JPH11118639A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor pressure sensor for inhibiting influence to performance of an internal combustion engine by preventing dew formation or freezing of a sensor element even in the case of high humidity of the air to be measured, and always accurately measuring pressure. SOLUTION: The semiconductor pressure sensor comprises a sensor element 1 having a pressure introducing tube 1a, a printed board 3 having the element 1 mounted via leads 1d isolated at a predetermined distance thereon, and a base 4 having a pressure passage 4a for holding the board 3 and a pressure introducing tube 1a inserted into the passage 4a. In this case, a distance isolated between the element 1 and the board 3 is set so that temperature dropping velocity of the element 1 at the time of at least cold radiating becomes smaller than temperature dropping velocity of the passage 4a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor used for detecting an intake pressure of an internal combustion engine or detecting an atmospheric pressure.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a configuration diagram of a conventional semiconductor pressure sensor disclosed in Japanese Unexamined Patent Publication (Kokai) Publication. In the figure, 1 is a sensor element enclosed in a metal case, and 2 is a hybrid IC (hereinafter, referred to as HIC) constituting an electronic circuit for amplifying the output of the sensor element 1.
The sensor element 1 and the HIC 2 are mounted on a printed board 3 by respective leads, and electronic components (not shown) are mounted on the printed board 3.
Reference numeral 4 denotes a base which holds the printed circuit board 3 and has a pressure passage 4a into which the pressure introducing pipe 1a of the sensor element 1 is inserted, and 5 is fixed to the base 4 via an O-ring 6 and a pressure passage 4a of the base 4 Having a pressure passage 5a communicating with the connector, for example, a cap attached to an intake port of an internal combustion engine (not shown), 7 is a metal cover for covering the sensor element 1 and the HIC 2, 8 is integrated with a connector 9 having a terminal 9a formed by insert molding. The housing 8 is fixed to the base 4, and the housing 8 and the base 4
The sensor element 1 and the like are accommodated in a space 8a formed between the sensor element 1 and the sensor element 1. 10 is the pressure passages 4a and 5a and the pressure introduction pipe 1
a sealing body such as an O-ring for sealing a from atmospheric pressure, 11
Is a holder for holding the sealing body 10.

In the semiconductor pressure sensor constructed as described above, for example, a negative pressure generated at the intake port of the internal combustion engine is applied to the pressure passages 5a and 4a of the cap 5 and the base 4.
Is applied to the sensor element 1 via the pressure introducing pipe 1a, and the negative pressure value is converted into an electric signal by the sensor element 1 and output. The output signal of the sensor element 1 is amplified by the HIC 2, subjected to temperature compensation by an electronic circuit of the printed circuit board 3, output to a control device (not shown) via a terminal 9a, and used for controlling the internal combustion engine.

[0004]

In the conventional semiconductor pressure sensor constructed as described above, the air to be measured flows into the sensor element 1 through the pressure introducing pipe 1a and the pressure passages 4a and 5a. However, the air to be measured is the intake air of the internal combustion engine or the outside air such as the atmosphere, and when these are in high humidity, the inside of the sensor element 1 and each pressure passage is filled with high humidity air. In such cases, when the ambient temperature decreases, the residual humidity condenses, and when the temperature further decreases, it freezes. Since the sensor element 1 made of a metal component such as silicon has a higher thermal conductivity and a higher cooling rate than the pressure passages 4a and 5a of the base 4 and the cap 5 which are synthetic resin components, dew condensation and freezing occur in the sensor element 1. The dew condensation or freezing in the sensor element 1 causes an error in pressure detection, and has a problem that various characteristics of the internal combustion engine controlled by the pressure value fluctuate.

The present invention has been made to solve such a problem, and prevents dew condensation and freezing in the sensor element 1 even when the air to be measured has a high humidity, so that the pressure measurement is always performed with high accuracy. It is an object of the present invention to obtain an excellent semiconductor pressure sensor that does not affect the performance of an internal combustion engine.

[0006]

A semiconductor pressure sensor according to the present invention comprises a sensor element having a pressure introducing pipe, a printed circuit board supporting the sensor element at a predetermined distance, and holding the printed circuit board and the sensor element. A base having a pressure passage into which the pressure introducing pipe is inserted, and the sensor element and the printed circuit board such that the temperature decrease rate of the sensor element during natural cooling is smaller than the temperature decrease rate of the pressure passage of the base. The distance between them is set.

