JP2001296196A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an atmospheric pressure introduction passage from being choked by preventing the filter section from being clogged in a pressure sensor where the atmospheric pressure on the outside of the case is introduced to an encased sensor element section through the filter section. SOLUTION: An atmospheric pressure introduction opening 10 opening to the outside is made in the surface of a case 1 and fixed with a water repellent filter 12 for blocking passage of dust and water while allowing air flow such that the filter surface is oriented vertically during use of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for introducing an environmental pressure outside a case to a sensor element in the case through a filter provided in the case, and particularly to an environment in which water is severely affected by water. It is suitable for a pressure sensor applied to

[0002]

2. Description of the Related Art A pressure sensor of this type is disclosed in
JP-A-43085 and JP-A-9-43076 have been proposed. In this device, a sensor element for detecting pressure is provided in a case capable of introducing an environmental pressure (atmospheric pressure) and a pressure to be measured, and a differential pressure between these two pressures is detected. A filter (water-repellent filter) for removing dust, moisture, and the like in the atmosphere is interposed and set in the passage into which the environmental pressure is introduced.

[0003]

In the conventional pressure sensor described above, when it is attached to an object to be detected, such as a fuel tank of an automobile, the filter surface of the filter section faces downward (horizontally).
The shape is set to. Therefore, if moisture in the pressure medium (atmosphere) adheres to the filter portion, it is difficult for the moisture to drop due to surface tension, the filter portion is clogged, the introduction path of the environmental pressure is blocked, and the sensor does not function. Occurs. In particular, the above problem becomes remarkable when the environment is severely affected by rain such as rainwater.

[0004] In view of the above problems, the present invention provides a pressure sensor in which the environmental pressure outside the case is introduced to a sensor element disposed in the case via a filter provided in the case. It is an object of the present invention to prevent the filter portion from being clogged and to prevent the introduction path of the environmental pressure from being blocked.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, an inlet (10) for introducing an environmental pressure opening to the outside is formed on the surface of the case (1). In addition, a filter unit (12) is attached to the inlet, and the filter surface is arranged so as to be oriented in the vertical direction when the sensor is used.

According to the present invention, since the filter surface is arranged in the vertical direction (ie, the direction of gravity) when the sensor is used, even if moisture in the environmental pressure medium adheres to the filter portion, the filter surface is placed under its own weight. , Can easily fall off the filter surface. Therefore, it is possible to prevent the filter portion from being easily clogged and to prevent the introduction path of the environmental pressure from being blocked.

According to the second aspect of the present invention, since the filter surface of the filter portion (10) has a convex shape facing the outside of the case (1), the filter surface has a higher moisture content than a flat surface. Surface tension can be reduced, and the attached moisture can be more easily dropped.

According to the third aspect of the present invention, the inlet (10) is constituted by an aggregate of a plurality of openings (21) partitioned by a frame (20), Compared to the case where the inlet is a single opening, there is a frame that partitions the plurality of openings, so that the area in contact with moisture increases, and even a small amount of moisture promotes dew condensation. Therefore, the removal of water can be further promoted in combination with the effect of the invention of claim 1 that the water is easily dropped.

Here, if the plurality of openings (21) are vertically elongated in the vertical direction as in the invention of claim 4, it is possible to make the condensed water easily flow in the vertical direction. Therefore, water can be more easily dropped.

Further, according to the invention of claim 5, a projection (22) protruding to the outside of the case (1) is formed on the frame (20) defining the plurality of openings (21), and the filter section is formed. A gap (23) through which environmental pressure can be introduced is formed between the frame and the filter surface by disposing the filter surface of (12) in contact with the tip of the projection. Since the environmental pressure can be introduced into the gap, even if the filter surface is clogged, the environment pressure can instead be guided from the gap to the sensor element portion (4), which is preferable.

Further, the present inventors have conducted an experimental study on the opening area of the inlet, and found that
If the opening area of the inlet (10) is 90 mm ² or more,
It was confirmed that the effect of the invention of claim 1 can be exerted at a higher level.

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention shown in the drawings will be described below. FIG. 1 is a schematic cross-sectional view showing the entire configuration of the pressure sensor 100 according to the first embodiment of the present invention, and FIG. 2 is a view as seen from the direction of arrow A in FIG. FIG. 3 is an enlarged view of the sensor element unit 4 in FIG.

