JPH0477650A - Dust detector - Google Patents

Abstract

PURPOSE:To enable continuous measurement of dust in an exhaust within an exhaust duct with a high accuracy and in a highly stable manner by extracting components varying beyond a specified value in a microscopic time unit of a signal according to the quantity of light transmitted to be integrated over a specified time and then, to be compared with a specified value. CONSTITUTION:Light beam irradiated from a light emitter 10 is made to irradiate a light emitter 12 passing through a dust path 20 of a container 18 and a photocurrent is outputted. When a large amount of dust passes continuously through the dust path 20 caused by breakage of filter or the like, an output signal of a photo detector 12 changes rapidly in a microscopic time unit and the amplitude of the change is large. In this case, a signal level to be outputted from a rectifier circuit 65 via a differentiation circuit 64 always becomes large than a reference value e1 and the signal level to be outputted from an integration circuit 68 is also larger than a reference value e2. Abnormality is determined with a judging circuit 69 to be shown on a display means 70. This enables continuous measurement of dust with a high accuracy and in a highly stable manner in the exhaust within an exaust duct thereby achieving detection of abnormality of a dust condition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dust detection device, and in particular, it is used to continuously and accurately measure the amount of dust in the exhaust air in the exhaust duct of a factory, etc., and to detect whether the dust condition is abnormal. The present invention relates to a light transmission type dust detection device that determines whether or not the dust is present.

[Prior art and problems to be solved by the invention] Japanese Patent Application Laid-open No. 6
FIG. 4 of Japanese Patent No. 1-196140 discloses a principle diagram of a device for detecting dust using a light transmission type. This device has a light-emitting part and a light-receiving part installed facing each other on both sides of the flue through which dust passes, and prevents changes in light transmittance caused by dust blocking the optical path between the light-emitting part and the light-receiving part. It measures the concentration of dust. However, this device has the following problems. That is,
(1) Since the light emitting part and the light receiving part are separated, it is difficult to align the optical axis. (2) Optical axis misalignment is likely to occur due to thermal distortion and mechanical vibration of the flue, resulting in lack of stability.

(3) The surfaces of the optical lenses constituting the light emitting section, the light receiving section, etc. are easily contaminated by dust and lack long-term stability. (4
) The amount of light emitted by the light-emitting part and the light-receiving sensitivity of the light-receiving part are susceptible to changes depending on the environmental temperature, making it impossible to measure dust concentration with high precision.

In order to solve these problems, Japanese Patent Application Laid-Open No. 591366
Publication No. 39 discloses a light transmission type dust concentration measuring device that stabilizes the optical axis and prevents contamination of the optical lenses of the light emitting section and the light receiving section. In this device, a partition plate with pinholes is provided between the flue and the light emitting part and between the flue and the light receiving part to prevent contamination of the light emitting part and the light receiving part by dust. The air is blown out into the flue through a pinhole. Furthermore, by arranging the light emitting part and the light receiving part facing each other in a container with a dust passage formed in the center, and by integrating the light emitting part, the light receiving part, and the container, optical axis stability and ease of optical axis adjustment are ensured. are doing. In addition, in order to correct output fluctuations of the light emitting section due to temperature changes, this dust concentration measuring device uses a half mirror to irradiate the output of the light emitting section onto a separately provided reference light receiving section to correct output changes. It is disclosed that direct light from a light emitting part to a light receiving part and light scattered by dust are measured by different light receiving parts, and temperature changes in the output of the light emitting part are corrected by calculation. Such devices have the following problems. (1) Since the temperature of the light receiving section is not corrected, measurement instability occurs due to changes in sensitivity due to temperature changes in the light receiving section. (2)
The use of optical devices such as a plurality of light receiving units and half mirrors increases the complexity and instability of the device, and complicates the processing of optical output signals such as reference light measurement and calculation of direct light and scattered light.

In order to correct the sensitivity change due to temperature change of the light emitting part and the light receiving part, which is one of the drawbacks explained above, JP-A No. −
Japanese Patent No. 307641 discloses a powder density measuring device in which the temperatures of a light emitter and a light receiver are stabilized using a PTC thermistor which is a constant temperature heating element and has positive temperature characteristics, and a temperature sensor. This device uses PT as a heating element based on the temperature of the emitter and receiver measured by the temperature measuring element.
By feedback-controlling the operation of the C thermistor, the operating temperatures of the light emitter and light receiver are kept constant, and the temperature of the light emission output of the light emitter and the light receiving sensitivity of the light receiver is stabilized.

