JPH0755740A - Gas detector for controlling introduction of outside air of automobile - Google Patents

Abstract

PURPOSE:To control a damper for an automobile by detecting the contamination of the outside air rapidly without being subject to the effect of a wind and without contaminating a gas sensor by dust and water droplets. CONSTITUTION:A printed board 6 is mounted to an upper section and a gas sensor 8 and a cover 16 to a lower section, gas introducing ports 18 are formed at positions lower than the gas sensor 8 in the cover 16, and a drain hole 20 is formed at the lower end of the cover 16. Ventilating holes 22 are formed to the board 6 at positions between the gas sensor 8 and the inner circumference of the cover 16, and the replacement of air in the root of the cover 16 is promoted by utilizing wind pressure on the inside and outside of the board 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outside air introduction control of a vehicle using a gas sensor, and more particularly to a cover thereof.

[0002]

2. Description of the Related Art It has been proposed to detect pollution of air outside a vehicle by a gas sensor and open / close a damper provided in a cowl box or the like to control ventilation to a vehicle compartment. The inventors used a NOx sensor such as WO3
It has been proposed to detect NOx from diesel exhaust gas by second-order differentiating the signal of the O3 sensor (JP-A-5-15).
7,714). Other than this, SnO2 gas sensor (combustible gas) and phthalocyanine sensor (NO
x) and the like are proposed, and in the processing of the sensor signal, in addition to the second derivative, the first derivative, the difference of the gas sensor signal, etc. are proposed.

In detecting the outside air pollution of an automobile, it is necessary that 1) the outside air pollution can be detected promptly and without the influence of the wind, and 2) dust and water droplets do not adhere to the gas sensor. Therefore, the inventor made a prototype in which the gas sensor is covered with a double cover, the outer cover has an opening on the side surface, and the inner cover has an opening at the tip of the cover. The outside air was supposed to enter the cover through the side opening of the outer cover, swirl through the gap between the covers, and touch the gas sensor through the opening at the tip of the inner cover. However, such a cover had a slow response to the outside air.

[0004]

An object of the present invention is to provide a gas for controlling the introduction of outside air of an automobile, which is: 1) quick response to pollution of the outside air, 2) dust and water droplets do not adhere to the gas sensor, and 3) the influence of wind is small. It is to provide a detection device.

[0005]

According to the present invention, a gas sensor for detecting outside air pollution is attached to a lower surface of a substrate, a cover is attached to a lower surface of the substrate so as to surround the gas sensor, and a gas is introduced into the cover at a position lower than the gas sensor. Is provided in the lower end of the cover, a drain opening is provided, and a ventilation hole is provided in the substrate between the gas sensor and the inner circumference of the cover. Preferably,
The ventilation hole is smaller than the gas introduction opening, and a plurality of ventilation holes are provided. Further, preferably, a plurality of openings for introducing gas are provided on the side surface of the cover. The gas inlet and the drain opening at the lower end of the cover may be the same, in which case a large opening is provided at the lower end of the cover.

[0006]

According to the present invention, the gas detection device is attached so that the substrate is on the top and the tip of the cover is on the bottom, and the cover is provided with an opening for introducing gas at a position lower than the gas sensor. Since the opening is below the gas sensor, the gas sensor is not directly exposed to the wind. The substrate is provided with a vent hole at a position between the gas sensor and the inner circumference of the cover. Without the vent hole, the response of the gas sensor is slow, and when the vent hole is provided, the response is quick. The inventor actually confirmed this (FIGS. 7 to 1).
0). The gas detector is installed in the cowl box of the automobile or on the front of the radiator grill, and the gas sensor and the cover are installed so that the tip of the cover faces down.
The flow of air is different above and below the substrate, and if a ventilation hole is provided in the substrate, the air flows through the ventilation hole due to the difference in wind pressure, and the response performance of the gas sensor is improved. Dust, water droplets, etc. enter the cover, and these collide with and adhere to the inner wall of the cover. Here, if the tip of the cover is faced down and the gas sensor is on the top of the cover, dust and water droplets do not adhere to the gas sensor, and the dust and water droplets are discharged from the opening at the bottom of the cover.

