JP6288290B2 - Optical emission spectrometer - Google Patents

Description

  The present invention relates to a spectroscope and an emission spectroscopic analysis apparatus including the spectroscope.

  In an emission spectroscopic analyzer, generally, a solid sample, which is a metal or nonmetal, is given energy by arc discharge or spark discharge to evaporate and evaporate the sample, and the emitted light is introduced into a spectrometer. A spectral line having a wavelength peculiar to the element is extracted and detected (for example, see Patent Document 1). In particular, an emission spectroscopic analyzer using a spark discharge as an excitation source is capable of highly accurate analysis. For example, in a production plant such as a steel material or a non-ferrous metal material, a composition analysis in a produced metal body is performed. Widely used.

  The configuration of a conventional general emission spectroscopic analyzer is shown in FIG. The emission spectroscopic analysis apparatus includes an excitation unit 210 that excites and emits a solid sample, a spectroscopic unit 220 that detects wavelength-dispersed light emitted from the sample, a control / processing unit 240 that controls each unit and performs data processing, and the like. Is included.

  The excitation unit 210 includes a discharge generation unit 211, an electrode rod 212, a discharge chamber 213, a sample placement plate 214, and a condenser lens 215. The discharge chamber 213 is provided with an analysis opening opened obliquely upward and a light guide hole 213a for taking out light from the discharge chamber 213, and a sample is provided above the discharge chamber 213 so as to cover the analysis opening. A mounting plate 214 is detachably attached. The sample mounting plate 214 has a central opening 214a that is smaller than the sample S, and the sample S is placed on the sample mounting plate 214 so as to cover the central opening 214a. A part of (analyzed surface) is exposed inside the discharge chamber 213. Inside the discharge chamber 213, an electrode rod 212 for discharge is disposed with its tip directed toward the central opening 214a.

  The discharge generator 211 applies a pulsed high voltage to the electrode bar 212 in synchronization with a predetermined frequency (for example, 400 Hz). The sample S such as iron or non-ferrous metal is excited to emit light by the spark discharge from the electrode rod 212. At this time, in order to prevent the gas component existing in the discharge chamber 213 from being excited and emitted, when measuring the sample S, the discharge chamber 213 is connected to the discharge chamber 213 from the gas supply source 250 such as a gas cylinder through the discharge chamber side conduit 251a. Then, an inert gas (usually argon gas) is supplied, and the air in the discharge chamber 213 is purged by the inert gas. The supply of the inert gas to the discharge chamber 213 is controlled by the control / processing unit 240 of the discharge chamber side opening / closing valve 252a and the discharge chamber side flow rate adjusting unit 253a provided on the discharge chamber side conduit 251a. It is executed by.

  Light emitted by excitation light emission of the sample S passes through a light guide hole 213 a provided in the discharge chamber 213, is condensed by the condenser lens 215, and is introduced into the spectroscopic unit 220. The spectroscopic unit 220 is a so-called Paschen-Lunge spectroscope, and includes an entrance slit 222, a diffraction grating 223, a plurality of photodetectors 224a, 224b, and 224c arranged in parallel on the Roland circle, and a chamber 221 that houses these. Is included. The photodetectors 224a, 224b, and 224c are multichannel photodetectors each composed of a linear CCD sensor or the like. Here, for convenience, only three photodetectors 224a, 224b, and 224c are illustrated, but in a general emission spectroscopic analyzer, about 10 to 15 photodetectors are arranged along a Roland circle. Is done. Light incident on the spectroscopic unit 220 from the excitation unit 210 through the entrance slit 222 is wavelength-dispersed by the diffraction grating 223, and light in a predetermined wavelength range among the wavelength-dispersed light is the multi-channel photodetector. 224a, 224b and 224c are detected all at once.

