JP7096587B2 - Seeds heater - Google Patents

Description

The present invention relates to a sheathed heater configured by accommodating a conductive member that generates heat when energized inside a cylindrical sheath, and particularly to a so-called single-terminal type in which a pair of terminals is provided at one end of the sheath.

The sheathed heater is an electric heater in which a heating wire (heating wire) made of a nickel-chromium alloy or the like is housed inside a metal heater pipe (sheath) and is filled with powder of an inorganic insulator.
The sheathed heater is excellent in safety, reliability, economy and the like, and is widely used as a heater for industrial use, for example.

As a conventional technique relating to a sheathed heater, for example, in Patent Document 1, a pair of terminals to which a power supply is connected is provided at one end of a heater pipe, and both ends are connected to the pair of terminals, respectively, and the other end of the heater pipe is provided. A cartridge heater with a heating wire that folds back at the end is described.

Japanese Unexamined Patent Publication No. 5-152061

A sheathed heater (cartridge) in which a pair of terminals are provided at one end of a tubular sheath (heater pipe), and a conductor including a heating element such as a nichrome wire coil is arranged so as to be folded inside the sheath. In the heater), it is required to reduce the resistance value of the heating element in order to increase the output of the heater.
When trying to reduce the resistance value of a heating element, there are methods such as changing the material to one with a smaller resistance value or reducing the winding diameter of the coil. There was a limit.
On the other hand, when the half of the folded conductor is a low resistance member (low heating element) such as a nickel rod having a lower resistance value than the heating element, the resistance value of the entire conductor (entire circuit) is used. It is possible to increase the output of the heater by reducing the voltage and increasing the current with respect to the supply voltage.
However, in this case, there is a problem that the sheath is bent at the time of heating due to the thermal stress caused by the difference in thermal elongation between the low resistance member such as a bar and other members, and deformation such as twisting occurs.
In view of the above-mentioned problems, an object of the present invention is to provide a sheathed heater that reduces electrical resistance and suppresses deformation due to thermal stress.

The present invention solves the above-mentioned problems by the following solution means.
The invention according to claim 1 comprises a sheath formed in a cylindrical shape and accommodating an insulator on the inner diameter side, a first terminal and a second terminal provided at one end of the sheath, and the sheath. On the inner diameter side, a first conductive member having a heat generating portion that is arranged along the longitudinal direction of the sheath and has one end connected to the first terminal and generates heat when energized, and on the inner diameter side of the sheath. The first conductive member is arranged in parallel with the first conductive member, one end thereof is connected to the second terminal, and the first end of the first conductive member is opposite to the second terminal side. The second conductive member is provided with a second conductive member conductively connected to the end portion on the opposite side to the terminal side of the above, and the second conductive member has a low electrical resistance with respect to the first conductive member and at least a part thereof. It is a sheathed heater characterized by having a stretchable allowance portion that can be expanded and contracted along the longitudinal direction of the sheath by elastic deformation.
According to this, in a single-terminal type sheathed heater in which a pair of terminals are provided at one end of the sheath, one of the conductive members (second conductive member) arranged in parallel in the sheath is mainly used. By lowering the electrical resistance with respect to the other conductive member (first conductive member) that contributes to heat generation, the length of the heat generating part that mainly contributes to heat generation is reduced to about half, and the resistance value of the sheathed heater as a whole is reduced. The output of the sheathed heater can be increased by lowering the voltage and increasing the current per unit voltage supplied.
Further, the expansion / contraction allowable portion of the second conductive member is elastically deformed according to the thermal expansion of the sheath due to the temperature change when each conductive member is energized to generate heat, and the sheath expands and contracts in the longitudinal direction to generate heat. Deformation of the sheath due to stress can be suppressed.
In the present specification and claims, "arranged in parallel" is not limited to the state in which the first and second conductive members are arranged completely in parallel, but is arranged side by side with twisting, bending, and the like. It shall include the state of being placed.

