JPH0610641B2 - Pressure sensor for high temperature fluid - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates to pressure sensors, and in particular to improvements in pressure sensors used to measure the pressure of hot fluids.

[Prior Art] Pressure sensors are widely used in various fields to measure the pressure of fluid such as gas or liquid, and in recent years, in particular, they are often used under extremely severe operating environments of high temperature and high pressure. . Therefore, the sensor used for measuring the pressure of such a high temperature fluid is required to have an ability to accurately measure the pressure without being affected by the surrounding environment, particularly the temperature thereof.

For example, when such a pressure sensor is used as a combustion pressure sensor for an internal combustion engine, it is required to have the ability to accurately measure the pressure for a long time without being affected by the combustion gas having a temperature of 1000 ° C. or higher. .

FIG. 2 shows an example of a conventional pressure sensor,
This pressure sensor transmits the pressure P of the combustion gas acting on the surface of the diaphragm portion 10 as a compressive force W to the force conversion element 14 via the thermal insulator 12 and converts it into an electric signal output from the force conversion element 14. Based on this, the pressure P of the combustion gas was measured.

However, when trying to measure the pressure of the combustion gas having a temperature higher than 1000 ° C., the heat insulator 12 provided between the diaphragm portion 10 and the force conversion element 14 alone is used to heat the heat transmitted to the force conversion element 14. Can not be sufficiently shielded,
The performance of the force conversion element 14 itself deteriorates.

For this reason, conventionally, the block portion 22 is provided integrally with the front surface side of the diaphragm portion 10.
By absorbing the heat of the combustion gas that has come in the vicinity, it is possible to suppress the temperature rise of the diaphragm portion 10 itself and prevent the heat from being transferred to the force conversion element 14 even when the pressure of the high-temperature and high-pressure combustion gas is measured. It had been.

Conventionally, the force conversion element 1 used for such a pressure sensor
The strain gauge type 4 represented by a compression type load cell is generally known.

However, with the conventional force conversion element 14,
None were constructed with a new compression force detection method.

FIG. 3 shows an example of a conventional strain gauge type force conversion element 14.

This force conversion element has a quadrangular prismatic strain element 16 to which a compressive force W is applied.
A semiconductor strain gauge 17 is attached to 6a using an adhesive 17a. Then, the plurality of strain gauges 17 attached to the respective side surfaces are electrically connected to each other so as to form a Wheatstone bridge circuit.

Then, the flexure element 1 generated corresponding to the applied compressive force W
The distortion of 6 is output as a voltage signal from the wheelstone bridge circuit.

[Problems to be Solved by the Invention] However, the conventional pressure sensor, in particular, the force conversion element 14 thereof.
Had the following problems.

First Problem First, the force conversion element 14 used in the conventional pressure sensor.
In order to reduce the adverse effect on the detection characteristics caused by the increase or decrease in the resistance value of the semiconductor strain gauge 17 due to the temperature change, a plurality of semiconductor strain gauges 17 were attached to each side surface 16a of the strain body 16. Then, the electrodes 17 of each of these strain gauges 17
Lead wire 18 from b, 17b to terminals 18, 18
a, 18a are pulled out and each of these terminals 1
Lead wires 19 and 19 were connected to 8 and 18, and each strain gauge 17 was connected so as to form a Wheatstone bridge circuit.

For this reason, the manufacturing process of the force conversion element 14 and by extension, the pressure sensor is complicated, and high know-how is required for the manufacturing thereof, so that the manufactured pressure sensor becomes expensive and the characteristics of each product vary. There was a problem that it would grow.

Second Problem Further, in the force conversion element 14 used in the conventional sensor, the strain gages 16 are formed by using a plurality of strain gauges 17 with an adhesive 17a.
It is attached to the side surface 16a of the. Therefore, the adhesive 17a
There is a problem in that the adverse effects on the measurement characteristics such as creep and hysteresis caused by are inevitable and the reliability is poor. Further, the attachment of the strain gauge 17 using the adhesive 17a requires a great deal of know-how, and there is a problem that the strain gauge characteristics vary greatly due to the adhesion.

[Object of the Invention] The present invention has been made in view of such conventional problems, and an object of the present invention is to solve the above-mentioned problems, to provide a highly reliable and inexpensive pressure for a high temperature fluid. To provide a sensor.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention transmits the pressure of the high-temperature fluid acting on the surface of the diaphragm portion to the force conversion element as a compressive force, and outputs the pressure from the force conversion element. In the pressure sensor for measuring the pressure of the high temperature fluid based on the electric signal, the force conversion element is formed to have a {110} crystal face as a face to which a compressive force is applied, and the crystal face is the diaphragm part. And a first electrode provided on the Si single crystal body so as to face the direction of 45 degrees from the <001> direction of the crystal on the {110} plane of the Si single crystal body. And a second electrode provided opposite to each other in a direction of 45 degrees from the <110> direction, and one of the first and second electrodes is used as an output electrode and the other is used as an input electrode. Electrodes And one end of the Si single crystal is joined to the {110} crystal face of the Si single crystal, and the other end is formed to be in contact with the diaphragm part. The pressure applied to the diaphragm part is used as a compressive force S
A composite pedestal that is transmitted perpendicularly to the crystal plane of the i single crystal and is joined to the {110} plane of the Si single crystal, and a surface of the Si single crystal that faces the surface to which the pedestal is joined. A stem that is joined to the stem, the stem is joined to a surface facing a surface to which the pedestal of the Si single crystal body is joined, and a support base for supporting the Si single crystal body; A plurality of output electrode terminals for extracting an electric signal output from the output electrode to the outside, a plurality of input electrode terminals for supplying a current to the input electrode from the outside, and the input electrode terminal, the output electrode terminal and the support Holding means for integrally holding the base, and applying a compressive force perpendicularly to the crystal plane of the Si single crystal body while applying a current from the input electrode terminal to the Si single crystal body, and from the output electrode terminal to the diaphragm. Temperature acting on the surface of the part And outputs a voltage corresponding to the pressure of the body.

Attention Point The present inventors have developed a pressure sensor for high temperature fluid using a novel pressure detecting means whose principle is completely different from that of the conventional force conversion element.

The points of interest in developing the pressure detecting means used in the pressure sensor of the present invention, particularly the force converting element thereof, will be described below.

First point of interest The force conversion element used in the conventional pressure sensor uses a plurality of semiconductor strain gauges in order to reduce the adverse effect on the characteristics caused by the resistance value of the semiconductor strain gauges that increases and decreases with changes in temperature. And formed a Wheatstone bridge circuit.

A first point of interest of the present invention is to replace a Wheatstone bridge circuit formed by using such a plurality of semiconductor strain gauges and configure a plurality of strain gauges with one Si single crystal body. For this reason, in the present invention, a pair of output electrodes and input electrodes are provided to intersect each other on one Si single crystal body, and preferably, they are provided to face each other in a direction orthogonal to each other.

By doing so, according to the present invention, for the reason described later (detailed in the section (g) of the action column), the adverse effect on the characteristics caused by the temperature fluctuation is reduced, and
The problem of can be solved.

Second point of interest However, as described above, even if the Si single crystal body in which the pair of output electrodes and the input electrodes are provided orthogonally to each other is used, this Si single crystal body is used as a strain element as in the conventional case. If the adhesive is attached to the side surface, the above-mentioned second problem cannot be solved.

A second point of interest of the present invention is to apply a compressive force perpendicularly to the crystal plane of the Si single crystal body, and to apply Si based on this compressive force.
This is because a new force detection method has been adopted, in which the compression force is detected using the piezoresistive effect of a single crystal.

