JP3627766B2 - Pressure sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a reference pressure chamber into which an atmospheric pressure is introduced and a measurement pressure introduction chamber into which a measurement target pressure is introduced in a case, and the pressure difference between the two chambers is detected by a pressure sensing unit. It relates to sensors.
[0002]
[Problems to be solved by the invention]
This type of pressure sensor is used, for example, to detect a pressure in a pipe connected from a fuel tank to a canister in an automobile. This pressure sensor is provided with a reference pressure chamber into which atmospheric pressure is introduced, a measurement pressure introduction chamber into which a pressure to be measured is introduced, in a synthetic resin case having a thin box shape. The pressure sensitive element is provided at the boundary portion that divides the area. The case is formed with an atmospheric pressure introducing hole for communicating the reference pressure chamber with the outside (atmosphere).
[0003]
Then, on the surface of the thin portion of the pressure sensitive element, for example, a circuit in which four resistors are assembled in a bridge is formed. Thus, the electrical resistance changes due to the stress accompanying the pressure difference between the upper and lower sides of the thin portion, and the measurement target pressure (relative pressure) is detected by taking out the output signal from the circuit. In addition, a filter for preventing droplets and dust from entering the reference pressure chamber is also provided so as to close the atmospheric pressure introduction hole.
[0004]
However, the above conventional ones have the following problems. That is, when the pressure sensor is used in an environment where there is a risk of water splashing or condensation, the water attached to the outer surface of the case may become a water film and block the atmospheric pressure introduction hole. The pressure chamber might not be at the correct atmospheric pressure. In addition, foreign matter such as water, oil, and dust may enter the case (reference pressure chamber) from the atmospheric pressure introduction hole, which may cause adverse effects such as deterioration of parts.
[0005]
In this case, if a filter is provided in the atmospheric pressure introduction hole as described above, foreign matter will not enter the case, but foreign matter captured by the filter will clog the filter and introduce atmospheric pressure. The negative effect of closing the hole will occur. In particular, in the case of a pressure sensor used for a vehicle, when the vehicle travels on a rainy day, the case may get wet by splashing and the atmospheric pressure introduction hole may be blocked by mud or water. It becomes easy to happen.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to effectively prevent the atmospheric pressure introduction hole that connects the reference pressure chamber and the outside of the case from being blocked by a water film or the like. To provide a sensor.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, the pressure sensor includes a reference pressure chamber into which the atmospheric pressure is introduced and a measurement pressure introduction chamber into which the measurement target pressure is introduced, and detects a pressure difference between the two chambers. Oite those comprising a pressure sensing section, wherein the case, and the atmospheric pressure introducing hole communicating with said reference pressure chamber and the outside of the case, provided in an opening portion of the case exterior surface portion that atmospheric pressure introducing hole is opened, the and a spout projecting from the casing outer surface, the spout, the co the outer wall surface is reduced in diameter toward the distal end inner wall of the atmospheric pressure introduction hole toward the distal end side at the tip contraction It is provided in a form having a wall thickness by diameter , and the projecting port part has an inner peripheral end surface in which the projecting port part is cut in the thickness direction, and a linear projecting tip extending in a circular shape And has a feature.
[0008]
In this case, a water repellent filter that allows passage of air and prevents passage of droplets and dust may be provided at a position deeper than the protruding opening of the atmospheric pressure introduction hole. invention). Further, it is more effective if the atmospheric pressure introduction hole is formed downward (invention of claim 3). Furthermore, it can also be set as the structure which diameter-reduces the outer wall of the said protrusion opening part toward the front end side (invention of Claim 4).
The pressure sensor according to claim 5 of the present invention includes, in the case, a reference pressure chamber into which atmospheric pressure is introduced and a measurement pressure introduction chamber into which measurement target pressure is introduced, and a pressure difference between the two chambers. The case is provided with a pressure-sensitive portion for detection, and the case is provided at an opening portion of an atmospheric pressure introduction hole for communicating the reference pressure chamber and the outside of the case, and an outer surface portion of the case where the atmospheric pressure introduction hole opens. In addition, it has a feature in that it has a projecting opening portion that protrudes from the outer surface portion of the case and whose inner wall surface and outer wall surface are reduced in diameter downward.
Also in this case, a water-repellent filter that allows passage of air and prevents passage of droplets and dust may be provided at a position behind the projecting opening of the atmospheric pressure introduction hole. Invention). Further, a linear projecting tip can be provided at the projecting opening (invention of claim 7). Furthermore, the projecting tip of the projecting port portion can be formed in a form in which the projecting port portion is cut in the thickness direction (invention of claim 8).
