JP2962605B2 - PTC heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive temperature coefficient (Positive
Temperature Coefficient Hereinafter referred to as PTC. ), Particularly a PT which efficiently heats an active or harmful gas or liquid.
Related to C heating element.

[0002]

2. Description of the Related Art It is necessary to maintain a certain temperature of a gas mixture or window fluid supplied to an internal combustion engine of an automobile even immediately after starting the internal combustion engine in a low temperature state. For this purpose, a heating element (PTC heating element) made of semiconductor porcelain having a positive temperature coefficient is often used.

It is desired that such a PTC heating element can also heat an active atmosphere such as oxidation and reduction or a gas or liquid containing toxic substances.
Many inventions have been filed for heating elements (for example, Japanese Patent Application Laid-Open Nos. 52-138735 and 57-2568).
8). FIGS. 7 (a) and 7 (b) show Japanese Patent Application Laid-Open No.
FIG. 35 is a perspective view of a PTC heating element disclosed in No. 35.

That is, (a) shows a case where a center of a cylindrical PTC heating element 701 is used as a fluid passage 702, and electrodes 703 and 704 are formed on the inner and outer circumferences of the cylinder. (B) is a diagram in which electrodes 705 and 706 are alternately spirally formed on the outer periphery of a cylindrical PTC heating element 701. Further, a device in which an electrode is formed in a comb shape on the outer periphery of a cylinder has been proposed.

FIG. 7C shows a PTC heating element disclosed in JP-A-57-25688, in which electrodes are provided on both end faces of a cylindrical PTC heating element. Further PTC
There has also been proposed a device in which a fluid is caused to flow through a PTC element using a heating element as a porous body.

[0006]

However, these PTC heating elements have the following problems. That is, in the PTC heating element shown in FIG. 7A, heat is transferred to the fluid through an insulating film for preventing the electrode provided on the inner wall surface from coming into direct contact with the fluid, so that the heat transfer efficiency is increased. In addition, since heat is generated almost at the center between the inner and outer electrodes, heat is not actively generated in the inner periphery, resulting in poor heat efficiency.

In the PTC heating element shown in FIG. 7 (b), current flows along the surface of the PTC heating element, which is the shortest distance between the electrodes, or only the portion where the current flows generates heat. Therefore, the heat generation is also limited to the surface and the efficiency is reduced . The PTC heating element shown in FIG. 7C generates heat almost uniformly inside, but heat radiation from the cylindrical surface cannot be ignored, and there is room for improvement in efficiency.

Further, the PTC heating element itself is made porous,
When a fluid is caused to flow through the porous PTC element, the porosity is extremely small, and the pressure loss becomes too high. When PTC is made porous, the resistance distribution of the fluid cannot be made uniform, and it becomes very difficult to uniformly heat the fluid. Furthermore, when an electrode is directly provided on the porous PTC, if the electrode is in direct contact with the fluid, the electrode is likely to be corroded and deteriorated, so that there is a problem that a treatment such as coating is required.

The present invention has been made in view of the above problems, and has as its object to provide a PTC heating element capable of efficiently heating a fluid and rapidly raising the temperature.

[0010]

Means for Solving the Problems A PT according to the first invention
C the heating element comprises a cylindrical flow path extending in the axial direction in order to distribute the heated fluid is formed, the outer surface of the PTC heating elements
To have a pair of electrodes for passing a current through the P TC heating element on a plane that is provided across the flow path to the. In the PTC heating element according to the second invention, the width of the pair of electrodes in the direction perpendicular to the axis of the PTC heating element is larger than the diameter of the flow path.

[0011] The PTC heating element according to the third invention is a PTC heating element.
At least two are provided in parallel with the axis of the C heating element.

[0012]

In the PTC heating element according to the present invention, not only the entire PTC heating element generates heat uniformly, but also heat is efficiently transmitted to the fluid to be heated flowing through the flow path provided in the PTC heating element.

[0013]

1 is a structural view of a PTC heating element according to the first invention, wherein FIG. 1A is a perspective view, FIG.
(C) shows a YY cross section. That is, the PTC heating element 100 has a substantially cylindrical shape, and the flow path 101 penetrates along the central axis.

A pair of flat surfaces 102 and 103 having a shape obtained by shaving a cylindrical outer wall symmetrically with respect to the flow path 101 are provided. It is also possible to provide the collar portions 104 at both ends of the cylindrical PTC heating element 100. On a pair of flat surfaces 102 and 103 of the PTC heating element 100, there are provided electrodes 105 and 106 composed of a nickel electrode electrolessly plated so as to have ohmic contact with the PTC heating element and a silver electrode printed and baked thereon. ing.

