to 16, wherein a functional addition body including the above is disposed adjacent to the downstream side of the heater element. [Aspect 18] The passenger compartment purification system according to Aspect 17, wherein at least the partition wall of the functional addition body is made of cordierite. [Aspect 19] · A honeycomb structure having an outer peripheral wall and partition walls that are disposed inside the outer peripheral wall and define a plurality of cells that form a flow path extending from an inlet end face to an outlet end face; A first electrode provided on the inlet end face; and A second electrode provided on the outlet end face; A heater element including the above; and · A honeycomb structure having an outer peripheral wall and partition walls that are disposed inside the outer peripheral wall and define a plurality of cells that form a flow path extending from an inlet end face to an outlet end face; and A functional material-containing layer provided on the surface of the partition wall; A functional addition body that includes the above and is disposed adjacent to the downstream side of the heater element; and · A power source for applying a voltage to the heater element; · An inflow pipe that communicates the passenger compartment with the inlet end face of the heater element; · An outflow pipe having a first path that communicates the outlet end face of the functional addition body with the passenger compartment; · A ventilator for allowing air from the passenger compartment to flow into the inlet end face of the heater element through the inflow pipe; A passenger compartment purification system including the above.

Advantages of the Invention

[0010] According to one embodiment of the present invention, there is provided a heater element capable of widening the region in the extending direction of the flow path where the functional material can be effectively heated. Further, according to another embodiment of the present invention, there is provided a passenger compartment purification system including the heater element. When a functional material-containing layer is provided on the partition wall surface of the heater element, the ratio of functional materials that are difficult to regenerate and not effectively utilized and / or functional materials that are not effectively utilized because the temperature rise is insufficient can be reduced. That is, the region of the functional material-containing layer that can be effectively utilized is widened. Thereby, it becomes possible to improve the cost performance of the heater element.

[0011] Also, in the vehicle interior purification system according to still another embodiment of the present invention in which the heater element is disposed on the upstream side and the functional addition body is disposed on the downstream side, it is possible to increase the ratio of effective utilization of the functional material.

Brief Description of the Drawings

[0012]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7A

Figure 7B

Figure 7C

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] 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 added to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention, and such modified and improved embodiments also fall within the scope of the present invention.

[0014] (1. Heater element) The heater element according to an embodiment of the present invention can be suitably used as a heater element for a passenger compartment purification system in various vehicles such as automobiles. The vehicle is not particularly limited, and examples include automobiles and trains. The automobile is not particularly limited, and examples include gasoline vehicles, diesel vehicles, gas fuel vehicles using CNG (compressed natural gas), LNG (liquefied natural gas), etc., fuel cell vehicles, electric vehicles, and plug-in hybrid vehicles. The heater element according to the embodiment of the present invention can be suitably used particularly for vehicles without an internal combustion engine such as electric vehicles and trains.

[0015] FIGS. 1A to 1D show a schematic perspective view and a cross-sectional view of a heater element 1 according to a first embodiment of the present invention. FIGS. 2A to 2D show a schematic perspective view and a cross-sectional view of a heater element 2 according to a second embodiment of the present invention. As shown in FIGS. 1A to 1D and FIGS. 2A to 2D, the heater elements 1 and 2 include a honeycomb structure 10 having an outer peripheral wall 11 and a partition wall 14 that is disposed inside the outer peripheral wall 11 and partitions a plurality of cells 13 that form a flow path extending from one end face 12a to the other end face 12b. The heater elements 1 and 2 include a pair of electrodes composed of a first electrode 30a and a second electrode 30b. Further, the heater elements 1 and 2 can include a functional material-containing layer 20 provided on the surface of the partition wall 14. Hereinafter, each component of the heater elements 1 and 2 will be described in detail.

[0016] (1-1. Honeycomb structure) The shape of the honeycomb structure 10 is not particularly limited. For example, the outer shape of a cross section orthogonal to the flow path direction (the direction in which the cells 13 extend) of the honeycomb structure 10 can be a polygon (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), a circle, an oval shape (oval, ellipse, oblong, rounded rectangle, etc.), or the like. Note that the end faces (one end face 12a and the other end face 12b) have the same shape as the cross section. Further, when the cross section and the end faces are polygons, the corners may be chamfered.

[0017] The shape of the cell 13 is not particularly limited, but in a cross-section orthogonal to the flow path direction of the honeycomb structure 10, it can be a polygon (quadrilateral, pentagon, hexagon, heptagon, octagon, etc.), a circle, or an oval shape. These shapes may be single or a combination of two or more. Among these shapes, a quadrilateral or a hexagon is preferable. By providing the cell 13 with such a shape, the pressure loss when air flows can be reduced. Note that FIGS. 1 and 2 show, as an example, the honeycomb structure 10 in which the outer shape of the cross-section and the shape of the cell 13 are quadrilaterals in a cross-section orthogonal to the flow path direction.

[0018] The honeycomb structure 10 may be a honeycomb bonded body having a plurality of honeycomb segments and a bonding layer that bonds the outer peripheral side surfaces of the plurality of honeycomb segments to each other. By using the honeycomb bonded body, it becomes possible to increase the total cross-sectional area of the cell 13, which is important for ensuring the air flow rate while suppressing the occurrence of cracks. Note that the bonding layer can be formed using a bonding material. The bonding material is not particularly limited, but a material obtained by adding a solvent such as water to a ceramic material to make it paste-like can be used. The bonding material may contain a material having PTC characteristics or may contain the same material as the outer peripheral wall 11 and the partition wall 14. In addition to the role of bonding the honeycomb segments to each other, the bonding material can also be used as an outer peripheral coating material after bonding the honeycomb segments.

[0019] From the viewpoints of ensuring the strength of the honeycomb structure 10, reducing the pressure loss when air passes through the cell 13, ensuring the loading amount of the functional material, and ensuring the contact area with the air flowing in the cell 13, it is desirable to suitably combine the thickness of the partition wall 14, the cell density, and the cell pitch (or the opening ratio of the cell). In this specification, the thickness of the partition wall 14 refers to the length when a line segment connecting the centers of gravity of adjacent cells 13 crosses the partition wall 14 in a cross-section orthogonal to the flow path direction. The thickness of the partition wall 14 refers to the average value of the thicknesses of all the partition walls 14. In this specification, the cell density is a value obtained by dividing the number of cells by the area of one end face of the honeycomb structure 10 (the total area of the partition walls 14 and the cells 13 excluding the outer peripheral wall 11). In this specification, the cell pitch refers to a value obtained by the following calculation. First, the area per cell is calculated by dividing the area of one end face of the honeycomb structure 10 (the total area of the partition walls 14 and the cells 13 excluding the outer peripheral wall 11) by the number of cells. Next, the square root of the area per cell is calculated, and this is taken as the cell pitch. In this specification, the aperture ratio of the cell 13 is a value obtained by dividing the total area of the cells 13 partitioned by the partition walls 14 in a cross section orthogonal to the flow path direction of the honeycomb structure 10 by the area of one end face (the total area of the partition walls 14 and the cells 13 excluding the outer peripheral wall 11). Note that when calculating the aperture ratio of the cell 13, the first electrode 30a, the second electrode 30b, and the functional material-containing layer 20 are not considered.

