JP2014163731A - Constant temperature bath for chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant temperature bath including a housing provided in a chromatograph, a heater warming air in the housing, and a fan circulating the air in the housing, which can continue operation, while preventing the heater from being overheated.SOLUTION: A temperature regulator controlling air temperature in the housing includes a first temperature converter connected to a first temperature sensor and outputting a value indicating the air temperature, a second temperature converter connected to a second temperature sensor and outputting the value indicating heater temperature, a first control circuit using the air temperature in the housing outputted by the first temperature converter as a controlled variable, the target temperature of the air in the housing as a target value, and the target temperature of the heater as a manipulated variable, and a second control circuit using the heater temperature outputted by the second temperature converter as the controlled variable, the target temperature of the heater outputted from a limiting circuit as the target value, and the value indicating electric power supplied to the heater as the manipulated variable.

Description

  The present invention relates to a thermostatic chamber for controlling the temperature of a mobile phase supply unit, a sample introduction unit, a separation column, a detection unit and the like provided in a chromatograph.

  Among the chromatographs, the liquid chromatograph includes an eluent supply means, a sample introduction means, a separation column, a detection means, a waste liquid container, and a flow path connecting them. When the sample is introduced upstream of the separation column by the sample introduction means in order to analyze the components contained in the sample, the sample is introduced into the separation column by the eluent supplied from the eluent supply means. The liquid chromatograph uses the fact that the time to pass through the separation column differs for each component in the sample, and the detection means for separating the component contained in the sample and providing the component eluted from the separation column downstream of the separation column After detection, discard the eluate in a waste container. Note that the eluate can be collected in a plurality of containers without being discarded in a waste liquid container, or discarded in a waste outlet.

  In the analysis by liquid chromatography, the temperature of the sample introduction means and separation column can be increased for the purpose of improving the component separation ability in the sample by the separation column and improving the solubility of the component in the sample. Done. In addition, since the eluent supply stability by the eluent supply means, the peak retention time by the separation column, the signal baseline by the detection means, and the like depend on the temperature, the temperature is adjusted as necessary. Therefore, the eluent supply means, the sample introduction means, the separation column, and the detection means are stored individually or in a plurality of means in a constant temperature bath and held at a constant temperature (heated as necessary).

  A constant temperature bath that maintains at least one of the mobile phase supply means, sample introduction means, separation column (separation means), and detection means provided in the chromatograph is usually one of the above means. A housing for housing, a heater for heating the air in the housing, and a fan for circulating the air in the housing; and circulating the air heated by the heater through the fan The temperature inside the casing is kept constant.

  In the above-mentioned thermostatic chamber, the air temperature in the housing is measured (control amount), and the heat generation amount of the heater is controlled so that the air temperature becomes a predetermined temperature (target value) (when an electric heater is used as the heater) Controls the power supplied to the heater. As a method of controlling the amount of heat generated when an electric heater is used as the heater, normally the power proportional to the difference between the target value and the controlled variable (proportional term) and the integral value over the time of the difference between the target value and the controlled variable are used. PI control for supplying proportional power (integral term) to the electric heater, integral power (proportional term) proportional to the difference between the target value and the controlled variable, and the integral value for the time between the target value and the controlled variable ( In addition to the power proportional to the integral term), PID control is used in which power (differential term) proportional to the rate of change of the control amount with respect to time is supplied to the electric heater. In PI control and PID control, the integral term causes overshoot (overshoot) after the temperature adjustment starts and reaches the target temperature. In many cases, the controlled variable reaches a temperature near the target value. It is reset when

  In the above-described air circulation type thermostat, since the thermal resistance between the heater and the air is large, there is a problem that the heater temperature is likely to rise due to the heater heating. In particular, at the start of temperature control, in most cases, the maximum amount of heat is generated, so that the difference between the temperature of the heater and the temperature of the air in the cabinet increases, and the heater may overheat.

