JPH07294355A - Pressure sensor - Google Patents

Abstract

PURPOSE:To prevent the destruction of pressure sensing element due.to adhesion of dust, mad, water, etc., to the pressure sensing element, prevent the lowering of measuring accuracy and prevent the discharge of measured pressure medium to the air. CONSTITUTION:The pressure sensor consists of a header 11, a measured pressure-introducing pipe 12, a pedestal 14, a pressure sensing element 15 and a cap 19. The cap 19 is made of a material disturbing the transmission of water, mad, dust, etc., and transmitting only air. Concretely, porous tetrafluoroethylene resin material is used. For the cap 19, permeable and water absorptive diaphragm or permeable and water absorptive sheet can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for measuring relative pressure with respect to atmospheric pressure, preventing dirty air and moisture from entering the pressure sensor and adhering to a pressure sensitive element, and introducing the atmosphere. The present invention relates to a pressure sensor in which the mouth is prevented from being clogged with dust or mud, and, conversely, the measurement pressure medium is released into the atmosphere as much as possible.

[0002]

2. Description of the Related Art Conventionally, in order to prevent the release of automobile fuel into the atmosphere, there has been a small pressure sensor which detects the leakage of gasoline gas into the atmosphere by detecting the pressure in the gasoline tank. Being developed. The pressure change of this slight pressure sensor is a minute amount of about -5 to +5 KPa. Further, it is optimal that the reference pressure is atmospheric pressure. When the pressure sensor is used in such an environment with a lot of dust, dust, water, mud, etc., it is necessary to devise introduction of the atmosphere.

On the other hand, regarding the pressure sensor, the actual construction of Sho 61-
No. 158836, No. 59-15943,
Japanese Utility Model Publication No. 57-194041, Japanese Utility Model Publication No. 1-1464.
The sensors disclosed in Japanese Patent Laid-Open No. 40 and Japanese Patent Laid-Open No. 59-224534 are known. All of these sensors are provided with a filter in the introduction path for introducing the measurement pressure.

[0004]

Even if these filters are provided in the introduction path for introducing the atmosphere, when the pressure sensor is installed in an automobile, dust, dirt, mud,
The filter is clogged by the intrusion of water or the like, and it is impossible to accurately detect the minute differential pressure. When the pressure-sensitive element is destroyed, the measuring pressure medium may leak into the atmosphere.

The present invention has been made to solve the above problems, and an object thereof is to enable accurate detection of a minute differential pressure without causing clogging, and also to prevent dust, dust,
When the atmosphere is introduced into the pressure sensor from an environment with a lot of mud, water, etc., do not destroy the pressure sensitive element due to dust or mud adhering to the pressure sensitive element, and the measured pressure medium is released into the atmosphere. It is to prevent being done.

[0006]

According to a first aspect of the present invention, there is provided a base, a pressure sensitive element disposed on the base so as to receive an atmospheric pressure on one end face and a measurement pressure on the other end face, and a base. In a pressure sensor consisting of a cap that covers the pressure-sensitive element and the base from the end surface side that engages with the base and receives the atmospheric pressure of the pressure-sensitive element, the cap is made of a material that has air permeability and blocks the passage of moisture. Is characterized by.

The invention of claim 2 is characterized in that the surface of the cap is covered with a metal net in the form of a wire mesh.

According to a third aspect of the present invention, in the first aspect of the invention, the base is connected to the measurement pressure introducing pipe for introducing the measurement pressure and the pressure sensing element connected to the inlet and outlet of the measurement pressure introducing pipe. It is characterized in that the joint between the measuring pressure introducing pipe and the pedestal and the joint between the pedestal and the pressure sensitive element are covered with a soft resin.

