Elemental analysis device, mounting jig, and mounting method

Abstract

In order to provide an element analysis device capable of exchanging only a part of a worn electrode tip for an electrode having a housing recess in which a crucible is housed during elemental analysis, an element analysis device 100 sandwiches a crucible MP containing a sample between a first electrode 31 and a second electrode 32 and heats the sample by passing an electric current between the first electrode 31 and the second electrode 32, wherein the first electrode 31 includes a first electrode main body 31B in which an accommodation recess 311 for accommodating the crucible MP is formed, and a first electrode tip 31C detachably provided with respect to the first electrode main body 31B in the accommodation recess 311 such that a part of the first electrode tip 31C is exposed.

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 technology]

[0002] Elemental analyzers are used to quantify elements contained in a sample, such as nitrogen (N), hydrogen (H), and oxygen (O). In such elemental analyzers, a graphite crucible containing a sample is sandwiched between a pair of electrodes in a heating furnace, and a current is passed directly through the crucible to heat the crucible and the sample. The sample gas generated by heating is discharged from the heating furnace to the outside, and the concentration of each component is measured by an analysis mechanism consisting of an NDIR (Non Dispersive Infrared) gas analyzer, a TCD (Thermal Conductivity Detector), etc.

[0003] For example, the heating furnace of an elemental analysis apparatus shown in Patent Document 1 includes an upper electrode having an accommodating recess formed therein, and a lower electrode on which a crucible is placed. When the lower electrode rises, the crucible is accommodated in the accommodating recess while being sandwiched between the upper and lower electrodes.

[0004] Specifically, the upper electrode includes a generally cylindrical upper electrode body in which an accommodating recess is formed, and an upper electrode tip that is brazed and fixed to the upper electrode body within the accommodating recess.

[0005] For this reason, when elemental analysis is repeated and the upper electrode tip becomes worn, the entire upper electrode must be replaced, which requires a great deal of time and cost. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Publication US9808797 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an elemental analysis device that allows the replacement of only the worn electrode tip portion of an electrode having a recess in which a crucible is housed during elemental analysis. [Means for solving the problem]

[0008] The elemental analysis apparatus of the present invention is an elemental analysis apparatus that clamps 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, and is characterized in that the first electrode comprises a first electrode body having a accommodating recess in which the crucible is accommodated, a first electrode tip arranged so that a portion of the first electrode tip is exposed within the accommodating recess of the first electrode body, and a fixing structure arranged between the first electrode body and the first electrode tip for removably fixing the first electrode tip to the first electrode body.

[0009] In this case, since the first electrode tip is detachable from the first electrode body, when the first electrode tip is worn out, only this part can be replaced, which significantly reduces the effort and cost required for replacement compared to the conventional method of replacing the entire first electrode.

[0010] A specific embodiment for removably fixing the first electrode tip to the first electrode body includes a fixing structure that is a first screw structure consisting of a male thread portion and a female thread portion formed between the first electrode body and the first electrode tip.

[0011] In order to make the first electrode tip detachable from the first electrode body and to prevent sample gas generated from the sample from leaking to the outside between the first electrode tip and the first electrode body, the first electrode body may further have a sample insertion hole having one end opening into the accommodating recess and for inserting a sample into the crucible, and the first screw structure may be such that the first electrode comprises the male thread portion and the female thread portion formed between a portion of the sample insertion hole of the first electrode body and the first electrode tip.

[0012] In order to enable the sample gas generated from the sample in the crucible to be quickly discharged into the accommodating recess so that elemental analysis can be performed accurately in a short time, the first electrode tip must comprise: an insertion tube having the male thread portion formed on its outer peripheral surface and inserted into the sample insertion hole of the first electrode body; a flange portion that is exposed in the accommodating recess and extends radially at one end side of the insertion tube; a through hole formed to penetrate the insertion tube and the flange portion in the axial direction; and a gas discharge groove formed in the flange portion such that at least one end opens into the through hole and extends radially.

[0013] In order to enable a sufficient torque to be applied when screwing the first electrode tip into the first electrode body by engaging an instrument such as a mounting jig with the gas outlet groove, the other end of the gas outlet groove needs to be formed so as to open onto the outer peripheral surface of the flange portion.

[0014] In order to prevent bias in the flow of sample gas while making it easier to apply a uniform torque when attaching the first electrode tip, it is sufficient that multiple gas outlet grooves are formed and arranged axially symmetrically about the central axis of the first electrode tip.

