Thermal conductivity detection cell and gas chromatograph

Abstract

A technique for improving the accuracy of operation control of a heating device of a thermal conductivity detector is provided. A controller that controls a thermal conductivity detector is configured to control, in basic control, an output of a heating device of the thermal conductivity detector at an output corresponding to a measurement result of a temperature sensor. However, the controller is configured to control, in output reduction control, the output of the heating device at the output corresponding to the measurement result, in a case where a temperature of a first member that houses a filament and the temperature sensor is outside a first range with respect to a temperature of a second member that houses the heating device. In the output reduction control, the output of the heating device is controlled to be lower than the output corresponding to the measurement result in the basic control.

Description

Technical Field

[0001] This invention relates to improving the accuracy of the operation control of the heating device in a thermal conductivity detector. Background Technology

[0002] Conventionally, as described in, for example, Japanese Patent Application Publication No. 2020-041989 (Patent Document 1), a heating device (heater) is provided in the thermal conductivity detector. As a result, it is possible to minimize the temperature variation of the part containing the filament used for detecting thermal conductivity due to factors other than the composition or concentration of the gas being detected.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-041989 Summary of the Invention The technical problem that the invention aims to solve In conventional thermal conductivity detectors, to reduce manufacturing costs, a general-purpose unit housed within a component with high thermal conductivity is sometimes used as the heating element. In this case, the filament and temperature sensor are housed together within a component with low thermal conductivity. Furthermore, when the heating element is controlled using the temperature detected by the temperature sensor, the component housing the heating element sometimes reaches the target temperature before the detected temperature does. Consequently, when the detected temperature reaches the target temperature, the temperature of the component housing the heating element may exceed the target temperature. Therefore, when controlling the heating element based on the detected temperature, temperature overshoot may occur. This results in a longer time for the temperature of the aforementioned components in the thermal conductivity detector to stabilize during analysis. Therefore, it is desirable to improve the accuracy of the heating element's operation control in the thermal conductivity detector.

[0004] The present invention was conceived in view of the above facts, and its purpose is to provide a technique for improving the accuracy of the operation control of the heating device of a thermal conductivity detector.

[0005] Solution to the above technical problems According to one aspect of the present disclosure, a thermal conductivity detection unit includes a thermal conductivity detector and a controller configured to control the thermal conductivity detector. The thermal conductivity detector includes: a first component; a second component with a thermal conductivity higher than that of the first component; a heating device housed in the second component; and a filament and a temperature sensor housed in the first component. The controller is configured to: in basic control, control the output of the heating device with an output corresponding to the measurement result of the temperature sensor; and in output reduction control, when the temperature of the first component is outside a first range relative to the temperature of the second component, control the output of the heating device with an output corresponding to the measurement result; and in output reduction control, control the output of the heating device to a lower output than the output corresponding to the measurement result in basic control.

[0006] According to one aspect of the present disclosure, a gas chromatograph includes: a sample vaporization section for generating a sample gas by vaporizing a sample; a chromatographic column for separating the components of the sample gas generated by the sample vaporization section; and the aforementioned thermal conductivity detection unit, which detects the thermal conductivity of each component of the sample gas separated by the chromatographic column.

[0007] Invention Effects According to one aspect of this disclosure, a technique is provided for improving the accuracy of motion control of a heating device for a thermal conductivity detector. Attached Figure Description

[0008]

【 Figure 1 [Illustration] is a block diagram showing the structure of a gas chromatograph including a thermal conductivity detection unit in one embodiment.

[0009]

【 Figure 2 The diagram above shows an example of a control block for controlling the operation of a heating device.

[0010]

【 Figure 3 The figure shown is an example of information used for threshold setting.

[0011]

Figure 4

[0012]

Figure 5

[0013] 【 Figure 6 This is a flowchart of the output control process of the heating device 70H used to control the first conduit 71 containing the filament F at the target temperature. Detailed Implementation

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, identical or equivalent parts are given the same reference numerals, and repeated descriptions thereof are omitted.

