JP4221875B2 - Pressure sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure sensor that introduces an environmental pressure outside a case into a sensor element portion in the case through a filter portion provided in the case, and more particularly to a pressure sensor that is applied to a severely wet environment. Is preferred.
[0002]
[Prior art]
As this type of pressure sensor, one described in Japanese Patent Laid-Open No. 9-43084 has been proposed. In this case, a sensor element portion for pressure detection 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 unit (water repellent filter) for removing dust, moisture, etc. in the atmosphere is interposed in the passage through which the environmental pressure is introduced.
[0003]
[Problems to be solved by the invention]
However, in the prior art, a filter portion for removing foreign substances and moisture has been attached to the pressure introduction path, but intrusion of moisture is inevitable, and further moisture removal is required. For example, in a pressure sensor attached to an object to be detected such as a fuel tank of an automobile, when the environment becomes extremely wet, such as rain water, it is easy for moisture to pass through the filter part in the conventional sensor, and the sensor functions. The possibility of not doing so increases.
[0004]
Therefore, in view of the above problems, the present invention provides a pressure sensor in which an environmental pressure outside the case is introduced to the sensor element portion disposed in the case through the filter portion provided in the case. It aims at improving the moisture removal performance in a part.
[0005]
[Means for Solving the Problems]
Conventionally, the introduction path of the environmental pressure provided with the filter portion has been a single hole (opening). However, the present invention is configured by forming the introduction passage from a plurality of openings partitioned by a frame. This is made by paying attention to the idea that the moisture in the pressure medium will not penetrate into the sensor element portion if the contact area with the substrate is increased and condensation is promoted.
[0006]
That is, in the first aspect of the present invention, the inlet (10) for introducing the environmental pressure that opens to the outside is formed on the surface of the case (1), and the filter portion (12) is attached to the inlet. Furthermore, the introduction port is configured by an assembly of a plurality of openings (21) partitioned by a frame (20).
[0007]
According to the present invention, compared to the case where the inlet is a single opening, there is a frame that divides a plurality of openings, so that the area in contact with moisture increases, and even a slight amount of moisture causes condensation in the filter portion. Promoted. As a result, moisture stops in the filter portion, and moisture becomes less likely to enter the inside of the filter portion, so that the moisture removal performance in the filter portion can be improved.
[0008]
Further, according to the present invention, a frame (20), protruding portions protruding to the outside of the case (1) forming a (22), disposed in contact with the filter surface of the filter unit (12) to the tip of the protrusion Thus, a gap (23) capable of introducing environmental pressure is formed between the frame and the filter surface. Since the environmental pressure can be introduced into the gap portion, it is preferable that the environmental pressure can be guided from the gap portion to the sensor element portion (4) instead if the filter surface is clogged.
[0009]
In addition, the code | symbol in the parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 is a schematic cross-sectional view showing the overall configuration of a pressure sensor 100 according to an embodiment of the present invention, and FIG. 2 is a view seen from the direction of arrow A in FIG. FIG. 3 is an enlarged view of the sensor element portion in FIG. FIG. 4 shows a detailed configuration of the filter section, where (a) is an enlarged view of the vicinity of the filter section in FIG. 2, and (b) is an enlarged view of section B in FIG. FIG. 5 is a diagram showing a configuration in which the water repellent filter 12 and the filter fixing member 13 are removed from FIG. 4A, and a detailed configuration of the atmospheric pressure introduction port 10.
[0011]
The pressure sensor 100 introduces an environmental pressure outside the case 1 to the sensor element portion 4 for pressure detection disposed in the case 1 via a filter portion 12 provided in the case 1. For example, the present invention is applied to a fuel pressure sensor that is attached to a fuel tank (not shown) as a detection target and detects the pressure in the tank.