The invention according to claim 2 is the sheathed heater according to claim 1, wherein the expansion / contraction allowable portion is provided in parallel over the entire length of the heat generating portion of the first conductive member.
According to this, the second conductive member can be expanded and contracted by the expansion / contraction allowable portion over the entire range in which the sheath is heated, and the deformation of the sheath due to the thermal expansion difference between the sheath and the second conductive member is ensured. Can be prevented.
According to the third aspect of the present invention, the first conductive member has a coil portion made of a wire rod of at least a nickel-chromium alloy or an iron-chromium alloy, and the expansion and contraction of the second conductive member. The sheathed heater according to claim 1 or 2, wherein the permissible portion has a coil portion made of a metal wire having a lower electric resistance than the material of the coil portion of the first conductive member. ..
According to this, the above-mentioned effect can be obtained by a configuration in which an existing sheathed heater manufacturing facility or the like can be used.

As described above, according to the present invention, it is possible to provide a sheathed heater that reduces electrical resistance and suppresses deformation due to thermal stress.

It is sectional drawing of embodiment of the sheathed heater to which this invention was applied. It is sectional drawing of the sheathed heater which is a comparative example of this invention. It is a photograph which shows the deformation at the time of use in the sheathed heater of the comparative example.

Hereinafter, embodiments of a sheathed heater to which the present invention is applied will be described.
The sheathed heater of the embodiment is applied to a heater unit in which a sheath (heater pipe) having a length of about several meters is bent and embedded in a predetermined pattern along a groove formed in a plate-shaped base material, for example. It is a long and relatively small diameter cartridge heater that can be used.

FIG. 1 is a cross-sectional view of the sheathed heater of the embodiment.
FIG. 1A shows a cross section cut along a plane including the sheath and the central axis of each terminal, and FIG. 1B is a cross-sectional view taken along the line bb of FIG. 1B. (Same as in FIG. 2 described later)
The sheathed heater 1 has a sheath 10, terminals 20, 30, a high heating element 40, a low heating element 50, a connecting member 60, and the like.

The sheath 10 is a heater pipe that functions as a housing for the main body of the sheathed heater 1.
The sheath 10 is formed in a cylindrical shape, for example, from an aluminum-based alloy.
As an example, the sheath 10 can have an outer diameter of about 5 mm and a length of about 2 m, but these dimensions can be appropriately changed.
The sheath 10 can be used by being plastically deformed, for example, by being curved or bent according to the shape of the base material of the heater unit or the like.

The terminals 20 and 30 are members to which a power source for supplying electric power is connected to a circuit including a high heating element 40, a low heating element 50, and a connecting member 60.
The terminals 20 and 30 are formed of, for example, a nickel round bar.
The terminals 20 and 30 are arranged in the longitudinal direction in parallel with the central axis of the sheath 10.
A part of the terminals 20 and 30 in the longitudinal direction is inserted on the inner diameter side of the sheath 10.
The other portion of the terminals 20 and 30 in the longitudinal direction is arranged so as to project from one end of the sheath 10 and is connected to a power supply (not shown).
The terminals 20 and 30 are arranged apart from each other in the radial direction of the sheath 10 so as to be symmetrical with respect to the central axis of the sheath 10 when viewed from the longitudinal direction of the sheath 10.

The high heating element 40 is a first conductive member that is arranged inside the sheath 10 and serves as a heat source that generates Joule heat when energized.
The high heating element 40 has, for example, a spiral band wire (a wire rod made of a long plate-shaped member formed in a band shape) of a nickel-chromium alloy (nichrome) so as to be concentric with the central axis of the terminal 20. It is formed in the shape of a coil wound around.
The high heating element 40 extends in the sheath 10 along the longitudinal direction of the sheath 10.
In the main part except both ends 41 and 42 of the high heating element 40, the strips are wound at a predetermined pitch at which intervals are provided between the adjacent strips so that the strips do not come into close contact with each other.

