JP2001272296A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent as much as possible the effect of a contaminant contained in a pressure medium, on a diaphragm part of a pressure sensor chip with a relatively simple configuration. SOLUTION: A reference pressure chamber 3 and a measuring pressure chamber 4 communicating with each other with a through hole 8b while partitioned with a partition wall 8 are provided in a case 2. A pressure sensor chip 5 is fitted inside a housing recessed part 8a provided on the measuring pressure chamber 4 side of the partition wall 8, with a rubber film 13 held on its rear surface side. The rubber film 13 is so configured that a thick-wall fixing part 13b is integrally provided on the outer peripheral side of a thin-wall pressure receiving part 13a corresponding to the through hole 8b. The front surface side of the pressure sensor chip 5 is covered with a protective material such as silicon gel. The pressure in the reference pressure chamber 3 is applied to the rear surface side of a diaphragm part 14a of the pressure sensor chip 5 through the rubber film 13.

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 detecting a differential pressure (relative pressure) between a reference pressure chamber and a measurement pressure chamber using a pressure sensor chip having a diaphragm.

[0002]

For example, a pressure sensor (differential pressure sensor) used for an automobile has a reference pressure chamber in which a reference pressure is introduced and a measurement pressure chamber in which a measurement pressure is introduced. And a pressure sensor chip for detecting a pressure difference therebetween is provided. The pressure sensor chip is formed by forming a thin diaphragm portion on a silicon substrate and forming a pressure detection circuit, and is mounted in a case while being supported by a glass pedestal. The reference pressure and the measured pressure are applied to both surfaces of the diaphragm, respectively, to detect the differential pressure therebetween.

By the way, in such a differential pressure sensor, for example, dust, soot, water or the like from the outside of a vehicle enters a reference pressure chamber into which the atmosphere is introduced. May contain contaminants such as dust and impurities. When contaminants are contained in the pressure medium in this way,
As a result, the pressure sensor chip may be contaminated, and the contaminant may accumulate on the diaphragm portion, which may have a negative effect such as a change in the characteristics of the pressure sensor chip.

In order to solve such a problem, it is conceivable to cover both front and back surfaces of the pressure sensor chip (diaphragm portion) with a protective material such as silicon gel. However,
In such a configuration, the operation of applying and curing the silicon gel on the pressure sensor chip is required on both sides, respectively, which complicates the configuration and causes a problem of increasing the number of assembling steps.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent contamination of a diaphragm of a pressure sensor chip due to contaminants such as dust and impurities contained in a pressure medium as much as possible. Another object of the present invention is to provide a pressure sensor having a relatively simple structure.

[0006]

In order to achieve the above object, a pressure sensor according to the present invention partitions a pressure sensor chip between a back side of a diaphragm portion of a pressure sensor chip and a pressure chamber, and responds to a change in pressure in the pressure chamber. A protective rubber film which is elastically deformed is provided (the invention of claim 1). According to this, the pressure in the pressure chamber is applied to the back surface of the diaphragm portion of the pressure sensor chip via the rubber film, but even if there is a pressure fluctuation in the pressure chamber, the rubber film is affected by the pressure fluctuation. Accordingly, the pressure in the pressure chamber can be transmitted to the diaphragm with almost no loss because it is easily elastically deformed (elongated and deformed).

[0007] Even if the pressure medium introduced into the pressure chamber contains contaminants such as dust and impurities, the protective rubber film that partitions between the back side of the pressure sensor chip and the pressure chamber provides The contaminant is prevented from reaching the pressure sensor chip, and can be prevented from adhering to the diaphragm. In this case, since the rubber film can be easily assembled by, for example, bonding or the like, the configuration is simpler and the assembling operation can be easily performed as compared with the rubber film covered with a protective material such as silicon gel.

