JP3028147B2 - Photoelectric dust sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects air contamination by mounting it on an air purifier used in non-residential buildings such as stores and offices and in general homes, or by installing it alone in a room. TECHNICAL FIELD The present invention relates to a photoelectric dust sensor suitably used for performing automatic operation of an air cleaner, a ventilation fan, and the like.

[0002]

2. Description of the Related Art Conventionally, an air purifier detects the dirt of indoor air to automatically operate the rotation and stop of an intake fan, and performs a ventilation operation of a ventilation fan as an air dirt sensor. Gas sensors that detect the change in the resistivity of tin oxide etc.
It takes about 5 minutes for the function to be stable after turning on the power, and for the function to start, and the resistance value of the sensor element is sufficient to return to the original state even after the smoke has been removed. Therefore, it was necessary to incorporate a timer control output. In addition, most timer conditions take into account predictions based on changes in dust concentration based on certain operating conditions, such as the size of a room. Since it is far from proper operation control, it has a drawback that it does not match the actual feeling of use of the air purifier.

[0003]

Therefore, recently, a photoelectric dust sensor which does not require such a timer has been developed. However, such a sensor has a floating concentration equal to that of the gas detection system. In order to realize dust detection performance, it is necessary to reduce the amount of stray light in the optical chamber. Such a photoelectric dust sensor includes an optical chamber in which a light-emitting device and a light-receiving device are opposed to each other such that their optical axes intersect,
The light emitted from the light emitter collides with the floating dust and diffusely reflected, and the scattered light is condensed on the light receiver and detected.However, even when there is no dust, the light emitted from the light emitter remains inside the optical chamber. The light that strikes the wall and is reflected and enters the light receiver is generally called stray light, and how to reduce this stray light is a major design issue. The detection of dust means that irrelevant light is constantly incident on the light receiver, so that the inner wall surface is easily affected by adhesion of dirt or dust. The present invention has been made in view of the above-described problems, and has as its object to provide a photoelectric dust sensor capable of almost eliminating stray light.

[0004]

SUMMARY OF THE INVENTION The present invention proposed to achieve the above object has an optical chamber in which a light emitting device and a light receiving device are opposed to each other so that their optical axes cross each other. In the photoelectric type dust sensor, which collects and detects the scattered light that diffuses and reflects when the light emitted from the dust strikes the floating dust, the optical chamber emits light from the light-emitting device side wall and the light receiving device side wall. Device, formed on a glossy surface inclined in a divergent shape so that the distance increases as the distance from the light receiver increases, and a partition wall with a cutout window formed in the middle is provided,
And so that the cutout window becomes a passage of the floating dust, a pair of flow openings penetrating the cutout window is formed, and the optical axis of the light emitter and the light receiver intersect at the cutout window of the partition wall. Are arranged as follows.

[0005]

