JP3700548B2 - Gas concentration detector and vehicle air conditioner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas concentration detection device and a vehicle air conditioner that detect the concentration of pollutant gas in the air based on a detection value of a gas sensor and a predetermined reference value.
[0002]
[Prior art]
Conventionally, as a gas concentration detection apparatus as described above, for example, as described in JP-A-11-240323, the ratio A to the detection value Vgsn increases as the amount of increase (change rate) of the detection value Vgsn with respect to time increases. The reference value Bgsn that follows the change in the detection value Vgsn with a delay is calculated so as to increase, and the gas concentration is high when the ratio A between the detection value Vgsn and the reference value Bgsn is equal to or greater than the predetermined value Lgs ′. Is detected and the inside / outside air mode is switched to the inside air mode (see FIG. 3 for explaining the related art and the present embodiment ).
[0003]
In the above prior art, by calculating the reference value Bgsn as described above, as shown in FIG. 5, the gas sensor energization time Tb to Tc with respect to the change rate ΔV1 of the detected value Vgsn in the gas sensor energization time Ta to Tb. When the rate of change ΔV2 of the detected value Vgsn at is increased, the ratio Ac to the detected value Vgsn at the gas sensor energizing time Tc is larger than the ratio Ab to the detected value Vgsn at the gas sensor energizing time Tb.
[0004]
[Problems to be solved by the invention]
However, as a result of various studies on the above prior art by the present inventors, it has been found that there are the following problems.
[0005]
In FIG. 3, when the detected value Vgsn increases from the same value of the detected value Vgsn and the reference value Bgsn at the gas sensor energization time T1, the ratio A between the detected value Vgsn and the reference value Bgsn becomes equal to or greater than the predetermined value Lgs ′. Thus, an increase in gas concentration can be detected quickly.
[0006]
However, since the reference value Bgsn follows the change in the detected value Vgsn with a delay, when the detected value Vgsn suddenly changes before the reference value Bgsn catches up with the detected value Vgsn, for example, at the gas sensor energization time T3, the reference value Bgsn. When the detection value Vgsn increases before the value reaches the detection value Vgsn, the ratio A between the detection value Vgsn and the reference value Bgsn does not exceed the predetermined value Lgs ′, and it cannot be detected that the gas concentration is high. A problem occurs.
[0007]
In view of the above problems, an object of the present invention is to provide a gas concentration detection device that can quickly detect this change even when the actual gas concentration changes suddenly.
[0008]
[Means for solving the problems]
The present invention uses the following technical means to achieve the above object.
[0009]
That is, in the invention according to claim 1 , a gas sensor (10) that outputs a detection value (Vgsn) according to the gas concentration of the pollutant gas in the air,
A first reference that follows the change in the detection value (Vgsn) with a delay so that the ratio or difference (A) to the detection value (Vgsn) increases as the change rate of the detection value (Vgsn) increases. First reference value calculating means (S120) for calculating a value (Bgsn);
The ratio or difference (A) between the detected value (Vgsn) detected by the gas sensor (10) and the first reference value (Bgsn) calculated by the first reference value calculating means (S120) is calculated. First fouling degree calculation means (S130) for calculating a first fouling degree in calculation indicating the change rate of the detection value (Vgsn);
Second reference value calculation means (S140) for calculating a second reference value (Cgsn) that follows the change of the ratio or difference (A) calculated by the first stain degree calculation means (S130) with a delay.
Ratio or difference between the ratio or difference (A) calculated by the first stain degree calculation means (S130) and the second reference value (Cgsn) calculated by the second reference value calculation means (S140). (B) is calculated, and the change rate of the change rate of the detection value (Vgsn) that increases as the change rate of the ratio or difference (A) calculated by the first stain degree calculation means (S130) increases. Second dirt degree calculation means (S150) for calculating a second dirt degree, which is the degree of dirt in the calculation processing to be shown, and
Gas for detecting that the gas concentration of the pollutant gas in the air is high when the ratio or difference (B) calculated by the second contamination degree calculation means (S150) is equal to or greater than a first predetermined value (Lgs). It is characterized by having density detecting means (S160).