That is, in the conventional force conversion element, a plurality of strain gauges are attached to the side surface of the flexure element using an adhesive, and the compression force is detected as the compression strain of the flexure element. Therefore, the compressive strain of the flexure element is transmitted to each strain gauge through the adhesive, and the adhesive is liable to be adversely affected by creep, hysterisis, etc., and the reliability is low. .

On the other hand, in the present invention, one of the crystal planes of the Si single crystal body is joined to the pedestal, and the other crystal plane is joined to the support base.
It employs a novel structure that does not exist in the past, in which a compressive force is applied perpendicularly to the crystal plane of a single crystal.

Therefore, even if an adhesive is used to bond the Si single crystal body to the pedestal and the support base, the adverse effects of creep, hysteresis, etc. due to the adhesive are significantly reduced, and the reliability of the measured data is extremely high. Becomes In order to surely remove the influence of such an adhesive, the bonding of the Si single crystal body with the support base and the pedestal is disclosed in, for example, Japanese Patent Publication No. 53-28747, without using an adhesive. It is preferable to use the electrostatic bonding method described above.

Third point of interest By the way, when the compressive force is measured using such a Si single crystal body, it is necessary to output a measurement voltage corresponding to the applied compressive force from the Si single crystal body. It is said that

From such a viewpoint, the present inventors have studied the crystal plane of the Si single crystal body so that the piezoresistive coefficient π ₆₃ of the Si single crystal body has a large value.

As a result of this examination, as a surface to which pressure is applied (110)
It has been found that it is necessary to form a Si single crystal so as to have a face crystal face.

Further, the inventors of the present invention used a Si single crystal having such a (110) crystal plane, and the heat generation due to the application of an excessive voltage to the Si single crystal causes the characteristics thereof to change. In the case of applying a voltage in a range that does not cause a bad influence, studies have been conducted to output a voltage ΔV of a practically sufficient magnitude.

As a result of this study, it was found that in order to output a large voltage ΔV from the Si single crystal body, the thickness of the Si single crystal body should be made as small as possible. In particular, it has been found that the thickness of this Si single crystal body should be 50 μm or less, preferably 20 μm or less in order to output ΔV of a practically sufficient magnitude.

Therefore, in the present invention, while having a (110) crystal face as a face to which a compressive force is applied, the impurity concentration is controlled in the range of 1 × 10 ¹⁵ / cm ³ to 1 × 10 ²¹ / cm ³ , and its thickness The Si single crystal body is formed to have a thickness of 50 μm or less.

Fourth Point of Interest In the conventional force conversion element, as shown in FIG. 3, in order to extract the output voltage from the semiconductor strain gauge 17, the lead wire 18a is provided between the electrode 17b of the strain gauge 17 and the terminal 18. And the lead wire 19 from the terminal 18
The lead wire 19 was drawn so that the four strain gauges 17 form a Wheatstone bridge circuit. Therefore, in order to manufacture a force conversion element of a certain quality, a high level of know-how of the operator is required, and depending on how the lead wire 19 is routed, ambient noise is likely to be mixed and there is a problem in electrical measurement. .

A fourth point of interest of the present invention is to shorten the length of the wiring so that the electrical connection can be easily performed.

Therefore, the present invention provides an output electrode provided on a Si single crystal body, an output electrode terminal to which an input electrode is connected,
The input electrode terminal and the supporting base for joining and supporting the Si single crystal body are formed so as to be integrally held by using a holding means.

By doing so, after bonding the Si single crystal body on the support base, simply connecting the input electrode and the output electrode to the input electrode terminal and the output electrode terminal which are integrally held with the support base, respectively. Good. Therefore, it is possible to solve the problem that the lead wire has to be drawn and connected as in the conventional case, and it is possible to obtain a force conversion element that has simple wiring, is resistant to noise, and is low in cost.

[Operation] FIG. 1 shows a pressure sensor for high temperature fluid of the present invention.

(A) In this pressure sensor, the diaphragm portion 10 is attached and fixed to the tip opening portion of the sensor case 20 formed in a substantially cylindrical shape.

When a high temperature fluid is applied to the surface of the diaphragm portion 10, the pressure P acts as a compressive force on the force conversion element 14 via the thermal insulator 12 and the pedestal 42, and the force conversion element 1
A measurement voltage corresponding to the pressure P is output from the lead wire 4 through the lead wire 56.

When measuring the high temperature / high pressure fluid pressure P using such a pressure sensor, the surface 12 of the diaphragm portion 10 is exposed to the high temperature / high pressure fluid. For this reason, the sensor case 20 is made of a material having good thermal conductivity so that the heat transferred from the high-temperature / high-pressure fluid to the diaphragm portion 10 does not go around to the force conversion element 14 via the sensor case 20, for example, It is preferable that heat is released from the mounting and fixing screw groove 28 of the case 20 to the cylinder head portion (not shown).

(B) FIG. 4 shows an example of the force conversion element 14 used in the pressure sensor of the present invention. FIG. 4 (A) is its plan view and FIG. 4 (B) is its side view. Is.

The force conversion element 14 includes a Si single crystal body 30 formed to have a (110) crystal plane as a plane to which a compressive force W is applied, and a (110) plane crystal plane 32 of the Si single crystal body 30. It includes a pedestal 40 that is joined and that transmits the compressive force W perpendicularly to its crystal plane 32, and a stem 60 that is joined to another crystal plane 34 of this Si single crystal body 30. And the S
The first electrodes 50, 5 provided on the surface of the i single crystal body 30 so as to face each other in the direction of 45 degrees from the <001> direction of the crystal.
0'and second electrodes 52, 52 'provided opposite to each other in the direction of 45 degrees from the <10> direction are provided, and any of these first and second electrodes is provided. One of them 50, 50 'is used as an output electrode and the other 52, 52' is used as an input electrode.

(C) In the present invention, the stem 60 is made of Si.
A support base 62 that is joined to the other crystal plane 32 of the single crystal body 30 and supports the Si single crystal body 30, and a plurality of input electrodes for passing a current from the outside to the input electrodes 52 and 52 '. Terminals 66 and 66 ', a plurality of output electrode terminals 64 and 64' for taking out electric signals output from the output electrodes 52 and 52 ', and these electrode terminals 64 and 64',
66, 66 'and holding means for integrally holding the support base 62.

In FIG. 4, the stem 60 is the electrode terminal 6 of each of these.
4, 64 ', 66, 66' are arranged around the support base 60 in a ring shape so as to be substantially symmetrical. The stem 60 uses an outer ring 70 and a sealing glass 68 as a holding means, and a support base 62 and electrode terminals 64, 64 ', 66, 66 are provided in a substantially cylindrical outer ring 70 having an open upper end. It is formed by integrally attaching and fixing 66 'with a sealing glass 68.

Here, the electrode terminals 64, 64 ', 66, 6
6'is attached such that one end side thereof is substantially flush with the crystal plane 32 of the Si-end crystal body 30, and each electrode 50, 50 ', 52, 5 provided on the Si single crystal body 30.
2'and a gold wire 54 are connected.

The other end side of each of the electrode terminals 64, 64 ', 66, 66' is drawn out to the outside through an insertion hole 72 provided in the bottom surface of the outer ring 70. And at the end there is a first
A lead wire 56 shown in the figure is connected, and is electrically connected to an external measuring device via the lead wire 56.