[0015] If the gas outlet groove also serves as an engagement groove with which a jig is engaged when removing the first electrode tip from the first electrode body, the first electrode tip can be attached and detached to the back of the accommodation recess using a configuration required for elemental analysis, so there is no need to provide an element such as an engagement groove for engaging with a jig on the first electrode tip. Therefore, the first electrode tip can be made detachable from the first electrode body while preventing the flow of gas optimized for elemental analysis from being hindered by the element for attachment and detachment. Therefore, elemental analysis can be performed with the same accuracy as when the entire first electrode is formed as a single unit as in the past.

[0016] In order to clamp the crucible between the first electrode and the second electrode within the accommodating recess to heat the sample in a closed space and facilitate the discharge of all of the generated sample gas to the analytical device side, it is sufficient that the second electrode is configured to be movable between a first position where the crucible within the accommodating recess is clamped between the first electrode and the second electrode, and a second position a predetermined distance away from the first position where the crucible is positioned outside the accommodating recess.

[0017] In the elemental analysis apparatus of the present invention, by using an attachment jig for attaching the first electrode tip to the first electrode body, the attachment jig including a guide that fits into the accommodating recess, a rotating shaft that is rotatably arranged relative to the guide, and an engaging member that protrudes radially from the tip of the rotating shaft and engages with the gas outlet groove, it becomes easy to attach the first electrode tip in a straight position even when screwing it into the back side of the accommodating recess. Effect of the Invention

[0018] According to the present invention, since the first electrode tip is configured to be detachable from the accommodating recess of the first electrode body, when the first electrode tip is worn out, only this part can be replaced. Therefore, it is not necessary to replace the entire first electrode, and the effort and cost required for replacement can be significantly reduced compared to the conventional art. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing an elemental analysis apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 3 is a schematic cross-sectional view showing a state in which a crucible is sandwiched between a first electrode and a second electrode in the first embodiment. [Diagram 3] FIG. 2 is a schematic exploded perspective view of a first electrode according to the first embodiment, and a schematic view showing an end face of a flange portion. [Figure 4] FIG. 2 is a schematic exploded perspective view of a second electrode according to the first embodiment. [Diagram 5] FIG. 6 is a schematic cross-sectional view showing a state in which a mounting jig used in an elemental analyzer according to a second embodiment of the present invention is used. [Figure 6] FIG. 11 is a schematic perspective view showing a mounting jig according to a second embodiment. [Figure 7] FIG. 11 is a schematic diagram showing an example of a first electrode tip according to another embodiment of the present invention. [Figure 8] FIG. 13 is a schematic diagram showing the front side of a cap for a second electrode according to another embodiment of the present invention. [Figure 9] FIG. 13 is a schematic diagram showing the back side of a cap of a second electrode according to another embodiment. [Figure 10] FIG. 13 is a schematic diagram showing yet another embodiment of the cap for the second electrode. [Figure 11] FIG. 13 is a schematic diagram showing a gas venting flow path when a gas venting groove is formed in either the female thread portion or the male thread portion. [Explanation of symbols]

[0020] 100...Elemental analyzer 1...source 2...purifier 3...Heating furnace 31...1st electrode 31B...1st electrode body 311....Housing recess 312...Outflow hole 313: Sample insertion hole 31C First electrode tip 314 Insertion tube 315···Flange part 316...Through hole 317 Gas outlet groove 31S...First screw structure 32...Second electrode 32B...Second electrode body ST...Double section 322 ... Recess 32C Second electrode tip 32D···Cap 32S...Second screw structure 323...exposed mouth 324...Press plate 325...Ventilation hole 326 Gas exhaust groove 327 Ring-shaped recess 32F Gas vent passage 4. Dust filter 5. CO detection section 6. Oxidation reactor 7 CO 2 Detection Unit 8 H 2 O detection unit 9...Removal mechanism 10 Mass flow controller 11 N 2 Detection section (thermal conductivity analysis section) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] An elemental analyzer 100 according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows an outline of the elemental analyzer 100 according to the first embodiment.

[0022] The elemental analyzer 100 heats and melts, for example, a metal sample or a ceramic sample (hereinafter simply referred to as a sample) contained in a graphite crucible MP, and measures the amount of elements contained in the sample by analyzing the sample gas generated during the process. In the first embodiment, the elements to be measured are C (carbon), H (hydrogen), and N (nitrogen) contained in the sample.