However, in this dust detection device, there is a limit to temperature stabilization due to the hysteresis characteristics of the feedback control circuit composed of a PTC thermistor and a temperature sensor.
The temperature of the light emitter and light receiver fluctuates by several degrees Celsius under normally used on/off control, and by about ±1 degree Celsius under PI (proportional/integral) control. With temperature stability at this level of accuracy, highly accurate dust measurement cannot be performed because an error occurs due to minute changes (1% or less) in light transmittance.

Furthermore, Japanese Patent Application Laid-open No. 61-221634 discloses that in a smoke amount detection device equipped with a light emitter and a light receiver, the peak value of the output signal of the light receiver is detected, and this is integrated with a long integration time constant. A reflection-type smoke amount detection device has been disclosed that detects only the change due to smoke by comparing the amount of smoke with a value determined by the amount of smoke.

This is a technology that detects only minute signal light due to smoke in an atmosphere of large amounts of unwanted reflected light, and has the feature of being able to eliminate changes in sensitivity due to deterioration of the emitter and receiver, changes in characteristics due to temperature, and contamination of the optical system. . However, in order to use this smoke amount detection device to detect only the signal light caused by smoke with high precision, it is necessary to set an optimal integration time constant according to the frequency component of the signal light, which results in a lack of versatility.

The present invention has been made in consideration of the above facts, and it is possible to continuously measure dust in the exhaust gas in the exhaust duct with high precision and high stability, and to determine whether or not the dust condition is abnormal. The aim is to obtain a dust detection device with excellent environmental resistance.

[Means to solve the problem]

In order to achieve the above object, a dust detection device according to the present invention includes a light emitting section and a light receiving section, and detects the state of the dust based on the amount of light irradiated from the light emitting section and detected by the light receiving section through the dust. A dust detection device for detecting dust, comprising an extracting means for extracting a fluctuation component that fluctuates by a predetermined value or more in a minute time unit of a signal according to the amount of light output from the light receiving section, and a fluctuating component extracted by the extraction means. It has a calculating means that integrates or integrates over a predetermined time, and a determining means that compares the calculation result of the calculating means with a predetermined value and determines whether or not the dust condition is abnormal. It is characterized by

[Effect]

Dust that passes through a duct such as a chimney is unevenly distributed in the duct due to uneven dust particle size and turbulent airflow within the duct, resulting in uneven distribution between the light emitting part and the light receiving part. The amount of dust passing through the optical path between and changes randomly. Along with this, the inventors have confirmed through experiments that the amount of transmitted light that is emitted from the light emitting part, passes through the dust, and is detected by the light receiving part fluctuates by a predetermined value or more in minute time units, as shown in Figure 1. ing. Note that if there is no dust on the optical path between the light emitting section and the light receiving section, the signal output from the light receiving section will be at a constant level. A similar change also occurs when detecting light reflected by dust.

Therefore, in the present invention, a fluctuation component that fluctuates by a predetermined value or more in a minute time unit of a signal corresponding to the amount of light output from the light receiving section is regarded as a fluctuation due to dust, and is extracted by the extraction means. For example, when the signal output from the light receiving section changes gradually due to changes in the environment such as temperature changes, contamination, and deterioration of the light emitting section and the light receiving section, the amount of fluctuation in the minute time unit of the signal is extremely small and is less than a predetermined value. The signal output from the extraction means is not affected. Therefore, only the fluctuation components due to dust can be extracted without being affected by changes in the environment. A method for extracting fluctuation components that fluctuate by a predetermined value or more in minute time units is to pass the signal output from the light receiving section through a differentiating circuit with a small time constant, and then extract signal components whose amplitude is a predetermined value or more. Alternatively, it can be performed by sampling the signal at minute intervals, calculating the difference, that is, the rate of change, and then extracting the signal component having a rate of change equal to or higher than a predetermined value.

The fluctuation component extracted by the extraction means is integrated or integrated over a predetermined time by the calculation means. The calculation result of the calculation means is compared with a predetermined value in the determination means to determine whether or not the dust condition is abnormal. For example, during dust removal operation when performing maintenance on the filter of a dust collector,
For dust that is emitted instantaneously, the value extracted by the extraction means changes temporarily as shown by arrow A in FIG. Since the resulting values are averaged over a predetermined period of time, the change is reduced, so that the dust condition is not determined to be abnormal.

However, since the dust emitted when the filter is damaged is continuously emitted, even in small amounts, it is reflected in the calculation results and can be accurately determined as an abnormality, making it possible to perform highly accurate measurements.

Furthermore, as described above, since it is not affected by environmental changes such as temperature changes, continuous measurements can be performed stably over a long period of time.