In this way, the force conversion element 14 used in the present invention has the output electrode terminals 64, 64 'and the input electrode terminals 66,
Since 66 ′ is integrally formed with the support base 62 as the stem 60, the electrodes 50, 50 ′, 52, 52 ′ of the Si single crystal body 30 bonded to the support base 62 and the electrode terminals are formed. The electrical connection is completed only by connecting the 64, 64 ', 66, 66' via the short lead wire 54 of, for example, about 10 mm, and the electrical wiring becomes extremely simple.

Therefore, unlike the conventional case, the wiring of the semiconductor strain gauge is not laid out and electrically connected.
The electrical connection can be performed easily and surely without requiring special know-how. Furthermore, according to the present invention, since the electrical wiring is also extremely short, noise from the outside is not mixed into the wiring that has been routed as in the conventional case, and an extremely reliable force conversion element can be obtained. .

Although the outer ring and the sealing glass are used as the holding means in FIG. 4, the holding means are the electrode terminals 64 and 6.
Other means can be adopted as long as 4 ', 66, 66' and the support base 62 can be integrally held, and for example, a ceramic package may be used.

(D) Next, using this force conversion element 14, a compression force W applied to the pedestal 40 (pressure P applied to the diaphragm portion 10)
The case of measuring is explained.

First, when a compressive force W is applied vertically to the pedestal 40, the compressive force W is evenly distributed by the pedestal 40, and a compressive stress δ _Z = W / A is given perpendicularly to the crystal plane 32 of the Si single crystal body 30. To work. Here, A represents the area of the bonding surface of the pedestal 40 to the Si single crystal body 30. At this time, when a current I is made to flow from the input electrodes 52, 52 'to the Si single crystal body 30, the Si single crystal body 30 on which the compressive stress δ _Z acts is applied.
Is the voltage Δ from the output electrodes 50, 50 '
V is output. ΔV = b · ρ · J ₂ · π _{63 ′} · δ _Z · k (1) where ρ is the specific resistance of the Si single crystal body 30, J ₂ is the current density, and π ₆₃ ′. Is a piezoresistance coefficient and k is a constant determined by the electrode shape of the Si single crystal body.

One of the features of the present invention is that the output electrodes 50 and 50 'output the voltage ΔV corresponding to the compressive force, so that the Si single crystal body 30 has a sufficiently large value for the piezoresistive coefficient π ₆₃ ′.
Has been formed.

That is, the present inventors have changed the direction in which the electrodes are provided for the Si single crystal body 30 having the following four typical crystal planes (100), (110), (111), and (211), and The calculation of the piezoresistive coefficient π ₆₃ ′, which is essential for obtaining the voltage ΔV, was performed from the single crystal body 30. As a result, in the case of (100), (111) and (211), the piezoresistance coefficient π
₆₃ 'became zero. On the other hand, in the case of (110), the electrodes are provided in the direction of 45 ° from the <001> direction or the direction of 45 ° from <10>, so that the absolute values are equal and the maximum piezoresistance coefficient π _63. It turned out that'is present.

FIG. 5 shows the calculation result of the piezoresistive coefficient π ₆₃ ′ of a p-type (110) plane Si single crystal having a specific resistance of 7.8 Ωcm. From the figure, the output electrode is 4 from the <001> direction.
By providing the input electrode in the direction of 5 ° and in the direction of 45 ° from the <10> direction, the maximum piezoresistive coefficient π ₆₃ ′ is obtained.
You can see that you can get

It should be noted that the output electrodes 50 and 50 'are arranged in a direction of 45 ° from <10>, and the input electrodes 52 and 52' are arranged in a direction of 4 ° from <001>.
Even when it is installed in the direction of 5 °, the piezoresistance coefficient π ₆₃ ′
Can be similarly utilized and the force conversion element which is the object of the present invention can be realized.

The crystal directions of [001] and [10] are typical crystal directions of the (110) plane Si single crystal 30, and the crystal directions equivalent to these crystal directions are exactly the same. Can be thought of.

Table 1 shows a crystal plane equivalent to the crystal plane of the (110) plane of the Si single crystal body 30 and a crystal direction equivalent to the crystal orientation of [001] and [10]. As is clear from this table, the Si single crystal body has a plurality of crystal planes equivalent to the (110) plane. Therefore, the force conversion element 1000 of the present invention can be formed by using a Si single crystal body having a crystal plane equivalent to the (110) plane.

The crystal plane equivalent to the (110) crystal plane is {110}
Further, the crystal directions equivalent to [001] and [10] are generally represented by <001> and <110>.

Although the piezoresistance coefficient π ₆₃ ′ of the p-type Si single crystal body 30 is shown in FIG.
Even in a single crystal, its piezoresistive coefficient π ₆₃ ′ is
It has the same size as that of the p-type and exists in the same manner.

In this way, the pressure sensor of the present invention applies the pressure p applied to the diaphragm portion 10 as a compressive force perpendicularly to the (110) crystal plane 32 of the Si single crystal body 30 via the pedestal 40. By adopting a novel structure which has not been available in the past, the output electrodes 50, 50 'of the Si single crystal body 30 can be obtained.
Therefore, the voltage ΔV corresponding to the pressure P can be accurately output.

(E) Examination of other conditions The current density J ₂ of the current I flowing in the Si single crystal body 30 is
It is expressed by the following equation.

J ₂ = I / (b · h) (2) Therefore, by substituting the second equation into the first equation, the measured voltage ΔV from the Si single crystal body 30 is expressed by the following equation. You can In the equation, b represents the distance between the output electrodes 50 and 50 ', and h represents the thickness of the Si single crystal body 30.

ΔV = ρ (I / h) π ₆₃ ′ · σ _Z (3) As is apparent from the third expression, the voltage ΔV output from the force conversion element 14 used in the present invention is increased. In addition to the piezoresistance coefficient π ₆₃ ′, the specific resistance ρ of the Si single crystal body 30, the current value I / h of the Si single crystal body 10 with respect to the thickness h of the Si single crystal body 30 and the compressive stress σ _Z are determined in order to Either one should be increased.

However, in reality, the specific resistance ρ, the current I, and the compressive stress σ _Z of the Si single crystal body 30 cannot be made larger than a range beyond common sense for the reasons described below.

That is, it is difficult to manufacture the Si single crystal body 30 commercially available as a p-type or n-conduction type so as to have intrinsic characteristics in which the specific resistance ρ exceeds 1 × 10 ⁴ Ωcm.

Further, when providing a plurality of electrodes on the Si single crystal body 30, if the specific resistance ρ exceeds 10 Ωcm, it becomes difficult to obtain good electrical connection.

Furthermore, the resistivity ρ of the Si single crystal body 30 at room temperature is 1
0 Ωcm (corresponding to an impurity concentration of about 1 × 10 ¹⁵ / cm ₃ ) to 1 × 10 ⁻⁴ Ωcm (impurity concentration of about 1 × 10 ²¹
(Corresponding to / cm ₃ ) is not satisfied, the change of the measured voltage ΔV with respect to room temperature becomes extremely large.

Therefore, as the Si single crystal body 30 constituting the force conversion element of the present invention, it is preferable to use the one whose specific resistance ρ is controlled in the range of 10 Ωcm to 1 × 10 ⁻⁴ Ωcm. The Si single crystal 30 used has an impurity concentration controlled within the range of 1 × 10 ¹⁵ / cm ³ to 1 × 10 ²¹ / cm ³ .

Further, the size of the piezoresistance coefficient π ₆₃ ′ of the Si single crystal body 30 also depends on the size of the specific resistance ρ,
The range is restricted for the same reason as the specific resistance ρ.