In the present invention, air containing floating dust to be sampled flows into the optical chamber through a pair of flow openings formed in the optical chamber, and is radiated from a light emitter to receive scattered light which diffuses and reflects on the floating dust. The concentration of airborne dust is detected by collecting light in a vessel. In addition, since the optical axis of the light-emitting device and the light-receiving device is arranged so as to intersect with a notch window formed in the middle part of the partition wall of the optical chamber, the detection space is formed by a pair of communication ports formed by the notch of the partition wall. It is formed on a dust passage formed so as to penetrate the window. Further, in the optical chamber, the side wall on the light emitting side and the side wall on the light receiving side are formed on a glossy surface which is inclined so that the distance increases as the distance from the light emitting side and the light receiving side increases. The light emitted from the light emitter and passed through the detection space is reflected by the side walls of both the light emitter and the light receiver in a direction away from the light receiver, and is attenuated and absorbed in the light emitter and the light receiver in the respective rooms. Therefore, the strong light reflected by the inner wall in the optical chamber does not enter the light receiver, and stray light that causes a malfunction can be almost eliminated.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.
explain. FIG. 1 is a view showing a state in which a back cover of a photoelectric dust sensor used in the present invention is opened, FIG.
2 (b) and 2 (c) are views showing the cross-sectional structure of the optical chamber, and FIG.
1 shows an exploded perspective view of the photoelectric dust sensor of the present invention, and FIG. 4 shows a circuit configuration diagram. In the following, a description will be given assuming that the detection of a suspended dust concentration level (= 0.15 mg / m) specified in the Building Management Law is performed as a sensor for detecting air contamination. As shown in FIG. 1, a light emitting element ED (light emitting device) composed of a light emitting diode and a light receiving element LD (light receiving device) composed of a photodiode are disposed in a rectangular parallelepiped case 1. The case 1 is made of a synthetic resin, and has a rectangular frame-shaped body 10 having two open sides facing each other.
Metal first cover 20 that covers both opening surfaces
And a second cover 30 made of synthetic resin (see FIG. 2). The body 10 has a light emitting device side wall 11.
and the optical chamber 1 surrounded by the side wall 11b on the light-receiving side.
2 are formed. In addition, the first cover 20 and the second cover
Are formed in the cover 30, respectively, and the pair of flow ports 21 and 31 are located in a straight line in a direction orthogonal to the opening surface. Therefore, a pair of distribution ports 21,
At 31, the introduced floating dust flows into a detection space (indicated by oblique lines in FIG. 1) which is an overlapping portion between the irradiation area of the light emitting element ED and the light receiving area of the light receiving element LD. The optical chamber 12
Inside, as shown in FIG. 1, a light emitting element ED and a light receiving element L
D, a partition 18 is formed, and a portion of the partition 18 corresponding to the flow window 14 (see FIG. 3) is cut out to form the cutout window 1.
9 are formed. Therefore, the partition wall 18 prevents light from the light emitting element ED from directly entering the light receiving element LD. Light emitting element ED and light receiving element LD
Is disposed in the upper part of the case 1 in the optical chamber 12 as shown in FIG. 1, and both side walls 11a and 11b which define the optical chamber 12 gradually decrease the distance from the lower part to the upper part. ing. That is, the side wall 11a on the light emitting device side,
The side wall 11b on the side of the light receiver is inclined so as to expand as the distance from the light emitter ED and the light receiver LD increases. Here, the case 1 is generally made of a resin molded product, but is molded in a mold in which plating and the like are performed after processing the mold surface so that the surfaces of the side walls 11a and 11b are particularly mirror-finished. It is a mirror surface.

According to the sensor of the present invention, the side walls 11a and 11b on both the light emitting side and the light receiving side that define the optical chamber 12 are provided.
Is inclined so that the distance gradually decreases from the lower part to the upper part, and the surface is made glossy, so that the light emitted from the light emitting element ED is reflected by the opposing light receiving side wall 11b and most of the light is emitted. The light energy is a synthetic resin cover 30
Attenuate to a minute level while repeating the diffuse reflection on the inner surface of the case, facing the surface of the case, away from the detection area on the matte surface, the case bottom, the case side wall, the partition, and so on,
The light enters the detection area of the light receiving element LD. Further, even if a small amount of light energy diffusely reflected on the above-mentioned mirrored side wall reaches the side wall opposed to the light receiving element LD, it is inclined and mirrored, so that most of the light energy does not go to the light receiving element LD. Toward the cover made of synthetic resin. Therefore,
The stray light that is reflected from the light emitting element ED on the inner wall surface of the optical chamber 12 and reaches the light receiving element LD with high intensity in a state without dust is almost eliminated.

