JP2003057203A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor that can be miniaturized and at the same time can increase the number of elements that can be mounted on a sensor board. SOLUTION: The inner surface of a casing 19 for accommodating a sensor unit 9, which includes a sensor element module 5 and a sensor board 3 set as an annular wall section 19d. At least a gap DS is formed between an inner surface 19d of the casing and the sensor unit 9. Then, the sensor element module 5 is to be assembled to the sensor board 3 so as to include a non-mount section 5b with the sensor element module 5 being arranged, while straddling over the gap DS and the sensor board 3.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas sensor.

[0002]

2. Description of the Related Art Many automobiles are equipped with a duct (outside air duct) for taking in outside air and a duct (inside air duct) for taking in and circulating outside air in a duct connected to the inside of the vehicle. A flap is used to switch between these ducts.When the air outside the vehicle is relatively clean, the flap closes the inside air duct to take in outside air, and on the contrary, it runs on a road with heavy traffic or runs in a tunnel. When doing so, the outside air duct is closed by a flap so that the outside air containing a large amount of exhaust gas does not enter the inside of the vehicle to circulate the inside air. Switching of the inside / outside air mode by opening / closing the flap is a manual type in a general automobile, and a driver or a passenger carries out an appropriate operation according to a traveling environment.

However, the manual switching is often forgotten, and there is often a case where the user enters the tunnel in the outside air mode and the odor of exhaust gas is trapped inside the vehicle and then rushes to switch to the inside air mode. Also,
There is a case where air contaminated due to a sudden factor is inevitably taken into the vehicle. For example, it is common for anyone to experience a situation in which a diesel vehicle running in the adjacent lane suddenly ejects a large amount of black smoke from the exhaust pipe at a very close distance. If you switch modes, you will be a prey.

Therefore, a change in the exhaust gas concentration in the outside air is detected by a gas sensor, and when a change in the exhaust gas concentration above a predetermined level is detected, the flaps are automatically opened / closed to control the inside / outside air mode. The mechanism is installed in recent high-grade car models.

[0005]

The gas sensor as described above is often provided on the way of the duct for the outside air, but since the duct is a very narrow passage, miniaturization of the gas sensor is required. On the other hand, as the demand for higher performance of the gas sensor increases, for example, if the substrate area is increased in order to increase the number of electronic components mounted on the sensor substrate to obtain the output, the gas sensor may become large. Further, if the substrate is simply downsized to meet the miniaturization, the number of mounted electronic components must be reduced, and the output characteristics up to now cannot be satisfied.

An object of the present invention is to provide a gas sensor which can be miniaturized and can increase the number of electronic parts mounted on a sensor substrate to obtain an output.

[0007]

In order to solve the above problems, a gas sensor according to the present invention comprises a sensor substrate and a sensor element module that is integrally assembled with the sensor substrate and includes a gas sensor element. A sensor unit, and a casing having a gas introduction opening for allowing the gas sensor element to come into contact with the gas to be detected, the casing being an enclosed space of the sensor unit, and the casing inner surface and the sensor substrate. A gap is formed at least between the sensor element module and the sensor element module, and the sensor element module is assembled to the sensor substrate so as to be disposed across the gap and the sensor substrate.

According to such a gas sensor, among the components that can be mounted or placed on the sensor substrate, a relatively large-sized sensor element module is arranged across the gap between the sensor substrate and the inner surface (wall portion) of the casing. Since the sensor element module is configured to be assembled as described above, at least the non-mounting portion that is not mounted or mounted on the sensor substrate is formed in the sensor element module. In this case, it is possible to increase the mountable area of electronic parts on the sensor substrate by the amount of the non-mounting part, as compared with the case where the entire sensor element module is simply mounted on the sensor substrate without forming the non-mounting part. On the other hand, when the same electronic component as the conventional one is mounted, the sensor substrate can be downsized.
Therefore, while the gas sensor itself can be downsized as the sensor substrate is downsized, when the same sensor substrate is used in the conventional configuration (configuration that does not span the gap), the sensor substrate electronic It is possible to increase the mountable area of components, and it becomes possible to mount the same or more electronic components as the conventional one, even if the board becomes smaller than the conventional one.