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a pressure sensor used in an automobile will be described with reference to FIGS. FIG. 1 shows an overall configuration of a pressure sensor 1 according to the present embodiment. Here, a case 2 is configured by covering a synthetic resin case main portion 3 with a synthetic resin lid 4. In this case, the lid 4 is airtightly fixed to the case main portion 3 by the adhesive 5.
[0010]
In the figure of the case main part 3, the right end part is formed by insert molding a plurality of terminals 6 (only one is shown) and a substantially rectangular tube-shaped connector housing part 3a. It is designed to function as a connector. The pressure sensor 1 is connected to the outside through this connector. At this time, an air escape hole 6a is formed in the terminal 6 in order to release pressure generated when connecting to a female connector (not shown) upward from the lower surface side of the terminal 6, and in the case 2, A sub chamber 7 communicating with the air escape hole 6a is provided.
[0011]
In the center of FIG. 2, the reference pressure chamber 8 into which the atmospheric pressure is introduced, the measurement pressure introduction chamber 9 into which the pressure to be measured (for example, the pressure in the pipe connected from the fuel tank to the canister) is introduced, and A pressure sensitive unit 10 for detecting a pressure difference between the two chambers 8 and 9 is provided. Among these, the pressure-sensitive part 10 is provided in the recessed part 3b formed in the case main part 3 as described later. The upper part of the pressure-sensitive part 10 (the space part between the lid 4) serves as a reference pressure chamber 8.
[0012]
On the other hand, a tubular pressure port 11 is integrally formed extending downward from the lower surface portion of the central portion of the case main portion 3, and the hollow portion of the pressure port 11 becomes one step larger in diameter in the case main portion 3. The measurement pressure introduction chamber 9 is formed by these hollow portions so as to be continuous with the bottom of the recess 3b. The pressure port 11 is connected to a pressure measurement target (a pipe connected from the fuel tank to the canister) via a pressure guiding pipe (not shown).
[0013]
Here, the pressure sensitive unit 10 will be described. As shown also in FIG. 4, the pressure sensitive element 12 formed of, for example, single crystal silicon has a thin pressure responsive portion 12a at the center, and although not shown in the figure, on the surface of the pressure responsive portion 12a. For example, a circuit in which four resistors are assembled in a bridge is formed. Further, a protective film 13 made of, eg, SiN is formed on the entire surface of the pressure sensitive element 12 so as to improve moisture resistance. Note that the pressure responsive portion 12a is formed thin and with high precision by an electric stop etching technique in which etching stops at the epitaxial layer.
[0014]
The pressure-sensitive element 12 is airtightly bonded by anodic bonding to the upper surface of a glass pedestal 14 combined with a thermal expansion coefficient. Further, the pedestal 14 is mounted in the recess 3 b in a state where it is placed on the stem 15. The stem 15 is made of, for example, a synthetic resin having a material whose thermal expansion coefficient is similar to that of the base 14. Further, the space between the pedestal 14 and the stem 15 and the space between the stem 15 and the case main portion 3 (the bottom surface of the recess 3b) are both airtightly bonded by an adhesive. In this case, as the adhesive, Young A fluorine-based material having a low rate and high chemical resistance is used.
[0015]
Thus, the upper surface side of the pressure sensitive element 12 (pressure responsive portion 12a) faces the reference pressure chamber 8, and the lower surface side of the pressure sensitive element 12 is inserted through the through hole 14a of the pedestal 14 and the through hole 15a of the stem 15. A pressure difference (relative pressure) between the pressure to be measured and the atmospheric pressure is detected by the pressure sensing element 12 in communication with the measurement pressure introduction chamber 9. An electrode (circuit) on the pressure sensitive element 12 is connected to the terminal 6 via a bonding wire 16 so that a detection signal is taken out.
[0016]
The space in the recess 3b is filled with, for example, a fluorine-based adhesive 17 so as to embed the lower half of the stem 15 and the pedestal 14 in order to improve hermeticity. Further, in order to improve the moisture resistance, the upper surface side of the adhesive 17 is filled with a silicon gel 18 so as to cover the whole including the pressure sensitive element 12 and the bonding wire 16. At the time of application of the adhesive, a primer for improving the adhesive strength is applied to the adhesive surface of the stem 15 and the recess 3b, but only the lower surface portion of the pedestal 14 is applied. In order to prevent the primer from rising in the through hole 14a and adversely affecting the pressure sensitive element 12, the primer is not applied.