[0015] [Structure overview and basic operation of a gas chromatograph] Figure 1 This is a block diagram illustrating the structure of a gas chromatograph including a thermal conductivity detection unit in one embodiment. Figure 1 As shown, the gas chromatograph 1 includes a gas tank 10, a flow regulating unit 20, a sample vaporization unit 30, a chromatographic column 40, a flow regulating unit 50, a switching valve 60, a thermal conductivity detector 70, and a control unit 80.

[0016] The gas tank 10 stores a carrier gas for guiding the sample gas to the chromatographic column 40 and the thermal conductivity detector 70. An inert gas, such as helium, is used as the carrier gas.

[0017] The gas tank 10 supplies carrier gas to two flow regulating units 20 and 50 via branch pipelines. One of the flow regulating units 20 supplies carrier gas to the sample vaporization unit 30 at a predetermined flow rate based on the control of the control unit 80.

[0018] 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 through the injector. The internal atmosphere of the vaporization chamber is maintained in a state where the sample can be vaporized. Thus, the sample injected into the vaporization chamber is vaporized within it. The sample vaporization unit 30 mixes the vaporized sample with carrier gas supplied from the flow control unit 20 and simultaneously supplies it to the chromatographic column 40. In the following description, the gaseous components of the sample vaporized in the sample vaporization unit 30 are collectively referred to as sample gas.

[0019] The chromatographic column 40 is housed in a column oven (not shown). Within the chromatographic column 40, the components of the sample gas supplied from the sample vaporization section 30 are separated. The chromatographic column 40 supplies the component-separated sample gas to the sample inlet line 76 of the thermal conductivity detector 70.

[0020] The flow regulating unit 50, under the control of the control unit 80, supplies carrier gas to the switching valve 60 at a predetermined flow rate. The switching valve 60, for example, is a three-way solenoid valve, which is connected to the flow regulating unit 50 and to the two carrier gas inlet lines 75 and 77 (described later) of the thermal conductivity detector 70. The switching valve 60, under the control of the control unit 80, supplies carrier gas from the flow regulating unit 50 to either of the carrier gas inlet lines 75 and 77.

[0021] Furthermore, instead of the switching valve 60, a switching mechanism comprising multiple control valves and branch lines can be used as a structure for supplying carrier gas from the flow regulating unit 50 to either of the two carrier gas inlet lines 75 and 77. For example, the main line is connected to the flow regulating unit 50, and the two branch lines are respectively connected to the carrier gas inlet lines 75 and 77. In addition, two control valves are provided on each of the two branch lines. In this case, by controlling the on / off state of the two control valves, the carrier gas supplied from the flow regulating unit 50 can be selectively supplied to either of the two carrier gas inlet lines 75 and 77 of the thermal conductivity detector 70.

[0022] The thermal conductivity detector 70 of this embodiment includes a first conduit 71, a second conduit 72, a third conduit 73, a fourth conduit 74, carrier gas inlet conduits 75 and 77, a sample inlet conduit 76, and an exhaust conduit 78, all extending in a straight line. These conduits are formed, for example, by metal piping. Furthermore, among the multiple conduits of the thermal conductivity detector 70, the first to fourth conduits 71 to 74 are housed together with the heating device 70H within a cell block 70X. The cell block 70X is manufactured by machining and joining multiple plate-shaped metal components. Within the cell block 70X, the heating device 70H is housed within an aluminum block 70A.

[0023] The first conduit 71 and the second conduit 72 are configured to face each other and extend parallel to each other. The third conduit 73 is configured to connect one end of the first conduit 71 and one end of the second conduit 72, and the fourth conduit 74 is configured to connect the other end of the first conduit 71 and the other end of the second conduit 72. A filament F is housed inside the first conduit 71. On the other hand, no filament F is housed inside the second conduit 72. Furthermore, a temperature sensor 79 is housed inside the first conduit 71.