[0023] As shown in Fig. 1, the elemental analysis apparatus 100 includes a heating furnace 3 in which a sample contained in a crucible MP is heated, an inlet flow path L1 that introduces a carrier gas into the heating furnace 3, and an outlet flow path L2 through which a mixed gas of the carrier gas and the sample gas is discharged from the heating furnace 3. More specifically, the elemental analysis apparatus 100 includes the heating furnace 3, each device provided in the inlet flow path L1 or the outlet flow path L2, and a control and calculation mechanism COM that controls each device and performs calculation processing of measured concentrations, etc. The control and calculation 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, and executes a program stored in the memory, and functions as a measurement value calculation unit C1 described later by cooperation of various devices. The control and calculation mechanism COM also includes, for example, a CO detection unit 5, a CO 2 Detection unit 7, H 2 O detector 8, N 2 It also functions as a display unit (not shown) that displays the concentrations of various elements contained in the sample based on the output of the detection unit 11.

[0024] Each part will be described in detail.

[0025] A gas cylinder, which is a carrier gas supply source 1, is connected to the base end of the inlet flow path L1. In the first embodiment, He (helium) is supplied from the supply source 1 into the inlet flow path L1. In addition, a purifier 2 is provided on the inlet flow path L1 to remove minute amounts of hydrocarbons contained in the carrier gas and increase the purity of the carrier gas.

[0026] The purifier 2 is formed of a material that physically adsorbs the hydrocarbons contained in the carrier gas, but does not substantially adsorb the carrier gas itself. The material forming the purifier 2 does not chemically react with the carrier gas or the hydrocarbons. That is, the purifier 2 is also used in, for example, a gas chromatograph, and the material forming the purifier 2 may be, for example, a zeolite molecular sieve. The material forming the purifier 2 may also be silica gel, activated carbon, ascarite, or the like. The purifier 2 can desorb the adsorbed molecules by, for example, heating, and regenerate its adsorption ability.

[0027] The heating furnace 3 is configured such that a graphite crucible MP containing a sample is sandwiched between a pair of electrodes, and a current is passed directly through the crucible MP to heat the crucible MP and the sample. When the sample is heated, the pressure of the carrier gas is adjusted by a pressure adjusting valve (not shown) provided upstream of the heating furnace 3 so that the pressure inside the heating furnace 3 is 60 kPa or less, more preferably 40 kPa or less. The electrodes of the heating furnace 3 will be described in detail later.

[0028] Next, each device provided on the outlet flow path L2 will be described.

[0029] On the outlet flow path L2, a dust filter 4, a CO detector 5, an oxidizer 6, and a CO 2 Detection unit 7, H 2 O detection unit 8, removal mechanism 9, mass flow controller 10, and N 2 The detection units 11 are arranged in this order from the upstream side.

[0030] The dust filter 4 filters out soot and other particles contained in the sample gas, thereby removing dust.

[0031] 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, and is composed of an NDIR (non-dispersive infrared gas analyzer). Due to its measurement accuracy, the CO detector 5 operates effectively when the oxygen contained inside the sample is at a high concentration. Specifically, it is preferable to measure CO of 150 ppm or more.

[0032] The oxidation unit 6 detects CO and CO contained in the mixed gas that has passed through the CO detection unit 5. 2 and oxidize H 2 H 2 In the first embodiment, copper oxide is used as the oxidizer 6, and its temperature is kept at 450° C. or less by a heating resistor provided around it.

[0033] CO 2 The detection unit 7 detects CO in the mixed gas that has passed through the oxidation unit 6. 2 This is an NDIR that detects and measures the concentration of CO. 2 From the viewpoint of measurement accuracy, the detection unit 7 operates effectively when the oxygen contained in the sample is at a low concentration (for example, less than 150 ppm).

[0034] H 2 The O detector 8 detects CO 2 H in the mixed gas that has passed through the detection unit 7 2 The NDIR detects O and measures its concentration. 2 The temperature of the mixed gas in the flow path up to the O detector 8 is kept at 100°C or higher. 2 O is kept in the form of water vapor. In this way, measurement errors caused by condensation are eliminated. 2 This is done to prevent this from occurring in the O detection unit 8.

[0035] The removal mechanism 9 is a mechanism for removing CO contained in the mixed gas. 2 and H 2 This removal mechanism 9 is made of an adsorbent, and for example, the same one as the purifier 2 provided in the introduction flow path L1 described above is used.

