JPH07153558A - Cartridge heater - Google Patents

Abstract

PURPOSE:To obtain a cartridge heater, which has excellent radiation efficiency and which can prevent the contact failure of an electrode with a positive characteristic thermistor element. CONSTITUTION:In a heater, wires 33a, 33b are fitted to electrodes 31a, 31b made of aluminum, and these electrodes 31a, 31b are inserted into an insulating tube (thermoplastic polyimide tube) 37 under the condition that the electrodes pinch PTC(positive characteristic thermistor elements) 35a-35d to form a heat generating part 39. After housing this heat generating part 39 in a metal tube 41 having the bottom and made of stainless steel, a clearance between the insulating tube 37 and the metal tube 41 is filled with the heat conductive powder 45, and the metal tube 41 is compressed from the periphery thereof to shrink the diameter thereof. As a result, intrusion of the heat conductive powder 45 into a contact surface between the electrodes 31a, 31b and the PTC 35a-35d is prevented so as to prevent the deterioration of the radiating efficiency due to the lowering of the contact property of the electrodes 31a, 31b and the PTC 35a-35d.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cartridge heater.

[0002]

2. Description of the Related Art Conventionally, a positive temperature coefficient thermistor element (hereinafter referred to as "PT
A cartridge heater having a temperature control function (self-protection function) of not exceeding a predetermined temperature has been developed.

Conventionally, as a cartridge heater using such a PTC, for example, as shown in the cross section of FIG. 5, the lead wires 3 are respectively attached to the aluminum-made electrodes 1 and 2 formed in a kamaboko shape. , 4 is attached, and a thin plate-shaped PTC 5 is sandwiched between the electrodes 1 and 2 to form a cylindrical heating portion 6, and the heating portion 6 is inserted into a stainless steel bottomed metal tube 7 and then a bottomed metal A method has been developed in which a gap between the tube 7 and the heat generating portion 6 is filled with an insulating powder 8 such as boron nitride powder having good thermal conductivity, and then the outer circumference of the bottomed metal tube 7 is compressed and reduced in diameter. .

In this type of cartridge heater, the outer circumference of the bottomed metal tube 7 is compressed and reduced to consolidate the insulating powder 8, whereby the electrodes 1 and 2 and the PTC 5 are formed.
And the heat generation of the PTC 5 are efficiently conducted to the surface of the bottomed metal tube 7 through the insulating powder 8.

[0005]

However, in the above-mentioned conventional cartridge heater, when the insulating powder 8 is filled or the insulating powder 8 is compacted, the insulating powder 8 and the electrodes 1, 2 and PT are used.
It enters the contact surface with C5, and the contact property of both decreases,
There is a problem that the heat generation efficiency of the PTC 5 and, in turn, the heat radiation efficiency of the heater itself deteriorates.

Further, in the above-mentioned conventional cartridge heater, there is a problem that the insulating powder 8 must be made of a material having both excellent insulating properties and thermal conductivity. The present invention has been made in view of the above problems, and an object of the present invention is to provide a cartridge heater that is excellent in heat dissipation efficiency and can prevent defective contact between an electrode and a PTC.

[0007]

[Means for Solving the Problems] That is, the present invention as set forth in claim 1 made to achieve the above object, comprises a heat generating portion having a positive temperature coefficient thermistor element and electrodes sandwiching the positive temperature coefficient thermistor element, A cartridge heater provided with a bottomed metal tube for accommodating the heat generating part, and powder having good thermal conductivity filled in a gap between the bottomed metal tube and the heat generating part,
A cartridge heater is characterized in that an insulating material is provided around an electrode surface of the heat generating portion, and then the heat generating portion is housed in the bottomed metal tube.

A second aspect of the present invention provides a cartridge heater according to the first aspect, characterized in that the insulating material is formed of a thermoplastic resin.

[0009]

In the cartridge heater according to claim 1 configured as described above, when a current is passed through the electrodes of the heat generating portion, the PTC (positive temperature coefficient thermistor element) generates heat, and the heat is It is released from the surface of the bottomed metal tube to the outside world through the electrode, the insulating material provided around the surface of the electrode, and the powder having good thermal conductivity filled in the gap between the bottomed metal tube and the heat generating portion. .