[0024] In the third pipeline 73, a first gas inlet 73a, a second gas inlet 73b, and a third gas inlet 73c are arranged in this order. Among the first to third gas inlets 73a to 73c, the first gas inlet 73a is closest to the first pipeline 71, and the third gas inlet 73c is closest to the third pipeline 73.

[0025] The carrier gas inlet conduit 75 is configured to extend from the first gas inlet 73a to the outside of the cell block 70X. The sample inlet conduit 76 is configured to extend from the second gas inlet 73b to the outside of the cell block 70X. The carrier gas inlet conduit 77 is configured to extend from the third gas inlet 73c to the outside of the cell block 70X.

[0026] A gas outlet 74a is provided in the fourth conduit 74. An exhaust conduit 78 is configured to extend from the gas outlet 74a to the outside of the pool block 70X. A through hole is formed in the gas outlet 74a. Thus, the internal space of the fourth conduit 74 communicates with the internal space of the exhaust conduit 78. The exhaust conduit 78 has an outlet 78e on the outside of the pool block 70X.

[0027] The heating device 70H is controlled by the control unit 80 to maintain the space within the cell block 70X at a temperature equivalent to that in the vaporization chamber of the sample vaporization unit 30 or in the column oven housing the chromatographic column 40. For example, a cylindrical heater is used as the heating device 70H.

[0028] The control unit 80 is, for example, composed of 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. Furthermore, the control unit 80 in this example also includes a drive circuit for driving the filament F and a detection circuit for detecting changes in the resistance of the filament F.

[0029] The aforementioned switching valve 60 switches between a first state, which supplies carrier gas to one side of the carrier gas inlet line 75, and a second state, which supplies carrier gas to the other side of the carrier gas inlet line 77, at a predetermined period (e.g., about 100 msec).

[0030] In this situation, 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 closer to the first gas inlet 73a than the second gas inlet 73b becomes higher. As a result, the sample gas supplied to the sample inlet conduit 76 flows through the second conduit 72 together with a portion of the carrier gas introduced from the first gas inlet 73a. Additionally, the remaining carrier gas introduced from the first gas inlet 73a flows through the first conduit 71 as a reference gas.

[0031] 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 closer to the third gas inlet 73c than the second gas inlet 73b increases. As a result, the sample gas supplied to the sample inlet conduit 76 flows through the first conduit 71 together with a portion of the carrier gas introduced from the third gas inlet 73c. ​​Additionally, the remaining carrier gas introduced from the third gas inlet 73c flows through the second conduit 72.

[0032] Therefore, in the control unit 80, the thermal conductivity of the sample gas is measured based on the change in the resistance value of the filament F between the reference gas passing around the filament F and the sample gas passing around the filament F.

[0033] [Overview of Heating Device Operation Control] Figure 2This is a diagram illustrating an example of a control block for controlling the operation of a heating device. Figure 2 The example illustrates feedback (FB) control using the difference (error) between the measurement result of temperature sensor 79 (the temperature measured by temperature sensor 79) and the target temperature. Figure 2 The diagram shows the FB control unit 200, monitoring unit 201, output limiting unit 202, and controlled object 220. Controlled object 220 refers to... Figure 1 The heating device 70H.

[0034] Basically, the FB control unit 200 controls the output of the controlled object 220 based on basic control. In basic control, the output (value) of the controlled object 220 is set based on the aforementioned error, and the controlled object 220 is controlled to achieve the set output.

[0035] exist Figure 2 In the example, the monitoring unit 201 determines whether the temperature of the component housing the filament F and the temperature sensor 79 (first pipe 71: first component) is outside the first range relative to the temperature of the component housing the heating device (aluminum block 70A: second component), and determines whether it is within the second range.

[0036] Whether the temperature of the first component is outside the first range relative to the temperature of the second component, and whether the temperature of the first component is within the second range relative to the temperature of the second component, can be determined either by direct measurement of the temperatures of the two components or indirectly by other methods.

[0037] When the monitoring unit 201 determines that the temperature of the first component is outside a 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 used to reduce the output implemented by the controlled object 220 to a level lower than the output set by the FB control unit 200. The output controlled by the output limiting unit 202 only needs to be lower than the output set by the FB control unit 200; it can be the value obtained by subtracting a fixed value from the output set by the FB control unit 200, or it can be "zero".

