JPH11183419A - Air contamination detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain accurate air contamination information regardless of fluctuation in the output of a sensor by operating an air contamination indicated by gas sensor measurements with reference to a temporary sensor memory value or a sensor memory value. SOLUTION: A gas sensor (a) outputs a signal having a value corresponding to the gas concentration from the variation of resistance due to the presence of gas. Upon turn on the power of the gas sensor (a), a sensor measurement indicating the highest cleanliness of the air are stored, as a sensor memory value, in a sensor memory value setting means (b). A sensor memory value updating means (c) employs a current sensor measurement as a temporary sensor measurement if a sensor measurement read out from the gas sensor (a) indicates a higher cleanliness of the air than a stored value and updates the sensor memory value. An air contamination measuring means (d) operates the air contamination indicated by a sensor measurement from the gas sensor (a) with reference to a temporary sensor memory value or a sensor memory value and delivers air contamination information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control of an intake door corresponding to an exhaust gas of an automobile and a method of automatically controlling a vehicle interior gas such as a cigarette smoke and an exhaust gas when a driving environment outside the vehicle compartment having a high exhaust gas concentration is automatically set to an inside air circulation mode. The present invention belongs to the technical field of an air pollution degree detection device applied as a means for obtaining air pollution degree information outside a vehicle compartment or inside a vehicle compartment by an in-vehicle air purifier or the like that controls the driving of a fan motor according to a component.

[0002]

2. Description of the Related Art Conventionally, as a device for detecting the degree of air contamination, for example, Japanese Patent Application Laid-Open Nos.
No. 431 is known.

The former JP-A-5-96945 discloses that
The first gas sensor for detecting the degree of contamination of the air in the vehicle cabin and the speed for detecting the degree of contamination of the air are provided with the object of preventing the setting of the reference value of the gas sensor due to the contamination of air at the beginning of energization. Is set at a position that is later than the gas sensor by a predetermined time and sets the first reference value when the power is turned on.
And an apparatus for detecting the degree of air contamination based on the relative level of the output value from the first gas sensor based on the output level from the second gas sensor. In other words, in the case of the one-sensor configuration, the reference value is set when the output unstable time in the initial stage of power-on to the sensor has elapsed. However, when smoking is started immediately after power-on, the reference value is shifted. 2 gas sensors are set.

The latter Japanese Patent Application Laid-Open No. Hei 5-253431 aims to obtain a stable sensor output accuracy irrespective of the influence of humidity around a gas sensor, and detects gas components and exhaust gas contained in cigarettes. A gas sensor,
There is described an apparatus provided with a humidity sensor installed near the gas sensor and correction means for correcting the output of the gas sensor based on a change in humidity detected by the humidity sensor.

[0005]

However, in the above-mentioned conventional air pollution degree detecting device, the former device is the first device.
Gas sensor and the second gas sensor, and the latter device has a two-sensor configuration such as a gas sensor and a humidity sensor.
Space for one sensor
There is a common problem of increasing costs.

[0006] In addition, in the former device, the reference value is set only once when the output instability time at the initial power-on time has passed by the second gas sensor, so that the occupant remains in the passenger compartment. In the case where the engine is once stopped and stopped, and immediately after that, the vehicle starts traveling, if the interior of the vehicle is still dirty due to smoking or the like, the sensor value in a state where the air is dirty is used as a reference value. If the temperature or humidity at the start of running changes greatly during running, such as during long-distance running or long-distance running, causes of variations in sensor output (temperature, humidity)
Cannot accurately detect the degree of air contamination.

Further, in the latter device, only the humidity compensation is performed for the variation factor (temperature, humidity, and aging) of the sensor output, and the variation of the sensor output with respect to the temperature and aging remains, and the accurate gas concentration remains. I cannot get information.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air contamination degree detecting apparatus which can obtain accurate air contamination degree information without being affected by variations in sensor output, while having a single sensor configuration which is advantageous in terms of cost. Is to do.

