JPH04259848A - Detecting apparatus for floating fine particle - Google Patents

Abstract

PURPOSE:To detect the floating fine particles with high sensitivity by widening the detecting space and detecting the floating fine particles on a flow passage of the air. CONSTITUTION:A light emitting element ED for casting light to the detecting space, and a photodetector LD for receiving the scattering light from the light emitting element ED because of the floating fine particles are provided at one side of a circuit board 4. Then, the light emitting element ED is driven and, a circuit part which detects the floating particles within the detecting space is accordance with the receiving signal output from the photodetector LD is mounted at the other side of the circuit board 4. A pair of circulation ports 21, 31 to circulate the air into the detecting space are formed at the front and rear sides of the circuit board 4 in a casing 1. Therefore, a flow passage running in the detecting space between the circulation ports 21 and 31 is defined in the casing 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspended particulate detection device for detecting suspended particulates such as smoke particles and dust.

0002

2. Description of the Related Art Conventionally, floating particle detection devices have been used in smoke detectors, air purifiers, and the like to detect floating particles such as smoke particles and dust. Various methods have been considered for detecting floating particles, but as shown in Figure 8, light such as infrared rays is irradiated into the detection space by a light emitting element ED, and scattering occurs when floating particles are present in the detection space. A device in which light is received by a light receiving element LD and floating particles are detected based on a change in the light reception signal output from the light receiving element LD is often adopted.

[0003] Driving the light emitting element ED or driving the light receiving element LD
A circuit section for processing light reception signals outputted from the light emitting element ED and the light receiving element LD is mounted on a circuit board 4, and this circuit board 4 is housed in the case 1. That is, a detection space is formed within the case 1. On the circuit board 4, the parts constituting the circuit section are arranged on the same surface as the light emitting element ED and the light receiving element LD. One side is a sensing space, and the other side is a space for mounting components. Further, the flow port 6 for introducing suspended particles into the detection space is formed only on one side of the case 1.

0004

[Problems to be Solved by the Invention] In the above configuration, only a portion of one side of the circuit board 4 is used as the detection space, and the detection space is small. The amount of scattered light is small and the intensity of the scattered light cannot be obtained sufficiently. That is, there is a problem that the sensitivity is low and that floating particles cannot be detected if they are at a low concentration. In addition, since the flow port 6 is formed only on one side of the case 1, there is no choice but to wait for floating particles to be naturally introduced, and it is necessary to judge whether the air introduced by an air purifier or the like is clean or not. There is a problem in that sensitivity cannot be increased in such cases.

[0005] The present invention is aimed at solving the above-mentioned problems, and is capable of detecting suspended particles with high sensitivity by widening the detection space and detecting the presence or absence of suspended particles on an air flow path. The present invention aims to provide a suspended particulate detection device that enables the detection of suspended particles.

[0006]

[Means for Solving the Problems] In claim 1, in order to achieve the above object, there is provided a light emitting element that irradiates light into a detection space, and a light emitting element that receives light scattered by floating particles among the light irradiated from the light emitting element. A circuit board on which a light-receiving element and a circuit section that drives the light-emitting element and detects floating particles in the detection space based on the light-receiving signal output from the light-receiving element are mounted together with the light-emitting element and the light-receiving element, and the circuit board is delivered. In a suspended particle detection device, the parts constituting the circuit section, the light-emitting element, and the light-receiving element are on opposite sides of the circuit board. The case has a pair of ventilation holes on both the front and back sides of the circuit board that allow outside air to flow into the case, and a flow path that passes through the detection space between the two ventilation holes is formed inside the case. .

