JP3206730B2 - Driving method of ceramic heating element for infrared light source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a ceramic heating element for an infrared light source which is used as a heating element for an infrared light source.

[0002]

2. Description of the Related Art FIG. 4 shows an example of this type of ceramic heating element for an infrared light source. In this method, a plate-like member having a thickness of about 0.5 mm, which is obtained by forming a raw material powder into a sheet and firing it, is subjected to electric discharge machining to form a zigzag-shaped heating part 11 and linear leads 12a and 12b. This is attached to a ceramic tube 14 with a heat-resistant adhesive 13. 2a and 2b are lead wires.

[0003]

The ceramic heating element for an infrared light source as shown in FIG. 4 is normally driven by a DC voltage so that the light quantity does not fluctuate. However, the temperature of the heating section is 1500 ° C. In the vicinity, when the heat generation time is about several hundred hours, the temperature distribution of the heat generation portion may locally change or deform, and eventually may lead to disconnection.

It has been confirmed that such an abnormality occurs on the positive terminal side. It is presumed that this is not due to the non-uniformity of the material or the like, but to the migration of atoms contained in the ceramic heating element. Therefore, an object of the present invention is to make it difficult for abnormalities such as deformation to occur particularly in the ceramic heating element for an infrared light source, and to improve the reliability thereof.

[0005]

Means for Solving the Problems In order to solve such a problem, according to the invention of claim 1, a ceramic heating element for an infrared light source, which is made of a ceramic material and a part of which is heated to a high temperature by energization, has a thermal response. The apparatus is driven by a high frequency AC voltage having a frequency higher than the above and outside the operating frequency band of the device using the infrared light source.

According to the first aspect of the invention, the ceramic heating element for an infrared light source can be formed of molybdenum disilicide as a main material (the invention of the second aspect ), or can be molybdenum, silicon, or carbonized. It can be formed from silicon (the invention of claim 3 ).

[0007]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. That is, a DC power supply unit 3 and an inverter 4 are provided for the ceramic heating element 1, and the ceramic heating element 1 is, for example, as shown in FIG.
The polarity of the DC power supply is switched at a predetermined cycle, and AC driving is performed. The cycle at this time must be selected so as not to hinder the operation of the apparatus using the ceramic heating element 1 as the infrared light source.

[0008] This point will be supplementarily described by taking an infrared analyzer as an example. FIG. 2 is a characteristic diagram showing the thermal response of the ceramic heating element 1. That is, when a voltage as shown in FIG. 2 (b) is applied to the ceramic heating element 1, the ceramic heating element 1 is subjected to infrared spectroscopy t hours after the start of application (pulse rise) as shown in FIG. 2 (a). Reaches a temperature T required as a light source, and thereafter maintains a constant temperature level until the application is completed (fall of the driving pulse).

According to experiments by the present inventors, the outer dimensions of the heating portion of the ceramic heating element 1 are 0.5 mm × 3 mm × 5 m.
In the case of m, the thermal response frequency is about 10 Hz. Therefore, to obtain a predetermined light level, and
In order to prevent flicker, it is necessary to select the frequency of the AC voltage for driving the ceramic heating element 1 to be higher than this.

Further, the infrared gas analyzer is configured so that a detection signal is repeatedly output in accordance with the rotation of a chopper for converting infrared rays emitted from the ceramic heating element 1 into intermittent light. The frequency band is usually set in the range of several Hz to several tens Hz. It is desirable that the frequency of the AC voltage for driving the ceramic heating element 1 be set to a high frequency outside the detection frequency band of the infrared gas analyzer to be applied.

Considering the above two points, the frequency is determined, and the ceramic heating element 1 is driven by an alternating current as shown in FIG. It has been confirmed from experimental results. This is presumed to be due to the so-called migration of silicon atoms or molybdenum atoms contained in the ceramic heating element being eliminated by the AC driving.

