JP7335994B2 - Heating element and its use - Google Patents

Description

The present invention relates to heater elements and methods of use thereof .

From the viewpoint of protecting the global environment , there is an increasing demand for reducing CO ₂ emissions . Therefore , a vapor compression heat pump has been used to effectively use electric power for heating (Patent Document 1). Vapor compression heat pumps compress the medium with an electric compressor and use the heat absorption and heat dissipation in the phase change between the gas phase and the liquid phase to pump heat from the cold outside air into the room . On the other hand, there is an advantage that electrical energy can be used more effectively because the amount of heat that can be pumped is large.

A heater using Joule heat generated by electrical resistance when energized is also known (Patent Document 2). In heaters using Joule heat, a heating element is arranged in a heat exchanger to heat a fluid passing through the heat exchanger. A heater using Joule heat is effective, for example, in applications such as vehicle interior heating, when rapid heating is required at the start of a vehicle or when the outside air temperature is extremely low. As the heating element, it is known to use a PTC material to prevent thermal runaway.

On the other hand, heaters using honeycomb-shaped heater elements (hereinafter referred to as "honeycomb heaters") are known. For example, Patent Literature 3 describes a honeycomb structure for electrical heat generation that is effective for heating exhaust gases from gasoline engines, diesel engines, and combustion devices. Furthermore, US Pat. No. 6,200,000 also describes an electrically heatable honeycomb body for treating the exhaust gas of an internal combustion engine. Patent Document 4 discloses an electrically heatable honeycomb body having cavities through which a fluid can flow and having at least one current distribution structure, which current distribution structure can be connected to a power supply via a current supply, At least one of a) the current supply and b) the current distribution structure has at least one control element made of a positive temperature coefficient (PTC) material, the control element having a fluid flowing through the honeycomb body. An electrically heatable honeycomb body is described, which is characterized in that it is in at least thermal contact with the .

JP 2017-30724 A Japanese Patent Publication No. 2015-519260 Japanese Patent No. 5261256 JP 2008-215351 A

Although heat pumps are superior in terms of thermal efficiency, heat pumps have problems in that they are difficult to operate when the outside air is extremely cold, and that it is difficult to rapidly warm the passenger compartment when the vehicle is started. Therefore, we thought it would be practical to use a heater that uses Joule heat as a supplement when rapid heating is required when starting a vehicle or when the outside temperature is extremely low, while a heat pump is used as the main heating source. be done.

However, conventional heaters using Joule heat tend to be large , and there is a problem of pressing the space . Therefore, it would be desirable to provide a more compact heater. In this respect, the honeycomb heater can increase the heat transfer area per unit volume, which is considered to contribute to the miniaturization of the heater. However, the honeycomb structure for electric heat generation described in Patent Document 3 generates excessive heat because the honeycomb structure has NTC characteristics, and is not suitable as a heater for a narrow space such as for heating a passenger compartment. It is difficult. In addition, in the technique described in Patent Document 4, the temperature of the control element made of the PTC material does not follow the temperature of the honeycomb body, and it cannot be said that the effect of suppressing excessive heat generation is sufficient as a heater for heating the passenger compartment. Ta. For the reasons described above, conventionally, there has not yet existed a compact honeycomb heater that can be suitably used for heating the cabin of a vehicle such as an automobile or a train.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heater element which can be miniaturized and in which the effect of suppressing excessive heat generated by a PTC material is improved. Another aspect of the present invention is to provide a method of using such a heater element .

In the honeycomb heater described in Patent Document 4, since the control element made of the PTC material is arranged closer to the outer peripheral side of the honeycomb structure than the current distribution structure (see FIGS. 2 and 3 of Patent Document 4), Heat from the honeycomb structure is transferred through the current distribution structure to the control elements made of PTC material, resulting in slow response speed. For this reason, in the technique of Patent Document 4, even if the honeycomb structure reaches an overheated state, the heat is not quickly transferred to the PTC material, so excessive heat generation tends to occur. Based on such findings, the inventors of the present invention proposed that a PTC thermistor should be connected to the honeycomb structure and the electrode portion (corresponding to the current distribution structure in Patent Document 4) in order to increase the response speed when the honeycomb structure reaches an overheated state. ), and completed the present invention exemplified below.

[1]
A columnar honeycomb structure capable of generating heat by electricity, having an outer peripheral wall and partition walls disposed on the inner peripheral side of the outer peripheral wall and partitioning and forming a plurality of cells forming fluid flow paths from one bottom surface to the other bottom surface. ,
a pair of electrode portions formed so as to face the outer peripheral side of the outer peripheral side wall of the columnar honeycomb structure portion;
a PTC thermistor disposed so as to cover the outer peripheral sidewall of the columnar honeycomb structure at a position sandwiched between the outer peripheral sidewall of the columnar honeycomb structure and at least one of the pair of electrode units;
with
The size of each bottom area of the columnar honeycomb structure is 300 cm ² or less.
heater element.
[2]
A ratio (S/V) of the total area S of the portion where the outer peripheral side wall of the columnar honeycomb structure is covered with the PTC thermistor to the volume V of the columnar honeycomb structure (S/V) is 0.1 cm ² /cm ³ or more. The heater element according to [1].
[3]
The heater element according to [2], wherein the S/V is 0.2 cm ² /cm ³ or more.
[4]
The heater element according to any one of [1] to [3], wherein the plurality of cells are arranged radially in a cross section in a direction perpendicular to the fluid flow path of the plurality of cells.
[5]
The heater element according to any one of [1] to [4], wherein the PTC thermistor is made of a PTC material having a Curie point of 100° C. or higher and 250° C. or lower.
[6]
The heater element according to any one of [1] to [5], wherein the columnar honeycomb structure contains Si-bonded SiC.
[7]
The heater according to any one of [1] to [6], wherein the at least one electrode portion of the PTC thermistor is arranged so that there is no portion in direct contact with the outer peripheral side wall of the columnar honeycomb structure portion. tar element.
[8]
PTC thermistors are disposed at positions sandwiched between the outer peripheral sidewall of the columnar honeycomb structure portion and the electrode portions of the pair of electrode portions,
An electrical insulating layer located between a part of at least one PTC thermistor and the outer peripheral wall of the columnar honeycomb structure, wherein the current distribution in the honeycomb structure when a voltage is applied to the pair of electrodes. The heater element according to any one of [1] to [7], further comprising an electrical insulating layer extending at a position capable of enhancing uniformity.
[9]
The total area S of the portion where the outer peripheral side wall is covered with the PTC thermistor and the area Se obtained by subtracting the area of the portion where the outer peripheral side wall is in contact with the electrical insulating layer from the total area S are 0.3≤Se/S< 1. The heater element according to [8].
[10]
The heater element according to any one of [1] to [9], wherein the columnar honeycomb structure has a height of 40 mm or less.
[1 1 ]
It has an outer peripheral side wall, an inner peripheral side wall, and a partition wall disposed between the outer peripheral side wall and the inner peripheral side wall and partitioning and forming a plurality of cells that form fluid flow paths from one bottom surface to the other bottom surface. a hollow honeycomb structure that can generate heat by electricity;
an outer electrode portion formed on the outer peripheral side of the outer peripheral side wall of the hollow honeycomb structure portion;
an inner electrode portion formed on the inner peripheral side of the inner peripheral side wall of the hollow honeycomb structure;
as well as,
disposed so as to cover the inner peripheral sidewall of the hollow honeycomb structure at a position sandwiched between the inner peripheral sidewall of the hollow honeycomb structure and the inner electrode portion; and/or a PTC thermistor disposed so as to cover the outer peripheral side wall of the hollow honeycomb structure at a position sandwiched between the outer peripheral side wall of the hollow honeycomb structure and the outer electrode section;
with
The size of each bottom area of the hollow honeycomb structure is 300 cm ² or less.
heater element.
[1 2 ]
The ratio (S/V) of the total area S of the portion where the inner peripheral sidewall and/or the outer peripheral sidewall of the hollow honeycomb structure is covered with the PTC thermistor to the volume V of the hollow honeycomb structure (S/V) is 0. The heater element according to [1 1 ], which is 1 cm ² /cm ³ or more.
[1 3 ]
The heater element according to [1 2 ], wherein the S/V is 0.2 cm ² /cm ³ or more.
[ 14 ]
The heater element according to any one of [1 1 ] to [1 3 ], wherein the plurality of cells are arranged radially in a cross section perpendicular to the flow path of the fluid of the plurality of cells.
[1 5 ]
The heater element according to any one of [1 1 ] to [1 4 ], wherein the PTC thermistor is made of a PTC material having a Curie point of 100° C. or higher and 250° C. or lower.
[ 16 ]
The heater element according to any one of [1 1 ] to [1 5 ], wherein the hollow honeycomb structure contains Si-bonded SiC.
[ 17 ]
When the PTC thermistor is arranged so as to cover the inner peripheral sidewall of the hollow honeycomb structure, the PTC thermistor has a portion where the inner electrode directly contacts the inner peripheral sidewall of the hollow honeycomb structure. When the PTC thermistor is arranged so as to cover the outer peripheral wall of the hollow honeycomb structure, the outer electrode portion of the PTC thermistor covers the outer peripheral wall of the hollow honeycomb structure. A heater element according to any one of [1 1 ] to [1 6 ] arranged so that there are no parts in direct contact.
[18]
The heater element according to any one of [11] to [17], wherein the hollow honeycomb structure has a height of 40 mm or less.
[ 19 ]
A method of using the heater element according to any one of [1] to [1 8 ], wherein a voltage of 200 V or more is applied between the two electrodes.
[ 20 ]
A method of using the heater element of [ 19 ] comprising passing a gas from -60°C to 20°C through the cell .

