JP3587326B2 - Gas detector - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas detection device, and for example, to a gas detection device used for detecting exhaust gas from an automobile.
[0002]
[Prior art]
It is known that a gas detection element made of a semiconductor for detecting a specific gas in the atmosphere can detect a reducing gas such as HC or CO contained in exhaust gas of an automobile. Therefore, a gas detection device using this gas detection element is attached to, for example, an outside air intake of an automobile as a sensor for switching between inside and outside air of an air conditioner.
[0003]
However, this type of gas detection device is often installed in, for example, an engine room of an automobile due to the necessity of taking in outside air, and is easily subjected to rain, water during car washing, and the like. Therefore, in order to prevent the built-in control circuit and the like from being exposed to water, a structure (hereinafter referred to as a “waterproof structure”) that prevents water and the like from entering from outside, except for the outside air inlet and outlet, is generally adopted. It has been targeted.
[0004]
[Problems to be solved by the invention]
However, according to the gas detection device adopting the waterproof structure described above, when a microcomputer (hereinafter, referred to as a “microcomputer”) is used for a control circuit, a stable power supply voltage is supplied to the microcontroller, so that a constant voltage that generates heat is generated. The circuit also needs to be housed in the gas detector together with the control circuit. In addition, there is a design constraint that the constant voltage circuit and the microcomputer must be arranged in a close positional relationship to ensure stable operation of the microcomputer. On the other hand, since the control circuit and the constant voltage circuit are accommodated in the sealed space having the waterproof structure, the constant voltage circuit cannot be cooled by the airflow flowing from outside the casing. For this reason, the constant voltage circuit that generates heat cannot be efficiently cooled, and the temperature around the control circuit including the microcomputer tends to increase.
[0005]
The problem that the temperature around the control circuit is likely to increase can be solved by, for example, attaching a heat radiation plate having high heat radiation efficiency to the heat generating portion of the constant voltage circuit. However, according to this configuration, since the size of the heat radiating plate generally increases with the improvement of the heat radiation efficiency, a sealed space capable of accommodating the heat radiating plate having a large size is required. Therefore, there is a new problem that the size of the gas detection device is increased.
[0006]
In addition, in the conventional gas detection device, when a relatively large particle size, snow, or the like enters from the outside air intake port that takes in outside air, the outside air passage may be blocked by accumulation or growth of the entered foreign matter, snow, or the like. there were. Then, since the outside air passage cannot be taken in due to the obstruction of the outside air passage, there has been a problem that a malfunction of the gas detection device may be caused.
[0007]
An object of the present invention is to provide a gas detection device that can efficiently radiate heat from a circuit unit that controls a gas detection element and can be downsized.
Another object of the present invention is to provide a gas detection device for preventing a blockage of an outside air passage.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention employs the means described in claim 1.
According to this means, the housing of the gas detection device has, in addition to the outside air passage accommodating the gas detection element, a cooling outside air passage accommodating a circuit for controlling the gas detection element. Thus, the circuit portion can be cooled by the cooling air taken in from the cooling air inlet. Therefore, even if this circuit portion generates heat, the heat dissipation of the circuit portion can be efficiently performed without using a heat dissipation plate or the like having a high heat dissipation efficiency, thereby preventing an increase in size due to a heat dissipation plate or the like having a high heat dissipation efficiency. That is, there is an effect that heat is efficiently dissipated from the circuit portion and the physique is reduced in size.
[0009]
By adopting the means described in claim 2, the cooling outside air outlet is located above the cooling outside air inlet in the direction of gravity, and the internal pressure of the cooling outside air outlet is lower than the internal pressure of the cooling outside air inlet. As a result, even if water, foreign matter, or the like attempts to enter the inside from the cooling external air outlet located on the upper side in the gravity direction, the internal pressure of the cooling external air outlet is lower than the internal pressure of the cooling external air inlet. Water, foreign matter, and the like are pushed outward by the outside air. Therefore, it is possible to prevent water, foreign matter, and the like that are to enter the inside from entering the outside air passage and the cooling outside air passage. For this reason, the waterproof structure in which the space for accommodating the circuit portion and the like is sealed by an O-ring or the like can be changed to a structure that does not require a sealing member such as an O-ring. Therefore, there is no need for a sealing member such as an O-ring, so that the number of parts can be reduced.