  Accordingly, an object of the present invention is to provide a chromatograph provided with a mobile phase supply means, a sample introduction means, a separation means, and a detection means, and a casing that houses any one or more of the means, and the casing. In a thermostatic chamber that regulates the temperature of any one or more of the above-mentioned means, including a heater that heats the air in the body and a fan that circulates the air in the housing, operation can be continued without overheating the heater. It is to provide a constant temperature bath.

  The present invention made in view of the above problems includes the following inventions.

According to a first aspect of the present invention, there is provided a mobile phase supply means, a sample introduction means, a separation means, and a casing that houses any one or more of the means provided in a chromatograph provided with a detection means, An electric heater for supplying heat to the air in the housing, a first temperature sensor for detecting the air temperature in the housing, a second temperature sensor for detecting the temperature of the heater, and controlling the air temperature in the housing A thermostat that regulates the temperature of any one or more of the means, and a temperature regulator that includes a temperature regulator and a fan that circulates air in the housing.
A first temperature converter connected to the first temperature sensor and outputting a value indicating the air temperature;
A second temperature converter connected to the second temperature sensor and outputting a value indicating the heater temperature;
A first control circuit, wherein the air temperature in the housing output by the first temperature converter is a control amount, the target temperature of the air in the housing is a target value, and the target temperature of the heater is an operation amount;
A second control circuit, wherein the heater temperature output from the second temperature converter is a control amount, the target temperature of the heater is a target value, and a value indicating the power to be given to the heater is an operation amount;
It is the said thermostat which had.

  The second aspect of the present invention further includes a limiting circuit for limiting the target temperature of the heater output from the first control circuit to the temperature regulator to a predetermined value or less, and the target value in the second control circuit is It is the thermostat according to the first aspect, which is a target temperature of the heater restricted by the restriction circuit.

In the third aspect of the present invention, the first control circuit is
The PI temperature output from the first temperature converter is a control amount, the target temperature of the air in the housing is a target value, and the difference between the target temperature of the heater and the current heater temperature is an operation amount. A control circuit or a PID control circuit;
An adder circuit for calculating a target temperature of the heater from the sum of the operation amount of the PI control circuit or the PID control circuit and the heater temperature output from the second temperature converter;
It is a thermostat as described in said 1st or 2nd aspect which is a circuit which has.

  Further, the fourth aspect of the present invention is the air temperature in the casing output from the first temperature converter, the heater temperature output from the second temperature converter, the target temperature of the air in the casing, the target temperature of the heater, the heater The constant temperature bath according to any one of the first to third aspects, further comprising display means for displaying any one or more of a value indicating the power applied to the temperature or a difference between these temperatures.

  Hereinafter, the present invention will be described in detail.

  The constant temperature bath of the present invention is a chromatograph for maintaining (temperature controlling) one or more of mobile phase supply means, sample introduction means, separation means (separation column), and detection means at a constant temperature. Provided.

  As the heater provided in the thermostat for the chromatograph, an electric heater that directly transfers heat to the air in contact with the heater is often used. The electric heater can control the amount of heat generated by the amount of electric power applied. Electric heaters include heaters in which elongated heating wires are wound in a spiral shape or a spiral shape, heaters sealed in tubes of metal, glass, ceramics, such as stainless steel tubes, and semiconductor elements such as power transistors There are known heaters that utilize the heat generated by these, and PTC heaters made of semiconductor ceramics, but any heater may be used. Of the electric heaters described above, when using a heater sealed in a stainless steel cylinder, providing fins on the outside increases the amount of air that contacts the heater, which improves heat transfer to the air inside the housing. ,preferable. If a power transistor is used, it may be attached to a heat sink or the like. One or more electric heaters may be provided in the thermostatic chamber.