[0007] In claim 2, the case includes a body that surrounds the periphery of the circuit board and is open on both the front and back sides of the circuit board, and a metal body that closes one opening of the body on the side of the circuit board on which the circuit section is mounted. and a second cover that closes the other opening of the body on the side of the circuit board where the light emitting element and the light receiving element are arranged, and the body and the second cover cover the entire surface of the conductive layer. The second cover is made of a material covered with an insulating layer made of synthetic resin, and the contact portion between the body and the second cover is welded by melting the insulating layer so that the conductive layers are electrically connected to each other. -ing

In claim 3, the case includes a body that surrounds the periphery of the circuit board and is open on both the front and back sides of the circuit board, and a metal body that closes one opening of the body on the side of the circuit board on which the circuit section is mounted. and a second cover that closes the other opening of the body on the side of the circuit board where the light emitting element and the light receiving element are arranged, and the body and the second cover are made of a conductive material filler. It is formed from a material filled with synthetic resin having insulating properties, and the body, first cover, and second cover are electrically connected to each other and to the ground line of the circuit section. be.

[0009]

According to the structure of claim 1, since the components constituting the circuit section, the light emitting element, and the light receiving element are arranged on opposite sides of the circuit board, the circuit section is on one side of the circuit board. Since there are no parts, by forming the detection space on this one side, the detection space can be widened. In addition, the case has a pair of airflow holes on both sides of the circuit board that allow outside air to flow into the case, and a flow path passing through the detection space is formed between the two airflow holes inside the case. Particulates can be made to flow between the two flow ports, and even when air is forced to flow, floating particulates can be detected by being placed on the air flow path. As described above, as a result of having a wide detection space and being able to set the detection space on the air flow path, a large amount of suspended particles can be introduced into the detection space, and suspended particles can be detected with high sensitivity. This is possible.

According to the second aspect of the present invention, the body surrounding the detection space and the second cover are formed of conductive members and are electrically connected to each other, so that noise such as electromagnetic waves is not transmitted to the light receiving element. It is possible to prevent light from entering from the outside, and it is possible to increase the signal-to-noise ratio of the circuit that processes the light-receiving signal output from the light-receiving element. In other words, this also leads to higher sensitivity.

According to the structure of claim 3, since the entire case is made of a conductive material and the case is electrically connected to the ground line of the circuit section, floating particles can be detected by charging the case. It is possible to prevent the light from adhering to the inner peripheral surface of the space, and it is possible to suppress the occurrence of malfunctions due to increase in stray light over time.

0012

[Example] (Example 1) As shown in Figures 1 to 3,
A light emitting element ED made of a light emitting diode and a light receiving element LD made of a photodiode are arranged in a rectangular parallelepiped-shaped case 1. The case 1 includes a rectangular frame-shaped body 10 made of synthetic resin and having two open sides facing each other, and a body 10.
The first cover 20 is made of metal and the second cover 30 is made of synthetic resin. A detection chamber 12 surrounded by a partition wall 11 is formed in the body 10 . Communication ports 21 and 31 are formed in the first cover 20 and the second cover 30, respectively, and both communication ports 21 and 31 are located on a straight line in a direction perpendicular to the opening surface. Among the partition walls 11 surrounding the detection chamber 12,
On the surface facing the first cover 20, a flow window 14 is opened at a portion corresponding to the flow port 21, and a rising wall 15 is formed around the periphery of the flow window 14. A step 16 is formed at the tip of the rising wall 15 to be inserted into the flow window 21. Therefore, the rising wall 15 functions as a spacer between the partition wall 11 and the first cover 20. A circuit board 4 is disposed in a space formed between the first cover 20 and the partition wall 11. A through hole 41 through which the upright wall 15 is inserted is bored in the circuit board 4 . A cylindrical spacer 42 is disposed between the circuit board 4 and the first cover 20, and the first cover 2
By screwing the assembly screw 22 inserted through the spacer 42 into the body 10, the first cover 2
0 is coupled to the body 10, and at the same time the circuit board 4 is fixed to the case 1. A light emitting element ED and a light receiving element LD are arranged on one surface of the circuit board 4 so as to face the detection chamber 12 .