As described above, in the present invention, gradual fluctuations in the photoreceiver output signal over a long period of time due to changes in the environment can be resolved by extracting fluctuation components of the signal that fluctuate by a predetermined value or more in minute time units in the extraction means. On the other hand, temporary fluctuations due to dust removal operations, etc. are averaged by integrating or accumulating the extracted fluctuation components over a predetermined time in the calculation means and judgment means, and are substantially smaller than the predetermined value. It is removed by setting it to a value. As a result, the determining means accurately outputs only a signal that reflects the abnormal dust state that constantly and randomly fluctuates over a predetermined period of time.

〔Example〕

First example A first embodiment of the present invention will be described below with reference to the drawings.

In addition, although the following examples are explained using numerical values that do not hinder the present invention, the present invention is not limited to the following numerical values.

As shown in FIG. 2, the dust detection device of this embodiment includes a light emitter 10 equipped with a light emitting element made of a light emitting diode (LED), and a light receiver 12 equipped with a light receiving element made of a photodiode (PD). , a container 18 in which a light emitter 10 and a light receiver 12 are integrally fixed so as to face each other, and a dust passage 20 is formed on an optical axis 28 connecting the light emitter 10 and the light receiver 12. There is. This container 18 is arranged such that a dust passage 20 is located in an exhaust duct 22 connected to a dust collector.

The cathode and anode of the light emitting diode of the light emitter 10 are connected to the LED drive circuit 61 of the control device 60,
The light emitter 10 emits a constant amount of light toward the light receiver 12 by the LED drive circuit 61. The cathode and anode of the photodiode of the photoreceiver 12 are connected to the input terminal of a current amplification circuit 62 of the control device 60 . Receiver 1
2 receives the light beam emitted from the light emitter 10 and transmitted through the dust, and outputs a signal corresponding to the amount of the light beam to the current amplification circuit 62. The current amplification circuit 62 amplifies the signal output from the light receiver 12. The output terminal of the current amplification circuit 62 is connected to the input terminal of a differentiating circuit 64 that constitutes a part of the extraction means 63. In the differentiating circuit 64, the values of each element are set so that the time constant is small (eg, 1 second or less). Therefore, the signal output from the differentiating circuit 64 is a signal obtained by extracting the minute time unit fluctuation component of the signal output from the current amplification circuit 62.

The output terminal of the differentiator circuit 64 is connected to the input terminal of the rectifier circuit 65. The rectifier circuit 65 performs full-wave rectification on the signal output from the differentiating circuit 64 and outputs the resultant signal.

The output terminal of the rectifier circuit 65 is connected to one of the two input terminals of the comparator circuit 67. The reference value e1 is manually input to the other of the two input terminals of the comparison circuit 67. Comparison circuit 67
compares the signal output from the rectifier circuit 65 with a reference value e1, and outputs a signal component greater than or equal to the reference value e1, that is, a fluctuation component that fluctuates by a predetermined value or more in minute time units as a signal due to dust.

The output terminal of the comparator circuit 67 is an integrator circuit 68 which is an arithmetic means.
is connected to the input terminal of The values of each element of the integrating circuit 68 are set so that the time constant is large (for example, 5 minutes to 10 minutes). The integrating circuit integrates the output signal of the comparing circuit 67 over a fixed time corresponding to a time constant and outputs the result as a signal. Therefore, the level of the signal output from the integrating circuit 68 corresponds to the amount of dust within a certain period of time corresponding to the time constant.

The output terminal of the integrating circuit 68 is connected to one of the two input terminals of a comparison/determination circuit 69 which is a determination means. The reference value e2 is input to the other of the two input terminals of the comparison/judgment circuit 69. Further, a display means 70 including a lamp, a buzzer, etc. is connected to the output terminal of the comparison/judgment circuit 69.

The comparison/determination circuit 69 compares the signal output from the integration circuit 68 with a reference value e2, and determines that the dust condition is normal when the level of the output signal of the integration circuit 68 is less than the reference value 02, and also outputs the output signal. It is determined that the dust condition is abnormal when the level of the dust is higher than the reference value. Comparison judgment circuit 6
The determination result of step 9 is output to the display means 70, and if the determination result is abnormal, a warning is output.

Next, the operation of the first embodiment will be explained.

The light beam emitted from the light emitter 10 passes through the dust passage 20 of the container 18 and is irradiated onto the light receiver 12, and the light receiver 12 outputs a photocurrent. Therefore, the emitter IO and the receiver 1
Since the transmittance of this optical path changes when dust passes through the optical path between the two and blocks the light beam, the photocurrent (output signal) of the light receiver 12 changes.

