Thermal conductivity detection unit and gas chromatograph

Abstract

To provide a technology for improving the accuracy of the operation control of the heating device for a thermal conductivity detector. [Solution] The controller for controlling the thermal conductivity detector is configured to control the output of the heating device of the thermal conductivity detector with an output corresponding to the measurement result of the temperature sensor in basic control. However, if the temperature of the first component housing the filament and the temperature sensor is outside the first range relative to the temperature of the second component housing the heating device, the controller is configured to control the output of the heating device with an output corresponding to the measurement result in output reduction control. In output reduction control, the output of the heating device is controlled with an output that is reduced from the output corresponding to the measurement result in basic control.

Description

Technical Field

[0001] The present invention relates to improving the accuracy of operation control of a heating device of a thermal conductivity detector.

Background Art

[0002] Conventionally, as described in, for example, Japanese Patent Application Laid-Open No. 2020-041989 (Patent Document 1), a heating device (heater) was provided in a thermal conductivity detector. Thereby, the temperature of the portion for detecting the thermal conductivity including the filament was avoided from changing due to factors other than the composition or concentration of the gas to be detected as much as possible.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [ In a conventional thermal conductivity detector, from the viewpoint of reducing manufacturing costs, a general-purpose unit housed in a member having a relatively high thermal conductivity may be adopted as the heating device. In such a case, the filament is housed in a member having a relatively low thermal conductivity together with the temperature sensor. And, in such a case, when the operation of the heating device is controlled using the detected temperature of the temperature sensor, before the detected temperature reaches the target temperature, the member housing the heating device may reach the target temperature. As a result, when the detected temperature reaches the target temperature, the temperature of the member housing the heating device may exceed the target temperature. Therefore, when the heating device is controlled based on the detected temperature, an overshoot regarding the temperature may occur. As a result, when performing an analysis using the thermal conductivity detector, a situation occurs in which a long time is required until the temperature of the above-mentioned portion in the thermal conductivity detector becomes stable, and in the thermal conductivity detector, improvement in the accuracy of operation control of the heating device has been desired.

[0005] This invention was conceived in view of the above circumstances, and its purpose is to provide a technology for improving the accuracy of the operation control of the heating device of a thermal conductivity detector. [Means for solving the problem]

[0006] A thermal conductivity detection unit according to a certain aspect of the present disclosure comprises a thermal conductivity detector and a controller configured to control the thermal conductivity detector, wherein the thermal conductivity detector includes a first member, a second member having a higher thermal conductivity than the first member, a heating device housed in the second member, and a filament and a temperature sensor housed in the first member, and the controller is configured to control the output of the heating device with an output corresponding to the measurement result of the temperature sensor in basic control, and, if the temperature of the first member is outside a first range with respect to the temperature of the second member, to control the output of the heating device with an output corresponding to the measurement result in output reduction control, in which the output of the heating device is controlled with an output reduced from the output corresponding to the measurement result in basic control.

[0007] A gas chromatograph according to a certain aspect of this disclosure comprises a sample vaporization unit that generates a sample gas by vaporizing a sample, a column for separating the components of the sample gas generated by the sample vaporization unit, and the thermal conductivity detection unit described above, wherein the thermal conductivity detection unit detects the thermal conductivity of each component of the sample gas separated by the column. [Effects of the Invention]

[0008] In accordance with certain aspects of this disclosure, a technique is provided for improving the accuracy of the operational control of a heating device for a thermal conductivity detector. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the configuration of a gas chromatograph including one embodiment of a thermal conductivity detection unit. [Figure 2]This figure shows an example of a control block related to the operation control of a heating device. [Figure 3] This figure shows an example of the information used to set thresholds. [Figure 4] This figure shows the information presented in Figure 3, along with different annotations. [Figure 5] This figure shows the information presented in Figure 3, along with different annotations. [Figure 6] This is a flowchart of the output control process of the heating device 70H for controlling the first conduit 71 containing the filament F to a target temperature. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] [Outline of gas chromatograph configuration and basic operation] Figure 1 is a block diagram showing the configuration of a gas chromatograph including one embodiment of a thermal conductivity detection unit. As shown in Figure 1, the gas chromatograph 1 includes a gas tank 10, a flow rate adjustment unit 20, a sample vaporization unit 30, a column 40, a flow rate adjustment unit 50, a switching valve 60, a thermal conductivity detector 70, and a control unit 80.