[0036] The mass flow controller 10 is a flow control device that integrates a flow sensor M1, a control valve M2, and a flow controller M3 in one package. 2 The detection unit 11 is supplied with the mixed gas that is kept constant at a set flow rate. Therefore, even if the pressure of the mixed gas changes due to the removal mechanism 9, the N 2 The pressure of the mixed gas in the detection unit 11 can be kept 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 so that the pressure inside the heating furnace 3 can be kept at 60 kPa, for example, even when the differential pressure before and after the mass flow controller 10 is 20 kPa.

[0037] N 2 The detection unit 11 is a thermal conductivity detector (TCD) that detects a change in the thermal conductivity of the mixed gas and a predetermined component, N, contained in the mixed gas from the flow rate of the mixed gas being supplied. 2 Measure the concentration of N 2 The mixed gas supplied to the detection unit 11 is mostly carrier gas and N 2 Since it is composed of only N 2 The concentration of N corresponds to the change in the measured thermal conductivity. 2 No flow meter is provided downstream of the detection unit 11. 2 The downstream side of the detection unit 11 is directly connected to the exhaust port of the outlet flow path L2.

[0038] The measurement signals indicating the concentration of each component obtained by each detection unit are input to the measurement calculation unit C1. The measurement 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, if the oxygen concentration inside the sample is equal to or higher than a predetermined threshold value (150 ppm), the measurement calculation unit C1 outputs the oxygen concentration obtained by the CO detection unit 5, and if the oxygen concentration is less than the threshold value, the measurement calculation unit C1 outputs the oxygen concentration obtained by the CO detection unit 5. 2 The oxygen concentration obtained by the detection unit 7 is used as an output value.

[0039] Finally, the pair of electrodes provided in the heating furnace 3 will be described in detail.

[0040] As shown in the cross-sectional view of Figure 2 and the oblique views of Figures 3 and 4, the heating furnace 3 is equipped with 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 a crucible MP is placed.

[0041] The first electrode 31 is an approximately two-stage cylindrical electrode with a thin cylindrical upper side and a flat disk lower side as shown in FIG. 3(a). The first electrode 31 includes a first electrode body 31B having a hollow cylindrical storage recess 311 formed in the lower center portion in which the crucible MP is stored as shown in the cross-sectional view of FIG. 2, and a first electrode tip 31C detachably provided in the storage recess 311 relative to the first electrode body 31B. The first electrode tip 31C is a part that directly contacts the upper edge of the approximately cylindrical crucible MP, and is consumed by repeating elemental analysis. The first electrode body 31B is made of, for example, copper, and the first electrode tip 31C is made of, for example, a copper alloy containing tungsten. That is, the first electrode tip 31C is made of a material having a higher hardness than the first electrode body 31B.

[0042] The first electrode body 31B forms the outer shape of the first electrode 31, and has a cylindrical storage recess 311 formed in the center of the flat disk-shaped portion so as to extend in the vertical direction as shown in the cross-sectional view of Fig. 2. A sample gas outlet hole 312 is formed in the side of the storage recess 311, extending in the horizontal direction so as to open. A sample insertion hole 313 for dropping a sample into the crucible MP is formed in the upper surface side of the storage recess 311. The sample insertion hole 313 is a roughly thin hollow cylindrical hole with a smaller diameter than the storage recess 311, and is formed so as to extend in the vertical direction along the central axis of the first electrode 31.

[0043] The first electrode tip 31C is roughly two-stage cylindrical, and includes a thin cylindrical insertion tube 314 inserted into the sample insertion hole 313 of the first electrode body 31B as shown in FIG. 2 and FIG. 3(a), and a flat flange portion 315 extending in the radial direction at the lower end side of the insertion tube 314. The first electrode tip 31C further includes a through hole 316 formed to penetrate the insertion tube 314 and the flange portion 315 in the axial direction, and a gas outlet groove 317 formed in the flange portion 315 so that at least one end opens on the side surface of the through hole 316 and extends in the radial direction. As shown in the lower end view of the first electrode tip 31C in FIG. 3(b), four gas outlet grooves 317 are provided at 90° intervals so as to be axially symmetrical with respect to the central axis. As shown in FIG. 2(b), the radially inner end of the gas outlet groove 317 opens to the inside of the crucible MP. In the first embodiment, the other end of the gas outlet groove 317 is open to the outer peripheral surface of the flange portion 315. That is, the sample gas generated by heating the sample in the crucible MP flows out of the crucible MP from inside the crucible MP through the gas outlet groove 317. The sample gas then flows out of the accommodating recess 311 through the outlet hole 312 formed in the first electrode body 31B into the outlet flow path L2.