For example, if there is no dust passing through the dust passage 20,
As shown in Figure (A), the output signal of the light receiver 12 is a constant value V. becomes. In this case, the output signal of the differentiating circuit 64 is always 0, and a fluctuation component that fluctuates by more than the reference value 61 in minute time units is not extracted.

When a small amount of dust is passing through the dust passage 20, the output signal of the light receiver 12 is a constant value V, as shown in FIG. 3(B), for example. fluctuates in minute time units at a level lower than . In this case, the differentiating circuit 64 outputs a signal corresponding to the fluctuation. However, since the amount of dust passing through the dust passage 20 is small, the amplitude α of the fluctuation in the output signal of the light receiver 12 is small, and similarly to the above, the fluctuation component is not extracted.

In addition, when dust is temporarily or instantaneously discharged by the dust removal operation of the filter of the dust collector, the output signal of the light receiver 12 temporarily becomes large, as shown by arrow A in FIG. 3(C), for example. fluctuate. As a result, the signal level output from the rectifier circuit 65 via the differentiating circuit 64 temporarily becomes higher than the reference value e1, but since the time constant of the integrating circuit 68 is increased, the signal level output from the integrating circuit 68 The level of dust is averaged to a small level, and the dust condition is determined to be normal.

If a large amount of dust continues to pass through the dust passage 20 due to damage to the filter, etc., the output signal of the light receiver 12 will fluctuate drastically in minute time units, as shown in FIG. 3(D), for example. , and the amplitude α of the fluctuation is large. In such a case, the signal level output from the rectifier circuit 65 via the differentiating circuit 64 will always be higher than the reference value e1, and the signal level output from the integrating circuit 68 will also be higher than the reference value e2, so the comparison judgment The circuit 69 determines that the dust condition is abnormal, and a warning message or the like is displayed on the display means 70.

In addition, if a large amount of fine dust with a small particle size continues to pass through the dust passage 20, as shown in FIG. 3(E), for example.
As shown in FIG. 2, the output signal of the light receiver 12 has a large number of fluctuations in minute time units, and the amplitude α of the fluctuations also becomes large.

In such a case, the amplitude α of the output signal of the optical receiver 12 is
If the signal level output from the rectifier circuit 65 via the differentiating circuit 64 exceeds the reference value e1, the integration result (signal level output from the integrating circuit 68) will be large due to the large number of fluctuations. The dust condition is determined to be abnormal. Therefore, even minute dust can be detected with high precision.

When there is a temperature change in the light emitter 10 and the light receiver 12, the output signal of the light receiver 12 changes gradually, as shown in FIG. 3(F), for example. Here, the time constant of the integration is
By increasing the amount proportionally according to the amount of dust emitted during dust removal operation, it is possible to perform appropriate averaging processing of the integral value regardless of the amount of dust, and only dust abnormalities can be detected. Can be accurately determined. In this way, if the output signal of the photodetector 12 changes slowly over a sufficiently large time period with respect to the time constant of the differentiating circuit 64, it will not affect the output signal of the differentiating circuit 64, so it may be mistakenly assumed that the dust condition is abnormal. There is no judgment. This is a light emitter 10, a light receiver 1
The same applies to changes over time such as contamination of the second optical system, deterioration of the light emitter 10 and the light receiver, etc.

In this way, in the first embodiment, the differential circuit 64 performs differentiation and extracts minute time unit fluctuation components by regarding them as fluctuations due to dust. Contamination, emitter 10 and receiver 1
Dust can be detected stably over a long period of time without being affected by environmental changes such as deterioration of the dust.

In addition, in the first embodiment, since the integration circuit 68 performs integration over a period of time according to the time constant, the integral value is not correct for dust that is temporarily and instantaneously discharged by a dust removal operation, etc. The dust state is not determined to be abnormal due to averaging, and only dust caused by damage to the filter or the like can be accurately detected.

In the first embodiment, the rectifier circuit 65 performed full-wave rectification, but it is only necessary to detect the portion of the signal output from the differentiator circuit 64 that corresponds to the variation due to dust.
For example, half-wave rectification or the like may be performed.

Second Embodiment A second embodiment of the present invention will be described below. Note that the same parts as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, in the second embodiment, the output terminal of the current amplification circuit 62 is connected to each input terminal of sample and hold circuits 72 and 73 forming a part of the extraction means 71. The sample and hold circuits 72 and 73 have a fifth
The output signal of the light receiver 12 as shown in FIG.