A sensor element having a pressure introducing tube, a printed circuit board supporting the sensor element, a base holding the printed circuit board, and a pressure passage supported by the base and into which the pressure introducing tube of the sensor element is inserted. A nipple is provided, and the nipple is made of a material having higher thermal conductivity than the base. Further, an inner surface is inscribed in the pressure introducing pipe, and an end surface is arranged in contact with the power supply pattern of the printed circuit board, and a conductive heating element having a predetermined resistance value is provided.

Further, the inner surface of the heated body is inscribed in the pressure introducing pipe,
The end face is placed in contact with the power supply pattern of the printed circuit board,
It is provided with a conductive heating element having a predetermined resistance value. The heating element is a holder that holds a sealing element that seals between the pressure passage and the atmosphere. Further, a resistor is interposed between the heating element and the pressure introducing pipe.

The heating element is an insulating material whose surface is plated with a conductive material. The heating element is an insulating material having a surface coated with a conductive material. The heating body is a conductive elastic body.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 shows a configuration of a semiconductor pressure sensor according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes a sensor element. The sensor element 1 has a conversion element for converting pressure into an electric signal and an amplifier circuit housed in a housing portion formed by a cap 1b and a stem 1c, and is connected to an external circuit by a lead 1d. Pressure introducing pipe 1a for introducing pressure to the conversion element
Is provided. Reference numeral 3 denotes a printed circuit board on which an electronic circuit such as a temperature compensation circuit and the sensor element 1 are mounted. The sensor element 1 is printed on a printed circuit board by leads 1d so that the stem 1c and the printed circuit board 3 are separated by a predetermined distance. 3 is attached. 4 has a pressure passage 4a, which holds the printed circuit board 3 and has a sensor element 1 in the pressure passage 4a.
A pressure-introducing pipe 1a is inserted into the base, and the base 8 is attached to, for example, an intake port of an internal combustion engine. Reference numeral 8 denotes a housing integrated with a connector 9 having a terminal 9a formed by insert molding. The housing 8 is fixed to the base 4. The sensor element 1 and the printed circuit board 3 are placed in a space 8a formed therebetween.
Is stored. Reference numeral 10 denotes a sealing body such as an O-ring that is inserted between the pressure introducing pipe 1a and the base 4 and shuts off the air to be measured in the pressure introducing pipe 1a and the pressure passage 4a from the atmospheric pressure.
Reference numeral 1 denotes a holder that is interposed between the printed board 3 and the base 4 and fixes the O-ring 10.

As for the spatial distance separating the stem 1c of the sensor element 1 and the printed circuit board 3, the larger the distance, the lower the thermal conductivity between the sensor element 1 and the printed circuit board 3 becomes. The cooling rate becomes slower. In this embodiment, at least when the semiconductor pressure sensor is allowed to cool naturally with the semiconductor pressure sensor attached to the internal combustion engine, the base 4
Is set so that the cooling rate of the sensor element 1 is lower than the cooling rate of the inner surface of the pressure passage 4a. As the base 4 of the semiconductor pressure sensor, a synthetic resin molded product such as poly-butylene-terephthalate is usually used. The thermal conductivity of these materials is 0.3 W / m · K, whereas the thermal conductivity of the material is 0.3 W / m · K. The thermal conductivity is 0.degree.
Since it is extremely small at 02 W / m · K, even if there is heat conduction by the metal lead 1 d connecting the sensor element 1 and the printed circuit board 3, the spatial distance separating the stem 1 c of the sensor element 1 and the printed circuit board 3 can be reduced. By setting it to a predetermined value or more, the heat radiation speed of the sensor element 1 is reduced
Can be made slower than the heat radiation speed.

In the semiconductor pressure sensor according to the first embodiment of the present invention configured as described above, the temperature of each part of the semiconductor pressure sensor rises to a certain value during the operation of the internal combustion engine, and the temperature of each part after the operation is stopped. Is lowered, the temperature of the conversion element inside the sensor element 1 and the temperature of the pressure introducing pipe 1a are kept higher than the temperature of the pressure passage 4a of the base 4,
The humidity in the air remaining in the conversion element section, the pressure introducing pipe 1a, and the pressure passage 4a in the sensor element 1 promotes dew condensation in the pressure passage 4a, and the humidity in the residual air decreases with the dew. In addition, dew condensation and freezing in the pressure introducing pipe 1a and the conversion element section inside the sensor element 1 can be greatly reduced, and an error in pressure detection can be avoided.