Therefore, according to the first aspect of the present invention, it is possible to achieve a relatively simple configuration while minimizing adverse effects such as contamination of the diaphragm of the pressure sensor chip due to contaminants contained in the pressure medium. The excellent effect that it can be obtained can be obtained. The material of the rubber film can be selected from fluorine rubber, acrylic rubber, NBR, silicon rubber, fluorosilicone rubber, and the like, depending on the use environment such as the type and temperature of the pressure medium. Of these, the former three also have excellent adhesiveness.

At this time, the rubber film is constituted by integrally providing a fixing portion for mounting outside the pressure receiving portion receiving the pressure of the pressure chamber, and the pressure receiving portion is made thinner than the fixing portion. (Invention of claim 2). According to this, the pressure receiving portion can be thinned and easily elastically deformed while securing the mounting strength of the rubber film by the fixing portion, and the pressure fluctuation can be transmitted to the diaphragm portion without loss.

The pressure sensor according to the present invention is desirably used for a low pressure whose pressure detected by the pressure sensor chip is 0.2 MPa or less (the invention of claim 3).
Thus, the pressure in the pressure chamber can be sufficiently transmitted to the diaphragm of the pressure sensor chip via the rubber film, and the rubber film does not require a large mounting strength or the like.
Adhesion or the like can be employed for attaching the rubber film.

As a more specific structure, of the partition wall having a communication hole for partitioning the reference pressure chamber and the measurement pressure chamber and communicating the two chambers, the communication hole portion on the side of the pressure chamber on the side of the pressure chamber where the pressure is high is provided. The pressure sensor chip can be attached with the rubber film sandwiched on the back side thereof (the invention of claim 4). According to this, when the pressure sensor chip is mounted on the partition wall, a simple configuration in which a rubber film is interposed between them is sufficient, so that the assemblability can be improved. Further, during use, pressure acts in the direction of pressing the rubber film, so that the rubber film can be prevented from coming off.

On the front side of the pressure sensor chip, there are circumstances in which a pressure detection circuit and its electrodes are provided, and bonding wires for electrical connection are provided. It is desirable to cover with a protective material such as gel.
Invention). Thus, the surface side of the pressure sensor chip can be protected from contaminants such as dust and impurities in the pressure medium in an appropriate form.

Further, the pressure sensor of the present invention is constructed not only as a sensor for detecting a differential pressure (relative pressure) but also for detecting an absolute pressure of a measured pressure by sealing a reference pressure chamber in a vacuum state. (The invention of claim 6), whereby the use can be expanded. Even in the case of absolute pressure, when the pressure is 0.2 MPa (0.2 N / mm 2), the force acting on the rubber film is 1. if the diameter of the pressure receiving portion of the rubber film is 3 mm (the area is about 7 mm 2). 4N (140 gf), which is considered to be sufficiently usable.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a differential pressure (relative pressure) sensor for an automobile will be described below with reference to the drawings. FIG. 2 shows the entire configuration of the pressure sensor 1 according to the present embodiment, and FIG. 1 shows a main portion (a portion where the pressure sensor chip is provided) of the pressure sensor 1 upside down in FIG. It is shown enlarged. In addition, this pressure sensor 1 is configured for low pressure detection pressure of 0.2 MPa or less.

Here, as shown in FIG.
In the case 2, two pressure chambers 3 and 4, a reference pressure chamber 3 and a measurement pressure chamber 4, are provided, and a pressure sensor chip 5 is provided. The case 2 is made of plastic, and integrally has a connector housing 7 on the right side of the main body 6 in the drawing. The main body 6 has a substantially rectangular box shape with both upper and lower surfaces open, and has a partition wall 8 at an intermediate portion in the height direction to partition the inside up and down. The case 2 has three (only one is shown) extending rightward in the figure from the intermediate portion of the partition wall 8, penetrating the main body 6, and having a right end portion located in the connector housing portion 7. Are integrally provided by insert molding. As a result, a connector for electrical connection to the outside is formed on the right side of the case 2.