[0010]
By adopting the means described in claim 4 , an intruder selection means is provided at the outside air inlet, so that, for example, a foreign substance having a predetermined particle diameter or water or the like having a predetermined amount or more is invaded by the intruder selection means. Can be prevented. Thereby, since the outside air passage is prevented from being clogged by the invading foreign matter and is not wetted, there is an effect that operation failure can be avoided.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
One embodiment of the gas detection device of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a gas detector 1 detects the concentration of odorous gas components such as HC and NOx in the outside air by a gas sensor 2, and as shown in FIG. 2, a detection signal corresponding to the detected gas concentration. Is output to an electronic control unit (hereinafter, referred to as “ECU”) 102 mounted on the vehicle. The ECU 102 outputs a control signal to an actuator 104 for driving an inside / outside air switching damper 103 of the inside / outside air switching device shown in FIG. 2 in accordance with the gas concentration detected by the gas detection device 1, and controls the same.
[0012]
As shown in FIG. 2, the inside / outside air switching device includes an inside / outside air switching damper 103 that selectively opens and closes an inside air introduction port 105a and an outside air introduction port 105b formed in the inside / outside air switching box 105, and an inside / outside air switching damper. And an actuator 104 (for example, a servomotor) for driving the motor 103. The inside / outside air switching box 105 is disposed at an upstream end of a duct 106 that guides air into a vehicle interior, and is configured integrally with a blower case 107 a of a blower 107.
[0013]
As shown in FIG. 1, the gas detection device 1 is disposed, for example, between a front grill of a vehicle (not shown) and a radiator, and is mounted on a front grill via a mounting hook provided on a front surface of a casing. I have. In the following description, when specifying the top (anti-gravity direction) and the ground (gravity direction) of the mounting direction of the gas detection device 1 with respect to the front grill, the upper direction indicates the top direction and the lower direction indicates the ground direction in FIG. It shall be.
[0014]
The gas detection device 1 includes a housing 13, a cover 5, a separator 7, a filter 6, a gas sensor 2, a circuit board 3, and the like.
The housing 13 as a casing, the cover 5 and the separator 7 are made of resin. The housing 13 is formed in a box shape, and the lower end thereof is provided with an outside air inlet 10 on the front and lower surfaces of the housing 13. Further, the outside air is directed from the front of the lower end of the housing 13 to the rear (to the right in FIG. 1). The outside air introduction path 11 for introducing the air is formed. Here, the outside air inlet 10 corresponds to an “outside air inlet” and a “cooling outside air inlet” described in the claims. That is, in the present embodiment, a configuration is adopted in which the “outside air inlet” and the “outside air inlet for cooling”, which are part of the components of the present invention, are shared.
[0015]
The outside air introduction passage 11 includes a front air intake 10a, a bottom air intake 10b, and a baffle 12 that are open on the front and bottom surfaces of the housing 13. The baffle 12 as the intruder selecting means is set so that the cross-sectional areas of the front and lower air inlets 10a and 10b are substantially the same, and the opening area on the inner (rear) side of the vicinity of the inlet is smaller. (A cross-sectional area of the passage). In addition, the lower surface air inlet 10b also has a role of an outlet for discharging water or the like that has entered the casing to the outside.
[0016]
As shown in FIG. 4, a connector 16 for electrically connecting the built-in circuit board 3 and the ECU 102 is formed integrally with the housing 13 on a side surface of the housing 13.
On the other hand, as shown in FIGS. 1 and 4, the cover 5 is formed so as to be fittable on the outer periphery of the housing 13, and has a claw 13 b provided on the outer periphery of the housing 13 and a hook 5 a provided on the outer periphery of the cover 5. Are attached to the housing 13 by the engagement of The cover 5 is provided with an air outlet 17, a filter holding portion 18, a holding rib 19, and drain walls 20 and 26.