FIG. 2 shows a PTC heating element 1 according to the first invention.
1 is a cross-sectional view of an embodiment in which 00 is applied to a heating device for an air-fuel mixture supplied to an internal combustion engine. That is, the fuel injection device 200 includes a fuel injection valve 210 and a heating device 220,
From above the housing 221 of the heating device 220, the fuel injection valve 21
0 is inserted.

The PTC heating element 100 is installed inside the housing 221 so that a mixture of fuel injected from the fuel injection valve 210 and intake air supplied from the intake passage 222 flows through the flow path 101. Fuel injection valve 210 and PTC heating element 1
00 and an attachment 22 having an appropriate structure
3 and 224 are arranged to fix the PTC heating element 100 and to supply fuel and intake air to the flow path 101 of the PTC heating element 100.

An attachment 225 is also provided below the PTC heating element 100 to fix the PTC heating element 100.
The attachments 224 and 225 desirably have a heat insulating property in order to prevent the heat generated by the PTC heating element 100 from being conducted to the housing 221. Also PTC
The outer periphery of the heating element 100 is covered with an insulating and heat insulating tube 225 to block heat conduction to the housing 221 and ensure power supply to the electrodes 105 and 106 of the PTC heating element 100.

That is, terminals 227 and 228 made of, for example, brass are pressed against the electrodes 105 and 106, and power is supplied by cables 229 and 230 connected to the terminals 227 and 228. When power is supplied by cables 229 and 230, P
The TC heating element 100 generates heat, and the flow path 10 provided therein is provided.
The mixture passing through 1 is heated.

Accordingly, even in a cold region where the atmospheric temperature is low, fuel vaporization is promoted immediately after the start, and deterioration of the exhaust gas properties and fuel efficiency can be prevented. FIG. 3 is a graph of an experimental result showing the superiority of the PTC heating element according to the present invention. The horizontal axis represents time, and the vertical axis represents the flow path inner surface temperature. The chain line indicates the time response of the conventionally used PTC heating element, and the solid line indicates the time response of the PTC heating element according to the present invention.

From this experiment, it can be understood that the PTC heating element according to the present invention reaches a higher temperature in a short time. FIG.
FIG. 4 is an explanatory view of a structure of an electrode installed on a pair of planes of a PTC heating element. That is, the electrodes may be installed on the entire plane as shown in FIG. 1C, may be installed so as to cover a part of the plane as shown in FIG.
It is also possible to divide and install it so that it can be squeezed.

FIG. 5 shows FIGS. 1, 4 (a) and 4 (b).
It is a graph which shows the response characteristic of the PTC heating element shown in FIG.
The horizontal axis represents time, and the vertical axis represents current. From these results, in the PTC heating element having the structure shown in FIGS. 1 and 4B, it is possible to flow a large current in a short time.
It can be understood that the PTC heating element of (a) has a small saturation current and a long time until the saturation current is reached.

That is, it is advantageous to make the electrode wider than the diameter of the flow path and to cover the outside of the flow path. FIG. 6 is a sectional view of the second embodiment, in which three channels are provided in parallel with each other. By providing a plurality of channels, the inner surface area of the channels is increased, and the amount of heat conducted to the fluid can be increased.

[0023]

According to the PTC heating element of the present invention, P
Since the entire TC heating element generates heat uniformly, heat can be efficiently transferred to the fluid.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a PTC heating element according to a first invention.

FIG. 2 is a sectional view of an embodiment of the PTC heating element according to the first invention.

FIG. 3 is a graph of an experimental result showing the superiority of the PTC heating element according to the present invention.

FIG. 4 is an explanatory diagram of a structure of electrodes installed on a pair of planes of a PTC heating element.

FIG. 5 is a graph showing response characteristics of a PTC heating element.

FIG. 6 is a sectional view of a second embodiment.

FIG. 7 is a perspective view of a conventional PTC heating element.

[Explanation of symbols]

 Reference Signs List 100: PTC heating element 101: Flow path 102, 103: Flat surface 104: Color part 105, 106: Electrode

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuyoshi Sugaya 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (72) Inventor Hiroaki Takeda 1-Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation stock In-company (72) Inventor Chishiro Sugimoto 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (56) References JP-A-52-138735 (JP, A) Jpn. (58) Fields surveyed (Int. Cl. ⁶ , DB name) H05B 3/14

Claims (3)

(57) [Claims] 1. A PTC heating element in which a cylindrical flow path penetrating in an axial direction for flowing a fluid to be heated is formed, and is provided on an outer surface of the PTC heating element with the flow path interposed therebetween. Tahira
The surface has a pair of electrodes for passing current through the PTC heating element.
A PTC heating element characterized in that: 2. The PTC heating element according to claim 1, wherein the width of the pair of electrodes in a direction perpendicular to the axis of the PTC heating element is larger than the diameter of the flow path. 3. The PTC heating element according to claim 1, wherein at least two passages are provided in parallel with an axis of the PTC heating element.