One end 41 of the high heating element 40 is wound around the outer peripheral surface of the end arranged inside the sheath 10 at the terminal 20, and is fixed to the terminal 20 in a conductive state. ..
The end 42 on the side opposite to the terminal 20 side of the high heating element 40 is wound around the outer peripheral surface of the high heating element connecting portion 61 of the connecting member 60, and is in a state of being conductive with the connecting member 60. It is fixed.
At the ends 41 and 42, the band wires are tightly wound so as to be in close contact with each other.
The main body portion, which is a region other than the end portions 41 and 42 of the high heating element 40, mainly functions as a heating portion that generates Joule heat when energized.

The low heating element 50 is a second conductive member arranged inside the sheath 10 in parallel with the high heating element 40.
The electric resistance value of the low heating element 50 is reduced with respect to the high heating element 40 by setting the material, shape, dimensions, and the like.
The resistance value of the low heating element 50 is preferably 50% or less, more preferably 30% or less of the resistance value of the high heating element 40 at the operating temperature of the sheathed heater 1.
Due to the above-mentioned resistance value setting, the low heating element 50 has a smaller heating element than the high heating element 40 when energized between the terminals 20 and 30.

The low heating element 50 spirally winds a band wire made of a metal having a smaller resistance value and elasticity than the material of the high heating element 40, for example, nickel, so as to be concentric with the central axis of the terminal 30. It is formed in a coil shape.
The low heating element 50 extends in parallel with the high heating element 40 along the longitudinal direction of the sheath 10 in the sheath 10.
In the main part except both ends 51 and 52 of the low heating element 50, the strips are wound at a predetermined pitch at which intervals are provided between the adjacent strips so that the strips do not come into close contact with each other.
The main body portion of the low heating element 50 can be elastically deformed in the expansion / contraction direction along the longitudinal direction of the sheath 10 by elastic deformation, and functions as the expansion / contraction allowable portion according to the present invention.
The main body portion (region other than the ends 51 and 52) of the low heating element 50 is arranged in parallel over the entire length of the main body portion (region other than the ends 41 and 42) that functions as the heat generating portion of the high heating element 40. ing.

One end 51 of the low heating element 50 is wound around the outer peripheral surface of the end arranged inside the sheath 10 at the terminal 30, and is fixed to the terminal 30 in a conductive state. ..
The end 52 on the side opposite to the terminal 30 side of the low heating element 50 is wound around the outer peripheral surface of the low heating element connecting portion 62 of the conductive member 60, and is in a state of being conductive with the connecting member 60. It is fixed.
In FIG. 1, the high heating element 40 and the low heating element 50 are formed straight and arranged in parallel, but in reality, inside the sheath 10, for example, two regular or irregular rows. It may be twisted in a spiral shape.

The connecting member 60 is a member that connects the end portion 42 on the side opposite to the terminal 20 side in the high heating element 40 and the end portion 52 on the opposite side to the terminal 30 in the low heating element 50 in an electrically conductive state. be.
The connecting member 60 is arranged inside the sheath 10 in the vicinity of the end portion on the side opposite to the terminals 20 and 30.
The connecting member 60 has a high heating element connecting portion 61, a low heating element connecting portion 62, and a curved portion 63.
The high heating element connection portion 61, the low heating element connection portion 62, and the curved portion 63 are integrally formed, for example, by bending a single nickel rod in a region corresponding to the curved portion 63.

The high heating element connecting portion 61 is a portion to which the end portion 42 of the high heating element 40 is connected.
The end portion of the high heating element connecting portion 61 is inserted into the inner diameter side of the end portion 42 of the high heating element 40 and is fixed in a state of being electrically conductive with the end portion 42.

The low heating element connecting portion 62 is a portion to which the end portion 52 of the low heating element 50 is connected.
The end portion of the low heating element connecting portion 62 is inserted into the inner diameter side of the end portion 52 of the low heating element 50 and is fixed in a state of being electrically conductive with the end portion 52.