  At this time, in order to prevent the wavelength dispersion light from being absorbed by oxygen or the like in the air, the inside of the spectroscopic unit 220 is also purged in advance by the inert gas supplied from the gas supply source 250. At that time, first, the exhaust pipe opening / closing valve 229 on the exhaust pipe 228 provided in the chamber 221 is opened, and the spectral section side opening / closing provided on the spectral section side conduit 251b from the gas supply source 250 to the chamber 221 is opened. Open the valve 252b. As a result, the inert gas flows into the chamber 221 and the air present in the chamber 221 is discharged to the outside through the exhaust pipe 228. Note that the flow rate of the inert gas at this time is adjusted by the spectroscopic unit side flow rate regulator 253b. Thereafter, when the exhaust pipe opening / closing valve 229 is closed when a sufficient time has passed for the air in the chamber 221 to be replaced with the inert gas, the pressure of the inert gas in the chamber is reduced from the gas supply source 250. The inflow of the inert gas into the chamber 221 stops when it becomes equal to the supply pressure of active gas (for example, 1.5 atm).

  Detection signals from the respective photodetectors 224a, 224b, and 224c obtained by measuring the sample are input to the control / processing unit 240, and predetermined data processing is performed, whereby a spectral line of a certain element having a certain content is obtained. Based on this, a quantitative analysis for each element is performed.

Japanese Patent Laid-Open No. 2001-83096

  In the emission spectroscopic analysis apparatus as described above, the chamber is often made of a heat insulating material in order to eliminate the influence of distortion of the spectroscope (spectral part 220) due to temperature change. In addition, when a detector including the above-described CCD element is used as the photodetectors 224a, 224b, and 224c, it is desirable to use the detector at as low a temperature as possible in order to eliminate the influence of background due to dark current. However, in order to maintain the temperature of the spectrometer at a relatively low temperature in the vicinity of the operating environment temperature range (ie, room temperature) of the apparatus, both a heater and a cooling device are required as a temperature control mechanism, which increases manufacturing costs. There's a problem. For this reason, the conventional emission spectroscopic analyzer does not include a cooling device, and the inside of the chamber 221 is heated to a temperature somewhat higher than the room temperature by the temperature control mechanism including the heater 225, the fan 226, and the temperature sensor 227. This realizes the temperature control of the spectrometer.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a spectroscope having a function of cooling an internal space and capable of being manufactured at a relatively low cost, and the spectroscope. It is providing the emission-spectral-analysis apparatus which has this.

The spectrometer according to the present invention, which has been made to solve the above problems,
a) a wavelength dispersion element for wavelength-dispersing the light to be measured;
b) a photodetector for detecting light wavelength-dispersed by the wavelength dispersion element;
c) a chamber containing the wavelength dispersion element and the photodetector;
d) a gas outlet for exhausting gas from the inside of the chamber to the outside;
e) an inert gas source filled with an inert gas compressed above atmospheric pressure;
f) cooling means for expanding the inert gas inside the chamber to reduce the temperature in the chamber by introducing the inert gas into the chamber from the inert gas supply source;
g) temperature detecting means for detecting the temperature in the chamber;
h) control means for controlling the cooling means so that the temperature detected by the temperature detection means becomes a predetermined target temperature;
It is characterized by having.

  In the spectrometer according to the present invention, the inert gas compressed to atmospheric pressure or higher is introduced into the chamber from the inert gas supply source, so that the inert gas is greatly expanded in the chamber. At this time, since the expansion of the inert gas occurs in a short time, almost no heat enters and leaves between the inert gas and its surroundings. Therefore, it becomes a state close to adiabatic expansion, the temperature of the inert gas is lowered, and the inside of the spectrometer is cooled. Therefore, by controlling the amount of inert gas introduced from the inert gas supply source while monitoring the temperature in the chamber by the temperature detecting means, the temperature in the chamber can be kept substantially constant and lower than the conventional temperature. Can do.