[0044] Between the first electrode body 31B and the first electrode tip 31C, a fixing structure is provided for removably fixing the first electrode tip 31C to the first electrode body 31B. More specifically, between the outer peripheral surface of the insertion tube 314 of the first electrode tip 31C and the inner peripheral surface of the sample insertion hole 313 of the first electrode body 31B, a first screw structure 31S consisting of a male screw portion S1 and a female screw portion S2 is formed as a fixing structure. The first screw structure 31S allows the first electrode tip 31C to be removably attached to the first electrode body 31B. In addition, there is no groove cut in the pitch direction in the thread of the first screw structure 31S. Therefore, when the first screw structure 31S is completely screwed, the flange portion 315 and the upper wall surface of the accommodation recess 311 are in close contact with each other, and the male screw portion S1 and the female screw portion S2 are in close contact with each other without any gaps. Therefore, the sample gas flowing out from the crucible MP can be prevented from being accumulated in the gap between the first electrode body 31B and the first electrode tip 31C and from flowing back.

[0045] Next, the second electrode 32 will be described with reference to FIGS.

[0046] The second electrode 32 is configured to be movable up and down, for example, by an air cylinder (not shown), and a part of it is inserted into the accommodating recess 311 together with the crucible MP placed on it. Specifically, the second electrode 32 is configured to be movable between a first position where the crucible in the accommodating recess 311 is sandwiched between the second electrode 32 and the first electrode 31, and a second position that is a predetermined distance away from the first position and where the crucible is disposed outside the accommodating recess 311.

[0047] The second electrode 32 includes a second electrode body 32B having a generally stepped cylindrical shape, a second electrode tip 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 tip 32C to the second electrode body 32B and has an exposure port formed therein for exposing the contact surface of the second electrode tip 32C with the crucible MP to the outside. The second electrode body 32B and the cap 32D are made of copper, and the second electrode tip 32C is made of a copper alloy containing tungsten.

[0048] In this way, the second electrode 32 is composed of three separate parts, and only the second electrode tip 32C is configured to be replaceable. More specifically, a second screw structure 32S consisting of a male screw portion S1 and a female screw portion S2 is formed between the outer peripheral surface of the tip portion of the second electrode body 32B and the inner peripheral surface of the cap 32D.

[0049] The second screw structure 32S is different in structure from the first screw structure 31S formed on the first electrode 31. That is, as shown in FIG. 4, the male screw portion S1 of the second screw structure 32S is formed so as to extend in the pitch direction of the screw and to cut out a part of the thread. The gas vent groove 321 is configured to cut out the thread to the height of the bottom of the thread, for example, but may be formed shallower. In addition, four gas vent grooves 321 are provided at 90° intervals so as to be axially symmetrical with respect to the central axis of the second electrode 32. The number of gas vent grooves 321 is not limited to four, and may be less or more. In addition, they do not necessarily have to be arranged axially symmetrical.

[0050] Because this gas vent groove 321 is formed, even if air in the gaps between the threads of the second screw-engagement structure 32S becomes trapped between the threads when the cap 32D is attached, the air in the second electrode 32 can be discharged to the outside of the second electrode 32 through the gas vent groove 321, for example, when replacing the air present in the heating furnace 3 with carrier gas.

[0051] The second electrode body 32B has a recess 322 formed on its tip surface so that the back side of the second electrode tip 32C can be fitted into it, and a step ST that faces 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 so that the tip surface where the second electrode tip 32C is attached has the smallest diameter, and the step ST expands to an outer diameter approximately the same as the outer diameter of the O-ring SL to be attached.

[0052] Specifically, the second electrode tip 32C can be aligned with respect to the second electrode body 32B by previously fitting the second electrode tip 32C into the recess 322. Furthermore, with the position of the second electrode tip 32C determined, the cap 32D is screwed onto the second electrode body 32B, whereby the second electrode tip 32C can be fixed while being maintained in the correct position.

[0053] In addition, an O-ring SL is placed in the ring-shaped groove RT formed between the step ST of the second electrode body 32B and the 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. In addition, the ring-shaped groove RT is formed slightly larger than the thickness dimension of the O-ring SL. In the process of inserting the second electrode 32 into the receiving recess 311 of the first electrode body 31B to clamp the crucible MP between the electrodes and pass a current, the O-ring SL slides toward the edge of the cap 32D and abuts against it to form a seal in the receiving recess 311. Because of this configuration, it is not necessary to attach the O-ring SL in a state where the inner diameter is greatly enlarged as in the conventional case, and the installation work of the O-ring SL can be simplified.

