JP2001074652A - Chopper and infrared gas analyzer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chopper capable of continuously performing the transmission and cutting-off of light in a restricted space. SOLUTION: A rotary shaft 4 is provided in the center of a sherical rotary body 2, which comprises a light impervious substance and has a through-hole 2a formed thereon so as to pass the center thereof, so as to cross the axis O of the through-hole 2a and connected to a motor 3 to rotationally drive the spherical rotary body 2. Since light is passed/cut off by the rotation of the rotary body having the through-hole and a rotary space wasteful to the rotation of the rotary part making light intermittent is not required, a chopper capable of continuously performing the transmission and cutting-off of light in a restricted space is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chopper used for an optical device for intermittently (chopping) light from a light source or the like to obtain intermittent light, and more particularly to a chopper suitable for an infrared gas analyzer. .

[0002]

2. Description of the Related Art Many heteronuclear molecules consisting of two or more different atoms are irradiated with infrared light having a wavelength of 1 to 20 μm, and the transition of vibrational and rotational kinetic energy levels specific to the chemical species occurs. Absorbs certain infrared spectra, causing thermodynamic changes such as increased internal energy, volume or pressure. Non-dispersive infrared gas analyzer (NDI)
R) is an instrument for measuring the concentration of the gas component by utilizing such characteristics of the gas component.

FIG. 6 shows a configuration of a single beam NDID. As shown in the figure, an infrared gas analyzer generally comprises a light source section 42 for generating infrared light, a cell section 44 into which a sample is introduced, and a detector section 46 for measuring the intensity of infrared light passing through the cell section. It consists of three parts. The light source unit 42 includes a heater (light source) 48 as a generation source for generating infrared light, and a chopper 50 for intermittently inputting infrared light to the cell unit 44 and the detector unit 46.

Further, as shown in FIG. 7, a chopper 50 includes a rotating disk 52 having a cutout portion 51 formed by cutting out a part thereof so as to allow the light from the light source 48 to pass therethrough, and the rotating disk 52. The motor 52 drives the plate 52 to rotate. By rotating the rotary disk 52 by the motor 54, an uncut portion (light shielding portion) 53 of the rotary disk 52 is positioned in front of the light source 48. When the cutout portion 51 is located in front of the light source 48, the infrared light from the light source 48 passes therethrough and is irradiated on the cell portion 44 when the cutout portion 51 is located in front of the light source 48. You. The cell portion 44 is a portion where a sample is introduced, and the front and rear of the pipe are sealed with a window 54 made of infrared-transmissive glass or CaF2 that can transmit infrared rays in a wide spectral range, and another side is provided on one side of the pipe. A gas lead-in / out hole 56 is provided to allow gas to flow to one end, and its inner surface is coated with a mirror finish or a coating of gold or the like to efficiently reflect infrared light.

As shown in the detailed view of FIG. 8, the detector section 46 is divided into two front and rear chambers 24 and 26, and at least the front face of the front chamber 24 and the partition wall between the front chamber 24 and the rear chamber 26 are infrared rays. The two chambers are separated by a light-transmitting window 28 and have a structure in which they are connected by a bypass 30 capable of completely isolating or transferring a gas at a small flow rate. In addition, the front and rear rooms 24,
In order to measure the pressure difference of 26, the pressure difference is connected to a pressure detecting element 34 such as a membrane condenser or a pressure sensor via a partition wall of these two chambers or an introduction pipe 32. Further, these two chambers are filled with only a chemical species such as CO2 or a gas obtained by diluting the chemical species with an inert gas such as Ar, He, or N2, which is a measurement target of the infrared gas analysis. Have been.

The infrared light emitted from the light source section 42 is transmitted to the cell section 4.
4 and enters the detector 46. At this time,
If the component to be measured exists inside the cell, a part of the infrared light incident on the cell according to the gas concentration in the cell is absorbed by the gas inside the cell, and the remaining infrared light is incident on the detector section 46. The infrared light incident from the front of the front chamber 24 of the detector unit 46 is absorbed by the front chamber 24 and the rear chamber 26, and the energy absorption causes a pressure difference between the front and rear chambers. it can.

[0007]

As described above, the light source unit 4
2. A chopper composed of a rotating disk 52 having a light-shielding portion 53 and a notch 51 and a motor 54 for rotating the same, and an NDIR using the same. Then, there is the following problem.