The casing may include a substrate surrounding portion surrounding the outer circumference of the sensor substrate, and the substrate surrounding portion may include at least a curved wall portion. Usually, many sensor substrates have a rectangular shape, but in the present invention, for example, the outer periphery of a rectangular substrate is surrounded by the substrate surrounding portion of the casing, and bulges outward in the radial direction of the substrate surrounding portion. At least a gap (dead space) is formed between the curved wall portion and the outer circumference of the sensor substrate. Here, by providing the curved wall portion in the casing as described above, it is possible to reduce the size of the entire case as compared with the rectangular casing, and to form between the curved wall portion and the sensor substrate. By arranging the sensor element modules across the gaps, the minimum gap (dead space) can be effectively utilized. That is, in the structure in which the sensor element module is arranged across the gap, the curved wall portion is provided in the substrate surrounding portion so as to bulge outward in the radial direction while the gas sensor is downsized, and the curved wall portion is provided. It is possible to effectively use the dead space formed between the portion and the outer periphery of the rectangular substrate. The dead space can be effectively used in a case where a part or the whole of the substrate surrounding portion of the casing is curved or annular.

The casing has a first casing portion and a second casing portion that are integrally fitted to each other at a fitting surface that divides the enclosed space, and the first casing is provided along the fitting surface. A seal member may be provided to seal the portion and the second casing portion. In this case, by constructing the casing separately, the assembly of the gas sensor is further facilitated, and since the fitting surface is sealed by the seal member, the airtightness of the fitting is improved. Further, since the airtightness can be improved only by fitting the first casing portion and the second casing portion using the seal member, the manufacturing process is extremely simplified. In addition, a part or all of the substrate surrounding portion of the casing is formed in a curved shape or an annular shape, and the sealing member is also formed in a curved shape or an annular shape in accordance with the curved or annular portion. Then, it becomes possible to mutually realize miniaturization, airtightness improvement, and manufacturing simplification of the gas sensor.

The sensor element module may be provided so as to project from a plate surface on one side of the sensor substrate. In this case, since the sensor element module is provided so as to project in the thickness direction of the sensor substrate,
Even in a small gas sensor, the detection space for the gas to be detected can be reliably secured inside the casing (enclosed space), and the responsiveness of the sensor can be improved.

The casing is formed so as to project from a first surface of the casing, and is formed so as to project from a module accommodating portion which is an accommodating portion of the sensor element module and a second surface of the casing, and outputs an output signal from the gas sensor element. And a terminal connector portion for taking out. The terminal connector part is a relatively large part that is formed so as to project from the gas sensor, but if this is formed so as to project from the same surface as the module housing part, the casing must be made larger, and the gas sensor becomes larger. Problems may arise. Therefore, it is possible to further reduce the size of the gas sensor by disposing the sensor element module across the gap between the sensor substrate and the above-mentioned gap as described above, and by mounting the terminal connector portion so as to project from a surface different from the module housing portion. Becomes

The reference numerals given to the respective requirements in the claims of the present specification are used with reference to the reference numerals attached to the corresponding portions in the accompanying drawings, but the understanding of the invention is easy to understand. However, the concept of each constituent element in the claims is not limited at all. Further, the description of the claims to which the reference numerals are given will be substituted for the explanation of the reference numerals.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a gas sensor 1 used in a vehicle according to an embodiment of the present invention in a disassembled state, and FIG. 2 is a schematic sectional view conceptually showing an internal structure in the assembled state. is there. Moreover, FIGS.
Shows schematically the appearance of the gas sensor 1 in the assembled state,
They are a perspective view, a front view, a plan view, and a side view, respectively.