[0054] The cap 32D has a top surface D1 and a side surface D2. The top surface D1 has an exposure opening 323 that exposes the second electrode tip 32C to the outside, and a pressing plate 324 that is provided around the exposure opening 323 and presses the second electrode tip 32C against the tip surface of the second electrode body 32B when the cap 32D is screwed into the second electrode body 32B. The side surface D2 has a female screw portion S1 formed on the inner peripheral surface. In addition, a gap is formed between the end surface of the side surface D2 and the second electrode body 32B, so that air that passes through the gas vent groove 321 from the lower edge of the cap 32D is not prevented from being discharged to the outside of the second electrode 32 even when the cap 32D is completely screwed into the second electrode body 32B.

[0055] In the elemental analysis device 100 thus configured, the first electrode tip 31C is configured to be detachable from the first electrode body 31B by the first screw structure 31S, so that when the first electrode tip 31C is worn down due to repeated elemental analysis, only the first electrode tip 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 conventional case.

[0056] Furthermore, since the second electrode tip 32C is configured to be detachable by the second screw structure 32S formed between the second electrode body 32B and the cap 32D, when the second electrode tip 32C is worn out, only this portion can be replaced.

[0057] For these reasons, the effort and cost required for replacing consumables required to continue elemental analysis in the heating furnace 3 can be significantly reduced compared to the conventional method.

[0058] In addition, since the second screw structure 32S has gas vent grooves 321 penetrating each thread in the pitch direction, the heating furnace 3 is filled with carrier gas before the sample is heated, and the air in the second electrode 32 can be discharged to the outside through the gas vent grooves 321. When the sample is heated, air can be prevented from being present in the second electrode 32, and air that has expanded due to heat does not leak from the second electrode 32 when the sample gas is generated, as in the conventional method. In other words, when the sample gas is generated, there is no leakage of air containing nitrogen (N), which is a cause of error, from the second electrode 32, and the measurement accuracy of the trace amount of nitrogen (N) contained in the sample gas in the N2 detection unit 11 can be improved.

[0059] Next, a mounting jig 200 used in an elemental analyzer according to a second embodiment of the present invention will be described with reference to FIGS.

[0060] The mounting jig 200 of the second embodiment is used to mount the first electrode tip 31C to the first electrode body 31B of the elemental analysis device 100 described in the first embodiment. That is, the first electrode tip 31C formed as an axisymmetric part needs to be mounted at the deepest part of the accommodation recess 311 of the first electrode body 31B, and since the first electrode tip 31C is harder than the first electrode body 31B, if the first electrode tip 31C is mounted without the mounting jig 200, there is a possibility that the first electrode tip 31C will be mounted at an angle by scraping the first electrode body 31B. To solve such a problem, the first electrode tip 31C needs to be rotated and screwed in the accommodation recess 311 of the first electrode body 31B while the axial direction of the first electrode tip 31C is aligned with the axial direction of the first electrode body 31B.

[0061] Specifically, as shown in the cross-sectional view of FIG. 5 and the oblique view of FIG. 6, the mounting jig 200 includes a cylindrical guide 20A that fits into the accommodating recess 311, a rotating shaft 20B that is a cylindrical rod-shaped member attached so as to coincide with the axial direction of the guide 20A and is rotatably arranged relative to the guide 20A, and an engaging member 20C that is roughly rectangular and protrudes radially from the tip of the rotating shaft 20B and engages with the gas discharge groove 317 of the first electrode tip 31C.

[0062] In the second embodiment, the guide 20A has an outer diameter dimension substantially equal to the maximum diameter portion of the accommodating recess 311, and by fitting this guide 20A into the accommodating recess 311, the axial directions of the guide 20A and the rotating shaft 20B can be made to substantially coincide with the axial directions of the accommodating recess 311 and the sample insertion hole 313 of the first electrode body 31B. By rotating the rotating shaft 20B relative to the guide 20A in this state, the first electrode tip 31C, whose gas leading groove 317 is engaged with the engaging member 20C, can be rotated while maintaining the correct posture and screwed into the first electrode body 31B.

[0063] Thus, according to the mounting jig 200 of the second embodiment, it becomes easy to mount the first electrode tip 31C straight to the innermost part of the accommodating recess 311, and the entire end face of the flange portion 315 of the first electrode tip 31C can be brought into complete contact with the edge of the crucible MP. This prevents the flange portion 315 from making sufficient contact with the crucible MP, resulting in insufficient current flow and the inability to heat the sample as expected.