[0020] In an advantageous embodiment from the viewpoint of supporting a sufficient amount of functional material, the thickness of the partition wall is 0.125 mm or less, the cell density is 100 cells / cm 2 or less, and the cell pitch is 1.0 mm or more. In a preferred embodiment, the thickness of the partition wall is 0.100 mm or less, the cell density is 70 cells / cm 2 or less, and the cell pitch is 1.2 mm or more. In a more preferred embodiment, the thickness of the partition wall is 0.080 mm or less, the cell density is 65 cells / cm 2 or less, and the cell pitch is 1.3 mm or more.

[0021] In each of the above embodiments, from the viewpoints of ensuring the strength of the honeycomb structure and keeping the electrical resistance low, the lower limit of the thickness of the partition wall is preferably 0.010 mm or more, more preferably 0.020 mm or more, and even more preferably 0.030 mm or more. In each of the above embodiments, from the viewpoints of ensuring the strength of the honeycomb structure, keeping the electrical resistance low, and increasing the surface area to promote reaction, adsorption, and desorption, the lower limit of the cell density is preferably 30 cells / cm 2 or more, and more preferably 35 cells / cm2 More preferably, it is as described above, and 40 cells / cm 2 Even more preferably, it is as described above. In each of the above embodiments, from the viewpoints of ensuring the strength of the honeycomb structure, keeping the electrical resistance low, and increasing the surface area to promote reaction, adsorption, and desorption, the upper limit of the cell pitch is preferably 2.0 mm or less, more preferably 1.8 mm or less, and even more preferably 1.6 mm or less.

[0022] In an advantageous embodiment from the viewpoint of achieving both reduction of pressure loss and maintenance of strength, the thickness of the partition wall is 0.08 mm or more and 0.36 mm or less, the cell density is 2.54 cells / cm 2 or more and 140 cells / cm 2 or less, and the aperture ratio of the cells is 0.70 or more. In a preferred embodiment, the thickness of the partition wall is 0.09 mm or more and 0.35 mm or less, the cell density is 15 cells / cm 2 or more and 100 cells / cm 2 or less, and the aperture ratio of the cells is 0.80 or more. In a more preferred embodiment, the thickness of the partition wall is 0.14 mm or more and 0.30 mm or less, the cell density is 20 cells / cm 2 or more and 90 cells / cm 2 or less, and the aperture ratio of the cells is 0.85 or more.

[0023] In each of the above embodiments, from the viewpoint of ensuring the strength of the honeycomb structure, the upper limit of the aperture ratio of the cells is preferably 0.94 or less, more preferably 0.92 or less, and even more preferably 0.90 or less.

[0024] The thickness of the outer peripheral wall 11 is not particularly limited, but it is preferably determined based on the following viewpoints. First, from the viewpoint of reinforcing the honeycomb structure 10, the thickness of the outer peripheral wall 11 is preferably 0.05 mm or more, more preferably 0.06 mm or more, and still more preferably 0.08 mm or more. On the other hand, from the viewpoints of increasing the electrical resistance to suppress the initial current and reducing the pressure loss when air flows, the thickness of the outer peripheral wall 11 is preferably 1.0 mm or less, more preferably 0.5 mm or less, still more preferably 0.4 mm or less, and even more preferably 0.3 mm or less. In this specification, the thickness of the outer peripheral wall 11 refers to the length in the normal direction of the side surface from the boundary between the outer peripheral wall 11 and the outermost peripheral cell 13 or partition wall 14 to the side surface of the honeycomb structure 10 in a cross section orthogonal to the flow path direction.

[0025] The length of the honeycomb structure 10 in the flow path direction and the cross-sectional area orthogonal to the flow path direction may be adjusted according to the sizes of the required heater elements 1 and 2 and are not particularly limited. For example, when used for compact heater elements 1 and 2 while ensuring a predetermined function, the honeycomb structure 10 has a length in the flow path direction of 2 to 20 mm and a cross-sectional area orthogonal to the flow path direction of 10 cm 2 or more. The upper limit value of the cross-sectional area orthogonal to the flow path direction is not particularly limited, but is, for example, 300 cm 2 or less.

[0026] The partition wall 14 constituting the honeycomb structure 10 is made of a material capable of generating heat by energization, and specifically, is made of a material having PTC (Positive Temperature Coefficient) characteristics. If necessary, the outer peripheral wall 11 may also be made of a material having PTC characteristics similar to those of the partition wall 14.

[0027] The functional material-containing layer 20 can be heated by heat transfer from the heat-generating partition wall 14 (and the outer peripheral wall 11 as required). In addition, a material having PTC characteristics has the property that when the temperature rises and exceeds the Curie point, the resistance value rapidly increases and it becomes difficult for electricity to flow. Therefore, when the heater elements 1 and 2 become hot, the partition wall 14 (and the outer peripheral wall 11 as required) restricts the current flowing through them, so excessive heat generation of the heater elements 1 and 2 is suppressed. Accordingly, it is also possible to suppress the thermal degradation of the functional material-containing layer 20 caused by excessive heat generation.

[0028] From the viewpoint of obtaining appropriate heat generation, the lower limit of the volume resistivity of the material having PTC characteristics at 25°C is preferably 0.5 Ω·cm or more, more preferably 1 Ω·cm or more, and still more preferably 5 Ω·cm or more. From the viewpoint of generating heat at a low driving voltage, the upper limit of the volume resistivity of the material having PTC characteristics at 25°C is preferably 20 Ω·cm or less, more preferably 18 Ω·cm or less, and still more preferably 16 Ω·cm or less. In this specification, the volume resistivity of the material having PTC characteristics at 25°C is measured in accordance with JIS K6271:2008.

[0029] From the viewpoint of being capable of generating heat by energization and having PTC characteristics, the outer peripheral wall 11 and the partition wall 14 are preferably made of a material mainly composed of barium titanate (BaTiO3), and more preferably a ceramic composed of a material mainly composed of barium titanate (BaTiO3)-based crystal particles in which part of Ba is substituted with a rare earth element. In this specification, "main component" means a component whose proportion in the total components exceeds 50% by mass. The content of the BaTiO3-based crystal particles can be determined by fluorescent X-ray analysis. Other crystal particles can also be measured in the same manner as this method.

[0030] The composition formula of the BaTiO3-based crystal particles in which 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 0.0001 ≦ 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, Y, 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. On the other hand, from the viewpoint of suppressing insufficient sintering and excessive increase in electrical resistance at room temperature, x is preferably 0.009 or less. The content in the ceramics of BaTiO3-based crystal particles in which a part of Ba is substituted with a rare earth element is not particularly limited as long as it is the main component amount, but is preferably 90% by mass or more, more preferably 92% by mass or more, and even more preferably 94% by mass or more. The upper limit value of the content of BaTiO3-based crystal particles is not particularly limited, but is generally 99% by mass, preferably 98% by mass. The content of this BaTiO3-based crystal particle can be measured by X-ray fluorescence analysis. The other crystal particles can also be measured in the same manner as this method.

[0031] From the viewpoint of reducing the environmental load, it is desirable that the materials used for the outer peripheral wall 11 and the partition wall 14 do not substantially contain lead (Pb). Specifically, the outer peripheral wall 11 and the partition wall 14 preferably have 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. By having a low Pb content, for example, the heated air can be safely applied to a living organism such as a human by contacting the partition wall 14 during heat generation. In the outer peripheral wall 11 and the partition wall 14, the Pb content, when converted to PbO, is preferably less than 0.03% by mass, more preferably less than 0.01% by mass, and even more preferably 0% by mass. The lead content can be determined by ICP-MS (inductively coupled plasma mass spectrometry).