Embodiment 2 FIG. FIG. 2 shows a configuration of a semiconductor pressure sensor according to Embodiment 2 of the present invention. In this embodiment, the pressure passage portion is separated from the base and is constituted by another member having good heat conduction. In the figure, 1
A nipple 2 has a pressure passage 12a and is formed of a metal material or a synthetic resin mixed with a high heat conductive material as a filler. The nipple 12 is fitted to the inner diameter 13a of the base 13, and is bonded or thermally welded. Is fixed by The pressure introducing pipe 1a of the sensor element 1 is a nipple 12
Of the sealing body 1 such as an O-ring
Numeral 0 is provided between the inner diameter 13a of the base 13, the nipple 12, and the pressure introducing pipe 1a, and shuts off the measured air from the atmospheric pressure.

In the semiconductor pressure sensor of the second embodiment configured as described above, since the heat conductivity of the nipple 12 having the pressure passage 12a is large, the heat radiation speed of the pressure passage 12a is increased, and the operation of the internal combustion engine is performed. After the stop, the temperature of the pressure introducing pipe 1a of the sensor element 1 and the temperature of the conversion element can be kept higher than that of the pressure passage 12a, and the condensation and freezing of the humidity in the residual air are concentrated in the pressure passage 12a. And dew condensation and freezing in the conversion element portion inside the sensor element 1 can be greatly reduced, so that an error does not occur in pressure detection and a highly reliable semiconductor pressure sensor can be obtained. When the thermal conductivity is relatively high, such as when the nipple 12 is made of metal, the setting of the distance between the sensor element 1 and the printed circuit board 3 described in the first embodiment is reduced or eliminated. You can do it.

Embodiment 3 3 and 4 show a configuration of a third embodiment of the present invention. FIG.
FIG. 4 is a plan view of the printed circuit board. In this embodiment, the holder 11 for fixing the sealing body 10 such as an O-ring is made of a conductor having a predetermined specific resistance value, and the inner surface thereof is formed on the outer surface of the pressure introducing pipe 1a of the sensor element 1. The upper surface is in contact with the wiring pattern 3 of the printed circuit board 3
a, and the holder 11 is configured as a heating element for the pressure introducing pipe 1a. The wiring pattern 3a of the printed circuit board 3 in FIG. 4 is connected to a power supply line, and is configured to be energized for a predetermined time even after the operation of the internal combustion engine is stopped. The pressure introducing pipe 1a of the sensor element 1 is connected to an earth line in the sensor element 1.

In the semiconductor pressure sensor of the third embodiment configured as described above, heat due to ohmic loss is generated in the holder 11 to heat the pressure introduction pipe 1a, and the pressure introduction pipe 1a is heated.
Since a is made of metal having good heat conduction, it is also thermally conducted to the conversion element portion in the sensor element 1, and this heating continues for a predetermined time after the operation of the internal combustion engine is stopped. The pressure introduction pipe 1a is maintained at a higher temperature than the pressure passage 4a, and the dew and freezing of the humidity in the residual air concentrate on the pressure passage 4a. Freezing can be significantly reduced.
In FIG. 3, the holder 11 is a normal conductor,
The same effect can be obtained by interposing the resistor 12 between the holder 11 and the pressure introducing pipe 1a. The same effect can be obtained by forming the holder 11 from an insulating resin molded product and plating the outer surface of the holder 11 with a conductive material, or applying a coating with a conductive paint. Further, the holder 11 is made of conductive rubber or the like.
It can also be constituted by an elastic body having conductivity.

Embodiment 4 FIG. 5 shows a configuration of a semiconductor pressure sensor according to a fourth embodiment of the present invention. This embodiment is different from the second embodiment shown in FIG. Inner surface is sensor element 1
Of the conductive heating element 14 whose upper surface contacts the wiring pattern of the power supply line of the printed circuit board 3.
Is provided. With such a configuration, dew condensation and freezing in the sensor element 1 can be completely prevented by the heat radiation effect of the nipple 12 and the heating effect of the pressure introduction pipe 1a, and a semiconductor pressure sensor free from malfunction can be obtained. It is. Also in this embodiment, the third embodiment
Similarly to the above, the heating element 14 is a conductor and a resistor is interposed between the heating element 14 and the pressure introducing tube 1a, or the heating element 14 is formed of a conductive elastic body or a conductive plated or coated insulator. be able to.

