JP2015161601A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor capable of determining whether or not foreign bodies adhere to an introduction path.SOLUTION: A pressure sensor includes: an introduction path 80 which introduces a measurement medium into a pressure detection element 22 and which has a resonance frequency different from a frequency of the measurement medium; and diagnostic means 23 for performing such a self-diagnosis that is determined that foreign bodies 100 are adhered to the introduction path 80 when the resonance frequency of the introduction path 80 is out of a predetermined range of the frequency.

Description

  The present invention relates to a pressure sensor in which a sensor signal corresponding to the pressure of a measurement medium introduced into an introduction path is output from a pressure detection element.

  Conventionally, a pressure detection element that assembles a port portion in which a plurality of pressure introduction holes are formed in a case and outputs a sensor signal corresponding to the pressure of a measurement medium to a pressure detection chamber configured between the case and the port portion (For example, refer patent document 1).

  Specifically, in such a pressure sensor, the port portion is configured with a chamber whose wall surface is tapered by widening the end portion on the case side of each pressure introducing hole. A pressure detection chamber is configured. When the measurement medium is applied to the pressure detection element via the introduction path constituted by the pressure introduction hole and the pressure detection chamber, a sensor signal corresponding to the pressure of the measurement medium is output from the pressure detection element.

  According to such a pressure sensor, when water droplets are generated in the pressure detection chamber due to condensation, the water droplets slide down the wall surface of the tapered room and are discharged to the outside from each pressure introducing hole. That is, the amount of water droplets passing through each pressure introduction hole is reduced, and the pressure introduction hole can be prevented from being blocked.

JP 2008-292268 A

  However, although the pressure sensor can suppress the pressure introduction holes from being blocked by water droplets, it is difficult to completely prevent the pressure introduction holes from being blocked. Further, the pressure introducing hole may be blocked by dust or dust existing in the external space.

  In the pressure sensor, even if the pressure introduction hole (introduction path) is blocked by foreign matter such as water droplets, dust, and dust, the pressure detection element continues to output a signal corresponding to the pressure in the closed space. That is, the pressure sensor has a problem that the pressure of the measurement medium may not be detected accurately.

  In view of the above points, an object of the present invention is to provide a pressure sensor that can determine whether or not foreign matter has adhered to an introduction path.

  In order to achieve the above object, according to the first aspect of the present invention, the case (10) in which the pressure introduction hole (13) for introducing the pressure of the measurement medium is formed, and the case (10) mounted on the case, depending on the pressure of the measurement medium. And a pressure detection element (22) that outputs a sensor signal.

  That is, the introduction path (80) for introducing the measurement medium into the pressure detection element includes a pressure introduction hole, and the introduction path has a resonance frequency different from the frequency of the measurement medium. When the resonance frequency is outside the predetermined frequency range, a diagnostic means (23) for performing self-diagnosis to determine that the foreign substance (100) is attached to the introduction path is provided.

  As described above, by determining whether or not the resonance frequency of the introduction path is out of the predetermined frequency range, it is possible to perform self-diagnosis for determining whether or not foreign substances are attached to the introduction path. For this reason, it can suppress performing pressure detection in the state where the introduction course is obstructed.

  In addition, the resonance frequency of the introduction path varies depending on the state of foreign matter adhering to the introduction path. For this reason, by appropriately setting the frequency range to be compared, even if the introduction path is not completely blocked by foreign matter, it is possible to self-diagnose that there is an abnormality when the measurement medium cannot be introduced properly. .

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing of the pressure sensor in 1st Embodiment of this invention. It is another sectional drawing of the pressure sensor shown in FIG. It is an enlarged view of the area | region A enclosed with the dashed-two dotted line in FIG. It is a figure which shows the circuit structure of a circuit chip. (A) is a schematic diagram of the introduction path, (b) is a diagram showing the relationship between the resonance frequency and the sensor signal. (A) is a schematic diagram when a foreign material adheres to the introduction path, and (b) is a diagram illustrating a relationship between a resonance frequency and a sensor signal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment of the present invention will be described. The pressure sensor of the present embodiment is preferably attached to a space in a vehicle door, for example, and used as a pressure sensor for detecting the pressure in the vehicle door.