[0017]
Now, an atmospheric pressure introduction hole 19 for communicating the reference pressure chamber 8 with the outside (atmosphere) of the case 2 is provided in the left end portion of the case 2 (case main portion 3). In this case, as shown in FIGS. 2 and 3, the left end portion of the case main portion 3 is configured to be thick so that the inner surface (upper surface) protrudes to a position close to the lid 4, and the atmospheric pressure introduction hole 19 is formed so as to penetrate the thick portion in the vertical direction.
[0018]
The atmospheric pressure introduction hole 19 is formed so as to have a circular cross section, and the upper end portion thereof is formed to be one step larger in diameter, and the water repellent filter 20 is provided in the larger diameter portion. . The water-repellent filter 20 is airtight by, for example, welding the outer peripheral surface of the holder 22 to the inner peripheral surface of the atmospheric pressure introduction hole 19 while being sandwiched between upper and lower holders 21 and 22 each having a substantially ring shape. The fitting is fixed.
[0019]
In this case, the water repellent filter 20 is made of a known porous filter, and has an outer diameter (for example, φ2.4 mm) and a hole diameter (for example, φ1.0 μm) that can ensure a predetermined air flow rate (for example, 0.37 cc / sec or more). And water repellent treatment for preventing liquid adhesion. Thus, the water-repellent filter 20 is located behind a projecting opening 23 described later in the atmospheric pressure introduction hole 19 so as to allow passage of air and prevent passage of droplets and dust. ing.
[0020]
The atmospheric pressure introduction hole 19 is opened at the lower surface of the case 2 (case main portion 3), and the opening opening on the lower surface of the case main portion 3 projects a small amount downward. The part 23 is provided integrally. As shown in FIGS. 2 and 3, the protruding port portion 23 is formed in a tapered shape whose outer wall surface is reduced in diameter downward, and the inner wall surface of the atmospheric pressure introduction hole 19 is a lower end portion. In FIG. 2, the taper is reduced in diameter toward the lower side, so that it has a certain thickness. At this time, the inner peripheral edge surface (opening) 23a of the spout 23 is a form as cut into the thickness direction, which at the projecting distal end 23b of the spout 23, substantially line extending in a circular shape It is made into a shape.
[0021]
Next, the operation of the above configuration will be described with reference to FIG. The pressure sensor 1 configured as described above is located at the lower part of the vehicle (automobile) (near the fuel tank) and is attached with the atmospheric pressure introduction hole 19 facing downward as shown in the figure. At this time, the inside of the reference pressure chamber 8 is communicated with the outside (atmosphere) through the water repellent filter 20 through the atmospheric pressure introduction hole 19 and the atmospheric pressure is introduced. On the other hand, the measurement pressure introduction chamber 9 communicates with a pipe connected from the fuel tank to the canister via the pressure port 11, and the pressure in the pipe is introduced as a measurement target pressure.
[0022]
At this time, the atmospheric pressure (reference pressure) acts on the pressure sensing element 12 of the pressure sensing unit 10 on the upper surface side of the pressure responsive portion 12a, while the measurement target pressure acts on the lower surface side. As a result, the electrical resistance of the resistor formed on the pressure responsive portion 12a changes due to the stress associated with the pressure difference between the upper and lower sides of the pressure responsive portion 12a, and the output signal is taken out from the circuit, so that the measurement target pressure (relative Pressure) is detected.
[0023]
Since the reference pressure chamber 8 is open to the atmosphere through the atmospheric pressure introduction hole 19, foreign matter such as dust and droplets may enter the reference pressure chamber 8 (in the case 2). If there is such intrusion, there is a risk of adverse effects such as deterioration of components (corrosion, disconnection, etc.). In addition, since the opening of the atmospheric pressure introduction hole 19 (opening 23a of the projecting opening 23) is small in diameter, if water is splashed or condensation is formed, a water film may be formed and the opening may be blocked. If such a water film is generated, the inside of the reference pressure chamber 8 does not become the atmospheric pressure correctly, and there is a risk that the characteristics will fluctuate and the detection accuracy will deteriorate.