[0010]
According to the above technical means, the change range of the first stain degree (A) is smaller than the change range of the detection value (Vgsn), and the followability to the change is the second reference value than the first reference value (Bgsn). Since (Cgsn) is better, for example, as shown in FIG. 3, when the detection value (Vgsn) increases before the first reference value (Bgsn) catches up with the detection value (Vgsn) during the energization time T3. As shown in FIG. 4, the second reference value (Cgsn) catches up with the ratio or difference (A) calculated by the first contamination degree calculation means (S130) during the energization time T3. Accordingly, it is possible to detect that the gas concentration is high because the ratio or difference (B) calculated by the second contamination degree calculation means (S150) is equal to or greater than the first predetermined value (Lgs) . As a result, this change can be detected quickly even when the actual gas concentration always changes suddenly.
[0011]
Here, as shown in FIG. 3, in the gas sensor energization time T2, the ratio or difference (A) calculated by the first contamination degree calculation means (S130) is sufficiently large, and the conventional technique detects that the gas concentration is high. ing. However, as shown in FIG. 4, the ratio or difference (B) calculated by the second contamination degree calculation means (S150) is higher than the peak of the ratio or difference (A) calculated by the first contamination degree calculation means (S130). ) Peak, the ratio or difference (B) calculated by the second contamination degree calculation means (S150) during the gas sensor energization time T2 may be less than or equal to the first predetermined value (Lgs).
[0012]
Therefore, in the second aspect of the present invention, even if the ratio or difference (B) calculated by the second contamination degree calculation means (S150) is equal to or less than the first predetermined value (Lgs), the first contamination degree calculation means ( If the ratio or difference (A) calculated in S130) is equal to or greater than the second predetermined value (Lgs ′), the gas concentration in the air is more accurately detected by detecting that the gas concentration in the air is high. Can be detected.
[0013]
Here, when the gas concentration state continues for a long time, the change in the detection value (Vgsn) becomes small, and the ratio or difference calculated by the second contamination degree calculation means (S150) is equal to or less than the first predetermined value (Lgs). And the ratio or difference (A) calculated by the first contamination degree calculation means (S130) is less than or equal to the second predetermined value (Lgs ′), and it may be impossible to detect that the gas concentration is high. .
[0014]
Therefore, according to the third aspect of the present invention, a change in the ratio or difference (A) obtained by calculating the delay of the first reference value (Bgsn) with respect to the change in the detection value (Vgsn) by the first stain degree calculation means (S130). By making the delay time longer than the delay of the second reference value (Cgsn), the ratio or difference (A) calculated by the first contamination degree calculation means (S130) is the first even when the gas concentration state continues for a long time. 2 It can be detected that the gas concentration is higher than a predetermined value (Lgs ′).
[0015]
Here, since the gas concentration in the air outside the passenger compartment changes one by one depending on the traveling location, the vehicle selects the inside air inlet (4b) and the outside air inlet (4a) by the inside / outside air switching means (5, S180, S190). In a vehicle air conditioner that automatically switches, there is a need to always detect a change in gas concentration in the air outside the passenger compartment quickly and reflect it in the switching control of the inside / outside air mode.
[0016]
On the other hand, in the invention according to claim 4, the ratio or difference (B) calculated by the second contamination degree calculation means (S150) is equal to or higher than the first predetermined value (Lgs), and the gas concentration is high. When the inside / outside air switching means (5, S180, S190) opens the inside air inlet (4b) and closes the outside air inlet (4a), the above needs can be satisfied.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment in which a gas concentration detection device of the present invention is applied to switching control of an inside / outside air mode in an automotive air conditioner will be described with reference to FIGS. FIG. 1 is a configuration diagram of an automotive air conditioner in the present embodiment, FIG. 2 is a flowchart showing a control process performed by a microcomputer, and FIG. 3 shows characteristics of a detected value Vgsn, a reference value Bgsn, and a first contamination degree A. FIG. 4 is a graph showing the characteristics of the first contamination degree A, the second reference value Cgsn, and the second contamination degree B, and the gas concentration detection results.
