JPH0574557A - Temperature adjusting sheath heater - Google Patents

Abstract

PURPOSE:To provide a temperature adjusting sheath heater invariably keeping the thermal state of a heating element and a heat-sensitive element constant. CONSTITUTION:A temperature adjusting sheath heater is constituted of a heating element 1, a heat-sensitive element 2 (thermocouple strand) provided across an insulator 8 not in contact with the heating element 1, an outer cover 5 covering the heat-sensitive element 2 and the heating element 1 across the insulator 8, and terminals 3, 4 for connecting the heating element 1 and the heat-sensitive element 2 to an external circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field in which heating is required and the temperature of an object to be heated must be precisely controlled, for example, a heating furnace of a thermal analyzer.

[0002]

2. Description of the Related Art Conventionally, when it is desired to precisely control the temperature of an object to be heated, while heating the object with a so-called sheath heater,
The temperature of the target object is measured with a so-called sheath thermocouple, and this temperature is fed back to control the power of the sheath heater so as to obtain the desired temperature. Here, the sheath heater refers to a heater (heater element wire) built in an outer cover (sheath, thin-walled tube of stainless steel, etc.) filled with an electrical insulator (eg, magnesium oxide). The sheath thermocouple refers to a thermosensitive element (thermocouple element wire) built in an outer cover filled with an electrical insulator. And these were separate entities.

[0003]

However, since the conventional sheath heater and sheath thermocouple are separate bodies, the time constant of heat transfer varies depending on the arrangement of the two and the contact state with the object. . Therefore, in the conventional temperature control system, there is a problem that a constant thermal state cannot be reproduced unless the feedback sensitivity or the like is adjusted for each individual system.

Further, since it is extremely important to keep the positional relationship between the heater and the thermocouple constant, a mechanism and efforts for that are necessary. Furthermore, since the positions of the heating element and the thermocouple are distant from each other, the heater temperature measured by the thermocouple is not a little affected by disturbance. The present invention focuses on the above problems, and an object thereof is to provide a temperature adjustment sheath heater in which the thermal states of the heating element and the heat-sensitive element are always constant.

[0005]

In order to achieve the above object, the present invention relates to a heating element and a heat-sensitive element which is provided at a position where it is thermally coupled to the heating element with an electrical insulator interposed therebetween. It is composed of an outer cover that wraps the heat-sensitive body and the heating element with an electrical insulator therebetween, and a terminal for connecting the heat-generating element and the heat-sensitive element to an external circuit.

[0006]

[Operation] When a current is applied to the heating element through the connection terminal,
This heating element generates heat. Then, this heat is transmitted to the object to be heated through the outer cover and heats the object to be heated.
On the other hand, the heat-sensitive body is provided at a position where it is thermally coupled to the heat-generating body, and is always provided in a fixed positional relationship with the heat-generating body. Therefore, in the temperature adjusting sheath heater according to the present invention, it is not necessary to adjust the relative positional relationship between the heat sensitive body and the heat generating body for each element individually.

[0007]

1 is a schematic view of a temperature adjusting sheath heater showing an embodiment of the present invention. This sheath heater is
The heating element 1, the heat-sensitive element 2, the heat-generating element terminal 3, the heat-sensitive element terminal 4, the jacket 5 enclosing them and the terminal outer tube 6. The space between the heating element terminal 3 and the heat-sensitive element terminal 4 is filled with the sealing material 7. Also, the heating element 1
An electric insulator 8 is filled between the heat sensitive body 2 and the jacket 5. In addition, 2 _-1 has shown the hot junction of the thermocouple which is a heat sensitive body.

Here, the material of each of the above-mentioned members is not particularly limited, but the following materials preferably apply. That is, the heating element 1 is a nichrome wire or a kanthal wire,
The thermosensitive element 2 corresponds to a thermocouple wire made of chromel wire and alumel wire or a thermocouple wire made of chromel wire and constantan wire. Further, magnesium oxide powder or the like corresponds to the electrically insulating filler. Further, the outer jacket 5 corresponds to a thin-walled stainless steel tube or the like, and the outer terminal tube 6 corresponds to a stainless-steel tube or the like. An epoxy resin or the like corresponds to the sealing material 7.