  As described above, even in a conventional emission spectroscopic analyzer, a sample is measured after introducing an inert gas into the spectrometer (that is, inside the chamber). However, in the conventional spectrometer, after the air in the chamber is replaced with an inert gas, the exhaust pipe opening / closing valve 229 on the exhaust pipe 228 (FIG. 3) provided in the chamber is closed, and the air in the chamber 221 is The temperature of the chamber 221 was controlled in a state where it did not flow out to the outside. Therefore, after the purging operation of the spectrometer is completed, the gas is only introduced into the spectrometer to compensate for the inert gas slightly leaking from the chamber 221, and the introduction of the inert gas as described above is performed. It was not possible to control the temperature. In contrast, in the emission spectroscopic analysis apparatus according to the present invention, the gas in the chamber can be discharged to the outside through the gas discharge port even after the air in the chamber is replaced with an inert gas. An inert gas can be introduced into the chamber.

The spectroscope according to the present invention is
i) heating means including a heater disposed inside the chamber;
Further comprising
It is desirable that the control unit controls the cooling unit and the heating unit so that the temperature detected by the temperature detection unit becomes a predetermined target temperature.

Further, an emission spectroscopic analyzer according to the present invention, which has been made to solve the above problems,
a) a discharge chamber;
b) discharge chamber purge means for purging air in the discharge chamber by introducing an inert gas into the discharge chamber;
c) a discharge generating means for exciting the sample to emit light by generating a discharge inside the discharge chamber;
d) a spectroscope that chromatically disperses the emitted light obtained by the excitation light emission and detects each wavelength;
Have
The spectrometer is the spectrometer according to the present invention,
The discharge chamber purge means is configured to introduce the inert gas into the discharge chamber from the inert gas supply source provided in the spectrometer.

  According to the spectroscopic temperature control mechanism according to the present invention and the emission spectroscopic analysis apparatus according to the present invention configured as described above, it is possible to control the temperature of the spectroscope at a temperature lower than that of the prior art. Therefore, the influence of the background due to the dark current of the photodetector can be reduced. Further, as the cooling means, a gas introduction mechanism (gas cylinder, pipe, valve, flow rate controller, etc.) for purging a spectrometer, which is conventionally provided in many spectrometers, can be used. Therefore, the spectroscope and the emission spectroscopic analyzer according to the present invention can be manufactured at a relatively low cost without causing a significant increase in the number of parts. Further, in order to keep the inside of the spectrometer at a constant temperature, it is not necessary to maintain the inside of the spectrometer at a temperature higher than room temperature as in the prior art, so that an energy saving effect can be expected.

The figure which shows the principal part structure of the emission-spectral-analysis apparatus by one Embodiment of this invention. 5 is a flowchart showing a temperature control method in the spectroscopic unit in the emission spectroscopic analysis apparatus of the embodiment. The figure which shows the principal part structure of the conventional emission-spectral-analysis apparatus.

  Hereinafter, a spectroscope according to the present invention and an emission spectroscopic analysis apparatus including the spectroscope will be described with reference to embodiments.

  FIG. 1 is a diagram showing a main configuration of an emission spectroscopic analyzer according to the present embodiment. Components that are the same as or correspond to those already described in FIG.

  The main difference between the emission spectroscopic analysis apparatus according to this embodiment and the conventional emission spectroscopic analysis apparatus is that an exhaust pipe 128 for exhausting gas from the chamber 121 of the spectroscopic unit 120 (corresponding to the “gas exhaust port” in the present invention). ) Is not provided with an open / close valve for opening and closing the exhaust pipe 128, and based on a detection signal from a temperature sensor 127 (corresponding to "temperature detection means" in the present invention) in the spectroscopic unit 120. The point is to control the introduction of an inert gas (in this case, argon gas) into the section 120. A gas supply source 150 for introducing argon gas into the spectroscopic unit 120 (corresponding to an “inert gas supply source” in the present invention), a spectroscopic unit side pipe 151b, a spectroscopic unit side opening / closing valve 152b, and a spectroscopic unit side As the flow rate adjusting unit 153b (corresponding to the “cooling means” in the present invention), the one conventionally provided in the emission spectroscopic analyzer for purging the air in the spectroscopic unit 120 can be used. Further, a temperature sensor 127 for detecting the temperature in the chamber 121, and a heater 125 and a fan 126 for heating the inside of the chamber 121 can be used as those conventionally provided for temperature control of the spectroscopic unit 120. is there.