[0018]
First, the configuration of the air conditioning unit 1 of the automotive air conditioner in the present embodiment will be described with reference to FIG.
[0019]
The air conditioning unit 1 includes an air conditioning case 2 that forms an air passage to the vehicle interior, and a fan 3 that generates an air flow toward the vehicle interior is provided in the air conditioning case 2. Also, an inside / outside air switching box 4 is provided in the air upstream side portion of the fan 3. The inside / outside air switching box 4 has an outside air inlet 4 a for sucking air outside the vehicle compartment (hereinafter referred to as outside air), a vehicle A room air inlet 4b for sucking indoor air (hereinafter referred to as room air) is formed.
[0020]
Reference numeral 5 denotes an inside / outside air switching door as an inside / outside air switching means for selectively opening and closing the outside air suction port 4a and the inside air suction port 4b. The inside / outside air switching door 5 closes the outside air suction port 4a and sucks the inside air. The inside air mode for opening the opening 4b and the outside air mode for opening the outside air suction port 4a and closing the inside air suction port 4b can be set. The inside / outside air switching door 5 is driven by a servo motor 6 as its driving means.
[0021]
Further, on the air downstream side of the fan 3, an evaporator 7 is provided for cooling the air introduced from the suction ports 4 a and 4 b selected by the inside / outside air switching door 5. The evaporator 7 is a heat exchanger for cooling that constitutes a known refrigeration cycle together with a compressor, a condenser, and a receiver (not shown).
[0022]
Further, although not shown, a heater core as a heat exchanger for heating, an air mix door as a temperature adjusting means, and a known blow mode switching mechanism are provided on the air downstream side of the evaporator 7, respectively.
[0023]
Next, the configuration of the control system of this embodiment will be described.
[0024]
Inside the control device 8, there are provided a well-known microcomputer comprising an unillustrated CPU, RAM, ROM and the like, an A / D conversion circuit, a timer and the like.
[0025]
Further, when the ignition switch 9 is turned on, the control device 8 is supplied with electric power from a battery (not shown) and enters an operating state.
[0026]
A gas sensor 10 that detects the concentration of NOx in the outside air, an air conditioning instruction member (not shown) (for example, an inside / outside air changeover switch that manually sets the inside / outside air mode), and the like are connected to the input terminal of the control device 8.
[0027]
Here, the gas sensor 10 according to the present embodiment is provided in a portion (for example, a vehicle front grill) where the NOx concentration can be satisfactorily detected in contact with outside air in the vehicle.
[0028]
Here, the configuration of the gas sensor 10 will be described. Although not shown, an oxide semiconductor (SnO _{2 in the} present embodiment) as a gas sensitive body and an electric heater as a heat supply means are adjacent to each other on an alumina substrate. The oxide semiconductor and the electric heater are both supplied with electric power from the battery when the ignition switch 9 is turned on.
[0029]
Further, when the oxide semiconductor is heated by the electric heater, oxygen and NOx are adsorbed by negative charges, and the resistance value increases as the amount of adsorbed negative charges increases. And when electric power is supplied from the battery, this resistance value is outputted as a detection value.
[0030]
The electric heater is configured to heat the oxide semiconductor to about 300 ° C. when electric power is supplied from the battery.
[0031]
Further, a servo motor 6 and the like are connected to the output terminal of the control device 8, and a signal corresponding to a control process performed by the microcomputer described later is output.
