JP2002139483A - Gas chromatograph - Google Patents

Abstract

(57) [Problem] To provide a gas chromatograph having an oven capable of precisely controlling an internal temperature. SOLUTION: When the power supply of the apparatus is started, the flap 3 is completely closed, and then the pulse motor 5 is opened one pulse at a time in the direction in which the flap 3 opens. For a while, the flap 3 does not actually open due to the dead zone, and the flap 3 opens only after the dead zone is exceeded. At this time, outside air enters inside the oven 1 and the temperature inside the oven 1 changes. By detecting this change, the number of pulses (referred to as A) in the dead zone period is detected and stored. When opening the flap 3, first, the previous operation of the pulse motor 5 is checked. If the previous operation is "open", the flap 3 is driven in a direction to open one pulse. Last action was "close"
If so, driving is performed in the direction of opening (A + 1) pulses in consideration of the dead zone. At this time, the flap 3 is actually driven to open by one pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph provided with an oven for controlling the temperature such as heating and cooling of a column.

[0002]

2. Description of the Related Art In recent gas chromatographs, separation and analysis are often carried out by sequentially or stepwise raising the temperature of a column after injecting a sample, and the capillary column used for analysis is also rapidly heated and cooled. Excellent and durable products are being developed. In order to perform efficient analysis using such a high-performance capillary column, a gas chromatograph equipped with an oven capable of rapidly increasing and cooling the temperature is required. By raising and cooling the temperature of the capillary column at a high speed, the analysis time can be shortened, and the processing capacity of the apparatus can be improved.

[0003] For example, after the inside of the oven is analyzed at a high temperature of 100 ° C or higher by a heater installed in the oven, the device is cooled to room temperature as soon as possible. In conventional gas chromatograph ovens, after analyzing the inside as a high temperature state, when cooling, open the flap attached to the suction and exhaust ports of the oven, stir the fan inside the oven, and forcibly replace the air. It has a structure. In this case, flaps for exhaust and intake are installed independently and can be individually opened and closed to suck and exhaust, or one flap is opened and closed to suck and exhaust.

In order to perform an analysis accurately and with good reproducibility, it is necessary to strictly control the temperature inside the oven. In particular, when controlling the temperature at low temperatures, it is impossible to perform strict control only by controlling the calorific value of the heater, and together with controlling the calorific value of the heater, the flap is opened and closed to cool the temperature. Control. That is, if the actual temperature is higher than the set temperature, the opening / closing amount of the flap is increased, and if it is lower, the opening / closing amount is reduced.

[0005]

In order to control the opening and closing amount of the flap, a pulse motor is usually used as a driving means of the flap. However, there is a dead zone in the pulse motor and mechanism for driving the flap. For example, when switching from the operation of opening the flap to the operation of closing it, there is a period during which the flap does not operate despite receiving a close command for several pulses. For this reason, delicate control of opening and closing the flap becomes impossible, and it becomes difficult to strictly control the temperature in the oven.

The present invention has been made to solve the above problems, and has as its object to provide a gas chromatograph having an oven capable of strictly controlling the internal temperature.

[0007]

In order to solve the above-mentioned problems, the gas chromatograph oven of the present invention makes it possible to finely control the opening and closing of the flap by correcting the dead zone at the time of switching the opening and closing of the flap. The internal temperature can be strictly controlled. In order to correct the dead zone at the time of flap opening / closing switching, the position where the flap is completely closed is regarded as zero, and is set as a reference position for flap control. When the pulse is opened from this position one pulse at a time, the flap does not actually operate due to the dead zone for a while, and when the dead band is exceeded, the flap is opened for the first time, whereby the temperature in the oven fluctuates. By sensing the temperature change in the oven, the number of pulses in the dead zone can be detected. This pulse number is stored, and in the subsequent flap opening / closing control, delicate control of flap opening / closing is enabled by performing correction of a dead zone. As a result, the temperature in the oven can be strictly controlled, and accurate and reproducible measurement can be performed.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 is a schematic sectional view of an embodiment of an oven used in the gas chromatograph of the present invention. The oven 1 comprises a flap 3, a shaft 4, a pulse motor 5, a fan 7, a heater 8, a temperature detector 9 and a controller 10, and the oven 1
Is covered with a heat insulating material 12.