In the cartridge heater according to the first aspect, the insulating material is provided around the electrode surface of the heat generating portion, and then the heat generating portion is housed in the bottomed metal tube. Therefore, according to the cartridge heater of claim 1, when the powder is filled in the gap between the bottomed metal tube and the heat generating portion, or when the outer circumference of the bottomed metal tube is compressed and reduced to consolidate the powder, etc. In addition, since the insulating material can prevent the powder from entering the contact surface between the electrode and the PTC, it is possible to prevent the heat dissipation efficiency from being deteriorated due to the decrease in the contact property between the electrode and the PTC.

Further, in the cartridge heater according to the first aspect of the present invention, since the electrodes of the heat generating portion and the bottomed metal tube are pre-insulated by the insulating material, the heat is generated between the heat generating portion and the bottomed metal tube. The material of the powder to be filled may be one having excellent thermal conductivity. Therefore, for example, as the material of the powder, it is possible to use a metal such as copper or aluminum, and the selection range becomes extremely large.

Here, it is conceivable to use a thermosetting resin as the material of the insulating material provided around the surface of the electrode.
However, in this case, for example, by heating the insulating material before housing the heat generating part in the bottomed metal tube, the electrode and PTC can be brought into close contact with each other in advance, but the outer circumference of the bottomed metal tube is compressed. When the diameter is increased, the stress may cause cracks in the insulating material.

Therefore, in the cartridge heater according to the second aspect, the insulating material is made of a thermoplastic resin. With the cartridge heater according to the second aspect, there is no fear of cracks in the insulating material when the diameter of the bottomed metal tube is reduced by compression.
At that time, the electrode and the PTC can be firmly adhered.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and includes all embodiments that can be conceived by those skilled in the art without departing from the gist of the present invention.

First, FIG. 1 is a vertical sectional view of a cartridge heater according to an embodiment, and FIG. 2 is a horizontal sectional view taken along the line BB in FIG. As shown in FIGS. 1 and 2, the cartridge heater according to the present embodiment includes electrodes 31a and 31b made of aluminum alloy which also have a heat dissipation function, and the electrodes 31a and 31b.
lead wires 33a and 3 attached to a and 31b, respectively
3b and the P for heat generation sandwiched between the electrodes 31a and 31b
TC35a, 35b, 35c, 35d and a thermoplastic polyimide having high insulation and thermal conductivity are formed into a bottomed tube shape, and the electrodes 31a, 31b are PTC35a-.
Polyimide tube 3 inserted with 35d sandwiched
7, a bottomed metal pipe (hereinafter, simply referred to as a metal pipe) 41 as a cartridge for accommodating a columnar heat generating portion 39 including the above-mentioned members, and a bottom portion 41a of the metal pipe 41,
Recess 43a into which the bottom of the polyimide tube 37 is fitted
Ceramic plate 43 provided with a polyimide tube 37
Of the heat conductive powder 45 filled in the gap between the outer surface of the metal tube 41 and the inner peripheral surface of the metal tube 41, the silicon seal 47 for preventing the heat conductive powder 45 from leaking from the metal tube 41, and the lead wires 33a, 33b. Of the metal pipe 41 by inserting the electrode terminals 49a and 49b connected to one end of the metal pipe 41, which are taken out from the opening 41b of the metal pipe 41 and connected to the power supply line (not shown), respectively. Opening 4
It is composed of an insulative plug body 51 for closing 1b, and a mounting screw plug 53 welded to the outer periphery of the metal tube 41 near the opening 41b.