  The thermostat of the present invention has a first temperature sensor that detects the air temperature in the housing and a second temperature sensor that detects the temperature of the electric heater. Of these, the first temperature sensor changes the air temperature depending on the position in the housing, so the temperature of each means (for example, mobile phase supply means such as a liquid feed pump or separation column) housed in the housing, and the sensor It is preferable to provide it at a position where the difference from the air temperature at the place of installation is small and the wind is well. Examples of the temperature sensor that can be used in the first temperature sensor include a platinum resistance thermometer, a thermocouple, a thermistor, and the like, and may be appropriately selected according to the temperature range to be used. Since the first temperature sensor measures the air temperature, it is preferable to use a small sensor with good time response. The material used for covering the lead wire of the first temperature sensor may be appropriately selected from vinyl chloride, polyethylene, fluororesin, glass fiber, ceramic, etc. according to the temperature range to be used. As with the first temperature sensor, the type of the temperature sensor used in the second temperature sensor may be appropriately selected according to the expected maximum temperature of the heater. An excellent sensor, such as a platinum resistance thermometer or a thermocouple, is more preferred. The material used for covering the lead wire of the second temperature sensor is more preferably glass or ceramic having excellent heat resistance when the heater is at a high temperature.

  The second temperature sensor may be brought into thermal contact with a portion that reflects the heater temperature. If it is difficult to make the temperature sensor adhere to the heater surface, for example, there is a method of making a hole in the heater and inserting the temperature sensor into the hole. Furthermore, in a heater in which a heating wire is enclosed in a stainless steel tube, the temperature sensor may be enclosed together with the heating wire. In addition, when the heat of the electric heater is quickly transmitted to the heat sink, the second temperature sensor may be provided on the heat sink. When using a plurality of electric heaters, it is preferable to provide a second temperature sensor for each heater. However, if the plurality of heaters are installed so that the temperature difference between the heaters does not increase, one heater is provided for each heater. Only two temperature sensors may be provided. Moreover, it is good also as an aspect which provided two or more 2nd temperature sensors with respect to one heater to be used. When providing two or more 2nd temperature sensors, it is good also considering the average value of the value (temperature) detected by each sensor as the value (temperature) detected by the 2nd temperature sensor.

  The temperature converter provided in the thermostat of the present invention can be selected from known temperature converters according to the type of temperature sensor used. When a platinum resistance thermometer or thermistor is used as a temperature sensor, it is usually incorporated into one side of a Wheatstone bridge connected to a constant current power source or a constant voltage power source, and a temperature signal is obtained by amplifying the potential difference between the two midpoints. If the non-linearity is large, a correction circuit may be further used. When using a thermocouple as the temperature sensor, provide a temperature measuring contact and a cold junction (reference contact) that detect the temperature, and keep the cold junction at a predetermined constant temperature, for example, the triple point temperature of water. What is necessary is just to amplify the potential difference between the lead wires consisting of. Instead of keeping the cold junction at a constant temperature, the temperature of the cold junction may be measured to compensate for the potential difference.

Among the temperature regulators provided in the thermostat of the present invention, the first control circuit uses the air temperature in the housing output from the first temperature converter as a controlled variable, the target temperature of the air in the housing as a target value, This is a circuit using the target temperature of the heater as an operation amount. As a specific example of the first control circuit,
A control circuit having a circuit for performing PI control or PID control using the control amount and the target value as input values and the operation amount as an output value;
A circuit for performing PI control or PID control using the control amount and the target value as input values, and outputting a value indicating the difference between the target temperature of the electric heater and the current heater temperature, and the output of the circuit and the first A control circuit having a heater temperature output from the two-temperature converter as an input value and an addition circuit having the operation amount as an output value;
Can be given. In the above aspect, control parameters such as the proportional gain (or proportional width), integral gain (or integral time), and derivative gain (or derivative time) of PI control or PID control are appropriately determined so that the air temperature is stabilized. That's fine.