Fifth Embodiment FIG. 6 shows a configuration of a semiconductor pressure sensor according to a fifth embodiment of the present invention. In this embodiment, the heating element 14 is provided with a predetermined conductivity such as a conductive rubber. Is mounted in a compressed state between the printed circuit board 3, the base 4, and the pressure introducing pipe 1a, and the same wiring pattern as that of the third embodiment is provided on the printed circuit board 3. Thus, the heater 14 is energized for a predetermined time even after the operation of the internal combustion engine is stopped. With this configuration, the pressure introduction pipe 1a is heated even after the operation of the internal combustion engine is stopped, preventing dew condensation and freezing in the sensor element 1, and without using a sealing body such as an O-ring. In addition, it is possible to seal the passage of the air to be measured from the outside air by the heating element 14 and to reduce the number of parts.

[0019]

As described above, according to the present invention, the sensor element is mounted at a predetermined distance from the printed circuit board, and the pressure introducing pipe of the sensor element is heated for a predetermined time after the internal combustion engine is stopped. Further, since the pressure passage of the base is made of a heat conductive material, the sensor element and the pressure introduction pipe are kept at a higher temperature than the pressure passage when the engine is stopped, and the pressure passage, the pressure introduction pipe, and the pressure are electrically controlled. The humidity of the introduced air, which is introduced into the converter that converts the signal, is first condensed in a low-temperature pressure passage, which lowers the humidity of the introduced air and prevents dew condensation and freezing in the pressure inlet pipe and the converter of the sensor element It is possible to obtain an excellent semiconductor pressure sensor that does not cause a decrease in pressure detection accuracy or a malfunction even at a low temperature operation such as when the internal combustion engine is restarted. That.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a semiconductor pressure sensor according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view showing a configuration of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a semiconductor pressure sensor according to Embodiment 3 of the present invention.

FIG. 4 is a plan view of a printed circuit board used in Embodiments 3 to 5 of the present invention.

FIG. 5 is a sectional view showing a configuration of a semiconductor pressure sensor according to Embodiment 4 of the present invention.

FIG. 6 is a sectional view showing a configuration of a semiconductor pressure sensor according to a fifth embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a conventional semiconductor pressure sensor.

[Explanation of symbols]

1 sensor element, 1a pressure introduction pipe, 1b cap,
1c stem, 1d lead, 3 printed circuit board, 4
Base, 4a pressure passage, 8 housing, 9 connector, 10 sealing body, 11 holder.

Claims (9)

[Claims] 1. A sensor element having a pressure introducing tube, a printed circuit board supporting the sensor element at a predetermined distance, and a base holding the printed circuit board and having a pressure passage into which the pressure introducing tube of the sensor element is inserted. Wherein the separation distance between the sensor element and the printed circuit board is set such that the temperature decrease rate of the sensor element during natural cooling is smaller than the temperature decrease rate of the pressure passage of the base. Semiconductor pressure sensor. 2. A sensor element having a pressure introducing tube, a printed circuit board supporting the sensor element, a base holding the printed circuit board, and a pressure passage supported by the base and into which the pressure introducing tube of the sensor element is inserted. A semiconductor pressure sensor comprising a nipple, wherein the nipple is made of a material having higher thermal conductivity than the base. 3. A conductive heating element having an inner surface in contact with the pressure introducing pipe and an end surface in contact with the power supply pattern of the printed circuit board, and having a predetermined resistance value. The semiconductor pressure sensor according to claim 2. 4. The semiconductor pressure sensor according to claim 3, wherein the heating body is a holder for holding a sealing body for sealing between the pressure passage and the atmosphere. 5. The semiconductor pressure sensor according to claim 3, wherein the heating element is a sealing element that seals between the pressure passage and the atmosphere. 6. The semiconductor pressure sensor according to claim 3, wherein a resistor is interposed between the heating element and the pressure introducing pipe. 7. The heating element is an insulating material having a surface plated with a conductive material.
The semiconductor pressure sensor according to claim 6. 8. The semiconductor pressure sensor according to claim 3, wherein the heating element is an insulating material whose surface is coated with a conductive material. 9. The semiconductor pressure sensor according to claim 3, wherein the heating body is a conductive elastic body.