That is, when viewed in a plane perpendicular to the required optical axis, a plane portion other than the front of the light source, that is, the rotating disk 5
The plane portion below the rotation axis 2 (below the dashed line in FIG. 6) is a space necessary for rotating the rotating disk 52, and is an unnecessary unnecessary space portion. Therefore, a space (volume) twice as large as the space originally required is required. For this reason, there is a problem that the size of the device is increased, and the chopper is a bottleneck in reducing the size of the device using the device. Further, since the rotating disk is rotated, unnecessary vibration is generated due to bending of the disk during rotation and noise is generated. In order to prevent this, it is necessary to increase the thickness of the rotating disk to increase the rigidity, but this causes a problem of increasing the weight of the device. In order to solve these problems, a chopper using liquid crystal is also used. However, there is a problem that light cannot be completely shielded and a response time is difficult.

The present invention has been made in order to solve the above-mentioned problem, and does not require a useless rotating space for the rotation of a rotating unit for intermittent light, and is capable of transmitting light in a limited space. It is an object of the present invention to provide a chopper capable of continuously performing cutoff and a small and lightweight infrared gas analyzer provided with the chopper.

[0010]

In order to solve the above-mentioned problems, a chopper according to the present invention comprises a rotating body having a through hole through which light passes, around a center axis thereof perpendicular to the axis of the through hole. The rotating body is characterized in that a spherical body (spherical body) is suitable as the rotating body.

According to such a configuration, the light passes through the through hole at the rotation position (the front position of the light source) where the through hole formed in the rotation body coincides with the optical axis by the rotation of the rotating body, and at other rotation positions, the light passes through the through hole. Light is blocked by the rotator itself, and the rotator rotates around its central axis orthogonal to the axis of the through-hole. Light transmission and blocking can be performed continuously, and unnecessary rotation space is not required for rotation of the rotating unit that interrupts light, so light transmission and blocking can be performed continuously in a limited space. Can be performed. Further, if the rotating body is a sphere having a through hole, there is an advantage that there is no more useless rotating space, light can be interrupted in a smaller space, and rotation of the rotating body can be performed smoothly.

Further, in the infrared gas analyzer according to the present invention, there is provided a rotating body having a through hole between the light source section and the measuring cell section through which infrared light passes, and this rotating body is orthogonal to the axis of the through hole. And a chopper comprising a drive mechanism for rotating about a central axis of the chopper.

According to such a configuration, at the rotation position (the front position of the light source) where the through-hole formed in the rotation of the rotating body coincides with the optical axis, the infrared light generated in the light source section passes through the through-hole. In the other rotation positions, the rotating body itself blocks the infrared light generated by the light source section, and the rotating body rotates around its central axis orthogonal to the axis of the through hole. In addition, since the transmission and blocking of infrared light can be continuously performed in a space corresponding to a blocking portion on the entire surface of the light source of this type of conventional chopper, there is no useless rotation of the rotating body that interrupts light. Since a rotating space is not required, a small and lightweight infrared gas analyzer can be obtained. Further, when the rotating body constituting the chopper is a sphere having a through hole, there is no more useless rotating space, and a smaller and lighter infrared gas analyzer can be obtained.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view schematically showing one embodiment of a chopper according to the present invention. As shown in FIG. 1, the chopper 1 comprises a spherical rotating body 2 made of a light-impermeable material and a motor 3 for rotating the rotating body. The rotating body 2 has a through hole 2a passing through the center thereof. The rotating shaft 4 is fixed to the center of the through hole 2 a orthogonal to the axis O. The rotating shaft 4 is connected to the motor 3, and the rotating body 2 drives the rotating shaft 4 by driving the motor 3. Rotate to the center. The spherical rotating body 2 is accommodated in a casing (not shown), the motor 3 is disposed outside the casing, and the rotating shaft 4 fixed to the rotating body 2 is connected to the motor 4 through the casing. I have.

FIG. 2 is a schematic diagram showing an arrangement relationship between instruments such as an analyzer and the chopper 1 shown in FIG. 1. The chopper 1 is arranged in front of a light source 48 and, if necessary, a casing before and after the spherical rotating body 2. On the inner wall of the body 5, a light-shielding barrier 6 for preventing light from leaking from a space for rotation of the rotating body 2 is provided.

FIG. 3 is a diagram for explaining the operation of the chopper having the structure shown in FIG. 1. When the non-through hole of the rotating body 2 is located in front of the light source as shown in FIG. Is blocked by the rotator 2 and cannot reach the opposite direction, but when the through hole 2a of the rotator 2 is located in front of the light source and coincides with the optical axis as shown in FIG. This through hole 2
The light indicated by the arrow from the light source passing through a can reach the opposite direction of the rotating body 2. The timing of blocking / passing light by the chopper 1 can be adjusted not only by the rotation speed of the rotating body 2 but also by the diameter of the opening 2a. In the figure, reference numeral 7 denotes a slit for regulating the light flux width.