[0038] The output limiting unit 202 responds to the instruction from the monitoring unit 201 and performs output reduction control. As a result, in the output reduction control, the output that is instructed to be realized by the controlled object 220 will be lower than the output set by the FB control unit 200.

[0039] Subsequently, when the monitoring unit 201 determines that the temperature of the first component is within a 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.

[0040] In this embodiment, an example of "basic control" is PID (Proportional Integral Differential) control. Furthermore, basic control can be any control that utilizes the measurement results from the temperature sensor 79, or it can be control that switches the output of the controlled object 220 on / off based on the measurement results, or control that sets the output of the controlled object 220 as a linear function of the measurement results.

[0041] In this embodiment, the controlled object 220 (heating device) is housed in a component with relatively high thermal conductivity. Therefore, heat from the heating device can be efficiently transferred to other elements in the thermal conductivity detector. Furthermore, aluminum (aluminum block) is shown as an example of a component with relatively high thermal conductivity in this specification, but it is not limited to this; other types of components such as copper may also be used.

[0042] Furthermore, the filament is housed within a component with relatively low thermal conductivity. This allows for temperature stability of the filament and its surrounding area. While stainless steel is shown as an example of a component with relatively low thermal conductivity in this specification, it is not limited to this and other types of components, such as titanium, may also be used.

[0043] Furthermore, the temperature sensor is housed in the same component that houses the filament, and the operation control of the heating device is implemented based on the measurement results of this temperature sensor and in accordance with basic control. Therefore, the temperature around the filament can be more reliably reflected in the temperature sensor's measurement results, and more reliably reflected in the operation control of the heating device.

[0044] Furthermore, in the operation control of the heating device, when the temperature of the heating device continues to rise and the temperature of the component housing the heating device (the second component) differs significantly from the temperature of the component housing the filament and the temperature sensor (the first component) (when the temperature difference between the two is outside the first range), the output of the heating device will be temporarily adjusted to be lower than the output corresponding to the measurement result in the basic control. This suppresses the occurrence of overshoot.

[0045] 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) (when the temperature difference between the two is within a second range), the output control of the heating device returns to the basic control described above. Thus, the heating device is controlled to ensure that the filament temperature reaches the target temperature earlier.

[0046] In summary, according to this disclosure, the operation of the heating device is controlled to suppress overshoot while causing the filament temperature to reach the target temperature earlier.

[0047] [Prerequisites for setting the threshold] In this embodiment, whether the temperature of the first component (first pipe 71) is outside the first range relative to the temperature of the second component (aluminum block 70A), and whether the temperature of the first component is within the second range relative to the temperature of the second component, is determined using threshold values.

[0048] Figure 3 This is a diagram illustrating an example of information used for threshold setting. Figure 3 Figures G10 and G20 are shown in the gas chromatograph 1 modified for setting thresholds. The modification refers to the addition of a temperature sensor (hereinafter also referred to as "additional sensor") mounted on the aluminum block 70A.

[0049] Chart G10 illustrates the results of controlling the heating device 70H on / off using temperature sensor 79 and a target temperature (80°C in an example). (If the temperature sensor 79's measurement is below the target temperature, the output of heating device 70H is controlled at 100%; if the measurement exceeds the target temperature, heating device 70H is turned off (output is 0%).) Chart G10 shows the changes in the output of heating device 70H (%: line L11), the measurement result of temperature sensor 79 (°C: line L12), and the rate of measurement (°C / sec: line L13) as time elapses since heating begins. The vertical axes of lines L11 and L12 are shown on the right. The vertical axis of line L13 is shown on the left.

[0050] Chart G20 illustrates the results of controlling the heating device 70H on / off using the aforementioned additional sensor and target temperature (if the temperature measured by the additional sensor is below the target temperature, the output of the heating device 70H is controlled to 100%; if the measurement result exceeds the target temperature, the heating device 70H is turned off (output is 0%)). Chart 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 measurement (°C / sec: line L23) as time elapses from 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.

