Elemental analysis device

Abstract

In order to provide an elemental analysis device whereby an electrode tip is made replaceable, but air can be prevented from becoming trapped inside the electrode during replacement, and whereby error in elemental analysis can be reduced, the present invention is an elemental analysis device 100 in which a crucible MP containing a sample is held between a first electrode 31 and a second electrode 32, and an electric current is passed between the first electrode 31 and the second electrode 32, thereby heating the sample, wherein the second electrode 32 comprises a second electrode body 32B provided with a substantially cylindrical distal-end part, a second electrode tip 32C provided to the distal-end surface of the second electrode body 32B, a cap 32D which holds the second electrode tip 32C between the second electrode body 32B and the cap 32D in a state in which a portion of the second electrode tip 32C is exposed to the outside, and a second screwing structure 32S comprising a male threaded part S1 and a female threaded part S2 formed between the second electrode body 32B and the cap 32D, the second screwing structure 32S further comprising a gas venting groove 321 which extends in the pitch direction in the male threaded part S1 and / or the female threaded part S2 and is formed by cutting off a portion of the screw threads.

Description

Technical Field

[0001] The present invention relates to an elemental analyzer that analyzes elements contained in a sample based on a sample gas generated by heating the sample.

Background Art

[0002] An elemental analyzer is used to quantify elements such as nitrogen (N), hydrogen (H), oxygen (O), etc. contained in a sample. Such an elemental analyzer sandwiches a graphite crucible containing a sample between a pair of electrodes in a heating furnace, and directly passes an electric current through the crucible to heat the crucible and the sample. The sample gas generated by heating is led out from the heating furnace to the outside, and the concentrations of various components are measured by an analysis mechanism composed of, for example, a NDIR (Non Dispersive Infrared) gas analyzer or a TCD (Thermal Conductivity Detector).

[0003] For example, the heating furnace of the elemental analyzer shown in Patent Document 1 includes an upper electrode having a housing recess formed inside, and a lower electrode on which the crucible is placed. By raising the lower electrode, the crucible is housed in the housing recess while being sandwiched between the upper electrode and the lower electrode.

[0004] This lower electrode includes a substantially two-stage cylindrical lower electrode body on which the crucible is placed on the tip side, a lower electrode chip provided on the tip surface of the lower electrode body, and a cap for fixing the lower electrode chip to the lower electrode body. Specifically, a screwing structure composed of a male screw and a female screw is formed between the outer peripheral surface of the tip portion of the lower electrode body and the inner peripheral surface of the cap, and only the lower electrode chip can be replaced.

[0005] However, when screwing the cap onto the lower electrode body, air is trapped in the gap between the male and female threads. When the furnace is filled with carrier gas to heat the sample for elemental analysis, the air trapped in the lower electrode may leak out as a component other than the sample gas. Especially when measuring trace amounts of nitrogen (N) contained in the sample gas, even a small amount of air leakage will cause a large measurement error due to the nitrogen (N) contained in the air. That is, since the lower electrode chip is configured to be replaceable, an error factor in elemental analysis has been formed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made in view of the above problems, and while making the electrode chip replaceable, when starting elemental analysis, when the furnace is filled with carrier gas to discharge the air in the furnace, the air trapped in the electrode is quickly discharged, and it is possible to provide an elemental analyzer that can prevent a measurement error caused by air mixing when the sample gas is generated.

Means for Solving the Problems

[0008] That is, the elemental analyzer according to the present invention is an elemental analyzer that sandwiches a crucible containing a sample between a first electrode and a second electrode and heats the sample by passing an electric current between the first electrode and the second electrode, wherein the second electrode includes a second electrode body having a substantially cylindrical tip portion, a second electrode chip provided on the tip surface of the second electrode body, a cap that sandwiches a part of the second electrode chip in a state of being exposed to the outside between the second electrode body, and a second screw structure including a male screw portion and a female screw portion formed between the second electrode body and the cap, and the second screw structure further includes a gas vent groove formed so as to extend in the pitch direction and notch a part of the thread in at least one of the male screw portion or the female screw portion.

[0009] If it is such a thing, since the gas vent groove is formed, when filling the furnace with a carrier gas and discharging the air in the furnace prior to heating the sample during elemental analysis, the air in the gap between the male screw portion and the female screw portion can be discharged from the gas vent groove to the outside of the second electrode. Therefore, even if there is air trapped inside the second electrode while the second electrode chip can be replaced, such air will not mix into the sample gas, and it is possible to prevent the occurrence of measurement errors. In addition, particularly when measuring a trace amount of nitrogen (N) contained in the sample gas, it becomes possible to improve the measurement accuracy compared to the conventional method.

[0010] In order to be able to fix the second electrode chip with the cap in a state where the second electrode chip is accurately positioned with respect to the second electrode body, it is sufficient that a recess is formed on the tip surface of the second electrode body into which a part of the second electrode chip is fitted.