According to the heater element according to one embodiment of the present invention, the honeycomb structure can increase the heat transfer area per unit volume, so that the size of the heater element can be reduced. Further, according to the heater element according to one embodiment of the present invention, since the PTC thermistor is sandwiched between at least one of the electrode portions and the outer peripheral sidewall or the inner peripheral sidewall of the honeycomb structure portion, the honeycomb structure can be obtained. The heat of the part is quickly transferred to the PTC thermistor. This makes it possible to improve the effect of suppressing excessive heat generation by the PTC thermistor.

FIG. 4 is a schematic perspective view of the heater element according to the first embodiment of the present invention when the honeycomb structure has a rectangular bottom surface. FIG. 4 is a schematic perspective view of the heater element according to the first embodiment of the present invention when the honeycomb structure has a square bottom surface. FIG. 4 is a schematic perspective view of the heater element according to the first embodiment of the present invention when the bottom surface of the honeycomb structure portion is oval. 1 is a schematic perspective view of the heater element according to the first embodiment of the present invention when the honeycomb structure has a square bottom surface and an electrical insulating layer is sandwiched between the outer peripheral side wall of the honeycomb structure and the PTC thermistor; FIG. It is a diagram. FIG. 4 is a schematic perspective view of the heater element according to the first embodiment of the present invention when the honeycomb structure has a circular bottom surface. FIG. 4 is a partial schematic diagram showing radially arranged cells of the heater element according to the first embodiment of the present invention, when observed from a direction perpendicular to the flow path of the cells. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the structural example of the heater for a vehicle interior heating which concerns on this invention.

Next, embodiments of the present invention will be described in detail with reference to the drawings. It is understood that the present invention is not limited to the following embodiments, and that design changes, improvements, etc., can be made as appropriate based on the ordinary knowledge of those skilled in the art without departing from the scope of the present invention. should.

(1. Heater element)
INDUSTRIAL APPLICABILITY The heater element according to the present invention can be suitably used as a heater element for heating the cabin of a vehicle. Vehicles include, but are not limited to, automobiles and trains. Motor vehicles include, but are not limited to, gasoline vehicles, diesel vehicles, fuel cell vehicles, electric vehicles and plug-in hybrid vehicles. INDUSTRIAL APPLICABILITY The heater element according to the present invention is particularly suitable for use in vehicles without internal combustion engines, such as electric vehicles and trains.

(1.1 First Embodiment of Heater Element)
1-1, 1-2 and 1-3 each show a schematic perspective view of a heater element 100 according to a first embodiment of the present invention. The heater element 100 has an outer peripheral side wall 112 and partition walls 113 which are arranged on the inner peripheral side of the outer peripheral side wall 112 and partition and form a plurality of cells 115 forming fluid flow paths from one bottom surface 114 to the other bottom surface 116 . and a columnar honeycomb structure capable of generating heat by electricity. The heater element 100 also includes a pair of electrode portions 120 formed to face the outer peripheral side of the outer peripheral side wall 112 of the columnar honeycomb structure. Further, the heater element 100 covers the outer peripheral side wall 112 of the columnar honeycomb structure at a position sandwiched between the outer peripheral side wall 112 of the columnar honeycomb structure and at least one electrode section 120 of the pair of electrode sections 120 . A PTC thermistor 122 is arranged to.

(1.1.1 Columnar honeycomb structure part)
The columnar honeycomb structure part has, for example, a polygonal prism shape having a polygonal bottom surface (quadrilateral (rectangular (see FIG. 1-1)), square (see FIG. 1-2), pentagon, hexagon, heptagon, octagon, etc.), It may have any shape, such as a columnar shape (columnar shape) with a circular bottom (see FIG. 2) or a columnar shape with an oval bottom (see FIGS. 1-3). If the base is polygonal, the corners may be chamfered. Also, the columnar honeycomb structure can be hollow.

Although there is no limitation on the shape of the cells in the cross section perpendicular to the flow path of the cells, it is preferably quadrangular (rectangular, square), hexagonal, octagonal, or a combination of two or more of these. Among these, squares and hexagons are preferred. By making the cell shape as described above, the pressure loss when the gas is caused to flow through the honeycomb structure can be reduced. For example, in the columnar honeycomb structure portion of the heater element 100 shown in FIG. 1-1, the shape of the cells in the cross section perpendicular to the flow path of the cells is square.

A plurality of cells may be arranged radially in a cross section perpendicular to the flow path of the cells. FIG. 2-2 shows an example in which a plurality of cells are arranged radially, which relates to a second embodiment described later. In the example shown in FIG. 2-2, each of the plurality of cells has a pair of partition walls extending from the center side to the outer peripheral side of the columnar honeycomb structure portion, and central and outer peripheral partition walls connecting the pair of partition walls. and are partitioned by. More specifically, in the example shown in FIG. 2-2(a), in the cross section perpendicular to the flow path of the cells, each of the plurality of cells 115 extends from the center side of the columnar honeycomb structure toward the outer peripheral side. It is partitioned by a pair of extending linear partitions 113a and a pair of concentric arcuate partitions 113b. In the embodiment shown in FIG. 2-2(b), each of the plurality of cells 115 has a hexagonal shape in the cross section perpendicular to the flow path of the cells, and extends from the center side to the outer peripheral side of the columnar honeycomb structure. It is partitioned by a pair of extending linear partition walls 113c and polygonal linear partition walls 113d on the central side and the outer peripheral side that connect the pair of partition walls 113c. In FIG. 2-2, portions indicated by dotted lines mean that a plurality of cells are arranged radially in the same manner as the illustrated portion.