[0051] In diagram G10, line L11 shows that after the output of heating device 70H is turned on at 100%, the output is switched off after 14 seconds. Thus, the time from the start of heating to temperature stabilization in the first component is 14 seconds.

[0052] Furthermore, in Figure G10, line L12, as shown by the dashed line, indicates that the temperature sensor 79's measurement increased by 15°C after the output of the heating device 70H was switched off.

[0053] Figure 4 Is with Figure 3 Different markings are used to indicate Figure 3 The diagram shows the information. Figure 4 In the diagram, the dashed line indicates the moment when the rate of measurement in line L13 of graph G10 reaches its maximum value (maximum heating rate (0.3℃ / sec)). This dashed line also shows the elapsed time at the same moment in graph G20.

[0054] At the aforementioned moment, the temperature sensor 79 measured approximately 60°C, as shown in line L12, while the temperature measured by the additional sensor, as shown in line L22, was approximately 75°C. Therefore, it can be concluded that when the temperature sensor 79 measures the maximum heating rate, there is a temperature difference of more than 15°C between the first and second components.

[0055] Figure 5 Is with Figure 3 Different markings are used to indicate Figure 3 The diagram shows the information. Figure 5 In the diagram, the dashed line indicates the moment when the heating rate reaches 0.1°C / sec in line L13 of graph G10. This dashed line also indicates the elapsed time at the same moment in graph G20.

[0056] 0.1℃ / 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 moment when the heating rate reaches a given value below the maximum heating rate. For example, a heating rate of approximately one-third of the maximum heating rate can be used as the heating rate employed.

[0057] exist Figure 5 At the indicated time, the temperature sensor 79 measures approximately 46°C as shown by line L12, while the temperature measured by the additional sensor is approximately 51°C as shown by line L22. Therefore, when the heating rate in the temperature sensor 79's measurement is 0.1°C / sec, the temperature difference between the first and second components is approximately 5°C.

[0058] [Determination of the threshold for initiating control by reducing output] For reference Figure 3 As explained, the time required for the first component to reach a stable temperature from the start of heating (stabilization time) is 14 seconds. Therefore, there is a 14-second delay from the start of heating until the first component reaches the target temperature. Additionally, as referred to... Figure 3 As explained, after the output of the heating device 70H was switched off, the measurement result of the temperature sensor 79 increased by 15°C.

[0059] Additionally, as referenced Figure 4 As explained, the maximum value (maximum heating rate) in the measurement results of temperature sensor 79 is 0.3℃ / sec, and when the maximum heating rate occurs, there is a temperature difference of more than 15℃ between the first component and the second component.

[0060] Additionally, as referenced Figure 5 As explained, when the heating rate is 0.1℃ / sec, the temperature difference between the first component and the second component is approximately 5℃.

[0061] In summary, when the heating rate is 0.1℃ / sec, even with the aforementioned delay (14 seconds), the temperature rise can be suppressed to a maximum of 1.4℃. This temperature is less than the temperature difference between the first and second components (approximately 5℃) when the heating rate is 0.1℃ / sec. Therefore, by changing the control from basic control to output reduction control based on the heating rate measured by temperature sensor 79 being 0.1℃ / sec or higher, overshoot of the first component can be avoided. In other words, a heating rate of 0.1℃ / sec or higher is an example of a disengagement condition (a condition used to disengage the control of the heating device 70H from basic control and transfer it to output reduction control). In this sense, "0.1℃ / sec" can be considered an example of a threshold (start-up threshold) used to switch the control from basic control to output reduction control.

