Elemental analysis device and filter unit

Abstract

In order to enable a dust filter to be replaced appropriately, irrespective of the skill level of a user, provided is a filter unit which is provided on a lead-out flow path through which a mixed gas composed of a carrier gas and a sample gas is led out from a heating furnace, the filter unit comprising: a filter element that collects dust in the mixed gas; an upstream-side holder and a downstream-side holder that face each other with the filter element interposed therebetween; and a fixing mechanism that fixes the filter element in a state where the upstream-side holder and the downstream-side holder hold the filter element therebetween. The fixing mechanism has an engaged part provided to either the upstream-side holder or the downstream-side holder, and a hook part that is provided to the other of the upstream-side holder and the downstream-side holder and that engages with the engaged part. The fixing mechanism fixes the upstream-side holder and the downstream-side holder by causing the hook part to engage with the engaged part.

Description

Elemental Analyzer, Filter Unit

[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, and a filter unit used in the elemental analyzer.

[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 the 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 mixed gas composed of the sample gas and the carrier gas generated by heating is passed through a dust filter to filter dust such as soot. The concentrations of various components contained in the mixed gas after filtration are measured by an analysis mechanism composed of an NDIR (Non Dispersive Infrared) or a TCD (Thermal Conductivity Detector).

[0003] When such a dust filter collects dust such as soot exceeding a predetermined amount, it affects the measurement accuracy of the analysis mechanism. Therefore, in the elemental analyzer disclosed in Patent Document 1, the dust filter is configured to be replaceable.

[0004] Specifically, the dust filter of Patent Document 1 is held sandwiched between a pair of screwed holders. By removing this screw, the dust filter is replaced, and by tightening the screw again, the elemental analyzer returns to a state where analysis is possible.

[0005] Japanese Patent Application Laid-Open No. 2022-505879

[0006] When such a dust filter is replaced manually, if the user's proficiency is low, the screw fastening of the holder sandwiching the dust filter may become loose, and there is a risk of gas leakage. In addition, there is a risk that the dust filter may be displaced from the predetermined position, and dust filtration may not be properly performed.

[0007] Therefore, the present invention was made to solve the above-mentioned problems, and aims to provide an elemental analyzer that can properly replace the dust filter regardless of the user's skill level.

[0008] In other words, the elemental analysis apparatus according to the present invention comprises a heating furnace for heating a sample to generate a sample gas, an introduction channel for introducing a carrier gas into the heating furnace, an outlet channel from which a mixed gas consisting of the carrier gas and the sample gas is discharged from the heating furnace, a filter unit provided on the outlet channel for filtering the mixed gas flowing through the outlet channel, and an analyzer provided downstream of the filter unit on the outlet channel for analyzing the components contained in the mixed gas, wherein the filter unit is used to analyze the components contained in the mixed gas The device comprises a filter element for collecting dust, an upstream holder and a downstream holder facing each other with the filter element in between, and a fixing mechanism for fixing the filter element while the upstream holder and the downstream holder are holding it. The fixing mechanism has a locking portion provided on one of the upstream holder and the downstream holder, and a hook portion provided on the other of the upstream holder and the downstream holder that locks onto the locking portion. The upstream holder and the downstream holder are fixed by locking the hook portion onto the locking portion.

[0009] With the present invention configured in this way, the hook portion can be engaged with the locked portion, allowing the upstream holder and the downstream holder to clamp the filter element with a constant mechanical force. This reduces the influence of user skill level compared to clamping the filter element with screws, enabling proper filter replacement.

[0010] The filter element is preferably in the form of a sheet. This configuration makes it easier to replace than filters made of quartz wool or similar materials.

[0011] It is desirable that the filter element is held horizontally within the filter unit. With this configuration, since the sheet-like filter element is held horizontally, displacement of the filter element due to gravity can be prevented.