On the other hand, the extraction means 71 includes an oscillation circuit 74, and the oscillation circuit 74 outputs a gate signal G, which is a pulse with a constant period as shown in FIG. 5(B). An output terminal of the oscillation circuit 74 is connected to an input terminal of a timing pulse generation circuit 75. The timing pulse generation circuit 75 has two output terminals, and one output terminal outputs the gate signal G.
The sampling signal S, synchronized with the rising edge of gate signal G (see FIG. 5 (C)) is output, and the sampling signal S2 synchronized with the falling edge of gate signal G (see FIG. 5 (E)) is output from the other output terminal. Output. The two output terminals of the timing pulse generation circuit 75 are connected to a sample hold circuit 72.
It is connected to the synchronization signal input terminal of 73.

The sample and hold circuit 72 samples the output signal of the light receiver 12 in synchronization with the rise of the sampling signal SI input from the synchronization signal input terminal, and outputs a signal v1 that holds the output signal level at the time of sampling. . Therefore, as shown in FIG. 5 (D>), the level of the signal v1 changes stepwise.The sample and hold circuit 73 receives light in synchronization with the fall of the sampling signal S2 inputted from the synchronization signal input terminal. It samples the output signal of the device 12 and outputs a signal v2 that holds the output signal level at the time of sampling.
As shown in Figure (F), the level of the signal v2 changes in a stepwise manner similar to the signal v. Therefore, the sample and hold circuits 72 and 73 operate alternately every pulse of the gate signal G to perform sampling.

The output terminal of the sample hold circuit 72 is connected to the gate circuit 76.
is connected to the output terminal of The gate signal G of the oscillation circuit 74 is input to the synchronization signal input terminal of the gate circuit 76 . Further, the output terminal of the sample hold circuit 73 is connected to the output terminal of the gate circuit 77. The gate signal G is also input manually to the synchronization signal input terminal of the gate circuit 77.

The gate circuits 76 and 77 allow the human input signal v1 or v2 to pass only when the gate signal G is on (level 1).

The output terminal of the gate circuit 76 is connected to one of the two input terminals of the differential circuit 78, and the output terminal of the gate circuit 77 is connected to the other input terminal of the differential circuit 78. The differential circuit 78 outputs the difference v, -v2 (denoted as ΔV) between the two input signals v1 and v2, as shown in FIG. 5(G). The output terminal of the differential circuit 78 is connected to the input terminal of the absolute value calculation circuit 79. The absolute value calculation circuit 79 calculates the absolute value 1Δv1 of the input signal ΔV and outputs a signal K·1Δv1 amplified by an amplification factor.

The output terminal of the absolute value calculation circuit 79 is connected to one of the two input terminals of a comparison circuit 67 similar to the first embodiment.

The reference value e3 is input to the other of the two input terminals of the comparison circuit 67. The comparison circuit 67 compares the signal K·ΔV outputted from the absolute value calculation circuit 79 with the reference value e3, and detects the signal component of the reference value 03 or more, that is, the fluctuation component that fluctuates by a predetermined value or more in minute time units, due to dust. Output as a signal.

The output terminal of the comparison circuit 67 is connected to the input terminal of an integration circuit 80 provided in place of the integration circuit 68 of the first embodiment. The integration circuit 80 integrates the signal output from the comparison circuit 67 over a predetermined period of time (approximately 5 minutes to 10 minutes) and outputs the result. The integration circuit 80 is connected to one of the two input terminals of the comparison/judgment circuit 69 as in the first embodiment. The comparison/judgment circuit 69 uses the input integration result as the reference value e4.
Determine whether it is larger than . If the integration result is less than or equal to the reference value e4, it is determined that the dust condition is normal, and if the integration result is greater than the reference value, it is determined that the dust condition is abnormal. The comparison judgment circuit 690 judgment result is displayed on the display means 70.
Output to. In the second embodiment, the display means 70 is a lamp, which is turned on when it is determined that there is an abnormality.

Next, the operation of the second embodiment will be explained.

In the second embodiment, the difference between the output signals of the light receiver 12 is calculated for each pulse of the gate signal, that is, in minute time units, the absolute value of the calculation result is amplified in the absolute value calculation circuit 79, and the absolute value of the calculation result is amplified in the comparison circuit 67. A fluctuation component that fluctuates by a predetermined value or more is used as an output signal of the extraction means 71. Therefore, the output signal of the extraction means 71 of the second embodiment is the same as that of the extraction means 6 of the first embodiment.
Similarly to the signal output from the light receiver 3, this corresponds to a fluctuation component due to dust in the output signal of the light receiver 12. For example, when there is no dust in the dust passage 20, the ΔV is always zero, so the output signal K·1Δv1 of the extraction means 71 is also zero. When dust is passing through the dust passage 20, the above Δ
The value of V increases or decreases depending on the amount of dust. light emitter 10,
The output signal is not affected by gradual changes such as temperature changes in the light receiver 12 or contamination of the optical system because the changes in minute time units are minute.