[0012] The gas tank 10 stores a carrier gas for guiding the sample gas to the column 40 and the thermal conductivity detector 70. An inert gas such as helium gas is used as the carrier gas.

[0013] The gas tank 10 supplies carrier gas to two flow rate adjustment units 20 and 50 via a branch pipeline. One of the flow rate adjustment units 20 supplies a predetermined flow rate of carrier gas to the sample vaporization unit 30 based on the control of the control unit 80.

[0014] The sample vaporization unit 30 includes an injector and a vaporization chamber. The sample is injected into the vaporization chamber of the sample vaporization unit 30 via the injector. The internal atmosphere of the vaporization chamber is maintained in a state where the sample can vaporize. As a result, the sample injected into the vaporization chamber vaporizes inside it. The sample vaporization unit 30 supplies the vaporized sample to the column 40 while mixing it with a carrier gas supplied from the flow rate adjustment unit 20. In the following description, the gas containing the components of the sample vaporized in the sample vaporization unit 30 is collectively referred to as the sample gas.

[0015] Column 40 is housed in a column oven (not shown). In column 40, each component of the sample gas supplied from the sample vaporization unit 30 is separated. Column 40 supplies the sample gas, separated by component, to the sample introduction conduit 76 of the thermal conductivity detector 70.

[0016] The flow rate adjustment unit 50 supplies a predetermined flow rate of carrier gas to the switching valve 60 based on the control of the control unit 80. The switching valve 60 is, for example, a three-way solenoid valve, and is connected to the flow rate adjustment unit 50 and also to two carrier gas introduction lines 75 and 77 of the thermal conductivity detector 70, which will be described later. Based on the control of the control unit 80, the flow rate adjustment unit 50 supplies the carrier gas supplied from the flow rate adjustment unit 50 to either of the carrier gas introduction lines 75 or 77.

[0017] Furthermore, as a configuration for supplying the carrier gas passing through the flow rate adjustment unit 50 to one of the two carrier gas introduction pipelines 75 and 77, a switching mechanism including multiple control valves and branch pipelines may be used instead of the switching valve 60. For example, the main pipeline is connected to the flow rate adjustment unit 50, and the two sub-pipes are connected to the carrier gas introduction pipelines 75 and 77, respectively. In addition, two control valves are provided for each of the two sub-pipes. In this case, by controlling the open and closed states of the two control valves, the carrier gas supplied from the flow rate adjustment unit 50 can be selectively supplied to one of the two carrier gas introduction pipelines 75 and 77 of the thermal conductivity detector 70.

[0018] The thermal conductivity detector 70 according to the present embodiment includes a first pipeline 71, a second pipeline 72, a third pipeline 73, a fourth pipeline 74, carrier gas introduction pipelines 75 and 77, a sample introduction pipeline 76, and an exhaust pipeline 78 that each extend linearly. These plurality of pipelines are formed by, for example, metal pipes. Among the plurality of pipelines of the thermal conductivity detector 70, the first to fourth pipelines 71 to 74 are housed in a cell block 70X together with a heating device 70H. The cell block 70X is produced by processing and joining a plurality of plate-like members made of metal. In the cell block 70X, the heating device 70H is housed in an aluminum block 70A.

[0019] The first pipeline 71 and the second pipeline 72 are formed so as to face each other and extend in parallel. The third pipeline 73 is formed so as to connect one end of the first pipeline 71 and one end of the second pipeline 72, and the fourth pipeline 74 is formed so as to connect the other end of the first pipeline 71 and the other end of the second pipeline 72. A filament F is housed inside the first pipeline 71. On the other hand, the filament F is not housed inside the second pipeline 72. Further, a temperature sensor 79 is housed inside the first pipeline 71.

[0020] The third pipeline 73 is provided with a first gas introduction part 73a, a second gas introduction part 73b, and a third gas introduction part 73c arranged in this order. Among the first to third gas introduction parts 73a to 73c, the first gas introduction part 73a is the closest to the first pipeline 71, and the third gas introduction part 73c is the closest to the third pipeline 73.

