JP3090518B2 - Air conditioning control device - Google Patents

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 of an automobile, control of an air purifier, and the like.

[0002]

2. Description of the Related Art It is known to control the introduction of outside air into an automobile using a gas sensor. The detection target in this case is mainly NOx from a diesel vehicle. In this regard, the applicant has proposed a NOx sensor using lead-phthalocyanine (Japanese Patent Laid-Open No. 3-103,761) and an Nx sensor using a WO3 thin film.
An Ox sensor (Japanese Patent Application No. 2-177,982) has 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 to noise such as wind is insufficient.

In air conditioning control using a gas sensor, there is another control such as an air purifier. In the control of the air purifier,
Since it is required to quickly detect the contamination of air due to smoking, smoking is detected from a slight change in sensor output, and the S / N is insufficient. The noise in this case is
Power fluctuations due to airflow and the on / off of the air purifier itself,
For example, fluctuations in humidity. An air purifier is often used as a countermeasure against smoking in a vehicle cabin. In this case, a change in airflow due to opening and closing of a window and a change in sensor output due to water vapor and body odor from an occupant are added as noise. The change in the air flow appears as a change in the sensor temperature due to the wind and a change in the humidity due to the flow of a large amount of water vapor into the vehicle compartment in rainy weather. Water vapor and body odor from the occupants themselves are also serious problems in detecting air pollution in a narrow cabin.

[0004] Referring to the related art heretofore known, it is well known that the output of a gas sensor is differentiated in an analog or digital manner, and air conditioning is controlled from a change in the sensor output. However, in the simple first-order differentiation, the S / N of the sensor signal is often insufficient, and in many cases, only a signal with a lot of noise and a slow detection is obtained.

[0005]

An object of the present invention is to provide a high speed and high S /
The purpose of the present invention is to make it possible to detect atmospheric contamination with N.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an apparatus for controlling air conditioning by detecting atmospheric pollution from the output of a gas sensor.
An edge filter for obtaining a starting point of a change in the output of the gas sensor is provided, and the degree of contamination of the atmosphere is obtained from the output of the edge filter.

[0007]

An embodiment 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. The gas sensor 1 also includes NO such as lead phthalocyanine.
An x sensor or a combustible gas sensor such as SnO2 may be used. Reference numeral 2 denotes 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.
Emit two outputs of D. 3 is a power supply. 4 is an operational amplifier circuit for a buffer, 5 is a capacitor for differentiation, 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 performing second order differentiation, 12 is a timer, 1
3 is an arithmetic logic circuit. The output of the microcomputer 8 is connected to a drive circuit 14, which controls a load 10, for example, a damper of an outside air introduction control device of a vehicle.

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

Since the concentration of NOx to be detected is low, WO3
In the case of the sensor 1, for exhaust gas from a diesel vehicle,
The change of the sensor output VRL is about 50 to 60 mV. If this is AD-converted with 8 bits, only an output of 2 to 3 bits is obtained, and it is difficult to directly perform digital differentiation. Therefore, in the embodiment, the operational amplifier circuit 4 for the buffer is used.
Is used to extract the output from the high-resistance load resistor RL, and the capacitor 5 performs analog differentiation. The signal is amplified by, for example, 20 times by the operational amplifier circuit 6 and the output of 50 mV is output by, for example, 1
Amplify to about V output.

The analog differential output VD1 of about 1 V is applied to AD
When 8-bit AD conversion is performed by the converter 9, an output of, for example, 50 bits is obtained. The obtained outputs are 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 differentiation is the sensor output V
It becomes 0 when RL changes linearly, and becomes a large output at the edge of the change of VRL. For this reason, even if the sensor output changes linearly due to the wind, acceleration of the vehicle, or the like, it does not appear in the output of the second-order digital differentiation. In the second order digital differentiation,
Since the edge of VRL is detected, a change in the sensor output VRL can be detected faster than the first derivative. Arithmetic logic circuit 13
Detects the pollution of the outside air from the second derivative output, and when the second derivative output exceeds a predetermined value, the load 15
And shut off the introduction of outside air. The arithmetic logic circuit 13 detects the contamination of the outside air and, at the same time, activates the timer 12 for 2 minutes, for example, and opens the load 15 after a lapse of at most 2 minutes to restart the introduction of the outside air.