[0064] Other embodiments of the present invention will now be described.

[0065] 7, the shape of the gas leading groove 317 formed in the first electrode tip 31C is not limited to those described in the respective embodiments. For example, one end of the gas leading groove 317 may be open only to the through hole 316, and the other end of the gas leading groove 317 may not be open to the outer peripheral surface of the flange portion 315. In addition, the number of the gas leading grooves 317 is not limited to four, and may be two or three.

[0066] The diameter of the through hole of the first electrode tip may be prepared in a plurality of types. For example, when the shape of the sample to be inserted is rod-shaped, the diameter may be changed to an appropriate diameter to prevent the sample from getting stuck between the sample insertion hole of the first electrode body and the crucible. That is, the diameter of the path of the sample can be changed appropriately by simply replacing the first electrode tip, so that the first electrode tip can be easily replaced with one that corresponds to the shape and properties of the sample. In addition, the fixing structure that detachably fixes the first electrode tip to the first electrode body is not limited to the first screw structure. The fixing structure may be, for example, an engagement structure consisting of an engagement claw and an engagement groove formed between the first electrode tip and the first electrode body, or a fitting structure.

[0067] As shown in each of Figures 8(a), 8(b) and 9, as a modified example of the cap 32D of the second electrode 32, the cap 32D may be provided with an air vent 325 that opens outwardly of an exposure opening 323 in the top surface portion D1 for exposing a portion of the second electrode tip 32C to the outside, a gas vent groove 321 that extends in the pitch direction of the screw and is formed by cutting out a portion of the thread in the female screw portion S2, and a gas exhaust groove 326 that extends radially on the lower end face of the side portion D2, which is the edge of the cap 32D.

[0068] 8(b), the vent hole 325 is configured to communicate between the inside and the outside of the second electrode 32 when the cap 32D is screwed onto the second electrode body 32B and the second electrode tip 32C is fixed. That is, in this embodiment, the vent hole 325 is formed as a notch extending in the radial direction from the exposed opening 323, and extends beyond the outermost periphery of the thin disk-shaped second electrode tip 32C fixed by the cap 32D. Four vent holes 325 are provided at 90° intervals so as to be axially symmetrical with respect to the central axis of the second electrode 32.

[0069] 9, gas vent grooves 321 and gas exhaust grooves 326 are also provided in four, each at an angle of 90°, so as to be symmetrical about the central axis, and are arranged so as to be approximately in phase with ventilation holes 325. Ventilation holes 325 and gas vent grooves 321 are adjacent to each other at their respective ends, and gas vent grooves 321 and gas exhaust grooves 326 are formed as continuous grooves that are perpendicular to each other.

[0070] By forming the ventilation hole 325 in the top surface D1 of the cap 32D in this manner, it becomes possible to make it easier for air in the gaps between the threads of the second screw structure 32S to escape from the top surface D1 side when the cap 32D is attached. In addition, the gas exhaust groove 326 makes it easier for air to escape from between the edge of the cap 32D and the O-ring SL. Therefore, even if the gas release groove 321 is deformed or dust accumulates due to the thermal effect on the second electrode 32 as a result of repeated analysis, the gas release performance is unlikely to deteriorate.

[0071] Next, another modified example of the cap 32D is shown in FIG. 10. The vent 325 may be formed as a through hole, for example, instead of being formed as a notch. The through hole may be formed at a position outside the second electrode tip 32C pressed by the cap 32D. In the cap 32D shown in FIGS. 8 to 10, the vent 325, the gas vent groove 321, and the gas exhaust groove 326 are arranged so that their positions are in phase, but their positions may be shifted in the circumferential direction. The cap 32D may also include at least one of the vent 325, the gas vent groove 321, and the gas exhaust groove 326. For example, the cap 32D may include either the vent 325 or the gas exhaust 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 portion D2 and the inner surface of the first electrode 31 is greater than or equal to a predetermined value, thereby making it easier for air to be discharged from the gas discharge groove 326.

[0072] 11, gas vent flow path 32F is formed to communicate between the inside of second screw structure 32S and the outside of second electrode 32, so that when cap 32C is attached to second electrode body 32B, air present between the threads can be quickly discharged to the outside of second electrode 32. Specifically, when gas vent groove 321 is formed in female screw portion S2 of cap 32C, air present between the threads can be discharged from gas vent groove 321 through vent hole 325 to the upper side of cap 32C, and can also be discharged from the lower side of cap 32C through gas discharge groove 325, as shown in FIG.