From the viewpoint of securing the gas flow rate, the lower limit of the size of each bottom area of the columnar honeycomb structure (excluding the portion if the columnar honeycomb structure is hollow) may be 50 cm ² or more. It is preferably 70 cm ² or more, more preferably 100 cm ² or more. From the viewpoint of making the heater element compact, the upper limit of the bottom area of each columnar honeycomb structure is preferably 300 cm ² or less, more preferably 200 cm ² or less, and further preferably 150 cm ² or less. is even more preferred. The size of each base area of the columnar honeycomb structure can be, for example, 50 to 300 cm ² .

From the viewpoint of making the heater element compact, the upper limit of the height of the columnar honeycomb structure (the length of the flow path of each cell) is, for example, preferably 40 mm or less, more preferably 20 mm or less, and 10 mm or less. is even more preferable, and it is even more preferable to be 5 mm or less. From the viewpoint of ensuring heating performance and strength, it is preferable that the lower limit of the height of the columnar honeycomb structure portion (flow channel length of each cell) is 3 mm or more. The height of the columnar honeycomb structure (flow path length of each cell) can be, for example, 3 to 40 mm.

It is advantageous to reduce the thickness of the partition wall from the viewpoint of suppressing the initial current from becoming excessive at the time of energization and from the viewpoint of suppressing the output of the blower by suppressing the ventilation resistance. Therefore, the upper limit of the average thickness of the partition walls 113 in the honeycomb structure is preferably 0.15 mm or less, more preferably 0.13 mm or less, and even more preferably 0.10 mm or less. However, from the viewpoint of ensuring the strength of the honeycomb structure, the lower limit of the average thickness of the partition walls 113 is preferably 0.02 mm or more, more preferably 0.04 mm or more, and more preferably 0.06 mm or more. It is even more preferred to have

In the present invention, the thickness of the partition wall refers to the length of a line segment that crosses the partition wall when connecting the centers of gravity of adjacent cells in a cross section perpendicular to the flow path of the cell. The average partition wall thickness refers to the average thickness of all partition walls.

The columnar honeycomb structure part preferably has a cell density of 40 cells/cm ² or more, more preferably 80 cells/cm ² or more. By limiting the cell density to the above range in combination with the preferred range of the average thickness of the partition walls described above, the heater element can be made suitable for rapid heating while suppressing the initial current. From the viewpoint of suppressing ventilation resistance and output of the blower, the columnar honeycomb structure preferably has a cell density of 150 cells/cm ² or less, more preferably 120 cells/cm ² or less. In the present invention, the cell density of the columnar honeycomb structure is obtained by dividing the number of cells by the area of each bottom surface of the columnar honeycomb structure (excluding that portion if the columnar honeycomb structure is hollow). value.

From the viewpoint of suppressing ventilation resistance, a larger open area ratio (OFA) is more advantageous. Therefore, the lower limit of the open area ratio at each bottom surface of the columnar honeycomb structure body is preferably 0.7 or more, more preferably 0.75 or more, and even more preferably 0.8 or more. From the viewpoint of ensuring thermal conductivity, the upper limit of the open area ratio at each bottom surface of the columnar honeycomb structure body is preferably 0.9 or less, more preferably 0.88 or less, and more preferably 0.85 or less. It is even more preferred to have In the present invention, the open area ratio at each bottom surface of the columnar honeycomb structure body is defined as the area of each bottom surface including the cell openings (if the columnar honeycomb structure body is hollow, exclude that portion). refers to the ratio of the area of the opening of

The material of the columnar honeycomb structure is not particularly limited as long as it can generate heat when energized, and metals, ceramics, and the like can be used. A columnar honeycomb structure in which gas such as outside air or vehicle interior air is heated during the period from when the gas flows in from one bottom surface of the columnar honeycomb structure part, passes through the plurality of cells 115, and flows out from the other bottom surface. It can be heated by heat transfer from the part. In particular, from the viewpoint of achieving both heat resistance and conductivity, the material of the columnar honeycomb structure portion preferably contains Si-bonded SiC or SiC as a main component, and is more preferably Si-bonded SiC or SiC. Tantalum silicide (TaSi ₂ ) and/or chromium silicide (CrSi ₂ ) can also be blended in order to lower the electrical resistivity of the columnar honeycomb structure. The fact that the columnar honeycomb structure contains Si-bonded SiC as a main component means that the columnar honeycomb structure contains Si-bonded SiC (total mass) in an amount of 90% by mass or more of the entire honeycomb structure. Here, the Si-bonded SiC contains silicon carbide particles as an aggregate and silicon as a binding material for binding the silicon carbide particles. The fact that the columnar honeycomb structure contains SiC as a main component means that the columnar honeycomb structure contains 90% by mass or more of SiC (total mass) of the entire honeycomb structure.

A PTC (Positive Temperature Coefficient) material typified by barium titanate can be used as the material of the columnar honeycomb structure. In other words, the columnar honeycomb structure itself may have a characteristic that when the temperature rises and exceeds the Curie point, the resistance value rises sharply, making it difficult for electricity to flow. However, from the viewpoint of selecting a honeycomb material that satisfies thermal conductivity, strength, and appropriate electrical resistance, Si-bonded SiC or a material having NTC (Negative Temperature Coefficient) characteristics such as SiC is generally preferable.

(1.1.2 Electrodes)
The heater element 100 includes a pair of electrode portions 120 formed to face the outer peripheral side of the outer peripheral side wall 112 of the columnar honeycomb structure portion. When a voltage is applied between the pair of electrode portions, the columnar honeycomb structure portion is energized and can generate heat by Joule heat. In a preferred embodiment, a pair of electrode portions 120 are provided in a strip shape on the outer peripheral side of the outer peripheral side wall 112 of the honeycomb structure portion in the direction of the flow path of the cells across the central axis of the honeycomb structure portion. As a result, the honeycomb structure can suppress unevenness in current flowing through the honeycomb structure when a voltage is applied between the pair of electrode portions 120, and can suppress uneven temperature distribution in the honeycomb structure. . An electric wire can be connected to each electrode portion 120 by diffusion bonding, a mechanical pressure mechanism, welding, or the like, and power can be supplied from a battery through an electric wire, for example.

Each electrode part 120 can use an electrode containing at least one selected from, for example, Cu, Ag, Al and Si. An ohmic electrode capable of making ohmic contact with a PTC thermistor, which will be described later, can also be used. The ohmic electrode contains, for example, at least one selected from 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. ohmic electrodes can be used.

Each of the pair of electrode portions 120 is preferably formed in a band shape extending from one bottom surface to the other bottom surface in the direction of the flow path of the cells of the columnar honeycomb structure. In this way, since the pair of electrode portions 120 are arranged across the bottom surfaces of the columnar honeycomb structure portion, when a voltage is applied between the pair of electrode portions 120, the current flowing through the columnar honeycomb structure portion is reduced. bias can be suppressed more effectively. By suppressing the unevenness of the current flowing through the columnar honeycomb structure, the unevenness of the temperature distribution in the honeycomb structure can be suppressed more effectively. “Each of the pair of electrode portions is formed in a band shape extending from one bottom surface to the other bottom surface in the flow channel direction of the cells of the columnar honeycomb structure portion” means that one cell flow direction end of each electrode portion 120 contact with the periphery of one bottom surface of the columnar honeycomb structure, and the other end in the cell flow path direction of each electrode member 120 is in contact with the periphery of the other bottom of the columnar honeycomb structure.