The curved portion 63 is a portion connecting the ends of the high heating element connecting portion 61 and the low heating element connecting portion 62 on the opposite sides to the terminals 20 and 30.
The curved portion 63 is formed by bending a bar member along, for example, a semicircular arc whose diameter is the distance between the axes of the high heating element connecting portion 61 and the low heating element connecting portion 62.

Inside the sheath 10, powder made of an insulator such as magnesia is filled except for a region occupied by terminals 20, 30, a high heating element 40, a low heating element 50, and a connecting member 60.

Hereinafter, the effects of the above-described embodiments will be described in comparison with the comparative examples of the present invention described below.
In the description of the comparative example, the same parts as those in the above-described embodiment are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.
FIG. 2 is a cross-sectional view of a sheathed heater of a comparative example.
In the sheathed heater 1A of the comparative example, instead of the low heating element 50 of the sheathed heater 1 of the embodiment, the terminal 30 and the low heating element connecting portion 62 of the connecting member 60 are connected by, for example, a nickel rod 70. It was done.
The bar 70 is a solid round bar extending along the longitudinal direction of the sheath 10 and having a circular cross-sectional shape.
In the comparative example, the terminal 30, the bar 70, and the connecting member 60 are integrally formed by, for example, bending one nickel bar at a portion corresponding to the curved portion 63 of the connecting member 60. ..

The sheathed heater 1A of such a comparative example has a problem of deformation as described below.
FIG. 3 is a photograph showing deformation of the sheathed heater of the comparative example during use.
FIG. 3A shows a state in which the sheathed heater 1A is at room temperature before the start of energization, and FIG. 3B shows a state in which the surface of the sheath 10 is heated to 400 ° C. by energizing. FIG. (C) shows a state in which the surface of the sheath 10 is cooled to 150 ° C. after the energization is completed.

As is clear from FIG. 3B, in the sheathed heater 1A of the comparative example, the sheath 10 exhibits torsional deformation and bending deformation during heating (during temperature rise).
Further, as is clear from FIG. 3C, the shape of the sheath 10 is restored to the state before deformation when cooled.
It is considered that such deformation is mainly caused by the thermal expansion (thermal expansion) of the bar 70 being different from the thermal expansion of other members such as the sheath 10.
On the other hand, when the same test was performed with the sheathed heater 1 of the embodiment, at least the deformation of the sheath 10 which can be visually confirmed was not confirmed.
As a result of measuring the surface temperature distribution of the sheath 10 when the sheathed heater 1 of the embodiment is energized, there is a practical problem on the side where the high heating element 40 is provided and the side where the low heating element 50 is provided. No such temperature difference was detected.

According to the sheathed heater 1 of the embodiment described above, the following effects can be obtained.
(1) The low heating element 50, which is one of the conductive members arranged in parallel in the sheath 10, has a low electrical resistance with respect to the high heating element 40, which is the other conductive member that mainly contributes to heat generation. As a result, the resistance value of the sheathed heater 1 as a whole is lowered and the current per unit voltage is increased without making the coil of the high heating element 40 excessively thick or reducing the winding diameter, so that the sheathed heater 1 is output at high output. Can be transformed into.
Further, the coil-shaped main body of the low heating element 50 elastically deforms and expands and contracts in the longitudinal direction of the sheath 10 in response to the thermal elongation of the sheath 10 due to the temperature change when the high heating element 40 is energized and heated. Thereby, the deformation of the sheath 10 due to the thermal stress can be suppressed.
(2) By arranging the main body portion of the low heating element 50 in parallel over the entire length of the main body portion of the high heating element 40, the low heating element 50 can be expanded and contracted over the entire range in which the sheath 10 is heated. , Deformation of the sheath 10 due to the difference in thermal elongation between the sheath 10 and the low heating element 50 can be reliably prevented.
(3) The high heating element 40 and the low heating element 50 are coiled by winding a nickel-chromium alloy and a nickel band, respectively, so that the existing sheathed heater manufacturing equipment and the like are used. Therefore, the above-mentioned effect can be obtained.