Furthermore, in the second embodiment, the signal output from the extraction means 71 is integrated over a predetermined time by the integration circuit 80, and this integration corresponds to the integration by the integration circuit 68 in the first embodiment. For example, when dust is temporarily or instantaneously discharged by a dust removal operation, the integrated value by the integration circuit 80 does not increase significantly, so the comparison/determination circuit 69 does not determine that the dust condition is abnormal. In addition, if a large amount of dust is continuously emitted due to filter damage, etc.
When the integrated value by the integrating circuit 80 becomes sufficiently large, the comparison/determination circuit 69 determines that the dust condition is abnormal.

Third Embodiment Next, a third embodiment of the present invention will be described. Note that the same parts as in the first embodiment and the second embodiment are denoted by the same reference numerals.
The explanation will be omitted.

As shown in FIG. 6, a plurality of partition plates 26 each having a pinhole 24 in the center are arranged between the light emitter 10 and the dust passage 20 and between the light receiver 12 and the dust passage 20. has been done. These partition plates 26 are arranged so that an optical axis 28 connecting the light emitter 10 and the light receiver 12 passes through the center of the pinhole 24. The light emitter IO is fixedly arranged within the heat insulating case 14 that constitutes the temperature controller 46, and is held integrally with the container 18 by the heat insulating case 14.

Further, the light receiver 12 is similarly fixedly arranged within the heat insulating case 16 that constitutes the temperature controller 48, and is held integrally with the container 18 by the heat insulating case 16. Inlet ports 36 are formed in the vicinity of the light emitter 10 and the receiver 12 of the container 18, respectively, and these inlets 36 are used to supply air such as factory air through piping, an air filter 34, and a pressure reducing valve 32. connected to the source.

As shown in FIG.
The light receiver 12 is connected to the D drive circuit 61 , and the light receiver 12 is connected to the current amplification circuit 62 of the control device 82 . The temperature controller 46 also detects the temperature inside the insulation case 14 and a heater 52 configured of a constant temperature heating element such as a PTC thermistor for heating the light emitting device 10 fixedly held within the insulation case 14. Temperature measuring element 50 composed of a thermistor etc.
It is equipped with. Heat generated from the heater 52 is transmitted to the light emitting device 10 via a heat transfer plate (not shown), and the light emitting device 10 is heated. Further, the temperature measuring element 50 measures the temperature inside the heat insulating material case 14. Note that the temperature controller 48 also includes a heater 56 and a temperature measuring element 54 similarly to the temperature controller 46.

The heater 52 is connected to a switch circuit 83 that is configured with a relay or the like and turns the heater 52 on and off. Heater 56
is connected to the switch circuit 84. switch circuit 8
3.84 is connected to a microcomputer 85 and its operation is controlled by the microcomputer 85. Also,
The temperature measuring element 50 and the temperature measuring element 54 are also connected to the microcomputer 85. The microcomputer 85 is
Insulating material case 14 based on the output of temperature measuring element 50.54
．． A switch circuit 83 determines whether the temperature inside the heater 52.56 has reached a preset temperature, cuts off power to the heater 52.56 when the temperature has reached a preset temperature, and supplies power to the heater 52.56 when the temperature has not reached the preset temperature. .84 control.

The output terminal of the current amplification circuit 62 is connected to the input terminal of a gain adjustment circuit 86. The gain adjustment circuit 86 stores in advance the transmitted light signal level when the light transmittance is 100% when the dust detection device is initially installed in the exhaust duct as a reference level, and the received light output from the current amplification circuit 62. In order to express the transmitted light signal of the device 12 as a light transmittance, the level of the output signal is adjusted to a level corresponding to the light transmittance with the reference level as 100%.

A transmittance display section 87 and an AD conversion circuit 88 are connected to the output terminal of the gain adjustment circuit 86 .

The transmittance display unit 87 converts the signal output from the gain adjustment circuit 86 into a light transmittance and displays it in percentage on a liquid crystal display or a meter. Further, the output terminal of the AD conversion circuit 88 is connected to the microcomputer 85,
The light transmission signal output from the gain adjustment circuit 86 is converted into a digital signal and output to the microcomputer 85.