As shown in FIG. 2, the gas sensor 1 basically comprises two parts, a sensor unit 9 and a casing 19. As shown in FIG. 1, the sensor unit 9 includes a sensor substrate 3, a sensor element module 5 integrally assembled to the sensor substrate 3, and a sensor output processing circuit for processing an output signal from the sensor element module 5. And part 7. Further, the casing 19 includes a gas introduction opening 13 for allowing the gas sensor element 11 incorporated in the sensor element module 5 to come into contact with the gas to be detected, and a module housing portion 19c for housing the sensor element module 5. And a terminal connector portion 15 for taking out an output signal from the gas sensor element 11 via the sensor output processing circuit 7, and the inside is a sealed space 17 of the sensor unit 9. A microcomputer 75 forming a part of a sensor output processing circuit 7, which will be described later, is mounted on the bottom surface of the sensor substrate 3 opposite to the front surface thereof, but the illustration thereof is omitted.

Here, as shown in FIGS. 1 and 2, and further in FIGS. 4, 5, and 7, the module accommodating portion 19c is formed so as to project from the surface P of the lid-like portion 37 of the casing 19, and the terminal connector portion is formed. 15 is the surface Q of the bottom 31 of the casing 19.
Is formed to project from. That is, the module housing portion 19c and the terminal connector portion 15 are formed so as to project from different surfaces. In the gas sensor 1, the module accommodating portion 19c and the terminal connector portion 15 are relatively large components that are formed to project from the gas sensor 1, but if these are formed to project in the same direction from the same surface, the casing 19 is formed. It becomes necessary to increase the width in the width direction, which may cause a problem of increasing the size of the gas sensor.
Therefore, the terminal connector portion 15 and the module housing portion 19c
Providing and in such a manner as to project in opposite directions from opposite surfaces makes it possible to use the substrate surface more effectively than in the conventional case.

The sensor element module 5 includes an exhaust gas component (oxidizing gas component such as NO _x or NO _x) inside a plastic or metal cap provided with a filter (or activated carbon) inlet gas to be detected. A gas sensor element 11 made of a known metal oxide semiconductor such as SnO ₂ or WO ₃ that changes its electric resistance value by adsorbing a reducing gas component such as CO or HC is incorporated. Figure 1
As shown in, the sensor element 11 is integrally assembled to the sensor substrate 3 by soldering or the like, and is electrically connected to the sensor output processing circuit 7. The gas sensor element 11 may be either a one-element type or a two-element type.

The sensor output processing circuit 7 is, for example, as shown in the block diagram of FIG. 8, a sensor resistance value conversion circuit 7 for detecting a change in electric resistance value of the sensor element 11.
1. A / D that digitizes the output (sensor output potential) from the sensor resistance value conversion circuit 71 every predetermined sampling
The conversion circuit 73 receives the sensor output value from the A / D conversion circuit 73, determines whether or not the change in the output value exceeds a predetermined level, and controls a control unit 100 described later for driving the flap. Which includes a microcomputer 75 for outputting a gas concentration signal LV for
Since all of them are publicly known, detailed description will be omitted. The gas concentration signal LV from the sensor output processing circuit 7 (microcomputer 75) is input to the control unit 100 mainly including a CPU and the like connected via the terminal connector unit 15.
As shown in FIG. 8, the control unit 100 controls the flap 1 based on the gas concentration signal LV from the microcomputer 75.
The actuator 105 of 05 to operate the flap 105
Is rotated to connect either the inside air intake duct 109 for circulating the inside air or the outside air intake duct 107 for introducing the outside air to the duct 101.
A fan 111 that pumps air is installed in the duct 101. Although the sensor output processing circuit 7 of the present embodiment includes the microcomputer 75, the gas sensor may be configured without using the microcomputer 75. In that case, the sensor output processing circuit 7 outputs the sensor output value from the A / D conversion circuit 73 directly to the control unit 100 so that the control unit 100 obtains the gas concentration signal LV. do it.