[0011] In order to easily attach an O-ring for maintaining internal sealing to the second electrode in a state where the second electrode is inserted into the accommodation recess of the first electrode and to fully exhibit its function, a stepped portion is formed on the tip side of the second electrode body, and an O-ring is provided in a ring-shaped groove formed by the stepped portion and the edge of the cap in a state where the cap is screwed to the second electrode body. Any structure may be used as long as it meets this condition.

[0012] In order to ensure that air present between the screw threads is sufficiently discharged to the outside through the gas vent groove during the process of attaching the cap to the second electrode body, a gas vent passage communicating the inside of the second screw structure and the outside of the second electrode is formed, and any structure may be used as long as the gas vent groove forms at least a part of the gas vent passage.

[0013] In order to ensure that air flowing in the advancing direction of the cap through the gas vent groove is sufficiently discharged to the outside during the process of screwing the cap onto the second electrode body, it is sufficient to have a top surface portion including an exposure port for exposing the second electrode chip to the outside and a pressing plate provided around the exposure port for pressing the second electrode chip against the tip surface of the second electrode body in a state where the cap is screwed to the second electrode body, and a side surface portion having a generally cylindrical shape with an internal thread portion formed on the inner peripheral surface.

[0014] In order to make it difficult for the ability to discharge air from the second electrode to the outside to decrease even if the gas vent groove is deformed or dust accumulates due to repeated analysis, it is sufficient that the cap further includes one or more ventilation ports formed outside the exposure port on the top surface portion.

[0015] In order to increase the route for discharging air not only from the top surface side but also from the end side of the cap and further improve the air discharge performance, it is sufficient that the cap further includes one or more gas discharge grooves extending from the inner peripheral side to the outer peripheral side on the side surface portion.

[0016] As one aspect of forming the gas venting channel such that air within the second threaded structure is discharged to the outside of the second electrode from the vent or the gas discharge groove, examples include those in which a gas venting groove is formed in the female threaded portion of the cap.

[0017] Even if, for example, a gas venting groove is formed in the male threaded portion of the electrode body, a gas venting channel can be formed to communicate the interior of the second threaded structure and the outside of the second electrode through, for example, the vent of the cap, and air present between the threads can be discharged to the outside.

[0018] Even when a gas venting groove is formed in the male threaded portion of the electrode body, in order to be able to discharge air from below through the gas discharge groove, a ring-shaped recess formed near the base end of the male threaded portion of the second electrode body may be further provided, and it is sufficient if the ring-shaped recess communicates with the gas venting groove formed in the male threaded portion.

[0019] In order to make it easier to extract only the sample gas generated from the sample by heating the crucible in a sealed space, examples include those in which the first electrode includes a housing recess in which the crucible is housed, and the second electrode is configured to be movable between a first position where the crucible is clamped within the housing recess between the first electrode and a second position spaced a predetermined distance from the first position where the crucible is disposed outside the housing recess.

[0020] As a specific embodiment of the second electrode, examples include those in which the second electrode is configured such that the crucible is placed thereon.

Advantages of the Invention

[0021] In the elemental analyzer according to the present invention as described above, in the screwing structure formed between the second electrode body and the cap, an air vent groove is formed so as to extend in the pitch direction and notch the thread, so that when the second electrode chip is attached, the male screw portion and the female screw portion can be screwed together to discharge the air in the gap to the outside. Therefore, it is possible to prevent components other than the sample gas from leaking from the second electrode during elemental analysis and causing an analysis error.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Explanation of Reference Numerals

[0023] 100 ··· Elemental analysis device 1 ··· Supply source 2 ··· Purifier 3 ··· Heating furnace 31 ··· First electrode 31B ··· First electrode body 311 ··· Accommodating recess 312 ··· Outlet hole 313 ··· Sample input hole 31C ··· First electrode chip 314 ··· Insertion cylinder 315 ··· Flange portion 316 ··· Through hole 317 ··· Gas flow groove 31S ··· First screwing structure 32 ··· Second electrode 32B ··· Second electrode body ST ··· Step portion 322 ··· Recess 32C ··· Second electrode chip 32D ··· Cap 32S ··· Second screwing structure 323 ··· Exposed port 324 ··· Pressing plate 325 ··· Vent hole 326 ··· Gas discharge groove 327 ··· Ring-shaped recess 32F ··· Gas venting flow path 4 ··· Dust filter 5 ··· CO detection unit 6 ··· Oxidizer 7 ··· CO2 detection unit 8 ··· H2O detection unit 9 ··· Removal mechanism 10 ··· Mass flow controller 11 ··· N2 detection unit (thermal conductivity analysis unit)

Mode for carrying out the invention

[0024] The elemental analyzer 100 according to the first embodiment of the present invention will be described with reference to the respective drawings. FIG. 1 shows a schematic of the elemental analyzer 100 of the first embodiment. The elemental analyzer 100 heats and melts, for example, a metal sample, a ceramic sample, etc. (hereinafter simply referred to as a sample) accommodated in a graphite crucible MP, and analyzes the sample gas generated at that time, thereby measuring the amount of elements contained in the sample. In the first embodiment, C (carbon), H (hydrogen), and N (nitrogen) contained in the sample are the measurement targets.