[0021] The carrier gas introduction pipeline 75 is formed so as to extend from the first gas introduction part 73a to the outside of the cell block 70X. The sample introduction pipeline 76 is formed so as to extend from the second gas introduction part 73b to the outside of the cell block 70X. The carrier gas introduction pipeline 77 is formed so as to extend from the third gas introduction part 73c to the outside of the cell block 70X.

[0022] The fourth conduit 74 is provided with a gas outlet 74a. The exhaust conduit 78 is formed to extend from the gas outlet 74a to the outside of the cell block 70X. A through hole is formed in the gas outlet 74a. This allows the internal space of the fourth conduit 74 and the internal space of the exhaust conduit 78 to communicate. The exhaust conduit 78 has an outlet 78e on the outside of the cell block 70X.

[0023] The heating device 70H is controlled by the control unit 80 and maintains the space within the cell block 70X at a temperature similar to the temperature inside the vaporization chamber of the sample vaporization unit 30 or the temperature inside the column oven housing the column 40. For example, a cartridge heater is used as the heating device 70H.

[0024] The control unit 80 is composed of, for example, a CPU (Central Processing Unit) and memory or a microcomputer, and controls the operation of each component of the gas chromatograph 1 as described above. In addition, the control unit 80 in this example further includes a drive circuit for driving the filament F and a detection circuit for detecting changes in the resistance of the filament F.

[0025] The above-mentioned switching valve 60 can be switched between a first state in which carrier gas is supplied to one carrier gas introduction pipeline 75 and a second state in which carrier gas is supplied to the other carrier gas introduction pipeline 77 at a predetermined period (for example, about 100 msec).

[0026] In this case, inside the third conduit 73 of the thermal conductivity detector 70, when the switching valve 60 is in the first state, the pressure in the space on the side of the first gas inlet 73a is higher than that of the second gas inlet 73b. As a result, the sample gas supplied to the sample introduction conduit 76 flows through the second conduit 72 together with a portion of the carrier gas introduced from the first gas inlet 73a. The remaining carrier gas introduced from the first gas inlet 73a flows through the first conduit 71 as a reference gas.

[0027] On the other hand, inside the third conduit 73 of the thermal conductivity detector 70, when the switching valve 60 is in the second state, the pressure in the space on the side of the third gas inlet 73c is higher than that of the second gas inlet 73b. As a result, the sample gas supplied to the sample introduction conduit 76 flows through the first conduit 71 together with a portion of the carrier gas introduced from the third gas inlet 73c. ​​The remaining carrier gas introduced from the third gas inlet 73c flows through the second conduit 72.

[0028] As a result, the control unit 80 measures the thermal conductivity of the sample gas based on the change in the resistance value of the filament F between the time the reference gas passes around the filament F and the time the sample gas passes around the filament F.

[0029] [Overview of heating device operation control] Figure 2 shows an example of a control block related to the operation control of a heating device. The example in Figure 2 represents feedback (FB) control that utilizes the difference (error) between the measurement result of the temperature sensor 79 (temperature measured by the temperature sensor 79) and the target temperature. Figure 2 shows the FB control unit 200, the monitoring unit 201, the output limiting unit 202, and the controlled object 220. The controlled object 220 refers to the heating device 70H in Figure 1.

[0030] Basically, the FB control unit 200 controls the output of the controlled device 220 according to the basic control. In the basic control, the output (value) of the controlled device 220 is set based on the above error, and the controlled device 220 is controlled to achieve the set output.

[0031] In the example shown in Figure 2, the monitoring unit 201 determines whether the temperature of the member housing the filament F and the temperature sensor 79 (first conduit 71: first member) is outside a first range and whether it is within a second range relative to the temperature of the member housing the heating device (aluminum block 70A: second member).

[0032] Whether the temperature of the first component is outside a first range relative to the temperature of the second component, and whether the temperature of the first component is within a second range relative to the temperature of the second component, may be determined based on direct measurement results of the temperatures of both components, or it may be determined indirectly by other methods.

[0033] When the monitoring unit 201 determines that the temperature of the first component is outside the first range relative to the temperature of the second component, it instructs the output limiting unit 202 to execute output reduction control. Output reduction control is a control that reduces the output to be realized for the controlled object 220 to an output set by the FB control unit 200. The output controlled by the output limiting unit 202 may be the output set by the FB control unit 200 minus a certain value, or it may be "zero", as long as it is lower than the output set by the FB control unit 200.