[0024]
In particular, in the present embodiment, the pressure sensor 1 is incorporated in an automobile and used outdoors, so that it is used in a harsh environment where it is susceptible to dust, muddy water, and the like. Incidentally, FIG. 5 shows the relationship between the amount of water applied to the pressure sensor 1 and the vehicle speed when running on a water channel at a water depth of 5 cm, according to experiments conducted by the present inventors. In addition, the pressure sensor 1 is largely wet even during the steam car wash.
[0025]
However, in the present embodiment, since the projecting port portion 23 projecting downward is provided at the opening portion of the atmospheric pressure introduction hole 19 communicating with the reference pressure chamber 8, the projecting port portion 23 becomes a wall, for example, from an oblique direction. Dust and droplets are prevented from entering the opening, and the dust and droplets are less likely to enter the atmospheric pressure introduction hole 19 as compared to the case where the opening is simply formed on a flat surface. In addition, since the projecting port portion 23 has a tapered shape with a reduced diameter downward, the opening portion 23a becomes smaller in diameter, and foreign matter is more difficult to enter.
[0026]
The projecting distal end 23b of the spout 23, since there is a linear shape extending in a circular shape, as compared with the case periphery of the opening is wide flat surface, so to speak drainage is improved, condensation is deposited Even so, it is possible to prevent the formation of a water film that closes the opening 23a.
[0027]
In this embodiment, since the water repellent filter 20 is provided in the atmospheric pressure introduction hole 19, for example, air A containing dust or droplets enters the atmospheric pressure introduction hole 19 as shown in FIG. Even so, the water-repellent filter 20 prevents the passage of these dusts and droplets, and only clean air B is introduced into the reference pressure chamber 8. In this case, since the water repellent filter 20 itself is provided at the back of the atmospheric pressure introduction hole 19, it is difficult for dust and droplets to reach the water repellent filter 20. In addition, since the foreign matter is captured on the lower surface side of the water-repellent filter 20, the foreign matter does not accumulate on the filter surface and clog the water-repellent filter 20. In addition, in the research by the present inventors, it has been found that if the position of the water repellent filter 20 is 8 mm or more away from the opening 23a, the probability that the water repellent filter 20 is wetted can be extremely reduced.
[0028]
Further, in the present embodiment, since the atmospheric pressure introduction hole 19 is provided downward, as shown in FIG. 3, dust C and droplets D that have entered the atmospheric pressure introduction hole 19 are caused to flow into the inner wall of the atmospheric pressure introduction hole 19. The foreign matter flows down and is quickly discharged from the opening 23a.
[0029]
Therefore, according to the present embodiment, by providing the projecting port portion 23 in the opening portion of the atmospheric pressure introduction hole 19, it is possible to effectively prevent foreign matter from entering the atmospheric pressure introduction hole 19, and Unlike the conventional case in which a water film is likely to be formed in the opening, it is possible to effectively prevent the atmospheric pressure introduction hole 19 that connects the reference pressure chamber 8 and the outside of the case 2 from being blocked by a water film or the like. It can be done.
[0030]
In particular, in the present embodiment, the water-repellent filter 20 is provided in the depth of the atmospheric pressure introduction hole 19 so that the entry of foreign matter such as dust and droplets into the reference pressure chamber 8 can be surely prevented and the water-repellent property can be prevented. The filter 20 is not clogged, and by providing the atmospheric pressure introduction hole 19 downward, foreign matter that has entered the atmospheric pressure introduction hole 19 can be quickly discharged. By forming the outer wall of the taper 23 into a tapered shape, it is possible to enjoy the merit that foreign matter can be prevented from entering even more effectively.
[0031]
FIG. 6 shows a reference example . This reference example is different from the above embodiment in the structure of the projecting port portion 32 provided at the opening portion of the atmospheric pressure introduction hole 31, and here, a thin cylinder projecting the projecting port portion 32 downward. It is formed in a shape. Therefore, the projecting tip 32a of the projecting port 32 is also non-planar (in this reference example, it is substantially linear extending in the same manner as the embodiment shown in FIGS. 2 and 3). Further, the atmospheric pressure introduction hole 31 is formed in a shape in which the lower portion is reduced in a taper shape. Even in such a configuration, the same effect as in the above embodiment can be obtained.
[0032]
FIG. 7 shows another different reference example. Here, the projecting port portion 33 is formed in a long shape, and the base end portion of a pipe (hose) 34 can be connected to the projecting port portion 33. It is. According to this, the front-end | tip part of the piping 34 can be arrange | positioned in the clean air chamber as much as possible. In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and can be applied to, for example, a pressure sensor for uses other than those for vehicles. Further, the pressure sensing unit 10 and the measurement pressure introduction chamber 9 are applicable. Various modifications can be made to the configuration of the portion, and the configuration can be appropriately changed and implemented without departing from the spirit of the invention.