[0032]
Next, control processing performed by the microcomputer in the present embodiment will be described with reference to the flowchart of FIG. Note that the routine of FIG. 2 is processed at predetermined intervals, and is not activated when the inside / outside air mode is set by the inside / outside air changeover switch.
[0033]
When the routine of FIG. 2 starts, first, the oxide semiconductor and the electric heater are energized (hereinafter, the gas sensor 10 is energized). In step S100, the memory, timer, etc. are initialized, and in the next step S110, the detection value Vgsn of the gas sensor 10 is read.
[0034]
In the next step S120, the current first reference value Bgsn is calculated based on the following formula 1 and stored in the RAM as a storage means.
[0035]
[Expression 1]
Bgsn = Bgsn-1 + (Vgsn-Bgsn-1) / m
Here, Bgsn-1 is the previous first reference value, m is the time constant, and Vgsn is the detected value of the gas sensor 10 at this time. The initial value of Bgsn-1 is set to Vgsn.
[0036]
The current first reference value Bgsn stored in the RAM is used as the previous first reference value Bgsn-1 in the next calculation.
[0037]
In Formula 1, the smaller the time constant m is set, the larger the difference between the detected value Vgsn and the previous first reference value Bgsn−1 is taken, and the delay of the first reference value Bgsn with respect to the change in the detected value Vgsn. Has become shorter.
[0038]
By calculating in this way, the first reference value Bgsn follows the change in the detection value Vgsn with a delay as shown in FIG.
[0039]
In the next step S130, the first contamination degree, that is, the ratio A (= Vgsn / Bgsn) between the current detection value Vgsn and the first reference value Bgsn is calculated. The first contamination degree A represents the amount of change in the detected value Vgsn from the previous time to the current time, that is, the rate of change in the detected value Vgsn.
[0040]
In the next step S140, the current second reference value Cgsn is calculated based on the following Equation 2 and stored in the RAM.
[0041]
[Expression 2]
Cgsn = Cgsn-1 + (A-Cgsn-1) / n
Here, Cgsn−1 is the previous second reference value, n is the time constant, and A is the ratio between the current detection value Vgsn calculated in step S130 and the first reference value Bgsn. Further, the initial value of Cgsn−1 is set to the first contamination degree A.
[0042]
The current reference value Cgsn stored in the RAM is used as the previous second reference value Cgsn-1 at the next calculation.
[0043]
In the above formula 2, the smaller the time constant n is set, the larger the difference between the first contamination degree A and the second reference value Cgsn−1 of the previous time is taken, and the second reference with respect to the change in the first contamination degree A. The delay of the value Cgsn is shortened.
[0044]
By calculating in this way, the second reference value Cgsn follows the change of A with a delay as shown in FIG. The time constant n in Expression 2 is set smaller than the time constant m in Expression 1. In other words, the delay of the first reference value Bgsn with respect to the change in the detection value Vgsn is longer than the delay of the second reference value Cgsn with respect to the change in the first contamination degree A.
[0045]
In the next step S150, a ratio B (= A / Cgsn) between the second stain degree, that is, the current first stain degree A and the second reference value Cgsn is calculated. The second stain degree B represents the change amount of the first stain degree A from the previous time, that is, the change rate of the change rate of the detection value Vgsn.
[0046]
In the next step S160, it is determined whether or not the second stain degree B is greater than a first predetermined value Lgs.
[0047]
If NO is determined in step S160, the process proceeds to step S170. If YES is determined, the process proceeds to step S180.
[0048]
In step S170, it is determined whether or not the first contamination degree A is greater than a second predetermined value Lgs ′.
[0049]
If YES is determined in step S170, the inside / outside air mode is set to the inside air mode in step S180, and if NO is determined, the inside / outside air mode is set to the outside air mode in step S190, and the process returns to step S110.