[0025] As shown in FIG. 1, the elemental analyzer 100 includes a heating furnace 3 for heating the sample accommodated in the crucible MP, an introduction flow path L1 for introducing a carrier gas into the heating furnace 3, and a derivation flow path L2 for deriving a mixed gas of the carrier gas and the sample gas from the heating furnace 3. More specifically, the elemental analyzer 100 is composed of a heating furnace 3, each device provided in the introduction flow path L1 or the derivation flow path L2, and a control arithmetic mechanism COM that controls each device and performs arithmetic processing such as the measured concentration. The control arithmetic mechanism COM is a so-called computer equipped with, for example, a CPU, a memory, an A / D converter, a D / A converter, and various input / output means. The program stored in the memory is executed, and various devices cooperate to exhibit the function as a measurement value calculation unit C1 described later. Further, the control arithmetic mechanism COM also exhibits a function as a display unit (not shown) that displays the concentrations of various elements contained in the sample based on the outputs of, for example, a CO detection unit 5, a CO2 detection unit 7, an H2O detection unit 8, and an N2 detection unit 11 described later.

[0026] Each part will be described in detail.

[0027] A gas cylinder, which is a supply source 1 of the carrier gas, is connected to the proximal end of the introduction flow path L1. In the first embodiment, He (helium) is supplied into the introduction flow path L1 from the supply source 1. Further, a purifier 2 for removing a minute amount of hydrocarbon contained in the carrier gas and increasing the purity of the carrier gas is provided on the introduction flow path L1.

[0028] The purifier 2 is made of a material that physically adsorbs hydrocarbons contained in the carrier gas and does not substantially adsorb the carrier gas itself. Note that the material forming the purifier 2 does not chemically react with the carrier gas or hydrocarbons. That is, this purifier 2 is also used, for example, in a gas chromatograph, and a zeolite-based molecular sieve can be used as the material forming the purifier 2. Also, the material forming the purifier 2 may be silica gel, activated carbon, ascarite, or the like. This purifier 2 can desorb the adsorbed molecules by heating, for example, and regenerate its adsorption capacity.

[0029] The heating furnace 3 is configured to sandwich the graphite crucible MP containing the sample between a pair of electrodes and pass a direct current directly through the crucible MP to heat the crucible MP and the sample. When heating the sample, the pressure in the heating furnace 3 is adjusted by a pressure regulating valve (not shown) provided on the upstream side of the heating furnace 3 so that the pressure in the heating furnace 3 becomes 60 kPa or less, more preferably 40 kPa or less. Details of the electrodes of the heating furnace 3 will be described later.

[0030] Next, each device provided on the derivation channel L2 will be described.

[0031] On the derivation channel L2, a dust filter 4, a CO detector 5, an oxidizer 6, a CO2 detector 7, an H2O detector 8, a removal mechanism 9, a mass flow controller 10, and an N2 detector 11 which is a thermal conductivity analyzer are arranged in this order from the upstream side.

[0032] The dust filter 4 filters out soot and the like contained in the sample gas and removes dust.

[0033] The CO detector 5 detects CO (carbon monoxide) contained in the mixed gas that has passed through the dust filter 4 and measures its concentration. It is composed of an NDIR (non-dispersive infrared gas analyzer). This CO detector 5 operates effectively when the oxygen contained inside the sample is at a high concentration due to its measurement accuracy. Specifically, it is preferable to measure CO of 150 ppm or more.

[0034] The oxidizer 6 oxidizes CO and CO2 contained in the mixed gas that has passed through the CO detector 5, and also oxidizes H2 to H2O (water) to generate water vapor. In the first embodiment, copper oxide is used as this oxidizer 6, and its temperature is maintained at 450°C or lower by a heating resistor provided around it.

[0035] The CO2 detector 7 is an NDIR that detects CO2 in the mixed gas that has passed through the oxidizer 6 and measures its concentration. This CO2 detector 7 operates effectively when the oxygen contained in the sample is at a low concentration (for example, less than 150 ppm) from the perspective of measurement accuracy.

[0036] The H2O detector 8 is an NDIR that detects H2O in the mixed gas that has passed through the CO2 detector 7 and measures its concentration. Note that the flow path from the oxidizer 6 to the H2O detector 8 is configured such that the temperature of the mixed gas is maintained at 100°C or higher so that H2O remains in the state of water vapor. In this way, a measurement error due to dew condensation is prevented from occurring in the H2O detector 8.

[0037] The removal mechanism 9 adsorbs and removes CO2 and H2O contained in the mixed gas. This removal mechanism 9 is composed of an adsorbent, and for example, the same one as the purifier 2 provided in the introduction flow path L1 described above is used.