[0009]

[Means for Solving the Problem] [Solution 1] Solution 1 of the above-mentioned problem (Claim 1) utilizes a change in resistance value due to the presence of gas, as shown in the claim correspondence diagram of FIG. A gas sensor a that outputs a signal having a value corresponding to the gas concentration;
A sensor storage value setting unit b for storing a sensor measurement value indicating that the air is cleanest as a sensor storage value after the power supply to the gas sensor a is turned on;
And the sensor measurement value read in the current process is compared with the sensor storage value up to the previous process stored in the sensor storage value setting means b, and the sensor measurement value is more air than the sensor storage value. If the value indicates that the sensor is clean, a sensor storage value updating unit c that converts the current sensor measurement value into a temporary sensor storage value and updates it as a sensor storage value from the next time, and the temporary sensor storage value or the sensor storage value. Air contamination degree calculation means d for calculating the degree of air contamination indicated by the sensor measurement value from the gas sensor a with reference to the above, and outputting the calculation result as air contamination degree information.

[0010] (Solution 2) In the air pollution degree detection apparatus according to claim 1, power is supplied to the gas sensor (a) as shown in the claim correspondence diagram of FIG. An update processing restricting means e for stopping the sensor memory value updating processing by the sensor memory value updating means c for a set time from when the sensor output is stabilized until the sensor output is stabilized is provided.

(Solution Means 3) In the air pollution degree detection apparatus according to Claim 1 or 2, the solution means 3 (Claim 3) of the above-mentioned problem is, as shown in the claim correspondence diagram of FIG. a gas concentration threshold value setting means for setting a value indicating that the air is contaminated as a gas concentration threshold value even if the variation of the sensor measurement value from the gas sensor a is taken into consideration. Is greater than the set gas concentration threshold, the output from the air contamination degree calculating means d is replaced with air contamination degree information based on the calculated value, and a signal indicating that the air is clearly in a dirty state. The air pollution environment compensating means g is provided.

[0012]

(Embodiment 1) Embodiment 1 corresponds to the first to third aspects of the present invention.

FIG. 2 is a diagram showing an exhaust gas-compliant intake door control system to which the air pollution degree detecting device according to the first embodiment is applied.

In FIG. 2, 1 is a gas sensor, 2 is an air conditioner control unit (or a dedicated control unit), 3 is a sensor signal processing circuit, 4 is a servomotor,
Is an intake door, 6 is a blower, 7 is an outside air intake, and 8 is an inside air intake.

The gas sensor 1 outputs a voltage signal Vs corresponding to the gas concentration by utilizing a change in resistance value due to the presence of gas. That is, the gas sensor element includes a gas detection unit provided on a ceramic substrate with SnO ₂ as a main component,
A heater for heating the gas to promote a reaction with the gas. When a reducing gas reacts with the element, the electrical resistance changes due to an oxidation-reduction reaction. When the gas sensor 1 is applied to an exhaust gas-compliant intake door control system, the gas sensor 1 is installed in a front grille that has a small change in temperature and humidity and can effectively detect exhaust gas.

The air conditioner control unit 2
The sensor detects changes in vehicle interior temperature due to changes in the outside air temperature, changes in the amount of solar radiation, changes in the number of occupants, etc., and sets the desired temperature once. , The amount of air blown out, and the switching of the inlet and outlet are automatically controlled by a microcomputer.

One of the air-conditioner controls is an exhaust gas-corresponding intake door control in which a gas sensor 1 detects a state of contamination of the outside air by exhaust gas, and controls the servo motor 4 to automatically switch the suction port.

The sensor signal processing circuit 3 includes an air conditioner
This is a circuit for the gas sensor 1 among the input signal processing circuits built in the control unit 2,
Value G obtained by digitally converting the voltage signal Vs from the sensor
The SAD is input, and a gas concentration calculation value GSC indicating the degree of contamination of the outside air is obtained based on the sensor measurement value GSAD.

The intake door 5 is disposed on the suction side of the blower 6, and is driven by a servomotor 4 as an intake door actuator. Then, the fresh position (FRE) of the intake door 5 that blocks the inside air intake port 8
Then, the outside air introduction rate becomes 100%. Conversely, at the recirculation position (REC) of the intake door 5 closing the outside air intake port 7, the outside air introduction rate becomes 0%, that is, the inside air circulation mode is set. Further, the outside air introduction rate can be changed in accordance with the set opening degree position such that the outside air introduction rate is 50% at the intermediate opening position of the intake door 5.