[0050]
According to the present embodiment, the first reference value Bgsn that follows the change of the detected value Vgsn with delay is calculated in step S120, and the ratio A between the detected value Vgsn and the first reference value Bgsn is calculated in step S130. Calculated as a degree of contamination of 1. Further, in step S140, a second reference value Cgsn that follows the change in the first contamination degree A with a delay is calculated, and in step S150, the ratio B between the first contamination degree A and the second reference value Cgsn is calculated. It is calculated as the second contamination degree, and when the second contamination degree B is equal to or greater than the first predetermined value Lgs, it is detected that the NOx concentration is high, and the inside / outside air mode is set to the inside air mode in step S180.
[0051]
Thereby, the change width of the first contamination degree A becomes smaller than the change width of the detection value Vgsn, and the second reference value Cgsn is better than the first reference value Bgsn in the followability to the change. As shown in FIG. 3, when the detected value Vgsn increases before the first reference value Bgsn catches up with the detected value Vgsn during the gas sensor energizing time T3, as shown in FIG. The second reference value Cgsn has caught up. Therefore, it is possible to detect that the second contamination degree B is equal to or higher than the first predetermined value Lgs and the gas concentration is high. As a result, this change can be detected quickly even when the actual gas concentration always changes suddenly.
[0052]
Even if the second contamination degree B is equal to or less than the first predetermined value Lgs, if the first contamination degree A is determined to be equal to or greater than the second predetermined value Lgs ′ in step S170, it is determined that the NOx concentration is high. By setting the inside / outside air mode to the inside air mode, it is possible to more accurately detect the high NOx concentration.
[0053]
Further, by making the delay of the first reference value Bgsn with respect to the change of the detection value Vgsn longer than the delay of the second reference value Cgsn with respect to the change of the first contamination degree A, the state where the NOx concentration is high continues for a long time. Even if the change in Vgsn becomes small, it can be detected that the first contamination degree A is equal to or higher than the second predetermined value Lgs ′ and the NOx concentration is high.
[0054]
(Other embodiments)
In the above-described embodiment, the embodiment in which the gas concentration detection device of the present invention is applied to the inside / outside air mode control of the air conditioner for automobiles is described, but not limited thereto, for example, when the gas concentration is detected to be high, You may make it drive | operate an air cleaner.
[0055]
In each of the above embodiments, the “ratio or difference calculated by the first contamination degree calculation means” and the “ratio or difference calculated by the second contamination degree calculation means” in claim 1 are respectively set as the detected value Vgsn. A ratio A to Bgsn, and a ratio B to the first contamination degree A and the second reference value Cgsn are set as the difference between the detection values Vgsn and Bgsn, and the difference between the first contamination degree A and the second reference value Cgsn, respectively. It is also good.
[0056]
In each of the above embodiments, the current first reference value Bgsn (current second reference value Cgsn) is changed to the previous first reference value Bgsn-1 (previous second reference value Cgsn-1) as a detected value. By adding the value obtained by multiplying the difference between Vgsn (first contamination degree A) and the previous first reference value Bgsn-1 (previous second reference value Cgsn-1) by the time constant m (time constant n). However, the present invention is not limited to this. For example, the current detection value Vgsn (current first contamination degree A) is added to the previous first reference value Bgsn-1 (previous second reference value Cgsn-1). It may be calculated by adding a value obtained by multiplying the difference from the previous detection value Vgsn-1 (the previous first degree of contamination A) by the time constant m (time constant n).
[0057]
Further, in each of the above embodiments, the form using the sensor that detects the NOx concentration in the air as the “gas sensor” in claim 1 has been described. However, the present invention is not limited to this, and for example, a sensor that detects a gas concentration other than NOx May be used.
[0058]
Further, as described in the above embodiments, when the first contamination degree A is not less than the second predetermined value Lgs ′ or the second contamination degree B is not less than the first predetermined value Lgs, the outside air inlet 4 is completely closed. It is not necessary to do so, and it may be opened as long as it is a slight amount.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an automotive air conditioner according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a control process performed by a microcomputer in the embodiment.