According to a fourth aspect of the present invention, a base, a pressure-sensitive element disposed on the base so as to receive the atmospheric pressure on one end face and the measurement pressure on the other end face, and the pressure-sensing element engaged with the base In the pressure sensor including a cap that covers the pressure-sensitive element and the base from the end surface side that receives the atmospheric pressure of the pressure element, and a connector that is formed on the base and that extracts the detection signal from the pressure-sensitive element to the outside, the bottom of the connector On the base of the pressure sensitive element, a communication hole for introducing atmospheric pressure to the room on the side receiving the atmospheric pressure of the pressure sensitive element is formed, and an outside air introduction pipe is connected to the opening to the outside of the connector, or the cap has A feature is that a communication hole that guides the atmospheric pressure is formed in the room that receives the atmospheric pressure of the pressure element, and an outside air introduction pipe is connected to this communication hole, and this outside air introduction pipe is connected to a location where clean air can be obtained. And

[0010]

According to the first aspect of the invention, the end surface of the pressure-sensitive element is covered with a cap on the side where atmospheric pressure is introduced. The cap is made of a material that is breathable and blocks the passage of moisture. Since it is formed, only the atmosphere is introduced into the room of the pressure sensor where the atmosphere is introduced, and mud, dust, and water are blocked. Therefore, the end surface of the pressure sensitive element to which the atmospheric pressure is applied,
Since the mud, dust, dust, water, etc. do not adhere, the pressure sensitive element is prevented from being broken. In addition, since the entire cap is formed of a material having air permeability, the inner chamber of the pressure sensor does not become lower than the atmospheric pressure of the outside due to clogging, and therefore an accurate minute differential pressure can be detected. . In addition, even if the pressure-sensitive element is destroyed, it will not pass through the cap even if the measurement pressure medium enters the inner chamber of the pressure-sensitive element that receives the atmospheric pressure. The release of pressure medium is prevented.

According to the second aspect of the present invention, the surface of the cap is covered with the metal net in the shape of a wire mesh, which reinforces the mechanical strength of the cap.

According to the third aspect of the present invention, it is a part that separates the space into which the measurement pressure is introduced from the space into which the atmospheric pressure is introduced, and the connection between the parts, that is, the pressure-sensitive element and the pedestal. Since the connection between the pedestal and the base is covered with resin,
Since there is no measurement pressure or atmospheric leak, an accurate minute differential pressure can be detected.

According to the invention of claim 4, in a pressure sensor having a connector for extracting a detection signal formed on the base to the outside, the base on the bottom of the connector has a room on the side receiving the atmospheric pressure of the pressure sensitive element. To form a communication hole that guides atmospheric pressure to
Alternatively, a communication hole is formed in the cap that covers the pressure-sensitive element and the base, the outside air introduction pipe is connected to the opening to the outside of the connector, and this outside air introduction pipe is connected to a location where clean air can be obtained. Clean air in the atmosphere is introduced into the inner chamber of the pressure sensor. Therefore, mud, dust, dust, water, etc. do not adhere to the pressure-sensitive element, and the element is prevented from being destroyed and the measurement accuracy is prevented from lowering.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the present invention will be described with reference to the drawings. First Embodiment In FIG. 1, a pressure sensor 10 has a metal-based header (secret terminal body) 11, and a measuring pressure introducing pipe 12 is inserted into a hole 13 formed in the center of the header 11 and brazing or the like. Is connected to the header 11 by the above method. Further, the joint between the measuring pressure introducing pipe 12 and the header 11 is sealed with solder 21. A pedestal 14 made of glass (borosilicate glass such as Pyrex glass) is confidentially bonded to the inlet / outlet 12b of the measurement pressure introducing pipe 12 by an anodic bonding method, and the semiconductor piezoelectric strain element is mounted on the pedestal 14. The pressure-sensitive element 15 composed of the bridge circuit is joined. Further, the lead pins 16a to 16d are provided so as to be sealed by hermetic glass 17 so as to penetrate the header 11. These lead pins 16
Reference symbols a to 16d are terminals for supplying power to the pressure-sensitive element 15 and terminals for extracting a signal from the pressure-sensitive element 15 to the outside. The lead pins 16a to 16d are used for the pressure-sensitive element 15
Are electrically connected to each other by a wire 22.

An introduction hole 18 is previously formed in the pedestal 14, and the introduction hole 18 is joined to the measuring pressure introduction pipe 12. The pressure to be measured is applied to the one end surface 15 a of the pressure sensitive element 15 via the measurement pressure introducing pipe 12 and the introduction hole 18.