[0017]
The air outlets 17 are provided on both sides of the upper portion of the cover 5, that is, at two locations in the width direction, respectively, and on the downstream side of the air outlets 17, water or the like is prevented from entering the casing from the air outlets 17. A waterproof wall 21 is provided at a position where it enters inside the cover 5. Here, the air outlet 17 corresponds to the “outside air outlet” and the “outside air outlet for cooling” described in the claims. That is, the present embodiment employs a configuration in which the “outside air outlet” and the “outside air outlet for cooling”, which are a part of the components of the present invention, are shared.
[0018]
The filter holding portion 18 holds the filter 6 by holding the upper side surface 6a of the filter 6 housed in the casing, and is formed below the air outlet 17 and is recessed inside the cover 5.
The pressing rib 19 partially holds and holds the lower side surface 6 b of the filter 6, and extends vertically inside the cover 5 below the filter pressing portion 18 so as to protrude.
[0019]
The drain wall 20 is for forming a part of a later-described detection air passage 22 into a maze structure, and protrudes from the holding rib 19 so as to extend in the width direction to the inside of the cover 5.
As shown in FIGS. 1, 2 and 5, the separator 7 constituting a part of the casing is formed in a shape that can be assembled inside the housing 13. The space inside the casing is divided into a detection air passage 22 in which the gas sensor 2 is accommodated and a cooling air passage 23 in which the circuit board 3 is accommodated by the separator 7 attached to the housing 13.
[0020]
Here, the detection air passage 22 corresponds to an “outside air passage” described in the claims, and the cooling air passage 23 corresponds to a “cooling outside air passage” described in the claims.
A U-shaped groove 8 is formed between the outer peripheral wall of the separator 7 and the inner peripheral wall of the housing 13, for example, with the gap set to about 1 mm or less. In this way, the inside of the casing is partitioned into the board side on which the circuit board 3 is disposed and the passage side into which the outside air flows, and the front and bottom air inlets 10a are provided between the separator 7 and the cover 5 on the passage side. , 10b and the air discharge port 17 are formed as a detection air passage 22 (a part of the outside air introduction passage 11 described above).
[0021]
As shown in FIG. 3, the thickness of the gas detection device 1 is integrally formed with the U-shaped groove 8 at the tip of the U-shaped groove 8 of the separator 7 (the contact portion between the bottom of the housing 13 and the separator 7). A thin elastic wall 9 is formed in a direction perpendicular to the U-shaped groove 8, that is, in a direction perpendicular to the U-shaped groove 8, and the front end thereof is elastically pressed against the inner wall of the housing 13. A plate-shaped substrate support member 13a that presses a circuit board 3 described below against the separator 7 is formed integrally with the housing 13 in a direction of the elastic wall 9 in the casing. The substrate support member 13a and the elastic wall 9 are close to each other and are located in a so-called nesting state, thereby forming a passage having a maze structure with a very narrow passage width.
[0022]
Thereby, the gap formed between the substrate supporting member 13a and the elastic wall 9 and the gap formed between the elastic wall 9 and the inner wall of the housing 13 cause a meandering passage as shown by a dotted arrow in FIG. Is formed to secure the cooling air passage 23 flowing out from the cooling air passage 23 described above. By making the passage width of the cooling air passage 23 narrower and having a maze structure in this way, water that has entered the casing from the air discharge port 17 located on the upper side in the direction of gravity can reach the housing space of the circuit board 3. Prevents inflow.
[0023]
Further, as shown in FIG. 1, the separator 7 is provided with a drain wall 25, a drain wall 26, a filter support member, and the like.
The drain wall 25 is formed in a C shape on both left and right sides of the communication hole 24, and further has an end extending along the inner wall surface of the housing 13.
The drain wall 26 is for forming the detection air passage 22 into a maze structure together with the drain wall 20 provided on the cover 5, and protrudes below the separator 7 in the width direction.
[0024]
The filter support member includes four protrusions 27 formed to support the upper end surface 6c and the lower end surface 6d of the filter 6, and two side walls formed to support the left and right side surfaces 6e and 6f of the filter 6. 28. The upper side of the side wall 28 is a portion where the end of the drain wall 25 described above extends along the inner wall surface of the housing 13. A passage 29a is formed.
