JP2002188973A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor capable of detecting the pressure highly accurately with a simple formation. SOLUTION: In this sensor, an upper glass 2 having an opening part 7 formed on the center, silicone 3 having a diaphragm 3b formed on the center, and a lower glass 4 having an opening part 9 formed on the center are laminated. A resonance driving circuit 5 is installed between the upper glass 2 and the diaphragm 3b, and a voltage having a prescribed frequency is applied to the diaphragm 3b, to thereby vibrate the diaphragm 3b. An amplitude measuring circuit 6 is installed between the lower glass 4 and the diaphragm 3b, to measure the amplitude of vibration generated on the diaphragm 3b. The pressure on the pressure side to be measured is acquired based on the measured amplitude in a pressure detection part 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 measuring a pressure during gas supply or the like.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open Nos. Hei 5-90615 (hereinafter referred to as a first conventional example) and Japanese Unexamined Patent Publication No. Hei 8- Japanese Patent No. 5494 (hereinafter referred to as a second conventional example) is known.

FIG. 5 is an external view showing a configuration of a pressure sensor described in a first conventional example, and FIG. 6 is a circuit configuration diagram.
As shown in FIG. 5, the pressure sensor 101 includes a silicon diaphragm 102 to which a vibrator 104 having an “H” shape is attached. The vibrator 104 is covered with a shell 103, and the space in which the vibrator 104 vibrates is kept in a vacuum.

As shown in FIG. 6, a magnetic field H is applied to a vibrator 104 having an “H” shape in a direction indicated by an arrow H in FIG. Causes an electromagnetic force to be generated in the beam 104a,
04 starts to vibrate in the direction perpendicular to the paper surface according to Fleming's left hand rule.

[0005] In the other beam 104b of the vibrator 104, an alternating electromotive force e is generated by the conductor crossing the magnetic flux. Then, after the electromotive force e is amplified by the amplifier 105 and then positively fed back to the drive current side, the vibrator 104 self-excites at its natural frequency. Amplifier 1
The pressure applied to the silicon diaphragm 102 can be detected based on the magnitude of the oscillation of the voltage signal output from the signal line 05.

However, the pressure sensor described in the first conventional example requires complicated processing because it is necessary to perform advanced processing to form the vibrator 104 mounted on the silicon diaphragm 102 or the shell 103 covering the vibrator 104. Silicon process is required. Furthermore, the structure becomes complicated because a mechanism for generating magnetism is required.

Further, the pressure sensor disclosed in the second conventional example has a configuration for measuring pressure by using a large number of diaphragms arranged on silicon. However, in this pressure sensor, a wide range of vacuum pressure is measured by one sensor by arranging a large number of sensors. Therefore, although the measurement range can be expanded, the sensor becomes large as a whole. .

[0008]

As described above, the pressure sensor described in the first conventional example enables high-precision pressure detection, but requires a complicated process at the stage of manufacturing the diaphragm. In addition, since the circuit becomes complicated, there is a disadvantage that the device becomes large and the cost becomes high. Further, in the pressure sensor described in the second conventional example, although the measurement range can be widened, there is a disadvantage that the sensor becomes large and complicated.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a pressure detecting device having a simple structure and capable of detecting pressure with high accuracy. It is to provide a sensor.

[0010]

In order to achieve the above object, the invention according to claim 1 of the present application is installed between a measured pressure side and an atmospheric pressure side to detect the pressure on the measured pressure side. A pressure sensor having a diaphragm formed in a central portion and a peripheral portion serving as a supporting portion, a diaphragm substrate fixed to the supporting portion on one surface side of the diaphragm substrate, and having an opening near the central portion. A first substrate disposed on the pressure side to be measured, and the support portion on the other surface side of the diaphragm substrate, having an opening near a central portion, and disposed on the atmospheric pressure side; A second substrate to be
A voltage is applied between the first electrode formed on the first substrate, the second electrode formed on the second substrate, the first electrode, and the diaphragm substrate to vibrate the diaphragm. Vibration generating means, amplitude measuring means for measuring the amplitude of vibration generated in the diaphragm, and pressure detection for measuring the pressure on the measured pressure side based on the magnitude of the amplitude measured by the amplitude measuring means. And means.

