thermal conductivity detector

Abstract

A thermal conductivity detector (1) is provided with: a cell block (2) provided with a measuring cell (10) in which a heating wire (12) for exchanging heat with a gas is arranged, the cell block (2) being provided with a cell inlet (11) for flowing the gas into the measuring cell (10) and a cell outlet (13) for flowing the gas out of the measuring cell (10); an outlet flow path (4) leading to the cell outlet (13) of the cell block (2); a buffer block (6) having a buffer space (14) in the inside and having a flow inlet (15) for flowing the gas into the buffer space (14) and a discharge outlet (16) for discharging the gas from the buffer space (14), the flow inlet (15) being fluidly connected to the outlet flow path (4); and a discharge member (8) holding a fluid resistance portion (20) for increasing a fluid resistance of the discharge outlet (16) and being installed to the buffer block (6) in a manner that the gas discharged from the discharge outlet (16) passes through the fluid resistance portion (20), the discharge member (8) being provided to be able to be detached from the buffer block (6) together with the fluid resistance portion (20).

Description

TECHNICAL FIELD

[0001] The present application relates to a thermal conductivity detector as one of detectors for component detection in a gas chromatograph. BACKGROUND

[0002] A thermal conductivity detector as one of detectors of a gas chromatograph is known. The thermal conductivity detector is configured with a heating wire in a measurement cell in which a gas flows, and quantifies a component in the gas by detecting an amount of heat exchange between the heating wire and the gas. The amount of heat exchange between the heating wire and the gas varies depending on a flow rate of the gas flowing in the measurement cell, and therefore if the flow rate of the gas flowing in the measurement cell varies, a baseline of measurement data also varies, which adversely affects an analysis result.

[0003] For the above reason, it is important to maintain the flow rate of the gas flowing in the measurement cell to be constant. As a main cause of variation in the flow rate of the gas flowing in the measurement cell, variation in atmospheric pressure is cited. Since the outlet of the measurement cell is open to the atmosphere, when the atmospheric pressure varies, the pressure difference between the inlet and the outlet of the measurement cell varies, which causes the flow rate of the gas flowing in the measurement cell to vary. Therefore, a scheme is proposed in which a buffer space is provided downstream of the measurement cell and the outlet of the buffer space is provided with a certain fluid resistance, thereby making the atmospheric pressure variation less likely to be transmitted to the outlet of the measurement cell, suppressing the pressure variation at the outlet of the measurement cell, and stabilizing the baseline of the measurement data (see Patent Literature 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2016-080413 SUMMARY

[0007] Problems to be Solved by the Invention

[0008] In the case where the buffer space is provided downstream of the measurement cell, the larger the volume of the buffer space and the greater the fluid resistance of the outlet of the buffer space, the higher the effect of suppressing the pressure variation at the outlet of the measurement cell, and the more stable the baseline. On the other hand, if a large-volume buffer space is provided downstream of the measurement cell, the detector becomes large. In order to reduce the volume of the buffer space and stabilize the baseline, it is necessary to increase the fluid resistance by reducing the inner diameter of the flow path of the outlet of the buffer space or the like. However, if the fluid resistance of the outlet of the buffer space is increased, there is a problem that the sample is likely to be clogged at this portion.

[0009] The present application was made in view of the above problems, and aims to achieve both stabilization of the baseline and miniaturization of the detector.

[0010] Means for Solving the Problems

[0011] The heat conduction detector of the present application is provided with: a cell block provided with a measuring cell inside, the measuring cell being a space provided with a heating wire for exchanging heat with a gas, the cell block being provided with a cell inlet for causing the gas to flow into the measuring cell and a cell outlet for causing the gas to flow out from the measuring cell; an outlet flow path leading to the cell outlet of the cell block; a buffer block having a buffer space inside and having a flow inlet for causing the gas to flow into the buffer space and a discharge outlet for causing the gas to be discharged from the buffer space, the flow inlet being fluidly connected to the outlet flow path; and a discharge member holding a fluid resistance portion for increasing the fluid resistance of the discharge outlet, the discharge member being installed to the buffer block in such a manner that the gas discharged from the discharge outlet passes through the fluid resistance portion, the discharge member being configured to be able to be detached from the buffer block together with the fluid resistance portion.