Further, it is known that the breaking strength due to the compressive force of the Si single crystal body 30 is about 50 kg / mm ² at maximum. Therefore, the Si single crystal body 30 has a breaking strength of 50 kg / mm.
It is necessary to form so that compressive stress σ _Z exceeding ² is not applied, and the compressive stress is preferably 25 kg / mm ²
It is preferable to act as follows.

Further, it is necessary to take care so that the current value I flowing through the Si single crystal body 30 does not become excessive. this is,
If an excessive current I is passed through the Si single crystal body 30, the Si single crystal body 30 itself will remarkably generate heat as an electrical resistor, which adversely affects not only the measured voltage ΔV but also other characteristics. Is.

According to the confirmation by the present inventors, the current I is
As long as the power consumption was within the range of not exceeding about 30 mW, the characteristics were not adversely affected.

As described above, the desirable conditions for obtaining a larger measurement voltage ΔV from the Si single crystal 30 are summarized as follows.
It looks like this:

First, the impurity concentration of the Si single crystal body 30 is 1 × 10.
^It is controlled as ¹⁵ / cm ₃ to 1 × 10 ²¹ / cm ₃ .

Secondly, the compressive stress σ _Z acting on the Si single crystal body 30 is
The breaking limit of the Si single crystal body 30 is not exceeded. According to experiments, the range does not exceed 50 kg / mm ² , preferably 2
It has been confirmed that the range should not exceed 5 kg / mm ² .

Thirdly, the current I flowing through the Si single crystal body 30 is set in a range in which the Si single crystal body 30 does not remarkably generate heat. Experiments have confirmed that the power consumption of the Si single crystal body 30 may be set within a range not exceeding 30 mW.

(F) Study on Thickness h The inventors of the present invention have made it possible to satisfy the above-mentioned desirable conditions and further increase the voltage ΔV output from the Si single crystal body 30 by using the third formula. A study was conducted to reduce the thickness h shown in FIG. 1, that is, the thickness h of the Si single crystal body 30.

Generally, the Si single crystal body 30 is manufactured using a Si single crystal wafer having a diameter of 1.5 inches or more. As we all know,
The Si single crystal wafer is premised on various IC process treatments, and has a thickness of at least 2 in order to facilitate its handling.
If the wafer is manufactured to have a diameter of 5 μm or more and the wafer diameter is 5 inches, the wafer having a thickness of about 500 μm is commercially available.

Therefore, in the force conversion element of the present invention, first, a commercially available (110) plane Si single crystal wafer is cut out to obtain Si.
A single crystal body 30 is formed. And this Si single crystal body 3
The (110) crystal plane 34 of 0 is bonded to the support base 62 and backed to facilitate the handling. afterwards,
The other crystal plane 32 of the Si single crystal body 30 is polished by using a mechanical method and a chemical method in combination, and the thickness thereof is 50 μm, which is considered to be difficult to manufacture and market as a normal Si single crystal body wafer. Below.

Then, the Si single crystal body 30 is formed on the output electrode 50,
50 'and the input electrodes 52, 52' are attached, and the pedestal 40 is joined to the crystal plane 32.

In this way, the force conversion element 14 of the present invention is configured so that the thickness h of the Si single crystal body 30 is 50 μm or less,
It is possible to obtain a practically sufficiently large measurement voltage ΔV within the constraint that the desired situation for the i single crystal body 30 is satisfied.

According to the experiments by the present inventors, the impurity concentration is 1 × 10 ¹⁵
/ Cm ³ to 1 × 10 ²¹ / cm ^{3 in} a controlled range, and further, the thickness thereof is polished to h = 20 μm.
When the force conversion element 14 is formed by using
It was confirmed that the temperature had less influence on the characteristics and the measured voltage ΔV was about 10 times or more as compared with the force conversion element 14 formed by using the Si single crystal body 30 of 00 μm or more.

Therefore, according to the present invention, as described in the item (e), the impurity concentration of the Si single crystal body 30 is set to 1 × 10 5.
By controlling in the range of ¹⁵ / cm ³ to 1 × 10 ²¹ / cm ³ , it is possible to obtain a highly reliable force conversion element 14 that is less affected by ambient temperature fluctuations.

In addition to this, according to the present invention, as described in the section (f), by forming the Si single crystal body 30 so as to have a thickness of 50 μm or less, it is proportional to the compression force and practically used. It is possible to obtain a voltage output having a sufficiently large size.

(G) Further, in the present invention, the Si single crystal body 30 is cut out so that its crystal plane 32 is rectangular (including square), and is formed so that its thickness and impurity concentration are uniform. The output electrodes 50, 50 'are mounted on the Si single crystal body 30 at a predetermined interval, and the input electrodes 52, 52' are also mounted on the Si single crystal body 30 at a predetermined interval. Has been.

By providing the respective electrodes 50, 50 ', 52, 52' in this manner, 50 and 52, 52 and 50 ', 50' and 5
The resistance values between 2 ', 52' and 50 can be made equal, and since the thickness and the impurity concentration of the Si single crystal body 30 are uniform, the resistance values can be made substantially equal to the change in temperature.

Therefore, the offset voltage in the case where a current is made to flow from the input electrodes 52, 52 to the Si single crystal body 30 and a voltage output is taken out from the output electrodes 50, 50 'is substantially zero without being affected by temperature changes. Will be maintained as
One of the above-mentioned problems can be solved by replacing the single Si single crystal body 30 with the Wheatstone bridge circuit formed by using the above-described conventional plurality of semiconductor strain gauges.

[Effects of the Invention] As described above, according to the present invention, the pressure of the high temperature fluid acting on the surface of the diaphragm is perpendicular to the crystal plane of the {110} plane of the Si single crystal through the pedestal which is the transmission material. It uses a new pressure detection method that causes it to act as a compression force.

Therefore, according to the present invention, like a conventional pressure sensor,
There is no adverse effect on the properties of the adhesive and the properties of the flexure element, and the pressure of the hot fluid applied is
This is an effect that the piezoresistance effect of the Si single crystal body can be effectively used and can be accurately measured.

Particularly, according to the present invention, the impurity concentration of the Si single crystal is set to 1
By controlling in the range of × 10 ¹⁵ / cm ³ to 1 × 10 ²¹ / cm ³ , it is possible to obtain a more reliable pressure sensor that is less affected by ambient temperature fluctuations.
By setting the thickness of the single crystal body to 50 μm or less, it is possible to obtain a voltage output that is proportional to the pressure of the high temperature fluid and has a practically sufficient magnitude.

Further, according to the present invention, since the Si single crystal body has the function of the Wheatstone bridge circuit, the plurality of semiconductor strain gauges provided in the conventional force conversion element are replaced by one S
There is an effect that it is possible to obtain a pressure sensor which can be replaced with an i single crystal and which has a simple structure and is inexpensive.

Further, according to the present invention, the support base for supporting and fixing the Si single crystal body and the input / output electrode terminals respectively connected to the input / output electrodes of the Si single crystal body are integrally held and fixed by using the holding means. By forming such a stem, electrical wiring of the Si single crystal body can be easily performed by using a short conductive wire without laying a lead wire or the like. As a result, there is an effect that it is possible to obtain a highly reliable and inexpensive pressure sensor that is easy to manufacture and is less affected by noise.

[Embodiment] Next, a preferred embodiment of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 shows a first preferred embodiment in which the pressure sensor for high temperature fluid according to the present invention is used as a combustion pressure sensor for an engine.