Returning to FIG. 1, the sensor element module 5 is provided so as to project from the main surface on one side of the sensor substrate 3, and the bottom surface thereof includes a mounting portion 5a mounted on the sensor substrate 3 and a non-mounting portion 5b not mounted. Is included. Note that the sensor element module 5 refers to the peripheral portion including the sensor element 11, and also includes the case where the sensor element module 5 is configured by only the sensor element 11. In addition, as shown in FIG. 2, the casing 19 includes an enclosure space 17 formed to enclose the sensor unit 9, and a casing main body portion 19M for accommodating the sensor substrate 3 and a protrusion formed from the outer surface of the casing main body portion 19M. At the same time, the inside of the casing main body 19M serves as a detected gas introduction space 49 having a smaller volume than the internal space 17a, and the gas introduction opening 13 is formed on the side surface so as to communicate with the detected gas introduction space 49. And the module accommodating portion 19C that is formed. The sensor unit 9 is enclosed in the casing 19 such that the sensor substrate 3 is engaged with the unit assembly portion (mounting portion) 25 of the casing 19. The casing 19 is made of a thermoplastic resin such as nylon 6,6. The sensor unit 9 accommodates the sensor element module 5 in the module accommodating portion 19C of the casing 19, while the sensor substrate 3 is accommodated in the casing main body portion 19M. In addition, the mounting portion 2 is provided in the second casing portion 23.
A pair of unit fixing portions 49 for fixing the sensor unit 9 (sensor substrate 3) placed on the sensor substrate 5 are provided so as to face each other, and the unit fixing portion 49 covers at least the surface of the sensor substrate 3 above. It is supposed to be provided with a fixing surface that is pressed down from the side opposite to the mounting surface.

Here, as schematically shown in FIG. 3, the casing 19 is provided with a substrate surrounding portion 192 surrounding the outer circumference or the outer portion of the sensor substrate 3, and the substrate surrounding portion 192 is at least curved or annular. The wall portion 19d is provided. Specifically, the inner surface of the substrate surrounding portion 192 is an annular wall portion 19d, and at least a gap DS is formed between the inner surface of the casing 19 and the sensor unit 9. In the gas sensor 1 of the present embodiment, the non-mounting portion 5b is arranged so that the sensor element module 5 is disposed across the gap DS and the sensor substrate 3 for the purpose of effectively using the gap DS and downsizing the gas sensor 1. Is assembled to the sensor substrate 3 so as to include. Specifically, the non-mounting portion 5b is arranged so as to be positioned in the gap DS, and the electronic components on the sensor substrate 3 are equivalent to the non-mounting portion 5b in comparison with the case where the non-mounting portion 5b is not provided. It becomes possible to secure a mountable area. Further, when mounting the same electronic component as the conventional one, the sensor substrate 3 can be downsized, and the gas sensor 1 can be downsized.

Next, as shown in FIG. 2, in the projecting direction of the sensor element module 5 from the sensor substrate 3, between the inner front end surface 51 of the module housing portion 19C and the front end surface 53 of the sensor element module 5. A gap GP is formed. Then, the side wall portion 19S of the module housing portion 19C
The gas introduction opening 13 is formed at a position facing the gap GP. Further, a water repellent filter 55 that blocks the permeation of water droplets and permits the permeation of gas is arranged in the gap GP on the rear side of the gas introduction opening 13.
As such a water repellent filter, for example, a porous fiber structure of polytetrafluoroethylene (eg, trade name:
Microtex (Nitto Denko Corporation) or the like can be used.

According to the above structure, the gas introduction opening 13 is formed.
Even if water droplets or the like enter from the above, since the gap GP is formed at the position corresponding to the gas introduction opening 13, a large bend occurs in the path reaching the sensor element module 5,
The water droplets flying at high pressure hit the water-repellent filter 55 in a decelerated state. As a result, it is possible to significantly reduce the probability that the water droplet will pass through the water-repellent filter 55 and reach the sensor element module 5.

Next, in the gas sensor 1 of the present embodiment, the following structural ingenuity is made in order to simplify the assembly process of the sensor. That is, as shown in FIG. 1, the casing 19 has a first casing portion 21 and a second casing portion 23 that are integrally fitted to each other at a fitting surface 18 that divides the enclosed space 17.

At the time of assembling the gas sensor 1, a unit assembly portion (mounting portion) 25 provided in the second casing portion 23
The first casing portion 21 is fitted on the fitting surface 18 with the sensor unit 9 placed on the. Then, as shown in FIG. 2, the first casing portion 21 and the second casing portion 23 are provided along the outer edge of the fitting surface 18.
By inserting the polymer material seal member 27 into the seal member insertion portion 29 formed between the gas sensor 1 and
Can be assembled. Polymer material seal member 2
7 is made of a polymer material such as resin (eg, epoxy resin) or rubber, and is formed by pouring the resin in the uncured state along the outer edge of the mating surface 18 and curing it.