Although it is described in FIG. 1 that the heating element terminal 3 and the heating element terminal 4 are installed in a straight line,
This is merely done for the sake of convenience of explanation, and is actually installed as shown in FIG. That is, the jacket 5
Since the leakage current between the heat generating element 1 and the heat sensitive element 2 should be suppressed to the minimum value, the heat generating element 1 and the heat sensitive element 2 are installed in a positional relationship orthogonal to each other.

Next, an example of the structure of a temperature adjusting system using the temperature adjusting sheath heater shown in FIG. 1 will be described. Referring to FIG. 4, this temperature control system includes a sheath heater 10 according to the present invention, a heater power control circuit 11 for supplying appropriate electric power to the heating element terminal 3 of the sheath heater 10, and a heat-sensitive terminal 4. The temperature measuring circuit 12 receives the induced voltage of the thermocouple and the heated object 13.
The temperature measuring circuit 12 includes a temperature amplifying circuit and a room temperature compensating circuit.

Explaining the operation of this system, the sheath heater 10 receives electric power from the heater power adjusting circuit 11 to heat the object 13 to be heated. This heat generation of the heating element 1 is also transmitted to the thermocouple 2, so that a voltage proportional to the heating temperature is generated between the two heating element terminals 4 of the thermocouple 2. Then, the voltage of the heat-sensitive body terminal 4 is equal to the temperature measuring circuit 12
The sheath power adjusting circuit 11 controls the sheath heater 10 to heat the object 13 to be heated in a predetermined manner based on the input temperature data. Here, the circuit configurations of the heater power adjusting circuit 11 and the temperature measuring circuit 12 are not particularly limited, and for example, program control may be performed using a microprocessor.

FIG. 3 is a schematic view of a temperature adjusting sheath heater showing another embodiment of the present invention. The configuration is almost the same as in the case of FIG. 1, and the same parts are denoted by the same numbers. The difference from that of FIG. 1 is that the sheath heater for temperature adjustment of FIG. 3 is a double-end terminal type, whereas the FIG. 1 is a single-terminal type. That is, this sheath heater is characterized in that the heat generating terminal 3 and the heat sensitive terminal 4 are led out on both sides, and other operating principles are the same as in the case of FIG.

[0013]

As described above, in the temperature adjusting sheath heater according to the present invention, the positional relationship between the heating element and the heat sensitive element is always constant. In other words, it is not necessary to adjust the feedback sensitivity or the like for each individual system, except for variations in characteristics that occur during the manufacturing process of the temperature adjustment sheath heater. Further, depending on the system, there are cases in which variations between individual heaters that occur during the manufacturing process can be ignored.

Further, since the positional relationship between the heating element and the heat-sensitive element is always constant, it is not necessary to provide a mechanism for maintaining the positional relationship between the heater and the thermocouple as in the conventional case. further,
Since the heating element and the heat sensitive element are integrated by the outer cover,
The value measured as the heater temperature is exclusively due to the influence of the heating element, and therefore the influence of disturbance is relatively low, and is stable as a feedback system.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a drawing showing the structure of the sheath heater of FIG. 1 in more detail.

FIG. 3 is a schematic view showing another embodiment of the present invention.

FIG. 4 is a block diagram of a temperature control system using the sheath heater shown in FIG.

[Explanation of symbols]

 1 heating element (heater wire) 2 heat sensing element (thermocouple element) 3 heating element terminal 4 heat sensing terminal 5 jacket

Claims (1)

[Claims] 1. A heat-generating body, a heat-sensitive body which is provided at a position where it is thermally coupled to the heat-generating body, with an electric insulator interposed therebetween, and the heat-sensitive body and the heat-generating body are wrapped with the electric insulator interposed therebetween. A temperature-adjusting sheath heater including an outer cover and a terminal for connecting the heating element and the heat-sensitive element to an external circuit.