In order to prevent the gas sensor from being exposed to the wind, it is preferable that the ventilation hole be smaller than the gas introduction opening, and that a plurality of ventilation holes be provided to make the air flow around the gas sensor uniform. It is preferable that a plurality of openings for introducing gas be provided on the side surface of the cover so that the air in the cover can be replaced quickly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the mounting position of a gas detection device for controlling the outside air introduction of an automobile. The gas detection device 2 is attached to the inside of a cowl box 02 of the automobile 01, the radiator grille on the front face of a radiator 03, or the like. The gas detection device 2 is installed downward, and the signal processing microcomputer 4 is installed in the detection device under the floor of the vehicle interior 04, inside the vehicle interior 04, etc., and the gas sensor and the preamplifier (first-stage amplifier) are installed in the detection device. It is preferable to incorporate it in 2.

FIG. 2 shows the structure of the gas detector 2. In the figure, 6 is a printed circuit board, and 8 is a gas sensor such as WO3, SnO2 or phthalocyanine, which detects NOx from the exhaust gas of a diesel vehicle and combustible gas from the exhaust gas of a gasoline vehicle. Reference numeral 10 is a cap of the gas sensor 8, which is different from the cover referred to in the present invention, and 12 is the cap 1
A ventilation hole provided at the tip of No. 0 is provided with a metal mesh (not shown). There is no other opening in the gas sensor 8, and the ventilation part is only the ventilation hole 12, and ambient air diffuses from the ventilation hole 12 and enters the inside of the cap 10, and contacts the sensor body 14. The sensor body 14 is, for example, a die-bonded alumina substrate on a metal frame, and a WO3 semiconductor and a heater are provided on the substrate.

Reference numeral 16 is a cover made of plastic or metal,
Although it is directly attached to the lower surface of the substrate 6 together with the gas sensor 8, it may be attached via another attachment member. The cover 16 is attached so as to surround the gas sensor 8, two to six gas inlets 18 are provided on the side surface, and a drain port 20 having a smaller diameter than the gas inlet 18 is provided at the tip. The gas sensor 8 and the cover 16 are attached to the lower side of the printed circuit board 6, the gas sensor 8 and the cover 16 are arranged inside the cowl box 02, for example, and the printed circuit board 6 is attached so as to be on the cowl box 02. Between the gas sensor 8 and the inner peripheral surface of the cover 16, the printed circuit board 6 is provided with, for example, 2 to 2.
Six ventilation holes 22 are provided to generate an air flow between the outside of the cowl box 02 and the inside of the cover 16. Vent hole 2
2 has a diameter smaller than that of the gas inlet 18, and is, for example, about 1 to 3 mm. A microcomputer 4 for mounting an auxiliary circuit on the side opposite to the printed circuit board 6 as viewed from the gas sensor 8 and arranging, for example, a differentiating circuit of the gas sensor 8 and an amplifying circuit 24 to perform final signal processing of the gas sensor 8.
And a cable 26. This is cowl box 02
In order to prevent the microcomputer 4 from malfunctioning due to strong noise from the engine inside the radiator and around the radiator 03, and to amplify and use a small signal of the gas sensor 8, an amplifier circuit 24 is arranged on the printed circuit board 6. This is to prevent noise from being added to the sensor signal before amplification.

The operation of the embodiment will be described. When air flows in the cowl box 02 from right to left in the figure, the air enters from the gas introduction port 18 on the right side as shown by the white arrow in the figure and on the opposite side. Is discharged from the gas introduction port 18 of. Gas sensor 8
Since the output fluctuates when the air is exposed to the wind, the gas inlet 18
Is arranged below the tip of the cap 10. The flow of air contains dust, water droplets, etc., and if it adheres to the sensor body 14, it will have an adverse effect, so the drain port 20 is provided at the lower end of the cover 16. The air that has entered from the gas introduction port 18 collides with the inner surface of the cover 16, dust and water droplets move to the lower end of the cover 16, and are discharged from the drain port 20 as indicated by the thick black arrow. Placing the gas inlet port 18 below the gas sensor 8 has an effect of preventing dust, water droplets, and the like from adhering to the gas sensor 8.