[0032] The lower limit of the Curie point of the material constituting the outer peripheral wall 11 and the partition wall 14 is preferably 100°C or higher, more preferably 110°C or higher, still more preferably 125°C or higher, from the viewpoint of efficiently heating air. Regarding the upper limit of the Curie point, from the viewpoint of safety as a component placed in the passenger compartment or near the passenger compartment, it is preferably 250°C or lower, more preferably 225°C or lower, still more preferably 200°C or lower, and even more preferably 150°C or lower.

[0033] The Curie point of the material constituting the outer peripheral wall 11 and the partition wall 14 can be adjusted by the type and addition amount of the shifter. For example, the Curie point of barium titanate (BaTiO3) is about 120°C, but by substituting part of Ba and Ti with one or more of Sr, Sn, and Zr, the Curie point can be shifted to the lower temperature side.

[0034] In this specification, the Curie point is measured by the following method. Attach the sample to a sample holder for measurement, place it in a measurement tank (e.g., MINI-SUBZERO MC-810P manufactured by Espec Corporation), and measure the change in the electrical resistance of the sample with respect to the temperature change when heating from 10°C using a DC resistance meter (e.g., multimeter 3478A manufactured by YOKOGAWA HEWLETT PACKARD, LTD). Based on the electrical resistance-temperature plot obtained by the measurement, the temperature at which the resistance value becomes twice the resistance value at room temperature (20°C) is defined as the Curie point.

[0035] (1-2. Electrode) In the heater element 1 according to the first embodiment of the present invention, the first electrode 30a is provided on one end face 12a. The second electrode 30b has an electrode portion A provided on the other end face 12b and an electrode portion B provided on the surface of the partition wall 14 over a predetermined length D1 in the direction in which the flow path extends from the other end face 12b and connected to the electrode portion A.

[0036] In the heater element 1 according to the first embodiment, by arranging the first electrode 30a and the second electrode 30b in this way, compared with the case where the first electrode 30a and the second electrode 30b are provided only on one end face 12a and the other end face 12b respectively, the distance in the extending direction of the flow path between the first electrode 30a and the second electrode 30b can be shortened. Since the electrical resistance decreases as the distance between the electrodes shortens, it becomes possible to widen the region in the extending direction of the flow path that can be effectively heated.

[0037] In the first embodiment, air may be circulated inside the cell 13 of the heater element 1 such that one end face 12a is the upstream side and the other end face 12b is the downstream side, or air may be circulated inside the cell 13 of the heater element 1 such that one end face 12a is the downstream side and the other end face 12b is the upstream side. However, the upstream side portion of the heater element 1 is cooled by the cold inflowing air, while the downstream side portion is not cooled because the inflowing air is heated. Therefore, since the downstream side portion is sufficiently heated by heat conduction, no current flows through the honeycomb structure 10 in the downstream side portion, and even if electricity flows through the electrodes provided in the extending direction of the flow path, it can be sufficiently heated. For this reason, circulating inside the cell 13 of the heater element 1 such that one end face 12a is the upstream side and the other end face 12b is the downstream side is preferable in that it can further widen the region in the extending direction of the flow path that can effectively heat the functional material-containing layer 20.

[0038] In the heater element 2 according to the second embodiment of the present invention, the first electrode 30a has an electrode portion A provided on one end face 12a and an electrode portion B provided on the surface of the partition wall 14 and connected to the electrode portion A and extending over a predetermined length D2a in the extending direction of the flow path from one end face 12a. Further, the second electrode 30b has an electrode portion A provided on the other end face 12b and an electrode portion B provided on the surface of the partition wall 14 and connected to the electrode portion A and extending over a predetermined length D2b in the extending direction of the flow path from the other end face 12b.

[0039] In the heater element 2 according to the second embodiment, by arranging the first electrode 30a and the second electrode 30b in this way, compared with the case where the first electrode 30a and the second electrode 30b are provided only on one end face 12a and the other end face 12b respectively, the distance in the extending direction of the flow path between the first electrode 30a and the second electrode 30b can be shortened. Since the electrical resistance decreases as the distance between the electrodes shortens, it becomes possible to widen the region in the extending direction of the flow path that can be effectively heated.

[0040] In the second embodiment, air may be circulated inside the cell 13 of the heater element 2 such that one end face 12a is on the upstream side and the other end face 12b is on the downstream side, or air may be circulated inside the cell 13 of the heater element 2 such that one end face 12a is on the downstream side and the other end face 12b is on the upstream side. However, as described above, the downstream portion of the heater element 2 can be heated even if no current flows through the honeycomb structure 10 and electricity flows through the electrodes provided in the extending direction of the flow path. For this reason, it is preferable to circulate air inside the cell 13 of the heater element 2 such that the end face having the electrode with the shorter average length of D2a and D2b is on the upstream side and the end face having the electrode with the longer average length is on the downstream side, in that it can further widen the region in the extending direction of the flow path that can effectively heat the functional material-containing layer 20.

[0041] In both the first and second embodiments, the longer the predetermined length (D1, D2a, D2b) of the electrode portion B, the shorter the distance between the electrodes can be. For this reason, the predetermined length (D1, D2a, D2b) of the electrode portion B is preferably an average length of 1 / 200 or more, more preferably 1 / 100 or more, and even more preferably 1 / 50 or more with respect to the length in the extending direction of the flow path of the honeycomb structure 10. However, the predetermined length (D1, D2a, D2b) of the electrode portion B is preferably an average length of less than 1 / 2, more preferably 1 / 3 or less, and even more preferably 1 / 4 or less for the reasons that the distance that can be heated by heat conduction is limited and that the electrode portion B of the first electrode 30a and the electrode portion B of the second electrode 30b may come into contact with each other and cause a short circuit.

[0042] The average length of the electrode portion B in the extending direction of the flow path of the honeycomb structure 10 is measured by the following procedure. First, a cross-sectional image of the heater element at about 50 times magnification is obtained with a scanning electron microscope or the like. The cross-section is a cross-section parallel to the flow path direction passing through the central axis O extending in the flow path direction of the honeycomb structure 10 as exemplified in FIGS. 1C and 2C. The position of the central axis O is the centroid position in the cross-section orthogonal to the flow path of the honeycomb structure 10 (see FIGS. 1A and 2A). Next, when obtaining the average lengths of D1 and D2b of the second electrode 30b, the lengths in the extending direction of the flow path from the other end face 12b of the honeycomb structure 10 of all the electrode portions B of the second electrode 30b in the cross-sectional image are obtained, and the average value is calculated. When obtaining the average length of D2a of the first electrode 30a, the lengths in the extending direction of the flow path from one end face 12a of the honeycomb structure 10 of all the electrode portions B of the first electrode 30a in the cross-sectional image are obtained, and the average value is calculated.

[0043] By applying a voltage between the first electrode 30a and the second electrode 30b, it becomes possible to generate heat in the honeycomb structure 10 due to Joule heat. The first electrode 30a and the second electrode 30b may have extending portions that extend toward the outside of the honeycomb structure 10. By providing the extending portions, it becomes easier to connect to a connector that is responsible for connection to the outside.