[0012] Preferably, the filter unit is provided interposed between the upstream holder and the downstream holder and the filter element, and further has a clamping portion that clamps the peripheral edge of the filter element from the thickness direction, and the clamping portion is fixed by being clamped between the upstream holder and the downstream holder by engaging the hook with the locked portion, and the clamping portion is removed from the upstream holder and the downstream holder together with the filter element by releasing the hook from the locked portion. With this configuration, the filter element can be attached to and detached from the filter unit while being clamped by the clamping portion, so that the filter element does not shift during replacement and the handling of the filter unit can be improved.

[0013] Preferably, the clamping portion includes a pair of clamping plates for clamping the filter element and a fixing device for fixing the pair of clamping plates together while the filter element is clamped. With this configuration, the filter element can be clamped and fixed to the clamping portion taken out from the upstream holder and the downstream holder, and then the clamping portion can be set back into the holders to replace the filter element. This allows the attachment of the filter element to the clamping portion to be done in advance in a spacious workspace, and as a result, the filter can be prevented from shifting or curling.

[0014] Preferably, a guide groove is formed on one of the opposing surfaces of the upstream and downstream holders, extending from a predetermined fixing position for securing the clamping portion to the outer surface, and the clamping portion has a protrusion that fits into the guide groove and moves within the guide groove. With this configuration, the clamping portion can be slid along the guide groove to be set in the fixing position, and replacement work, including positioning the clamping portion, can be easily performed.

[0015] The upstream holder and the downstream holder have internal passages that communicate with the discharge passage, and the clamping portion has an inlet for introducing gas into the filter element and an outlet for discharging gas from the filter element. When the upstream holder and the downstream holder clamp the clamping portion, the internal passage of the upstream holder communicates with the inlet, and the internal passage of the downstream holder communicates with the outlet, forming a series of passages. Preferably, the filter unit further includes an upstream seal portion provided between the upstream holder and the clamping portion so as to surround the inlet, and a downstream seal portion provided between the downstream holder and the clamping portion so as to surround the outlet. With this configuration, the force with which the upstream holder and the downstream holder clamp the clamping portion presses the seal portion between each holder and the clamping portion, thereby providing a seal and suppressing leakage.

[0016] The filter unit preferably has a sliding mechanism that slides the other of the upstream or downstream holder along their clamping direction relative to one of the upstream or downstream holders. With this configuration, the other holder sliding along the clamping direction can evenly press the clamped portion between the two holders, thereby suppressing leakage.

[0017] Preferably, the filter unit further includes an elastic member that applies force to the upstream holder or the downstream holder in a direction that causes the upstream holder and the downstream holder to move away from each other. With this configuration, when the hook portion is released from the locking portion, the distance between the upstream holder and the downstream holder automatically increases, securing the space necessary for replacing the filter element and facilitating the replacement of the filter element.

[0018] Preferably, the system further includes a determination mechanism for determining the recommended replacement time for the filter element, the determination mechanism comprising a detection unit that calculates and outputs the electrical resistance of the filter element, and a determination unit that compares the electrical resistance with a predetermined threshold to determine whether or not the filter element is due for replacement. With this configuration, the appropriate replacement time for the filter element can be determined based on the electrical resistance value corresponding to the amount of dust collected by the filter element. This allows for a better balance between reducing operating costs and ensuring measurement accuracy compared to conventional methods of determining replacement time based on the number of uses or usage period.

[0019] Furthermore, the filter unit according to the present invention is a filter unit provided in an outlet channel through which gas is discharged from a heating furnace that heats a sample to generate a sample gas, and comprises a filter element for collecting dust in the gas, an upstream holder and a downstream holder facing each other with the filter element in between, and a fixing mechanism for fixing the filter element with the upstream holder and the downstream holder in a clamped state, wherein the fixing mechanism comprises a locking portion provided on one of the upstream holder and the downstream holder, and a hook portion provided on the other of the upstream holder and the downstream holder that locks onto the locking portion, and the upstream holder and the downstream holder are fixed by locking the hook portion onto the locking portion.

[0020] Thus, with the elemental analyzer according to the present invention, it becomes possible to replace filters appropriately regardless of the user's skill level.