[0038] The mass flow controller 10 is a flow control device in which a flow sensor M1, a control valve M2, and a flow controller M3 are integrated into one package. This mass flow controller 10 supplies the mixed gas maintained at a constant set flow rate to the N2 detector 11 on the downstream side. Therefore, even if the pressure of the mixed gas fluctuates due to the removal mechanism 9, the pressure of the mixed gas in the N2 detector 11 can be maintained at a value suitable for measurement. In the first embodiment, the mass flow controller 10 is configured to operate at a pressure lower than 60 kPa, for example, to operate even when the differential pressure before and after is 20 kPa, so that the pressure in the heating furnace 3 can be maintained at 60 kPa.

[0039] The N2 detector 11 is a TCD (thermal conductivity detector), and measures the concentration of N2, which is a predetermined component contained in the mixed gas, from the change in the thermal conductivity of the mixed gas and the flow rate of the supplied mixed gas. That is, since the mixed gas supplied to the N2 detector 11 is composed almost entirely of the carrier gas and N2, the concentration of N2 contained in the mixed gas becomes a value corresponding to the change in the measured thermal conductivity. Also, in the first embodiment, no flow meter is provided on the downstream side of the N2 detector 11, and the downstream side of the N2 detector 11 is directly connected to the exhaust port of the outlet channel L2.

[0040] Measurement signals indicating the concentrations of the respective components obtained by each detector are input to the measured value calculation unit C1. The measured value calculation unit C1 calculates the concentrations of O, H, and N contained in the sample based on each measurement signal. When calculating the oxygen concentration contained in the sample, the measured value calculation unit C1 outputs the oxygen concentration obtained by the CO detector 5 as the output value when the oxygen concentration inside the sample is equal to or higher than a predetermined threshold value (150 ppm), and outputs the oxygen concentration obtained by the CO2 detector 7 as the output value when it is less than the threshold value.

[0041] Finally, the pair of electrodes provided in the heating furnace 3 will be described in detail.

[0042] As shown in the cross-sectional view of FIG. 2 and the perspective views of FIGS. 3 and 4, the heating furnace 3 includes a first electrode 31, which is an upper electrode fixed above, and a second electrode 32, which is a lower electrode provided below and on which the crucible MP is placed.

[0043] As shown in Fig. 3(a), the first electrode 31 is a substantially two-stage cylindrical electrode with an upper part being a thin cylindrical shape and a lower part being a flat disk shape. As shown in the cross-sectional view of Fig. 2, this first electrode 31 includes a first electrode body 31B in which a hollow cylindrical accommodation recess 311 for accommodating the crucible MP is formed at the lower central part, and a first electrode chip 31C detachably provided with respect to the first electrode body 31B within the accommodation recess 311. The first electrode chip 31C is a part that directly contacts the upper edge of the crucible MP having a substantially cylindrical shape and is consumed by repeating elemental analysis. Further, the first electrode body 31B is formed of, for example, copper, and the first electrode chip 31C is formed of, for example, a copper alloy containing tungsten. That is, the first electrode chip 31C is formed of a material having a higher hardness than the first electrode body 31B.

[0044] The first electrode body 31B forms the outer shape of the first electrode 31. As shown in the cross-sectional view of Fig. 2, a cylindrical accommodation recess 311 extends in the vertical direction at the center of the flat disk-shaped part. Further, a sample gas outlet hole 312 extending in the horizontal direction is formed so as to open on the side surface of the accommodation recess 311. Further, a sample injection hole 313 for injecting a sample into the crucible MP is formed on the upper surface side of the accommodation recess 311. The sample injection hole 313 is a substantially thin hollow cylindrical hole having a smaller diameter than the accommodation recess 311 and is formed so as to extend in the vertical direction along the central axis of the first electrode 31.

[0045] The first electrode chip 31C has a generally two-stage cylindrical shape, and as shown in FIGS. 2 and 3(a), it includes a thin cylindrical insertion tube 314 inserted into the sample injection hole 313 of the first electrode body 31B, and a flat plate-shaped flange portion 315 that extends radially on the lower end side of the insertion tube 314. Further, the first electrode chip 31C further includes a through hole 316 formed so as to penetrate the insertion tube 314 and the flange portion 315 in the axial direction, and in the flange portion 315, a gas outlet groove having one end opening at least on the side surface of the through hole 316 and formed to extend in the radial direction. As shown in the lower end face view of the first electrode chip 31C in FIG. 3(b), four gas outlet grooves are provided at 90° intervals so as to be axisymmetric with respect to the central axis. As shown in FIG. 2(b), the radially inner end of the gas outlet groove opens inside the crucible MP. In the first embodiment, the other end of the gas outlet groove is opened on the outer peripheral surface of the flange portion 315. That is, the sample gas generated by heating from the sample in the crucible MP flows out of the crucible MP to the outside via the gas outlet groove. Thereafter, the sample gas flows out from the accommodation recess 311 to the lead-out flow path L2 via the lead-out hole 312 formed in the first electrode body 31B.