[0033]
【The invention's effect】
As is apparent from the above description, according to the pressure sensor of claim 1 of the present invention, the case is provided at the opening portion of the case outer surface portion where the atmospheric pressure introduction hole for communicating the reference pressure chamber and the outside of the case is opened. Since the projecting port portion that protrudes from the outer surface portion and the protruding tip is linear is provided, the atmospheric pressure introduction hole can be effectively prevented from being blocked by a water film or the like.
[0034]
In this case, if a water repellent filter is provided at a position behind the projecting opening of the atmospheric pressure introduction hole (a pressure sensor according to claim 2), foreign matter such as dust and droplets can enter the reference pressure chamber. While being able to prevent reliably, the water-repellent filter can be prevented from being wet as much as possible. Further, if the atmospheric pressure introduction hole is formed downward (pressure sensor of claim 3), the foreign matter is less likely to enter the atmospheric pressure introduction hole, and the entered foreign matter can be quickly discharged. Furthermore, if the diameter of the outer wall of the projecting opening is reduced toward the distal end (pressure sensor according to claim 4), the entry of foreign matter can be prevented more effectively.
According to the pressure sensor of claim 5 of the present invention, the opening portion of the case outer surface portion where the atmospheric pressure introduction hole for communicating the reference pressure chamber and the outside of the case opens, projects from the case outer surface portion, and the inner wall surface and the outer wall surface. Is provided with a projecting opening that is reduced in diameter toward the lower side, so that the diameter of the opening of the atmospheric pressure introduction hole can be made smaller to prevent the intrusion of liquid droplets and dust.
In this case, if a water-repellent filter is provided at a position behind the projecting opening of the atmospheric pressure introduction hole (pressure sensor of claim 6), foreign matter such as dust and droplets can enter the reference pressure chamber. While being able to prevent reliably, the water-repellent filter can be prevented from being wet as much as possible. Further, if a linear projecting tip is provided at the projecting opening (pressure sensor according to claim 7), water drainage is improved, and it is possible to prevent the formation of a water film. Furthermore, if the projecting tip of the projecting port is formed in a form in which the projecting port is cut in the thickness direction (pressure sensor of claim 8), the projecting tip can be made linear.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention, and is an overall longitudinal side view. FIG. 2 is a longitudinal side view of a main part for explaining the operation of a water repellent filter. Fig. 4 is an enlarged vertical side view of the pressure-sensitive element. Fig. 5 is a diagram showing the relationship between the vehicle speed and the amount of water. Fig. 6 is a protruding port portion showing another embodiment of the present invention. Fig. 7 is a vertical side view of the main part showing another different embodiment.
In the drawings, 1 is a pressure sensor, 2 is a case, 3 is a case main part, 4 is a lid, 8 is a reference pressure chamber, 9 is a measurement pressure introducing chamber, 10 is a pressure sensing unit, 11 is a pressure port, and 12 is pressure sensitive. Elements 19 and 31 are atmospheric pressure introduction holes, 20 is a water repellent filter, 23, 32 and 33 are projecting openings, and 23 b and 32 a are projecting tips.

Claims (3)

In the case, which includes a reference pressure chamber into which atmospheric pressure is introduced and a measurement pressure introduction chamber into which a measurement target pressure is introduced, and a pressure sensing unit that detects a pressure difference between the two chambers,
The case has an atmospheric pressure introduction hole for communicating the reference pressure chamber with the outside of the case,
Provided in the opening portion of the case outer surface portion where the atmospheric pressure introduction hole opens, and includes a projecting mouth portion protruding from the case outer surface portion,
The spout, that the outer wall surface is an inner wall surface of said atmospheric pressure introducing hole co the diameter decreases toward the distal end is reduced in diameter toward the distal end side at the tip, provided in a form having a wall thickness And
Furthermore, the spout, the pressure sensor and having an inner peripheral surface of the form as the spout is cut in the thickness direction, and a linear protruding end extending circular. The pressure sensor according to claim 1, wherein a water repellent filter that allows passage of air and prevents passage of liquid droplets and dust is provided at a position deeper than the protruding opening of the atmospheric pressure introduction hole. . The pressure sensor according to claim 1, wherein the atmospheric pressure introduction hole is formed downward .

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