An upper cover 10 is provided at an opening on the upper surface of the main body 6. The upper lid 10 has a falling wall 10a around the lower surface thereof. The falling wall 10a is inserted into a groove 6a formed in the upper end surface of the main body 6, and the adhesive 11 is formed. It is airtightly attached by bonding. Thus, the reference pressure chamber 3 is provided between the partition wall 8 and the upper lid 10 in the case 2 (main body 6). At this time, a reference pressure introduction port (not shown) is provided in the upper lid 10 so that the inside of the reference pressure chamber 3 is set to a reference pressure (in this case, atmospheric pressure).

Similarly, a lower lid 12 is provided in the opening on the lower surface of the main body 6. The lower lid portion 12 has a rising wall portion 12a around the upper surface side thereof.
2a is hermetically attached by being inserted into a groove 6b formed on the lower end surface of the main body 6 and adhered by an adhesive 11. Thus, case 2 (main body 6)
The measurement pressure chamber 4 is provided between the partition wall 8 and the lower lid 12. At this time, a measurement pressure introduction port (not shown) is provided in the lower lid portion 12, so that a measurement pressure (for example, an intake pressure of an engine) is introduced into the measurement pressure chamber 4. In this embodiment, the inside of the measurement pressure chamber 4 has a higher pressure than the reference pressure chamber 3.

Further, as shown in FIG. 1, an accommodation recess 8a to which a pressure sensor chip 5 described later is attached is formed in a central portion of the partition wall 8 on the measurement pressure chamber 4 side (the upper surface side in FIG. 1). Is formed. The lower surface (the upper surface in FIG. 1) of the left end of the terminal 9 is exposed at the right end portion of the bottom surface of the accommodation recess 8a. Further, a communication hole 8b penetrating vertically and communicating the reference pressure chamber 3 and the measurement pressure chamber 4 is formed in a leftward portion of the accommodation recess 8a.

Now, as shown in FIG.
In a, a rubber film 13 for protection is provided together with the pressure sensor chip 5. The pressure sensor chip 5 includes a thin diaphragm portion 14a formed by etching the central rear surface of the single-crystal silicon substrate 14, as is well known, and a piezoresistive element (not shown) on the front surface. It is configured by forming a bridge-connected detection circuit. The single-crystal silicon substrate 14 is hermetically bonded on a glass pedestal 15. The pedestal 15 is formed with a through hole 15a communicating with the back surface of the diaphragm portion 14a.

The pressure sensor chip 5 is provided in the communication hole 8b at the bottom of the accommodation recess 8a. At this time, the back side (the bottom side of the pedestal 15).
In addition, it can be attached with the rubber film 13 interposed therebetween. The rubber film 13 is made of, for example, fluorine rubber, acrylic rubber, NBR, or the like, and integrally has a fixing portion 13b for attachment on the outer peripheral side of the pressure receiving portion 13a having a size substantially equal to the opening of the communication hole 8b. It is configured. In this case, the pressure receiving portion 13a is configured to be thinner than the fixing portion 13b. This rubber membrane 13 is
The fixing portion 13b is attached to the bottom wall portion of the accommodation recess 8a by, for example, bonding so that a coincides with the opening of the communication hole 8b.

The pressure sensor chip 5 has the lower surface side of the pedestal 15 attached to the fixing portion 13b of the rubber film 13 by, for example, bonding. The pressure sensor chip 5 (detection circuit) and the exposed portion of the terminal 9 are electrically connected by a bonding wire 16. Further, a protective material 17 such as, for example, silicone gel is potted in the accommodation recess 8a.
7, the front side of the pressure sensor chip 5, the bonding wires 16, and the exposed portions of the terminals 9 are covered.