[0012] The present application is characterized in that, when a clogging occurs at the fluid resistance portion for increasing the fluid resistance of the outlet (discharge outlet) of the buffer space, the fluid resistance portion can be easily replaced. Here, as a member that realizes the fluid resistance portion, a resistance tube, a filter, and the like are exemplified. In the case where the fluid resistance portion is realized by a resistance tube, a fine resistance tube having an outer diameter of 1 mm or less needs to be installed to the buffer block in correspondence with the small capacity of the buffer space, but such a fine resistance tube cannot be installed to the discharge outlet of the buffer space in the same connection method as general piping. In the present application, the fluid resistance portion is held to the discharge member that is detachably installed to the buffer block, and the fluid resistance portion can be detached from the buffer block by detaching the discharge member from the buffer block.

[0013] Effects of the Invention

[0014] As described above, in the heat conduction detector of the present application, the fluid resistance portion is held to the discharge member that is detachably installed to the buffer block, and the fluid resistance portion can be detached from the buffer block by detaching the discharge member from the buffer block, so that the fluid resistance portion can be easily replaced when a clogging occurs at the fluid resistance portion, and the stabilization of the baseline and the miniaturization of the detector can be achieved in balance. BRIEF DESCRIPTION OF DRAWINGS

[0015] Fig. 1 is a cross-sectional view showing one embodiment of a heat conduction detector.

[0016] Fig. 2 is a cross-sectional view showing the configuration of the discharge member of the embodiment.

[0017] Fig. 3is a cross-sectional view schematically showing another embodiment of a thermal conductivity detector.

[0018] Fig. 4 is a cross-sectional view schematically showing still another embodiment of a thermal conductivity detector. DETAILED DESCRIPTION

[0019] Hereinafter, an embodiment of a thermal conductivity detector of the present application will be described with reference to the drawings.

[0020] As Fig. 1 shown, a thermal conductivity detector 1 is provided with a cell block 2, an outlet pipe 4, a buffer block 6, and a discharge member 8.

[0021] The cell block 2 is internally provided with a measurement cell 10 in which a heating wire 12 is arranged, and is provided with a cell inlet 11 for flowing a gas into the measurement cell 10 and a cell outlet 13 for flowing the gas out of the measurement cell 10. One end of the outlet pipe 4 constituting an outlet flow path is fluidly connected to the cell outlet 11 of the cell block 2. The heating wire 12 is used for heat exchange with the gas flowing in the measurement cell 10. The thermal conductivity detector 1 performs quantification of a component contained in a gas by reading a signal corresponding to the amount of heat exchange between the gas flowing in the measurement cell 10 and the heating wire 12.

[0022] The buffer block 6 is internally provided with a buffer space 14. Further, the buffer block 6 is provided with a flow inlet 15 for flowing a gas into the buffer space 14 and a discharge outlet 16 for discharging the gas from the buffer space 14. The other end of the outlet pipe 4 is fluidly connected to the flow inlet 15 of the buffer block 6. The cross-sectional area of the buffer space 14 perpendicular to the direction of flow of the gas from the flow inlet 15 is larger than the cross-sectional area of the flow path (i.e., the outlet flow path) on the inside of the outlet pipe 4 perpendicular to the direction of the flow path. The discharge member 8 is attached to the buffer block 6 in a detachable manner with respect to the buffer block 6.

[0023] Further, in Fig. 1 the present embodiment, only one measurement cell 10 is illustrated in the inside of the cell block 2, but two measurement cells 10, one for a sample gas and the other for a reference gas, can be provided in the inside of the cell block 2. In the case where two measurement cells 10 are provided in the cell block 2, these measurement cells 10 can be fluidly connected to a common buffer space 14, or two buffer spaces 14 can be provided in the buffer block 6 and the two measurement cells 10 can be fluidly connected to the respective buffer spaces 14.