[0044] The first electrode 30a and the second electrode 30b are not particularly limited. For example, a metal or alloy containing at least one selected from Cu, Ag, Al, Ni, and Si can be used. Also, an ohmic electrode capable of making ohmic contact with the outer peripheral wall 11 and / or the partition wall 14 having PTC characteristics can be used. The ohmic electrode 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, Zn, Ge, Sn, Se, and Te for an n-type semiconductor as a dopant. Also, the first electrode 30a and the second electrode 30b may have a single-layer structure or a laminated structure of two or more layers. When the first electrode 30a and the second electrode 30b have a laminated structure of two or more layers, the materials of each layer may be of the same type or different types.

[0045] The thicknesses of the first electrode 30a and the second electrode 30b are not particularly limited and can be appropriately set according to the formation method of the first electrode 30a and the second electrode 30b. Examples of the formation method of the first electrode 30a and the second electrode 30b include metal deposition methods such as sputtering, vapor deposition, electrolytic deposition, and chemical precipitation. Also, after applying an electrode paste, it is possible to form the electrodes 30a and 30b by baking or spraying. Further, the electrodes 30a and 30b may be formed by joining a metal plate or an alloy plate.

[0046] In either the first electrode 30a or the second electrode 30b, the thickness of the electrode portion A is preferably about 5 to 30 μm in baking of the electrode paste, about 100 to 1000 nm in dry plating such as sputtering and vapor deposition, about 10 to 100 μm in thermal spraying, and about 5 to 30 μm in wet plating such as electrolytic deposition and chemical deposition. In joining of a metal plate or an alloy plate, the thicknesses of the first electrode 30a and the second electrode 30b are preferably about 5 to 100 μm.

[0047] In either the first electrode 30a or the second electrode 30b, a larger average thickness of the electrode portion B is desirable in terms of ensuring electrical continuity, while a smaller one is advantageous in terms of reducing the ventilation resistance of the inflowing air. Therefore, the average thickness of the electrode portion B is preferably not less than 1 / 10000 and not more than 1 / 10 of the hydraulic diameter of the cell 13, and more preferably not less than 1 / 1000 and not more than 1 / 20 of the hydraulic diameter of the cell 13. The hydraulic diameter of the cell 13 is a value (P - t) obtained by subtracting the thickness t (mm) of the partition wall from the cell pitch P (mm) described above.

[0048] The average thickness of each electrode portion B of the first electrode 30a and the second electrode 30b is measured by the following procedure. First, a cross-sectional image of the heater element at about 50 times magnification is acquired with a scanning electron microscope or the like. As the cross-section, it is a cross-section parallel to the flow path direction passing through the central axis O extending in the flow path direction of the honeycomb structure 10 as illustrated in FIGS. 1C and 2C. The position of the central axis O is the center of gravity position in the cross-section orthogonal to the flow path direction of the honeycomb structure 10 (see FIGS. 1D and 2D). For each electrode portion B visually recognized from the cross-sectional image, the average thickness is calculated by dividing the cross-sectional area by the length in the extending direction of the flow path of the cell 13. This calculation is performed for all the electrode portions B of the first electrode 30a and the second electrode 30b visually recognized from the cross-sectional image, and the overall average value is taken as the average thickness of each electrode portion B of the first electrode 30a and the second electrode 30b.

[0049] In both the case of the heater element 1 according to the first embodiment and the heater element 2 according to the second embodiment, the electrode portion B is continuously provided over the entire surface of all the partition walls 14 that partition and form the plurality of cells 13 over the predetermined length. In other words, in the region of the predetermined length, when observing the heater elements 1 and 2 in a cross-section orthogonal to the flow path direction, all the partition walls 14 (the partition walls 14 that partition and form the outermost peripheral cells 13 and the outer peripheral wall 11) that partition and form the cells 13 are entirely covered over the entire circumference by the electrode portion B of the first electrode 30a or the second electrode 30b (see FIGS. 1D and 2D). With this configuration, the distance between the electrodes can be uniformly shortened in all the cells 13. As a result, it becomes easier to uniformly generate heat in the heater elements 1 and 2.

[0050] However, the electrode portion B of the first electrode 30a and the second electrode 30b may have a portion that does not cover the partition wall 14 when observing the heater elements 1 and 2 in a cross-section orthogonal to the flow path direction in the region of the predetermined length. That is, in another embodiment, the electrode portion B can be continuously provided over the predetermined length on a part of the surface of the partition walls 14 that partition and form the plurality of cells 13. Such embodiments include (1) an embodiment in which the electrode portion B is continuously provided over the predetermined length on a part of the surface of all the partition walls 14 that partition and form the plurality of cells 13, and (2) an embodiment in which the electrode portion B is continuously provided over the predetermined length on a part or the entire surface of a part of the partition walls 14 that partition and form the plurality of cells 13. FIGS. 3A to 3D show schematic diagrams of cross-sections orthogonal to the flow path direction before forming the functional material-containing layer 20 for heater elements according to several different embodiments in which the structure of the electrode portion B of the first electrode 30a or the second electrode 30b is different.

[0051] In the embodiment of FIG. 3A, the electrode portion B is provided in all the cells 13. Further, the partition walls 14 that partition and form each cell 13 (in the case of the outermost peripheral cell 13, the partition wall 14 and the outer peripheral wall 11 that partition and form the outermost peripheral cell 13) have a square cross-sectional shape, and all the corner portions 13b are covered by the electrode portion B. On the other hand, none of the side portions 13a other than the corner portions 13b are covered by the electrode portion B.

[0052] In the embodiment of FIG. 3B, the electrode portion B is provided in some of the cells 13. Further, the partition walls 14 that partition and form each cell 13 in which the electrode portion B is provided (in the case of the outermost peripheral cell 13 in which the electrode portion B is provided, the partition wall 14 and the outer peripheral wall 11 that partition and form the outermost peripheral cell 13) have a square cross-sectional shape, and all the corner portions 13b are covered by the electrode portion B. On the other hand, none of the side portions 13a other than the corner portions 13b are covered by the electrode portion B. When providing the electrode portion B in some of the cells 13, from the viewpoint of heat generation uniformity, the electrode portion B is provided point-symmetrically with the central axis O as the center of symmetry, or the electrode portion B is provided line-symmetrically with any line segment passing through the central axis O as the center of symmetry, in a cross-section orthogonal to the flow path direction.

[0053] In the embodiment of FIG. 3C, the electrode portion B is provided in all the cells 13. Further, the partition walls 14 that partition and form each cell 13 (in the case of the outermost peripheral cell 13, the partition wall 14 and the outer peripheral wall 11 that partition and form the outermost peripheral cell 13) have a square cross-sectional shape, and only one corner portion 13b is covered by the electrode portion B. On the other hand, none of the portions other than the one corner portion 13b are covered by the electrode portion B.

[0054] In the embodiment of FIG. 3D, the electrode portion B is provided in all the cells 13. Further, the partition walls 14 that partition and form each cell 13 (in the case of the outermost peripheral cell 13, the partition wall 14 and the outer peripheral wall 11 that partition and form the outermost peripheral cell 13) have a square cross-sectional shape, and only a pair of opposing corner portions 13b are covered by the electrode portion B. On the other hand, none of the portions other than the pair of opposing corner portions 13b are covered by the electrode portion B.