As the material of the ceramic, molybdenum, silicon, silicon carbide (SIC) or the like can be mainly used. However, considering the mechanical strength,
It is desirable to use molybdenum disilicide. 1400 ° C. using molybdenum disilicide for ceramic heating element 1
When a comparative experiment was conducted under the condition of heat generation at the above high temperature, a change in temperature distribution and deformation occurred in the heat generating portion in about 100 hours in the case of DC drive, but several thousand hours elapsed in the case of 50 Hz AC drive. It has been confirmed that there will not be any problems that can be seen with direct current.

Further, the AC voltage is obtained through a DC power supply unit 3 which comprises a rectifier 31, a transformer 32, a converter 33 and the like and outputs DC power, and an inverter 4 which converts the DC power into AC power. But
Of course, the configuration is not limited to this. In other words, its frequency and waveform (sine wave, rectangular wave, trapezoidal wave, etc.)
Can be arbitrarily selected, but since it is used as a light source, it does not affect the thermal responsiveness (frequency higher than the thermal responsiveness). Is satisfied. By doing so, there is no fluctuation of the light source, and driving almost equivalent to DC voltage can be performed.

FIG. 3 illustrates another example of the driving method .
It is an illustration of. In this example, the ceramic heating element has a current duty ratio of approximately 50% (approximately 100% from the viewpoint of the power duty ratio and the ON / OFF duty ratio).
AC drive is performed by a rectangular wave close to. In FIG. 3A, reference numeral 1 denotes a ceramic heating element, 3 denotes a DC power supply, and Q1 to Q4 denote electric field effect transistors (FETs).

Now, Q1 and Q4 are turned on, and Q2 and Q4 are turned on.
3 is turned off, the current flows in the direction of arrow A, and conversely, Q2
When Q3 and Q3 are turned on and Q1 and Q4 are turned off, current flows in the direction of arrow B. Therefore, if the FET elements Q1 to Q4 are switched so as to alternately repeat the states of A and B, and the direction of the current is instantaneously changed, the off-time becomes several as shown by the symbol in FIG. μs,
The ceramic heating element 1 can be driven with a rectangular wave having an on / off duty ratio of approximately 100% and a current duty ratio of approximately 50% such that the on-time is several hundred ms.

Reference numeral 7 denotes current detecting means composed of a resistor.
If the voltage drop v is detected and given as a feedback signal to the control circuit 8, current control can be performed with high accuracy. According to this example, not only does the ceramic heating element 1 not be deformed, but also the fluctuation of the light source is completely eliminated, and the driving substantially equal to the DC voltage can be performed.

[0017]

According to the present invention, the heating portion of the ceramic heating element is driven by an AC voltage having a frequency equal to or higher than a predetermined frequency, so that the change in the amount of light in the heating portion with time is reduced and the life is extended. This has the advantage that reliability can be significantly increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of thermal response characteristics of a ceramic heating element.

FIG. 3 is an explanatory diagram for explaining another example of a driving method .

FIG. 4 is a schematic view showing a structural example of a ceramic heating element.

[Explanation of symbols]

1 ceramic heating element, 2a, 2b lead wire, 3 ...
DC power supply unit, 4 ... inverter, 7 ... current detection means, 8 ...
Control circuit, 11: heating section, 12a, 12b: lead section,
13: heat resistant adhesive, 14 : ceramic tube, 31: rectifier, 32: transformer, 33: converter.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masao Sakanaka 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (56) References JP-A-7-335376 (JP, A) JP-A-7-304325 (JP, A) JP-A-5-296833 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 3/00 H05B 3/20 H05B 3/14 G01N 21/00 G01J 3/10

Claims (3)

(57) [Claims] 1. An infrared light source ceramic heating element made of a ceramic material and partially heated to a high temperature when energized, has a high frequency exceeding its thermal response and outside the operating frequency band of an apparatus using the infrared light source. A method for driving a ceramic heating element for an infrared light source, wherein the method is driven by an AC voltage having a frequency. 2. A ceramic heating element for the infrared light source.
From molybdenum disilicide as the main material
The method for driving a ceramic heating element for an infrared light source according to claim 1, wherein: 3. The ceramic heating element for the infrared light source
With molybdenum, silicon or carbide
The method for driving a ceramic heating element for an infrared light source according to claim 1, wherein the ceramic heating element is formed from i .