(Modification example)
The present invention is not limited to the embodiments described above, and various modifications and changes can be made, and these are also within the technical scope of the present invention.
(1) The shape, structure, material, manufacturing method, quantity, dimensions, arrangement, etc. of the sheathed heater and each member constituting the sheathed heater are not limited to the above-described embodiment, and can be appropriately changed.
(2) In the embodiment, the material of the sheath is, for example, an aluminum alloy, but the material is not limited to this, and other materials such as stainless steel having heat resistance can also be used.
(3) In the embodiment, the material of the high heating element (first conductive member) is, for example, a nickel-chromium alloy, but the material is not limited to this, and other materials such as an iron-chromium alloy are used. You can also do it.
Further, in the embodiment, the band wire is used as the wire rod forming the coil, but the present invention is not limited to this, and a wire rod having another cross-sectional shape such as a round wire can be used.
(4) In the embodiment, the material of the low heating element (second conductive member) is, for example, nickel, but the resistance value of the low heating element can be made lower than that of the high heating element, and the resistance value of the low heating element can be made lower than that of the high heating element. Other materials having the required heat resistance, elasticity, etc. can also be used.
Further, in the embodiment, the band wire is used as the wire rod forming the coil, but the present invention is not limited to this, and a wire rod having another cross-sectional shape such as a round wire can be used.
(5) In the embodiment, the expansion / contraction allowable portion of the low heat generating body is, for example, configured by winding a wire rod in a coil shape, but the configuration of the expansion / contraction allowable portion is not limited to this, for example, a zigzag shape or a bellows. Other configurations such as a shape may be used.
(6) In the embodiment, the high heating element and the low heating element are arranged so as to match the positions in the longitudinal direction of the sheath, but the position of at least one end is set to the high heating element and the low heating element. You may make it different with.
(7) In the embodiment, the cross-sectional shape of the sheath is circular, but the cross-sectional shape of the sheath is not limited to the circular shape. For example, it can be an ellipse, an oval, or any other shape having a major axis along the arrangement direction of the high heating element and the low heating element.

1 Seeds Heater (Embodiment) 1A Seeds Heater (Comparative Example)
10 sheath 20 terminals 30 terminals 40 high heating element 41 end 42 end 50 low heating element 51 end 52 end 60 connection member 61 high heating element connection 62 low heating element connection 63 curved part 70 bar material

Claims (3)

A sheath that is formed in a cylindrical shape and contains an insulator on the inner diameter side,
A first terminal and a second terminal provided at one end of the sheath,
A first conductive member arranged on the inner diameter side of the sheath along the longitudinal direction of the sheath and having one end connected to the first terminal and having a heat generating portion that generates heat when energized.
The first end is connected to the second terminal while being arranged in parallel with the first conductive member on the inner diameter side of the sheath, and the first end is opposite to the second terminal side. The end portion of the conductive member on the side opposite to the first terminal side and the second conductive member connected so as to be conductive are provided.
The second conductive member has a low electrical resistance with respect to the first conductive member, and at least a part thereof has a stretchable allowance portion that can expand and contract along the longitudinal direction of the sheath due to elastic deformation. Seeds heater. The sheathed heater according to claim 1, wherein the expansion / contraction allowable portion is provided in parallel over the entire length of the heat generating portion of the first conductive member. The first conductive member has a coil portion made of a wire rod of at least a nickel-chromium-based alloy or an iron-chromium-based alloy.
1 or claim 1, wherein the expansion / contraction allowable portion of the second conductive member has a coil portion made of a metal wire having a lower electric resistance than the material of the coil portion of the first conductive member. Item 2. The sheathed heater according to item 2.

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