[0024] As Fig. 2As shown, the discharge member 8 is provided with a resistance tube 20, a holding member 22, a fixing member 24, and a seal ring 26. The resistance tube 20 is, for example, a linear tube of a fine size with an outer diameter of 1 mm or less and an inner diameter of 0.5 mm or less, and constitutes a fluid resistance portion for increasing the fluid resistance of the discharge port 16. The holding member 22 is made of a resin material (e.g., silicone rubber) having elasticity, and the outer peripheral surface of the resistance tube 20 is held by making the resistance tube 20 penetrate through the holding member 22. The fixing member 24 is a member made of metal, has a recess for embedding and holding the holding member 22, and is attached to the portion of the buffer block 6 provided with the discharge port 16 in a detachable manner in a state where the holding member 22 is held by the recess.

[0025] A cylindrical protrusion 18 is provided on the portion of the outer surface of the buffer block 6 provided with the discharge port 16, and a thread is provided on the outer peripheral surface of the protrusion 18. A thread that threadedly engages with the thread of the outer peripheral surface of the protrusion 18 of the buffer block 6 is provided on the inner peripheral surface of the fixing member 24 of the discharge member 8, and the discharge member 8 can be attached to and detached from the buffer block 6 by rotating the fixing member 24.

[0026] The discharge member 8 is attached to the buffer block 6 in a manner that the resistance tube 20 fluidically connects the buffer space 14 and the atmosphere. The seal ring 26 is interposed between the top end of the protrusion 18 of the buffer block 6 and the holding member 22 of the discharge member 8. The seal ring 26 is used to deform the holding member 22 made of resin at the top end of the protrusion 18 to improve the sealability, thereby preventing the gas from being discharged through a path other than the resistance tube 20.

[0027] According to the above-described configuration, the fluid resistance with respect to the gas discharged from the discharge port 16 is large, and the capacity of the buffer space 14 can be reduced to achieve the miniaturization of the buffer block 6. Since the resistance tube 20 is fine, clogging of the sample in the resistance tube 20 occurs, but since the discharge member 8 that integrally holds the resistance tube 20 can be easily attached to and detached from by rotating the fixing member 24, the replacement of the resistance tube 20 is easy.

[0028] Further, as the fluid resistance portion for increasing the fluid resistance of the discharge port 16, a filter (metal crystal filter, ceramic filter, etc.) can also be used instead of the resistance tube 20. In this case, the filter can be held by the holding member 22 or can be welded to the fixing member 24 of the discharge member 8.

[0029] In addition, the attachment and detachment configuration of the discharge member 8 to the buffer block 6 is not limited to the configuration using the thread engagement of the thread, and is a configuration in which the discharge member 8 can be attached to and detached from the buffer block 6. In addition, the discharge member 8 does not necessarily have to be directly attached to and detached from the buffer block 6, and can be configured to be attached to and detached from the buffer block 6 with the aid of a pipe.

[0030] In addition, as shown in FIG. 6, the discharge member 8 can be configured to be attached to and detached from the buffer block 6 by a screwing operation.Fig. 3 and Fig. 4 As shown in FIG. 1, in order to prevent clogging in the fluid resistance section such as the resistance tube 20, a heat retaining section for preventing a decrease in temperature of the discharge member 8 can also be provided. In the example of FIG. 1, the heat retaining section is constituted by the heat insulating member 30 that surrounds the periphery of the discharge member 8, thereby avoiding escape of heat transmitted to the discharge member 8 via the metal outlet pipe 4 and the buffer block 6. In the example of FIG. 2, the heat retaining section is constituted by the metal heat conducting block 32 that is in contact with the discharge member 8 and the heater 34 that heats the heat conducting block 32. Fig. 3 Fig. 4 In the example of FIG. 2, the heat retaining section is constituted by the metal heat conducting block 32 that is in contact with the discharge member 8 and the heater 34 that heats the heat conducting block 32.

[0031] The above-described embodiments merely exemplify the implementation of the thermal conductivity detector of the present application. The implementation of the thermal conductivity detector of the present application is described below.

[0032] In the implementation of the thermal conductivity detector of the present application, there are provided: a cell block that has a measurement cell inside, the measurement cell being a space in which a heating wire for exchanging heat with a gas is arranged, the cell block having a cell inlet for causing the gas to flow into the measurement cell and a cell outlet for causing the gas to flow out of the measurement cell; an outlet flow path that leads to the cell outlet of the cell block; a buffer block that has a buffer space inside and has a flow inlet for causing the gas to flow into the buffer space and a discharge outlet for causing the gas to be discharged from the buffer space, the flow inlet being fluidly connected to the outlet flow path; and a discharge member that holds a fluid resistance section for increasing the fluid resistance of the discharge outlet, the discharge member being installed to the buffer block in such a manner that the gas discharged from the discharge outlet passes through the fluid resistance section, the discharge member being configured to be detachable from the buffer block together with the fluid resistance section.