The pressure sensor 100 introduces an environmental pressure outside the case 1 to a sensor element 4 for pressure detection disposed in the case 1 via a filter section 12 provided in the case 1. For example, the present invention is applied to a fuel tank (not shown) as an object to be detected, with a vertical direction in FIG.

The case 1 is formed, for example, by molding a resin such as PBT (polybutylene terephthalate) or PPS (polyphenylene sulfide). A concave portion is formed in the center of the case 1,
The space inside the recess is divided into a reference pressure chamber 2 into which atmospheric pressure (environmental pressure) is introduced, and a measurement pressure chamber 3 into which a pressure to be measured such as gasoline vapor is introduced. Both rooms 2, 3
Is defined by the sensor element section 4 fixed in the concave portion.

As shown in FIG. 1, a pressure introducing portion 1a projecting in a column shape is formed as a part of the case 1 at a portion of the case 1 opposite to the concave portion. In the pressure introducing section 1a, an introduction path 1b as a path for introducing the pressure to be measured into the sensor element section 4 is provided.
And the outside of the case 1.

On the inner wall of the introduction path 1b, O
A ring 17 and a holding member (spacer) 18 for holding the O-ring 17 in the introduction path 1b are provided. The pressure introducing portion 1a can be connected to the fuel tank itself or a mating member such as a hose or a pipe extended from the fuel tank so as to communicate with the inside of the fuel tank. To prevent leakage of the pressure transmitted from the counterpart member to the introduction path 1b.

As shown in FIG. 3, the sensor element section 4 comprises a pressure-sensitive element 4a made of silicon or the like and a glass pedestal 4b for supporting and fixing the pressure-sensitive element 4a. The pressure-sensitive element 4a has a diaphragm formed on a substrate made of, for example, silicon or the like, and is joined to a glass pedestal 4b having a thermal expansion coefficient similar to that of the pressure-sensitive element 4a.

The glass pedestal 4b has a through hole,
The pressure difference between the atmospheric pressure (environmental pressure) introduced from the reference pressure chamber 2 and the measurement pressure introduced from the measurement pressure chamber 3 is determined by the pressure-sensitive element 4.
"a" is detected.

The sensor element section 4 is fixed to the case 1 via a hollow stem 5 having a through hole. The stem 5 employs a 42-alloy (Fe: Ni = 58: 42) which is a material having a thermal expansion coefficient similar to that of the glass pedestal 4b, and the sensor element portion 4 and the stem 5 are bonded with a thermosetting resin or the like. It is fixed with the agent.

The stem 5 and the case 1 are also fixed with an adhesive such as a thermosetting resin. By fixing the sensor element portion 4 and the stem 5 to the case 1, the measurement pressure chamber 3
Can be transmitted to the back surface of the pressure-sensitive element 4a (the surface on the glass pedestal 4b joining side).

An adhesive such as a thermosetting resin is provided in the concave portion of the case 1 in order to further improve the airtightness of the fixing portion between the sensor element portion 4 and the stem 5 and the fixing portion between the stem 5 and the case 1. 6, and a silicone gel 7 for improving the moisture resistance of the sensor element portion 4. The upper surface of the reference pressure chamber 2 is closed by a lid (lid) 8 made of a resin such as PBT. The lid 8 is airtightly fixed by an adhesive 9.

On the surface of one end of the case 1, an atmospheric pressure inlet (inlet in the present invention) 10 for introducing atmospheric pressure (environmental pressure) is formed by opening to the outside of the case 1. Have been. The case 1 has an atmospheric pressure inlet 1
An atmospheric pressure introduction passage 11 extending from 0 to the reference pressure chamber 2 side is formed, and the atmospheric pressure introduction passage 11 and the reference pressure chamber 2 communicate with each other by a gap between the lid 8 and the case 1. Thus, the reference pressure chamber 2 is open to the atmosphere via the atmospheric pressure inlet 10 and the atmospheric pressure inlet passage 11.

The atmospheric pressure inlet 10 is provided with a sheet-like water-repellent filter made of resin or the like (the filter portion in the present invention).
In the present embodiment, the filter surface is oriented in the vertical direction (that is, the direction of gravity, see FIG. 1) when the sensor 100 is used (that is, when the sensor 100 is attached to the detection target). ).