  Among the temperature regulators provided in the thermostat of the present invention, the second control circuit uses the heater temperature output from the second temperature converter as a controlled variable, sets the target temperature of the heater as a target value, and supplies electric power to the electric heater. This is a circuit in which an indicated value is an operation amount. Specifically, the temperature of the electric heater is controlled to the target value by adjusting the power supplied to the heater so that the value output from the second temperature converter is equal to the target temperature of the heater. Like the first control circuit, the second control circuit may adopt PI control or PID control, but the time delay is short and the increase or decrease in power is reflected in the electric heater temperature quickly, and the first control circuit When the control is PI control or PID control, since the offset error of the electric heater temperature is eliminated by the integral term of the first control circuit, simple proportional control may be used. In the proportional control, as shown in FIG. 3, when the difference between the heater target temperature (target value) and the heater temperature (control amount) is smaller than the proportional band, electric power (or heat generation amount) proportional to the difference is supplied to the heater. give. If the difference is greater than the proportional band, maximum power is applied to the heater.

  Among the temperature regulators provided in the thermostat of the present invention, a limiting circuit that limits the target temperature of the heater output by the first control circuit to a predetermined value between the first control circuit and the second control circuit. Furthermore, you may have. As an example of the limiting circuit, the target temperature of the heater calculated by the adding circuit as shown in FIG. 2 is used as an input value, and when the target temperature of the heater exceeds a predetermined limiting temperature, the target temperature is set to the limiting temperature. A replacement circuit is given. The predetermined value (limit value) in the limit circuit may be determined in consideration of the risk of burns or ignition due to high temperatures. Further, the limit value may be changed according to the conditions for using the liquid chromatograph, for example, the solvent used.

  When the thermostat of the present invention is provided with a plurality of electric heaters and a second temperature sensor is provided for each heater, one first control circuit may be provided, and a second control circuit may be provided for each heater. The first control circuit and the second control circuit are provided one by one, and the control amount (heater temperature output by the second temperature converter) in the second control circuit is output by the second temperature converter provided for each heater. The aspect which makes it an average value of a value may be sufficient.

  In the thermostat of the present invention, the air temperature in the housing output from the first temperature converter, the heater temperature output from the second temperature converter, the target temperature of the air in the housing, the target temperature of the heater (with a limiting circuit). If it is, the target temperature of the heater after the restriction output by the restriction circuit), or a value indicating the power to be given to the heater, is displayed on the temperature controller or the chromatograph control device. Or may be displayed on an external display or the like. Further, the temperature difference, for example, the difference between the air temperature in the housing and the target temperature in the housing, the difference between the heater temperature or the target temperature and the target temperature in the housing, the heater temperature or the target temperature and the target temperature in the housing, You may display the difference of air temperature, the difference of heater temperature, and its target temperature.

  In order to change the electric power applied to the electric heater based on the operation amount in the second control circuit, the current or voltage flowing through the heater is continuously changed by a transistor or FET (field effect transistor) as is generally known. You can adjust the power by changing it, or you can adjust the power by changing the duty ratio by turning on or off the current or voltage at regular intervals using switching devices such as transistors, FETs, thyristors, etc. Also good. A DC power supply may be used, or an AC power supply may be used.

  The constant temperature bath of the present invention includes a casing that houses any one or more of a mobile phase supply means, a sample introduction means, a separation means, and a detection means, an electric heater that supplies heat to the air in the casing, and the casing. A first temperature sensor for detecting the air temperature in the body, a second temperature sensor for detecting the temperature of the heater, a temperature regulator for controlling the air temperature in the housing, and a fan for circulating the air in the housing And the temperature regulator is connected to the first temperature sensor and outputs a value indicating the air temperature, and a value connected to the second temperature sensor and indicating the heater temperature A first temperature converter that outputs the first temperature converter, and a first control that uses the air temperature in the housing output from the first temperature converter as a control amount, the target temperature of the air in the housing as a target value, and the target temperature of the heater as an operation amount Circuit and heater temperature output by the second temperature converter Was the target value of the target temperature of the heater as a control amount, and the operation amount of the value indicating the power applied to the heater, it is characterized in that it comprises a second control circuit.