As a result, the gap between the back surface of the diaphragm portion 14a of the pressure sensor chip 5 and the reference pressure chamber 3 is partitioned by the rubber film 13, and the pressure in the reference pressure chamber 3 is reduced by the rubber film 13 ( The pressure is applied to the back side of the diaphragm part 14a via the pressure receiving part 13a). At this time, the pressure receiving portion 13a of the rubber film 13 is easily elastically deformed according to the pressure change of the reference pressure chamber 3. On the other hand, the diaphragm portion 14a of the pressure sensor chip 5
The pressure of the measurement pressure chamber 4 is applied via a protective material 17 to the surface side of the. Pressure sensor chip 5
Outputs an electric signal corresponding to a pressure difference applied to both front and back surfaces of the diaphragm portion 14a.

Here, the procedure for assembling the pressure sensor 1 having the above configuration will be briefly described. First, Case 2 is shown in FIG.
With the reference pressure chamber 3 side facing upward, the upper lid 10 is fitted into the main body 6 of the case 2 and fixed with the adhesive 11. Next, the case 2 is turned upside down (the state shown in FIG. 1), a rubber film 13 is adhered to the bottom of the accommodation recess 8a of the partition wall 8 in a positioning state, and a pedestal 15 is previously provided on the rubber film 13. The pressure sensor chip 5 is adhered. Thereafter, electrical connection is made by the bonding wire 16, and further, the protective material 17 is filled in the housing recess 8a and cured. Finally, the pressure sensor 1 is completed by fitting the lower lid 12 into the main body 6 and fixing it with the adhesive 11.

In the pressure sensor 1 configured as described above, for example, the atmospheric pressure as the reference pressure is introduced into the reference pressure chamber 3 as described above, and the pressure is applied to the rubber film 13.
Is applied to the back surface side of the diaphragm portion 14a of the pressure sensor chip 5 through the pressure sensor. At the same time, a measurement pressure is introduced into the measurement pressure chamber 4, and the pressure is applied to the surface side of the diaphragm portion 14a via the protective material 17, whereby the differential pressure between them is detected.

At this time, the pressure sensor chip 5 (on the back side of the diaphragm portion 14a) and the reference pressure chamber 3 are separated by the rubber film 13;
Even if there is a pressure fluctuation inside, the pressure receiving portion 13a of the rubber film 13 easily elastically deforms (extends and deforms) according to the pressure fluctuation, so that the pressure in the reference pressure chamber 3 is transmitted to the diaphragm portion 14a with almost no loss. be able to. In addition, the rubber film 1
3 is a thin pressure receiving portion 13a inside the thick fixing portion 13b.
Therefore, the pressure receiving portion 13a can be thinned and easily elastically deformed while securing the mounting strength of the rubber film 13 by the fixing portion 13b, and the diaphragm portion 14a does not lose pressure fluctuation without loss. Can tell.

The pressure medium (air) introduced into the reference pressure chamber 3 may include dust, soot, water, and other dust and impurities. Contaminants such as impurities are prevented from reaching the pressure sensor chip 5, and the contaminants are
It can be prevented from adhering to and further depositing on a. On the other hand, since the front surface side of the pressure sensor chip 5 is also covered with the protective material 17 together with the bonding wires 16 and the like, protection from contaminants such as dust and impurities in the pressure medium in the measurement pressure chamber 4 should be achieved. Can be.

By the way, in the configuration of this embodiment, the rubber film 1
3 is attached to the wall of the partition wall 8 on the side of the measuring pressure chamber 4 where the pressure is high.
Is applied to the partition wall 8 (the bottom surface of the accommodation recess 8a). For this reason, compared with the case where the rubber film 13 is provided on the opposite side, the sealing property is excellent and the rubber film 13 is provided.
This eliminates the need for such a large mounting strength. Moreover, the pressure sensor 1 itself has a detection pressure of 0.2M.
It is configured for low pressure of Pa or less. This allows
As described above, the thickness of the fixing portion 13b of the rubber film 13 is increased, and the rubber film 13 can be attached by an easy means of adhesion.

Further, as compared with the case where both sides of the pressure sensor chip 5 are covered with a protective material such as silicon gel,
As described above, the mounting of the rubber film 13 and the pressure sensor chip 5 and the formation of the protective material 17 can be performed from one side of the case 2, so that the mounting operation is facilitated. Also, since only the rubber film 13 is added, the configuration is simple,
Of course, it can be inexpensive.