[0046] A fixing structure for detachably fixing the first electrode chip 31C to the first electrode body 31B is provided between the first electrode body 31B and the first electrode chip 31C. More specifically, a first screwing structure 31S composed of a male screw portion S1 and a female screw portion S2 is formed as a fixing structure between the outer peripheral surface of the insertion tube 314 of the first electrode chip 31C and the inner peripheral surface of the sample injection hole 313 of the first electrode body 31B. The first electrode chip 31C is configured to be detachable from the first electrode body 31B by this first screwing structure 31S. Also, there are no grooves notched in the pitch direction on the threads of the first screwing structure 31S. Therefore, in a state where the first screwing structure 31S is fully screwed, the flange portion 315 is in close contact with the upper wall surface of the accommodation recess 311, and the male screw portion S1 and the female screw portion S2 are in close contact without a gap. For this reason, it is possible to prevent the sample gas flowing out from the crucible MP from being stored in the gap between the first electrode body 31B and the first electrode chip 31C or flowing backward.

[0047] Next, the second electrode 32 will be described with reference to FIGS. 2 and 4.

[0048] The second electrode 32 is configured to be movable in the vertical direction by, for example, an air cylinder (not shown), and a part thereof is inserted into the accommodation recess 311 together with the crucible MP on which it is placed. Specifically, the second electrode 32 is configured to be movable between a first position where the crucible MP in the accommodation recess 311 is clamped between the second electrode 32 and the first electrode 31, and a second position spaced a predetermined distance from the first position where the crucible MP is disposed outside the accommodation recess 311.

[0049] The second electrode 32 also includes a second electrode body 32B having a substantially stepped cylindrical shape, a second electrode chip 32C having a thin disk shape provided on the tip surface of the second electrode body 32B, and a cap 32D that fixes the second electrode chip 32C to the second electrode body 32B and forms an exposure port for exposing the contact surface of the second electrode chip 32C with the crucible MP to the outside. Note that the second electrode body 32B and the cap 32D are formed of an alloy containing copper, and the second electrode chip 32C is formed of an alloy containing tungsten.

[0050] As described above, the second electrode 32 is composed of three separate parts, and only the second electrode chip 32C is configured to be replaceable. More specifically, a second screw structure 32S including a male screw portion S1 and a female screw portion S2 is formed between the outer peripheral surface of the tip end portion of the second electrode body 32B and the inner peripheral surface of the cap 32D.

[0051] The second screwing structure 32S has a different structure from the first screwing structure 31S formed on the first electrode 31. That is, as shown in FIG. 4, a gas vent groove 321 is formed in the male screw portion S1 of the second screwing structure 32S so as to extend in the pitch direction of the screw and notch a part of the thread. The gas vent groove 321 is configured to notch, for example, up to the height of the thread root with respect to the thread, but it may be formed shallower. Also, four gas vent grooves 321 are provided at 90° intervals so as to be axially symmetric with respect to the central axis of the second electrode 32. The number of gas vent grooves 321 provided is not limited to four, and it may be less or more. Also, they do not necessarily have to be arranged axially symmetrically.

[0052] Since this gas vent groove 321 is formed, even if the air in the gap between the threads of the second screwing structure 32S is trapped when the cap 32D is attached, for example, when replacing the air existing from the inside of the heating furnace 3 with the carrier gas, the air inside the second electrode 32 can be discharged from the gas vent groove 321 to the outside of the second electrode 32.

[0053] The second electrode body 32B is formed with a recess 322 on the tip surface so that the back surface side of the second electrode chip 32C is substantially fitted, and a step portion ST facing the edge of the cap 32D is formed on the tip side as shown in FIG. 2. The tip side of the second electrode 32 is formed with the smallest diameter at the tip surface where the second electrode chip 32C is attached, and expands to substantially the same outer diameter as the outer diameter of the O-ring SL attached at the step portion ST.

[0054] Specifically, by previously fitting the second electrode chip 32C into the recess 322, the alignment of the second electrode chip 32C with respect to the second electrode body 32B can be performed. Also, by screwing the cap 32D onto the second electrode body 32B with the position of the second electrode chip 32C determined, the second electrode chip 32C can be fixed while maintaining its correct position.

[0055] An O-ring SL is disposed in a ring-shaped groove RT formed between a stepped portion ST of the second electrode body 32B and an edge of the cap 32D. That is, before the cap 32D is attached, there is no member that restricts the axial movement of the O-ring SL. Further, the ring-shaped groove RT is formed slightly larger than the thickness dimension of the O-ring SL. In order to sandwich the crucible MP with each electrode and pass an electric current, in the process of inserting the second electrode 32 into the accommodation recess 311 of the first electrode body 31B, the O-ring SL slips toward the edge side of the cap 32D and abuts to form a seal in the accommodation recess 311. With such a configuration, it is not necessary to attach the O-ring SL in a state where its inner diameter is extremely enlarged as in the prior art, and the attachment work of the O-ring SL can be simplified.