The invention according to claim 2 is characterized in that the diaphragm substrate is formed of silicon, and the diaphragm is a silicon diaphragm.

According to a third aspect of the present invention, the first electrode is provided on the inner surface of the opening of the first substrate and near the upper and lower openings, and the second electrode is The second substrate is provided near the inner surface of the opening and the upper and lower openings.

According to a fourth aspect of the present invention, the first substrate and the second substrate are made of glass.

The invention according to claim 5 is characterized in that the first substrate and the diaphragm substrate and the second substrate and the diaphragm substrate are fixed by anodic bonding.

According to a sixth aspect of the present invention, when the first substrate has a rectangular shape, and at least one corner is cut out, the first substrate and the diaphragm substrate are fixed when the first substrate is fixed to the diaphragm substrate. The upper surface of the diaphragm substrate exposed from the cutout portion is a connection point with the vibration generating means and the amplitude measuring means.

According to a seventh aspect of the present invention, the first substrate and the diaphragm substrate each have a rectangular shape, and at least one corner is cut out. An end electrode connected to the second electrode is formed on an upper surface side of the second substrate exposed from the cutout portion when the second substrate is fixed.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing a configuration of a pressure sensor according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the pressure sensor. As shown in FIG. 1, the pressure sensor 1 is roughly divided into an upper glass (first substrate) 2, a silicon (diaphragm substrate) 3, and a lower glass (second substrate) 4. Further, as shown in FIG. 2, a resonance driving circuit (vibration generating means) 5, an amplitude measuring circuit (amplitude measuring means) 6, and a pressure detecting section (pressure detecting means) 13
And In the present embodiment, the upper glass 2 is referred to as “upper”, and the lower glass 4 is referred to as “lower”.

The upper glass 2 has a substantially rectangular flat plate shape, and two diagonal corners of the four corners are cut off in an arc shape. A circular opening 7 is formed in the center of the upper glass 2, and an electrode (first electrode) 8 is formed so as to cover the inner side surface of the opening 7 and the peripheral portions of the upper surface and the lower surface. Is formed. The electrode 8 can be formed by evaporating a metal such as aluminum.

The silicon 3 has a substantially rectangular flat plate shape, and one of the four corners is cut off in an arc shape. A peripheral portion of the silicon 3 is a supporting portion 3a having a large thickness, and a central portion thereof is a circular diaphragm 3b having a small thickness.

The lower glass 4 also has a substantially rectangular flat plate shape, and one of the four corners is cut off in an arc shape to form a cutout 4a. Further, an opening 9 having the same diameter as that of the opening 7 formed in the upper glass 2 is formed at the center. Further, an electrode (second electrode) 10 is formed so as to cover the inner side surface of the opening 9 and the peripheral portions of the upper surface and the lower surface. The electrode 10 is connected to an end electrode 12 formed in the cutout 4a via a connection electrode 11 formed on the lower surface of the lower glass 4. The end electrode 12
Reaches the upper surface of the upper glass 2 via the side surface of the notch 4a. Therefore, the electrode section 12a on the upper surface side can be electrically connected to the amplitude measuring circuit 6.

The above-mentioned upper glass 2, silicon 3 and lower glass 4 are laminated in the direction shown in FIG. 1, and their contact portions are firmly bonded by anodic bonding. As a result, when viewed from above, the configuration is as shown in FIG.

As shown in FIG. 2, a resonance drive circuit 5 is connected between the electrode 8 formed on the upper glass 2 and the silicon 3 so that the resonance drive circuit 5 is connected between the upper glass 2 and the diaphragm 3b. Is configured to be able to apply a voltage of a fixed frequency. The resonance drive circuit 5 is connected to the silicon 3 exposed at reference numeral P1 shown in FIG. 3 and the electrode 8, and the amplitude measurement circuit 6 is connected to the silicon 3 exposed at reference numeral P1 and the electrode portion 12a.