[0012]
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 central portion of the case 1, and a space in the concave portion is a reference pressure chamber 2 into which atmospheric pressure (environmental pressure) is introduced, and a measurement pressure into which a pressure to be measured such as gasoline vapor is introduced. It is divided into a chamber 3. The compartments of both chambers 2 and 3 are formed by a sensor element portion 4 fixed in the recess.
[0013]
As shown in FIG. 1, a pressure introducing portion 1 a protruding in a columnar 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 introduction part 1 a, an introduction path 1 b that is a path for introducing the measurement target pressure into the sensor element part 4 is formed so as to communicate the measurement pressure chamber 3 and the outside of the case 1.
[0014]
An O-ring 17 made of rubber or the like and a holding member (spacer) 18 for holding the O-ring 17 in the introduction path 1b are provided on the inner wall of the introduction path 1b. The pressure introducing portion 1a can be connected to the fuel tank itself or a mating member such as a hose or pipe extending from the fuel tank so as to communicate with the inside of the fuel tank, and the O-ring 17 is connected to the connecting portion. Is to prevent leakage of pressure transmitted from the mating member to the introduction path 1b.
[0015]
As shown in FIG. 3, the sensor element unit 4 includes a pressure sensitive element 4a made of silicon or the like, and a glass base 4b that supports and fixes the pressure sensitive element 4a. The pressure sensitive element 4a has a diaphragm formed on a substrate such as silicon, for example, and is joined to a glass pedestal 4b having a thermal expansion coefficient approximate to that of the pressure sensitive element 4a.
[0016]
The glass pedestal 4b has a through hole so that the pressure-sensitive element 4a detects the differential pressure between the atmospheric pressure (environmental pressure) introduced from the reference pressure chamber 2 and the measured pressure introduced from the measurement pressure chamber 3. It has become.
[0017]
The sensor element portion 4 is fixed to the case 1 via a hollow stem 5 having a through hole. The stem 5 employs 42-alloy (Fe: Ni = 58: 42), which is a material whose thermal expansion coefficient is close to that of the glass pedestal 4b, and the sensor element portion 4 and the stem 5 are bonded by a thermosetting resin or the like. It is fixed with an agent.
[0018]
The stem 5 and the case 1 are also fixed with an adhesive such as a thermosetting resin. By fixing the sensor element unit 4 and the stem 5 to the case 1, the measurement pressure introduced from the measurement pressure chamber 3 can be transmitted to the back surface of the pressure sensitive element 4a (surface on the glass pedestal 4b joint side). Become.
[0019]
In addition, the concave portion of the case 1 is filled with an adhesive 6 such as a thermosetting resin in order to further improve the airtightness of the fixing portion of the sensor element portion 4 and the stem 5 and the fixing portion of the stem 5 and the case 1. Furthermore, in order to improve the moisture resistance of the sensor element unit 4, the silicon gel 7 is filled. 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 hermetically fixed by an adhesive 9.
[0020]
Further, an atmospheric pressure introduction port (introduction port in the present invention) 10 for introducing atmospheric pressure (environmental pressure) is formed on the surface of one end side of the case 1 so as to open to the outside of the case 1. A porous sheet-like water-repellent filter (filter part in the present invention) 12 made of resin or the like is attached and fixed in the vicinity of the atmospheric pressure introduction port 10 outside the atmospheric pressure introduction port 10.
[0021]
An atmospheric pressure introduction passage 11 extending from the atmospheric pressure introduction port 10 to the reference pressure chamber 2 side is formed in the case 1. The atmospheric pressure introduction passage 11 and the reference pressure chamber 2 include the lid 8 and the case 1. It communicates with the gap. Thus, the reference pressure chamber 2 is opened to the atmosphere via the atmospheric pressure introduction port 10 and the atmospheric pressure introduction passage 11.