Here, the metal tube 41 is formed in a bottomed cylindrical shape, and is made of a material having excellent thermal conductivity and rollability, for example, stainless steel (SUS316L or the like). The electrodes 31a and 31b have the same shape,
Made of an aluminum alloy having a diameter of about 2/3 of the inner diameter of the metal tube 41 and about 2/3 of the length of the metal tube 41 (for example, JI
A metal column of S standard 6063-T4) is formed by being divided into two substantially in the axial direction, and its cross section has a substantially semicircular shape. Then, as shown in FIG.
Grooves 55a and 55b for inserting the lead wires 33a and 33b are formed on the outer peripheral surfaces of the curved surfaces a and 31b, respectively.
It is formed up to both ends in the direction orthogonal to the arc of the curved surface, and the outer peripheral surface of the flat surface of each of the electrodes 31a and 31b has a shallow groove 57a for positioning with the PTCs 35a to 35d sandwiched therebetween. , 57b are formed in the axial direction. Then, such electrodes 31a, 31
b is each groove 55a, 55b, 57a, 57 by casting.
It is formed as a shape having b in advance.

On the other hand, the PTCs 35a to 35d are ceramic semiconductors formed by mixing a small amount of yttrium or the like with barium titanate and sintering it, and are heating materials whose resistance suddenly increases when the temperature exceeds a predetermined temperature. That is, a general thermistor whose resistance value decreases as the temperature rises is referred to as a negative characteristic thermistor, whereas it is a positive characteristic thermistor and is a heating material having its own temperature control function. Since such a PTC is manufactured by mixing and sintering an inorganic material, it can be formed in a desired size and a desired shape.

In the cartridge heater of this embodiment,
The sizes of the PTCs 35a to 35d are the electrodes 31a and 31b.
Is a rectangular plate shape having a length shorter than the length of, and slightly narrower than the length of the diameter of the arc of the electrodes 31a and 31b, and a thickness of a little less than half the width. In addition, a metal having a high conductivity, such as silver, is coated on each surface of the PTCs 35a to 35d in contact with each of the electrodes 31a and 31b to prevent an increase in contact resistance between the electrodes and each of the electrodes 31a, 31b. 31b and PTC35a
The generation of Joule heat is prevented at the contact portion with ~ 35d. As the PTCs 35a to 35d, for example, PTC thermistor elements manufactured by Murata Manufacturing Co., Ltd. are used.

In the cartridge heater of this embodiment, boron nitride powder is used as the heat conductive powder 45, and the inner diameter of the polyimide tube 37 is such that the electrodes 31a and 31b sandwich the PTCs 35a to 35b. It is formed to have almost the same outer shape.

On the other hand, the electrode terminals 49a and 49b are respectively
The lead wire 33a is made of metal and formed into a rod shape.
The end on the side connected to 33b has a tubular shape. That is, by inserting and crimping the ends of the lead wires 33a and 33b into the cylindrical ends, the lead wires 33a and 33b are inserted.
It can be electrically connected to. The lead wires 33a and 33b are made of nickel alloy.

The silicon seal 47 is a viscous agent containing silicon as a main component and is hardened with the passage of time. Next, a procedure for manufacturing such a cartridge heater of this embodiment will be described with reference to FIG.

First, one ends of the lead wires 33a and 33b are connected to one ends of the electrode terminals 49a and 49b (not shown in FIG. 3) by crimping. Then, as shown in FIG. 3, the other ends of the lead wires 33a and 33b are inserted into the grooves 55a and 55b of the electrodes 31a and 31b, respectively, and external force is applied to the electrodes 31a and 31b to crimp the electrodes. Lead wires 33a, 33b are provided on the electrodes 31a, 31b.
Attach.

Next, the shallow groove 57 of each electrode 31a, 31b is formed.
The PTCs 35a to 35b are aligned and positioned on a and 57b, and the columnar body thus formed is inserted to the bottom of the polyimide tube 37 to form a cylindrical heating portion 39.
To form. On the other hand, the ceramic plate 43 is placed on the bottom portion 41a in the metal pipe 41 in advance, and the metal pipe 4
The screw plug 53 is attached to the outer peripheral surface near the opening 41b of No. 1 in advance. The screw plug 53 is attached by welding the edge portion of the screw plug 53 to the outer peripheral surface of the metal tube 41.