[0033] In the first mode of the implementation of the thermal conductivity detector of the present application, the fluid resistance section is a resistance tube.

[0034] In the above-described first mode, the outer diameter of the resistance tube is 1 mm or less. It is difficult to install the fine resistance tube having an outer diameter of 1 mm or less to the buffer block in a detachable manner by screwing or the like, but in the implementation of the present application, the resistance tube is detachable with respect to the buffer block in conjunction with the attachment and detachment of the discharge member, so even the fine resistance tube is easily replaced.

[0035] In the above-described first mode, the discharge member can have: a holding member that holds the outer peripheral surface of the resistance tube; and a fixing member that is fixed to the buffer block in a detachable manner while holding the holding member.

[0036] In the above-described case, the holding member can be constituted by a resin material having elasticity. According to such a mode, the fine resistance tube can be prevented from being bent.​

[0037] In the second aspect of the embodiment of the thermal conductivity detector of the present application, the fluid resistance portion is a filter.

[0038] In the third aspect of the embodiment of the thermal conductivity detector of the present application, a heat retaining portion that prevents the temperature of the discharge member from decreasing is further provided. According to this aspect, clogging of the sample in the fluid resistance portion can be suppressed.

[0039] In the third aspect described above, the heat retaining portion can include a heat conducting block that contacts the discharge member, and a heater that heats the heat conducting block.

[0040] Explanation of Reference Numerals

[0041] 1 Thermal conductivity detector; 2 Cell block; 4 Outlet pipe; 6 Buffer block; 8 Discharge member; 10 Measuring cell; 11 Cell inlet; 12 Heating wire; 13 Cell outlet; 14 Buffer space; 15 Inlet; 16 Outlet; 18 Protrusion; 20 Resistance pipe (fluid resistance portion); 22 Retaining member; 24 Fixing member; 26 Sealing ring; 30 Heat insulating member; 32 Heat conducting block.

Claims

1. A thermal conductivity detector, wherein, This thermal conductivity detector has the following features: A unit block having a measuring unit inside, the measuring unit being a space configured with a heating wire for heat exchange with gas, the unit block having a unit inlet for gas to flow into the measuring unit and a unit outlet for gas to flow out of the measuring unit; An outlet flow path that leads to the unit outlet of the unit block; A buffer block having a buffer space inside, and having an inlet for gas to flow into the buffer space and an outlet for gas to discharge from the buffer space, the inlet being fluidly connected to the outlet flow path; as well as A discharge member, which retains the outer peripheral surface of a fluid resistance section for increasing the fluid resistance of the discharge port, is mounted on the buffer block such that gas discharged from the discharge port passes through the fluid resistance section. This discharge member is configured to be removable from the buffer block integrally with the fluid resistance section. The fluid resistance section is a resistance pipe. The outer diameter of the resistance pipe is smaller than the inner diameter of the outlet, and the fluid resistance of the resistance pipe is higher than the fluid resistance of the outlet. The outer surface of the buffer block is provided with a protrusion, and the discharge component is installed on the protrusion.

2. The thermal conductivity detector according to claim 1, wherein, The outer diameter of the resistance tube is less than 1 mm.

3. The thermal conductivity detector according to claim 1, wherein... The discharge member includes: a retaining member that retains the outer peripheral surface of the resistance tube; and a fixing member that is detachably fixed to the buffer block while retaining the retaining member.

4. The thermal conductivity detector according to claim 3, wherein, The retaining member is made of an elastic resin material.

5. The thermal conductivity detector according to claim 1, wherein, The fluid resistance section is a filter.

6. The thermal conductivity detector according to claim 1, wherein, The thermal conductivity detector also has an insulation section to prevent the temperature of the discharge component from dropping.

7. The thermal conductivity detector according to claim 6, wherein, The heat insulation section includes a heat-conducting block that contacts the discharge member and a heater for heating the heat-conducting block.

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