This pressure sensor transmits the pressure P of the combustion gas acting from the front surface side of the diaphragm portion 10 to the force conversion element 14 fixed inside the sensor case 20 via the thermal insulator 12, and this force conversion element 14 Is configured to measure the pressure P of the combustion gas based on the electrical signal output from

In this embodiment, the sensor case 30 is made of a material having a high heat insulating property.

Further, in this pressure sensor, the flange portion 11a of the diaphragm portion 10 is fitted into the tip opening portion of the sensor case 20 which is formed in a substantially cylindrical shape, and the fitting portion is fitted so that combustion gas does not enter the inside of the sensor case 20. Projection welding is performed along the entire circumference.

A block portion 22 is formed at the center of the surface of the diaphragm portion 10 for the purpose of absorbing the heat of the combustion gas near the diaphragm portion 10 and absorbing the heat received by the diaphragm portion 10 itself.

In order to perform such heat absorption, the block portion 22 must have a lower temperature than the diaphragm portion 10. Therefore, the block portion 22 is required to have characteristics that the specific heat is large and the thermal conductivity is large. In addition, it is not preferable that the block portion 22 is formed so large that it does not reduce the natural frequency of the diaphragm portion 10.
In particular, when the compression force sensor of the present invention is used as a combustion pressure sensor, the weight of the block portion 22 increases,
When the natural frequency of the diaphragm portion 10 is reduced, the measurable frequency range is narrowed, and it becomes difficult to detect a knock signal or the like particularly when the diaphragm portion 10 is mounted in a place where vibration of the engine is large.

Therefore, the block portion 22 is required to have a smaller specific weight with respect to the diaphragm portion 10, and the smaller the specific weight, the better the detection characteristics.

In order to solve such a problem, in the present invention, the diaphragm portion 10 and the block portion 22 are formed separately, and the block is provided on the joining convex portion 10a provided near the central portion of the surface of the thin plate portion 11b of the diaphragm portion 10. The joining recess 22a provided in the central portion of the portion 22 is joined, and the block portion 22 is attached and fixed to the central portion of the surface of the diaphragm portion 10.

By doing so, it is possible to form using a different material for both. That is, the diaphragm portion 10 is made of a material having excellent spring characteristics at high temperature (for example, SUS43).
0, a material such as Inconel X720), and the block portion 22 can be formed using a material having a high thermal conductivity (for example, an Al-based alloy).

For example, when the block portion 22 is formed of an Al-based alloy, its mass is about 1/3 of that of a conventional case using an Fe-based or Ni-based alloy. This means that when an Al-based alloy is used, the responsiveness and acceleration sensitivity are almost the same, and the heat capacity is about 3 even when the volume is three times that of the conventional case using the Fe-based and Ni-based alloys. It means that you can double.

Furthermore, when the block portion 22 is formed using an Al-based alloy, compared to the conventional case using an Fe-Ni-based alloy,
The specific heat is about twice and the thermal conductivity is about three times.

As described above, according to the present invention, the diaphragm portion 10 has good high temperature spring characteristics, such as SUS430 and Inconel X.
By forming the block portion 22 using a material such as 720 and using, for example, an Al-based alloy, the specific heat of the block portion 22 is about twice and the thermal conductivity is about three times that of the conventional one. The specific weight can be reduced to about 1/3, and the effect can be expected to be about 18 times as large as that in the case where the block portion 22 having the same volume is integrally formed with the diaphragm portion 10.

Further, in the present embodiment, the joining convex portion 10a is formed so that the tip side does not spread forward, and the joining concave portion 22a has a size of the joining convex portion 10a so that the inside does not spread inward. It is formed according to the size. By doing so, these block parts 22
Since the diaphragm portion 10 can be easily formed by a press die, mass productivity of the pressure sensor is improved,
It is possible to reduce costs.

Further, when the block portion 22 is bonded and fixed to the surface of the diaphragm portion 10 in this manner, the surface of the diaphragm portion 10 is covered by the block portion 22 through the gap 24 almost entirely like an umbrella. At this time, the size of the gap 24 can be arbitrarily adjusted by the dimensions of the convex portion 10a and the concave portion 22a, and is formed to be almost zero in the figure. By doing so, the block portion 22 can quickly absorb the heat of the combustion gas coming near the diaphragm portion 10.

Therefore, the amount of heat directly transferred from the combustion gas to the diaphragm portion 10 is greatly reduced, and as a result, the temperature rise of the diaphragm portion 10 can be effectively suppressed, and further, the creep and the like of the diaphragm portion can be reduced.

Further, in the pressure sensor of this embodiment, the force conversion element 14
Is formed so as to have a (110) crystal face as a face to which a compressive force is applied, and the Si single crystal body 30 mounted so that the crystal face is parallel to the diaphragm 10.
And a pedestal 40 that is electrostatically bonded to the (110) crystal face of the Si single crystal body 30 and uniformly applies the compressive force transmitted through the thermal insulator 12 perpendicularly to the crystal face. It includes a stem 60 joined to another crystal plane of the single crystal body 30.

The force converting element 14 has an outer periphery on the sensor case 2
It is attached and fixed to the inner peripheral surface of 0 through the stem 60.

Further, on the crystal plane of the Si single crystal body 30, a pair of first crystal layers facing each other in the direction of 45 degrees from the <001> direction of the crystal are arranged.
Electrode (not shown) of the
A pair of second electrodes (not shown) are provided facing each other in the direction of 5 degrees. Then, one of the first and second electrodes is used as an output electrode and the other is used as an input electrode.

Further, the stem 60 is provided with two electrode terminals 64 and 64 'which can correspond to the output electrode and two electrode terminals 66 and 66' which correspond to the input electrode (fourth electrode terminal).
One end of each of the four electrode terminals is electrically connected to the corresponding input / output electrode via a gold wire 54. The other end side of each of these electrode terminals 48 is connected to a lead wire 56, and the lead wire 56 is led out from the other end side of the sensor case 20.

In the sensor of the embodiment, in order to prevent the lead wire 56 from coming off, a caulking portion 20a for the lead wire is provided on the other end side, and the pulling force applied to the lead wire 56 causes the electrode terminals 64, 64 '. , 66, 66 '. Further, the caulking portion 20a of the sensor case 20 is formed so as to be covered with a case cover 26.

Further, in the combustion pressure sensor of the embodiment, a screw groove 28 for mounting and fixing is provided on the outer peripheral portion on one end side of the sensor case 20, and the screw groove 28 is provided on the inner peripheral portion of a predetermined mounting hole (not shown). It is formed so that it can be easily attached to a desired position by being screwed into the provided thread groove.

FIG. 4 shows a detailed embodiment of the force conversion element 14 used in the pressure sensor of the present invention. FIG. 4 (A) is its plan view, and FIG. 4 (B) is its side sectional view. It is a figure.

In the present embodiment, the Si single crystal body 30 has an impurity concentration of 1 × 10 ¹⁶ / cm ³ (specific resistance ρ is about 1 Ωcm) in the range of 1 × 10 ¹⁵ / cm ³ to 1 × 10 ²¹ / cm ^3. P-type S with a size of 1.7 mm ² and a thickness of 17 μm
i is formed as a single crystal.

Then, as shown in FIG. 4 (A), a pair of output electrodes having a width of 0.1 mm is formed on one crystal plane 32 of the Si single crystal body 30 in a direction 45 degrees from the <001> direction of the crystal. Fifty,
Aluminum is vapor-deposited so that 50 'face each other, and further, a pair of input electrodes 52, 52' having a width of 0.9 mm face each other in the direction of 45 degrees from the <10> direction of the crystal. Is formed by vapor deposition.

In the embodiment, the pedestal 40 is made of crystallized glass having a size of 1 mm ² and a height of 1.1 mm.