[0021] This is a schematic diagram showing the overall configuration of an elemental analyzer in one embodiment of the present invention. (a) is a front view, (b) is a side view, and (c) is a top view schematically showing the structure of the filter unit in the same embodiment. This is a schematic cross-sectional view taken along line A-A showing the structure of the filter unit in the same embodiment. This is a schematic exploded perspective view showing the structure of the filter unit in the same embodiment. This is a schematic cross-sectional view showing the filter unit in the released state in the same embodiment. This is a schematic cross-sectional view showing the filter element removed from the filter unit in the same embodiment.

[0022] An embodiment of the elemental analyzer 100 according to the present invention will be described below with reference to the drawings. Note that all the following figures are schematic representations, with some details omitted or exaggerated for clarity. The same components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0023] <Basic Configuration of Elemental Analyzer> As shown in Figure 1, the elemental analyzer 100 of this embodiment heats and melts, for example, a metal sample or a ceramic sample (hereinafter simply referred to as "sample") contained in a graphite crucible MP, and measures the amount of elements contained in the sample by analyzing the sample gas generated at that time. For example, all or part of the O (oxygen), H (hydrogen), and N (nitrogen) contained in the sample are to be measured.

[0024] Specifically, as shown in Figure 1, the elemental analyzer 100 includes a heating furnace 1 for heating a sample to generate a sample gas, an introduction channel L1 for introducing a carrier gas into the heating furnace 1, an outlet channel L2 from which a mixed gas consisting of the carrier gas and the sample gas is discharged from the heating furnace 1, a filter unit 2 provided on the outlet channel L2 for filtering the mixed gas flowing through the outlet channel L2, and an analyzer 3 for analyzing the components contained in the mixed gas filtered by the filter unit 2.

[0025] A gas cylinder, which is the carrier gas supply source S, is connected to the base end of the introduction channel L1. In this embodiment, He (helium) is supplied into the introduction channel L1 from the supply source S. A purifier (not shown) is also provided on the introduction channel L1 to remove trace amounts of hydrocarbons contained in the carrier gas and increase the purity of the carrier gas.

[0026] The heating furnace 1 is configured to hold a graphite crucible MP containing the sample between a pair of electrodes, a first electrode and a second electrode, and to heat the crucible MP and the sample by passing an electric current directly through the crucible MP. The sample gas generated by heating the sample is mixed with a carrier gas supplied into the heating furnace 1 from the introduction channel L1 and supplied into the outlet channel L2 connected to the heating furnace 1.

[0027] On the outlet channel L2, there is a filter unit 2 into which the mixed gas discharged from the heating furnace 1 flows, and an analyzer 3 that detects and analyzes one or more predetermined components in the mixed gas that has passed through the filter unit 2. The specific configuration of the filter unit 2 will be described later.

[0028] The analyzer 3 consists of a detection device installed in the outlet channel L2 and a control device (not shown) that performs calculations to determine the concentration of the components detected by the detector. The control device is a so-called computer equipped with, for example, a CPU, memory, A / D converter, D / A converter, various input / output means, etc., and performs functions such as calculating concentrations according to the program stored in the memory.

[0029] <Specific Configuration of the Filter Unit> The filter unit 2 filters out dust such as soot contained in the mixed gas flowing through the outlet channel L2, thereby removing dust. Furthermore, the filter unit 2 in this embodiment is configured to allow replacement of filter elements whose function has deteriorated due to dust accumulation.

[0030] The structure of the filter unit 2 of this embodiment will be described below with reference to Figures 2 to 6. Figure 3 is a cross-sectional view of the filter unit 2 along the line A-A in Figure 2(c).

[0031] Specifically, as shown in Figures 2 to 6, the filter unit 2 includes a filter element 21 for collecting dust in the mixed gas, an upstream holder 22 and a downstream holder 23 for holding the filter element 21, and a fixing mechanism 24 for fixing the filter element 21 while the upstream holder 22 and the downstream holder 23 are clamping it.

[0032] Figures 2 and 3 show the filter unit 2 with the holders 22 and 23 fixed by the fixing mechanism 24. Figure 5 shows the filter unit 2 with the fixing mechanism 24 releasing the holders 22 and 23. Figure 6 shows the filter element 21 removed from the released filter unit 2 along with the clamping part 25, which will be described later.