[0056] The cap 32D includes a top surface portion D1 and a side surface portion D2. The top surface portion D1 is provided with an exposure port 323 for exposing the second electrode chip 32C to the outside, and a pressing plate 324 provided around the exposure port 323 for pressing the second electrode chip 32C against the tip surface of the second electrode body 32B in a state where the cap 32D is screwed onto the second electrode body 32B. The side surface portion D2 has a female screw portion S1 formed on its inner peripheral surface. Further, a gap is formed between the end surface of the side surface portion D2 and the second electrode body 32B so that air passing through the air vent groove 321 from the lower edge of the cap 32D does not prevent the discharge of the second electrode 32 to the outside even when the cap 32D is completely screwed onto the second electrode body 32B.

[0057] In the element analyzer 100 configured as described above, since the first electrode chip 31C is detachably configured with respect to the first electrode body 31B by the first screwing structure 31S, when the first electrode chip 31C is consumed due to repeated element analysis, only the first electrode chip 31C can be replaced. Therefore, it is not necessary to replace the entire first electrode 31 including the first electrode body 31B as in the prior art.

[0058] In addition, since the second electrode chip 32C is detachably configured by a second screwing structure 32S formed between the second electrode body 32B and the cap 32D, only this part can be replaced when the second electrode chip 32C is consumed.

[0059] From these facts, the labor and cost required for the replacement work of consumables necessary for continuing elemental analysis in the heating furnace 3 can be significantly reduced as compared with the conventional case.

[0060] Further, since the second screwing structure 32S is provided with a gas vent groove 321 that penetrates each thread in the pitch direction of the thread, by filling the heating furnace 3 with a carrier gas before heating the sample, the air inside the second electrode 32 can be discharged to the outside through the gas vent groove 321. Then, it is possible to prevent air from existing inside the second electrode 32 during heating of the sample, and there is no leakage of thermally expanded air from the second electrode 32 when the sample gas is generated as in the conventional case. That is, since there is no leakage of air containing nitrogen (N), which is an error factor, from the second electrode 32 when the sample gas is generated, the measurement accuracy of trace nitrogen (N) contained in the sample gas can be improved in the N2 detection unit 11.

[0061] Next, the mounting jig 200 used in the elemental analyzer according to the second embodiment of the present invention will be described with reference to FIGS. 5 and 6.

[0062] The mounting jig 200 of the second embodiment is used to attach the first electrode chip 31C to the first electrode body 31B of the elemental analyzer 100 described in the first embodiment. That is, the first electrode chip 31C formed as an axially symmetric component needs to be attached to the innermost part of the accommodation recess 311 of the first electrode body 31B, and since the first electrode chip 31C has a higher hardness than the first electrode body 31B, if the attachment is performed without the mounting jig 200, the first electrode chip 31C may shave the first electrode body 31B and be attached obliquely. In order to solve such a problem, it is necessary to rotate and screw the first electrode chip 31C in a state where the axial direction of the first electrode chip 31C coincides with the axial direction of the first electrode body 31B within the accommodation recess 311 of the first electrode body 31B.

[0063] Specifically, as shown in the cross-sectional view of FIG. 5 and the perspective view of FIG. 6, the mounting jig 200 includes a cylindrical guide 20A that fits into the housing recess 311, a cylindrical rod-shaped member attached so as to coincide with the axial direction of the guide 20A, a rotating shaft 20B provided rotatably with respect to the guide 20A, and an engaging member 20C provided to project radially at the tip of the rotating shaft 20B and engaging with the gas flow groove 317 of the first electrode chip 31C, having a substantially rectangular parallelepiped shape.

[0064] In the second embodiment, the guide 20A has an outer diameter dimension substantially the same as the maximum diameter portion of the housing recess 311. By fitting the guide 20A into the housing recess 311, the axial directions of the guide 20A and the rotating shaft 20B can be made substantially coincident with the axial direction of the housing recess 311 and the sample injection hole 313 of the first electrode body 31B. By rotating the rotating shaft 20B with respect to the guide 20A in such a state, the first electrode chip 31C with the gas outlet groove engaged with the engaging member 20C can be rotated while maintaining the correct posture and screwed into the first electrode body 31B.

[0065] Thus, according to the mounting jig 200 of the second embodiment, it becomes easy to directly attach the first electrode chip 31C to the innermost part of the housing recess 311, and the entire end face of the flange portion 315 of the first electrode chip 31C can be brought into complete contact with the edge of the crucible MP. Therefore, it is possible to prevent a situation where a sufficient current does not flow due to insufficient contact of the flange portion 315 with the crucible MP, and the sample cannot be heated as expected.

[0066] Other embodiments of the present invention will be described.

[0067] As shown in each of the diagrams in FIG. 7, the shape of the gas flow groove 317 formed in the first electrode chip 31C is not limited to that described in each embodiment. For example, one end of the gas flow groove 317 may be open only to the through hole 316, and the other end of the gas flow groove 317 may not be open on the outer circumferential surface of the flange portion 315. Also, the number of gas flow grooves 317 is not limited to four, and may be two or three.