Further, the electrode 10 formed on the lower glass 4
An amplitude measuring circuit 6 is connected between the (end electrode 12) and the silicon 3, so that the amplitude of the vibration generated in the diaphragm 3b can be measured.

The pressure sensor 1 measures the pressure on the measured pressure side by arranging the upper glass 2 side on the atmospheric pressure side and the lower glass 4 side on the measured pressure side (for example, in a gas cylinder). Is what you do.

Next, the operation of the above embodiment will be described. In the pressure sensor 1 of the present embodiment, the pressure on the measured pressure side is detected by applying vibration to the diaphragm 3b and measuring the amplitude of the generated vibration. Hereinafter, this principle will be described.

The resonance frequency of the diaphragm 3b is expressed by the following equation (1).

[0027]

(Equation 1) Here, f is a resonance frequency, k is a spring constant, and m is a mass.

The vibration displacement x is expressed by the following equation (2).

[0029]

(Equation 2) Here, ω = 2πf.

As shown in equation (1), when the material resonates, the amplitude x is infinite in an ideal state. However, due to various restrictions, the state is not ideal. In particular, when the diaphragm 3b vibrates as in the present embodiment, the atmosphere in contact with the diaphragm 3b is a major factor that hinders the vibration.

Here, the vibration damping ratio h is given by the following (3)
Defined as an expression.

[0032]

(Equation 3) Further, based on the equation (3), the sensitivity coefficient MA can be obtained by the following equation (4).

[0033]

(Equation 4) Here, in the equation (4), u is a frequency ratio, and u = f
/ Fn = (frequency of vibration to be measured) / (undamped natural frequency of pendulum).

FIG. 4 is a characteristic diagram showing the relationship between the frequency ratio u (= f / fn) and the sensation coefficient MA. When attention is paid to u = 1.0 in FIG. It is understood that the ratio changes greatly with the change in the ratio h.

Here, if the factor that attenuates the amplitude is only the atmosphere, the attenuation ratio h can be considered as the atmospheric pressure. Therefore, in the pressure sensor 1 according to the present embodiment,
The amplitude when the diaphragm 3b is vibrated at the resonance frequency of the diaphragm 3b is measured, and the damping ratio h = 0 (ie,
The air pressure is measured by comparing with the amplitude when the pressure difference between the upper and lower portions of the diaphragm 3b shown in FIG. 2 is zero).

The amplitude x is obtained by different equations according to the magnitude of the attenuation ratio h. That is, the following equations (5), (6) and (7) are obtained.

[0037]

(Equation 5)

(Equation 6)

(Equation 7) Here, A and B are constants.

By solving the above equations (5) to (7) for the damping ratio h, the damping ratio h can be obtained from the amplitude x. Further, the pressure can be obtained based on the damping ratio h.

As described above, in the pressure sensor 1 according to the present embodiment, the diaphragm 3b is installed between the atmospheric pressure side and the measured pressure side, and the diaphragm 3b is vibrated at the resonance frequency. The amplitude of the vibration generated in 3b is measured, and the pressure on the measured pressure side is measured based on the amplitude. Therefore, highly accurate pressure detection can be achieved with a very simple configuration.

As shown in FIG. 1, the upper glass 2, the silicon 3, and the lower glass 4 have a laminated structure.
Further, since the electrodes for connecting the resonance drive circuit 5 and the amplitude measuring device 6 are formed on the upper surface side of the laminated structure, the wiring becomes easy, and the mounting operation and the like can be simplified.

Although the pressure sensor according to the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and each component may have any configuration having the same function. Can be replaced.

For example, the diaphragm 3b does not necessarily have to be circular, but may be rectangular or elliptical. Further, in place of the upper glass 2 and the lower glass 4, a substrate having another similar function can be used.

[0043]

As described above, in the pressure sensor according to the present invention, the diaphragm substrate is sandwiched between the first substrate and the second substrate so as to be laminated, and the diaphragm is subjected to vibration, and the amplitude of the vibration is given. Ask for. Then, based on the amplitude, the pressure on the side of the driven constant pressure is measured. Therefore, the configuration can be simplified, and highly accurate pressure measurement can be performed.