The flange portion 11a of the header 11 is in contact with the flange portion 19a of the cap 19 so that the cap 19
Is fixed to the header 11 by a clip 20. The cap 19 is made of a member that blocks the passage of moisture, mud, dust, etc., and allows only air to pass. The cap 19 allows the atmosphere to be introduced into the pressure sensor 10 without pressure loss. The cap 19 is formed in a shell shape, and does not deform due to a normal external mechanical stress, and has a hardness capable of protecting the pressure sensitive element 15 and the wire 22 from an external force. The cap 19 is formed of a diaphragm having air permeability and water repellency. Specifically, a porous material such as tetrafluoroethylene resin can be used. Further, a reinforcing material such as metal or resin may be inserted into the meat in the cap 19.

The cap 19 is made of a material having air permeability and water absorbability, such as Sunwet 1M-.
A breathable water-absorbent membrane containing 1000 (manufactured by Sanyo Kasei Co., Ltd.) may be used. Furthermore, for the cap 19, a breathable water absorbing sheet such as an SAP sheet (manufactured by Sanyo Kasei Co., Ltd.) may be used.

The pressure sensor 10 shown in FIG. 1 is installed in the housing 100 as shown in FIG. The lead pins 16a to 16d are connected by soldering or welding to a connector terminal 102 arranged in advance in the housing 100. An introduction pipe 104 for introducing the measurement pressure is arranged in the housing 100 so as to be continuous with the measurement pressure introduction pipe 12 of the pressure sensor 10. or,
The measuring pressure introducing pipe 12 is hermetically sealed to the housing 100 by an O-ring 108 at the bottom of the housing 100. On the other hand, an introduction hole 106 for introducing atmospheric pressure is formed in the upper part of the housing 100. With this structure, atmospheric pressure is introduced into the housing 100 through the introduction hole 106, passes through the cap 19 and is introduced into the pressure sensor 10, and the pressure-sensitive element 15 is introduced.
Is applied to the measurement pressure end face of. In addition, the measurement pressure is 1
04, it is introduced into the pressure sensor 10 through the measurement pressure introduction pipe 12, and is applied to the measurement pressure end face of the pressure sensitive element 15 of the pressure sensor 10 through the introduction hole 18 of the pedestal 14.

When the pressure in the gasoline tank of the automobile is measured, the housing 100 is arranged at a position where the introduction pipe 104 is opened inside the gasoline tank and the introduction hole 106 is opened to the atmosphere. However, in the case of an automobile, muddy water, dust, dirt such as high-pressure shower cleaning water, water, and the like enter the introduction hole 106 that is open to the atmosphere. In such a case, if the cap 19 of the pressure sensor 10 is gas permeable and is formed of a substance that blocks the passage of water due to water repellency or water absorption, as in the present embodiment, the pressure is reduced. It is possible to prevent muddy water, dust, water, etc. from entering the inside of the sensor 10. Moreover, the required atmosphere can be introduced into the pressure sensor 10. Therefore, it is possible to prevent adhesion of mud, dust, water, etc. to the pressure-sensitive element 15, so that it is possible to prevent the pressure-sensitive element 15 from being broken. Moreover, since the cap 19 has air permeability over the entire surface, clogging can be prevented, so that the inside of the pressure sensor 10 has an accurate atmospheric pressure.

Further, the cap 19 is used for the pressure sensor 10.
When mounting the unit on the housing 100, the pressure-sensitive element 15,
It acts to mechanically protect the lead pins 16a to 16d and the wire 22. Also, the pressure sensor 1
When 0 is used, oil can be removed by forming the cap 19 with an oil absorbing material.

The cap 19 can be formed by cutting, injection molding, extrusion molding or the like. A material formed by impregnating a non-woven fabric, a metal filter or the like with a water repellent material, a water absorbent material or the like or kneading may be used. Further, the base material such as a non-woven fabric may be formed on the surface (either one side or both sides) by a method such as coating or pasting so as to exhibit the function of water repellency or water absorption while ensuring air permeability. In particular, when a highly malleable material such as a metal material is used as the base material, the breathable cap can be manufactured by a simple method such as pressing.