(1.1.3 PTC thermistor)
The heater element 100 is sandwiched between the outer peripheral side wall 112 of the columnar honeycomb structure and at least one electrode portion 120 of the pair of electrode portions 120 so as to cover the outer peripheral side wall 112 of the columnar honeycomb structure. It has a PTC thermistor 122 disposed thereon. With such a sandwich structure, the heat from the columnar honeycomb structure is quickly transferred to the PTC thermistor 122. Therefore, when the columnar honeycomb structure overheats, the PTC thermistor 122 is quickly activated to Through 120, it becomes possible to suppress the current passing through the columnar honeycomb structure. The PTC thermistor 122 may be provided only at a position sandwiched between the outer peripheral side wall 112 of the columnar honeycomb structure and one electrode part 120 of the pair of electrode parts 120, or may be provided between the outer peripheral side wall 112 of the columnar honeycomb structure and the electrode part 120. It may be provided at a position sandwiched between both electrode portions 120 of the pair of electrode portions 120 . When PTC thermistors are provided for both electrode sections, it is preferable to separate the PTC thermistors for the respective electrode sections from each other in order to prevent current imbalance.

From the viewpoint of enhancing the overheating prevention performance, the lower limit of the ratio (S/V) of the total area S of the portion where the outer peripheral side wall 112 of the columnar honeycomb structure is covered with the PTC thermistor 122 to the volume V of the columnar honeycomb structure is It is preferably 0.1 cm ² /cm ³ or more, more preferably 0.2 cm ² /cm ³ or more, and even more preferably 0.4 cm ² /cm ³ or more. In addition, although it is possible to increase the S/V by making the shape more complex than covering all the side surfaces of a simple shape such as a circular cross section or a square cross section, the current distribution becomes complicated and the temperature distribution tends to become non-uniform. Therefore, from the viewpoint of maintaining a simple shape, the upper limit of S/V is preferably 0.8 cm ² /cm ³ or less, more preferably 0.7 cm ² /cm ³ or less, and more preferably 0.6 cm ^{2 .} /cm ³ or less is even more preferable. Here, the volume V of the honeycomb refers to a volume value measured based on the external dimensions of the columnar honeycomb structure (hollow portions are not included in the volume V). In addition, when a plurality of PTC thermistors are installed, the total area S refers to the total area of the portion where the outer peripheral side wall of the columnar honeycomb structure is covered by the plurality of PTC thermistors.

If the total area S of the portion where the outer peripheral side wall of the columnar honeycomb structure is covered with the PTC thermistors is increased in order to increase the S/V, the distance between the PTC thermistors arranged for the respective electrode portions is shortened. A portion with a short electric conduction path is formed in the honeycomb structure. In this case, since the electrical resistance is low, the current flows intensively in that portion, causing a localized high temperature and non-uniform temperature. Therefore, if the portion of the honeycomb structure portion where the electric conduction path is shortened is insulated with respect to electric conduction and the heat conduction is allowed, the heat is transferred well to the PTC thermistor, so that the overheating prevention effect is excellent, and Since a short portion of the electric conduction path is not formed, the effect of improving heat generation uniformity in the honeycomb structure is obtained.

Accordingly, in one embodiment, the heater element according to the present invention is
PTC thermistors are disposed at positions sandwiched between the outer peripheral sidewall of the columnar honeycomb structure portion and the electrode portions of the pair of electrode portions,
An electrical insulating layer located between a part of at least one PTC thermistor and the outer peripheral wall of the columnar honeycomb structure, wherein the current distribution in the honeycomb structure when a voltage is applied to the pair of electrodes. It further comprises an electrically insulating layer extending at a location where uniformity can be enhanced.

In a preferred embodiment, a pair of electrical insulating layers are arranged between a part of each PTC thermistor and the outer peripheral side wall of the columnar honeycomb structure.

As for the arrangement position of the electrical insulating layer that can improve the uniformity of the current distribution in the honeycomb structure when a voltage is applied to the pair of electrodes, the PTC thermistors arranged for the respective electrode parts are placed around each other. The edge of each PTC thermistor that is closest in direction is included. The electrically insulating layer may be provided on one edge of each PTC thermistor or may be provided on both edges of each PTC thermistor. Here, the circumferential direction refers to a direction perpendicular to the height direction (cell extending direction) of the honeycomb structure.

The ratio (Se/S) of the area Se obtained by subtracting the area of the portion where the outer peripheral side wall is in contact with the electrical insulating layer from the total area S to the total area S of the portion where the outer peripheral side wall is covered with the PTC thermistor (Se/S) is preferably smaller. , the effect of improving heat generation uniformity in the honeycomb structure is likely to be obtained. On the other hand, if Se/S is too small, the effect of preventing excessive temperature rise tends to decrease. Therefore, in a preferred embodiment, 0.3≦Se/S<1, in a more preferred embodiment, 0.3≦Se/S≦0.8, and in a still more preferred embodiment, 0.3≦Se/S≦0.8. 4≦Se/S≦0.7 is satisfied.

For example, FIG. 1-4 shows a modification of the embodiment of FIG. 1-2 in which an electrical insulating layer 118 is partially sandwiched between the outer peripheral sidewall 112 of the honeycomb structure and the PTC thermistor 122. It is shown. In the embodiment of FIGS. 1-4, a pair of opposing PTC thermistors 122 each extend in an L-shaped cross-section on the voltage application surface of the outer peripheral sidewall 112 and the adjacent side surface of the outer peripheral sidewall 112 perpendicular to the voltage application surface. is set. The electrical insulating layer 118 is placed between each PTC thermistor 122 and the outer peripheral sidewall 112 so as to cover the adjacent side surface of the outer peripheral sidewall 112 .

_The material _{of the} electrical _{insulating layer 118} is not particularly _{limited .} things are mentioned. These may be used alone or in combination of two or more. A method for forming the electrical insulating layer 118 includes a dry method and a wet method. Examples of dry methods include CVD (chemical vapor deposition), PVD (physical vapor deposition), ion plating, sputtering and electrostatic spraying. Examples of the wet method include a method in which a slurry for forming an electrical insulating layer is applied to a predetermined position on the outer peripheral side wall, dried, and then fired.

The PTC thermistor 122 is preferably arranged such that at least one electrode portion 120 does not have a portion in direct contact with the outer peripheral side wall 112 of the columnar honeycomb structure portion. According to this configuration, when the PTC thermistor is activated, it is possible to completely cut off the current path.

From the viewpoint of having PTC characteristics, the PTC thermistor 122 is preferably ceramics composed of a material containing barium titanate as a main component, and is ceramics composed of a material containing 70% by mass or more of barium titanate. More preferably, it is a ceramic composed of a material containing 90% by mass or more of barium titanate. The ceramic preferably contains one or more additives such as rare earth elements in order to obtain desired PTC characteristics. Additives include semiconducting agents such as Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; side shifters, high temperature side shifters such as (Bi--Na), (Bi--K), property improvers such as Mn, metal oxides such as vanadium oxide and yttrium oxide (especially oxides of rare earth elements) , and conductive powders such as carbon black and nickel. As another PTC material, there is a composite material containing cristobalite phase SiO ₂ as a base material and conductive filler. Tridymite phase SiO ₂ , cristobalite phase _{AlPO 4 and} tridymite phase AlPO ₄ can also be used instead of the cristobalite phase SiO 2 base material.