The second cover 30 is formed with holders 32 and 33 that hold the light emitting element ED and the light receiving element LD, respectively. The holder 33 holding the light receiving element LD includes a plurality of light shielding plates 34 arranged in the optical axis direction to prevent light from entering the light receiving element LD from unnecessary directions. The second cover 30 has a plurality of (
4) locking claws 35 are provided protrudingly, and the locking claws 35 are attached to the body 1.
0, and the distal end engages with a locking hole 17 formed on the side surface of the body 10, and when the locking pawl 35 engages with the locking hole 17, the second cover 30 is adapted to be coupled to the body 10.

By the way, as shown in FIG. 2, in the detection chamber 12, a partition wall 18 is formed between the light emitting element ED and the light receiving element LD, and a notch 19 is formed in the partition wall 18 at a portion corresponding to the communication window 14. ing. This partition wall 18 prevents direct light from the light emitting element ED from entering the light receiving element LD. The light emitting element ED and the light receiving element LD are arranged in the upper part of the detection chamber 12 in FIG.
The side walls of are sloped so that the distance gradually decreases from the bottom to the top in FIG.

[0015] With the above structure, both flow ports 21
, 31, a flow path passing through the detection chamber 12 can be formed between the irradiation area of the light emitting element ED and the light receiving element LD.
It is possible to detect floating particles in the detection space that overlaps with the light-receiving area of the sensor. Incidentally, as shown in FIG. 4, the light emitting element ED is driven by an oscillation circuit 51 and a drive circuit 52 so as to be lit intermittently at approximately constant intervals.

On the other hand, the light reception signal, which is a current output corresponding to the amount of light received by the light receiving element LD, is converted into the amount of light received through a current-to-voltage conversion circuit 61 with a very high input impedance (approximately 100 MΩ) constructed using an operational amplifier circuit. converted to the corresponding voltage output. Thereafter, the received light signal converted into a voltage output passes through a bandpass filter 62 (50Hz to 10kHz), and is further clipped by a peak cut circuit 63 consisting of diodes connected in antiparallel to remove noise components. Ru.

After removing noise components from the light reception signal in this way, the light reception signal is transferred to the sample and hold circuit 64.
and based on the output of the oscillation circuit 51, the light emitting element ED
The received light signal is captured in synchronization with the lighting timing of the
The voltage value of the light reception signal is held until the next light reception signal is input. By the way, in this embodiment, a digital output section that outputs a binary signal corresponding to whether the concentration of suspended particles in the detection space is greater than or equal to a predetermined value or less than a predetermined value, and a continuous amount that corresponds to the concentration of suspended particles are provided. It also includes an analog output section for output.

The digital output section is composed of a comparator 65 that compares the output of the sample and hold circuit 64 with a reference voltage, and when the concentration of suspended particles is less than a predetermined value, the output is L level, and when it is above the predetermined value, the output is H level. It is set to be. On the other hand, the analog output section outputs the output of the sample hold circuit 64 and the reference voltage generation circuit 66.
It is equipped with a differential amplifier circuit 67 that performs correction by taking the difference with the reference voltage output from the differential amplifier circuit 67, and by amplifying the output of the differential amplifier circuit 67 with a DC amplifier circuit 68, a continuous output corresponding to the received light signal is generated. It is configured so that it can be obtained. The reference voltage generation circuit 66 includes a first reference voltage generation section 66a that divides the power supply voltage, and a second reference voltage generation section 66a that outputs a second reference voltage based on the first reference voltage output from the first reference voltage generation section 66a. It consists of a reference voltage generating section 66b. The second reference voltage is input to the differential amplifier circuit 67, and the first reference voltage is input to the DC amplifier circuit 68. Power is supplied to each of the above circuits by a power supply circuit 55 that makes DC input a constant voltage.

Here, among the parts constituting the circuit section, the parts other than the light emitting element ED and the light receiving element LD are surface mounted using chip parts as much as possible. Also,
The light emitting element ED, the light receiving element LD, and other components are arranged on opposite sides of the circuit board 4. That is, most of the components of the circuit section are arranged on the surface of the circuit board 4 facing the first cover 20. In this way, since almost no components other than the light emitting element ED and the light receiving element LD are mounted on the surface of the circuit board 4 on the detection chamber 12 side, a large space can be secured that can be used as the detection chamber 12. This increases the amount of outside air introduced into the detection chamber 12, making it possible to operate with high sensitivity.