[0025]
The filter 6 is made of a fibrous material and removes dust contained in the outside air flowing into the casing. The filter 5 is compressed and fixed between the cover 5 and the separator 7 by the above-described filter support member, the filter pressing portion 18 and the pressing rib 19. The length of the side surface (upper side surface 6a and lower side surface 6b) of the filter 6 is formed longer than the upper end surface 6c and the lower end surface 6d.
[0026]
The gas sensor 2 includes a gas detection element (not shown) made of a metal oxide semiconductor (for example, a small amount of noble metal attached to SnO _{2 as} a main component) and a heater (not shown) for heating the gas detection element to a high temperature. Have been. Then, the gas concentration in the air is detected by utilizing the characteristic that when a predetermined type of gas comes into contact with the detection surface 2a of the gas detection element in a state where the gas is kept at a high temperature, the electric resistance value changes.
[0027]
The gas sensor 2 has its terminals soldered to a circuit board 3 to be described later, and protrudes from a communication hole 24 formed in the separator 7 toward the detection air passage 22. As a result, the detection surface 2a of the gas sensor 2 is exposed to the air flowing through the detection air passage 22. An air retention space 30 is formed around the detection surface 2a (on the detection surface 2a) so that the air flowing through the detection air passage 22 is likely to temporarily stay.
[0028]
A signal processing circuit (not shown) for digitally processing a detection signal of the gas sensor 2 is formed on a circuit board 3 as a circuit unit, and a microcomputer and the like are mounted on the circuit board 3. A power supply IC 3a for supplying a stable power supply voltage to a microcomputer or the like is mounted on the circuit board 3 via a heat sink 3b. The heat radiating plate 3b is for radiating heat generated by the power supply IC 3a. Since the heat radiating plate 3b is cooled by the air flowing through the cooling air passage 23, the size of the fin is made smaller than that of the conventional one. be able to. Accordingly, the heat radiation plate 3b can be reduced in size, so that the physical size of the gas detection device 1 can be reduced. The signal digitally processed by the signal processing circuit is output to the ECU 102 via the connector 16 described above.
[0029]
Next, the operation of the gas detection device 1 will be described with reference to FIGS.
(1) Flow of air flowing through the detection air passage 22 The outside air flowing into the outside air introduction passage 11 from the front and bottom air inlets 10a and 10b flows meandering through a maze structure forming a part of the detection air passage 22. Thereafter, the light passes through the filter 6. As a result, the air from which dust and the like have been removed by the filter 6 temporarily stays in the air holding space 30 and is then discharged from the air outlet 17 to the outside of the casing. At this time, the gas concentration in the air staying in the air staying space 30 is detected by the gas sensor 2, and a digitally processed signal is output to the ECU 102 according to the gas concentration.
[0030]
(2) Flow of air flowing through cooling air passage 23 On the other hand, air flowing through cooling air passage 23 is blown from outside air inlet 10 during traveling. That is, the air is introduced from the front and lower air inlets 10a and 10b and flows into the housing space of the circuit board 3 according to the path indicated by the dotted arrow shown in FIG. Then, as shown in FIG. 6, after flowing around the power supply IC 3a and its heat radiating plate 3b (dotted arrow in FIG. 6), the air outlet is passed through the above-described route shown in FIG. 3 (dotted arrow in FIG. 3). It is discharged from 17. The reason why the cooling air passing through the cooling air passage 23 is discharged from the front and lower air inlets 10a and 10b to the air outlet 17 is that when the vehicle is running, the cooling air flows from the outside air inlet 10 into the casing. This is because the internal pressure of the front and lower air inlets 10a and 10b becomes higher than the internal pressure of the air outlet 17 due to the blown air flow. As a result, even if water or the like that is wet from the air discharge port 17 attempts to flow into the casing, the differential pressure prevents water or the like from entering, so that water easily enters the casing from the air discharge port 17. Absent. Even if water enters through the air outlet 17, it can be drained out of the casing by the route described in the following (3).
