JPH05157714A - Air-conditioning control device - Google Patents

Abstract

PURPOSE:To enable contamination of atmosphere to be detected readily and with a high S/N by providing an edge filter for obtaining an edge of a gas sensor output and obtaining a degree of contamination of the atmosphere from an output of the edge filter. CONSTITUTION:An output is taken out of a high-resistance load resistor RL by using an operation amplification circuit 4 for buffer, it is subjected to analog differentiation by a capacitor 5, and then is amplified by an operational amplification circuit 6. An amplified analog differential output VD1 is AD-converted by an AD converter 9, obtained output is stored into a memory 10 in sequence, and then a second digital differentiation is performed by a digital differential circuit 11. An output of the second digital differentiation becomes 0 when a sensor output VRL changes linearly and becomes a large output at an edge of the sensor output VRL. An operation logic circuit 13 detects contamination of external air from a second differential output, closes a load 15 through a drive circuit 14 when the second differential output exceeded a specified value, breaks introduction of external air, at the same time operates a timer 12 for example for 2 minutes, opens the load 15 in two minutes, and then restarts introduction of external air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of air conditioning by a gas sensor, and more particularly to control of an outside air introduction control device for an automobile or an air purifier.

[0002]

2. Description of the Related Art It is known to control the introduction of outside air into an automobile by using a gas sensor. The detection target in this case is mainly NOx from a diesel vehicle. In this regard, the applicant has adopted a NOx sensor using lead-phthalocyanine (Japanese Patent Laid-Open No. 3-103,761) and N using a WO3 thin film.
An Ox sensor (Japanese Patent Application No. 2-177,982) and the like have been proposed. These proposals are for increasing the NOx sensitivity of the sensor, but at present, the NOx sensitivity is still insufficient and the S / N for noise such as wind is insufficient.

In addition to the air conditioning control by the gas sensor, there is an air purifier control. In air purifier control,
Since it is required to quickly detect air pollution due to smoking, smoking is detected from a slight change in the sensor output, and the S / N is insufficient. The noise in this case is
Power fluctuations due to air flow and on / off of the air purifier itself,
This is due to changes in humidity. An air purifier is often used as a measure against smoking in the passenger compartment, but in this case, changes in the air flow due to opening and closing of windows and changes in sensor output due to water vapor and body odor from passengers add as noise. The change in the airflow appears as a change in the sensor temperature due to the wind and a change in the humidity due to a large amount of water vapor flowing into the vehicle compartment in rainy weather. Water vapor and body odor from the passengers themselves are also serious problems in detecting air pollution in a narrow vehicle compartment.

It is well known that the related art is touched upon to differentiate the output of the gas sensor by analog or digital and control the air conditioning from the change of the sensor output. However, the S / N of the sensor signal is often insufficient by simple first-order differentiation, and in many cases only a signal with a lot of noise and slow detection can be obtained.

[0005]

The object of the present invention is to achieve high speed and high S /
The purpose is to enable N to detect contamination of the atmosphere.

[0006]

According to the present invention, in a device for controlling air conditioning by detecting pollution of an atmosphere from the output of a gas sensor, an edge filter for determining the edge of the gas sensor output is provided, and the output of the edge filter is detected. The feature is that the degree of pollution of the atmosphere is obtained.

[0007]

EXAMPLE An example will be described with reference to FIGS. In FIG. 1, 1 is a gas sensor using a metal oxide semiconductor such as WO3, RL is its load resistance, and RH is a heater. In addition to this, the gas sensor 1 uses NO such as lead phthalocyanine.
An x sensor or a flammable gas sensor such as SnO2 may be used. Reference numeral 2 is a constant voltage power supply, which is a detection power supply VC such as 5V for driving the gas sensor 1 and a power supply VD for driving an auxiliary circuit such as 7V.
Emits two outputs of D. 3 is a power supply. 4 is an operational amplifier circuit for buffer, 5 is a differentiating capacitor, R1
˜R5 is a resistor, 6 is an operational amplifier circuit, and 7 is a Zener diode for protection. 8 is a microcomputer, 9
Is an AD converter, 10 is a memory, 11 is a digital differentiating circuit for differentiating the second order, 12 is a timer, 1
Reference numeral 3 is an arithmetic logic circuit. The output of the microcomputer 8 is connected to a drive circuit 14, and the output thereof controls a load 10, for example, a damper of a vehicle outside air introduction control device.