[0033] Here, the direction in which the upstream holder 22 and the downstream holder 23 clamp the filter element 21 (the clamping direction) is referred to as the clamping direction. The filter unit 2 in this embodiment is configured such that its clamping direction is vertical. The upstream side refers to the upstream side in the flow direction of the mixed gas supplied from the heating furnace 1, and the downstream side refers to the opposite side.

[0034] As shown in Figures 2 to 6, the filter unit 2 of this embodiment further includes a clamping portion 25 interposed between the upstream holder 22 and the downstream holder 23 and the filter element 21 to clamp the filter element 21, a sealing portion 26 provided between the clamping portion 25 and the upstream holder 22 and the downstream holder 23, a sliding mechanism 27 that slides the downstream holder 23 relative to the upstream holder 22, and an elastic member 28 that applies force in a direction that causes the upstream holder 22 and the downstream holder 23 to move away from each other.

[0035] The following describes in detail each component of the filter unit 2.

[0036] As shown in Figure 3, the filter element 21 is in the shape of a circular sheet. In this embodiment, the filter element 21 consists of a PTFE membrane filter 211 and a metal mesh filter 212 stacked on top of each other. The membrane filter 211 is a dust removal filter that collects dust contained in the mixed gas. The metal mesh filter 212 is provided downstream of the membrane filter 211 and is a support filter that supports the membrane filter 211 and prevents it from tearing or breaking.

[0037] The filter element 21 is held horizontally within the filter unit 2. More specifically, the flat surface of the sheet-like filter element 21 is held so as to be aligned horizontally.

[0038] As shown in Figures 2 to 6, the upstream holder 22 and the downstream holder 23 are a pair of block bodies facing each other with the filter element 21 in between. In this embodiment, the upstream holder 22 and the downstream holder 23 each have a roughly rectangular parallelepiped shape and face each other vertically in the vertical direction with the filter element 21 in between. Here, the upstream holder 22 is positioned on the lower side and the downstream holder 23 is positioned on the upper side.

[0039] The upstream holder 22 has an upstream internal channel 22x that communicates with the outlet channel L2. One opening of the upstream internal channel 22x is formed on the side wall surface of the upstream holder 22, and the other opening is formed on the upper surface of the upstream holder 22, that is, on the surface 22a facing the downstream holder 23.

[0040] The other opening of the upstream internal flow path 22x is formed in a recess 221 formed on the opposing surface 22a. Furthermore, a guide groove 222 is formed on the opposing surface 22a of the upstream holder 22, extending from the recess 221 to the outer surface of the upstream holder 22. This guide groove 222 is formed to be shallower than the recess 221.

[0041] The downstream holder 23 has a downstream internal channel 23y that communicates with the outlet channel L2. One opening of the downstream internal channel 23y is formed on the bottom surface of the downstream holder 23, that is, on the surface 23a facing the upstream holder 22, and the other opening is formed on the side wall surface of the downstream holder 23.

[0042] The fixing mechanism 24 is a so-called snap lock, and as shown in Figures 2 to 6, it has a locking portion 241 attached to the side of the downstream holder 23 and a hook portion 242 attached to the side of the upstream holder 22 that locks onto the locking portion 241. By locking the hook portion 242 onto the locking portion 241, the upstream holder 22 and the downstream holder 23 are fixed in a state where they are clamping the filter element 21. In this embodiment, the locking portion 241 and the hook portion 242 are fastened to the upstream holder 22 or the downstream holder 23 by screws.

[0043] The hook portion 242 is attached to the upstream holder 22 via the lever portion 243, and the locking of the hook portion 242 to the locked portion 241 is performed by operating the lever portion 243.

[0044] Note that the holders 22 and 23 to which the locked portion 241 and the hook portion 242 are attached may be reversed. The fixing mechanism 24 may utilize a spring element or a toggle mechanism. Further, the fixing mechanism 24 may utilize an air cylinder. For example, the air cylinder is attached so as to press the downstream holder 23 in a direction approaching the upstream holder 22 via a piston. When an air cylinder is used for opening and closing the heating furnace 1, a common compressed air source can be used for that air cylinder.