From the viewpoint of efficiently heating the air for heating, the lower limit of the Curie point of the material forming the PTC thermistor 122 is preferably 100° C. or higher, more preferably 125° C. or higher, and 150° C. or higher. It is even more preferred to have In addition, the upper limit of the Curie point of the material that constitutes the PTC thermistor 122 is preferably 250° C. or less, more preferably 225° C. or less, from the viewpoint of safety as a component placed in or near the vehicle compartment. is more preferable, and 200° C. or less is even more preferable.

The Curie point of the material forming the PTC thermistor 122 can be adjusted by the type and amount of shifter added. For example, the Curie point of barium titanate (BaTiO ₃ ) is about 120° C., but the Curie point can be shifted to the low temperature side by substituting a portion of Ba and Ti with one or more of Sr, Sn and Zr. can be done. Further, by substituting part of Ba with Pb, the Curie temperature can be shifted to the high temperature side.

In the present invention, the Curie point is measured by the following method. Attach the sample to the sample holder for measurement, install it in a measuring tank (eg: MINI-SUBZERO MC-810P manufactured by Tabai Espec Co., Ltd.), and measure the change in the electrical resistance of the sample with respect to the temperature change when the temperature is raised from 10 ° C. It is measured using a DC resistance meter (eg, multimeter 3478A manufactured by YHP). The temperature at which the resistance value becomes twice the resistance value at 20° C. according to the electrical resistance-temperature plot obtained by the measurement is defined as the Curie point.

The lower limit of the average thickness of the PTC thermistor 122 is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 2 mm or more, from the viewpoint of enhancing overheat prevention performance. The upper limit of the average thickness of the PTC thermistor 122 is preferably 50 mm or less, more preferably 40 mm or less, and more preferably 30 mm or less from the viewpoint of not excessively increasing the initial electrical resistance value as a whole. more preferred. The average thickness of the PTC thermistor 122 is obtained as an average value when the thickness of the PTC thermistor 122 is arbitrarily measured at 10 or more points in a cross section perpendicular to the flow path of the cell.

(1.2 Second Embodiment of Heater Element)
FIG. 2 shows a schematic perspective view of a heater element 200 according to a second embodiment of the invention. The heater element 200 includes an outer peripheral sidewall 112, an inner peripheral sidewall 117, and a plurality of cells 115 disposed between the outer peripheral sidewall 112 and the inner peripheral sidewall 117 and forming fluid flow paths from one bottom surface to the other bottom surface. and partition walls 113 that partition and form a hollow honeycomb structure capable of electrically generating heat. The heater element 200 includes an outer electrode portion 120a formed on the outer peripheral side of the outer peripheral side wall 112 of the hollow honeycomb structure portion and an inner electrode portion 120a formed on the inner peripheral side of the inner peripheral side wall 117 of the hollow honeycomb structure portion. 120b. Further, the heater element 200 is disposed so as to cover the inner peripheral side wall 117 of the hollow honeycomb structure at a position sandwiched between the inner peripheral side wall 117 of the hollow honeycomb structure and the inner electrode portion 120b. and/or is disposed so as to cover the outer peripheral sidewall 112 of the hollow honeycomb structure at a position sandwiched between the outer peripheral sidewall 112 of the hollow honeycomb structure and the outer electrode portion 120a. , a PTC thermistor 122 .

(1.2.1 Columnar honeycomb structure part)
The overall shape of the hollow honeycomb structure and the shape of the cells are the same as those of the columnar honeycomb structure described in the first embodiment, except for the fact that they are hollow, so detailed description is omitted. do. However, in the second embodiment, since the electrode portions are arranged on both the outer peripheral side and the inner peripheral side of the hollow honeycomb structure portion, by arranging the cells radially, electricity can easily flow in the radial direction. . Therefore, arranging the cells radially increases the uniform heating performance particularly when the electrode portions are arranged on both the outer peripheral side and the inner peripheral side of the hollow honeycomb structure portion as in the present embodiment. Advantageous.

The size and height of each bottom area of the hollow honeycomb structure, the average thickness of the partition walls, the cell density, the open area ratio, and the material are the same as those described for the columnar honeycomb structure described in the first embodiment, so the details are as follows. detailed description is omitted.

From the viewpoint of securing the area where the PTC material contacts the honeycomb, the ratio of the area occupied by the hollow parts to the cross-sectional area of the entire hollow honeycomb structure including the hollow parts and the cell openings in the cross section perpendicular to the flow path of the cells is , preferably 5% or more, more preferably 10% or more. In addition, from the viewpoint of sufficiently securing the honeycomb portion and suppressing gas flow resistance, the hollow portion occupies the cross-sectional area of the entire hollow honeycomb structure portion including the hollow portion and the cell opening in the cross section perpendicular to the flow path of the cells. The area ratio is preferably 80% or less, more preferably 60% or less, and even more preferably 50% or less. Note that the electrodes and the PTC thermistor are not considered in calculating the area occupied by the hollow portion.

(1.2.2 Electrodes)
The heater element 200 has an outer electrode portion 120a formed on the outer peripheral side of the outer peripheral side wall 112 of the hollow honeycomb structure portion, and an inner electrode portion 120b formed on the inner peripheral side of the inner peripheral side wall 117 of the hollow honeycomb structure portion. Prepare. When a voltage is applied between the pair of electrode portions, the hollow honeycomb structure portion is energized and can generate heat by Joule heat. In a preferred embodiment, from the viewpoint of uniform heat generation, the outer electrode portion 120a is formed so as to cover the entire outer peripheral side of the outer peripheral side wall of the hollow honeycomb structure portion. In a preferred embodiment, from the viewpoint of uniform heat generation, the inner electrode portion 120b is formed so as to cover the entire inner peripheral side of the inner peripheral side wall 117 of the hollow honeycomb structure portion. As a result, the honeycomb structure can suppress unevenness in the current flowing through the honeycomb structure when a voltage is applied between the pair of electrode portions 120a and 120b, thereby suppressing unevenness in the temperature distribution in the honeycomb structure. can be done. As shown in FIG. 2-2(a), the inner electrode portion 120b can be provided so as to completely block the hollow portion of the honeycomb structure portion, thereby increasing the structural strength of the heater element. can be done. An electric wire can be connected to each of the electrode portions 120a and 120b by diffusion bonding, a mechanical pressing mechanism, welding, or the like, and power can be supplied from a battery through the electric wire, for example.

The material of each of the electrode portions 120a and 120b is the same as the electrode portion described in the first embodiment, so detailed description thereof will be omitted.

(1.2.3 PTC thermistor)
The heater element 200 is arranged so as to cover the inner peripheral sidewall 117 of the hollow honeycomb structure at a position sandwiched between the inner peripheral sidewall 117 of the hollow honeycomb structure and the inner electrode portion 120b. A PTC thermistor 122 may be provided. Alternatively or additionally, the heater element 200 covers the outer peripheral sidewall 112 of the hollow honeycomb structure at a position sandwiched between the outer peripheral sidewall 112 of the hollow honeycomb structure and the outer electrode portion 120a. A PTC thermistor 122 is provided.

With such a PTC thermistor sandwich structure, the heat from the columnar honeycomb structure is quickly transferred to the PTC thermistor 122, so that when the columnar honeycomb structure overheats, the PTC thermistor 122 quickly operates. , it becomes possible to suppress the electric current passing through the columnar honeycomb structure portion via the electrode portion 120 . From the viewpoint of enhancing the overheating prevention performance, it is preferable that at least the PTC thermistor is arranged on the outer peripheral electrode side where the covering area can be increased.