Next, the operation will be described. Flap 3
Are driven by a pulse motor 5 via a shaft 4 and are opened and closed. The pulse motor 5 is controlled by the controller 10. The temperature in the oven 1 is controlled by controlling the heating by the heater 8 and the opening and closing of the flap 3 by the controller 10 while monitoring the temperature in the oven by the temperature detector 9. As the temperature detector 9, a platinum resistor is used. Further, the fan 7 is rotated to constantly stir the air in the oven so that the temperature in the oven becomes uniform.

First, when the power supply of the apparatus is started, the flap 3 is unconditionally driven by the pulse motor 5 in a direction for closing a certain pulse, and is completely closed. This closed position is regarded as a zero point, and is stored in the controller 10 as a reference position for the flap 3 control. Next, the dead zone of the flap 3 is checked according to the flowchart shown in FIG. That is, from this closed position, the pulse motor 5 is opened one pulse at a time in the direction in which the flap 3 opens. The flap 3 does not actually open due to the dead zone for a while, and the flap 3 opens only after the dead zone is exceeded. At this time, outside air enters inside the oven 1 and the temperature inside the oven 1 changes. By detecting this change with the temperature detector 9, the number of pulses in the dead zone period is detected and stored in the controller 10. The number of pulses at this time is A.

Next, temperature control in the oven 1 is started. At this time, when opening and closing the flap 3, the opening and closing control is performed according to the chart shown in FIG. 1 or FIG. That is, when opening the flap 3, first, the previous operation of the pulse motor 5 is checked as shown in FIG. If the previous operation is "open", the flap 3 is driven in a direction to open one pulse. If the previous operation is “closed”, driving is performed in the direction of opening (A + 1) pulses in consideration of the dead zone. At this time, the flap 3 is actually driven to open by one pulse.

When closing the flap 3, the operation of the previous pulse motor 5 is first checked as shown in FIG. If the previous operation is "close", the flap 3 is driven in the direction to close one pulse. If the last action was "open",
Drive in the (A + 1) pulse closing direction in consideration of the dead zone. At this time, the flap 3 is actually driven in the direction to close by one pulse. In this way, by controlling the opening and closing in consideration of the dead zone of the flap 3, the flap 3
Can be finely controlled by the operation of the pulse motor 5 for each pulse.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various changes may be made within the scope of the present invention described in the appended claims. be able to. For example, in the above-described embodiment, one flap is opened and closed to perform intake and exhaust. However, two exhaust flaps and one intake flap may be independently installed and individually opened and closed.

[0014]

According to the gas chromatograph of the present invention,
Since the opening and closing of the flap installed in the oven can be delicately controlled, the temperature control in the oven can be strictly controlled, and as a result, accurate and reproducible analysis can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flowchart for performing flap opening / closing control (when a flap is opened) according to the present invention.

FIG. 2 is a diagram showing a flowchart for performing flap opening / closing control (when a flap is closed) according to the present invention.

FIG. 3 is a diagram showing a flowchart for detecting the number of pulses in a dead zone of a flap.

FIG. 4 is a schematic sectional view showing an embodiment of the oven of the present invention.

[Explanation of symbols]

 3 --- Flap 5 --- Pulse motor 7 --- Fan 8 --- Heater 9 --- Temperature detector 10 --- Controller

Claims (1)

[Claims] 1. A gas chromatograph comprising an oven for opening and closing a flap by using a pulse motor as a driving means to open and close a flap to perform suction and exhaust, wherein a control means for eliminating a dead zone at the time of flap opening and closing switching is provided. .