[0073] 11(b), a similar gas release flow passage 32F can be formed even when the gas release groove 321 is formed in the male thread portion S1 of the electrode body 32B, not in the female thread portion S2 of the cap 32C. Specifically, a ring-shaped recess 327 is formed near the base end of the male thread portion S1, and this ring-shaped recess 327 is formed so as to communicate with both the gas release groove 321 and the gas discharge groove 325. That is, the ring-shaped recess 327 is formed by cutting the second electrode body 3B toward the inner periphery to have a depth approximately equal to the height of the thread of the male thread portion S1. Even when the gas release groove 321 is formed in the male thread portion S1 in this way, it is possible to quickly discharge air present between the threads to the outside of the second electrode 32 through the ventilation hole 325 or the gas discharge groove 326 of the cap 32C.

[0074] The shapes of the second electrode tip and the cap are not limited to those shown in each embodiment. For example, in order to easily adjust the position of the gas vent groove of the second screw structure to the appropriate position, a partially cutout portion may be formed instead of a circular shape as a mark indicating the mounting direction of the cap. In addition, the gas vent groove formed in the second screw structure of the second electrode may be formed not only in the male screw portion but also in the female screw portion. These gas vents may be synchronized so that the circumferential positions are approximately the same when the cap is completely screwed onto the second electrode body. In other words, 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, the gas vent groove may be formed only in the female screw portion.

[0075] The positional relationship between the first and second electrodes and the direction of movement are not limited to those shown in each embodiment. For example, the second electrode may move horizontally relative to the fixed first electrode so that the crucible is accommodated in the accommodation recess.

[0076] In addition, various modifications of the embodiments and combinations of parts of each embodiment may be made without departing from the spirit of the present invention. [Industrial Applicability]

[0077] According to the present invention, it is possible to provide an elemental analyzer that does not require replacement of the entire first electrode, and that can significantly reduce the effort and cost involved in replacement compared to conventional techniques.

Claims

1. An elemental analysis apparatus that holds a crucible containing a sample between a first electrode and a second electrode, and heats the sample by passing a current between the first electrode and the second electrode, The first electrode is a first electrode body having a recess for receiving the crucible; a first electrode tip provided so as to be partially exposed within the accommodating recess of the first electrode body; a fixing structure provided between the first electrode body and the first electrode tip, for detachably fixing the first electrode tip to the first electrode body; the fixing structure is a first screw structure including a male screw portion and a female screw portion formed between the first electrode body and the first electrode tip, the first electrode body further includes a sample insertion hole having one end opening into the accommodation recess and for inserting a sample into the crucible; an electrode tip provided on the first electrode body and connected to the second electrode body via a second thread;

2. The first electrode tip is an insertion tube having the male screw portion formed on an outer peripheral surface thereof and being inserted into the sample insertion hole of the first electrode body; a flange portion that is exposed in the accommodating recess and extends in a radial direction at one end side of the insertion tube; a through hole formed so as to pass through the insertion tube and the flange portion in the axial direction; 2. The elemental analyzer according to claim 1, further comprising a gas outlet groove formed in said flange portion, said gas outlet groove having at least one end open in said through hole and extending in a radial direction.

3. 3. An elemental analyzer according to claim 2, wherein the other end of said gas outlet groove is formed so as to open onto the outer peripheral surface of said flange portion.

4. 4. The elemental analyzer according to claim 2, wherein a plurality of the gas outlet grooves are formed and are arranged symmetrically with respect to a central axis of the first electrode tip.

5. 5. The elemental analyzer according to claim 2, wherein the gas outlet groove also serves as an engagement groove with which a jig is engaged when removing the first electrode tip from the first electrode body.

6. 6. An elemental analysis apparatus as described in any one of claims 1 to 5, wherein the second electrode is configured to be movable between a first position in which the second electrode clamps the crucible located in the accommodating recess between itself and the first electrode, and a second position spaced a predetermined distance from the first position in which the crucible is positioned outside the accommodating recess.

7. 4. The elemental analyzer according to claim 2, further comprising a mounting jig for mounting the first electrode tip to the first electrode body, the mounting jig comprising: A guide that is fitted into the receiving recess; A rotation shaft provided rotatably relative to the guide; an engaging member that is provided at the tip of the rotating shaft and protrudes in the radial direction, and that engages with the gas leading groove.

8. A method for attaching the first electrode tip to the first electrode body using the attachment jig according to claim 7.

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