[0055] (1-3. Functional material-containing layer) The functional material-containing layer 20 can be provided on the surface of the partition wall 14 of the honeycomb structure 10 (in the case of the outermost peripheral cell 13, the partition wall 14 and the outer peripheral wall 11 that form the partition of the outermost peripheral cell 13). The functional material-containing layer 20 may be provided on the surface of at least one of the electrode portion B of the first electrode 30a and the electrode portion B of the second electrode 30b in addition to the partition wall 14. It is more preferable that the functional material-containing layer 20 is provided on the surface of at least the partition wall 14 of the honeycomb structure 10 and the electrode portion B of the second electrode 30b. When the electrode portion B of the first electrode 30a exists, it is more preferable that the functional material-containing layer 20 is provided on the surface of at least the partition wall 14 of the honeycomb structure 10, the electrode portion B of the first electrode 30a, and the electrode portion B of the second electrode 30b.

[0056] The functional material contained in the functional material-containing layer 20 is not particularly limited as long as it can exhibit a desired function, and an adsorbent, a catalyst, etc. can be used. The adsorbent preferably has a function of adsorbing one or more selected from the components to be removed in the air, such as water vapor, carbon dioxide, and odor components. In addition, it is also preferable to have a function of adsorbing harmful volatile components. Further, by using a catalyst, the component to be removed can be purified. Furthermore, for the purpose of enhancing the capturing function of the component to be removed by the adsorbent, the adsorbent and the catalyst may be used in combination.

[0057] The adsorbent preferably has a function of adsorbing components to be removed, such as water vapor, carbon dioxide, and harmful volatile components (such as aldehydes, odor components, etc.) at -20 to 40°C and desorbing at a high temperature of 60°C or higher. Examples of such adsorbents include zeolite, silica gel, activated carbon, alumina, silica, low-crystalline clay, and amorphous aluminum silicate composites. The type of the adsorbent may be appropriately selected according to the type of the component to be removed. The adsorbent may be used alone or in combination of two or more.

[0058] The catalyst preferably has a function capable of promoting an oxidation-reduction reaction. Examples of such catalysts include metal catalysts such as Pt, Pd, and Ag, and oxide catalysts such as CeO2 and ZrO2. The catalyst may be used alone or in combination of two or more kinds.

[0059] Harmful volatile components contained in the air in the passenger compartment are, for example, volatile organic compounds (VOCs) 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, di-2-ethylhexyl phthalate, diazinon, acetaldehyde, 2-(1-methylpropyl)phenyl N-methylcarbamate, and the like.

[0060] The average thickness of the functional material-containing layer 20 may be determined according to the size of the cell 13 and is not particularly limited. For example, from the viewpoint of ensuring sufficient contact with air, the average thickness of the functional material-containing layer 20 is preferably 20 μm or more, more preferably 25 μm or more, and still more preferably 30 μm or more. On the other hand, from the viewpoint of suppressing peeling of the functional material-containing layer 20 from the partition wall 14 and the outer peripheral wall 11, the average thickness of the functional material-containing layer 20 is preferably 400 μm or less, more preferably 380 μm or less, and still more preferably 350 μm or less.

[0061] The average thickness of the functional material-containing layer 20 is measured by the following procedure. As illustrated in FIGS. 1C and 2C, an arbitrary cross section parallel to the flow path direction is cut out through the central axis O extending in the flow path direction of the honeycomb structure 10, and a cross-sectional image of about 50 times magnification is obtained with a scanning electron microscope or the like. The position of the central axis O is the centroid position in the cross section orthogonal to the flow path direction of the honeycomb structure 10 (see FIGS. 1D and 2D). For each functional material-containing layer 20 visible from the cross-sectional image, the average thickness is calculated by dividing the cross-sectional area by the length of the cell 13 in the flow path direction. This calculation is performed for all the functional material-containing layers 20 visible from the cross-sectional image, and the overall average value is taken as the average thickness of the functional material-containing layer 20.

[0062] From the perspective that the functional material exhibits the desired functions within the heater elements 1 and 2, the amount of the functional material-containing layer 20 is preferably 50 g / L or more and 500 g / L or less, more preferably 100 g / L or more and 400 g / L or less, and even more preferably 150 g / L or more and 350 g / L or less, based on the volume of the honeycomb structure 10. Note that the volume of the honeycomb structure 10 is a value determined by the outer dimensions of the honeycomb structure 10.

[0063] (2. Method for manufacturing the heater element) Next, a method for manufacturing the heater element according to the present invention will be illustratively described. The method for manufacturing the honeycomb structure constituting the heater element includes a forming step and a firing step. In the forming step, a green soil containing a ceramic raw material including BaCO3 powder, TiO2 powder, and a powder of a rare earth nitrate or hydroxide is formed to produce a honeycomb formed body having a relative density of 60% or more. The ceramic raw material can be obtained by dry-mixing each powder so as to have a desired composition. The green soil can be obtained by adding a dispersion medium, a binder, a plasticizer, and a dispersant to the ceramic raw material and kneading them. The green soil may contain additives such as a shifter, a metal oxide, a property improver, and a conductor powder as necessary. The blending amounts of the components other than the ceramic raw material are not particularly limited as long as the relative density of the honeycomb formed body is 60% or more.

[0064] Here, in this specification, the "relative density of the honeycomb formed body" means the ratio of the density of the honeycomb formed body to the true density of the entire ceramic raw material. Specifically, it can be obtained by the following formula. Relative density of honeycomb formed body (%) = Density of honeycomb formed body (g / cm 3 ) / True density of entire ceramic raw material (g / cm 3 ) × 100 The density of the honeycomb formed body can be measured by the Archimedes method using pure water as the medium. Also, 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 ).

[0065] Examples of the dispersion medium include water, or a mixed solvent of water and an organic solvent such as alcohol, and water can be particularly preferably used.

[0066] Examples of the binder include organic binders such as methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. In particular, it is preferable to use methyl cellulose and hydroxypropyl methyl cellulose in combination. The binder may be used alone or in combination of two or more, but it is preferably free of alkali metal elements.

[0067] Examples of the plasticizer include polyoxyalkylene alkyl ether, polycarboxylic acid-based polymer, and alkyl phosphate ester.

[0068] 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.

[0069] The honeycomb formed body can be produced by extrusion molding the clay. During extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0070] The relative density of the honeycomb formed body obtained by extrusion molding is 60% or more, preferably 65% or more. By controlling the relative density of the honeycomb formed body within such a range, it is possible to densify the honeycomb formed body and reduce the electrical resistance at room temperature. The upper limit value of the relative density of the honeycomb formed body is not particularly limited, but is generally 80%, preferably 75%.

[0071] The honeycomb 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.

[0072] The firing process includes holding at 1150 - 1250°C, then raising the temperature to the maximum temperature of 1360 - 1430°C at a heating rate of 20 - 600°C / hour and holding for 0.5 - 10 hours. By holding the honeycomb formed body at the maximum temperature of 1360 - 1430°C for 0.5 - 10 hours, a 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, the 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 - 600°C / hour, 1.0 - 10.0 mass% of Ba6Ti 17 O 40 crystal particles can be generated in the honeycomb structure 10.