Next, the operation will be described.

[Exhaust Gas Corresponding Intake Door Control] Exhaust gas corresponding intake door control to which the air pollution degree detecting device of the first embodiment is applied will be briefly described.

The intake gas control corresponding to the exhaust gas is performed by calculating the gas concentration calculation value GSC obtained by the sensor signal processing circuit 3.
And the exhaust gas corresponding intake door control map shown in FIG. 3, for example, when GSC = 1 and the air is clean, the intake door 5 is moved to the fresh position (FRE).
In the case where GSC = 0 and the air is dirty, the intake door 5 is set to the recirculation position (REC), the introduction of outside air is shut off, and the inside air circulation mode is set. . Then, in the region of 1>GSC> 0, which is high in normal driving, 1> GSC
> In the area of> a, and 5 in the area of a ≧ GSC> b.
0% outside air introduction rate, 50% in the region of b ≧ GSC> c
From the outside air introduction rate, which gradually changes from
In the region of C> 0, the outside air introduction rate is 0%.

In other words, when the gas concentration calculation value GSC reaches a certain set threshold value, the recirculation at which the outside air introduction rate becomes 0% when the outside air introduction rate is changed from 100% or 50% to the inside air circulation mode at once is performed. Frequency (REC) increases, and as a result, CO
There is a problem that the concentration of ₂ rapidly increases.

Therefore, in the range of b ≧ GSC> c, the opening degree of the intake door 5 is controlled by the inclination characteristic,
As a result, when the exhaust gas concentration is increased, the internal air circulation mode can be satisfactorily shifted to the internal air circulation mode by changing the external air introduction rate from 15% to the intake door operation to the REC, and the vehicle interior is expanded by expanding the external air introduction area. CO ₂ concentration can be suppressed. By the way, it takes about 4 seconds to operate the intake door from the FRE to the REC with a 100% outside air introduction rate, but it is reduced to about 1 second when the intake door operates to the REC from a 15% outside air introduction rate. Also, for example,
Although the frequency of introduction of outside air is higher than the control of REC at the point b, the sensory value for exhaust gas odor can be suppressed by providing a deodorizing filter such as activated carbon in the intake door.

In this exhaust gas corresponding intake door control, how to obtain a highly accurate gas concentration calculation value GSC is a deciding factor of control reliability. In particular, when the inclination characteristic is adopted in the exhaust gas corresponding intake door control map, a high level is required. Obtaining an accurate gas concentration calculation value GSC is a necessary condition for effective control.

[Gas Sensor Signal Processing Operation] FIG. 4 is a flowchart showing the gas sensor signal processing operation performed by the sensor signal processing circuit 3. Each step will be described below.

In step 40, the set time A (for example, 60
(Second) has elapsed, and the process proceeds to step 41 if YES, and to step 42 if NO.
That is, the update process of the sensor stored value GSMS is stopped during the set time A after the ignition switch is turned from OFF to ON (corresponding to the update process limiting means e).

In step 41, after the set time A has elapsed since the ignition switch was turned from OFF to ON,
The sensor measured value GSAD read from the gas sensor 1 in the current process and the sensor stored value G stored in the RAM (corresponding to the sensor stored value setting means b) up to the previous process are stored.
Compare with SMS. Here, the RAM stores the sensor measured value GSAD indicating that the air is the cleanest after the set time A has elapsed since the power supply to the gas sensor 1 was turned on by turning on the ignition switch.
It is stored as SMS.

In step 42, if the determination in step 41 is YES, that is, if GSAD> GSMS, the current sensor measured value GSAD is set to the temporary sensor stored value GSMX and updated as the next sensor stored value GSMS. That is, steps 41 and 42 correspond to the sensor stored value updating means c. Note that the read sensor measurement value GSAD is rewritten as a temporary sensor storage value GSMX for each process until the set time A elapses after the power supply to the gas sensor 1 is turned on. The temporary sensor storage value GSMX in the processing is set as the sensor storage value GSMS.