FIG. 4 is an enlarged view of the vicinity of the atmospheric pressure inlet 10. 4A is an enlarged view in a plane corresponding to FIG. 2, and FIG. 4B is an enlarged view in a cross section corresponding to FIG. 2 and FIG. 4A, the surface of the water-repellent filter 12 is hatched. In the present example, the angle θ between the top and bottom directions shown in FIG. 4B and the filter surface is 0 ° (parallel to the top and bottom directions), but this angle θ is preferably about 0 to 45 °.

The water-repellent filter 12 is a well-known filter obtained by subjecting a fluorine-based resin (such as polytetrafluoroethylene (PTFE)) formed into a porous sheet to a water-repellent treatment, for example. The water-repellent filter 12 is assembled and fixed to the case 1 by a filter fixing member (spacer) 13 having a frame shape (in this example, rectangular shape) corresponding to the outer wall shape of the atmospheric pressure inlet 10. The material of the filter fixing member 13 may be any material, but in this example, the same material as the case 1 is used.

The water-repellent filter 12 is assembled, for example, by attaching the water-repellent filter 12 to the case 1 so as to cover the atmospheric pressure inlet 10.
The filter fixing member 13 presses and fixes the water-repellent filter 12 and the outer wall of the atmospheric pressure inlet 10 so that the filter fixing member 13 is not removed. Thereby, the fixing member 13 is bonded to the case 1. In this way, the water repellent filter 12 and the case 1 are sealed, and the passage of dust, water, and the like into the reference pressure chamber 2 is prevented while allowing the flow of air.

An output terminal for outputting a detection signal of the pressure-sensitive element 4a fixed to the case 1 via the stem 5 is connected to a terminal 15 via a bonding wire 16, and the pressure-sensitive element 4a is It is possible to take out the detected signal to the outside (for example, an ECU of an automobile).

Next, a method of manufacturing the pressure sensor 100 will be briefly described. First, the case 1 is manufactured by molding a resin such as PBT or PPS. At this time,
The terminals 15 are simultaneously insert-molded. Also,
The water-repellent filter 12 is fixed to the manufactured case 1 by the above-described assembling method. Next, the O-ring 17 and the holding member 18 are attached to the pressure introducing portion 1a of the case 1.

Next, the pressure-sensitive element 4a is adhered to the glass pedestal 4b to form the sensor element portion 4. The glass pedestal 4b of the sensor element portion 4 is adhered to the stem 5, and the stem 5
Is bonded to the concave portion of the case 1. As a result, the reference pressure chamber 2 and the measurement pressure chamber 3 are defined in the recess of the case 1. Next, the pressure-sensitive element 4a of the sensor element unit 4
And the terminal 15 is wire-bonded and connected by the wire 16.

Next, the adhesive 6 is injected and filled into the concave portion of the case 1 on the side of the reference pressure chamber 2, and is cured by heat treatment or the like. Next, silicone gel 7 is injected and filled so as to cover the sensor element portion 4 and the wire bonding portion.
Next, the lid 8 is fixed to the upper surface of the reference pressure chamber 2 with an adhesive 9, and the reference pressure chamber 2 is hermetically sealed. Thus, the pressure sensor 100 is completed.

The pressure sensor 100 includes the pressure introduction unit 1
a is connected to the above-mentioned member so as to be sealed via the O-ring 17 and is in use. Then, the measured pressure from the object to be detected (fuel tank) is introduced into the measurement pressure chamber 3 from the introduction path 1b, and the hollow portion of the stem 5, the glass pedestal 4
The light is transmitted from the through hole b to the back surface of the pressure-sensitive element 4a. As described above, the measurement pressure transmitted to the pressure-sensitive element 4a is detected as a differential pressure from the atmospheric pressure (environmental pressure) introduced from the reference pressure chamber 2, and the bonding wire 16 and the terminal 1
5 to the outside.

According to the present embodiment, since the filter surface of the water-repellent filter (filter section) 12 is arranged in the vertical direction when the sensor is used, the water content in the environmental pressure medium (atmosphere) is reduced. Can easily fall off the filter surface due to its own weight even if it adheres to the filter surface. Therefore, the water-repellent filter 12 can be hardly clogged, and the introduction path of the environmental pressure can be prevented from being blocked.

For example, in the pressure sensor 100 attached to the fuel tank, the vehicle is drenched by the water that is wound up from the wheels when the vehicle is running on rainy weather. Even in such an environment, the pressure sensor 100 can prevent the water-repellent filter 12 from being blocked by the adhesion of moisture, so that the function of the sensor is not impaired.