[0073] The holding time at 1150 - 1250°C is not particularly limited, but is preferably 0.5 - 10 hours. By setting such a holding time, the Ba2TiO4 crystal particles generated during the firing process are easily and stably removed.

[0074] The firing process preferably includes holding at 900 to 950 °C for 0.5 to 5 hours during the temperature rise. By holding at 900 to 950 °C for 0.5 to 5 hours, BaCO3 decomposes efficiently, and the honeycomb structure 10 having a predetermined composition is easily obtained.

[0075] Note that 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, etc. can be used.

[0076] By joining a pair of electrodes (first electrode 30a and second electrode 30b) to the honeycomb structure thus obtained, a heater element can be manufactured. The electrode portions A of the first electrode 30a and the second electrode 30b can be formed on one end face 12a and the other end face 12b of the honeycomb structure 10 by a metal deposition method such as sputtering, vapor deposition, electroplating, or chemical precipitation. Also, the electrode portion A can be formed by applying an electrode paste to one end face 12a and the other end face 12b of the honeycomb structure 10 and then baking it. Furthermore, it can also be formed by spraying. The electrode portion A may be composed of a single layer, but can also be composed of a plurality of electrode layers having different compositions. When forming the electrode portion A on the end face by the above method, if the thickness of the electrode layer is set so as not to be excessively large, the cell can be prevented from being blocked. For example, the thickness of the electrode is preferably about 5 to 30 μm in the case of baking the 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 spraying, and about 5 to 30 μm in the case of wet plating such as electroplating and chemical precipitation.

[0077] When the first electrode 30a and the second electrode 30b both have the electrode portion A and the electrode portion B, they can be formed, for example, by the following procedure. First, an electrode slurry containing an electrode material, an organic binder, and a dispersion medium is prepared, and the honeycomb structure 10 is immersed in the slurry from one end face 12a or the other end face 12b to a desired depth in the flow path direction of the honeycomb structure. The dispersion medium can be water, an organic solvent (e.g., toluene, xylene, ethanol, isopropanol, n-butanol, ethyl acetate, butyl acetate, terpineol, dihydroterpineol, texanol, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether) or a mixture thereof. The excess slurry on the outer periphery of the honeycomb structure 10 is removed by blowing and wiping. Thereafter, by drying the slurry, the electrode portion B can be formed on the surface of the partition wall 14 or the like, and the electrode portion A can be formed on one end face 12a or the other end face 12b of the honeycomb structure 10. The electrode portion A may be separately formed by the method described above. Drying can be performed, for example, while heating a heater element to a temperature of about 120 to 600 °C. The series of steps of immersion, slurry removal, and drying may be performed only once, but by repeating them a plurality of times, the electrode portion A and the electrode portion B having a desired thickness can be provided.

[0078] When the surface tension changes according to the viscosity of the slurry, the coating state by the electrode portions B at the side portions 13a and corner portions 13b of the partition walls 14 (the partition walls 14 and the outer peripheral wall 11 that partition and form the cells 13) that partition and form the cells 13 can be changed. For example, when covering the entire surface of the partition wall 14 as shown in FIGS. 1D and 2D, the viscosity of the electrode slurry may be made relatively low. When covering only the corner portions 13b of the partition wall 14 as shown in FIGS. 3A to 3D, the viscosity of the electrode slurry may be made relatively high. The differentiation of the differences among FIGS. 3A to 3D can be achieved, for example, by masking one end face 12a or the other end face 12b of the honeycomb structure 10 when the honeycomb structure 10 is immersed in the electrode slurry. As a masking method, for example, a method of attaching a resin sheet to one end face 12a or the other end face 12b of the honeycomb structure 10 and laser-drilling the resin sheet at a location corresponding to the cell 13 where the electrode portion B is to be formed can be mentioned.

[0079] Next, by forming the functional material-containing layer 20 on the surfaces such as the partition walls 14 of the heater element thus obtained, a heater element with a functional material-containing layer is obtained. The method for forming the functional material-containing layer 20 is not particularly limited. For example, it can be formed by the following steps. A heater element is immersed in a slurry containing a functional material, an organic binder, and a dispersion medium for a predetermined time, and excess slurry on the end face and outer periphery of the honeycomb structure 10 is removed by blowing and wiping. The dispersion medium can be water, an organic solvent (e.g., toluene, xylene, ethanol, isopropanol, n-butanol, ethyl acetate, butyl acetate, terpineol, dihydroterpineol, texanol, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether) or a mixture thereof. Then, the functional material-containing layer 20 can be formed on the surface of the partition wall 14 or the like by drying the slurry. Drying can be performed, for example, while heating the heater element to a temperature of about 120 to 600°C. The series of steps of immersion, slurry removal, and drying may be performed only once, but a functional material-containing layer 20 having a desired thickness can be provided on the surface of the partition wall 14 or the like by repeating the steps a plurality of times.

[0080] (3. Passenger Compartment Purification System) According to an embodiment of the present invention, a passenger compartment purification system including the above-described heater element with a functional material-containing layer is provided. The passenger compartment purification system can be suitably used for various vehicles such as automobiles.

[0081] FIG. 4 is a schematic diagram showing the configuration of a passenger compartment purification system according to an embodiment of the present invention. The passenger compartment purification system 1000 includes at least one heater element 1, 2, and a power source 200 such as a battery for applying a voltage to the heater elements 1, 2, and an inflow pipe 400 that communicates the passenger compartment with the inlet end faces of the heater elements 1, 2, and An outflow pipe 500 having a first path 500a that communicates the outlet end surfaces of the heater elements 1 and 2 with the passenger compartment, a blower 600 for allowing air from the passenger compartment to flow into the inlet end surfaces of the heater elements 1 and 2 via an inflow pipe 400, is provided.

[0082] In the passenger compartment purification system shown in FIG. 4, the heater elements 1 and 2 are arranged such that the inlet end surface is one end surface 12a and the outlet end surface is the other end surface 12b. However, the heater elements 1 and 2 can also be arranged such that the inlet end surface is the other end surface 12b and the outlet end surface is one end surface 12a.

[0083] In addition to the first path 500a, the outflow pipe 500 can have a second path 500b that communicates the outlet end surfaces of the heater elements 1 and 2 with the outside of the vehicle. Further, the outflow pipe 500 can have a switching valve 300 that can switch the flow of air flowing through the outflow pipe 500 between the first path 500a and the second path 500b.

[0084] The passenger compartment purification system 1000 has a first mode in which the applied voltage from the power supply 200 is turned off, the switching valve 300 is switched so that the air flowing through the outflow pipe 500 passes through the first path 500a, and the blower 600 is turned on, and a second mode in which the applied voltage from the power supply 200 is turned on, the switching valve 300 is switched so that the air flowing through the outflow pipe 500 passes through the second path 500b, and the blower 600 is turned on. can have operating modes.

[0085] The passenger compartment purification system 1000 can include a control unit 900 capable of performing switching between the first mode and the second mode. The control unit 900 can be configured, for example, to alternately execute the first mode and the second mode. By repeating the switching between the first mode and the second mode at a constant cycle, it becomes possible to stably discharge the components to be removed in the passenger compartment to the outside of the vehicle.