In addition, in the present embodiment, the stem 60 is electrostatically bonded to the crystal plane 34 of the Si single crystal body 30 and supports the Si single crystal body 30. A pair of output electrode terminals 64, 6 arranged in a ring shape
4 ′, input electrode terminals 66, 66 ′, and these electrode terminals 64, 64 ′, 66, 66 ′ and the support base 62 are sealed in an outer ring 70 having a substantially cylindrical shape with an open upper end. It is formed by integrally mounting and fixing using a glass glass 68.

Here, the support base 62 is made of the Si single crystal 30.
And made of crystallized glass having a thermal expansion coefficient close to each other, and the size is 1.7 mm ² and the height is 3 mm.

The outer ring 70 is made of a Fe-Ni-Co alloy,
It is formed in a substantially cylindrical shape with one end opened, and a plurality of electrode terminal insertion holes 72 are formed in the bottom surface thereof.

The electrode terminals 64, 64 ', 66, 66' are formed in the shape of elongated rods having a diameter of 0.5 mm, and are attached so that one end side "a" thereof is substantially flush with the crystal plane 32 of the Si single crystal body 30. It is fixed. Then, the output electrode terminals 66, 6
6'is provided with a metal plating layer on its one end side a, and the metal plating layer is connected to the input electrodes 52, 52 'using a gold wire 54 having a diameter of 0.05 mm.
Further, each of the output electrode terminals 64, 64 'is similarly provided with a gold plating layer on one end side a side thereof and has a diameter of 0.05 mm.
Are connected to the output electrodes 50 and 50 ', respectively.

Also, these electrode terminals 64, 64 ', 66, 66'
Has one end side of the stem 60 through the insertion hole 72 of the outer ring 70.
, And is connected to a measuring device (not shown) via a lead wire 54 as shown in FIG.

Next, the force conversion element 14 formed in this manner applies a voltage ΔV of a magnitude sufficient for practical use to its output electrode 50,
It can be output from 50 ', and its measured voltage Δ
In order to verify that V is less affected by temperature, the following experiment was conducted.

That is, the inventors of the present invention have a power consumption of 30 at room temperature.
A current I is made to flow from the power source to the Si single crystal body 30 so as not to exceed mW, and σZ is set to 15 kg / mm ² through the pedestal 40 so that the Si single crystal body 30 is not destroyed. A compressive force was applied.

In the example, the resistance value between the pair of input electrodes 52, 52 ′ provided on the Si single crystal body 30, that is, the so-called input resistance value was 800Ω at room temperature. Therefore, the power consumption is 3
A current of I = 6 mA was applied to the Si single crystal body 30 from these input electrodes 52 and 52 'so as not to exceed 0 mW.

As a result, the output electrodes 50, 5 of the Si single crystal body 30 are
From 0 ', a voltage of ΔV = about 110 mV could be obtained at room temperature. The measured voltage ΔV is -40 ° C to 150 ° C.
The rate of change in the temperature range was 0.15% / ° C. As a result, it has been confirmed that the force conversion element 14 of the present embodiment can output a voltage ΔV of a sufficient magnitude in practical use, and the influence of the characteristics on temperature is extremely small.

By the way, in the force conversion element 14 shown in FIG.
A study was also conducted on the case where a single crystal body 30 having a thickness of 200 μm was used. At this time, the power consumption is 30
In order not to exceed mW, the input electrodes 52, 5
It is necessary to pass a current I of 2 mA from 2 ', and
If the Si single crystal body 30 having a thickness h of 200 μm is used, even if a current of 21 mA is applied from the input electrodes 52, 52 ′, the force conversion element 14 outputs about 30 mV.
It is possible to output only a voltage of a certain degree, and it is understood from this also that the force conversion element 14 of this embodiment can obtain the measured voltage ΔV having a practically sufficient magnitude. Will be done.

In addition, in the present embodiment, the case where the Si single crystal body 30 is formed as the p-conductivity type with the impurity concentration of 1 × 10 ¹⁶ / cm ³ has been described as an example, but the present invention is not limited to this, and the n-conductivity type. The same effect can be obtained by using the Si single crystal body 30.

As described above, the force conversion element 14 of the present invention has an effect of taking out the measurement voltage ΔV largely by reducing the thickness h of the Si single crystal body 30, and this effect has an impurity concentration of 1 × 10 5. ^It becomes more prominent as it increases toward ²¹ / cm ³ .

Further, in the force conversion element shown in FIG. 4, the force application point side of the pedestal 40 to which the compressive force W is applied is formed in a flat shape, but a convex curved surface is formed on the whole surface or a part of the force application point side surface of the pedestal 40. Alternatively, a concave curved surface may be provided so that the compressive force W exerted by the pressing surface of the pressing plate acts on substantially the center of the pedestal 40.

For example, as shown in FIG. 6, the surface 42 of the pedestal 40 on the force application point side may be formed into a convex curved surface shape, and the compressive force W may be applied to the pedestal 40.

Further, in the present embodiment, the case where the thermal insulator 12 is used to prevent the conduction of heat from the diaphragm portion 10 to which the pressure P is applied to the Si single crystal body 30 has been described as an example. However, the pressure measurement can be performed without using the heat insulator 12 by using the pedestal 40 as a composite pedestal having excellent heat insulating properties.

That is, one end of the pedestal 40 is bonded to the Si single crystal body 30. Therefore, the pedestal 40 is made of the Si single crystal 30.
It is preferable to use a material having a thermal expansion coefficient close to that of The other end of the pedestal 40 is in contact with the high temperature diaphragm portion 10 side. Therefore, it is preferable that the material of this portion is formed using a material having excellent mechanical strength and thermal insulation. Therefore, the Si single crystal body 3 of the pedestal 40 is
0 is formed by using an electrically insulating material having a thermal expansion coefficient close to that of the Si single crystal body 30, and a portion of the pedestal 40 which is in contact with the diaphragm portion 10 side is connected to the Si single crystal body 30. It may be formed by using a material having a mechanical strength or a heat insulating property superior to that of the joint portion.

Thus, by forming the pedestal 40 itself as a composite pedestal using two kinds of materials, for example, when it is attempted to measure a high temperature / high pressure fluid pressure such as combustion gas in a cylinder of an internal combustion engine, the diaphragm portion is The heat transferred to 10 is relaxed and blocked by the pedestal 40, and does not act on the Si single crystal body 30 as a high temperature. Therefore, the Si single crystal body 30 can output a voltage corresponding to the pressure P applied to the diaphragm portion 10 without being affected by the ambient environmental temperature.

Further, a compressive force may locally act on a portion of the pedestal 40 that is in contact with the diaphragm portion 10 side, such as a single contact, depending on the state of the joint surface. In such cases,
The pedestal 40 may be plastically deformed or destroyed.
However, as described above, by using a material having excellent mechanical strength for this portion of the pedestal, the diaphragm portion 10
Even if the joint portion between the side and the pedestal 40 is in one-sided contact or the like, the pedestal 40 is not destroyed, so that the pressure P can be measured well.

The present invention is not limited to the above embodiment,
Various modifications are possible within the scope of the invention.

Second Embodiment FIG. 7 shows another embodiment of the force conversion element 14 used in the present invention.