[0034] The output limiting unit 202 performs output reduction control in response to instructions from the monitoring unit 201. As a result of the output reduction control, the output that is instructed to be realized for the controlled object 220 will be lower than the output set by the FB control unit 200.

[0035] Subsequently, when the monitoring unit 201 determines that the temperature of the first component is within the second range relative to the temperature of the second component, it instructs the output limiting unit 202 to release the output reduction control. The control of the controlled object 220 returns to basic control. As a result, the output instructed to the controlled object 220 returns to the output set by the FB control unit 200.

[0036] In this embodiment, an example of "basic control" is PID (Proportional Integral Differential) control. Note that the basic control may be any control that utilizes the measurement results of the temperature sensor 79, such as a control that switches the output of the controlled object 220 on or off according to the measurement results, or a control in which the output of the controlled object 220 is set as a linear function of the measurement results.

[0037] In this embodiment, the controlled object 220 (heating device) is housed in a material with relatively high thermal conductivity. This allows heat from the heating device to be efficiently transferred to other elements in the thermal conductivity detector. In this specification, aluminum (aluminum block) is shown as an example of a material with relatively high thermal conductivity, but the specification is not limited to this, and other types of materials such as copper may also be used.

[0038] Furthermore, the filament is housed in a material with relatively low thermal conductivity. This allows for stabilization of the temperature of the filament and its surroundings. In this specification, stainless steel is shown as an example of a material with relatively low thermal conductivity, but the specification is not limited to stainless steel, and other types of materials such as titanium may also be used.

[0039] Furthermore, the temperature sensor is housed in the same component that contains the filament, and the operation of the heating device is controlled based on the measurement results of the temperature sensor and according to basic control. This ensures that the temperature around the filament is more reliably reflected in the measurement results of the temperature sensor and more reliably reflected in the operation control of the heating device.

[0040] Furthermore, in the operation control of the heating device, if the temperature of the heating device rises and the temperature of the component housing the heating device (second component) deviates significantly from the temperature of the component housing the filament and temperature sensor (first component) (i.e., the temperature difference between the two is outside the first range), the output of the heating device is temporarily adjusted to be lower than the output corresponding to the measurement result in the basic control. This suppresses the occurrence of overshoot.

[0041] Subsequently, when the temperature of the component housing the filament and temperature sensor (the first component) approaches the temperature of the component housing the heating device (the second component) (if the temperature difference between the two is within the second range), the output control of the heating device is returned to the basic control described above. This controls the heating device so that the filament temperature reaches the target temperature more quickly.

[0042] Therefore, according to this disclosure, the operation of the heating device is controlled to bring the filament temperature to the target temperature earlier while suppressing the occurrence of overshoot.

[0043] [Prerequisites for setting thresholds] In this embodiment, thresholds are used to determine whether the temperature of the first member (first conduit 71) is outside a first range relative to the temperature of the second member (aluminum block 70A), and whether the temperature of the first member is within a second range relative to the temperature of the second member.

[0044] Figure 3 shows an example of the information used to set the threshold. Figure 3 shows graphs G10 and G20 obtained from gas chromatograph 1 modified for threshold setting. The modification involves adding a temperature sensor (hereinafter also referred to as the "additional sensor") attached to the aluminum block 70A.

[0045] Graph G10 shows the results of controlling the heating device 70H on / off using a temperature sensor 79 and a target temperature (for example, 80°C). (If the measurement result of the temperature sensor 79 is below the target temperature, the output of the heating device 70H is controlled to 100%, and if the measurement result exceeds the target temperature, the heating device 70H is turned off (output is controlled to 0%).) Graph G10 shows the changes in the output of the heating device 70H (%: line L11), the measurement result of the temperature sensor 79 (°C: line L12), and the rate of the measurement result (°C / sec: line L13) as time elapses from the start of heating by the heating device 70H. The vertical axes of lines L11 and L12 are shown on the right. The vertical axis of line L13 is shown on the left.

[0046] Graph G20 shows the results of controlling the heating device 70H on / off using the additional sensor and target temperature described above (if the temperature measured by the additional sensor is below the target temperature, the output of the heating device 70H is controlled to 100%, and if the measurement result exceeds the target temperature, the heating device 70H is turned off (output is controlled to 0%)). Graph G20 shows the changes in the output of the heating device 70H (%: line L21), the measurement result of the temperature sensor 79 (°C: line L22), and the rate of the measurement result (°C / sec: line L23) as time elapsed since the start of heating by the heating device 70H. The vertical axes of lines L21 and L22 are shown on the right. The vertical axis of line L23 is shown on the left.