Second Embodiment As shown in FIG. 3, the pressure sensor 10 of the present embodiment covers the inner and outer surfaces of the cap 19 of the pressure sensor 10 of the first embodiment with metal nets 23a, 23b in the form of wire mesh. It is a thing. When the thickness of the cap 19 is thin and the shape of the cap cannot be maintained, or when the cap 19 cannot support the external stress of the cap when it is formed of a brittle material,
It is extremely effective to bond the metal nets 23a and 23b together. Further, when the cap 19 is not conductive, the metal nets 23a and 23b have a function of removing electromagnetic noise or the like that affects the pressure sensitive element 15 by noise. That is, it has an EMI shield function.

[0023] The pressure sensor 10 of the third embodiment The third embodiment is that efforts to airtightness failure due to variations in manufacturing measures. In the pressure sensor 10 of the first embodiment, airtight leakage may occur due to manufacturing variations at the joint between the pressure sensitive element 15 and the pedestal 14 and at the joint between the pedestal 14 and the measurement pressure introducing pipe 12. Therefore, in the present embodiment, as shown in FIG. 4, a soft resin 24 is coated all around the joint between the pressure sensitive element 15 and the pedestal 14 and the joint between the pedestal 14 and the measurement pressure introducing pipe 12. Is. The diameter of the introduction hole 18 of the pedestal 14 is set to 0.1 to 0.2 mm, so that the pressure sensitive element 15
Even if the fuel is destroyed, the release of the measured pressure medium, that is, gasoline, into the atmosphere is suppressed to an extremely small amount. Also, the pedestal 14
Has a stepped portion 14a formed in an L shape in the upper part, so that the soft resin 24 is firmly attached to the pedestal 14.

FIG. 5 shows a pressure sensor 50 according to a modification of the third embodiment. The pressure sensitive element 15, the pedestal 14 made of glass, the introduction hole 18, and the measurement pressure introduction pipe 12 have the same configurations as in the third embodiment. In this modification, the header 11
Instead of this, a stem 52 and a glass 53 are used. That is, the measurement pressure introducing pipe 12 and the lead pins 16a and 16c are hermetically attached to the stem 52 by the glass 53. A cap 51 is brazed to the stem 52. The cap 51 has only side walls and is open at the top. The space formed by the cap 51 and the stem 52 is filled with a gel-like soft resin 54. Also in this modification, the diameter of the introduction hole 18 of the pedestal 14 is 0.2 mm or less. With this configuration, even if the pressure sensitive element 14 is destroyed, the measured pressure medium and gasoline are prevented from being discharged to the atmosphere side.

Fourth Embodiment As shown in FIG. 6, the pressure sensor 30 of the fourth embodiment is characterized by the method of introducing the atmosphere. In this pressure sensor 30,
A measurement pressure introducing pipe 32 for introducing a measurement pressure at the bottom of the base 31 and a connector 33 on the side surface of the base 31 are formed integrally with the base 31. Then, as in the first embodiment, the pressure sensitive element 35 is joined to the glass pedestal 34 by anodic bonding, the lead pins 36 are connected to the printed circuit board 47, and the printed circuit board 47 is connected to the internal space of the connector 33. It is electrically connected to the protruding external terminal 45. Further, the introduction hole 41 of the pedestal 34 is connected to the introduction pipe 40, and the introduction pipe 40 is connected to the measurement pressure introduction pipe 32. Resin 48 filled in the bottom of the base 31
Thus, the printed circuit board 47, the lead pin 36, the introduction pipe 40, and the printed circuit board 47 are held. further,
The upper portion of the pressure sensitive element 35 is covered with protective caps 42 and 43. Further, the pressure sensor 30 has a resin cap 39 that engages with the base 31 on the side surface, and the base 31 and the cap 3
9 and 9 form a casing of the pressure sensor 30.

On the other hand, an atmospheric air introducing hole 44 is formed in the side wall of the base 31 which is connected to the connector 33, and the atmospheric air is introduced into the pressure sensor 30 through the atmospheric air introducing hole 44. The connector 33 is connected to the introduction pipe 46, and the introduction pipe 46 is open to the space A.
This space A is for air cleaner, passenger compartment, trunk, EC
It is a space where there is no dirty air such as U and there is a clean atmosphere.