As described above, according to the present embodiment, the protection rubber film 13 is provided between the back surface of the diaphragm portion 14a of the pressure sensor chip 5 and the reference pressure chamber 3, so that the reference pressure chamber 3 While preventing the diaphragm portion 14a of the pressure sensor chip 5 from being contaminated by the contaminants contained in the introduced pressure medium, and thereby preventing adverse effects such as characteristic changes,
With a relatively simple configuration, an excellent effect that the assembling work can be easily performed can be obtained.

In the above-described embodiment, the differential pressure (relative pressure) is detected. However, the pressure sensor of the present invention can be used, for example, by sealing the reference pressure chamber 3 in a vacuum state to obtain the absolute pressure of the measured pressure. Can also be configured as a sensor for detecting, so that the use can be expanded. Also,
In the above embodiment, the rubber film 13 is configured as having the thin pressure receiving portion 13a and the thick fixing portion 13b.
It is also possible to adopt a sheet having a constant thickness. The material of the rubber film 13 can be selected from fluorine rubber, acrylic rubber, NBR, silicon rubber, fluorosilicone rubber and the like according to the use environment such as the type of pressure medium and temperature.

In addition, the pressure medium may be a liquid or other gas, and the space between the rubber film 13 and the diaphragm 14a may be filled with silicone oil or the like instead of air. Thus, the temperature characteristics can be improved. In addition, various modifications are possible for the position where the rubber film 13 is provided, the fixing structure, the configuration of the case and the pressure chamber, and the like. The present invention can be implemented with appropriate modifications without departing from the gist.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and is an enlarged vertical sectional view showing a configuration of a mounting portion of a pressure sensor chip.

FIG. 2 is a longitudinal sectional view showing the entire configuration of the pressure sensor.

[Explanation of symbols]

In the drawing, 1 is a pressure sensor, 2 is a case, 3 is a reference pressure chamber, 4 is a measurement pressure chamber, 5 is a pressure sensor chip, 8 is a partition wall, 8a is a housing recess, 8b is a communication hole, 13 is a rubber film, 1
3a is a pressure receiving portion, 13b is a fixed portion, 14a is a diaphragm portion, and 17 is a protective material.

Claims (6)

[Claims] In a case, a reference pressure chamber serving as a reference pressure, a measurement pressure chamber into which a measurement pressure is introduced, and pressures of these two pressure chambers are provided on front and back surfaces of a diaphragm portion. A pressure sensor comprising a pressure sensor chip, and configured to detect a pressure difference between the measured pressure and a reference pressure, wherein the pressure sensor chip partitions between a back surface of a diaphragm portion of the pressure sensor chip and the pressure chamber. A pressure sensor comprising a protective rubber film that elastically deforms in response to a pressure change in a pressure chamber. 2. The pressure sensor according to claim 1, wherein the rubber film is integrally formed with a fixing portion for attachment outside the pressure receiving portion receiving the pressure of the pressure chamber, and the pressure receiving portion is thinner than the fixing portion. The pressure sensor according to claim 1, wherein 3. The pressure detected by the pressure sensor chip is 0.2 MPa or less.
Or the pressure sensor according to 2. 4. The communication hole portion of the wall surface on the pressure chamber side, which has a high pressure, among the partition walls that partition the reference pressure chamber and the measurement pressure chamber and have communication holes that communicate the two chambers. 4. The device according to claim 1, wherein said rubber film is attached to a back surface of said rubber film.
The pressure sensor according to any one of the above. 5. The pressure sensor according to claim 1, wherein a front surface of the pressure sensor chip is covered with a protective material. 6. The sensor according to claim 1, wherein the reference pressure chamber is sealed in a vacuum state so that the reference pressure chamber can be configured as a sensor for detecting an absolute pressure of a measured pressure. Or a pressure sensor.