As shown in FIG. 4, the light emitting element ED is driven by an oscillation circuit 51 and a driving circuit 52 so as to be intermittently turned on at a substantially constant cycle. On the other hand, a light-receiving signal of a current output corresponding to the amount of light received by the light-receiving element LD has a very high input impedance and a very high feedback resistance (about 100Ω) formed by using an operational amplifier circuit. Is converted into a voltage output corresponding to the amount of received light. Thereafter, the received light signal converted into the voltage output passes through the bandpass filter 62 and further passes through the peak cut circuit 6.
3 to remove noise components. In this way, after removing the noise component from the received light signal, the received light signal is input to the sample hold circuit 64, and the received light signal is captured in synchronization with the lighting timing of the light emitting element ED based on the output of the oscillation circuit 51. The voltage value of the light receiving signal is held until the next light receiving signal is input. A differential amplifier circuit 67 for taking a difference between an output of the sample-and-hold circuit 64 and a reference voltage output from a reference voltage generating circuit 66 to perform correction; By amplifying by 68, a continuous output corresponding to the received light signal is obtained. The reference voltage generation circuit 66 includes a first reference voltage generation circuit 66a that divides a power supply voltage, and a second reference voltage generation circuit that outputs a second reference voltage based on the first reference voltage output from the first reference voltage generation circuit 66a. And a reference voltage generation circuit 66b. The differential amplifier 67 receives the second reference voltage, and the DC amplifier 68 receives the first reference voltage. Each of the above circuits is supplied with power by a power supply circuit 55 for converting a DC voltage into a constant voltage.

FIG. 5 is an exploded perspective view of an air purifier provided with the photoelectric dust sensor according to the present invention. The photoelectric dust sensor A passes a part of the intake airflow of the fan 72 of the air purifier body B from the side opposite to the air suction port 14 to the bypass passage 77.
To bypass. This air purifier B has a housing 71
And a blow-out port 76 provided on the upper surface of the housing 71 with air introduced from the front surface of the housing 71.
Is transmitted from the server. A front cover 73 is detachably mounted on the front surface of the casing 71, and a filter holder 74 is provided between the casing 71 and the front cover 73.
Are arranged in a pair. The filter 75a is provided to prevent large dust from entering the inside, and the filter 75b is provided to remove floating particles and a part of odor.

[0010]

As described above, according to the photoelectric dust sensor of the present invention, stray light can be almost eliminated. As a result, the amplification factor of the amplifier circuit can be increased, and fine suspended dust particles can be detected with high sensitivity.

[Brief description of the drawings]

FIG. 1 is a plan view of a photoelectric dust sensor according to the present invention in a state where a back cover is removed.

2A is a diagram showing the appearance of the photoelectric dust sensor of the present invention, FIG. 2B is a cross-sectional view taken along line II of FIG. 2A, and FIG. 2C is a cross-sectional view taken along line II-II of FIG. Is shown.

FIG. 3 is an exploded perspective view of the photoelectric dust sensor of the present invention.

FIG. 4 shows a block diagram of the circuit of the present invention.

FIG. 5 is an exploded perspective view of an air purifier provided with the photoelectric dust sensor of the present invention.

[Explanation of symbols]

 A: photoelectric dust sensor 1: rectangular parallelepiped case 10: rectangular frame-shaped body 11a: side wall with a glossy surface on the light emitting device side 11b: surface on the light receiving device side Side wall formed on glossy surface 12 Optical chamber 20 First cover 30 Second cover 21 31 Distribution port ED Light-emitting element (light-emitting device) LD Light receiving element (receiver)

Continued on the front page (56) References JP-A 4-32062 (JP, U) JP-A 61-56563 (JP, U) JP-A 61-46454 (JP, U) (58) Fields surveyed (Int .Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61

Claims (1)

(57) [Claims] An optical chamber in which a light emitting device and a light receiving device are opposed to each other so that their optical axes intersect with each other, and scattered light which is diffusely reflected by light emitted from the light emitting device hitting floating dust is collected by the light receiving device. In a photoelectric dust sensor that detects light, in the optical chamber, the side wall on the light emitting device side and the side wall on the light receiving device side are inclined in a divergent shape so that the distance increases as the distance from the light emitting device and the light receiving device increases. And, as well as being formed as a glossy surface, providing a partition having a cutout window in the middle, and so that the cutout window becomes a passage for floating dust,
A photoelectric dust sensor, wherein a pair of communication ports penetrating a notch window is formed, and an optical axis of the light emitting device and the light receiving device is arranged to intersect at the notch window of the partition wall.