A vent hole 22 is provided in the printed circuit board 6, and a part of the air that has entered the cover 16 through the gas inlet port 18 is ventilated by utilizing the difference in wind pressure inside and outside the cowl box 02. Let the air flow. This is also the case when the gas detection device 2 is arranged on the front surface of the radiator 03, and air is made to flow through the ventilation hole 22 by using the difference between the air flow inside and outside the substrate 6. The thin arrows indicate the flow of air through the ventilation holes 22. The inventor has confirmed that the response of the gas sensor 8 is delayed unless the ventilation hole 22 is provided, and the response of the sensor 8 is accelerated when the ventilation hole 22 is provided. It is preferable that a plurality of ventilation holes 22 be provided so that an airflow is uniformly generated around the gas sensor 8.

FIG. 3 to FIG. 5 show a modified cover. Figure 3
In the cover 30, the large gas introduction port 32 also serving as the drain port is provided at the lower end of the cover 30, and the gas discharge port 34 having a small diameter is provided on the downstream side of the cover 30. Also in this case, the gas outlet 34 is arranged below the tip of the cap 10 so that the gas sensor 8 is not directly exposed to the wind.

FIG. 4 shows a modification using the double cover 40. 42 is an outer cover and 44 is an inner cover. For example, the outer cover 42 is provided with a large gas introduction port 46 which also serves as a drain port, and the inner cover 44 is provided with about 2 to 6 gas introduction ports 48 on its side surface. The air that has entered through the gas inlet port 46 at the lower end enters the inner cover 44 through the gas inlet port 48 inside while swirling between the two covers 42 and 44, and a part of the air passes through the vent hole 22. Since the gas flows to the opposite side of the printed circuit board 6, the gas sensor 8 is brought into contact with outside air.

In the cover 50 shown in FIG. 5, about 2 to 6 gas inlets 52 are formed by bending the cover 50 into an arrow blade shape, and the air is collided with the arrow blade portion to change the flow direction. , The inside of the cover 50 is swung to contact the gas sensor 8. The dust and water droplets collide with the inner wall of the cover 50, collect below, and are discharged from the drain port 20. Part of the air in the cover 50 flows from the ventilation hole 22 to the opposite side of the substrate 6, and the air around the gas sensor 8 is exchanged during this time.

The shape of the cover can be variously modified in addition to this. What is important is to arrange the gas inlet below the gas sensor 8 (particularly below the tip of the sensor 8).
It is to prevent the wind from directly touching the gas sensor 8. In addition, the drain port 20 is provided at the lower end of the cover, and dust, water droplets, and the like that have entered the cover are discharged from the drain port 20 to the outside. Further, a ventilation hole 22 is provided in the substrate 6 at a position between the inner circumference of the cover and the gas sensor.
2 is to replace the air at the bottom of the cover (around the gas sensor 8).

FIG. 6 shows a circuit of the gas detector 2. The power source of the automobile battery or the like is stabilized and, for example, a 5V power source + VDD is taken out and supplied to the gas sensor 8. Reference numeral 60 is a WO3 semiconductor 60, 62 is a heater, and 64 is a load resistor. The gas sensor output to the load resistor 64 is connected to the capacitor 6
After being differentiated by 6, a bias is applied and then amplified by the amplifier circuit 24, for example, 16 to 64 times. Then, a differential signal is sent to the microcomputer 4 using the cable 26, the microcomputer 4 performs the first-order digital differentiation, the second-order differentiation of the resistance value of the WO3 semiconductor 60 detects the contamination of the outside air, and the damper 68 is driven. WO3 semiconductor 60 has high resistance,
Since the differential signal is small and has high impedance, the sensor 8
Amplify around and prevent noise from riding. On the other hand, the microcomputer 4 is arranged at a position away from the engine to prevent malfunction.

FIG. 7 and FIG. 8 show the results of actual vehicle running when the cover 16 of FIG. 2 is used and the vent holes 22 are provided, and FIG. 9 is the result when the cover 16 is used but the vent holes 22 are not provided.
As shown in FIG. These show the results of actual vehicle running for 20 minutes and were measured at the same time. The vertical axis of the figure is the amplification circuit 2
This is the first-order differential signal at 4
Digitally differentiate with to detect air pollution. The WO3 semiconductor 60 mainly feels NOx in diesel exhaust gas,
Since the resistance value increases when touching Ox, the damper 68 is closed when the downward gradient in the figure exceeds the threshold value. If the first derivative has a large gradient,
The damper 68 is closed as gasoline exhaust gas. Fresh in the figure shows a state in which outside air pollution is not detected, and recirculate shows a state in which outside air pollution is detected.