The force conversion element 14 of the embodiment is formed by heat-treating the semiconductor layer 36 made of Si having a (110) crystal face of 1.7 mm ² and a thickness of 200 μm and the side surface of the semiconductor layer 36 at a high temperature. The electrically insulating film 37 made of SiO 2 having a thickness of 1 μm and the (110) plane formed on the main surface 37 a of the insulating film 37 by epitaxial growth to have a thickness h = 1 μm. And a Si single crystal body 30. The pedestal 40 is electrostatically bonded to the crystal plane 32 of the Si single crystal 30, and the support base 62 is electrostatically bonded to the surface of the semiconductor layer 36 opposite to the surface on which the insulating film 37 is provided. ing.

Here, the Si single crystal body 30 has an impurity concentration of 1 × 10 ¹⁹ / cm ³ to 1 × 10 ²¹ / cm ^{3 in} a range of 1 × 10 ¹⁹ / cm ³ (specific resistance ρ of about 0. 0.01 Ωc
m), boron is thermally diffused as p-conductivity type.

An insulating film 37 is formed on the semiconductor layer 36, and the impurity concentration of the Si single crystal body 30 is 1 × 10 ¹⁹ / cm ^3.
A series of steps by the IC manufacturing process technology, such as controlling by, is actually performed at the wafer manufacturing stage. Then, the wafer was diced with a dicer as shown in FIG.
Cut out as 7 mm ² .

Next, with respect to the force conversion element thus formed, the present inventors apply a current I to the Si single crystal body 30 within the range in which the power consumption at room temperature does not exceed 30 mW in the same manner as in the first embodiment. It was confirmed that the Si single crystal body 10 was thinned by applying a compressing force of 15 kgw while flowing, and that the effect of temperature fluctuation on the characteristics was small.

As a result, the measured voltage ΔV of the Si single crystal body 10 is about 25 mV at room temperature, and the measured voltage ΔV is −40.
The change rate in the range of ° to 150 ° is -0.23% /
It was ℃.

From this, it was confirmed that the force conversion element 14 of the example can output a sufficiently large voltage ΔV in practical use, and that the influence of the temperature of the measured voltage V is extremely small.

Furthermore, the force conversion element 14 of the present embodiment is the Si single crystal body 3
Since 0 is formed on the main surface 37a of the electrically insulating film 37, there is no current leakage even at high temperatures, and the reliability is high.

In the present embodiment, the case where the Si single crystal body 30 is formed as the p-conduction type has been described as an example, but the present invention is not limited to this, and the silicon single crystal body 30 is formed as the n-conduction type. There is no problem at all.

Further, in the present embodiment, the case where the Si single crystal body 30 having the (110) plane is formed by the epitaxial growth method has been described as an example, but the present invention is not limited to this and, for example, C
The VD method or the MBE growth method may be used in combination with the laser recrystallization technique or the like.

Third Embodiment FIG. 8 shows another embodiment of the force conversion element 14 used in the present invention.

In this embodiment, the Si single crystal body 30 has a crystal plane (1
10) The surface is of p-conductivity type and its thickness is h = 200μ.
It is formed as that of m. The Si single crystal 30 has a thickness h = 2 μm formed by thermally diffusing boron so that the impurity concentration becomes 5 × 10 ¹⁸ / cm ³ (specific resistance is about 2 × 10 ⁻² Ωcm). It is formed so as to include a p-conductivity-type compressive force sensing conductive layer 38 and an insulating separation layer 39 that electrically insulates and separates the conductive layer 38 so that the conductive layer 38 functions with at least 1% accuracy.

Further, in the Si single crystal body 30, the resistance value of the current path flowing in the conductive layer 38 from the input electrode 52 toward the opposite input electrode 52 ′ is the same as the current path flowing in the electrically insulating separation layer 39. The impurity concentration is controlled so as to be at least 1/100 or less of the resistance value of.

The Si single crystal body 30 has one crystal plane 3
The pedestal 40 is electrostatically bonded to the second side, and the support base 62 is electrostatically bonded to the other crystal surface 34.

In the embodiment, the input electrodes 52 and 58 'and the output electrodes 50 and 50' are both electrically connected to at least the conductive layer 38 in order to take out the measured voltage ΔV based on the piezoresistive effect of the conductive layer 38. It is formed by vapor deposition.

With respect to the force conversion element 14 formed in this way, the present inventors, like the above-mentioned respective examples, flow a current I through the Si single crystal body 30 within a range in which the power consumption at room temperature does not exceed 30 mW, The effect of thinning the Si single crystal body and the effect that the temperature fluctuation has little influence on the characteristics were confirmed.

As a result, by reducing the thickness of the conductive layer 38 to h = 2 μm, it is possible to obtain a measurement voltage ΔV that is about 10 times that of the case where the thickness of the conductive layer 38 is 200 μm.
Further, the conductive layer 22 is provided so as to have a self-sensitivity guaranteeing function (a function disclosed in Japanese Patent Publication No. 57-58791, which suppresses fluctuation of the measurement voltage ΔV with temperature).
Impurity concentration (for example, about 5 for P-conductivity-type Si single crystal)
Two impurity concentration regions of × 10 ¹⁸ / cm ³ and about 2 × 10 ²⁰ / cm ³ exist as regions to which the self-sensitivity compensation method can be applied), so that the temperature of −40 ° C. to 150 ° C. It was confirmed that the change of the measured voltage ΔV in the range was almost zero.

In the present embodiment, the Si single crystal body 30 that also serves as the conductive layer 38 and the electrically insulating separation layer 39 is described as being of the p-conduction type resistance separation method, but the present invention is not limited to this. Alternatively, a force conversion element having substantially the same effect can be formed by using the resistance separation method of n-conduction type.

In addition, in the present embodiment, the Si single crystal body 30 which also serves as the electrical insulation separation layer 28 is provided with intrinsic characteristics with few carriers controlled so that the donor and the acceptor are neutralized. And the conductive layer 38 is p
It may be formed of either a conductivity type or an n conductivity type.

The conductive layer 38 and the electrically insulating separation layer 39 are
There is no problem even if it is formed by using the -n junction isolation method. However, when the pn junction separation method is used, the output power is 5
0, 50 'and the input electrodes 58, 52' must be formed so as to make an electrical connection only with the conductive layer 38,
Electrical isolation using the pn junction isolation method is essentially 1
It is well known that the electrical separation function is provided only in the temperature range up to about 50 ° C.

Fourth Embodiment FIG. 9 shows another embodiment of the pressure sensor according to the present invention.

The feature of this embodiment is that the thin plate portion 1 of the diaphragm portion 10 is
Provide a screw hole 80 on the surface of 1b in the direction of pressure application,
The purpose is to deform the thin plate portion 11b in the pressure applying direction by using the adjusting screw 82 screwed into the screw hole 80 to give a desired preload to the force conversion element 14.

In this embodiment, the screw hole 80 is provided from the block portion 22 toward the central portion of the surface of the thin plate portion 11b.

The adjusting screw 82 is composed of a head portion 84 provided with an engaging groove 84a for engaging with the tip of the driver and a screw portion 86 into which the screw hole 80 is screwed, and the screw portion 86 has a threaded tip. It is formed in a mold, and the thin plate portion 11 is formed at the center of its tip.
It is formed so as to effectively press and deform the surface central portion 100 of b.

Further, the diaphragm portion 10 needs to be formed such that the thin plate portion 11b is deformed to the right in the drawing by the pressing force of the adjusting screw 82, and the screw hole 80 penetrates to the back surface side of the thin plate portion 11b. Be careful not to.

Then, in the present embodiment, in the case of applying a preload to the force conversion element 14 using the adjustment screw 82 formed in this way, first, while adjusting the output of the force conversion element 14, the adjustment screw 82 is tightened. This allows the adjustment screw 8
The tip of 2 presses the central portion 100 of the thin plate portion 11b of the diaphragm portion 10. Then, the central portion 10 of the thin plate portion 11b
0 deforms to the right in the figure, and preloads the force conversion element 14 via the thermal insulator 12.