[0045] The clamping portion 25 is provided between the upstream holder 22, the downstream holder 23 and the filter element 21, and clamps the peripheral edge portion of the filter element 21 in the thickness direction. Further, the clamping portion 25 functions as a joint that holds the filter element 21 inside in the lead-out flow path L2, and has an inlet 25x for introducing the mixed gas into the filter element 21 and an outlet 25y for leading out the mixed gas from the filter element 21.

[0046] More specifically, the clamping portion 25 has a pair of clamping plates 251x and 251y that clamp the filter element 21, and a fixture 252 that fixes the pair of clamping plates 251x and 251y in a state where the filter element 21 is clamped. Further, the clamping portion 25 has an O-ring 253 that is clamped between the pair of clamping plates 251x and 251y together with the filter element 21.

[0047] The pair of clamping plates 251 of the present embodiment each have a substantially disk shape with a through hole provided at the center, and their diameters are larger than that of the filter element 21. The pair of clamping plates 251 each have a concave portion on their opposing surfaces, and the peripheral edge portions of those concave portions clamp the peripheral edge portion of the filter element 21.

[0048] The through-hole of one clamping plate 251x located on the upstream side is the aforementioned inlet 25x, and in the clamped state where the clamping portion 25 is clamped between the upstream holder 22 and the downstream holder 23, it is connected to the upstream internal flow path 22x of the upstream holder 22. The through-hole of the other clamping plate 251y located on the downstream side is the outlet 25y, and in the clamped state, it is connected to the downstream internal flow path 23y of the downstream holder 23.

[0049] Also, a convex portion 254 is formed on the lower surface of one clamping plate 251 disposed on the lower side. This convex portion 254 fits snugly with the concave portion 221 formed on the opposing surface 22a of the aforementioned upstream holder 22, the guide groove 222.

[0050] The clamping plate 251 is formed of a transparent resin such as acrylic, for example, and is configured such that the state of the filter element 21 can be visually observed from the outside. The aforementioned upstream holder 22 and downstream holder 23 may also be formed of a transparent resin as well.

[0051] The fixture 252 of the present embodiment is a screw, which is screwed into screw holes formed in the peripheral portions of the pair of clamping plates 251 to fix them. The fixture 252 is not limited to a screw, and various fixtures such as clips and pins may be used. The fixture 252 is preferably removable.

[0052] The seal portion 26 is, for example, an O-ring, and includes an upstream seal portion 26x provided so as to surround the inlet 25x between the upstream holder 22 and the clamping plate 251x, and a downstream seal portion 26y provided so as to surround the outlet 25y between the downstream holder 23 and the clamping plate 251y.

[0053] In the present embodiment, the outer edge portion of the seal portion 26 is fitted inside the inner wall of the concave portion formed on the surface of the clamping plate 251, whereby the seal portion 26 is fixed to the clamping portion 25.

[0054] The slide mechanism 27 slides the downstream holder 23 along the clamping direction (vertical direction) relative to the upstream holder 22. The slide mechanism 27 in this embodiment is composed of three guide rails 271 attached to the upstream holder 22 and extending along the clamping direction, and three slide portions 272 formed as through holes that penetrate the downstream holder 23 in the clamping direction. The guide rails 271 are inserted through each slide portion 272, and the downstream holder 23 slides along the clamping direction as these slide portions 272 slide against the guide rails 271. Note that the specific configuration of the slide mechanism, such as the number of slide rails and their mounting positions, is not limited to the above.

[0055] An end stopper 273 and a spacer 274 are attached to the guide rail 271 to limit the range of movement of the downstream holder 23. The end stopper 273 in this embodiment consists of a washer and a screw provided at the end of the guide rail 271 extending from the upstream holder 22, and prevents the downstream holder 23 from coming off the guide rail 271. The spacer 274 is a cylindrical member that surrounds the outer circumference of the guide rail 271 and maintains a distance of at least a certain level between the upstream holder 22 and the downstream holder 23.