  Furthermore, the temperature controller provided in the thermostat of the present invention further includes a limiting circuit that limits the target temperature of the heater output by the first control circuit to a predetermined value or less, so that, for example, a large number of separation columns can be inserted. Therefore, even if the heat flow is hindered due to air flow deterioration, clogging with dust or dirt, or air circulation is stopped due to a fan failure, Since the overheating of the liquid chromatograph can be prevented, the utilization efficiency of the liquid chromatograph is improved and the safety is also improved. Even if the heater temperature temporarily reaches a predetermined value at the start of temperature control, the temperature increase rate is slowed by maintaining the heater temperature at the predetermined value instead of stopping the temperature control. However, the air temperature in the housing can be gradually increased.

  Furthermore, the air temperature in the housing output by the first temperature converter, the heater temperature output by the second temperature converter, the target temperature of the air in the housing, the target temperature of the heater (when a limiting circuit is provided) The target temperature of the heater after the restriction output by the restriction circuit), the value indicating the electric power applied to the heater, and the like are displayed on the display means, so that the operation state of the thermostat can be accurately grasped. Further, the temperature difference, for example, the difference between the air temperature in the housing and the target temperature in the housing, the difference between the heater temperature or the target temperature and the target temperature in the housing, the heater temperature or the target temperature and the target temperature in the housing, By displaying the difference in air temperature, the difference between the heater temperature and its target temperature, etc., it becomes possible to accurately grasp the operation state of the thermostatic bath.

The figure which shows the one aspect | mode of the thermostat of this invention. The figure which shows an example of the control by the limiting circuit provided in the thermostat of this invention. The figure which shows an example of the proportional control by the 2nd control circuit provided in the thermostat of this invention.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, these examples do not limit this invention.

Example 1
One mode of the thermostat 100 of the present invention is shown in FIG. A thermostat 100 shown in FIG. 1 includes a housing 10 for housing the separation column 20, an electric heater 30 for heating the air in the housing 10, and a circuit for circulating the air in the housing 10. A fan 40, a first temperature sensor 51 for detecting the air temperature in the housing 10, a second temperature sensor 52 for detecting the temperature of the electric heater 30, and a temperature regulator 60 for controlling the air temperature in the housing. Have. The temperature regulator 60 is connected to the first temperature sensor 51 and outputs a value indicating the air temperature in the housing 10. The temperature regulator 60 is connected to the second temperature sensor 52 and connected to the electric heater 30. The second temperature converter 62 that outputs a value indicating the temperature, and the air temperature in the housing 10 output by the first temperature converter 61 is the control amount, and the target temperature of the air in the housing 10 is the target value. Electric power given to the electric heater 30 using the first control circuit 63 having the target temperature of the electric heater 30 as an operation amount and the heater temperature output from the second temperature converter 62 as the control amount and the target temperature of the electric heater 30 as the target value. And a second control circuit 64 having an operation amount as a value for instructing.

  In the thermostatic chamber 100 shown in FIG. 1, the housing 10 has a capacity of 30 L, and is insulated from the outside air by a heat insulating material having a thickness of 20 mm. The first temperature sensor 51 uses a platinum resistance temperature sensor, and the second temperature sensor 52 uses a thermocouple. A detection result by the first temperature sensor 51 is converted into a temperature signal 71 by a first temperature converter 61 including a constant current power source, a voltage amplifier, a correction circuit, and the like, and is input to the first control circuit 63. The detection result by the second temperature sensor 52 is converted into a temperature signal 72 by a second temperature converter 62 including a cold junction, a cold junction compensation circuit, and a voltage amplifier, and the addition circuit 63b in the first control circuit and the second Input to the control circuit 64. The PID control circuit 63a in the first control circuit includes a temperature signal 81 from the first temperature sensor 51 output from the first temperature converter 61 and a target temperature of air in the housing 10 (target value temperature signal 73). And a signal indicating a difference between the target temperature of the electric heater 30 and the current temperature of the electric heater 30 is output based on the PID control (temperature difference instruction signal 74). The integral term of the PID control is reset to zero when the air temperature signal 71 in the housing 10 reaches the target value for the first time after the temperature adjustment is started. The temperature difference instruction signal 74 and the temperature of the electric heater 30 detected by the second temperature sensor 52 output from the second temperature converter 62 are added by the adder circuit 63b in the first control circuit to add the target temperature (instruction of the electric heater). Temperature) and then passing through the limiting circuit 65, the target temperature (indicated temperature) of the electric heater 30 is limited to a predetermined value (restricted value) or less (temperature indicating signal 75). The second control circuit 64 instructs power proportional to the difference between the target temperature (temperature instruction signal 75) of the electric heater 30 and the temperature signal 72 from the second temperature sensor 52 output from the second temperature converter 62. A value 76 is output, and power 77 is supplied to the electric heater 30 by the power supply circuit 66. In the thermostat 100 shown in FIG. 1, the electric power supplied to the electric heater 30 is 400 W, and the heating value of the heater is controlled by changing the ON duty ratio from 0% to 100% in a cycle of 2 seconds (proportional ON / OFF control).