The control / processing unit 140 is configured by dedicated hardware, general-purpose hardware (such as a personal computer), or a combination thereof. An input unit 141 for receiving an instruction from the user is connected to the control / processing unit 140. When measuring a sample, the target temperature T in the spectroscopic unit 120 and the target are previously measured from the user via the input unit 141. An allowable value Δt of temperature fluctuation from the temperature T is input. Here, the target temperature T can be freely set by the user. However, from the viewpoint of reducing the influence of dark current in the photodetectors 124a, 124b, and 124c composed of linear CCD sensors, the target temperature T is lower than room temperature. It is desirable to set it to a low temperature. When the target temperature T and the temperature fluctuation allowable value Δt are input, the control / processing unit 140 sets the value of T + Δt to the upper limit value t _max of the temperature in the chamber 121 and sets the value of T−Δt to the chamber 121. _Is stored in a memory or the like provided in the control / processing unit 140 as the lower limit value t _min of the internal temperature.

  Subsequently, when the user performs a predetermined operation with the input unit 141, the control / processing unit 140 causes the spectroscopic unit side opening / closing valve provided in the spectroscopic unit side conduit 151 b from the gas supply source 150 to the chamber 121 of the spectroscopic unit 120. By opening 152b, the air in the chamber 121 is purged with argon gas. At this time, the high-pressure argon gas supplied from the gas cylinder of the gas supply source 150 flows into the chamber 121 at approximately atmospheric pressure, so that the argon gas expands greatly. Since the expansion of the argon gas occurs in a short time, almost no heat enters and leaves between the argon gas and its surroundings. Therefore, it becomes a state close to adiabatic expansion, the temperature of the argon gas is lowered, and the inside of the chamber 121 is at a lower temperature than before the introduction of the argon gas. Then, when a sufficient time has passed for the inside of the chamber 121 to be replaced with argon gas, the control / processing unit 140 controls the spectroscopic unit side flow rate adjusting unit 153b to adjust the flow rate of argon gas, The supply of argon gas is continued at such a flow rate that the state in which the interior of the chamber 121 is filled with argon gas is maintained (hereinafter, this state is referred to as a “low flow” state). Note that the gas in the chamber 121 can always flow out from the exhaust pipe 128 and the exhaust pipe 128 has a sufficiently large inner diameter, so even if the argon gas is introduced as described above, The atmospheric pressure in the chamber 121 does not increase more than a certain level, and is always maintained at a lower pressure (for example, approximately atmospheric pressure) than the supply pressure of argon gas from the gas supply source 150. Therefore, even in the state where the flow rate is “small” as described above, the argon gas expands inside the chamber 121. However, at this time, since the amount of the introduced gas is small, the temperature in the chamber 121 does not greatly decrease.

Subsequently, the control / processing unit 140 starts temperature control of the spectroscopic unit 120 according to the flowchart of FIG. That is, based on the detection signal of the temperature sensor 127, chamber 121 internal temperature (hereinafter referred to as "chamber temperature t") is equal to or less than the lower limit value _{t min} of the above (step _{S11), t min} In the case of the following, the heater 125 and the fan 126 provided in the chamber 121 are turned on to heat the chamber 121 (step S12). If the chamber temperature t is not less than t _min in step S11, the process proceeds to step S15 described later.