[0068] A plurality of diameters of the through hole of the first electrode chip may be prepared. For example, when the shape of the sample to be introduced is rod-shaped or the like, the diameter may be changed to an appropriate value so as to prevent the sample from getting stuck between the sample introduction hole of the first electrode body and the crucible. That is, by simply replacing the first electrode chip, the diameter of the sample passage can be appropriately changed, so that it can be easily replaced according to the shape and properties of the sample. Also, the fixing structure for detachably fixing the first electrode chip to the first electrode body is not limited to the first screwing structure. The fixing structure may be, for example, an engaging structure including an engaging claw and an engaging groove formed between the first electrode chip and the first electrode body, or a fitting structure.

[0069] As shown in FIGS. 8(a), 8(b), and 9, as a modification of the cap 32D of the second electrode 32, the cap 32D may include a vent hole 325 that opens on the outer peripheral side of the exposure port 323 for exposing a part of the second electrode chip 32C on the top surface portion D1, a gas vent groove 321 that extends in the pitch direction of the screw and is formed so as to notch a part of the thread in the female screw portion S2, and a gas discharge groove 326 that extends in the radial direction at the lower end surface of the side surface portion D2 that is the edge of the cap 32D.

[0070] As shown in Fig. 8(b), the vent hole 325 is configured such that when the cap 32D is screwed onto the second electrode body 32B to fix the second electrode chip 32C, the inside and the outside of the second electrode 32 communicate with each other. That is, in this embodiment, the vent hole 325 is formed as a notch extending radially from the exposed port 323 and extends to the outside of the outermost periphery of the thin disk-shaped second electrode chip 32C fixed by the cap 32D. Further, four vent holes 325 are provided at 90° intervals so as to be axisymmetric with respect to the central axis of the second electrode 32.

[0071] As shown in Fig. 9, four gas vent grooves 321 and gas discharge grooves 326 are also provided at 90° intervals so as to be axisymmetric with respect to the central axis and are arranged to be substantially in phase with the vent hole 325. The vent hole 325 and the gas vent groove 321 are close to each other at their respective ends, and the gas vent groove 321 and the gas discharge groove 326 are formed as a continuous groove by making them orthogonal to each other.

[0072] By forming the vent hole 325 in the top surface D1 of the cap 32D in this way, it becomes easier to further release the air in the gaps between the threads of the second screw structure 32S from the top surface D1 side when the cap 32D is attached. Also, the gas discharge groove 326 makes it easier to release the air from between the edge of the cap 32D and the O-ring SL. Therefore, even if the gas vent groove 321 is deformed or dust accumulates due to the repeated analysis and the thermal influence on the second electrode 32, the gas release performance can be made less likely to deteriorate.

[0073] Next, yet another modification example of the cap 32D is shown in FIG. 10. Instead of forming the vent hole 325 as a notch, it may be formed as a through hole, for example. The position where the through hole is formed may be outside the second electrode chip 32C pressed by the cap 32D. Regarding the cap 32D shown in FIGS. 8 to 10, although the three of the vent hole 325, the gas vent groove 321, and the gas discharge groove 326 are arranged such that their respective positions are in phase, their respective positions may be shifted in the circumferential direction. Further, the cap 32D may be provided with at least one of the vent hole 325, the gas vent groove 321, and the gas discharge groove 326. For example, the cap 32D may be provided with either the vent hole 325 or the gas discharge groove 326, and the gas vent groove 321 may be formed only in the second electrode body 32B. In addition, the outer dimensions of the cap 32D itself may be reduced so that the gap between the outside of the side surface portion D2 and the inner surface of the first electrode 31 becomes a predetermined value or more, making it easier for air to be further discharged from the gas discharge groove 326.

[0074] As shown in FIG. 11, since a gas vent passage 32F that communicates the inside of the second screw structure 32S and the outside of the second electrode 32 is formed, when the cap 32C is attached to the second electrode body 32B, the air between the screw threads can be quickly discharged to the outside of the second electrode 32. Specifically, when the gas vent groove 321 is formed in the female screw portion S2 of the cap 32C, as shown in FIG. 11(a), the air present between the screw threads is discharged from the gas vent groove 321 through the vent hole 325 from above the cap 32C, and can also be discharged from below the cap 32C through the gas discharge groove 325.

[0075] Also, even when the gas vent groove 321 is formed not in the female screw portion S2 of the cap 32C but in the male screw portion S1 of the electrode body 32B as shown in FIG. 11(b), a similar gas vent passage 32F can be formed. Specifically, a ring-shaped recess 327 is formed near the base end of the male screw portion S1, and this ring-shaped recess 327 is formed so as to communicate with both the gas vent groove 321 and the gas discharge groove 325. That is, the ring-shaped recess 327 is formed by cutting the second electrode body 3B inward on the inner peripheral side to have a depth substantially the same as the height of the thread of the male screw portion S1, for example. Even when the gas vent groove 321 is formed in the male screw portion S1 in this way, it is possible to quickly discharge the air existing between the threads to the outside of the second electrode 32 through the vent hole 325 or the gas discharge groove 326 of the cap 32C.