In step 43, the tentative sensor storage value GSMX is stored when step 41 → step 42 has passed, and the sensor storage value G
The SMS is used as a reference value GSM, the ratio of the sensor measurement value GSAD from the gas sensor 1 to the reference value GSM is calculated, and the calculation result is used as a gas concentration calculation value GSC (air contamination degree information) (air contamination degree calculating means d). Equivalent).

In step 44, it is determined whether or not the sensor measurement value GSAD from the gas sensor 1 is less than the gas concentration threshold value GSCM.

In step 45, GS in step 44
When it is determined that AD <GSCM, the gas concentration calculation value GSC in step 43 is changed to GSC regardless of the calculation result.
= 0 (maximum gas concentration). Steps 44 and 45 correspond to the air pollution environment compensating means g. However, in the routine for performing the automatic intake door control calculation using the calculated value GSC, the aforementioned A
Calculation shall not be performed for more than time.

[Restriction on update processing] In step 40 of the above gas sensor signal processing, it is determined whether or not a set time A has elapsed since the ignition switch was turned from OFF to ON, and a sensor storage serving as a reference value of the gas concentration calculation value GSC is determined. The value GSMS update process is restricted. Hereinafter, the reason will be described.

First, when looking at the heater characteristics of the gas sensor 1 shown in FIG. 5, when the heater resistance value R _H = 50Ω and 20 ° C., the maximum heater current flows immediately after the power is turned on, and the constant current after about 30 seconds. Will flow. Also,
When the temperature changes, the heater characteristics slightly change. Therefore, it is necessary to wait at least 40 to 50 seconds after the power is turned on for the gas sensor 1 to have a stable output.

Therefore, in the first embodiment, the set time A
Was set to 60 seconds to ensure the sensor output stability.

As described above, in the initial stage of power-on in which the sensor output is unstable, by limiting the process of updating the sensor stored value GSMS, it is possible to prevent the reference value for calculating the gas concentration calculation value GSC from being erroneously set.

[Calculation of gas concentration having reference value] In step 43 of the gas sensor signal processing, the sensor measurement value GSA from the gas sensor 1 with respect to the reference value GSM
D ratio and calculate the gas concentration calculation value GSC
(Air contamination degree information). Hereinafter, the reason will be described.

First, looking at the sensor resistance characteristics under the condition that the gas concentration is constant shown in FIG. 6, the higher the temperature, the higher the humidity, and the longer the elapsed time, the more the sensor resistance becomes. Tend to decrease. That is, if the temperature or humidity changes even in the short-time span, the sensor output is affected, and in the long-time span, the sensor output value changes even under the same temperature and humidity conditions.

Therefore, in the first embodiment, a reference value GSM is set each time a gas concentration calculation value GSC, which is air contamination information, is obtained by calculation processing, and a sensor measurement value from the gas sensor 1 with respect to this reference value GSM is set. Calculate the ratio of GSAD,
By using the calculation result as a gas concentration calculation value GSC, the degree of air contamination can be detected without being affected by variations due to temperature, humidity, and aging.

Here, how to set the reference value GSM is a problem. The simplest method is to install the same gas sensor in a clean air environment and use the sensor output as the reference value. However, in this case, a two-sensor structure is used, and it is difficult to secure a sensor installation place, and disadvantageous in cost.

On the other hand, in the first embodiment, the processing for updating the sensor storage value GSMS serving as the reference value is performed in steps 41 and 42, and the sensor when the vehicle has passed the place where the air is most clean during traveling is performed. The measured value GSAD is used as the reference value GSM, that is, the reference value is set by a program, thereby achieving a one-sensor structure that is cost-effective. Therefore, if the air passes through a clean place for a very short time while traveling, the highly accurate reference value GSM
Is set.

[Setting of Gas Concentration Threshold] In steps 44 and 45 of the gas sensor signal processing, the sensor measured value GSAD is set to the gas concentration threshold GS.
When it is determined that it exceeds CM, GSC = 0 (gas concentration maximum value) is used instead of the gas concentration calculation value GSC in step 43. Hereinafter, the reason will be described.

For example, when traveling in an air polluted environment, such as when traveling only in an urban area where traffic volume is high and exhaust gas concentration is high, a sensor is used to detect when the vehicle has passed the place where the air is most clean during traveling. Measured value GSAD to reference value GSM
According to the present invention, the high-level reference value GSM is set as the degree of air contamination, and even if the gas concentration is considerably high, the gas concentration calculation value GSC is determined as the degree of air contamination. The stain has a low value (a value close to 1).