[0062] The heating rate measured by temperature sensor 79 is above 0.1°C / sec, constituting an example where the temperature of the first component is outside the controllable range (i.e., outside the first range) relative to the temperature of the second component. More specifically, after reaching the maximum heating rate (0.3°C / sec), the heating rate hardly increases, but the difference between the first and second temperatures tends to widen. If the heating rate is not lower than the maximum heating rate, it cannot be said that the temperature difference is within the controllable range. In this sense, the condition for determining that the temperature of the first component is outside the controllable range relative to the temperature of the second component should be that the heating rate measured by temperature sensor 79 exceeds the maximum heating rate. In this embodiment, considering individual differences among the components of gas chromatograph 1, a threshold of 0.1°C / sec, slightly smaller than 0.3°C / sec, is used as the threshold to reliably determine that the temperature difference is within the controllable range.

[0063] Furthermore, when the aforementioned additional sensor is installed in the gas chromatograph 1, as another example of a start-up threshold, the difference between the direct measurement results of the temperatures of the first and second components can also be used. More specifically, the control can be switched from basic control to output reduction control when these temperature differences are above a given value (e.g., around 5°C). In this case, the aforementioned temperature difference being above the given value is another example of a condition being deviated from being met.

[0064] [The output reduces the threshold used to determine the release of control] If the heating rate measured by temperature sensor 79 is less than 0.1°C / sec, the control is changed from output reduction control to basic control. The heating rate measured by temperature sensor 79 being less than 0.1°C / sec is an example of a recovery condition (a condition used to restore the control of heating device 70H from output reduction control to basic control). By restoring the control of heating device 70H to basic control based on the fulfillment of the recovery condition, the output of heating device 70H can be controlled earlier when the possibility of overshoot in the first component is low, thereby stabilizing the temperature of the first component near the target temperature.

[0065] The temperature rise rate measured by temperature sensor 79 is less than 0.1℃ / sec, which constitutes an example where the temperature of the first component is within a second range relative to the temperature of the second component. In this case, "0.1℃ / sec" constitutes an example of a threshold (release threshold) used to switch the control from output reduction control to basic control.

[0066] The threshold for deactivation can be the same as the threshold for activation described above. In this case, the second range refers to the same range as the first range.

[0067] Furthermore, the release threshold can be slightly larger than the start threshold. More specifically, to prevent jitter even when the measured value of the temperature sensor 79 changes instantaneously due to disturbances and / or noise, the release threshold can be set to a value approximately 0.05°C / sec larger than the start threshold. For example, if the start threshold is 0.10°C / sec, the release threshold could be 0.15°C / sec.

[0068] Furthermore, when the aforementioned additional sensor is installed in the gas chromatograph 1, as another example of the threshold for release, the difference between the direct measurement results of the temperatures of the first and second components can also be used. More specifically, the control can be switched from output reduction control to basic control when these temperature differences are less than a given value (e.g., around 5°C). In other words, these temperature differences being less than a given value is another example of a recovery condition being met.

[0069] [Processing Flow] Figure 6 This is a flowchart of the output control process of the heating device 70H, used to control the first conduit 71 housing the filament F at a target temperature. In one implementation example... Figure 6 The processing is implemented by the CPU of the control unit 80 executing a given program. In other words, the control unit 80, by executing this given program, implements an example of the "controller" in this embodiment. In one implementation example, the control unit 80 starts when instructed to begin temperature control of the first pipeline 71. Figure 6 The following refers to the processing. Figure 6 Explain the content being processed.

[0070] In step S10, the control unit 80 begins basic control of the heating device 70H. The control in step S10 is equivalent to that of the FB control unit 200 (…). Figure 2 () function.

[0071] In step S20, the control unit 80 determines whether the aforementioned "detachment condition" is met. The control unit 80 repeats the control in step S20 until it determines that the aforementioned "detachment condition" is met (in step S20, it is "No"). When it determines that the aforementioned "detachment condition" is met (in step S20, it is "Yes"), the control proceeds to step S30. The control in step S20 is equivalent to the monitoring unit 201 (…). Figure 2 () function.

[0072] 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 is equivalent to the output limiting unit 202 ( Figure 2 () function.