[0086] In the first mode, the purification of the cabin air is performed. Specifically, the air from the cabin flows in from the inlet end faces of the heater elements 1 and 2 through the inflow pipe 400, passes through the heater elements 1 and 2, and then flows out from the outlet end faces of the heater elements 1 and 2. The components to be removed from the cabin air are removed by being captured by the functional material while passing through the heater elements 1 and 2. The clean air flowing out from the outlet end faces of the heater elements 1 and 2 is returned to the cabin through the first path 500a of the outflow pipe 500.

[0087] In the second mode, the regeneration of the functional material is performed. Specifically, the air from the cabin flows in from the inlet end faces of the heater elements 1 and 2 through the inflow pipe 400, passes through the heater elements 1 and 2, and then flows out from the outlet end faces of the heater elements 1 and 2. The heater elements 1 and 2 generate heat by being energized, whereby the functional material carried on the heater elements 1 and 2 is heated. Therefore, the components to be removed captured by the functional material are detached or reacted from the functional material.

[0088] In order to promote the detachment of the components to be removed captured by the functional material, it is preferable to heat the functional material to a temperature equal to or higher than the detachment temperature according to the type of the functional material. For example, when using an adsorbent as the functional material, it is preferable to heat at least a part, preferably all, of the functional material to 70 to 150 °C, more preferably to 80 to 140 °C, and even more preferably to 90 to 130 °C. Also, it is desirable to perform the second mode for a time until the regeneration of the functional material is sufficiently performed. Although it depends on the type of the functional material, for example, when using an adsorbent as the functional material, in the second mode, the functional material is preferably heated in the above temperature range for 1 to 10 minutes, more preferably for 2 to 8 minutes, and even more preferably for 3 to 6 minutes.

[0089] Air from the passenger compartment flows out from the outlet end faces of the heater elements 1 and 2 while carrying the components to be removed that have detached from the functional material as it passes through the heater elements 1 and 2. The air containing the components to be removed that has flowed out from the outlet end faces of the heater elements 1 and 2 is discharged to the outside of the vehicle through the second path 500b of the outflow pipe 500.

[0090] The switching of the application voltage to the heater elements 1 and 2 between on and off is possible, for example, by electrically connecting the power source 200 and the pair of electrodes 30a, 30b of the heater elements 1 and 2 with an electric wire 810 and operating a power switch 910 provided therebetween. The operation of the power switch 910 can be executed by the control unit 900.

[0091] The switching of the ventilation fan 600 between on and off is possible, for example, by electrically connecting the control unit 900 and the ventilation fan 600 with an electric wire 820 or wirelessly and operating a switch (not shown) of the ventilation fan 600 by the control unit 900. The ventilation fan 600 can also be configured such that the ventilation volume can be changed by the control unit 900.

[0092] The switching of the switching valve 300 is possible, for example, by electrically connecting the control unit 900 and the switching valve 300 with an electric wire 830 or wirelessly and operating a switch (not shown) of the switching valve 300 by the control unit 900.

[0093] The switching valve 300 is not particularly limited as long as it is a valve that is driven electrically and has a function of switching the flow path, and examples include solenoid valves and motor-operated valves. In one embodiment, the switching valve 300 includes an opening / closing door 312 supported by a rotating shaft 310 and an actuator 314 such as a motor that rotates the rotating shaft 310. The actuator 314 is configured to be controllable by the control unit 900.

[0094] From the perspective of stably ensuring the above functions, it is desirable that the heater elements 1 and 2 be arranged at positions 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 elements 1 and 2 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 of the driving voltage is not particularly limited, but it is preferably 10V or more. If the driving voltage is less than 10V, the current during heating of the honeycomb structure 10 becomes large, so it is necessary to thicken the electric wire 810.

[0095] In the embodiment shown in FIG. 4, the ventilator 600 is installed upstream of the heater elements 1 and 2. More specifically, the ventilator 600 is installed in the middle of the inflow pipe 400 that communicates the heater elements 1 and 2 with the passenger compartment, and the air that has passed through the ventilator 600 flows in so as to be pushed against the heater elements 1 and 2. As an alternative method, the ventilator 600 may be installed downstream of the heater elements 1 and 2. In this case, the ventilator 600 can be installed, for example, in the middle of the outflow pipe 500, and the air that has passed through the inflow pipe 400 flows in so as to be sucked into the heater elements 1 and 2.

[0096] In another embodiment of the passenger compartment purification system 1000, a functional addition body 3 may be arranged adjacent to the downstream side of the heater elements 1 and 2 (see FIG. 5). Referring to FIGS. 6A to 6C, in one embodiment, the functional addition body 3 includes a honeycomb structure 10 having an outer peripheral wall 11 and a partition wall 14 that partitions and forms a plurality of cells 13 that form a flow path extending from one end face 12a that serves as an inlet end face to the other end face 12b that serves as an outlet end face, which is disposed inside the outer peripheral wall 11.

[0097] The honeycomb structure 10 of the functional addition body 3 may have the same configuration as described for the heater elements 1 and 2, including the shape and size of the honeycomb structure 10, the shape of the cells 13, the bonding layer, the thickness of the partition walls 14, the cell density, the cell pitch (or the aperture ratio of the cells), and the material. However, since air heated by the upstream heater elements 1 and 2 can flow into the functional addition body 3, it is not necessary for the functional addition body 3 itself to generate heat. For this reason, it is not necessary to provide a pair of electrodes on the functional addition body 3, nor is it necessary to configure the honeycomb structure 10 of the functional addition body 3 with a material having PTC characteristics. Therefore, the honeycomb structure 10 of the functional addition body 3 can be fabricated using various ceramics as the material. Among them, it is preferable that at least the partition walls 14 of the functional addition body 3 be made of cordierite for reasons such as heat transfer and ease of manufacturing.

[0098] In one embodiment, the functional addition body 3 can include a functional material-containing layer 20 provided on the surface of the partition walls 14 (in the case of the outermost peripheral cells 13, the partition walls 14 and the outer peripheral wall 11 that partition and form the outermost peripheral cells 13). Although not limited, in the functional addition body 3, the functional material-containing layer 20 provided on the surface of the partition walls 14 of the honeycomb structure 10 can have the same configuration as described for the heater elements 1 and 2, including the type, average thickness, and amount of the functional material. When the functional addition body 3 is arranged adjacent to the downstream side of the heater elements 1 and 2, it is not necessary to provide the functional material-containing layer 20 on the upstream heater elements 1 and 2. Also, when the functional material-containing layer 20 is provided on the upstream heater elements 1 and 2, the functional addition body 3 on the downstream side may be provided with a functional material-containing layer 20 that can exhibit a function different from that of the functional material-containing layer 20 of the heater elements 1 and 2. Of course, the functional addition body 3 on the downstream side may be provided with a functional material-containing layer that can exhibit the same function as the functional material-containing layer 20 of the upstream heater elements 1 and 2.

[0099] According to the passenger compartment purification system 1000 according to the embodiment shown in FIG. 5, since the upstream heater elements 1 and 2 can heat the air, the downstream functional addition body 3 does not need to be provided with a pair of electrodes. For this reason, the functional addition body 3 only needs to consider the optimization of the functional material-containing layer 20, and the honeycomb structure 10 can be simply configured.