FIG. 4 is a schematic view showing a method of driving the rotating body 2 to rotate. FIG. 4A shows the rotating body 2 rotatably supported in a housing 5 by a bearing or the like (not shown). Is directly connected to the motor 3 disposed outside the housing 5. In FIG. 2B, a magnetic body (magnet) 8 is attached to the rotating shaft 4 of the rotating body 2, a magnet 9 rotated by the motor 3 is arranged outside the housing 5, and the rotating body 2 is rotated by the rotation of the magnet 9. It is configured to be driven to rotate in a non-contact manner from outside the housing 5. In this case, the rotating body 2 itself may be formed of a magnetic material. FIG. 3C shows a case in which the coil 10 is wound around the rotating body 2 and the magnetic pole (magnet) 11 is provided inside or outside the housing 5 as in FIG. It is arranged to be a DC motor. In the drawing, reference numeral 12 denotes a rotating shaft and lead, 13 denotes a support bridge and lead, and 14 denotes a lead wire.

FIG. 5A is a schematic view showing an NDIR using the chopper 1 having the configuration shown in FIGS. 1 and 4. The chopper 1 is provided with a light source of a light source section 42 for generating infrared light and a sample. Is placed between the cell section 44 and the cell section 44 into which the cell is introduced. According to this configuration, this kind of conventional NDIR shown in FIG.
This eliminates the need for the space indicated by the one-dot chain line indispensable for the rotation of the rotating disk 52 of the chopper, so that it is possible to obtain an NDIR approximately half the size of the conventional one.

The rotary driving method of the rotating body constituting the chopper is shown in FIG. 4. In addition, the rotating body is formed of a conductor to form a rotor, and a stator is disposed inside or outside the housing. It may be driven to rotate. Further, in the embodiment, the rotating body having the through hole is a spherical body, but may be another shape such as an elliptical body, a cube,
The use of a spherical body as in the embodiment is advantageous in minimizing the rotation space of the rotating body and smoothly driving the rotating body. Further, the chopper according to the present invention can be applied to an apparatus for interrupting light from a light source or interrupting light incident on a detector, in addition to an infrared gas analyzer.

[0020]

According to the chopper of the present invention, light passes / blocks by the rotation of the rotating body having the through-hole, so that a useless rotating space is not required for the rotation of the rotating unit for interrupting the light. As a result, a chopper capable of continuously transmitting and blocking light in the defined space is obtained. In addition, an infrared gas analyzer using a chopper that passes / blocks light by rotation of a rotating body having a through-hole has no useless rotating space for rotation of a rotating body part that interrupts light from a light source, so that it is compact and compact. A lightweight infrared gas analyzer can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing one embodiment of a chopper according to the present invention.

FIG. 2 is a schematic diagram showing an arrangement relationship between a device and the chopper shown in FIG. 1;

FIG. 3 is a diagram for explaining the operation of the chopper having the configuration shown in FIG. 1;

FIG. 4 is a schematic diagram showing a configuration of a rotation driving method of a rotating body.

FIG. 5 is a schematic diagram showing an embodiment of the infrared gas analyzer of the present invention in relation to a conventional analyzer of this type.

FIG. 6 is a schematic diagram showing a configuration of a conventional infrared gas analyzer.

FIG. 7 is a schematic diagram showing a configuration of a chopper of a conventional infrared gas analyzer.

FIG. 8 is a schematic diagram showing a configuration of a detector section of a conventional infrared gas analyzer.

[Explanation of symbols]

1: Chopper 2: Spherical rotating body
2a: Through hole 3: Motor 4: Rotary shaft
5: Housing 42: Light source 44: Cell
46: detector part 48: heater (light source)

Claims (4)

[Claims] 1. A chopper comprising: a rotating body having a through hole through which light passes; and a driving mechanism for rotating the rotating body around a central axis thereof orthogonal to the axis of the through hole. 2. The chopper according to claim 1, wherein the rotating body is a spherical body having a through hole. 3. A light source for irradiating the measurement cell with infrared light is disposed at one end of the measurement cell, and a detector for detecting the intensity of infrared light passing through the measurement cell is provided at the other end of the measurement cell. A chopper that is disposed and chops infrared light emitted from the light source unit to the measurement cell, wherein the chopper has a through-hole through which the infrared light passes. An infrared gas analyzer comprising: a body; and a drive mechanism for rotating the rotating body about a central axis thereof orthogonal to the axis of the through hole. 4. The infrared gas analyzer according to claim 3, wherein the rotating body is a spherical body having a through hole.