[0073] In step S40, the control unit 80 determines whether the aforementioned "recovery condition" is met. The control unit 80 repeats the control in step S40 until it determines that the aforementioned "recovery condition" is met (in step S40, it is "No"). When it determines that the aforementioned "recovery condition" is met (in step S40, it is "Yes"), the control returns to step S10. Thus, the control of the heating device 70H returns to basic control. The control in step S40 is equivalent to the monitoring unit 201 ( Figure 2 () function.

[0074] At the beginning Figure 6During the processing, the control unit 80 may also implement 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 not perform PID control during a period when the temperature difference between the first component and the second component is greater than 20°C, but instead implement control to set the output of the heating device 70H to 100%. After determining that the period has ended, the heating control in step S10 will then be implemented.

[0075] When the temperature difference between the first and second components exceeds 20°C, the proportional term in the PID control will be 100% or higher. The range where the proportional term is below 100% is called the "proportional band." Outside the "proportional band," the output of the heating device 70H is controlled to 100% to rapidly heat the second component. Furthermore, when the temperature difference between the measurement result of temperature sensor 79 and the temperature measured by the additional sensor reaches 15°C or higher (i.e., when the measurement result of temperature sensor 79 is 15°C or higher lower than the target temperature), the possibility of overshoot is considered low even when the output of the heating device 70H is basically controlled. The aforementioned "20°C" is used as an example of a value exceeding the aforementioned difference.

[0076] This specification describes the control of the heating device for a thermal conductivity detector when the detector is mounted in a gas chromatograph. However, the control of the heating device for a thermal conductivity detector described in this specification is not limited to the case where the thermal conductivity detector is mounted in a gas chromatograph, and can be applied to the control of the heating device for a thermal conductivity detector in any situation.

[0077] [Way] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following approaches.

[0078] (First item) A thermal conductivity detection unit is provided, comprising a thermal conductivity detector and a controller configured to control the thermal conductivity detector, wherein the thermal conductivity detector includes: a first component; a second component with a thermal conductivity higher than that of the first component; a heating device housed in the second component; and a filament and a temperature sensor housed in the first component, the controller being configured to: in basic control, control the output of the heating device with an output corresponding to a measurement result of the temperature sensor; and, in output reduction control, control the output of the heating device with an output corresponding to the measurement result when the temperature of the first component is outside a first range relative to the temperature of the second component; in the output reduction control, the output of the heating device can be controlled to be a lower output than the output corresponding to the measurement result in the basic control.

[0079] According to the thermal conductivity detection unit described in the first item, a technique is provided for improving the accuracy of the motion control of the heating device of the thermal conductivity detector.

[0080] (Second item) In the thermal conductivity detection unit described in the first item, the controller can determine that the temperature of the first component is outside the first range relative to the temperature of the second component if the temperature rise value per unit time in the measurement result is above the preset heating rate.

[0081] According to the thermal conductivity detection unit described in the second item, a temperature sensor for measuring the temperature of the second component is not required, thereby reducing the manufacturing cost of the thermal conductivity detection unit.

[0082] (Third item) In the thermal conductivity detection unit described in the first or second item, the controller may be configured to control the output of the heating device in the basic control with an output corresponding to the measurement result, after the output reduction control, when the temperature of the first component is within a second range relative to the temperature of the second component.

[0083] According to the thermal conductivity detection unit described in the third item, the operation of the heating device is controlled to suppress overshoot while making the filament temperature reach the target temperature earlier.

[0084] (Fourth item) In the thermal conductivity detection unit described in the third item, the controller can determine that the temperature of the first component is within the second range relative to the temperature of the second component if the difference between the measurement result and the target temperature in the output control of the heating device is below a preset temperature.

[0085] According to the thermal conductivity detection unit described in the fourth item, a temperature sensor for measuring the temperature of the second component is not required, thereby reducing the manufacturing cost of the thermal conductivity detection unit.

[0086] (Fifth item) In any one of the first to fourth items, the basic control in the thermal conductivity detection unit may be PID control.

[0087] According to the thermal conductivity detection unit described in item 5, the operation of the heating device can be controlled with high precision at the target temperature.