The suspended particulate detection device A constructed as described above is used, for example, in an air cleaner as shown in FIG. This air purifier B has a fan 72 inside a housing 71.
It is configured such that air introduced from the front surface of the casing 71 is sent out from an air outlet 76 provided on the top surface of the casing 71. A front cover 73 is detachably attached to the front of the casing 71, and between the casing 71 and the front cover 73, a pair of filters 75a and 75 held by a filter holder 74 are provided.
5b is arranged. The filter 75a is provided to prevent large particles from entering the interior, and the filter 75b is provided to remove floating particles and odors. Here, the floating particle detection device A is arranged in the casing 71 so that a part of the air that has passed through the filter 75a is introduced into the floating particle detection device A. Further, the suspended particulate detection device A is arranged on the flow path to the fan 72 so that air is forced to circulate when the fan 72 is operated. According to such a configuration, after the fan 72 is operated, when the concentration of suspended particles detected by the suspended particle detection device A becomes equal to or less than a predetermined value, the fan 72 is activated, assuming that the air has been purified. Control such as automatic stopping becomes possible.

(Embodiment 2) By the way, since the light-receiving signal outputted from the light-receiving element LD is weak, a problem arises in that the signal-to-noise ratio decreases when electromagnetic waves or the like comes from outside. Therefore, in this embodiment, electromagnetic shielding is achieved by forming the body 10 and the second cover 30 using a conductive material.

That is, the body 10 and the second cover 30 are made of a conductive synthetic resin in which a filler such as short metal fibers or short carbon fibers is mixed into a base synthetic resin such as ABS or polystyrene. Figure 6(a)
), the conductive synthetic resin has a structure in which the entire surface of a conductive layer 2 having conductivity is covered with an insulating layer 3 made of a synthetic resin as a base.

By the way, in order to use the body 10 and the second cover 30 as an electromagnetic shield, it is necessary to make the conductive layers 2 of the body 10 and the second cover 30 the same potential, and as in the first embodiment, This requirement cannot be met simply by engaging the locking pawl 35 with the locking hole 17. That is, as shown in FIG. 6(b), the conductive layer 2 cannot be electrically connected due to the presence of the insulating layer 3. Therefore, in this embodiment, as shown in FIG.
A protrusion 13 having a triangular cross section is protruded over the entire circumference on the surface of the body 10 facing the second cover 30, and the insulating layer 3 is broken by melting the protrusion 13 by ultrasonic welding.
The conductive layer 2 is electrically connected as shown in FIG. 6(a). In this way, the body 10 and the second cover 30 can be joined without any gaps.

On the other hand, since the first cover 20 and the body 10 are connected by the assembly screws 22, if the body 10 is tapped and the metal assembly screws 22 are used, the first cover 20 and the body 10 can be connected together. It is possible to electrically connect the With the above configuration, the body 10, the first cover 20, and the second cover 30 can be electrically connected to each other to function as an electromagnetic shield, and the signal-to-noise ratio can be improved. be. Here, by electrically connecting the first cover 20 and the ground line provided on the circuit board 4, charging of the case 1 can be prevented, and floating particulates can be removed from the inner peripheral surface of the case 1. It is possible to suppress the increase in stray light caused by adhesion over time, and it is possible to prevent malfunctions over a long period of time. Other configurations are Example 1
Since it is the same as , the explanation will be omitted.

(Example 3) In Example 2, a conductive synthetic resin was used for the case 1, but in this example, as shown in FIG. It also has an antistatic effect. The conductive film 5 is formed by applying a conductive paint or plating a metal such as nickel or copper, and can be expected to have the same effect as when a conductive synthetic resin is used. The other configurations are the same as those in Example 1, so the explanation will be omitted.