[0047] In graph G10, line L11 indicates that the output of the heating device 70H was switched off after 14 seconds, following being turned on at 100%. This means that the rise time from the start of heating in the first component is 14 seconds.

[0048] Furthermore, in graph G10, line L11, as indicated by the dashed line, shows that after the output of the heating device 70H is switched off, the measurement result of the temperature sensor 79 rises by 15°C.

[0049] Figure 4 shows the information presented in Figure 3, along with different annotations. In Figure 4, the dashed line indicates the timing when the measurement rate at line L13 in graph G10 reached its maximum value (maximum heating rate (0.3°C / sec)). This dashed line also indicates the same elapsed time in graph G20 as the timing described above.

[0050] At the timing described above, the measurement result from the temperature sensor 79 is approximately 60°C, as shown by line L12, and the temperature measured by the additional sensor is approximately 75°C, as shown by line L22. This means that when the maximum heating rate appears in the measurement result from the temperature sensor 79, there is a temperature difference of 15°C or more between the first and second components.

[0051] Figure 5 shows the information presented in Figure 3, along with different annotations. In Figure 5, the dashed line indicates the timing at which the heating rate reached 0.1°C / sec, as indicated by line L13 in graph G10. This dashed line also indicates the same elapsed time as the above timing in graph G20.

[0052] 0.1°C / sec is an example of a heating rate set based on the maximum heating rate. More specifically, if the heating rate exceeds the maximum heating rate, the temperature difference between the first and second components cannot be determined. Therefore, the temperature between the first and second components can be determined based on the timing at which the heating rate reaches a given value lower than the maximum heating rate. For example, a heating rate of about one-third of the maximum heating rate is used.

[0053] At the timing shown in Figure 5, the temperature sensor 79 measured approximately 46°C, as indicated by line L12, and the temperature measured by the additional sensor was approximately 51°C, as indicated by line L22. This means that when the temperature rise rate measured by the temperature sensor 79 is 0.1°C / sec, the temperature difference between the first and second members is approximately 5°C.

[0054] [Determining the threshold for initiating output reduction control] As explained with reference to Figure 3, the time required for the first component to rise from the start of heating (rise time) is 14 seconds. This means that there is a 14-second delay from the start of heating until the first component reaches the target temperature. Also, as explained with reference to Figure 3, after the output of the heating device 70H is switched off, the measurement result of the temperature sensor 79 rises by 15°C.

[0055] Furthermore, as explained with reference to Figure 4, the maximum value (maximum heating rate) measured by the temperature sensor 79 is 0.3°C / sec, and there is a temperature difference of 15°C or more between the first and second components when the maximum heating rate occurs.

[0056] Furthermore, as explained with reference to Figure 5, when the heating rate is 0.1°C / sec, the temperature difference between the first member and the second member is approximately 5°C.

[0057] From the above, when the heating rate is 0.1°C / sec, even if the above delay (14 seconds) occurs, the temperature rise will be limited to a maximum of 1.4°C. This temperature is smaller than the temperature difference (approximately 5°C) between the first and second components when the heating rate is 0.1°C / sec. Therefore, overshoot in the first component can be avoided by changing the control from basic control to output reduction control, provided that the heating rate measured by the temperature sensor 79 is 0.1°C / sec or higher. In other words, a heating rate of 0.1°C / sec or higher is an example of a condition being met for switching the control of the heating device 70H from basic control to output reduction control. In this sense, "0.1°C / sec" can be an example of a threshold (starting threshold) for switching the control from basic control to output reduction control.

[0058] A temperature rise rate of 0.1°C / sec or higher as measured by the temperature sensor 79 constitutes an example of the temperature of the first component being outside the controllable range (i.e., outside the first range) relative to the temperature of the second component. More specifically, after reaching the maximum temperature rise rate (0.3°C / sec), the temperature rise rate hardly increases, but the difference between the first and second temperatures tends to widen. Unless the temperature rise rate is below the maximum temperature rise rate, the temperature difference cannot be said to be within a controllable range. In this sense, the temperature of the first component should be judged to be outside the controllable range relative to the temperature of the second component, provided that the temperature rise rate as measured by the temperature sensor 79 exceeds the maximum temperature rise rate. In this embodiment, considering individual differences in each component of the gas chromatograph 1, a threshold of 0.1°C, slightly smaller than 0.3°C, is adopted to ensure that the temperature difference is within a reliably controllable range.