[0031]
(3) Flow of water or the like entering from the air outlet 17 If the entire gas detection device 1 is wet, water enters the casing through the air outlet 17 or the fitting gap between the housing 13 and the cover 5. 4, the water can be drained through the drain passage 29a formed on the side of the filter 6 along the path indicated by the solid arrow shown in FIG.
[0032]
Further, when water that has entered the casing has passed beyond the outer peripheral wall of the separator 7, that is, the contact portion with the inner peripheral wall of the housing 13, the water is trapped in the U-shaped groove 8. In other words, the U-shaped groove 8 has the drainage passage 29b communicating with the lower surface air inlet 10b on the side between the inner wall of the housing 13 and the drainage passage 29a, like the drainage passage 29a described above. The water trapped in the U-shaped groove 8 can be discharged from the lower surface air inlet 10b in the same manner as the drainage passage 29a described above by the path indicated by the solid line arrow shown in FIG.
[0033]
Further, when the intruded water enters the space 8a between the inner wall of the housing 13 and the outside of the L-shaped elastic wall 9 at the tip of the separator 7 beyond the U-shaped groove 6, the space 8a is formed on the inner wall of the housing 13. As with the U-shaped groove 8, a drain passage 29c communicating with the lower surface air inlet 10b is provided on the side. Therefore, similarly to the above-described drain passages 29a and 29b, water that has entered the casing can be discharged (see solid arrows shown in FIGS. 6 and 7).
[0034]
As described above, according to the present embodiment, the casing of the gas detection device 1 includes, in addition to the detection air passage 22 that houses the gas sensor 2, the cooling air passage 23 that houses the circuit board 3 that controls the gas sensor 2. Have. Thus, the power supply IC 3a that generates heat on the circuit board 3 and the heat radiating plate 3b thereof can be air-cooled by the cooling air taken in from the outside air inlet 10. Therefore, the power supply IC 3a and the heat radiating plate 3b can be efficiently radiated without using a heat radiating plate having a high heat radiating efficiency. Therefore, a heat radiating plate having low heat radiation efficiency, that is, a small heat radiating plate can be used, and there is an effect of reducing the size of the gas detection device 1 in size.
[0035]
According to the present embodiment, the air outlet 17 is located above the outside air inlet 10 in the direction of gravity, and the internal pressure of the air outlet 17 is lower than the inside pressure of the outside air inlet 10 during running of the vehicle. As a result, even if water or the like that is wet from the air discharge port 17 tries to flow into the casing, the differential pressure prevents water or the like from entering, so that water does not easily enter the casing from the air discharge port 17. effective.
[0036]
Further, according to the present embodiment, a baffle 12 smaller than the cross-sectional area of the outside air inlet 10 is disposed at or in front of the outside air inlet 10. This reflects or scatters all or part of the water that enters directly and linearly, such as high-pressure running water for car washing, to reduce the impact energy of the water. It has the effect of preventing. The baffle 12 functions similarly for snow. In other words, even if snow enters the casing, it has a structure in which it falls from the lower surface air inlet 10b having a predetermined size, so that it does not accumulate in the outside air inlet passage 11 and the air inlet 10 or the outside air inlet passage 11b. This has the effect of preventing clogging.
[0037]
Furthermore, according to the present embodiment, since the detection air passage 22 is provided with a maze structure that makes the air flow meander below the filter 6, moisture is introduced into the air introduced from the outside air introduction passage 11. Even if it is included, the infiltration of moisture can be prevented by the drain walls 20, 26 constituting the maze structure. That is, when the air containing moisture passes through the maze structure from below to above, the moisture is rebounded by the drain walls 20 and 26 and falls downward, and can be directly discharged from the air intake 10b of the outside air introduction path 11. it can.
[0038]
Further, according to the present embodiment, since the drainage passage is provided by the three drainage passages 29a, 29b, and 29c, the water that has entered the casing can be discharged in three stages. This eliminates the need for the O-ring, which is essential in the conventional sealed waterproof structure, and can eliminate it. Therefore, there is an effect of reducing the number of parts by eliminating the O-ring.