  The limit value of the temperature of the electric heater 30 by the limit circuit 65 may be appropriately determined in consideration of the ignition point of the eluent used. For example, when tetrahydrofuran is used as the eluent, since the ignition point is around 230 ° C., ignition can be prevented by setting the limit value to 200 ° C.

  The present invention can prevent overheating of the heater in an air circulation thermostat containing any one or more of mobile phase supply means, sample introduction means, separation means, and detection means. It is a particularly useful invention for a liquid chromatograph that is required to be used in the above.

DESCRIPTION OF SYMBOLS 100: Thermostatic bath 10: Housing | casing 20: Separation column 30: Electric heater 40: Fan 51: 1st temperature sensor 52: 2nd temperature sensor 60: Temperature regulator 61: 1st temperature converter 62: 2nd temperature converter 63: First control circuit 63a: PID control circuit 63b: Addition circuit 64: Second control circuit 65: Limiting circuit 66: Power supply circuit 71/72: Temperature signal 73: Target value temperature signal 74: Temperature difference instruction signal 75: Temperature instruction signal 76: Power instruction signal 77: Supply power

Claims (4)

Provided in a chromatograph including a mobile phase supply means, a sample introduction means, a separation means, and a detection means, and a case that houses any one or more of the means, and supplies heat to the air in the case An electric heater, a first temperature sensor for detecting an air temperature in the housing, a second temperature sensor for detecting the temperature of the heater, a temperature regulator for controlling the air temperature in the housing, A thermostat for controlling the temperature of any one or more of the above means, and the temperature regulator,
A first temperature converter connected to the first temperature sensor and outputting a value indicating the air temperature;
A second temperature converter connected to the second temperature sensor and outputting a value indicating the heater temperature;
A first control circuit, wherein the air temperature in the housing output by the first temperature converter is a control amount, the target temperature of the air in the housing is a target value, and the target temperature of the heater is an operation amount;
A second control circuit, wherein the heater temperature output from the second temperature converter is a control amount, the target temperature of the heater is a target value, and a value indicating the power to be given to the heater is an operation amount;
The thermostat having the above. The heater further includes a limiting circuit that limits the target temperature of the heater output from the first control circuit to a predetermined value or less in the temperature regulator, and the target value in the second control circuit is limited by the limiting circuit. The thermostat according to claim 1, wherein The first control circuit
The PI temperature output from the first temperature converter is a control amount, the target temperature of the air in the housing is a target value, and the difference between the target temperature of the heater and the current heater temperature is an operation amount. A control circuit or a PID control circuit;
An adder circuit for calculating a target temperature of the heater from the sum of the operation amount of the PI control circuit or the PID control circuit and the heater temperature output from the second temperature converter;
The thermostat according to claim 1 or 2, which is a circuit having The air temperature in the housing output from the first temperature converter, the heater temperature output from the second temperature converter, the target temperature of the air in the housing, the target temperature of the heater, the value indicating the power to be applied to the heater, or these The thermostat according to any one of claims 1 to 3, further comprising display means for displaying any one or more of the temperature differences.

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