From the viewpoint of enhancing the overheating prevention performance, the ratio of the total area S of the portion where the inner peripheral sidewall and/or the outer peripheral sidewall 112 of the hollow honeycomb structure is covered with the PTC thermistor 122 to the volume V of the columnar honeycomb structure (S /V) is preferably 0.1 cm ² /cm ³ or more, more preferably 0.2 cm ² /cm ³ or more, and even more preferably 0.4 cm ² /cm ³ or more. preferable. From the viewpoint of maintaining a simple shape, the upper limit of S/V is preferably 0.8 cm ² /cm ³ or less, more preferably 0.7 cm ² /cm ³ or less, and more preferably 0.6 cm ^{2 .} /cm ³ or less is even more preferable. Here, the volume V of the honeycomb refers to a volume value measured based on the external dimensions of the columnar honeycomb structure (hollow portions are not included in the volume V). Further, the total area S refers to the total area of the portion where the inner peripheral sidewall and/or the outer peripheral sidewall of the columnar honeycomb structure is covered by the plurality of PTC thermistors when a plurality of PTC thermistors are installed.

When the PTC thermistor 122 is arranged to cover the inner peripheral sidewall 117 of the hollow honeycomb structure, the inner electrode portion 120b of the PTC thermistor 122 is in direct contact with the inner peripheral sidewall 117 of the hollow honeycomb structure. It is preferably arranged so that there are no parts. Similarly, when the PTC thermistor 122 is arranged to cover the outer peripheral wall 112 of the hollow honeycomb structure, the PTC thermistor 122 has the outer electrode portion 120a in direct contact with the outer peripheral wall 112 of the hollow honeycomb structure. It is preferable that it is arranged so that there is no part to be bent. According to this configuration, when the PTC thermistor is activated, it is possible to completely cut off the current path.

The material, Curie point, and average thickness of the PTC thermistor 122 in the second embodiment are the same as those of the PTC thermistor described in the first embodiment, so detailed description thereof will be omitted.

(2. How to use the heater element)
The heater element according to the present invention can generate heat by, for example, applying a voltage between a pair of electrodes. From the viewpoint of rapid heating, the applied voltage is preferably 200 V or higher, more preferably 250 V or higher. As described above, the heater element according to the present invention is highly safe because the initial current can be suppressed even when a high voltage is applied. In addition, since the safety specifications do not become heavy, the equipment around the heater can be manufactured at low cost.

The gas can be heated by flowing the gas through the cell while the heater element is generating heat due to the application of voltage. The temperature of the gas flowing into the cell can be, for example, -60°C to 20°C, typically -10°C to 20°C.

(3. Manufacturing method of heater element)
Next, a method for manufacturing a heater element according to the present invention will be exemplified.

(3.1 Fabrication of honeycomb structure)
A columnar honeycomb structure (including a hollow honeycomb structure) can be produced according to a known method for producing a honeycomb structure. For example, first, metal silicon powder (metal silicon), a binder, a surfactant, a pore-forming material, water, etc. are added to silicon carbide powder (silicon carbide) to prepare a forming raw material. It is preferable that the mass of the metallic silicon is 10 to 40% by mass with respect to the sum of the mass of the silicon carbide powder and the mass of the metallic silicon. This is the composition of the forming raw material when the material of the honeycomb structure is Si-bonded SiC, and when the material of the honeycomb structure is SiC, metallic silicon is not added.

Binders include methylcellulose, hydroxypropylmethylcellulose, hydroxypropoxylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol and the like. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose together. The content of the binder is preferably 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

The content of water is preferably 20 to 60 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

Ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used as surfactants. These may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include graphite, starch, foamed resin, water-absorbent resin, and silica gel. The content of the pore-forming material is preferably 0.5 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

Next, after kneading the obtained forming raw material to form a clay, the clay is extruded to produce a formed honeycomb body. For extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

Next, the obtained honeycomb molded body is dried. In the drying step, 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 them, a drying method combining hot-air drying and microwave drying or dielectric drying is preferable in that the entire molded body can be dried quickly and uniformly.

Next, by firing the dried honeycomb formed body, a columnar honeycomb structure can be produced. A degreasing step for removing the binder can also be performed before firing. Firing conditions can be appropriately determined depending on the material of the formed honeycomb body. For example, when the material of the columnar honeycomb structure is mainly Si-bonded SiC, the columnar honeycomb structure is fired in an atmosphere of an inert gas such as Ar under conditions in which Si metal bonds between SiC particles to obtain a columnar honeycomb structure. Structures can be made.

The firing furnace is not particularly limited, but an electric furnace, a gas furnace, or the like can be used.

(3.2 Production of PTC thermistor)
A PTC thermistor can be produced, for example, by the following procedure. A raw material composition containing a dispersion medium and a binder is mixed with a ceramic raw material and kneaded to prepare a paste or slurry. Additives such as a dispersant, a semiconducting agent, a shifter, a metal oxide, a property improving agent, and a conductor powder can be blended into the raw material composition as needed.

The ceramic raw material is the raw material of the portion that remains after firing and constitutes the skeleton of the PTC thermistor as ceramic. The ceramic raw material can be provided, for example, in the form of powder. As the ceramic raw material, oxides such as TiO ₂ and BaCO ₃ which are the main components of barium titanate, and carbonate raw materials can be used. In addition, semiconducting agents such as Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, low temperature side shifters such as Sr, Sn and Zr , (Bi--Na), (Bi--K) and other high-temperature side shifters, characteristic improvers such as Mn, oxides, carbonates, or oxalates that become oxides after firing. good. Conductive powders such as carbon black and nickel may be added to control conductivity.

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. In addition, from the viewpoint of maintaining the strength of the molded body, the content of the binder is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, more preferably 6 parts by mass with respect to 100 parts by mass of the ceramic raw material. The above is even more preferable. The content of the binder is preferably 9 parts by mass or less, more preferably 8 parts by mass or less with respect to 100 parts by mass of the ceramic raw material, from the viewpoint of suppressing cracking of the molded body during heating for removing the binder. It is even more preferable that it is not more than parts by mass. One type of binder may be used alone, or two or more types may be used in combination.

Surfactants such as ethylene glycol, dextrin, fatty acid soap, and polyalcohol can be used as dispersants. Dispersants may be used singly or in combination of two or more. The content of the dispersant is preferably 0 to 2 parts by mass with respect to 100 parts by mass of the ceramic raw material.

Next, the obtained paste or slurry is applied to desired locations on the outer peripheral side wall and/or the inner peripheral side wall of the honeycomb structure, and then the paste or slurry is fired. Temporary firing may be performed to remove the binder and the like before firing. As the firing conditions, it is preferable to heat at 950 to 1,300° C. for 10 to 120 minutes in an inert atmosphere such as nitrogen, argon, or vacuum.

Alternatively, the PTC thermistor may be produced by kneading the raw material composition described above to obtain a clay, molding it into the desired PTC thermistor shape, and then drying, degreasing and firing it. The firing conditions can be appropriately determined according to the material of the PTC thermistor. For example, when the PTC thermistor is mainly made of barium titanate, the firing temperature is preferably 1100 to 1400.degree. C., more preferably 1200 to 1300.degree. Also, the firing time is preferably about 1 to 4 hours. The manufactured PTC thermistor can be bonded to a desired location on the outer peripheral side wall and/or the inner peripheral side wall of the honeycomb structure by a method such as metallization bonding (brazing), diffusion bonding, inorganic adhesive, or the like.