[0039]
In the above-described embodiment, a predetermined gap is formed between the cover 5 and the lower side surface 6b of the filter 6 in order to make the side surface pressed by the pressing rib 19 of the cover 5 a ventilation surface. In the present invention, without being limited to this, a gap may be formed between the filter and the separator, and the side surface (lower surface side) on the separator side may be used as the ventilation surface. Further, gaps may be formed between the lower side surface and the side surface of the filter and the cover and the separator.
[0040]
Further, in the present embodiment, an example in which the inside / outside air switching device is controlled in accordance with the gas concentration detected by the gas detection device 1 has been described. However, the present invention is not limited to this. Is installed in the cabin to detect the gas concentration of the inside air (vehicle interior air) and control the air purifier to be activated when the inside air pollution level rises, or to increase the inside air pollution level. In such a case, the inside / outside air switching device may be controlled so that the outside air mode is set.
[0041]
Further, in the present embodiment, the intruder selecting means is constituted by the plate-shaped baffle 12, but the present invention is not limited to this, and may be constituted by a net-like member such as a sieve net.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a gas detection device.
FIG. 2 is a schematic diagram of an inside / outside air switching device.
FIG. 3 is an enlarged view of a dashed line III shown in FIG.
FIG. 4 is a sectional view taken along line IV-IV shown in FIG. 1;
FIG. 5 is a sectional view taken along line VV shown in FIG. 1;
FIG. 6 is a sectional view taken along line VI-VI shown in FIG. 1;
7 is a sectional view taken along line VII-VII shown in FIG.
[Explanation of symbols]
1 gas detection device 2 gas sensor (gas detection element)
3 circuit board (circuit part)
5 Cover (casing)
6 Filter 7 Separator (casing)
8 U-shaped groove 10 outside air inlet (outside air inlet, outside air inlet for cooling)
11 outside air introduction channel 12 baffle (intruder selection means)
13 Housing (casing)
17 Air outlet (outside air outlet, outside air outlet for cooling)
22 Detected air passage (outside air passage)
23 Cooling air passage (outside air passage for cooling)

Claims (10)

A gas detection element capable of detecting a predetermined type of gas,
A circuit unit for controlling the gas detection element,
An external air passage accommodating the gas detection element between the external air inlet and the external air outlet, and a cooling external air passage accommodating the circuit unit between the external air inlet for cooling and the external air outlet for cooling. A casing,
With
The outside air introduction port and the outside air introduction port for cooling are provided below the casing in the direction of gravity, and at least one of the outside air introduction port and the outside air introduction port for cooling is provided on the lower surface of the casing downward in the direction of gravity. A gas detection device comprising: an open lower surface inlet; and a front inlet that opens to the front of the casing for the outside air flow. 2. The cooling external air outlet is located above the cooling external air inlet in the direction of gravity, and the internal pressure of the cooling external air outlet is lower than the internal pressure of the cooling external air inlet. Gas detector. The outside air outlet and the outside air outlet for cooling are provided above the casing in the direction of gravity, and a waterproof wall is provided on at least one of the outside air outlet and the outside air outlet for cooling. 3. The gas detection device according to 1 or 2. The gas detection device according to any one of claims 1 to 3, wherein an intruder selection means is provided at the outside air inlet. The gas detection device according to any one of claims 1 to 4, wherein an intruding object selection unit is provided at the cooling outside air inlet . The gas detecting device according to claim 4, wherein the intruder selecting unit is a plate-shaped member or a net-shaped member. The gas detection device according to any one of claims 1 to 6, wherein the outside air passage on the upstream side of the gas detection element has a maze structure. The gas detection device according to any one of claims 1 to 7, wherein the cooling outside air passage downstream of the circuit unit has a maze structure. The gas detection device according to any one of claims 1 to 8, wherein the gas detection element is housed in an air retention space of the outside air passage. The casing has a separator that partitions the outside air passage and the outside air passage for cooling, and the outside air inlet and the outside air inlet for cooling, and the outside air outlet and the outside air outlet for cooling are common. The gas detection device according to at least one of claims 1 to 9, wherein:

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