After the heater 125 and the fan are turned on in step S12 and the chamber 121 is heated, when the chamber temperature t exceeds the lower limit value _tmin , the control / processing unit 140 turns off the heater 125 and the fan 126. Heating in the chamber 121 is stopped (steps S13 and S14).

Subsequently, the control and processing unit 140, chamber temperature t is equal to or greater than or equal to the upper limit value t _max of above (step S15), and when was t _max or more, the spectroscopic unit side flow rate adjustment The flow rate of argon gas is increased by the unit 153b to increase the amount of gas introduced into the chamber 121 (step S16). This state is referred to as a flow rate “high” state. If the chamber temperature t is not equal to or higher than _tmax in step S15, the process returns to step S11.

Even when the flow rate is set to “high” in step S <b> 16, the argon gas pressure in the chamber 121 is lower than the argon gas pressure in the gas supply source 150. Arise. In addition, the amount of argon gas introduced at this time is larger than when the flow rate is “small”, and the temperature drop due to expansion also increases, so the chamber temperature t decreases. Thereafter, when the chamber internal temperature t falls below the upper limit value t _max , the control / processing unit 140 reduces the opening of the spectroscopic unit side opening / closing valve 152b to return it to the “low” flow rate, thereby cooling the chamber 121. Is stopped (steps S17 and S18). After that, it returns to step S11 and continues the above temperature control.

  When measuring a sample in the emission spectroscopic analysis apparatus according to the present embodiment, the user first sets the sample S on the sample mounting plate 114 of the excitation unit 110 and then starts the measurement on the control / processing unit 140. Instruct. Then, the control / processing section 140 opens the discharge chamber side opening / closing valve 152a provided in the discharge chamber side pipe line 151a from the gas supply source 150 to the discharge chamber 113, whereby the air inside the discharge chamber 113 is changed to argon gas. Purge with. Then, when a predetermined time has elapsed from the start of the purge of the discharge chamber 113, a pulsed high voltage is applied to the electrode bar 112 from the discharge generator 111, and the sample S is excited and emitted by spark discharge from the electrode bar 112. . The emitted light obtained at this time passes through a light guide hole 113 a provided in the discharge chamber 113, is condensed by the condenser lens 115, and is emitted to the spectroscopic unit 120. The emitted light emitted from the excitation unit 110 enters the chamber 121 of the spectroscopic unit 120 through the entrance slit 122 and is wavelength-dispersed by the diffraction grating 123. Of the wavelength-dispersed light, light in a predetermined wavelength range is simultaneously detected by the photodetectors 124a, 124b, and 124c.

  Note that while the purge of the discharge chamber 113 and the measurement of the sample S are performed as described above, the temperature control of the spectroscopic unit 120 according to the flowchart of FIG. 2 is continued, and the measurement of the sample S is completed, and the user Steps S11 to S18 are repeatedly executed until an instruction for terminating the emission spectroscopic analyzer is input.

  As mentioned above, although the specific example was given and demonstrated about the form for implementing this invention, this invention is not limited to said example, A change is accept | permitted suitably in the range of the meaning of this invention. For example, in the above example, the purge of the discharge chamber and the spectroscopic unit and the cooling of the spectroscopic unit are performed by argon gas. However, these may be performed by other inert gas, for example, nitrogen gas. However, when nitrogen element in the sample is to be measured, if nitrogen gas is used for purging the discharge chamber, the nitrogen gas is excited and emitted in the discharge chamber, which may affect the measured value of the nitrogen element. . Therefore, in such a case, it is desirable to use an inert gas other than nitrogen.

  In the above example, the temperature control of the spectrometer is performed by switching the gas flow rate between “large / small” and the heater “ON / OFF” according to the chamber temperature t. The temperature control method in the present invention is not limited to this, and for example, the flow rate of the inert gas introduced into the chamber and the energization amount to the heater may be changed in proportion to the in-chamber temperature t.