The microcomputer 85 extracts the extraction means 71 of the second embodiment based on the signal input from the AD conversion circuit 88.
It is determined whether or not the dust condition is abnormal based on an algorithm that operates in the same way as the integration circuit 80 and the comparison and determination circuit 69. A key switch 89 for data input and settings is connected to the microcomputer 85. key switch 89
inputs into the microcomputer 85 determination reference values for making each determination. Also, microcomputer 85
includes a display section 91 such as a liquid crystal display that displays the processing results of the microcomputer 85, and a notification means 90 that notifies the worker of abnormalities in the dust condition determined by the microcomputer 85, for example by lighting or blinking a lamp. , an alarm circuit 92 is connected that outputs an alarm signal for stopping machine tools, etc. in the factory in the event of abnormal dust conditions.

Next, the operation of the third embodiment will be explained.

Factory air is made into low-pressure clean air by passing through a pressure reducing valve 32 that reduces the air pressure and an air filter 34 that removes water and oil from the air.
6 into the container 18. This clean air flows out in the direction of the dust passage 20 through the pinhole 24 of the partition plate 26, and the dust is scattered from the dust passage 20 in the direction of the light emitter 10 and the light receiver 12. It can prevent it from sticking and getting dirty.

The microcomputer 85 turns on the switch circuit 83 to supply power to the heater 52, causing the heater 52 to generate heat to heat the light emitter 10 and the light receiver 12. The temperature inside the insulation case 14 is measured by the temperature measurement element 50, and the microcomputer 85 compares the temperature measured by the temperature measurement element 50 with a preset temperature.
When the temperature inside the heater 52 reaches the set temperature, the switch circuit 83 is turned off to cut off the power supply to the heater 52. By repeating the above operations, the temperature inside the heat insulating case 14 is maintained at a constant temperature. Further, the temperature inside the heat insulating case 16 that houses the light receiver 12 is also controlled by the microcomputer 85 by turning on and off the switch circuit 84 in the same manner as described above. Therefore, the operating temperatures of the light emitter 10 and the light receiver 12 housed in the heat insulating case are maintained constant, and temperature stabilization of the light emitting output or light receiving sensitivity can be easily achieved.

The transmitted light signal from the light receiver 12 is adjusted by a gain adjustment circuit 86 to a level corresponding to the light transmittance, and the light transmittance is expressed as %.
It is displayed on the transmittance display section 87. Therefore, if there is no dust in the dust passage 20 and the transmittance displayed on the transmittance display section 87 is not 100%, it is determined that a problem such as deterioration of the light emitter 10 and the light receiver 12 has occurred. can. Therefore, it is possible to determine the timing of maintenance, etc. from the transmittance displayed on the transmittance display section 87.

Next, the process of determining the dust state by the microcomputer 85 will be explained with reference to the flowchart of FIG.

In step 100, key switch 89, temperature controller 46.4
8. Determine whether the interface with peripheral equipment such as an air supply source is normal. In the third embodiment, the microcomputer 85 has a function of checking peripheral devices and the like. If it is determined that the interface is not normal, it is determined that a failure has occurred in the interface with the peripheral device or the peripheral device itself, and the process moves to step 122. If it is determined that the interface is normal, in step 102, the setting values for determining abnormal dust, etc. input from the key switch 89 are checked and displayed on the display unit 91 or the like.

In the next step 104, it is determined whether the temperature control by the temperature regulators 46, 48 is normal. Whether this is normal or not can be determined based on whether the temperature inside the heat insulating material case 14, 16 is close to the set temperature or significantly deviates from the set temperature. If it is determined that the temperature control is normal, the process moves to step 108. If it is determined that the temperature control is not normal, it is determined in step 106 whether or not the heaters 52, 56 are in a preheating state or in preparation for heating. If it is determined that the heating preparation is not in progress, the temperature controller 4
It is determined that a failure has occurred at 6.48, and the process moves to step 122. If it is determined that heating preparation is in progress, the process moves to step 108.

In step 108, the digital light transmittance signal output from the AD conversion circuit 88 is taken in. In step 110, it is determined whether the transmittance value is within a permissible range. This permissible range is determined to prevent failures due to manual input of signals of excessive levels to each device, and if the permissible range is outside the permissible range, the process moves to step 122. If it is within the allowable range, the change in the light transmittance signal is extracted in step 112. That is, the microcomputer 85 stores the previously captured light transmittance signal, calculates the difference ΔV between the previously captured light transmittance signal and the currently captured light transmittance signal, and calculates the absolute value 1 of this difference ΔV. Calculate ΔV1 as the amount of change. In the next step 114, it is determined whether this amount of change is smaller than a reference value set by the key switch 89 or the like. If the amount of change is larger than the reference value, the amount of change is integrated in step I56 and stored in the integration rear, and the process proceeds to step 122. If the amount of change is smaller than the set value, the amount of change is offset as O in step 118, and the process proceeds to step 120.