Therefore, when traveling in an environment where the air is obviously contaminated, there is a demand to set the inside air circulation mode to maintain the vehicle interior air clean. For this purpose, the sensor measurement value GSAD from the gas sensor 1 is used as it is. Control for judging the degree of air contamination by comparing the absolute values is added. In other words, in this air contamination degree determination, the sensor measurement value GSA
It is necessary to set a gas concentration threshold GSCM to be compared with D in advance.

In setting the gas concentration threshold value GSCM in advance, first, looking at the sensor voltage characteristics, as shown by the solid line characteristics in FIG. 7, the sensor voltage Vs shows a characteristic that decreases as the gas concentration increases. Considering the variation of the sensor measurement value GSAD from the gas sensor 1, the characteristic becomes a dotted line. Therefore, even if there is a maximum variation, the value indicating that the air is dirty is set to the gas concentration threshold GSCM.
(Corresponding to gas concentration threshold value setting means f).

Therefore, when it is determined that the sensor measurement value GSAD exceeds the gas concentration threshold value GSCM, GSC = 0 (gas concentration maximum value) is output instead of the gas concentration calculation value GSC, It is possible to prevent erroneous detection of the degree of air contamination when traveling in an environment where the air is always contaminated.

In particular, in the intake door control corresponding to the exhaust gas, if GSC = 0, as apparent from FIG. 3, the internal air circulation mode is immediately set, and the introduction of the exhaust gas into the vehicle compartment is shut off.

(Other Embodiments) In the first embodiment, an example in which the air pollution degree detecting device is applied to an intake door control system corresponding to exhaust gas has been described. However, a vehicle air purifier control system, a gas notification system, etc. The air pollution degree detection device of the present invention can be applied to other systems that require air pollution degree information (gas concentration information).

In the first embodiment, the gas sensor uses H ₂ or CO ₂ whose sensor resistance decreases as the gas concentration increases.
Although an example of a reducing gas sensor such as that described above has been described, the air pollution degree detection device of the present invention can also be applied to an oxidizing gas sensor such as NO ₂ whose sensor resistance increases as the gas concentration increases. In this case, the judgment that the air is clean and the judgment of the gas concentration may be reversed.

In the first embodiment, in the calculation of the degree of air contamination, an example is shown in which the degree of air contamination is calculated based on the ratio of the sensor measurement value to the reference value. However, the air contamination degree is calculated by subtracting the reference value from the sensor measurement value. The degree may be calculated.

In the first embodiment, an example in which the update process is stopped for a set time using a timer as the update process restricting means has been described. However, a limit (limiter) is provided for the sensor storage value to be stored and set. Alternatively, an example in which a timer and a limiter are used in combination may be used.

In the first embodiment, as an example of the method of compensating for the air pollution environment, an example of a method of comparing with a threshold value has been described, but the following method is also available.

The differential value ΔGSAD (t−1) of the previous time is compared with the differential value ΔGSAD (t) of the present time. If the relationship satisfies the following equation, it is determined that the air is similarly contaminated. to decide.

ΔGSAD (t−1) * B <ΔGSAD (t) B: Coefficient As described above, by adjusting to the human sense of smell,
It is possible to increase the accuracy of sensing the exhaust gas odor.

Further, when the method of comparing with the threshold value and the method of using the differential value are used together, the accuracy is further improved.

[0056]

According to the first aspect of the present invention, there is provided a gas sensor for outputting a signal of a value corresponding to a gas concentration by utilizing a change in a resistance value due to the presence of a gas; A sensor storage value setting means for storing a sensor measurement value indicating that the air is the cleanest as a sensor storage value, a sensor measurement value read in the current process from the gas sensor, and a sensor storage value setting Comparing the sensor stored values up to the previous processing stored in the means,
When the sensor measurement value is a value indicating that the air is more clean than the sensor storage value, a sensor storage value updating unit that sets the current sensor measurement value as a temporary sensor storage value and updates it as a sensor storage value from the next time. Air contamination degree calculation means for calculating the degree of air contamination indicated by the sensor measurement value from the gas sensor based on the temporary sensor storage value or the sensor storage value, and outputting the calculation result as air contamination degree information. Therefore, it is possible to provide an air contamination degree detection device that can obtain accurate air contamination degree information without being affected by a variation in sensor output, while having a single sensor configuration that is advantageous in terms of cost.