FIG. 2 shows the operation of the embodiment. The WO3 NOx sensor 1 and the lead phthalocyanine NOx sensor have extremely high resistance, and the load resistance RL is, for example, 1M to 10MΩ. Since the load resistance RL is a high resistance, the output is taken out by the buffer operational amplifier circuit 4 and analog-differentiated by the capacitor 5. Since the operational amplifier circuit 6 is driven by the positive single power source VDD, a positive bias of, for example, 100 mV is applied to the differential output by using the resistors R2 and R3. This analog differential output is amplified by the operational amplifier circuit 6, for example, 20 times. This output is called the analog differential output VD1. A protective Zener diode 7 is provided in case the analog differential output VD1 exceeds the AD conversion range of the AD converter 9.

Due to the low concentration of NOx to be detected, WO3
In the case of sensor 1, for exhaust gas from diesel vehicles,
The change in the sensor output VRL is about 50-60 mV. If this is AD-converted with 8 bits, only an output of 2 to 3 bits is obtained, and direct digital differentiation is difficult. Therefore, in the embodiment, the operational amplifier circuit 4 for the buffer is used.
The output is taken out from the high resistance load resistor RL using, and analog differentiation is performed by the capacitor 5. Then, it is amplified by, for example, 20 times in the operational amplifier circuit 6, and the output of 50 mV is, for example, 1
The output is amplified to about V.

The analog differential output VD1 of about 1 V is AD
When 8-bit AD conversion is performed by the converter 9, for example, a 50-bit output is obtained. The obtained output is sequentially stored in the memory 10, and the digital differentiation circuit 11 performs the second-order digital differentiation. The output of the second-order digital derivative is the sensor output V
It becomes 0 when RL changes linearly, and becomes a large output at the edge of VRL. Therefore, due to wind and acceleration of the car,
Even if the sensor output changes linearly, it does not appear in the output of the second digital differentiation. Further, in the second-order digital differentiation, since the edge of VRL is detected, the change in the sensor output VRL can be detected even faster than the first-order differentiation. The arithmetic logic circuit 13 detects the contamination of the outside air from the second-order differential output, and when the second-order differential output exceeds a predetermined value, closes the load 15 via the drive circuit 14 to interrupt the introduction of the outside air. The arithmetic logic circuit 13 detects the contamination of the outside air and at the same time, for example, the timer 12 for 2 minutes.
The load 15 is opened after a maximum of 2 minutes, and the introduction of outside air is restarted.

FIG. 3 shows the operating characteristics of the embodiment. This figure shows the sensor output when the actual vehicle travels using the WO3 gas sensor 1. In the upper part of the figure, the digital differential output VD1 on the first floor
And the output of the wind speed sensor are shown, and the digital differential output VD2 of the second floor is shown in the lower part of the figure. First floor digital differential output VD1
The solid circles in the box indicate the output to diesel exhaust gas, and the dashed circles indicate the effect of wind upon acceleration and deceleration of the vehicle. As is clear from the figure, in the analog differential output VD1, the output to the first, third, and fifth diesel exhaust gases is almost equal to the output to the wind, and it is difficult to distinguish them. This is because the sensitivity to NOx is low and the influence of wind is large.

On the other hand, when the second-order digital differentiation is performed, the NOx sensitivity becomes larger than the influence of the wind, and the NOx and the influence of the wind can be distinguished. For example, if the detection threshold value is set like the shaded area at the bottom of FIG. 3, only NOx can be detected without being affected by the wind. The digital second-order differentiation improves the S / N ratio between NOx and the effect of wind because the change in sensor output due to diesel exhaust gas progresses rapidly in a shorter time than the change in sensor output due to wind. is there.

