JPH0260262B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a device for detecting the concentration of dust in the air, and more particularly to a device for detecting the concentration of dust using a light scattering type dust detector. It is.

Conventional technology As is well known, air conditioning is a system that purifies air, controls temperature,
The purpose of this is to adjust the humidity and keep the air condition suitable for the purpose of use. Therefore, if there is a large gap between the current air condition and the desired air condition, the processing air volume should be increased and Conversely, if the gap is small, the processing air volume is usually reduced. For example, when removing dust for air purification, conventionally, the concentration of dust contained in the air is detected and the processing air volume is changed depending on the dust concentration. FIG. 2 shows a conventional example of a device for this purpose, in which an exhaust unit 2 with a built-in filter 1 is interposed in the middle of an exhaust duct 3, and a variable air volume type exhaust fan is installed downstream of the exhaust unit 2. 4 is provided. In the exhaust unit 2, a suction pipe 5 is arranged to open in a direction perpendicular to the air flow on the upstream side of the filter 1, and a light scattering type dust detection system that samples the air with an attraction fan 6 is used. A vacuum chamber 7 is connected to the exhaust unit 2 via the suction pipe 5. Based on the output signal of the dust detector 7, the air volume by the exhaust fan 4 is adjusted. That is, when the air sampled by the attraction fan 6 flows into the dust detector 7, the laser light in the dust detector 7 is scattered by the dust contained in the air.
When the dust concentration is high, the proportion of scattered light is high and the proportion of straight light is low, so the output signal associated with this increases the air volume by the exhaust fan 4, and conversely, the dust concentration is low. in case of,
Since the proportion of scattered light is low and the proportion of straight light is high, the air volume by the exhaust fan 4 is reduced based on the output signal of the dust detector 7.

Problems to be Solved by the Invention By the way, a light scattering type dust detector operates according to the amount of dust flowing into its interior, so in order to detect the dust concentration, it is necessary to keep the amount of air flowing in constant. It is necessary to maintain the suction tube 5.
As mentioned above, the opening is perpendicular to the exhaust flow to avoid the influence of the dynamic pressure of the exhaust. However, the output of exhaust fans in air conditioning equipment is determined by the volume of the building in question.
In general, they have a large air volume of several hundred to several hundred ^m3 /min, and the air volume adjustment range is from several tens of percent to 100 m3/min.
%, the flow velocity within the exhaust duct varies greatly, and depending on the state of clogging of the filter 1, the pressure at the upstream side of the filter 1, that is, at the open end of the suction pipe 5 may vary. fluctuations occur;
In addition to this, 6 attraction fans for sampling
Since this is a small capacity device with an air flow rate of about several minutes per minute, the amount of air flowing into the dust detector 7 will change even if the suction pipe 5 is installed to avoid the dynamic pressure of the exhaust.

The conventional device described above does not have a means to suppress such fluctuations in the amount of air flowing into the dust detector 7, so even though the dust concentration is low, the amount of air exhausted by the exhaust fan 4 increases and becomes excessive. Even though the dust concentration is high, the detected value by the dust detector 7 is low because the sampling air volume is small, and the exhaust air volume by the exhaust fan 4 decreases, resulting in a reduction in air purification. There was a problem that made it impossible to do this properly.

In view of the above circumstances, an object of the present invention is to provide a dust concentration detection device that eliminates the influence of the flow state of dust-containing air, can accurately detect dust concentration, and furthermore enables proper operation of air conditioning equipment. It is something to do.

Means for Solving the Problems In order to achieve the above object, the present invention arranges a suction pipe that opens in a direction perpendicular to the streamline of the dust-containing air flow, and the suction pipe is communicated with a buffer chamber having an open part, and a first attraction fan for sucking the dust-containing air is interposed in the middle of the suction pipe, and a light scattering dust detector is communicated with the buffer chamber, A second attraction fan is provided to supply dust-containing air from the buffer chamber to the light scattering dust detector, and the air volume of the first attraction fan is set to be larger than the air volume of the second attraction fan. It is something.

In other words, in the device of the present invention, dust-containing air in an amount greater than the amount of air supplied to the dust detector is sampled by the first attraction fan, and the suction pipe is connected to a buffer chamber having an open portion. Therefore, the excess of the sampled dust-containing air flows out from the opening, and the dust detector is supplied with a certain amount of dust-containing air sucked from the buffer chamber by the second induction fan. . If the flow velocity or static pressure of the dust-containing air flow fluctuates, the amount supplied to the buffer chamber by the first induction fan will fluctuate, but as the amount of supply increases, the amount of leakage from the open section will increase. Furthermore, if the supply amount decreases, the amount of leakage from the opening will decrease, and thus the pressure fluctuation within the buffer chamber will decrease. Therefore, the second induction fan sucks dust-containing air from the buffer chamber whose pressure is almost constant at all times and supplies it to the dust detector, and as a result, the amount of sampling air to the dust detector becomes stable. , dust concentration can be detected accurately.

Embodiment Next, an embodiment of the present invention will be described with reference to FIG. The configuration of the exhaust system and suction pipe 5 for flowing dust-containing air in FIG. 1 is the same as that of the conventional device shown in FIG. 2, so the same reference numerals as those in FIG. The explanation will be omitted.