[0059] Furthermore, if the above-mentioned additional sensor is provided in the gas chromatograph 1, another example of a starting threshold may be the difference between the direct temperature measurements of the first and second components. More specifically, the control may be switched from basic control to output reduction control on the condition that this temperature difference is greater than or equal to a given value (for example, about 5°C). In this case, the fact that the above-mentioned temperature difference is greater than or equal to the above-mentioned given value is another example of the release condition being met.

[0060] [Determination of the threshold for disabling output reduction control] If the temperature rise rate measured by the temperature sensor 79 is less than 0.1°C / sec, the control is changed from output reduction control to basic control. A temperature rise rate of less than 0.1°C / sec measured by the temperature sensor 79 is an example of a return condition (a condition for returning the control of the heating device 70H from output reduction control to basic control). When the control of the heating device 70H is returned to basic control in response to the fulfillment of the return condition, the output of the heating device 70H can be controlled to stabilize the temperature of the first component near the target temperature at an earlier stage, in situations where the possibility of overshoot occurring in the first component is low.

[0061] A temperature rise rate of less than 0.1°C / sec as measured by the temperature sensor 79 constitutes an example of the temperature of the first component being within a second range relative to the temperature of the second component. In this case, "0.1°C / sec" constitutes an example of a threshold (release threshold) for switching control from output reduction control to basic control.

[0062] The release threshold may be the same value as the starting threshold mentioned above. In this case, the second range means the same range as the first range.

[0063] Furthermore, the release threshold may be slightly larger than the starting threshold. More specifically, to prevent chattering from occurring even if the measured value of the temperature sensor 79 fluctuates instantaneously due to disturbances and / or noise, the release threshold may be set to a value approximately 0.5°C larger than the starting threshold. For example, if the starting threshold is 0.10°C / sec, the release threshold may be 0.15°C / sec.

[0064] Furthermore, if the above-mentioned additional sensor is provided in the gas chromatograph 1, another example of a release threshold may be the difference between the direct temperature measurements of the first and second components. More specifically, the control may be switched from output reduction control to basic control on the condition that these temperature differences are less than a given value (for example, about 5°C). In other words, the fact that these temperature differences are less than a given value is another example of the return condition being met.

[0065] [Process Flow] Figure 6 is a flowchart of the output control process of the heating device 70H for controlling the first conduit 71 containing the filament F to a target temperature. In one implementation example, the process in Figure 6 is performed by the CPU of the control unit 80 executing a given program. In other words, an example of the "controller" in this embodiment is realized by the control unit 80 executing the given program. In one implementation example, the control unit 80 starts the process in Figure 6 in response to being instructed to start temperature control of the first conduit 71. The details of the process will be explained below with reference to Figure 6.

[0066] In step S10, the control unit 80 starts basic control of the heating device 70H. The control in step S10 corresponds to the function of the FB control unit 200 (Figure 2).

[0067] In step S20, the control unit 80 determines whether the above-mentioned "departure condition" has been met. The control unit 80 repeats the control in step S20 until it determines that the above-mentioned "departure condition" has been met (NO in step S20), and when it determines that the above-mentioned "departure condition" has been met (YES in step S20), it proceeds to step S30. The control in step S20 corresponds to the function of the monitoring unit 201 (Figure 2).

[0068] In step S30, the control unit 80 switches the control of the heating device 70H from basic control to output reduction control. The control in step S30 corresponds to the function of the output limiting unit 202 (Figure 2).

[0069] In step S40, the control unit 80 determines whether the above-mentioned "recovery condition" has been met. The control unit 80 repeats the control in step S40 until it determines that the above-mentioned "recovery condition" has been met (NO in step S40), and when it determines that the above-mentioned "recovery condition" has been met (YES in step S40), it returns control to step S10. This returns the control of the heating device 70H to basic control. The control in step S40 corresponds to the function of the monitoring unit 201 (Figure 2).