Separately from this, the atmosphere introducing hole 44 is provided in a place other than the connector 33, for example, in the cap 39, and the atmosphere introducing hole 44 is connected to the introducing pipe 46 and opened to the space A. Is also good. With the configuration as described above, the atmosphere from which mud, dust, water, etc. have been removed is detected by the pressure sensor 3.
0 inside, and their adhesion to the pressure sensitive element 35 is prevented.

Fifth Embodiment In the fourth embodiment, the atmosphere is introduced from the side wall of the base 31 through the introduction hole 44, but the pressure sensor 60 shown in FIGS. 7 and 8 is used.
Atmosphere is introduced through the introduction hole 63 formed in the cap 61. In the pressure sensor 60 shown in FIG. 7, the filter 62 is arranged in the introduction hole 64 of the protective cap 43. With this filter 62, mud, dust,
Dust, water, etc. are removed and prevented from adhering to the end surface of the pressure sensitive element 35 on the side where the atmospheric pressure is applied.

Further, the sensor shown in FIG.
The filter 62 is attached to the introduction hole 63 formed in No. 1. With this filter 62, mud, dust,
Dust, water, etc. are removed and prevented from adhering to the end surface of the pressure sensitive element 35 on the side where the atmospheric pressure is applied.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a housing in which the pressure sensor of the same embodiment is arranged.

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

FIG. 4 is a sectional view showing the configuration of a pressure sensor according to a third embodiment of the invention.

FIG. 5 is a sectional view showing the configuration of a pressure sensor according to a modification of the third embodiment of the present invention.

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

FIG. 7 is a sectional view showing a configuration of a pressure sensor according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing the structure of a pressure sensor according to a fifth embodiment of the present invention.

[Simple explanation of symbols]

 10, 30, 50, 60 ... Pressure sensor 11 ... Header (base) 12 ... Measuring pressure introducing pipe (base) 14 ... Pedestal (base) 15 ... Pressure sensitive element 16a to 16d ... Lead pin 18 ... Introducing hole 19 ... Cap 31 ... Base 39 ... Cap 44 ... Atmosphere introduction hole 45 ... External terminal 46 ... Atmosphere introduction pipe 47 ... Printed circuit board 48 ... Resin 51 ... Cap 52 ... Stem (base) 53 ... Glass (base) 54 ... Soft resin 100 ... Housing

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironobu Baba 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihondenso Co., Ltd.

Claims (4)

[Claims] 1. A base, a pressure sensitive element disposed on the base so as to receive an atmospheric pressure on one end surface and a measurement pressure on the other end surface, and the pressure sensitive element engaged with the base base. In the pressure sensor including the pressure-sensitive element and a cap that covers the base from the end surface side that receives the atmospheric pressure, the cap is formed of a substance that has air permeability and blocks the passage of moisture. Pressure sensor. 2. The pressure sensor according to claim 1, wherein a surface of the cap is covered with a metal net having a metal mesh shape. 3. The base comprises a measuring pressure introducing pipe for introducing a measuring pressure and a pedestal connected to an inlet / outlet of the measuring pressure introducing pipe to dispose the pressure sensitive element. The pressure sensor according to claim 1, wherein a joint portion of the pedestal and a joint portion of the pedestal and the pressure sensitive element are covered with a soft resin. 4. A base, a pressure-sensitive element disposed on the base so as to receive an atmospheric pressure on one end surface and a measurement pressure on the other end surface, and the pressure-sensitive element engaged with the base. A pressure sensor comprising a cap that covers the pressure-sensitive element and the base from the end surface side that receives the atmospheric pressure of, and a connector that is formed on the base to take out a detection signal from the pressure-sensitive element to the outside, On the base of the bottom of the connector, a communication hole for introducing atmospheric pressure to the room that receives the atmospheric pressure of the pressure-sensitive element is formed, and an outside air introduction pipe is connected to the opening to the outside of the connector, or In the cap, a communication hole for introducing atmospheric pressure is formed in the room on the side receiving the atmospheric pressure of the pressure-sensitive element, and an outside air introduction pipe is connected to this communication hole, and this outside air introduction pipe is a portion where clean air can be obtained. Pressure characterized by being connected to Capacitors.