FIG. 4 shows operation waveforms of the embodiment. This operating waveform is for the third and fourth NOx output peaks in FIG. The analog differential output VD1 is AD-converted, for example, every second, and stored in the memory 10. It is assumed that the sensor 1 touches the exhaust gas from the diesel vehicle at time t0. The first-order differential output VD1 changes as shown in the upper part of the figure, and the first-order differential output VD1 is further digitally differentiated by using 4 seconds from time t0 to t4 to pollute the outside air from the second-order differential output VD2 at time t4. To detect. This closes the load 15,
Cut off the introduction of outside air. When the contamination of the outside air is eliminated, the analog differential output VD1 shows a peak output as shown in the figure. Therefore, the analog differential output V0 at the time of detecting the outside air pollution is stored in the memory 10, and it is detected that the analog differential output VD1 crosses this point twice. For example, at the rightmost point in the upper part of FIG. 4, it is detected that the analog differential output VD1 crosses the reference value V0 twice. The fact that VD1 crosses V0 twice means that the sensor output VRL has almost recovered to the value before the contamination was detected. Therefore, at this point, the load 15 is operated to restart the introduction of outside air.

FIG. 5 shows an operation flowchart of the embodiment. For example, the analog differential output VD1 is sampled every 1 second, and this is digitally differentiated. Digital differential output VD2
Is −2 bits or less and NOx from the diesel vehicle is present, and the damper 15 is closed. Simultaneously with closing the damper 15, the analog differential output V0 at time t0 in FIG. 4 is memorized and the timer 12 is set. When the analog differential output VD1 crosses the reference value V0 twice as shown on the right side of FIG. 4 in the subsequent two minutes, it is considered that the outside air is dissolved and the damper 15 is opened. From the results of actual vehicle running, it was found that the analog differential output VD1 remained higher than the reference value V0 after the valley in FIG. 4 and crossed V0 only once. In such a case, the damper 15 is opened by the timer 12 after, for example, 2 minutes. Here, the value of 2 minutes is empirically determined so that the rate at which the damper 15 is repeatedly closed by the actual vehicle falls within the allowable range. Here, the introduction of the outside air is forcibly restarted by the timer 12, but the reference value V0 may be, for example, a line having an oblique gradient that advances from the lower left to the upper right in FIG. In this way, the reference value V0 gradually increases with the passage of time, and when the damper is kept closed for a long time, V0 increases, and eventually the analog differential output VD1 crosses V0 twice and the damper 15 opens. Although not shown in FIG. 5, the sensor 1 has a low sensitivity to exhaust gas from a gasoline vehicle, has a digital differential output VD2 of 5 bits or more, and has gasoline exhaust gas from a motorcycle, so that the damper 15 is closed.

Another method effective for reopening the closed damper 15 is to add or multiply an appropriate correction coefficient to the reference value V0 to correct V0, and use this value for the analog differential output VD.
To make sure 1 crosses twice. The correction coefficient does not have to be a constant, and the proportion of the time when the damper 15 is closed is less than or equal to the upper limit, and when the frequency of contamination detection is high, the proportion that the damper 15 is closed may be increased. Table 1 shows a simulation result of the ratio of the damper 15 being closed during the driving for 30 minutes in the city.

[0016]

[Table 1] Correction coefficient and ratio of damper 15 closed Correction coefficient Ratio of damper 15 closed (%) 1.0 62 1.02 32 1.04 26 1.06 24 1.08 44 1.10 45 * V0 The value obtained by multiplying by the correction coefficient was used as the value to open the damper 15 when VD1 crossed twice, and simulation was performed from the actual vehicle running data for 30 minutes.

FIG. 6 shows operation waveforms of the embodiment suitable for controlling the air purifier. The difference from the embodiments of FIGS. 1 to 5 is that the microcomputer 8 directly performs the second-order digital differentiation. This is because in the control of the air purifier, the output of the gas sensor 1 is generally large and a resolution sufficient to directly perform the second-order digital differentiation can be obtained. In this embodiment, for example, the output of the gas sensor 1 is sampled and AD-converted every second, and a Laplacian filter is used to obtain 2
Performs digital differentiation of the floor. The Laplacian filter used here is, for example, for five data from time t0 to t4,
Second-order digital differentiation is performed using weights (+1, -3, +4, -3, +1). The second-order differential output is, for example, (VRL0-3VRL1 + 4VRL2-3VRL3 + VRL4). The Laplacian filter has an arbitrary constant number, and this type of filter is generally used as an edge filter in the field of image processing. In the embodiment of FIG. 6, the second-order digital differential output F is compared with a constant K, and the air purifier is operated on the assumption that the second-order digital differential output F is a constant K or more and the air is contaminated. At the same time, the gas sensor output V
By substituting 0 into the reference value S and assuming that the gas sensor output Vn satisfies Vn ≧ S ± G (G is a constant), it is assumed that the air pollution is eliminated and the air purifier is stopped.