[0100] When this concept is further developed, even if the heater element installed on the upstream side cannot widen the region in the direction in which the flow path that can effectively heat the functional material extends, by arranging the functional addition body 3 adjacent to the downstream side of the heater element, it can be understood that the overall ratio of the functional material that can be effectively utilized can be increased. That is, since the functional addition body 3 on the downstream side can be made to flow in the air that has already been heated by the heater element on the upstream side, there is no need to worry about the temperature near the inlet side of the functional addition body 3 becoming low. For this reason, the entire functional material possessed by the functional addition body 3 can be effectively utilized.

[0101] In this case, a functional material-containing layer may be provided also on the heater element on the upstream side, but it is preferable not to provide it in terms of increasing the overall ratio of the functional material that can be effectively utilized. Further, the heater element on the upstream side that can be used in this case can adopt a simple electrode arrangement. FIGS. 7A to 7C show a schematic perspective view and a cross-sectional view of an example of a heater element 4 having such a simple electrode arrangement. The heater element 4 includes a honeycomb structure 10 having an outer peripheral wall 11 and a partition wall 14 that partitions and forms a plurality of cells 13 that form a flow path extending from one end face 12a that serves as an inlet end face to the other end face 12b that serves as an outlet end face, which is disposed inside the outer peripheral wall 11. Further, the heater element 4 includes a first electrode 30a provided on one end face 12a that serves as an inlet end face and a second electrode 30b provided on the other end face 12b that serves as an outlet end face.

[0102] The honeycomb structure 10 of the heater element 4 can have the same configuration as described for the heater elements 1 and 2, including, but not limited to, the shape and size of the honeycomb structure 10, the shape of the cells 13, the joining layer, the thickness of the partition walls 14, the cell density, the cell pitch (or the opening ratio of the cells), and the material. Also, the first electrode 30a and the second electrode 30b of the heater element 4 can have the same configuration as the electrode portion A described for the heater elements 1 and 2, including, but not limited to, the material and the thickness. In the heater element 4, it is not necessary to provide electrodes or functional material-containing layers inside the cells 13. Therefore, the simple structure of the heater element 4 is also advantageous in reducing the pressure loss when air flows through the cells 13.

[0103] FIG. 8 is a schematic diagram showing the configuration of a vehicle interior purification system 2000 according to still another embodiment of the present invention based on the above concept. The vehicle interior purification system 2000 includes a heater element 4, a functional addition body 3 disposed adjacent to the downstream side of the heater element 4, a power source 200 for applying a voltage to the heater element 4, an inflow pipe 400 that communicates the vehicle interior with one end face 12a that serves as the inlet end face of the heater element 4, an outflow pipe 500 having a first path 500a that communicates the other end face 12b that serves as the outlet end face of the functional addition body 3 with the vehicle interior, a blower 600 for causing air from the vehicle interior to flow into one end face 12a that serves as the inlet end face of the heater element 4 through the inflow pipe 400, and is provided with.

[0104] Other configurations and operation modes of the vehicle interior purification system 2000 are the same as those described for the vehicle interior purification system 1000, and thus the description thereof is omitted.

[0105] (4. Simulation) The result of simulating the temperature distribution inside the honeycomb structure when heating while flowing air from one end face of the honeycomb structure to the other end face is shown.

[0106] [Specifications of the honeycomb structure] The specifications of the honeycomb structure used in the simulation were as follows. · Shape of the cross section and end face of the honeycomb structure perpendicular to the flow path direction: Quadrilateral · Shape of the cell perpendicular to the flow path direction: Square · Thickness of the partition wall: 0.1016 mm · Cell density: 62 cells / cm 2 · Cell pitch: 1.270 mm · Cell opening ratio: 0.85 · Size of the cross section of the honeycomb structure perpendicular to the flow path direction: 10 mm × 0.635 mm · Length of the honeycomb structure in the flow path direction: 10 mm · Volume resistivity of the material constituting the outer peripheral wall and the partition wall at 25°C: 14 Ω·cm (almost no change up to 120°C) · Curie point of the material constituting the outer peripheral wall and the partition wall: 120°C (assuming barium titanate) · Density of the material constituting the outer peripheral wall and the partition wall: 4500 kg / m 3 · Specific heat of the material constituting the outer peripheral wall and the partition wall: 590 J / kg / K

[0107] [Heating test] A heating test was simulated to investigate the temperature distribution in the steady state inside the honeycomb structure when air (initial temperature = 20°C) was circulated through the cells of the honeycomb structure at 0.13 m / sec from one end face to the other end face while applying a constant voltage of 12 V between one end face and the other end face of the honeycomb structure. Fluent Ver2021-R1 (manufactured by Ansys, Inc.) was used for the simulation. The results are shown in Fig. 9. From these results, it can be seen that in the region from the inlet side (one end face) to about 1 / 4 of the length of the honeycomb structure, it is difficult to heat to 60 °C or higher, which is advantageous for regeneration, even when the functional material is supported, indicating that it cannot be effectively utilized. On the other hand, in the region from the outlet side (the other end face) to about 1 / 4 of the length of the honeycomb structure, it is heated to a temperature of 100 °C or higher, and it can be seen that in about 1 / 2 of the region, it is heated to a temperature of 80 °C or higher.

[0108] Therefore, it can be understood that by shortening the distance between the electrodes, it is advantageous to reduce the electrical resistance between the electrodes and widen the region in the direction in which the flow path that can be effectively heated extends. Further, when shortening the distance between the electrodes, it is understood that when providing the electrode portion B only on the outlet side where it is easily heated, or when providing the electrode portion B on both the inlet side and the outlet side, making the electrode portion B on the outlet side longer can effectively heat the inlet side where it is difficult to heat.

Explanation of reference numerals

[0109] 1: Heater element 2: Heater element 3: Functional addition body 4: Heater element 10: Honeycomb structure 11: Outer peripheral wall 12a: One end face 12b: The other end face 13: Cell 13a: Side portion 13b: Corner portion 14: Partition wall 20: Functional material-containing layer 30a: First electrode 30b: Second electrode 200: Power supply 300: Switching valve 310: Rotation shaft 312: Opening / closing door 314: Actuator 400: Inflow pipe 500: Outflow pipe 500a: First path 500b: Second path 600: Blower 810: Electric wire 820: Electric wire 830: Electric wire 900: Control unit 910: Power switch 1000: Passenger compartment purification system 2000: Passenger compartment purification system

Claims

[Claim 1] A honeycomb structure having an outer peripheral wall and partition walls disposed inside the outer peripheral wall to define a plurality of cells that form flow paths extending from one end face to the other end face, wherein at least the partition walls are made of a material having PTC characteristics; and a pair of electrodes composed of a first electrode and a second electrode; Equipped with A heater element in which the first electrode and the second electrode satisfy either of the following conditions (i) or (ii): (i) the first electrode is provided on the one end surface; the second electrode has an electrode portion A provided on the other end face, and an electrode portion B connected to the electrode portion A and provided on the surface of the partition wall over a predetermined length from the other end face in the direction in which the flow channel extends; (ii) the first electrode has an electrode portion A provided on the one end face, and an electrode portion B connected to the electrode portion A and provided on the surface of the partition wall over a predetermined length from the one end face in the direction in which the flow channel extends, The second electrode has an electrode portion A provided on the other end face, and an electrode portion B connected to the electrode portion A and provided on the surface of the partition wall over a predetermined length from the other end face in the direction in which the flow path extends.

Images