At this time, since the electric signal corresponding to the preload is output from the force conversion element 14, the adjuster sets the preload value as follows while watching the electric signal.

That is, each component of the pressure sensor usually has a certain dimensional error, and an assembling error occurs when assembling each component. For example, the diaphragm portion 10 may be attached to the sensor case 2
In the case of projection welding to 0 and sealing and fixing, the diaphragm portion 10 is displaced in the pressure applying direction by an amount corresponding to the protruding height (about 0.2 mm) of the weld portion. Therefore, during welding for assembling the pressure sensor, the sensor case 2
When the diaphragm portion 10 comes into contact with the force conversion element 14 fixed in 0, an impact force acts on the force conversion element 14 and there is a risk that the element 14 is destroyed.
For this reason, it is preferable that the force conversion element 14 is slowly preloaded after the assembly is completed, especially after the diaphragm portion 10 is projection-welded to the sensor case 20.

At this time, the diaphragm portion 10 and the sensor case 20 are prevented from expanding and contracting due to heat so that the pressure is not applied to the force conversion element 14 from the diaphragm portion 10, and moreover, the negative pressure acting on the surface of the diaphragm portion 10 is accurately measured. The preload value must be set to a value equal to or higher than a predetermined lower limit value so that it can be detected.

Further, this preload value must be set to a value equal to or less than a predetermined upper limit value so that the force conversion element 14 will not cause fatigue failure when repeatedly measuring pressure using a pressure sensor.

Therefore, in the pressure sensor of the present embodiment, the preload value is adjusted by using the adjusting screw 82 so that it exists between the lower limit value and the upper limit value.

Then, when the adjustment of the preload is completed, the adjusting screw 82 is cut from the position shown by the one-dot chain line AA ′ in the drawing to reduce the additional mass of the diaphragm portion 10,
Improve its seismic performance.

That is, the adjusting screw 82 is attached to the screw hole 80 provided in the diaphragm portion 10. For this reason, if the mass of the adjusting screw 82 is increased, the natural frequency of the diaphragm portion 10 is lowered, and its vibration resistance is lowered. Therefore, if such a combustion pressure sensor is attached to a portion of the engine or the like where vibration is great, the pressure detection accuracy is greatly reduced. Therefore, in this embodiment, after the adjustment of the preload by the adjustment screw 82 is completed, the adjustment screw 82 is
By cutting off the head portion 84, the seismic resistance of the combustion pressure sensor is not deteriorated.

As described above, according to the present embodiment, a desired preload is simply applied to the force conversion element 14 via the diaphragm portion 10, and the negative pressure changes from the negative pressure to the positive pressure without being affected by the ambient temperature change. It is possible to obtain a pressure sensor that can accurately measure even a pressure, and particularly can accurately measure a high temperature fluid pressure.

Further, in each of the above-described embodiments, the case where the force conversion element is formed by using the Si single crystal having the (110) crystal face has been described as an example, but the present invention is not limited to this, and the first As shown in the table, the force conversion element may be formed using a Si single crystal body having a {110} crystal plane equivalent to the (110) plane.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a preferred example when the pressure sensor according to the present invention is formed as a combustion pressure sensor, FIG. 2 is an explanatory view of a conventional pressure sensor, and FIG. 3 is used for a conventional pressure sensor. FIG. 4 is a perspective view of the force conversion element, FIG. 4 is an explanatory view showing a preferred example of the force conversion element used in the pressure sensor of the present invention, FIG. A side view thereof, FIG. 5 is a characteristic diagram of a piezoresistance coefficient π ₆₃ ′ of a p-type (110) plane Si single crystal having a specific resistance of 7.8 Ωcm, and FIG. 6 is a modification of the force conversion element shown in FIG. FIGS. 7 and 8 are explanatory views showing another embodiment of the force conversion element, and FIG. 9 is an explanatory view showing another embodiment of the pressure sensor according to the present invention. 10 ... Diaphragm section 14 ... Force conversion element 22 ... Block section 30 ... Si single crystal 32, 34 ... Crystal plane 40 ... Pedestal 50, 50 '... Output electrode 52, 52' ... Input electrode 60 ... Stem 62 ... Support base 64, 64 '... Output electrode terminal 66, 66' ... Input electrode 68 ... Sealing glass 70 ... Outer ring 80 ... Screw groove 82 ... Adjusting screw

Front Page Continuation (72) Inventor Sadayuki Hayashi, Nagakute-cho, Aichi-gun, Aichi 1-41 Yokomichi, Nakamichi Toyota Central Research Institute Co., Ltd. (56) Reference JP 63-88418 (JP, A) 52-63083 (JP, A) JP-A-53-42579 (JP, A)

Claims (4)

[Claims] 1. A pressure sensor for transmitting a pressure of a high temperature fluid acting on a surface of a diaphragm portion to a force conversion element as a compression force and measuring the pressure of the high temperature fluid based on an electric signal output from the force conversion element, The force conversion element is formed to have a {110} crystal face as a face to which a compressive force is applied, and a Si single crystal body attached so that the crystal face is parallel to the diaphragm portion. A first electrode provided on a single crystal body facing the <001> direction of the crystal on the {110} plane in the direction of 45 degrees and a first electrode facing the <110> direction in the direction of 45 degrees. A plurality of electrodes each including one of the first and second electrodes as an output electrode and the other as an input electrode, and one end of the {110} plane of the Si single crystal body. And the crystal plane of It is bonded so that the other end is in contact with the diaphragm part, and the pressure applied to the diaphragm part is used as a compression force S
A composite pedestal that is transmitted perpendicularly to the crystal plane of the i single crystal and is joined to the {110} plane of the Si single crystal, and a surface of the Si single crystal that faces the surface to which the pedestal is joined. A stem that is joined to the stem, the stem is joined to a surface facing a surface to which the pedestal of the Si single crystal body is joined, and a support base for supporting the Si single crystal body; A plurality of output electrode terminals for extracting an electric signal output from the output electrode to the outside, a plurality of input electrode terminals for supplying a current to the input electrode from the outside, and the input electrode terminal, the output electrode terminal and the support Holding means for integrally holding the base, and applying a compressive force perpendicularly to the crystal plane of the Si single crystal body while applying a current from the input electrode terminal to the Si single crystal body, and from the output electrode terminal to the diaphragm. Temperature acting on the surface of the part Pressure sensors for high temperature fluid and outputs a voltage corresponding to the pressure of the body. 2. The sensor according to claim 1, wherein the joining recess provided in the block having a large heat capacity is provided.
A pressure sensor for high-temperature fluid, characterized in that it is joined to a joining projection provided near the center of the surface of the diaphragm portion, and the block portion is attached and fixed to the surface of the diaphragm portion. 3. The sensor according to any one of claims (1) and (2), wherein an adjusting screw is screwed into a screw hole provided on the surface of the diaphragm in the pressure application direction, and the adjusting screw is screwed into the screw hole. A pressure sensor for high-temperature fluid, characterized in that the diaphragm portion is deformed in the direction of pressure application by using, and the compression force applied in advance to the force conversion element is adjusted. 4. The sensor according to any one of claims (1) to (3), wherein the Si single crystal body has an impurity concentration of 1 × 10 ¹⁵ / cm ³ to 1 × 10 ²¹ / cm ^3. A pressure sensor for a high temperature fluid, which is controlled to have a thickness of 50 μm or less.