[0056] The elastic member 28 applies force to the upstream holder 22 and the downstream holder 23 in a direction that causes them to move away from each other. In this embodiment, the elastic member 28 is a coil spring provided between the upstream holder 22 and the downstream holder 23, with the guide rail 271 inserted through its center. The elastic member 28 may also apply force to either the upstream holder 22 or the downstream holder 23.

[0057] <Regarding filter replacement> The method for replacing the filter element 21 in the elemental analyzer 100 of this embodiment will be described below.

[0058] First, the user operates the lever portion 243 of the fixing mechanism 24 to release the hook portion 242 that is locked to the locking portion 241.

[0059] As a result, the upstream holder 22 and the downstream holder 23 are released from their fixed positions, and the restoring force of the elastic member 28 causes the downstream holder 23 to move away from the upstream holder 22 (upward). The downstream holder 23, having slid upward along the guide rail 271, comes into contact with the end stopper 273 and stops, as shown in Figure 5.

[0060] Next, the user removes the clamping portion 25 from between the upstream holder 22 and the downstream holder 23. Then, as shown in Figure 6, the user removes the fasteners 252 that secure the pair of clamping plates 251x and 251y of the clamping portion 25, and replaces the filter element 21 held inside the clamping portion 25 with a new filter element 21.

[0061] The user installs the clamping portion 25 after replacing the filter element 21 at a predetermined fixed position between the upstream holder 22 and the downstream holder 23. Specifically, the user installs the clamping portion 25 at a predetermined fixed position corresponding to the position of the recess 221 by fitting the protrusion 254 provided on the clamping portion 25 into the guide groove 222 provided on the upstream holder 22 and sliding it toward the recess 221.

[0062] Finally, the user presses the downstream holder 23 toward the upstream holder 22 while operating the lever portion 243 to lock the hook portion 242 onto the locking portion 241.

[0063] In this manner, the upstream holder 22 and the downstream holder 23 are fixed in a state where they are clamping the clamping portion 25, as shown in Figure 3. In this fixed state, the upstream internal flow path 22x of the upstream holder 22 and the inlet 25x of the clamping portion 25 are in communication, and the downstream internal flow path 23y of the downstream holder 23 and the outlet 25y of the clamping portion 25 are in communication, forming a series of filter flow paths through which the mixed gas flows into the filter unit 2.

[0064] Furthermore, the upstream sealing portion 26x and the downstream sealing portion 26y are pressed between the respective holders 22, 23 and clamping portion 25, respectively, sealing the gaps between them and preventing the mixed gas from leaking out of the filter passage.

[0065] <Effects of this embodiment> With the elemental analyzer 100 configured in this way, the force that grips the filter element 21 can be mechanically kept constant by fixing the upstream holder 22 and the downstream holder 23 with the fixing mechanism 24, which is a snap lock. As a result, the filter element 21 can be fixed with less influence from the user's skill level compared to fixing with screws or the like.

[0066] Since the filter element 21 is held along the horizontal direction, it is less likely that the filter element 21 will shift or flip over due to the effects of gravity.

[0067] Since the filter element 21 is clamped and fixed between the clamping parts 25, and then the filter element 21 is set together with the clamping parts 25 between the upstream holder 22 and the downstream holder 23, the filter element 21 is less likely to shift or curl up during this setting process, and the influence of the user's skill level is reduced, making it possible to replace the filter element 21.

[0068] <Second Embodiment> The elemental analyzer according to the second embodiment further includes a determination mechanism for determining when it is recommended to replace the filter element, in addition to the configuration of the first embodiment. The determination mechanism includes a detection unit for detecting the amount of dust collected in the filter element, and a determination unit for determining when it is recommended to replace the filter element based on the detection status of the detection unit.

[0069] The detection unit calculates, for example, the electrical resistance of the filter element and outputs this electrical resistance value as a dust amount corresponding to the amount of dust. When dust containing graphite is collected in the filter element, the electrical resistance of the filter element decreases.

[0070] In this case, the detection unit includes, for example, a pair of electrodes attached to the filter element, a power supply connected to the pair of electrodes, an ammeter for detecting the current flowing through the filter element, and a voltmeter for detecting the voltage applied to the filter element.