FIG. 3 shows the operating characteristics of the embodiment. This figure shows the sensor output when the vehicle travels using the WO3 gas sensor 1. At the top of the figure is the first-order digital differential output VD1
And the output of the wind speed sensor. The lower part of the figure shows the second-order digital differential output VD2. First-order digital differential output VD1
Indicates the output to diesel exhaust gas, and the broken line indicates the effect of wind accompanying acceleration or deceleration of the vehicle. As is clear from the figure, in the analog differential output VD1, the first, third, and fifth outputs to the diesel exhaust gas are almost equal to the outputs to the wind, and it is difficult to identify them. This is because the sensitivity to NOx is small and the influence of wind is large.

On the other hand, when the second-order digital differentiation is performed, the NOx sensitivity becomes greater than the effect of wind, and NOx and the effect of wind can be distinguished. For example, if the detection threshold is determined as shown by the hatched area in the lower part of FIG. 3, only NOx can be detected without being affected by wind. The reason why the S / N between NOx and the effect of wind is improved by digital second-order differentiation is that the change in sensor output due to diesel exhaust gas progresses more 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 every second, for example, 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. The first-order differential output VD1 is further digitally differentiated using four seconds from the time t0 to t4, and the outside air pollution is reduced at the time t4 from the second-order differential output VD2. To detect. This closes the load 15,
Shut off the introduction of outside air. When the contamination of the outside air is eliminated, the analog differential output VD1 shows a peak of the 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 right end point in the upper part of FIG. 4, it is detected that the analog differential output VD1 crosses the reference value V0 twice. When VD1 crosses V0 twice, it means that the sensor output VRL has almost recovered to the value before the detection of contamination. Therefore, at this point, the load 15 is operated to restart the introduction of the outside air.

FIG. 5 shows an operation flowchart of the embodiment. For example, the analog differential output VD1 is sampled every second and digitally differentiated. Digital differential output VD2
Is -2 bits or less, and there is NOx from the diesel vehicle, and the damper 15 is closed. At the same time as the damper 15 is closed, the analog differential output V0 at time t0 in FIG. 4 is stored, and the timer 12 is set. If the analog differential output VD1 crosses the reference value V0 twice in the following two minutes as shown on the right side of FIG. 4, it is determined that the contamination of the outside air has been resolved, and the damper 15 is opened. From the result of running the actual vehicle, it was found that the analog differential output VD1 stayed at a value higher than the reference value V0 after the trough in FIG. 4 and crossed V0 only once. In such a case, the damper 15 is opened by the timer 12 after, for example, two minutes. Here, the value of 2 minutes is empirically determined so that the rate at which the damper 15 is closed by repeating the actual vehicle running is within an allowable range. Here, the introduction of outside air is forcibly restarted by the timer 12, but for example, the reference value V0 may be a line having an oblique slope that goes 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 if the damper is kept closed for a long time, V0 increases. 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-powered vehicle. The digital differential output VD2 is 5 bits or more, and the damper 15 is closed on the assumption that there is gasoline exhaust gas from a motorcycle.

Another effective method for reopening the closed damper 15 is to correct or correct V0 by adding or multiplying a reference value V0 by an appropriate correction coefficient.
Check that 1 crosses twice. The correction coefficient does not need to be a constant, and the proportion of the time during which the damper 15 is closed is equal to or less than the upper limit, and when the frequency of contamination detection is high, the proportion at which the damper 15 is closed may be increased. Table 1 shows a simulation result of a rate at which the damper 15 is closed in a 30-minute city driving.

[0016]

Table 1 Correction coefficient and ratio at which damper 15 is closed Correction coefficient Ratio at which damper 15 is 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 the data by the correction coefficient is assumed to be such that the damper 15 is opened when VD1 crosses twice, and a simulation was performed from 30 minutes of actual vehicle travel data.