(3.3 Formation of electrode portion)
An electrode part can be joined to the honeycomb structure part with a PTC thermistor thus obtained. Electrodes can be formed on the surface of the PTC thermistor by metal deposition methods such as sputtering, vapor deposition, electrolytic deposition, and chemical deposition. The electrode portion can also be formed by applying an electrode paste on the surface of the PTC thermistor and then baking it. Furthermore, it can also be formed by thermal spraying. Either method can form the coated electrode part on the surface of the PTC thermistor. The electrode portion may be composed of a single layer, but may also be composed of a plurality of electrode layers having different compositions. For example, the thickness of the electrode part is about 5 to 30 μm for paste baking, 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. The inner electrode portion can also be provided so as to completely block the hollow portion of the honeycomb structure portion, thereby increasing the structural strength of the heater element.

(4. Heater for cabin heating)
FIG. 3 schematically shows the configuration of a vehicle interior heating heater 300 according to one embodiment of the present invention. The heater according to the present embodiment includes the heater element 100 (or 200) according to the present invention, and the inflow pipes 132 (132a, 132b) that communicate the outside air or the air in the passenger compartment 130 with one bottom surface 114 of the heater element 100 (or 200). ), a battery 134 for applying voltage to the heater element 100 (or 200), and an outflow pipe 136 that communicates the other bottom surface 116 of the heater element 100 (or 200) with the air in the passenger compartment 130.

The heater element 100 (or 200) can be configured, for example, to be connected to the battery 134 by an electric wire 119 and turn on a power switch on the way to energize the heater element 100 (or 200) to generate heat. be.

A blower 138 can be installed upstream or downstream of the heater element 100 (or 200). It is preferable to install the blower downstream of the heater element 100 (or 200) from the viewpoint of ensuring safety by arranging high-voltage components as far away from the vehicle compartment as possible. When the blower 138 is driven, air flows into the heater element 100 (or 200) through the inflow pipes 132 (132a, 132b) from inside or outside the vehicle. The air is heated while passing through the heat generating heater element 100 (or 200). Heated air exits heater element 100 (or 200) and is channeled into the passenger compartment through outflow line 136. FIG. The outflow pipe outlet may be arranged near the feet of the occupants so that the heating effect is particularly high even in the passenger compartment, or the pipe outlet may be arranged in the seat to warm the seat from the inside, or the window may be arranged. It may be arranged in the vicinity to have the effect of suppressing fogging of the window.

The vehicle interior heating heater 300 according to the embodiment of FIG. 3 includes an inflow pipe 132a that communicates outside air with one bottom surface 114 of the heater element 100 (or 200). Furthermore, the heater for heating the vehicle compartment according to the embodiment of FIG. 3 includes an inflow pipe 132b that communicates the air in the vehicle compartment 130 with one bottom surface 114 of the heater element 100 (or 200). The inflow pipe 132a and the inflow pipe 132b join in the middle. Valves 139 (139a, 139b) can be installed in the inflow pipe 132a and the inflow pipe 132b on the upstream side of the junction. By controlling the opening and closing of the valves 139 (139a, 139b), there is a mode in which outside air is introduced into the heater element 100 (or 200) and a mode in which the air inside the passenger compartment 130 is introduced into the heater element 100 (or 200). You can switch. For example, when valve 139a is opened and valve 139b is closed, a mode is entered in which ambient air is introduced into heater element 100 (or 200). It is also possible to open both the valve 139a and the valve 139b to introduce the outside air and the air inside the passenger compartment 130 into the heater element 100 (or 200) at the same time.

The heater of the present invention can be used as an auxiliary heater in a vehicle that employs a vapor compression heat pump as a main heating device, and in that case, it is assumed that the air is not sent directly to the passenger compartment as described above. In that case, the "vehicle compartment" described above may be replaced with "a part of the main heating system blower pipe". In addition, the return pipe from the cabin may be further branched to provide a route for exhaust to the outside of the vehicle via a valve, but the exhaust to the outside of the vehicle should be performed by the main heating system using a vapor compression heat pump. It can be done in conjunction with another exhaust system.

The following examples are provided for a better understanding of the invention and its advantages, but are not intended to limit the scope of the invention.

<Examples 1 to 6>
(1. Fabrication of honeycomb structure)
A rectangular parallelepiped Si-bonded SiC honeycomb structure having dimensions shown in Table 1 was produced by molding and firing by a known method. The material composition of the honeycomb structure is the same in any of the examples. The honeycomb structure part had an average partition wall thickness of 0.13 mm, a cell density of 60 cells/cm ² , a square cell shape in a cross section orthogonal to the cell flow path, and an aperture ratio of 0.806. In Table 1, a and b indicate the length of each base of the honeycomb structure, and c indicates the height of the honeycomb structure (the length of the channel of the cells). In Table 1, V is the volume of the honeycomb structure, and TS is the total area of the outer peripheral side wall.

(2. Formation of PTC thermistor)
A paste is prepared by mixing TiO ₂ and BaCO ₃ , which are raw materials of barium titanate, with a dispersion medium, a binder, a sifter, etc., and after applying it to a predetermined position on the outer peripheral side wall of the honeycomb structure, the paste is fired. Then, a pair of PTC thermistors having various specifications shown in Table 1 were formed so as to face the outer peripheral wall of the honeycomb structure according to the number of the example. In Examples 5 and 6, the PTC thermistors were formed after an electrical insulating layer (silicon oxide film) was formed by the CVD method on part of the outer peripheral sidewall of the honeycomb structure to be covered with the PTC thermistors.

In Table 1, the covered area S indicates the total area covered by the PTC thermistor on the peripheral side wall. In Table 1, the Curie point indicates the Curie point measured by the method described above for a sample having the same specifications as the PTC thermistor used in the example. In Table 1, S/V indicates the ratio of the total area S of the portion where the outer peripheral side wall of the honeycomb structure is covered with the PTC thermistor to the volume V of the honeycomb structure. In Table 1, the electrical conduction area is the area Se obtained by subtracting the area of the portion where the outer peripheral side wall of the honeycomb structure part is in contact with the electrical insulating layer from the total area S of the portion where the outer peripheral side wall of the honeycomb structure part is covered with the PTC thermistor. show. Except for Examples 5 and 6, the electrical conduction area is equal to the covered area S. In Table 1, the covering position indicates the covering position of the peripheral side wall with the PTC thermistor and the electrical insulating layer when the honeycomb structure is observed from the bottom side. In any example, the PTC thermistor was extended over the entire height direction of the honeycomb structure.

(3. Formation of electrode portion)
On the PTC thermistor surface of the honeycomb structure with the PTC thermistor prepared as described above, an electrode portion (thickness 1 mm) made of tungsten was formed by a method of baking a glass frit mixed paste, and a heater element was manufactured. . In any of the examples, the electrode portion was formed so as to cover the entire surface of the PTC thermistor just enough. In Table 1, the position of the electrode portion in Examples 1 to 6 is "outside", which means that the electrode portion is located on the outer peripheral side of the PTC thermistor.

(4. Test of Excess Temperature Rise Prevention Effect)
A voltage of 200 V was applied at room temperature to the pair of opposing electrode portions of the heater element according to each example obtained by the above procedure to generate heat. The maximum temperature reached near the center axis of the honeycomb at the center position in the direction of (c) was investigated. Then, the effect of preventing excessive temperature rise was evaluated according to the following criteria. Table 1 shows the results.
D: Curie temperature of PTC material +100°C or higher.
C: Curie point temperature of PTC material +80°C or more and less than +100°C.
B: Curie point temperature of PTC material +60°C or more and less than +80°C.
A: Less than the Curie point temperature of the PTC material +60°C.