According to this structure, the casing 19
Is divided into a first casing portion 21 and a second casing portion 23, and a unit assembly portion (mounting portion) 25 is formed on the side of the second casing portion 23, where the sensor unit 9 (sensor substrate 3) is formed. By mounting and fixing with the unit fixing part 49, these can be handled as one integrated component. Therefore, the number of substantial parts is reduced, and basically, the two parts of the first casing part 21 and the second casing part 23 with the sensor unit 9 are fitted together, and the seal part is formed by two steps. As a result, the manufacturing cost can be reduced.

Further, as shown in FIGS. 1 and 2, the module accommodating portion 19C is formed so as to project from the surface P of the lid-like portion 37 forming the first casing portion 21 that does not face the enclosed space 17. . Further, the terminal connector portion 15 is formed so as to project from the surface Q of the bottom portion 31 of the second casing portion 23 that does not face the enclosed space 17, and projects in the direction opposite to the module housing portion 19C. As shown in FIG. 1, the terminal connector portion 15 has a sensor output extraction terminal fitting 57 that penetrates the bottom portion 31 in the plate thickness direction. Then, the portion 57a of the sensor output extraction terminal metal fitting 57 projecting to the enclosed space 17 side is inserted into the metal fitting insertion hole 3h formed in the sensor substrate 3 and soldered. That is, when the sensor unit 9 is mounted on the second casing portion 23, the sensor output lead-out terminal metal fitting 57 is also inserted into the metal fitting insertion hole 3h on the sensor board 3 side at the same time, so that the sensor output take-out terminal metal fitting 57 and the sensor board are connected. After soldering 3 and 1, the first casing portion 21
Is fitted to the second casing portion 23.

The first casing portion 21 and the second casing portion 23 are assembled by engaging the engaging groove 47 provided in the first casing portion 21 and the engaging convex portion provided in the second casing portion 23. It is performed by fitting together with 43. Here, the second casing portion 23 is provided with a lid receiving portion 41,
The first casing portion 21 is prevented from being incorporated below the receiving surface.

Next, a modified example of the gas sensor of the present invention will be described. It should be noted that only the configuration different from the gas sensor 1 will be described, and the configuration of a portion not particularly described has the same configuration as the gas sensor 1. In the gas sensor 200 shown in FIG. 9, especially in FIG.
As shown in FIG.
The surface on which is mounted is formed so as to be flush with the front end surface of the second casing portion 23 or located on the front end side with respect to the front end surface. In this case, it becomes possible to satisfactorily solder the sensor substrate 3 and the sensor output lead-out terminal fitting 57. In this case, the front end side means the front end side on the opening side opposite to the side where the bottom portion 31 of the hollow bottomed second casing portion 23 is formed.

A seal member mounting portion 29, which is a seal member assembling portion, is provided at the tip end side of the tubular portion of the second casing portion 23.
a is formed. In this case, the seal member mounting portion 2
The first casing portion 21 is engaged with the second casing portion 23 in a state where the annular seal member 27a is placed on the 9a. As a result, the seal member 2 is provided along the fitting surface 18 that divides the enclosed space 17 of the casing 19.
7a will be arranged, and more specifically, the sealing member 2
Since 7a is elastically contracted vertically and horizontally, it contributes to the sealing between the first casing portion 21 and the second casing portion 23, so that the sealing property (airtightness) between both members is improved. In addition,
The second casing portion 23 is formed with an engaging groove portion 43a, and the first casing portion 21 is formed with an engaging protrusion portion 47a. By these engagements, both members 21 and 23 are assembled. Further, as the seal member 27a, for example, a polymer annular seal member (so-called O-ring) made of resin, rubber or the like can be used.