On the other hand, in step 122, the alarm target determined to be abnormal is checked against the alarm determination conditions. Targets of this alarm include abnormalities in interfaces, failures in peripheral devices such as air supply sources, failures in temperature controllers, and abnormalities in dust conditions. For example, if the determination in step 114 is negative and it is determined that the amount of change is greater than or equal to the reference value, the integration result in step 116 is compared with the reference value corresponding to abnormal dust.

In step 124, it is determined whether or not to output an alarm based on the collated alarm determination conditions. If it is determined that there is no need to output an alarm, the process moves to step 120. If it is determined that it is necessary to output an alarm, the notification means 90 is activated in step 126 to notify the worker of the abnormality, and the alarm circuit 92 outputs an alarm signal, and the process proceeds to step 120. do.

In step 120, the processing data and self-check results are output and displayed by the display unit 91, and step 100 is performed.
Return to

Note that the processing from step 100 to step 120 is repeatedly performed in minute time units, for example, in a time period of 0.1 to 1 second. Therefore, in step 112, the fluctuation component due to dust, that is, the fluctuation in the transmittance signal in minute time units is extracted, and in step 116, the fluctuation components that fluctuate by more than a reference value in minute time units are integrated. Therefore, by comparing and determining the integration result in step 116 with the reference value, it is possible to accurately determine only the abnormal dust state.

In this way, in the third embodiment, since the operating temperatures of the light emitter 10 and the light receiver 12 are kept constant,
The light emission output of the light emitter 10 and the light receiving sensitivity of the light receiver 12 can be stabilized without being affected by environmental temperature changes.

Therefore, since it is possible to measure the absolute value of the light transmittance, it is possible to accurately know the dust concentration, which is proportional to the light transmittance.

Furthermore, in the third embodiment, in order to extract minute time unit fluctuation components of the light transmittance signal, it is necessary to extract long-period fluctuation components included in the light transmittance signal due to temperature control of the light emitter and light receiver. It is possible to extract only the light transmission fast component that randomly fluctuates due to dust, without being affected by temperature control fluctuations or spike noise mixed in from the outside.

Note that the microcomputer 85 of the third embodiment has the extraction means 71, the integration circuit 80, and the comparison/judgment circuit 6 of the second embodiment.
9, it was determined whether the dust condition is abnormal or not based on an algorithm that operates similarly to 9, but the extraction means 63, the integrating circuit 68, and the comparison/judgment circuit 69 operate in the same manner as in the first embodiment. It may be determined whether the dust condition is abnormal based on an algorithm.

〔Effect of the invention〕

As explained above, in the present invention, a fluctuation component that fluctuates by a predetermined value or more in a minute time unit of a signal corresponding to the amount of transmitted light is extracted, integrated or accumulated over a predetermined time, and the calculation result is calculated by a predetermined value. Since it is decided whether the dust condition is abnormal or not by comparing it with It has the excellent effect of being able to determine.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the present invention in detail, Fig. 2 is a schematic configuration diagram of a dust detection device according to the first embodiment, and Figs. 3 (A) to (F) show output signals of the light receiver. Diagram, Figure 4 is the second
A schematic configuration diagram of the dust detection device of the embodiment, FIG. 5 (A> to (H)) is a diagram showing the output signal of each circuit of the second embodiment, and FIG. 6 is a diagram of the dust detection device of the third embodiment. 7 is a schematic block diagram of the control device shown in FIG. 6, and FIG. 8 is a flowchart explaining the operation of the control device shown in FIG. 6. 10... light emitter, 12... light receiver 60.82...Control device, 63.71...Extraction means, 64...Differential circuit, 68...Integrator circuit, 69...Comparison/judgment circuit, 78...Differential circuit, 80... Integration circuit, 85... Microcomputer.

Claims (1)

[Claims] (1) A dust detection device that includes a light emitting part and a light receiving part, and detects the state of the dust based on the amount of light irradiated from the light emitting part and detected by the light receiving part through the dust. Extracting means for extracting a fluctuation component that fluctuates by a predetermined value or more in minute time units of a signal corresponding to the amount of light to be output;
a calculation means for integrating or accumulating the fluctuation component extracted by the extraction means over a predetermined time; and a calculation means for comparing the calculation result of the calculation means with a predetermined value to determine whether the dust condition is abnormal. A dust detection device characterized by having a determination means for determining.