[0070] When the process shown in Figure 6 is started, the control unit 80 may perform control to set the output of the heating device 70H to 100% before the basic control in step S10. In one implementation example, the control unit 80 may perform control to set the output of the heating device 70H to 100% instead of PID control for a period during which the temperatures of the first member and the second member are considered to be 20°C or more apart, and then, when it determines that such a period has ended, it may perform the heating control in step S10.

[0071] When the temperatures of the first and second components differ by 20°C or more, the proportional term in PID control will be 100% or more. The range in which the proportional term is 100% or less is called the "proportional band." Outside the "proportional band," the output of the heating device 70H is controlled to 100% in order to rapidly raise the temperature of the second component. Furthermore, when the difference between the measurement result of the temperature sensor 79 and the temperature measured by the additional sensor becomes 15°C or more (i.e., when the measurement result of the temperature sensor 79 is 15°C or more below the target temperature), it is considered unlikely that an overshoot will occur even if the output control of the heating device 70H is controlled to its basic level. The above "20°C" is used as an example of a value greater than the above difference.

[0072] This specification describes the control of the heating device for a thermal conductivity detector, specifically focusing on the case where the thermal conductivity detector is mounted on a gas chromatograph. However, the control of the heating device for a thermal conductivity detector described herein is not limited to cases where the thermal conductivity detector is mounted on a gas chromatograph, and can be applied to the control of the heating device for a thermal conductivity detector in any case.

[0073] [Pattern] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following embodiments.

[0074] (Section 1) A thermal conductivity detection unit according to one embodiment comprises a thermal conductivity detector and a controller configured to control the thermal conductivity detector, wherein the thermal conductivity detector includes a first member, a second member having a higher thermal conductivity than the first member, a heating device housed in the second member, and a filament and a temperature sensor housed in the first member, and the controller is configured to control the output of the heating device with an output corresponding to the measurement result of the temperature sensor in basic control, and to control the output of the heating device with an output corresponding to the measurement result in output reduction control when the temperature of the first member is outside a first range with respect to the temperature of the second member, and in output reduction control, the output of the heating device may be controlled with an output reduced from the output corresponding to the measurement result in basic control.

[0075] The thermal conductivity detection unit described in paragraph 1 provides a technique for improving the accuracy of the operation control of the heating device of the thermal conductivity detector.

[0076] (Clause 2) In the thermal conductivity detection unit described in paragraph 1, the controller may determine that the temperature of the first member is outside the first range relative to the temperature of the second member if the temperature rise per unit time in the measurement result is equal to or greater than a predetermined heating rate.

[0077] According to the thermal conductivity detection unit described in paragraph 2, a temperature sensor for measuring the temperature of the second component is not required, and the manufacturing cost of the thermal conductivity detection unit can be reduced.

[0078] (Clause 3) In the thermal conductivity detection unit described in paragraph 1 or 2, the controller may be configured to control the output of the heating device with an output corresponding to the measurement result in the basic control if, after the output reduction control, the temperature of the first member is within a second range relative to the temperature of the second member.

[0079] According to the thermal conductivity detection unit described in Section 3, the operation of the heating device is controlled to bring the filament temperature to the target temperature earlier while suppressing the occurrence of overshoot.

[0080] (Clause 4) In the thermal conductivity detection unit described in Clause 3, the controller may determine that the temperature of the first member is within the second range relative to the temperature of the second member if the difference between the measurement result and the target temperature for controlling the output of the heating device is less than or equal to a predetermined temperature.

[0081] According to the thermal conductivity detection unit described in paragraph 4, a temperature sensor for measuring the temperature of the second component is not required, and the manufacturing cost of the thermal conductivity detection unit can be reduced.

[0082] (Clause 5) In the thermal conductivity detection unit described in any one of Clauses 1 to 4, the basic control may be PID control.

[0083] According to the thermal conductivity detection unit described in Section 5, the operation of the heating device can be controlled with high precision with respect to the target temperature.

[0084] (Clause 6) In the thermal conductivity detection unit described in any one of paragraphs 1 to 5, the output reduction control may include turning off the output of the heating device.

[0085] According to the thermal conductivity detection unit described in Section 6, overshoot in the first component can be more reliably avoided.