[0022]
As shown in FIGS. 4 and 5, the atmospheric pressure inlet 10 is constituted by an aggregate of a plurality of (three in the illustrated example) openings 21 partitioned by a frame 20. Here, of the atmospheric pressure introduction passage 11, a passage extending from the atmospheric pressure introduction port 10 to the reference pressure chamber 2 side (the left-right direction in FIG. 4B) is connected to the first passage 11 a and the first passage 11 a. A passage extending on the lid 8 side (vertical direction in FIG. 4B) is defined 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 is joined to the second passage 11b. It can be set as the structure made to.
[0023]
The water repellent filter 12 is a well-known filter obtained by subjecting a fluorine resin (polytetrafluoroethylene (PTFE) or the like) 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 (rectangular shape in this example) corresponding to the outer peripheral wall shape of the atmospheric pressure inlet 10. The filter fixing member 13 may be made of any material, but in this example, is the same material as the case 1.
[0024]
The water-repellent filter 12 is assembled, for example, by placing the water-repellent filter 12 on the case 1 so as to cover the atmospheric pressure introduction port 10 and connecting the water-repellent filter 12 and the outer wall of the atmospheric pressure introduction port 10 by the filter fixing member 13. The fixing member 13 is adhered to the case 1 with an adhesive 14 made of an epoxy resin or the like so that the filter fixing member 13 cannot be removed by being press-fitted and fixed so as to be sandwiched. In this way, the water repellent filter 12 and the case 1 are sealed to allow passage of dust and water into the reference pressure chamber 2 while allowing air flow.
[0025]
As shown in FIGS. 4B and 5, the frame 20 that defines the plurality of openings 21 is formed with a protrusion 22 that protrudes to the outside of the case 1, and the water repellent filter 12. The filter surface is disposed in contact with the tip of the protrusion 22. As a result, the filter surface has a convex shape toward the outside of the case 1.
[0026]
Further, as shown by hatching (not a cross section) in FIG. 5, the pattern of the protrusion 22 is not formed on a part of the opening edge of each opening 21. In the formation portion, a gap portion 23 is formed between the frame 20 and the filter surface. The atmospheric pressure can be introduced into each opening 21 from the gap 23 through the filter surface of the water repellent filter 12.
[0027]
The output terminal for detecting signal output in the pressure sensitive element 4a fixed to the case 1 via the stem 5 is connected to the terminal 15 via the bonding wire 16, and the signal detected by the pressure sensitive element 4a is detected. Can be taken out to the outside (for example, an ECU of an automobile).
[0028]
Next, a method for manufacturing the pressure sensor 100 will be briefly described. First, the case 1 is produced by molding a resin such as PBT or PPS. At this time, the terminal 15 is simultaneously insert-molded. Further, the water repellent filter 12 is fixed to the manufactured case 1 by the above assembling method. Next, the O-ring 17 and the holding member 18 are assembled to the pressure introducing portion 1 a of the case 1.
[0029]
Next, the pressure-sensitive element 4a is bonded to the glass pedestal 4b to form the sensor element unit 4, the glass pedestal 4b of the sensor element unit 4 is bonded to the stem 5, and the stem 5 is attached to the recess of the case 1 Glue. As a result, the reference pressure chamber 2 and the measurement pressure chamber 3 are partitioned in the recess of the case 1. Next, the output terminal of the pressure-sensitive element 4 a of the sensor element unit 4 and the terminal 15 are wire-bonded and connected by a wire 16.
[0030]
Next, the adhesive 6 is injected and filled into the reference pressure chamber 2 side of the recess of the case 1 and cured by heat treatment or the like. Next, the silicone gel 7 is injected, filled and cured 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.
[0031]
The pressure sensor 100 is connected to the counterpart member so as to seal the pressure introducing portion 1a via the O-ring 17 and is in a use state. And the measurement pressure from a to-be-detected body (fuel tank) is introduce | transduced into the measurement pressure chamber 3 from the introduction path 1b, and is transmitted to the back surface of the pressure sensitive element 4a from the hollow part of the stem 5, and the through-hole of the glass base 4b. . The measured 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 as described above, and is externally connected via the bonding wire 16 and the terminal 15. It is taken out.