Further, one corner of the first substrate is cut out, and when the first substrate and the diaphragm substrate are laminated,
Since the vibration generating means and the amplitude measuring means are connected to the upper surface of the diaphragm substrate exposed at the notched portion,
Connection of electric wiring becomes easy. Furthermore, when the first substrate and one corner of the diaphragm substrate are cut out, and the first substrate, the diaphragm substrate and the second substrate are laminated,
On the upper surface of the second substrate exposed at the notched portion,
Since the end electrodes are formed and the electric wires are connected using the end electrodes, the electric wires can be easily connected.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view illustrating a configuration of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a pressure sensor according to one embodiment of the present invention.

FIG. 3 is a configuration diagram when a pressure sensor according to an embodiment of the present invention is viewed from above.

FIG. 4 is a characteristic diagram showing how a sensitivity coefficient changes with respect to a frequency ratio.

FIG. 5 is a perspective view showing a configuration of a pressure sensor described in a first conventional example.

FIG. 6 is a configuration diagram of a circuit used in the pressure sensor described in the first conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pressure sensor 2 upper glass (first substrate) 3 silicon (diaphragm substrate) 3a support 3b diaphragm 4 lower glass (second substrate) 4a notch 5 resonance drive circuit (vibration generating means) 6 amplitude measurement circuit ( Amplitude measuring means) 7 Opening 8 Electrode (first electrode) 9 Opening 10 Electrode (second electrode) 11 Connecting electrode 12 End electrode 12a Upper electrode 13 Pressure detector (Pressure detector)

Claims (7)

[Claims] 1. A pressure sensor installed between a measured pressure side and an atmospheric pressure side to detect a pressure on the measured pressure side, wherein a diaphragm is formed in a central portion and a peripheral portion is a support portion. A diaphragm substrate, a first substrate fixed to the support portion on one surface side of the diaphragm substrate, having an opening near a central portion, and disposed on the measurement pressure side; A second substrate fixed to the supporting portion on the other surface side, having an opening near the center, and disposed on the atmospheric pressure side; and a first electrode formed on the first substrate A second electrode formed on the second substrate; a vibration generating means for applying a voltage between the first electrode and the diaphragm substrate to vibrate the diaphragm; Amplitude measuring means for measuring the amplitude of a vibrating vibration , A pressure sensor, characterized in that it comprises, based on the magnitude of the amplitude measured by the amplitude measuring means, and a pressure detecting means for measuring the pressure of the object to be measured pressure side. 2. The pressure sensor according to claim 1, wherein the diaphragm substrate is formed of silicon, and the diaphragm is a silicon diaphragm. 3. The first electrode is provided on the inner surface of the opening of the first substrate and near the upper and lower openings, and the second electrode is provided on the opening of the second substrate. The pressure sensor according to claim 1, wherein the pressure sensor is provided in the vicinity of the opening on the inner side surface, the upper surface side, and the lower surface side. 4. The apparatus according to claim 1, wherein said first substrate and said second substrate are made of glass.
The pressure sensor according to any one of the preceding claims. 5. The method according to claim 1, wherein the first substrate and the diaphragm substrate are disposed between the first substrate and the diaphragm substrate, and the second substrate and the diaphragm substrate are disposed between the second substrate and the diaphragm substrate.
Attached by anodic bonding, characterized in that:
The pressure sensor according to claim 4. 6. The first substrate has a rectangular shape and has at least one corner cut out, and is exposed from the cutout when the first substrate and the diaphragm substrate are fixed. The pressure sensor according to any one of claims 1 to 5, wherein an upper surface of the diaphragm substrate is used as a connection point with the vibration generating means and the amplitude measuring means. 7. The first substrate and the diaphragm substrate each have a rectangular shape, and at least one corner is cut out to fix the first substrate, the diaphragm substrate, and the second substrate. 2. An end electrode connected to the second electrode is formed on an upper surface of the second substrate exposed from the cutout portion.
The pressure sensor according to claim 6.