The features of detecting the edge of the gas sensor output VRL with an edge filter or second derivative are as follows: 1) Since the edge of the change in VRL is detected, the first floor is detected when the rate of change in VRL becomes large. It can be detected more quickly than differentiation. 2) When the sensor output increases or decreases linearly,
The output of the edge filter is 0, which means that it is not affected by wind or the like. The feature (1) is apparent from the fact that there is a point where the second-order differential signal VD2 becomes maximum before the point where the first-order differential signal VD1 becomes maximum (bottom of VD1) in FIG. Further, the fact that the S / N does not decrease despite the increase in the detection speed is that the second-order differential signal VD2 in FIG. 3 captures diesel exhaust gas more reliably than the first-order differential signal VD1. Is clear from. Regarding the S / N point, the difference in time constant between the sensor signal and the air pollution and noise such as the influence of wind is important. Since the influence of wind is slower than the pollution of the outside air, the difference from the outside air pollution becomes clear by the second derivative. Other noise when detecting outside air pollution is a change in sensor temperature due to acceleration or deceleration of a vehicle. This is because the sensor 1 is in the engine room, so the sensor output V
RL changes greatly linearly during acceleration and deceleration. In the first-order differentiation, the linear change of the sensor output becomes a big noise,
The second derivative does not become noise.

[0019]

EFFECTS OF THE INVENTION According to the present invention, a high S / N ratio can be achieved quickly.
Thus, the pollution of the atmosphere can be detected.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an outside air introduction control device for an automobile according to an embodiment.

2 is an operation waveform diagram of the apparatus of FIG.

FIG. 3 is a characteristic diagram showing a gas sensor output when the vehicle is running.

FIG. 4 is a waveform diagram of an example showing an outside air introduction control operation of an automobile with the gas sensor characteristic of FIG.

FIG. 5 is an operation flowchart of an outside air introduction control device for a vehicle according to the embodiment.

FIG. 6 is an operation flowchart of the air purifier control device according to the embodiment.

[Explanation of symbols]

 1 Gas sensor RH Heater RL Load resistance 2 Constant voltage power supply 3 Power supply 4 Operational amplifier circuit for buffer 5 Differentiating capacitor 6 Operational amplifier circuit 7 Zener diode for protection R1 to R5 resistor 8 Microcomputer 9 AD converter 10 Memory 11 Digital derivative Circuit 12 Timer 13 Arithmetic logic circuit 14 Drive circuit 15 Load VRL Gas sensor output VD1 1st floor differential output VD2 2nd floor differential output VC Detection power supply VDD Circuit power supply

Claims (5)

[Claims] 1. An apparatus for detecting air pollution from the output of a gas sensor to control air conditioning, wherein an edge filter for determining the edge of the gas sensor output is provided, and the air pollution level is determined from the output of the edge filter. The air-conditioning control device is characterized in that 2. An analog differentiating circuit for first-order differentiating the output of the gas sensor by analog, an amplifying circuit for amplifying the output of the analog differentiating circuit, and an AD converting of the first-order differentiating output of the output of the amplifying circuit. Of A
It is characterized in that a D converter and a digital differentiating circuit for digitally converting the AD-converted first-order differential output into the second order are provided, and atmospheric pollution is detected from the output of the digital differentiating circuit. The air conditioning control device according to claim 1. 3. A means for storing a first-order differential output when atmosphere pollution is detected, and a first-order differential output after atmosphere pollution detection is compared with a stored first-order differential output to detect atmosphere pollution detection. 3. The air-conditioning control device according to claim 2, wherein means for detecting that the first-order differential output of the device has crossed the stored first-order differential output twice, and the elimination of the pollution of the atmosphere is detected by the signal of this means. .. 4. The air conditioning control device according to claim 1, wherein the air conditioning control device is used for outside air introduction control of an automobile. 5. The air conditioning control device according to claim 1, further comprising an AD converter for AD converting the output of the gas sensor, and a Laplacian filter for processing the AD converted gas sensor output.