[0032]
By the way, according to the present embodiment, the atmospheric pressure inlet 10 to which the water repellent filter (filter part) 12 is attached is constituted by an assembly of a plurality of openings 21 partitioned by the frame 20. Compared to the case where the atmospheric pressure inlet 10 is a single opening as in the prior art, the presence of the frame 20 increases the area in contact with moisture in the atmosphere flowing therethrough, and even a slight amount of moisture causes condensation. Promoted. As a result, moisture is collected and stopped in the water-repellent filter 12, and moisture is less likely to enter the inside than the filter 12, so that the moisture removal performance in the filter portion can be improved. Therefore, it becomes easier for water to fall, and the removal of water can be further promoted.
[0033]
For example, in the pressure sensor 100 attached to the fuel tank, the water is intense due to the water that is rolled up from the wheels when the automobile is running in the rain. Even in such an environment, according to the present pressure sensor 100, the water repellent filter 12 is sufficiently removed of water, so that the function of the sensor is not impaired.
[0034]
Furthermore, in this embodiment, since the gap portion 23 into which 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 clogged by any chance. However, it is preferable that the atmospheric pressure can be led to the sensor element portion 4 from the gap portion 23 instead.
[0035]
For example, as shown in FIG. 6, if a foreign matter K1 such as mud adheres to the filter surface of the water repellent filter 21 so as to cover the opening 20, the filter surface at the attachment portion is clogged. Here, if there is no gap 23, the opening 20 covered with the foreign material K1 is closed. In this regard, as shown by hatched hatching in FIG. 6, if there is a gap 23, communication between the outside and the opening 21 is ensured, so that foreign matter adheres to the entire filter surface and is not blocked. The pressure sensor 100 can prevent the atmospheric pressure introduction path from being blocked.
[0036]
(Other embodiments)
In the above embodiment, the present invention is applied to the relative pressure sensor that detects the differential pressure between the atmospheric pressure and the measurement target pressure. However, the atmospheric pressure (environmental pressure) is introduced into the sensor element unit, and the atmospheric pressure is absolute. It can also be applied to pressure sensors that measure pressure.
[0037]
In short, the present invention is formed on the surface of the case in the pressure sensor in which the environmental pressure outside the case is introduced to the sensor element portion arranged in the case through the filter portion provided in the case. Since the main part is that the inlet to which the filter part is attached is constituted by an assembly of a plurality of openings partitioned by a frame, other parts can be appropriately changed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an overall configuration of a pressure sensor according to an embodiment of the present invention.
FIG. 2 is a view taken in the direction of arrow A in FIG.
3 is an enlarged view of a sensor element portion in FIG. 1. FIG.
4 is a diagram showing a detailed configuration of a filter unit in the pressure sensor in FIG. 1. FIG.
FIG. 5 is a detailed configuration diagram of an atmospheric pressure introduction port of the pressure sensor shown in FIG. 1;
FIG. 6 is an explanatory diagram showing the effect of the gap.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Case, 4 ... Sensor element part, 10 ... Atmospheric pressure inlet, 12 ... Water-repellent filter, 20 ... Frame, 21 ... Opening part, 22 ... Projection part, 23 ... Gap part.

Claims (1)

The environmental pressure outside the case is introduced to the sensor element portion (4) for pressure detection disposed in the case (1) through the filter portion (12) provided in the case. In the pressure sensor,
An inlet (10) for introducing the environmental pressure that opens to the outside is formed on the surface of the case,
The filter part is attached to the inlet,
The introduction port is constituted by an aggregate of a plurality of openings (21) partitioned by a frame (20) ,
The frame (20) is formed with a protrusion (22) that protrudes to the outside of the case (1), and the filter surface of the filter part (12) is disposed in contact with the tip of the protrusion. And
A gap sensor (23) capable of introducing environmental pressure is formed between the frame and the filter surface .

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