  Further, in the above example, the “gas exhaust port” in the present invention is a pipe (exhaust pipe 128) penetrating the wall surface of the chamber and no valve is provided on the exhaust pipe 128. It is also possible to provide a valve for the spectroscope purge operation and the subsequent temperature control to keep the valve open at all times. Alternatively, when the temperature control is performed, the control / processing unit 140 may close the valve as appropriate, or reduce the opening of the valve. Specifically, in the temperature control shown in the flowchart of FIG. 2, when the gas flow rate is “small”, the valve is closed (or the opening of the valve is reduced), and when the gas flow rate is “large”, the valve is closed. It is conceivable to perform control such as opening the valve (or increasing the opening of the valve). Thereby, the effect of reducing the outflow amount of the gas from the chamber and suppressing the consumption of the argon gas can be expected.

    The “gas discharge port” discharges the gas in the chamber to the outside at least when performing the purge operation of the spectrometer and the subsequent temperature control, and discharges the gas from the inert gas supply source into the chamber. Any material can be used as long as it can be lower than the supply pressure (preferably substantially atmospheric pressure). For example, it can be a through hole provided in the wall surface of the chamber.

  In the above example, the spectroscope according to the present invention is applied to an emission spectroscopic analysis device that performs excitation light emission of a solid sample by discharge. However, the present invention is not limited to this, and various analysis devices including a spectroscope, for example, The present invention can be similarly applied to an ICP emission spectroscopic analyzer.

110, 210 ... excitation part 111, 211 ... discharge generation part 112, 212 ... electrode rod 113, 213 ... discharge chamber 114, 214 ... sample mounting plate 120, 220 ... spectroscopic part 121, 221 ... chamber 122, 222 ... entrance slit 123, 223 ... Diffraction gratings 124a to c, 224a to c ... Photo detectors 125, 225 ... Heaters 126, 226 ... Fans 127, 227 ... Temperature sensors 128, 228 ... Exhaust pipes 229 ... Exhaust pipe opening / closing valves 140, 240 ... Control Processing unit 141: Input unit 150, 250 ... Gas supply source 151a, 251a ... Discharge chamber side conduits 152a, 252a ... Discharge chamber side open / close valve 153a, 253a ... Discharge chamber side flow rate adjustment unit 151b, 251b ... Spectral unit side tube Paths 152b, 252b ... spectral part side opening / closing valves 153b, 253b ... spectral part side flow rate adjusting parts

Claims (2)

a) a discharge chamber;
b) discharge chamber purge means for purging air in the discharge chamber by introducing an inert gas into the discharge chamber;
c) a discharge generating means for exciting the sample to emit light by generating a discharge inside the discharge chamber;
d) a spectroscope that chromatically disperses the emitted light obtained by the excitation light emission and detects each wavelength;
Have
The spectrometer is
e) a wavelength dispersion element that wavelength-disperses the emitted light;
f) a photodetector for detecting light wavelength-dispersed by the wavelength dispersion element;
g) a chamber containing the wavelength dispersive element and the photodetector;
h) a gas outlet for exhausting gas from the inside of the chamber to the outside;
i) an inert gas source filled with an inert gas compressed above atmospheric pressure;
j) a cooling means for expanding the inert gas inside the chamber by introducing the inert gas into the chamber from the inert gas supply source to lower the temperature in the chamber;
k) temperature detecting means for detecting the temperature in the chamber;
l) control means for controlling the cooling means so that the temperature detected by the temperature detection means becomes a predetermined target temperature;
Having
The emission spectroscopic analyzer characterized in that the discharge chamber purge means introduces the inert gas into the discharge chamber from the inert gas supply source provided in the spectrometer. Furthermore,
m) heating means including a heater disposed inside the spectrometer;
Have
The emission spectroscopic analysis according to claim 1 , wherein the control unit controls the cooling unit and the heating unit such that a temperature detected by the temperature detection unit becomes a predetermined value. apparatus.

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