In the embodiment shown in FIG. 1, a suction pipe 5 is connected to a buffer chamber 10, and a first induction fan 11 that sends dust-containing air from inside the exhaust unit 2 to the buffer chamber 10 is located in the middle of the suction pipe 5. A dust detector 12 is provided in the buffer chamber 10 and outputs a signal in response to dust in the air.
It is connected to the. The buffer chamber 10 is for reducing the influence of fluctuations in air flow pressure, flow velocity, etc. inside the exhaust unit 2, and
For example, if the aperture ratio to the surrounding air or outside air is
It is a hollow body with a large number of open holes 13 so as to cover about 50%, and a drain 14 is provided at the bottom. In addition, the dust detector 12 determines whether the laser beam irradiated from the light emitter 15 toward the light receiver 16 detects dust based on the ratio of scattered light caused by scattering by dust in the air and the ratio of straight light. It is of a light scattering type for measuring the amount of air, and is connected to the buffer chamber 10 by a supply pipe 17, and is provided with a second induction fan 18 that sucks a certain amount of air from the buffer chamber 10. There is. The air volume by the second induction fan 18 is the same as that of the first
For example, the air volume of the first induction fan 11 is set to be smaller than that of the first induction fan 11.
min, whereas the second attraction fan 18 is 5
/min.

The dust detector 12 is connected to a controller 19, and the exhaust fan 4 is electrically connected to the controller 19. Based on the output signal of the dust detector 12, the rotational speed of the exhaust fan 4 or the blade It is configured to adjust the exhaust air volume by changing the corner. Furthermore, interlocking is provided so that the induction fans 11 and 18 operate only when the exhaust fan 4 is operating. Code 2 in Figure 1
The dashed line indicated by 0 schematically represents the relationship.

In the above-mentioned apparatus, sampling of dust-containing air is performed by operating each of the induction fans 11 and 18 during ventilation when the exhaust fan 4 is being driven. In that case, the air sucked from inside the exhaust unit 2 by the first induction fan 11 first flows into the buffer chamber 10, but the air volume is
Since the air volume is larger than the suction air volume by the induction fan 18, the excess air leaks to the outside from the open hole 13. Therefore, the pressure inside the buffer chamber 10 is slightly higher than atmospheric pressure. On the other hand, a certain amount of air is supplied to the dust detector 12 from the buffer chamber 10 by a second attraction fan 18, and the dust contained in the air causes the laser beam from the light emitter 15 to reach the light receiver 16. By scattering, the dust detector 12 detects the dust in the air sampled. If the proportion of scattered light in the laser beam is high and the proportion of straight light is small, the dust concentration is high, and therefore the control signal from the controller 19 based on the output signal of the dust detector 12 is As a result, the amount of air exhausted by the exhaust fan 4 increases. On the contrary, when the proportion of scattered light is low and the proportion of straight light is high, the amount of exhaust air by the exhaust fan 4 decreases.

When the exhaust air volume fluctuates due to the dust concentration, the flow velocity of the exhaust air at the open end of the suction pipe 5 changes, and as a result of continuous operation, the degree of clogging of the filter 1 increases. In this case, the static pressure at the open end of the suction tube 5 becomes slightly higher. These fluctuations in flow velocity and static pressure affect the amount of air sucked by the first attraction fan 11, but the first attraction fan 11 always sucks in more air than the amount of air that should be supplied to the dust detector 12. Moreover, in the buffer chamber 10, the excess amount is leaked from the open hole 13, so a fluctuation in the amount of suction air due to a change in the air flow within the exhaust unit 2 causes an increase in the amount of air leaking from the open hole 13. The internal pressure of the buffer chamber 10 remains approximately constant. Therefore, a constant amount of air is supplied to the dust detector 12 due to the steady rotation of the second attraction fan 18. That is, in the above device, the amount of sampling air supplied to the dust detector 12 is not affected by fluctuations in the flow velocity of the dust-containing air at the open end of the suction pipe 5, etc.
It is always kept almost constant, so that the dust concentration can be detected accurately.

Effects of the Invention As is clear from the above explanation, according to the device of the present invention, fluctuations in the flow velocity, static pressure, etc. of dust-containing air flow can be
The amount of air leaked from the opening in the buffer chamber increases or decreases, so the amount of air supplied to the dust detector can be kept almost constant.
As a result, the dust concentration can be detected accurately, and furthermore, unnecessary over-operation of air conditioning equipment can be prevented and energy conservation can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an example of a conventional dust concentration detection device. 5...Suction tube, 10...Buffer chamber, 11
...First attraction fan, 12...Dust detector, 1
3...Open hole, 18...Second attraction fan.

Claims (1)

[Claims] 1. A suction tube that opens in a direction perpendicular to the flow line of the dust-containing air is arranged in the flow path, and the suction tube is communicated with a buffer chamber with an open part, and the above-mentioned A second attracting fan for sucking dust-containing air is interposed, a light-scattering dust detector is communicated with the buffer chamber, and a second dust-containing air is supplied from the buffer chamber to the light-scattering dust detector. A number of attraction fans were installed, and the first
A dust concentration detection device characterized in that the air volume of the first induction fan is set to be larger than the air volume of the second induction fan.