[0026]

As described above, according to the structure of claim 1, the parts constituting the circuit section, the light emitting element, and the light receiving element are arranged on opposite sides of the circuit board. There are no circuit parts on one side, and by forming the sensing space on this one side, the sensing space can be made wider. In addition, the case has a pair of airflow holes on both sides of the circuit board that allow outside air to flow into the case, and a flow path passing through the detection space is formed between the two airflow holes inside the case. Particulates can be made to flow between the two flow ports, and even when air is forced to flow, floating particulates can be detected by being placed on the air flow path. As described above, as a result of having a wide detection space and being able to set the detection space on the air flow path, a large amount of suspended particles can be introduced into the detection space, and suspended particles can be detected with high sensitivity. This has the effect of making it possible to

According to the second aspect of the present invention, the body surrounding the detection space and the second cover are formed of conductive members and are electrically connected to each other, so that noises such as electromagnetic waves are not transmitted to the light receiving element. It is possible to prevent light from entering from the outside, and it is possible to increase the signal-to-noise ratio of the circuit that processes the light-receiving signal output from the light-receiving element. That is, this also has the advantage of leading to higher sensitivity.

According to the third aspect of the present invention, since the entire case is made of a conductive material and the case is electrically connected to the ground line of the circuit section, floating particles can be detected by charging the case. It is possible to prevent the light from adhering to the inner peripheral surface of the space, and it is possible to suppress the occurrence of malfunctions due to increase in stray light over time.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a first embodiment.

FIG. 2 is a front view showing the first embodiment with a second cover removed.

FIG. 3 is a longitudinal cross-sectional view showing Example 1.

FIG. 4 is a block diagram showing the first embodiment.

FIG. 5 is an exploded perspective view showing a usage pattern of Example 1.

FIG. 6(a) is a sectional view of a main part of Example 2, and FIG. 6(b) is a sectional view of a main part of a comparative example.

FIG. 7 is a cross-sectional view of the main part of Example 2 before processing.

FIG. 8 is a longitudinal cross-sectional view of Example 3.

FIG. 9 is an exploded perspective view showing a conventional example.

[Explanation of symbols]

1 Case 2 Conductive layer 3 Insulating layer 4 Circuit board 10 Body 20 First cover 21 Distribution port 30 Second cover 31 Distribution port 41 Through hole ED Light emitting element LD light receiving element

Claims (3)

[Claims] [Claim 1] A light emitting element that irradiates light into a detection space;
A light-receiving element that receives light scattered by floating particles among the light emitted from the light-emitting element, and a circuit that drives the light-emitting element and detects floating particles in the detection space based on the light reception signal output from the light-receiving element. A floating particle detection device comprising a circuit board mounted with a light-emitting element and a light-receiving element, and a case in which a detection space into which the circuit board is installed and into which floating particles are introduced is formed,
The components that make up the circuit section, the light emitting element, and the light receiving element are arranged on opposite sides of the circuit board, and the case has a pair of ventilation holes formed on both the front and back sides of the circuit board that allow outside air to flow into the case. A suspended particulate detection device characterized in that a flow path passing through a detection space is formed between both flow ports. 2. The case includes a body that surrounds the periphery of the circuit board and is open on both the front and back sides of the circuit board, and a metal first body that closes one opening of the body on the side of the circuit board on which the circuit section is mounted. and a second cover that closes the other opening of the body on the side of the circuit board where the light emitting element and the light receiving element are arranged, and the body and the second cover cover the entire surface of the conductive layer. The contact portion between the body and the second cover is formed by melting and welding the insulating layer so that the conductive layers are electrically connected to each other. The suspended particulate detection device according to claim 1, characterized by: 3. The case includes a body that surrounds the periphery of the circuit board and is open on both the front and back sides of the circuit board, and a metal first body that closes one opening of the body on the side of the circuit board on which the circuit section is mounted. and a second cover that closes the other opening of the body on the side of the circuit board where the light-emitting element and the light-receiving element are arranged. The body and the first
2. The suspended particulate detection device according to claim 1, wherein the cover and the second cover are electrically connected to each other and to a ground line of the circuit section.