[0086] (Clause 7) In the thermal conductivity detection unit described in any one of Clauses 1 to 6, the output reduction control may include calculating a value obtained by subtracting a certain value from the output corresponding to the measurement result in the basic control, as the output of the heating device.

[0087] According to the thermal conductivity detection unit described in Section 7, overshoot in the first component can be avoided, and the temperature of the first component can be stabilized near the target temperature at an early stage.

[0088] (Clause 8) In the thermal conductivity detection unit described in any one of paragraphs 1 to 7, the first member may include stainless steel, and the second member may include aluminum.

[0089] According to the thermal conductivity detection unit described in Section 8, heat from the heating device is easily transferred to other elements, and the temperature near the filament remains stable.

[0090] (Clause 9) A gas chromatograph according to one embodiment comprises a sample vaporization unit that generates a sample gas by vaporizing a sample, a column for separating the components of the sample gas generated by the sample vaporization unit, and a thermal conductivity detection unit as described in any one of Clauses 1 to 8, wherein the thermal conductivity detection unit may detect the thermal conductivity of each component of the sample gas separated by the column.

[0091] According to the gas chromatograph described in paragraph 9, a technique is provided for improving the accuracy of the operational control of the heating device of a thermal conductivity detector.

[0092] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. Furthermore, each technology in the embodiments is intended to be practiced individually or, as far as possible, in combination with other technologies in the embodiments. [Explanation of symbols]

[0093] 1 Gas chromatograph, 10 Gas tank, 20, 50 Flow rate adjustment unit, 30 Sample vaporization unit, 40 Column, 60 Switching valve, 70 Thermal conductivity detector, 70A Aluminum block, 70H Heating device, 70X Cell block, 71 First pipeline, 75, 77 Carrier gas introduction pipeline, 76 Sample introduction pipeline, 78 Exhaust pipeline, 78e Outlet, 79 Temperature sensor, 80 Control unit, 200 FB control unit, 201 Monitoring unit, 202 Output limiting unit, 220 Controlled object, F Filament, G10, G20 Graph, L11, L12, L13, L21, L22, L23 Lines.

Claims

1. Thermal conductivity detector, A controller configured to control the thermal conductivity detector, A thermal conductivity detection unit comprising: The thermal conductivity detector is, The first member and A second member having a higher thermal conductivity than the first member, A heating device housed in the second member, The first member includes a filament and a temperature sensor, The aforementioned controller, In basic control, the output of the heating device is controlled by an output corresponding to the measurement result of the temperature sensor. If the temperature of the first member is outside the first range relative to the temperature of the second member, the output of the heating device is configured to be controlled in the output reduction control to an output corresponding to the measurement result. In the output reduction control described above, the output of the heating device is controlled at an output that is lower than the output corresponding to the measurement result in the basic control, in the thermal conductivity detection unit.

2. The thermal conductivity detection unit according to claim 1, wherein the controller determines that the temperature of the first member is outside the first range relative to the temperature of the second member when the temperature rise per unit time in the measurement result is equal to or greater than a predetermined heating rate.

3. The thermal conductivity detection unit according to claim 1 or 2, wherein the controller is configured to control the output of the heating device with an output corresponding to the measurement result in the basic control when the temperature of the first member is within a second range relative to the temperature of the second member after the output reduction control.

4. The thermal conductivity detection unit according to claim 3, wherein the controller determines that the temperature of the first member is within the second range relative to the temperature of the second member when the difference between the measurement result and the target temperature for controlling the output of the heating device is less than or equal to a predetermined temperature.

5. The thermal conductivity detection unit according to claim 1 or claim 2, wherein the basic control is PID control.

6. The thermal conductivity detection unit according to claim 1 or 2, wherein the output reduction control includes turning off the output of the heating device.

7. The thermal conductivity detection unit according to claim 1 or 2, wherein the output reduction control includes calculating a value obtained by subtracting a certain value from the output corresponding to the measurement result in the basic control, as the output of the heating device.

8. The first member includes stainless steel, The thermal conductivity detection unit according to claim 1, wherein the second member includes aluminum.

9. A sample vaporization unit that generates a sample gas by vaporizing the sample, A column for separating the components of the sample gas generated by the sample vaporization unit, A thermal conductivity detection unit according to claim 1 or claim 2, Equipped with, The thermal conductivity detection unit is a gas chromatograph that detects the thermal conductivity of each component of the sample gas separated by the column.

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