[0071] The determination unit receives the dust amount corresponding value output by the detection unit, compares this value with a predetermined threshold, and determines whether or not the filter element is due for replacement. Specifically, the determination unit is composed of an electrical circuit consisting of, for example, analog or digital circuits. The determination result from the determination unit is communicated to the user by displaying it on a screen, sounding an alarm, etc.

[0072] Alternatively, the timing for replacement of a filter element may be determined by comparing the current value or voltage value with its corresponding threshold value. Furthermore, the timing for replacement may be predicted based on the difference between the electrical resistance value and the threshold value.

[0073] <Effects of the Second Embodiment> With an elemental analyzer configured in this way, it is possible to determine the appropriate replacement time for the filter element based on the actual amount of dust collected. This allows for a better balance between reducing operating costs and ensuring measurement accuracy compared to conventional methods that determine replacement time based on the number of uses or usage period.

[0074] The detection unit may also be a differential pressure gauge, a flow meter, or a reflected light measuring meter that measures reflected light from a filter element, as described below.

[0075] In the case of a differential pressure gauge, the detection unit calculates the pressure difference between the upstream and downstream points of the filter unit in the outlet flow path. The determination unit then determines the recommended replacement time based on the pressure difference. When dust accumulates in the filter element and causes clogging, the flow resistance increases, and the pressure loss (pressure difference) increases.

[0076] In this case, the detection unit includes, for example, an upstream pressure sensor provided at the upstream point, a downstream pressure sensor provided at the downstream point, and a pressure difference calculator that calculates the pressure difference between these two pressure sensors.

[0077] In the case of a flow meter, the detection unit calculates the flow rate at the point downstream of the filter unit in the outlet channel. The determination unit then determines the recommended replacement time based on the flow rate. When dust accumulates in the filter element and causes clogging, the flow resistance increases and the flow rate decreases.

[0078] In the case of a reflected light meter, the detection unit calculates the reflected light intensity, which is the intensity of the light reflected from the filter element. The determination unit then determines the recommended replacement time based on the reflected light intensity. When dust containing graphite is collected in the filter element, visible light is more easily absorbed by the filter element, and the reflected light intensity decreases.

[0079] In this case, the detection unit includes, for example, a light irradiator that irradiates a filter element with visible light, a photodetector that detects reflected light from the filter element, and a reflected light intensity calculation unit that calculates the reflected light intensity based on the detected value of the photodetector.

[0080] <Other Modified Embodiments> The present invention is not limited to the embodiments described above.

[0081] The filter element is not limited to membrane filters. For example, it may be a film-like filter made of a material other than resin, or a filter in which quartz wool is filled into a container. Furthermore, the filter element is not limited to being held horizontally.

[0082] In the above embodiment, the upstream holder and the downstream holder held the filter element via a clamping portion; however, the upstream holder and the downstream holder may clamp the filter element.

[0083] In the above embodiment, the upstream holder and the downstream holder were connected by a sliding mechanism. However, the upstream holder and the downstream holder may also be connected by a hinge or other mechanism located on the opposite side of the fixing mechanism. Alternatively, the upstream holder and the downstream holder may be connected using two snap locks attached to their respective sides.

[0084] The analyzer is not limited to the embodiments described above. For example, the analyzer may detect multiple components or a single component.

[0085] The filter unit should preferably be detachably mounted to the piping that constitutes the outlet channel.

[0086] Furthermore, various modifications of the embodiments and combinations of parts of each embodiment are permitted, as long as they do not contradict the spirit of the present invention.

[0087] According to the present invention, it becomes possible to replace filters appropriately regardless of the user's skill level.