Then, after the heating portion 39 formed as described above is inserted into the metal tube 41 through the opening 41b,
As shown in FIG. 1, the metal tube 41 and the polyimide tube 37
The heat conduction powder 45 is filled up to a predetermined position in the gap between and. Then, the silicon seal 47 is injected from the opening 41b so that the filled thermal conductive powder 45 does not leak.

After that, pressure is applied from the outer periphery of the metal pipe 41 toward the axial direction on the bottom portion 41a side of the portion where the screw plug 53 is welded to the metal pipe 41 to compress and reduce the diameter of the metal pipe 41. Then, since the heat conduction powder 45 is compacted in the metal tube 41 by this diameter reduction, the electrodes 31a, 31b and the like are firmly fixed, and the PTCs 35a-35d and the electrodes 31a, 31b are brought into contact with each other due to the displacement of the PTCs 35a-35d. In addition to preventing defects, the heat generated by the PTCs 35a to 35d is efficiently conducted to the metal tube 41.

After performing such compression reduction,
The electrode terminals 49a and 49b are respectively inserted into the two holes formed in the plug body 51, and the plug body 51 is opened.
Insert from b into the metal tube 41. As a result, the opening 41b of the metal tube 41 is closed with the electrode terminals 49a and 49b protruding outward, and the cartridge heater of this embodiment is completed.

In the cartridge heater of this embodiment having such a structure, when the electrode terminals 49a and 49b are connected to the power supply line, the P sandwiched between the electrodes 31a and 31b is obtained.
An electric current flows through the TCs 35a to 35d to generate heat. And
The heat is transmitted to the metal tube 41 through the electrodes 31a and 31b, the polyimide tube 37, and the heat conductive powder 45, and is radiated from the surface of the metal tube 41 to the outside. And
Due to the characteristics of the PTCs 35a to 35d, when the temperature reaches a predetermined temperature, the resistance value suddenly increases and the amount of flowing current decreases, so that the entire cartridge heater does not overheat.

In the cartridge heater of this embodiment, the screw plug 53 is provided on the outer periphery of the opening 41b of the metal tube 41.
Since the cartridge heater is attached, the cartridge heater can be easily attached to an arbitrary place into which the screw plug 53 can be screwed. Here, in the cartridge heater of this embodiment, the electrodes 31a and 31b are used to
By inserting the columnar body formed by sandwiching TCs 35a to 35d into the thermoplastic polyimide tube 37,
9 is formed, and the heat generating portion 39 is housed in the metal tube 41.

Therefore, according to the cartridge heater of this embodiment, the heat conduction powder 45 is filled in the gap between the metal tube 41 and the heat generating portion 39 (polyimide tube 37), and the metal tube 41 is reduced in diameter and compressed. When the heat conduction powder 45 is compacted, the heat conduction powder 45 is contacted by the polyimide tube 37 between the electrodes 31a and 31b and the PTCs 35a to 35d, that is, the shallow grooves 57a formed in the electrodes 31a and 31b.
57b is prevented from entering the electrodes 31a, 31b
It is possible to prevent deterioration of heat dissipation efficiency due to a decrease in contact property between the PTCs 35a to 35d.

Further, in the cartridge heater of this embodiment, the electrodes 31a and 31b and the metal tube 41 are pre-insulated by the polyimide tube 37. Therefore, the material of the heat conductive powder 45 is a heat conductive material. Only good ones will be enough. That is, in this embodiment, as the heat conductive powder 45, boron nitride powder was used as in the conventional cartridge heater, but metal powder such as copper or aluminum can be used. Then, for example, when copper powder is used as the heat conductive powder 45, there is an advantage that the heat conductivity is better and the cost is lower than that of the boron nitride powder.

Furthermore, in the cartridge heater of this embodiment, a polyimide tube 37 made of thermoplastic polyimide is used as an insulating material that is provided around the surfaces of the electrodes 31a and 31b. Therefore, according to the cartridge heater of the present embodiment, there is no fear of cracks in the polyimide tube 37 due to stress when the metal tube 41 is reduced in diameter and compressed.