According to the second aspect of the present invention, the first aspect is provided.
In the air pollution degree detecting device according to the above aspect, the update processing restricting means for stopping the updating processing of the sensor storage value by the sensor storage value updating means is provided. In the early stage of turning on the power, it is possible to prevent erroneous setting of the reference value for calculating the gas concentration calculation value.

According to the third aspect of the present invention, a first aspect is provided.
3. The gas concentration threshold value according to claim 2, wherein a value indicating that the air is contaminated is set as a gas concentration threshold value even when a variation in a sensor measurement value from the gas sensor is considered. Provide setting means,
When the sensor measurement value from the gas sensor exceeds the set gas concentration threshold value, the output from the air contamination degree calculating means is replaced with the air contamination degree information based on the calculated value, and the air is clearly contaminated. Since the air pollution environment compensating means for providing a signal indicating the presence is provided, in addition to the effect of the invention described in claim 1 or 2, erroneous detection of the degree of air pollution when the vehicle is always driven in an environment where air is polluted. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a view corresponding to a claim showing an air contamination degree detecting device of the present invention.

FIG. 2 is a diagram showing an exhaust gas-compatible intake door control system to which the air pollution degree detection device of the first embodiment is applied.

FIG. 3 is a diagram showing an example of an exhaust gas corresponding intake door control map in the exhaust gas corresponding intake door control system to which the air pollution degree detecting device of the first embodiment is applied.

FIG. 4 is a flowchart showing a gas sensor signal processing operation performed by a sensor signal processing circuit of the exhaust gas-compliant intake door control system according to the first embodiment;

FIG. 5 is a heater current characteristic diagram at the initial stage of turning on the power of the gas sensor.

FIG. 6 is a sensor resistance characteristic diagram showing how the sensor resistance changes with respect to variation factors (temperature, humidity, and aging) under the condition that the gas concentration is constant.

FIG. 7 is an explanatory diagram for explaining how to set a gas concentration threshold based on a sensor output voltage characteristic with respect to a gas concentration.

[Explanation of symbols]

 a gas sensor b sensor storage value setting means c sensor storage value updating means d air contamination degree calculating means e update processing limiting means f gas concentration threshold setting means g air pollution environment compensation means

Claims (3)

[Claims] 1. A gas sensor that outputs a signal of a value corresponding to a gas concentration by using a change in resistance value due to the presence of a gas, and a sensor that indicates that air is the cleanest after power to the gas sensor is turned on. A sensor storage value setting unit that stores the measurement value as a sensor storage value; a sensor measurement value read in the current process from the gas sensor; Comparing with the sensor storage value, if the sensor measurement value is a value indicating that the air is more clean than the sensor storage value, the current sensor measurement value is used as the temporary sensor storage value and as the sensor storage value from the next time A sensor storage value updating means for updating, calculating a degree of air contamination indicated by a sensor measurement value from the gas sensor based on the temporary sensor storage value or the sensor storage value, An air pollution degree detection device, comprising: air pollution degree calculation means for outputting a calculation result as air pollution degree information. 2. The air pollution degree detecting device according to claim 1, wherein the sensor storage value updating processing by the sensor storage value updating means is performed for a set time from when the power to the gas sensor is turned on until the sensor output is stabilized. An air pollution degree detecting device, comprising an update processing limiting means for stopping. 3. The air pollution degree detection device according to claim 1, wherein a value indicating that the air is dirty is set to a gas concentration threshold value even when a variation in a sensor measurement value from the gas sensor is considered. A gas concentration threshold value setting unit that sets the gas concentration threshold value as an air flow rate based on the calculated value, when the sensor measurement value from the gas sensor exceeds the set gas concentration threshold value. An air pollution degree detecting device, comprising an air pollution environment compensating means for providing a signal indicating that the air is clearly dirty, instead of the pollution degree information.