[0088] (Sixth item) In any one of the first to fifth items of the thermal conductivity detection unit, the output reduction control may include turning off the output of the heating device.

[0089] The thermal conductivity detection unit described in item six can more reliably prevent overshoot of the first component.

[0090] (Seventh item) In any one of the first to sixth items of the thermal conductivity detection unit, the output reduction control may include: calculating, as the output of the heating device, a value after subtracting a fixed value from the output corresponding to the measurement result in the basic control.

[0091] According to the thermal conductivity detection unit described in item 7, overshoot of the first component can be avoided, and the temperature of the first component can be stabilized near the target temperature earlier.

[0092] (Eighth item) In any one of the first to seventh items, the first component may comprise stainless steel and the second component may comprise aluminum.

[0093] According to the thermal conductivity detection unit described in item 8, heat from the heating device is easily transferred to other components, and the temperature near the filament is stable.

[0094] (Ninth item) A gas chromatograph according to an embodiment includes: a sample vaporization section for generating a sample gas by vaporizing a sample; a chromatographic column for separating the components of the sample gas generated by the sample vaporization section; and a thermal conductivity detection unit as described in any one of the first to eighth items, the thermal conductivity detection unit being capable of detecting the thermal conductivity of each component of the sample gas separated by the chromatographic column.

[0095] According to the gas chromatograph described in the ninth item, a technique is provided for improving the accuracy of the operation control of the heating device of a thermal conductivity detector.

[0096] It should be considered that the embodiments disclosed herein are exemplary in all respects and not restrictive. The scope of this disclosure is not shown by the description of the embodiments above, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Furthermore, it is intended that the techniques in the embodiments can be implemented individually or in combination with other techniques in the embodiments as needed.

[0097] Explanation of reference numerals in the attached figures 1. Gas Chromatograph 10 gas cylinders 20, 50 Flow Regulation Section 30 Sample vaporization section 40 chromatographic column 60 Switching valve 70 Thermal conductivity detector 70A aluminum block 70H heating device 70X Pool Block 71 First Pipeline 75, 77 Carrier gas inlet pipes 76 Sample introduction tubing 78 Exhaust pipe 78e discharge outlet 79 Temperature Sensor 80 Control Department 200 FB Control Department 201 Surveillance Department 202 Output Limiting Section 220 Controlled Object F filament G10 and G20 charts Lines L11, L12, L13, L21, L22, and L23.

Claims

1. A thermal conductivity detection unit, comprising: Thermal conductivity detector; as well as A controller configured to control the thermal conductivity detector. in, The thermal conductivity detector includes: First component; A second component with higher thermal conductivity than the first component; Heating device housed in the second component; and The filament and temperature sensor housed in the first component The controller is configured to: In basic control, the output of the heating device is controlled by the output corresponding to the measurement result of the temperature sensor. Furthermore, when the temperature of the first component is outside the first range relative to the temperature of the second component, the output of the heating device is controlled in the output reduction control to correspond to the measurement result. In the output reduction control, the output of the heating device is controlled to be lower than the output corresponding to the measurement result in the basic control.

2. The thermal conductivity detection unit according to claim 1, wherein, If the temperature rise per unit time in the measurement result is above the preset heating rate, the controller determines that the temperature of the first component is outside the first range relative to the temperature of the second component.

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

4. The thermal conductivity detection unit according to claim 3, wherein, If the difference between the measurement result and the target temperature in the output control of the heating device is below a preset temperature, the controller determines that the temperature of the first component is within the second range relative to the temperature of the second component.

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

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

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

8. The thermal conductivity detection unit according to claim 1, wherein, The first component is made of stainless steel. The second component contains aluminum.

9. A gas chromatograph, comprising: A sample vaporization section that generates sample gas by vaporizing the sample; A chromatographic column for separating the components of the sample gas generated by the sample vaporization section; and The thermal conductivity detection unit according to claim 1 or claim 2, in, The thermal conductivity detection unit detects the thermal conductivity of the sample gas containing each component separated by the chromatographic column.

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