(5. Honeycomb temperature uniformity investigation)
A voltage of 200 V was applied at room temperature to the pair of opposing electrode portions of the heater element according to each example obtained by the above procedure to heat each position of the honeycomb: height of the honeycomb (cell 5 points on one diagonal line (2 points on the outermost cell, the center cell, and 2 points on the middle) and on the line connecting the center of one side The temperature distribution at a total of 9 points of 5 points (2 outermost cells, 1 central cell, and 2 intermediate cells (the central cell is common)) was investigated by the method of temperature measurement using a thermocouple. Then, the honeycomb temperature uniformity was evaluated according to the following criteria. Table 1 shows the results.
D: Maximum temperature difference in honeycomb 100°C or more C: Maximum temperature difference in honeycomb 60°C or more to less than 100°C B: Maximum temperature difference in honeycomb 30°C or more to less than 60°C A: Maximum temperature difference in honeycomb less than 30°C

(6. Consideration)
As can be seen from the results in Table 1, as the S/V increases, the effect of preventing excessive temperature rise improves. It is also found that the honeycomb temperature uniformity is improved by electrically insulating and covering the area in the honeycomb where the length of the electrical conduction path becomes relatively short.

<Comparative Example 1>
A honeycomb structure similar to that of Example 1 was prepared. In Comparative Example 1, a heater element was produced in the same manner as in Example 1, except that the PTC thermistor was formed after the electrode portion was formed on the outer peripheral wall of the honeycomb structure portion. In Table 1, the position of the electrode portion in Comparative Example 1 being "inner" means that the electrode portion is located on the inner peripheral side of the PTC thermistor. The obtained heater element was subjected to an excessive temperature rise prevention effect test and a honeycomb temperature uniformity test in the same manner as in the example. Table 1 shows the results.

In Comparative Example 1, heat from the honeycomb structure portion was transferred to the PTC thermistor through the electrode portion, resulting in a slow response speed. As a result, the effect of preventing excessive temperature rise was lower than that of the first embodiment.

100, 200 heater element 112 outer peripheral sidewall 113 partition wall 114 one bottom surface 115 cell 116 other bottom surface 117 inner peripheral sidewall 118 electrical insulating layer 119 electric wire 120 electrode portion 120a outer electrode portion 120b inner electrode portion 122 PTC thermistor 130 compartment 139 (139a , 139b) Valve 132 (132a, 132b) Inflow pipe 134 Battery 136 Outflow pipe 138 Air blower 300 Heater for cabin heating

Claims (20)

A columnar honeycomb structure capable of generating heat by electricity, having an outer peripheral wall and partition walls disposed on the inner peripheral side of the outer peripheral wall and partitioning and forming a plurality of cells forming fluid flow paths from one bottom surface to the other bottom surface;
a pair of electrode portions formed so as to face the outer peripheral side of the outer peripheral side wall of the columnar honeycomb structure portion;
a PTC thermistor disposed so as to cover the outer peripheral sidewall of the columnar honeycomb structure at a position sandwiched between the outer peripheral sidewall of the columnar honeycomb structure and at least one of the pair of electrode units;
with
The size of each bottom area of the columnar honeycomb structure is 300 cm ² or less.
heater element. A ratio (S/V) of the total area S of the portion where the outer peripheral side wall of the columnar honeycomb structure is covered with the PTC thermistor to the volume V of the columnar honeycomb structure (S/V) is 0.1 cm ² /cm ³ or more. A heater element according to claim 1. 3. The heater element according to claim 2, wherein said S/V is 0.2 cm ^<2> /cm ^<3> or more. The heater element according to any one of claims 1 to 3, wherein the plurality of cells are arranged radially in a cross section in a direction orthogonal to the fluid flow path of the plurality of cells. The heater element according to any one of claims 1 to 4, wherein the PTC thermistor is made of a PTC material having a Curie point of 100°C or higher and 250°C or lower. The heater element according to any one of claims 1 to 5, wherein the columnar honeycomb structure contains Si-bonded SiC. The heater element according to any one of claims 1 to 6, wherein the PTC thermistor is arranged such that the at least one electrode portion does not directly contact the outer peripheral side wall of the columnar honeycomb structure portion. PTC thermistors are disposed at positions sandwiched between the outer peripheral sidewall of the columnar honeycomb structure portion and the electrode portions of the pair of electrode portions,
An electrical insulating layer located between a part of at least one PTC thermistor and the outer peripheral wall of the columnar honeycomb structure, wherein the current distribution in the honeycomb structure when a voltage is applied to the pair of electrodes. 8. A heater element according to any one of claims 1 to 7, further comprising an electrical insulating layer extending at a position capable of enhancing uniformity. The total area S of the portion where the outer peripheral side wall is covered with the PTC thermistor and the area Se obtained by subtracting the area of the portion where the outer peripheral side wall is in contact with the electrical insulating layer from the total area S are 0.3≤Se/S< 9. A heater element according to claim 8, wherein: The heater element according to any one of claims 1 to 9 , wherein each cell of the columnar honeycomb structure has a channel length of 40 mm or less. An electric current supply having an outer peripheral side wall, an inner peripheral side wall, and a partition wall disposed between the outer peripheral side wall and the inner peripheral side wall and partitioning and forming a plurality of cells forming a fluid flow path from one bottom surface to the other bottom surface. a heat-generating hollow honeycomb structure,
an outer electrode portion formed on the outer peripheral side of the outer peripheral side wall of the hollow honeycomb structure portion;
an inner electrode portion formed on the inner peripheral side of the inner peripheral side wall of the hollow honeycomb structure;
as well as,
disposed so as to cover the inner peripheral sidewall of the hollow honeycomb structure at a position sandwiched between the inner peripheral sidewall of the hollow honeycomb structure and the inner electrode portion; and/or a PTC thermistor disposed so as to cover the outer peripheral side wall of the hollow honeycomb structure at a position sandwiched between the outer peripheral side wall of the hollow honeycomb structure and the outer electrode section;
with
The size of each bottom area of the hollow honeycomb structure is 300 cm ² or less.
heater element. The ratio (S/V) of the total area S of the portion where the inner peripheral sidewall and/or the outer peripheral sidewall of the hollow honeycomb structure is covered with the PTC thermistor to the volume V of the hollow honeycomb structure (S/V) is 0. 12. The heater element of claim 11, having a surface area of 1 cm ^<2> /cm ^<3> or more. 13. The heater element according to claim 12, wherein said S/V is 0.2 ^cm2 / ^cm3 or more. 14. The heater element according to any one of claims 11 to 13, wherein the plurality of cells are arranged radially in a cross-section in a direction perpendicular to the fluid flow path of the plurality of cells. The heater element according to any one of claims 11 to 14, wherein the PTC thermistor is made of a PTC material having a Curie point of 100°C or higher and 250°C or lower. 16. The heater element according to any one of claims 11 to 15, wherein said hollow honeycomb structure contains Si-bonded SiC. When the PTC thermistor is arranged so as to cover the inner peripheral sidewall of the hollow honeycomb structure, the PTC thermistor has a portion where the inner electrode directly contacts the inner peripheral sidewall of the hollow honeycomb structure. When the PTC thermistor is arranged so as to cover the outer peripheral wall of the hollow honeycomb structure, the outer electrode portion of the PTC thermistor covers the outer peripheral wall of the hollow honeycomb structure. A heater element according to any one of claims 11 to 16, arranged so that there are no parts in direct contact. The heater element according to any one of claims 11 to 17, wherein each cell of the hollow honeycomb structure has a channel length of 40 mm or less. A method of using the heater element according to any one of claims 1 to 18, wherein a voltage of 200 V or higher is applied between the two electrodes. 20. A method of using a heater element according to claim 19, comprising passing a gas from -60°C to 20°C through the cell.