Further, particularly as shown in FIG. 9A, a duct fixing flange portion 201 which is an attachment portion for attaching the gas sensor 200 to the outside air duct 107 (see FIG. 8) is formed in the first casing portion 21. Has been done. Specifically, the duct fixing flange portion 201 is intermittently formed in the circumferential direction of the first casing portion 21, and after the duct fixing flange portion 201 is inserted into the mounting hole formed in the outside air duct 107. By rotating the casing 19 in the circumferential direction by a predetermined angle, the gas sensor 200 is fixed to the outside air duct 107 in a form in which the duct fixing flange portion 201 is attached to the attachment hole of the outside air duct 107.

It should be noted that the second casing portion 23 has a structure shown in FIG.
As shown in FIG. 3, the substrate mounting portion 25, which is a unit mounting portion, is attached to the sensor unit 9 from the opening side of the second casing portion 23.
A mounting surface facing the tip side is formed so that the (sensor substrate 3) can be mounted. Further, a pair of unit fixing portions 202 for fixing the mounted sensor unit 9 (sensor substrate 3) are provided facing each other, and the unit fixing portion 202 at least covers the surface of the sensor substrate 3 of the above-mentioned mounting portion 25. It is supposed to be provided with a fixing surface that is pressed down from the side opposite to the mounting surface. In addition, in FIG. 10, the illustration of the engaging groove portion 43a is omitted.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a gas sensor of the present invention and an explanatory view showing a configuration relating to assembly.

FIG. 2 is a schematic cross-sectional view showing the configuration of the gas sensor of FIG. 1 during assembly.

FIG. 3 is an explanatory view showing a configuration at the time of assembling the gas sensor of FIG.

FIG. 4 is a perspective view schematically showing the external appearance of the gas sensor in an assembled state.

FIG. 5 is a front view schematically showing the outer appearance of the gas sensor in an assembled state.

FIG. 6 is a plan view schematically showing the outer appearance of the gas sensor in an assembled state.

FIG. 7 is a side view schematically showing the outer appearance of the gas sensor in an assembled state.

FIG. 8 is a view conceptually showing an example of an automatic flap switching mechanism using the gas sensor of this embodiment.

FIG. 9 is a perspective view and a cross-sectional view schematically showing a modified example of the gas sensor of the present invention.

10 is a perspective view of a second casing portion of the gas sensor of FIG.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiya Matsuoka             14-18 Takatsuji-cho, Mizuho-ku, Nagoya City, Aichi Prefecture             Inside this special ceramics company F term (reference) 2G046 AA11 AA13 AA22 AA23 BA01                       BB02 BD01 BF05 BG02 BG05                       BH08 DC14 DC16 DC17 DC18                       FA01 FB02 FE39 FE46

Claims (5)

[Claims] 1. A sensor substrate (3) and a gas sensor element (11) assembled integrally with the sensor substrate (3).
A sensor unit (9) having a sensor element module (5) provided with a sensor unit module (5), and an interior space (17) for the sensor unit (9), wherein the gas sensor element (11) contacts the gas to be detected A casing (19) having a gas introduction opening (13) for allowing the gas, and at least a gap (DS) is formed between the inner surface of the casing (19) and the sensor substrate (3). A gas sensor (1,200), characterized in that an element module (5) is assembled to the sensor substrate (3) so as to be disposed across the gap (DS) and the sensor substrate (3). 2. The casing (19) includes a substrate surrounding portion (192) surrounding the outer circumference of the sensor substrate (3), and the substrate surrounding portion (192) includes at least a curved wall portion (19d). The gas sensor (1,
200). 3. The casing (19) includes a first casing part (21) and a second casing part (23) which are integrally fitted to each other at a fitting surface (18) which divides the enclosed space (17). ) And the fitting surface (1
8) A seal member (2) for sealing the first casing part (21) and the second casing part (23) along
Gas sensor (1,200) according to claim 1 or 2, provided with 7,27a). 4. The gas sensor (1,200) according to claim 1, wherein the sensor element module (5) is provided so as to project from a plate surface on one side of the sensor substrate (3). 5. The module (19), which is a housing for the sensor element module (5), is formed in the casing (19) so as to project from the first surface of the casing (19), and the casing (19). 19) is formed so as to project from the second surface,
The gas sensor (1, 20) according to any one of claims 1 to 4, further comprising a terminal connector portion (15) for extracting an output signal from the gas sensor element (11).
0).