In the cartridge heater of the above embodiment, four PTCs 35 are provided between the electrodes 31a and 31b.
Although a to 35d are arranged in a column, the number can be appropriately set according to the length of the heat generating portion of the cartridge heater and the length of each PTC.

Further, in the cartridge heater of the above embodiment, the PTC is formed on the flat side surface of each electrode 31a, 31b.
Shallow grooves 57a, 57 for positioning 35a to 35d
Although b is formed, it is not always necessary to form such shallow grooves 57a and 57b in the electrodes 31a and 31b. For example, as shown in FIG.
35 may be in contact with the entire flat side surfaces of the electrodes 131a and 131b. And in this case, PTC
Since a part of 135 comes into direct contact with the polyimide tube 37, PTC135
The heat generated from the heat is directly transmitted to the heat conductive powder 45 without passing through the electrodes 131a and 131b, and the heat generation efficiency is improved.

Furthermore, in the cartridge heater of the above embodiment, one set of electrodes 31a and 31b is used to form one row of PTC 35a.
~ 35d was sandwiched between the electrode and PT
The number of Cs may be set arbitrarily, and for example, as shown in FIG. 4B, four electrodes 231a, 231b, 231
c, 231d, four PTCs 235a, 235b, 2
You may make it pinch | interpose 35c and 235d. Incidentally, FIG.
In (B), 233a, 233b, 233c, 23
3d shows the lead wires attached to the electrodes 231a to 231d, respectively, and 255a, 255b, 255c, 2
55d shows grooves for fixing the lead wires 233a to 233d, respectively.

On the other hand, in the cartridge heater of the above embodiment, the metal tube 41 has a bottomed cylindrical shape, but a fin for heat radiation may be attached to the outer periphery of the metal tube 41 after the compression and diameter reduction. The metal tube 41 is not limited to the cylindrical shape,
For example, a triangular prism shape, a quadrangular prism shape, or a cylindrical shape having an elliptical cross section may be used.

In the cartridge heater of the above embodiment, the lead wires 33a, 3 to the electrodes 31a, 31b are also used.
3b is attached to the grooves 55a and 55b by the lead wire 33.
Although it was performed by inserting and crimping a and 33b, instead of crimping, use various connecting means capable of ensuring conductivity between the electrodes 31a and 31b and the lead wires 33a and 33b. You can

Further, in the cartridge heater of the above embodiment, the bottomed tubular polyimide tube 37 was used as an insulating material for insulating the electrodes 31a and 31b from the metal tube 41. However, the insulating sheet formed of thermoplastic polyimide in a sheet shape is not limited to the electrodes 31a, 31
It may be wrapped around b. Further, the material of such an insulating material is not limited to polyimide, and any material having good insulation and thermal conductivity may be used, and more preferably thermoplastic material.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a cartridge heater of an embodiment.

FIG. 2 is a cross-sectional view showing a cartridge heater according to an embodiment.

FIG. 3 is an explanatory diagram illustrating a manufacturing procedure of the cartridge heater of the embodiment.

FIG. 4 is a cross-sectional view showing a cross section of a cartridge heater of another embodiment.

FIG. 5 is an explanatory diagram illustrating a conventional cartridge heater.

[Explanation of symbols]

31a, 31b, 131a, 131b, 231a-23
1d ... Electrodes 35a to 35d, 135, 235a to 235d ... Positive characteristic thermistor element (PTC) 37 ... Polyimide tube 39 ... Exothermic part 4
1 ... Bottomed metal tube 45 ... Thermal conductive powder

Claims (2)

[Claims] 1. A heat generating part provided with a positive temperature coefficient thermistor element and electrodes sandwiching the positive temperature coefficient thermistor element, a bottomed metal tube accommodating the heat generating part, and a gap between the bottomed metal tube and the heat generating part. In a cartridge heater comprising: a powder having good thermal conductivity to be filled, an insulating material is provided around the electrode surface of the heat generating part, and then the heat generating part is housed in the bottomed metal tube. Characteristic cartridge heater. 2. The cartridge heater according to claim 1, wherein the insulating material is formed of a thermoplastic resin.