FIG. 3 is a graph provided for explaining both the prior art and the above embodiment showing the characteristics of the detection value Vgsn, the first reference value Bgsn, and the first contamination degree A in the above embodiment , and the gas concentration detection result ; is there.
FIG. 4 is a graph showing the characteristics of the first contamination degree A, the second reference value Cgsn, and the second contamination degree B and the gas concentration detection results in the embodiment.
FIG. 5 is a graph showing the relationship between a detection value Vgsn and a reference value Bgsn in the prior art.
[Explanation of symbols]
2 air conditioning case,
3 fans (air blowing means),
4a Outside air inlet,
4b Inside air inlet,
5 Inside / outside air switching door (inside / outside air switching means),
10 Gas sensor.

Claims (4)

A gas sensor (10) for outputting a detection value (Vgsn) according to the gas concentration of the pollutant gas in the air;
A first reference that follows the change in the detection value (Vgsn) with a delay so that the ratio or difference (A) to the detection value (Vgsn) increases as the change rate of the detection value (Vgsn) increases. First reference value calculating means (S120) for calculating a value (Bgsn);
The ratio or difference (A) between the detected value (Vgsn) detected by the gas sensor (10) and the first reference value (Bgsn) calculated by the first reference value calculating means (S120) is calculated. First fouling degree calculation means (S130) for calculating a first fouling degree in calculation indicating the change rate of the detection value (Vgsn);
Second reference value calculation means (S140) for calculating a second reference value (Cgsn) that follows the change of the ratio or difference (A) calculated by the first stain degree calculation means (S130) with a delay.
Ratio or difference between the ratio or difference (A) calculated by the first stain degree calculation means (S130) and the second reference value (Cgsn) calculated by the second reference value calculation means (S140). (B) is calculated, and the change rate of the change rate of the detection value (Vgsn) that increases as the change rate of the ratio or difference (A) calculated by the first stain degree calculation means (S130) increases. The second stain degree calculating means ( S150) for calculating the second stain degree, which is the stain degree in the calculation process , and the ratio or difference (B) calculated by the second stain degree calculating means (S150) is 1. A gas concentration detection device comprising gas concentration detection means (S160) for detecting that the gas concentration of the pollutant gas in the air is high when it is equal to or greater than one predetermined value (Lgs) The gas concentration detection means (S160, S170) is configured to detect the first concentration value even if the ratio or difference (B) calculated by the second contamination degree calculation means (S150) is equal to or less than the first predetermined value (Lgs). The high gas concentration in the air is detected when the ratio or difference (A) calculated by the contamination degree calculating means (S130) is equal to or greater than a second predetermined value (Lgs'). Gas concentration detector. The first reference value calculation means (S120) is configured such that a delay of the first reference value (Bgsn) with respect to a change in the detection value (Vgsn) is a ratio or difference calculated by the first stain degree calculation means (S130) ( 3. The gas concentration detection apparatus according to claim 2, wherein the first reference value (Bgsn) is calculated so as to be longer than a delay of the second reference value (Cgsn) with respect to the change in A). A vehicle air conditioner using the gas concentration detection device according to any one of claims 1 to 3,
An air conditioning case (2) that forms an air passage to the passenger compartment;
Air blowing means (3) for generating an air flow in the air conditioning case (2);
An inside air inlet (4b) for sucking air in the passenger compartment into the air conditioning case (2);
An outside air inlet (4a) for sucking outside air into the air conditioning case (2);
An inside / outside air switching means (5, S180, S190) for selectively opening and closing the inside air inlet (4b) and the outside air inlet (4a);
When the gas concentration detecting means (S160, S170) detects that the gas concentration is high, the inside / outside air switching means (5, S180, S190) opens the inside air suction port (4b) and sucks the outside air. A vehicle air conditioner characterized by closing the mouth (4a).

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