In the results shown in FIGS. 7 and 8 in which the vent hole 22 is provided, the signal of the gas sensor fluctuates constantly, and there is one place in FIG. 7 where the contamination of the outside air is detected. In the latter half of FIG. Is detecting contamination. On the other hand, in the results of FIGS. 9 and 10 in which the ventilation hole 22 is not provided, the signal of the gas sensor is dull, and the fine features are lost. Further, in FIG. 9, there is no place where the pollution of the outside air is detected, and the detection frequency of the outside air is reduced even in the latter half part of FIG. 10, and it is reduced from 5 times in FIG. 8 to 4 times in FIG. The fact that the signal of the gas sensor is dull in FIGS. 9 and 10 and the number of times of detecting the outside air pollution is decreased means that the air around the gas sensor 8 is not replaced so much and the response characteristic is deteriorated.
Therefore, in order to promptly detect the contamination of the outside air, the substrate 6
It is necessary to provide a ventilation hole 22 in the and to replace the air around the gas sensor 8 by utilizing the difference between the wind pressures inside and outside the cowl box 02.

The WO3 semiconductor 60 generally has uniform characteristics, and the difference between the results of FIGS. 7 and 8 and FIGS. 9 and 10 is as follows.
This is due to the presence or absence of the vent hole 22 rather than the variation of the gas sensor 8. Although the second-order differential signal of the WO3 semiconductor 60 is used in the embodiment, the first-order differential signal or the differential signal of the SnO2 gas sensor or the phthalocyanine gas sensor may be used.

[0021]

EFFECTS OF THE INVENTION According to the present invention, 1) a quick response to the pollution of the outside air, 2) dust and water droplets do not adhere to the gas sensor, and 3) the influence of the wind is small, the gas detecting device for the outside air introduction control of the automobile. Is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a mounting position of a gas detection device.

FIG. 2 is a sectional view of a cover of the gas detection device.

FIG. 3 is a sectional view of a cover according to a modified example.

FIG. 4 is a sectional view of a cover according to a modified example.

FIG. 5 is a sectional view of a cover according to a modified example.

FIG. 6 is a circuit diagram of a gas detection device.

FIG. 7 is a characteristic diagram showing an output waveform of the gas detection device of the embodiment.

FIG. 8 is a characteristic diagram showing an output waveform of the gas detection device of the embodiment.

FIG. 9 is a characteristic diagram showing an output waveform of a conventional gas detection device.

FIG. 10 is a characteristic diagram showing an output waveform of a conventional gas detection device.

[Explanation of symbols]

 01 Automobile 02 Cowl box 03 Radiator 04 Vehicle compartment 2 Gas detector 4 Microcomputer 6 Printed circuit board 8 Gas sensor 10 Cap 12 Vent hole 14 Sensor body 16 Cover 18 Gas inlet 20 Drain port 22 Vent hole 24 Amplification circuit 26 Cable 30 Cover 32 Gas inlet 34 Gas outlet 40 Double cover 42 Outer cover 44 Inner cover 46, 48 Gas inlet 50 Cover 52 Gas inlet 60 WO3 semiconductor 62 Heater 64 Load resistance 66 Capacitor 68 Damper

Claims (3)

[Claims] 1. A gas sensor for detecting outside air pollution is attached to a lower surface of a substrate, a cover is attached to a lower surface of the substrate so as to surround the gas sensor, and an opening for introducing gas is provided at a position below the gas sensor in the cover. A gas detection device for controlling outside air introduction of an automobile, wherein an opening for drain is provided at a lower end of the cover, and a ventilation hole is provided in a substrate between the gas sensor and an inner circumference of the cover. 2. The gas detecting device for controlling outside air introduction of an automobile according to claim 1, wherein the ventilation hole is a hole smaller than an opening for introducing gas, and a plurality of ventilation holes are provided. 3. The gas detecting device for controlling outside air introduction of a vehicle according to claim 1, wherein a plurality of openings for introducing gas are provided on a side surface of the cover.