[0076] The shapes of the second electrode chip and the cap are not limited to those shown in the respective embodiments. For example, in order to make it easier to adjust the position of the gas vent groove of the second screwing structure to an appropriate position, instead of a circular shape, a part of the notch may be formed as a mark indicating the mounting direction of the cap. Further, the gas vent groove formed in the second screwing structure of the second electrode may be formed not only in the male screw portion but also in the female screw portion. These gas vent grooves may be synchronized so that their circumferential positions substantially coincide in a state where the cap is completely screwed onto the second electrode body. That is, the gas vent grooves formed in both the male screw portion and the female screw portion may be aligned to increase the area through which air can pass. In addition, a gas vent groove may be formed only in the female screw portion.

[0077] The positional relationship and the moving direction of the first electrode and the second electrode are not limited to those shown in the respective embodiments. For example, the second electrode may move in the horizontal direction with respect to the fixed first electrode so that the crucible is accommodated in the accommodation recess.

[0078] In addition, as long as it does not contradict the gist of the present invention, various modifications of the embodiments and combinations of parts of the respective embodiments may be made.

Industrial Applicability

[0079] According to the present invention, it is possible to provide an elemental analyzer that can prevent components other than the sample gas from leaking from inside the second electrode during elemental analysis and causing an analysis error.

Claims

1. An elemental analyzer that sandwiches a crucible containing a sample between a first electrode and a second electrode and heats the sample by passing an electric current between the first electrode and the second electrode, wherein the second electrode comprises: a second electrode body having a substantially cylindrical tip portion; a second electrode chip provided on the tip surface of the second electrode body; a cap that sandwiches a part of the second electrode chip in a state where it is exposed to the outside between the cap and the second electrode body; a second screwing structure including a male screw portion and a female screw portion formed between the second electrode body and the cap; the second screwing structure further includes a gas vent groove formed to extend in the pitch direction and notch a part of the thread in at least one of the male screw portion or the female screw portion; a stepped portion is formed on the tip side of the second electrode body; an O-ring is provided in a ring-shaped groove formed by the stepped portion and the edge of the cap in a state where the cap is screwed to the second electrode body. An elemental analyzer.

2. The elemental analyzer according to claim 1, wherein a recess into which a part of the second electrode chip is fitted is formed on the tip surface of the second electrode body.

3. A gas vent passage communicating the inside of the second screwing structure and the outside of the second electrode is formed, The elemental analyzer according to any one of claims 1 or 2, wherein the gas vent groove forms at least a part of the gas vent passage.

4. The cap comprises: an exposure port for exposing the second electrode chip to the outside; a top surface portion provided around the exposure port and having a pressing plate that presses the second electrode chip against the tip surface of the second electrode body in a state where the cap is screwed to the second electrode body; The elemental analyzer according to any one of claims 1 to 3, further comprising a side surface portion having a substantially cylindrical shape and a female screw portion formed on the inner peripheral surface.

5. The elemental analyzer according to claim 4, wherein the cap further comprises one or more vent holes formed outside the exposure port on the top surface portion.

6. The elemental analyzer according to claim 4 or 5, wherein the cap further comprises a gas discharge groove extending from the inner peripheral side to the outer peripheral side on the side surface portion.

7. The elemental analyzer according to any one of claims 1 to 6, wherein the gas vent groove is formed in the female screw portion of the cap.

8. The elemental analyzer according to any one of claims 1 to 7, wherein the gas vent groove is formed in the male screw portion of the second electrode body.

9. It further includes a ring-shaped recess formed near the base end of the male screw portion of the second electrode body. The elemental analyzer according to claim 8, wherein the ring-shaped recess communicates with the gas vent groove formed in the male screw portion.

10. The first electrode includes a receiving recess in which the crucible is received. The elemental analyzer according to any one of claims 1 to 9, wherein the second electrode is configured to be movable between a first position where the crucible in the receiving recess is clamped between the second electrode and the first electrode, and a second position spaced a predetermined distance from the first position, where the crucible is disposed outside the receiving recess.

11. The elemental analyzer according to any one of claims 1 to 10, wherein the crucible is placed on the second electrode.

12. An elemental analyzer that sandwiches a crucible containing a sample between a first electrode and a second electrode and heats the sample by passing an electric current between the first electrode and the second electrode, wherein the second electrode includes a second electrode body having a generally cylindrical tip portion, a second electrode chip provided on the tip surface of the second electrode body, a cap that sandwiches a part of the second electrode chip in a state of being exposed to the outside between the cap and the second electrode body, and a second screwing structure including a male screw portion and a female screw portion formed between the second electrode body and the cap, wherein the second screwing structure further includes a gas vent groove formed to extend in the pitch direction and notch a part of the thread in at least one of the male screw portion or the female screw portion, wherein the cap includes an exposure port for exposing the second electrode chip to the outside, and a pressing plate provided around the exposure port for pressing the second electrode chip against the tip surface of the second electrode body in a state where the cap is screwed to the second electrode body, and a top surface portion, a side surface portion having a generally cylindrical shape and having the female screw portion formed on the inner circumferential surface, and one or more vent holes formed outside the exposure port on the top surface portion. An elemental analyzer.

Images