Further, the present inventors have proposed that the atmospheric pressure inlet 10
It is considered that a larger opening area can more effectively exert the above-described blocking prevention effect, and the atmospheric pressure introduction port 10 is designed so that the above-mentioned effect can be effectively exerted even in an extremely harsh environment. Were examined for the opening area. The test method is to immerse the entire pressure sensor 100 in water,
After taking out 00, it was checked whether the water-repellent filter 12 and the atmospheric pressure inlet 10 were closed.

In the pressure sensor 100 of the present embodiment,
The opening area of the atmospheric pressure inlet 10 is 48 mm ² , 90 m
m ² and 150 mm ^2, and as a comparative example, in the pressure sensor described in the above-mentioned conventional publication, the opening area of the atmospheric pressure introduction passage in the filter portion was 28 mm ²
Was created. The above test was performed on a plurality (for example, 4 to 6) of various sensors. The result is shown in FIG.

At least one blockage occurred in the comparative example and 48 mm ² , but not all of the 90 mm ² and 150 mm ² blocks. From this,
If the opening area of the atmospheric pressure introduction port 10 is at least 90 mm ² or more, the above-described blocking prevention effect is effective even in an environment that is more severe than a normal use environment in which the entire sensor is immersed in water. And it was found to be preferable.

(Second Embodiment) The second embodiment is different from the first embodiment in that the configurations of the water-repellent filter 12 and the atmospheric pressure inlet 10 are modified. Differences from the first embodiment will be mainly described, and the same portions will be denoted by the same reference numerals in the drawings and description thereof will be omitted.

FIG. 6 is a view showing a main part of a pressure sensor according to a second embodiment of the present invention, wherein FIG.
FIG. 4B shows a cross section corresponding to FIG. 4B. FIG. 7 is a diagram illustrating a configuration in which the water-repellent filter 12 and the filter fixing member 13 are removed from FIG. 6A, and is a diagram illustrating a detailed configuration of the atmospheric pressure inlet 10.

In the first embodiment, the atmospheric pressure inlet 10
Is constituted by a single opening, but in the present embodiment, as shown in FIG. 6A, the atmospheric pressure introduction port 10 is divided by a frame 20 instead of a single opening. And a plurality of (three in the illustrated example) openings 21. Each opening 21 has a vertically long shape in the vertical direction, and in this example, a long side of the rectangular opening 21 extends in the vertical direction.

Here, of the atmospheric pressure introducing passage 11, a passage extending from the atmospheric pressure introducing port 10 toward the reference pressure chamber 2 (the left-right direction in FIG. 6B) is a first passage 11a, A passage extending from the passage 11a toward the lid 8 (the vertical direction in FIG. 6B) is referred to as a second passage. Then, for example, a plurality of first passages 11a are provided in parallel corresponding to the plurality of openings 21, one second passage 11b is provided, and each first passage 11a joins the second passage 11b. It is possible to adopt a configuration in which these are performed.

In the first embodiment, the filter surface of the water-repellent filter 12 has a substantially flat planar shape. In this embodiment, as shown in FIG. The case 1 has a convex shape facing the outside. Specifically, as shown in FIGS. 6B and 7, a protrusion 22 projecting to the outside of the case 1 is formed on a frame 20 that defines a plurality of openings 21, and the water-repellent filter 12 is formed. Is placed in contact with the tip of the projection 22. This allows
The filter surface can be formed into a convex shape facing the outside of the case 1 according to the height of the protrusion 22.

The pattern of the projection 22 is shown in FIG.
As shown by hatching (not a cross-section), the opening 20 is not formed at a part of the opening edge of each opening 21. Therefore, in the portion where the protrusion is not formed, the portion between the frame 20 and the filter surface is not formed. A gap 23 is formed therebetween. And the atmospheric pressure is
Through the filter surface of the water-repellent filter 12, the water-repellent filter 12 can be introduced into each opening 21 from the gap 23.

By the way, according to the present embodiment, the first
As in the embodiment, the filter unit is hardly clogged,
In addition to the effect of preventing the introduction path of the environmental pressure from being blocked, it has the following various effects. First, since the filter surface of the water-repellent filter 12 has an R-shaped or spherical convex shape facing the outside of the case 1,
The surface tension of water can be reduced as compared with the case where the filter surface is a flat surface.