[0088] 100... Elemental analyzer 3... Heating furnace 4... Dust filter 41... Filter element 42... Filter holder 5... Analyzer R... Cleaning gas supply mechanism RS... Cleaning gas supply section RC... Flow path switching section R1... Cleaning gas supply source R2... Cleaning gas supply flow path R3... First three-way valve R4... Second three-way valve

Claims

1. The apparatus comprises: a heating furnace for heating a sample to generate a sample gas; an introduction channel for introducing a carrier gas into the heating furnace; an outlet channel from which a mixed gas consisting of the carrier gas and the sample gas is discharged from the heating furnace; a filter unit provided on the outlet channel for filtering the mixed gas flowing through the outlet channel; and an analyzer provided downstream of the filter unit on the outlet channel for analyzing components contained in the mixed gas, wherein the filter unit comprises: a filter element for collecting dust in the mixed gas; an upstream holder and a downstream holder facing each other with the filter element in between; and a fixing mechanism for fixing the filter element with the upstream holder and the downstream holder in a clamped state, wherein the fixing mechanism comprises: a locking portion provided on one of the upstream holder and the downstream holder; and a hook portion provided on the other of the upstream holder and the downstream holder for locking onto the locking portion. An elemental analyzer that fixes the upstream holder and the downstream holder by engaging the hook portion with the locking portion.

2. The elemental analyzer according to claim 1, wherein the filter element is in the form of a sheet.

3. The elemental analyzer according to claim 2, wherein the filter element is held horizontally in the filter unit.

4. The elemental analyzer according to any one of claims 1 to 3, wherein the filter unit is interposed between the upstream holder and the downstream holder and the filter element, and further has a clamping portion that clamps the peripheral edge of the filter element from the thickness direction, the clamping portion is clamped and fixed by the upstream holder and the downstream holder by engaging the hook portion with the locked portion, and the clamping portion is removed from the upstream holder and the downstream holder together with the filter element by releasing the hook portion from the locked portion.

5. The elemental analyzer according to claim 4, wherein the clamping portion comprises a pair of clamping plates for clamping the filter element and a fixing device for fixing the pair of clamping plates together in the state in which the filter element is clamped.

6. An elemental analyzer according to claim 4 or 5, wherein a guide groove is formed on one opposing surface of the upstream holder and the downstream holder, extending from a predetermined fixing position for fixing the clamping portion to the outer surface, and the clamping portion has a protrusion formed thereon that fits into the guide groove and moves within the guide groove.

7. The elemental analyzer according to any one of claims 4 to 6, wherein the upstream holder and the downstream holder have internal passages communicating with the outlet passage, the clamping portion has an inlet for introducing gas into the filter element and an outlet for discharging gas from the filter element, and when the upstream holder and the downstream holder clamp the clamping portion, the internal passage of the upstream holder communicates with the inlet, and the internal passage of the downstream holder communicates with the outlet to form a series of passages, and the filter unit further comprises an upstream seal portion provided between the upstream holder and the clamping portion so as to surround the inlet, and a downstream seal portion provided between the downstream holder and the clamping portion so as to surround the outlet.

8. The elemental analyzer according to claim 7, wherein the filter unit further comprises a sliding mechanism for sliding the other of the upstream holder or the downstream holder along the clamping direction relative to one of the upstream holder and the downstream holder.

9. The elemental analyzer according to any one of claims 1 to 8, wherein the filter unit further comprises an elastic member that applies force to the upstream holder or the downstream holder in a direction that causes the upstream holder and the downstream holder to move away from each other.

10. An elemental analyzer according to any one of claims 1 to 9, further comprising a determination mechanism for determining the recommended replacement time for the filter element, wherein the determination mechanism comprises a detection unit that calculates and outputs the electrical resistance of the filter element, and a determination unit that compares the electrical resistance with a predetermined threshold to determine whether or not the filter element is due for replacement.

11. A filter unit provided in an outlet channel from which gas is discharged from a heating furnace that heats a sample to generate a sample gas, comprising: a filter element for collecting dust in the gas; an upstream holder and a downstream holder facing each other with the filter element in between; and a fixing mechanism for fixing the filter element with the upstream holder and the downstream holder in a clamped state, wherein the fixing mechanism comprises: a locking portion provided on one of the upstream holder and the downstream holder; and a hook portion provided on the other of the upstream holder and the downstream holder for locking with the locking portion, thereby fixing the upstream holder and the downstream holder.

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