FIG. 6 shows operation waveforms of the embodiment suitable for controlling the air purifier. The difference from the embodiment of FIGS. 1 to 5 is that the microcomputer 8 directly performs 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 second-order digital differentiation is obtained. In this embodiment, for example, the output of the gas sensor 1 is sampled and AD-converted every second, and the output is sampled using a Laplacian filter.
Performs first-order digital differentiation. The Laplacian filter used here is, for example, for five data at times t0 to t4,
The second-order digital differentiation is performed using the weights (+1, -3, +4, -3, +1). The second-order differential output is, for example, (VRL0-3VRL1 + 4VRL2-3VRL3 + VRL4). The constant of the Laplacian filter is arbitrary, 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 assuming that the second-order digital differential output F is equal to or greater than the constant K and the air is contaminated. At the same time, the gas sensor output V
When 0 is substituted for the reference value S, when the gas sensor output Vn satisfies Vn ≧ S ± G (G is a constant), it is assumed that air pollution has been eliminated, and the air purifier is stopped.

The feature of detecting the edge of the change of the gas sensor output VRL by the edge filter or the second-order differentiation is as follows. 1) To detect the edge of the change of the VRL, it is detected when the rate of change of the VRL becomes large. 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. In addition, the fact that the S / N ratio did not decrease despite the increase in the detection speed means that the second-order differential signal VD2 in FIG. 3 captures diesel exhaust more reliably than the first-order differential signal VD1. It is clear from Regarding the S / N point, the difference between the time constant of the sensor signal between the air pollution and noise such as the influence of wind is important. Since the effect of the wind is a slower decrease than the outside air pollution, the difference from the outside air pollution becomes clear in the second derivative. Other noises at the time of detecting outside air pollution include changes in sensor temperature due to acceleration or deceleration of the vehicle. This is because the sensor 1 is in the engine room, and the sensor output V
RL varies greatly linearly during acceleration and deceleration. In the first derivative, the linear change of the sensor output becomes a large noise,
The second derivative does not cause noise.

[0019]

According to the present invention, the S / N ratio can be increased quickly and
Thus, contamination of the atmosphere can be detected.

[Brief description of the drawings]

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

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

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

FIG. 4 is a waveform diagram of an embodiment showing an outside air introduction control operation of an automobile based on the gas sensor characteristics of FIG. 3;

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

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

[Explanation of symbols]

 DESCRIPTION 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 Capacitor for differentiation 6 Operational amplifier circuit 7 Protection Zener diode R1 to R5 Resistance 8 Microcomputer 9 AD conversion unit 10 Memory 11 Digital differentiation Circuit 12 Timer 13 Operation logic circuit 14 Drive circuit 15 Load VRL Gas sensor output VD1 First-order differential output VD2 Second-order differential output VC Detection power supply VDD Circuit power supply

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/00

Claims (6)

(57) [Claims] An apparatus for controlling air conditioning by detecting contamination of an atmosphere from an output of a gas sensor, wherein an edge filter for obtaining an edge of a change in the output of the gas sensor is provided, and an atmosphere of the atmosphere is detected from an output of the edge filter. An air-conditioning control device, wherein the degree of pollution is determined. 2. The gas filter according to claim 1, wherein the edge filter is a gas sensor.
The second-order differentiation of a force
1 air conditioning control device. 3. The output of a gas sensor is first-order differentiated by analog.
An analog differentiating circuit for An amplification circuit for amplifying the output of the analog differentiation circuit; A for AD-converting the first-order differential output of the output of the amplifier circuit
A D converter, Digital output of the 1st derivative output after AD conversion, 2nd derivative
Digital differentiation circuit for performing Detects atmospheric contamination from the output of the digital differentiator
The air-conditioning control device according to claim 2, wherein 4. The first-order differential output at the time of detecting atmospheric contamination is described.
Means to remember, The first-order differential output after detecting atmospheric contamination is stored in the first-order fine
Compared with the minute output, the first derivative output after detecting the contamination of the atmosphere is
Detects that the stored first derivative output is crossed twice
Means for Detecting the elimination of atmospheric pollution with the signal of this means
The air conditioning control device according to claim 3, wherein 5. An air-conditioning control device, comprising:
The method according to any one of claims 1 to 4, wherein
The air-conditioning control device according to claim 1. 6. An A / D converter for converting an output of a gas sensor into an analog signal.
Process AD converter and AD converted gas sensor output
And a Laplacian filter for performing the operation.
2 air conditioning control device.