Therefore, for example, as shown in FIG. 8, even if foreign matter K1 such as moisture or dust adheres to the filter surface of the water repellent filter 12, the foreign matter K1 is more efficiently dropped than a flat filter surface. Can be easier. In the first embodiment as well, the water-repellent filter 12 may be assembled to the case 1 in such a manner that its filter surface is curved so as to have a convex shape facing the outside of the case 1. The effect of is obtained.

In this embodiment, the atmospheric pressure inlet 10
Is constituted by an aggregate of a plurality of openings 21 sectioned by a frame 20, as compared with the case where the atmospheric pressure introduction port 10 is a single opening as in the first embodiment. Due to the presence of the frame 20, the area in contact with atmospheric moisture flowing therethrough increases, and even a small amount of moisture promotes dew condensation.
For this reason, moisture is more easily dropped, and the removal of moisture can be further promoted.

Further, in this embodiment, since the gap 23 through which the atmospheric pressure (environmental pressure) can be introduced is formed between the frame 20 and the filter surface of the water-repellent filter 12, the filter surface is inevitable. Even if is clogged, the atmospheric pressure can be guided to the sensor element portion 4 from the gap portion 23 instead, which is preferable.

For example, as shown in FIG.
Assuming that foreign matter K2 such as mud adheres to the filter surface of the water repellent filter 21 so as to cover 0, the filter surface at the adhered portion is clogged. Here, if there is no gap 23, the opening 20 covered with the foreign matter K2 is closed. In this regard, as shown by hatching in FIG. 9, if the gap 23 exists, communication between the outside and the opening 21 is ensured, so long as foreign matter does not adhere to the entire area of the filter surface and is blocked. In addition, the pressure sensor 100 can prevent the introduction path of the atmospheric pressure from being blocked.

(Other Embodiments) In the above embodiment, the present invention is applied to a relative pressure sensor for detecting a differential pressure between the atmospheric pressure and the pressure to be measured. It can also be applied to a pressure sensor that is introduced into a section and measures atmospheric pressure as absolute pressure.

In short, the present invention relates to a pressure sensor in which an environmental pressure outside the case is introduced to a sensor element disposed in the case via a filter provided in the case. The main part is that the filter surface of the filter unit attached to the inlet formed on the surface is arranged so as to be oriented in the vertical direction when in use, and other parts can be appropriately changed. is there.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an entire configuration of a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a view taken in the direction of the arrow A in FIG.

FIG. 3 is an enlarged view of a sensor element unit in FIG.

FIG. 4 is an enlarged view of the vicinity of an atmospheric pressure introduction port of the pressure sensor according to the first embodiment.

FIG. 5 is a table showing the results of a study on the opening area of the atmospheric pressure introduction port.

FIG. 6 is a diagram showing a main part of a pressure sensor according to a second embodiment of the present invention.

FIG. 7 is a detailed configuration diagram of an atmospheric pressure introduction port of the pressure sensor according to the second embodiment.

FIG. 8 is an explanatory diagram showing the operation and effect of the convex surface configuration of the filter surface.

FIG. 9 is an explanatory view showing the operation and effect of the gap.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Case, 4 ... Sensor element part, 10 ... Atmospheric pressure introduction port,
12 ... water repellent filter, 20 ... frame, 21 ... opening, 22 ...
Protrusion, 23 ... gap.

Claims (6)

[Claims] An environmental pressure outside the case is applied to a sensor element (4) for pressure detection disposed in a case (1) through a filter (12) provided in the case. In the pressure sensor adapted to be introduced, an inlet (10) for introducing the environmental pressure which is open to the outside is formed on a surface of the case, and the filter unit is attached to the inlet. The pressure sensor is characterized in that the filter surface is arranged so as to be oriented in the vertical direction when used. 2. The pressure sensor according to claim 1, wherein the filter surface of the filter section has a convex shape facing the outside of the case. 3. The device according to claim 1, wherein the inlet is formed by an aggregate of a plurality of openings defined by a frame. Pressure sensor. 4. The pressure sensor according to claim 3, wherein the plurality of openings have a shape that is vertically long in the vertical direction. 5. The case (1) is provided in the frame (20).
A projection (22) protruding outward is formed, and a filter surface of the filter (12) is disposed in contact with a tip of the projection, and a gap is provided between the frame and the filter surface. The pressure sensor according to claim 3, wherein a gap portion capable of introducing an environmental pressure is formed. 6. The opening area of the inlet (10) is 90 m.
The pressure sensor according to claim 1, wherein the pressure sensor is at least m ² .