  As shown in FIGS. 1 and 2, the pressure sensor includes a case 10. For example, the case 10 has a substantially cylindrical shape made by molding a resin material. A recess 11 is formed on one end (upper end on the paper surface in FIG. 1), and an opening 12 is formed on the other end (end on the lower surface in FIG. 1) side.

  In addition, the case 10 is formed with a pressure introducing hole 13 for communicating the space in the recess 11 and the external space and introducing the measurement medium from the external space. In FIG. 1, the pressure introduction hole 13 has a shape in which the path through which the measurement medium passes is bent, but the path through which the measurement medium passes may be in a shape that does not bend.

  A sensor unit 20 is disposed in the recess 11 of the case 10. As shown in FIG. 3, the sensor unit 20 has a one surface 21a and another surface 21b, and a ceramic substrate in which the one surface 21a and the other surface 21b are electrically connected via a wiring pattern, a via, or the like. A wiring board 21 such as a printed board is provided. A sensor chip 22 and a circuit chip 23 are mounted on one surface 21 a of the wiring board 21, and the sensor chip 22 and the circuit chip 23 are electrically connected to the wiring board 21 via bonding wires 24. Further, an electronic component 25 such as a capacitor is mounted on the other surface 21b of the wiring board 21 via a conductive adhesive or the like (not shown).

  The sensor chip 22 outputs a sensor signal corresponding to the pressure of the measurement medium, and corresponds to the pressure detection element of the present invention. In this embodiment, a gauge resistor is formed so as to form a bridge circuit in the diaphragm, and when pressure is applied to the diaphragm, the resistance value of the gauge resistor changes and the voltage of the bridge circuit changes. A semiconductor diaphragm type that outputs a corresponding sensor signal is used.

  The circuit chip 23 has a signal processing function for performing predetermined processing on the sensor signal, and corresponds to the diagnostic means of the present invention. In the present embodiment, as shown in FIG. 4, the circuit chip 23 includes an amplifier circuit 23 a that amplifies the sensor signal output from the sensor chip 22 by a predetermined factor and outputs the amplified signal. Further, it has a low-pass filter 23b and a band-pass filter 23c connected to the amplifier circuit 23a, a phase synchronization circuit (PPL circuit) 23d connected to the band-pass filter 23c, a determination circuit 23e connected to the phase synchronization circuit 23d, and the like. ing.

  In the present embodiment, the low pass filter 23b corresponds to the first filter of the present invention, and the band pass filter 23c corresponds to the second filter of the present invention.

  Here, although specifically described later, processing of the circuit chip 23 will be briefly described. When a sensor signal is output from the sensor chip 22, the sensor signal is amplified by a predetermined factor by the amplifier circuit 23a and then input to the low-pass filter 23b and the band-pass filter 23c. The sensor signal input to the low-pass filter 23 b is attenuated in a component having a predetermined frequency or higher and output to the external circuit 30. The low-pass filter 23b is designed to pass a frequency component that the measurement medium may have.

  On the other hand, the sensor signal input to the bandpass filter 23c is attenuated in components below a predetermined frequency and output to the phase synchronization circuit 23d. The phase synchronization circuit 23d has a phase comparator, a frequency divider, a voltage controlled oscillator, and the like, and outputs a signal corresponding to the difference between the phase of the input signal and the phase of the reference signal output from the frequency divider. Things are used. That is, the phase synchronization circuit 23d outputs a signal corresponding to the phase difference between the phase of the signal input via the bandpass filter 23c and the phase of the reference signal. The band-pass filter 23c is designed to pass a resonance frequency component that an introduction path 80 described later may have.

  The determination circuit 23e determines whether or not the signal input from the phase synchronization circuit 23d is within a predetermined range, and outputs the determination result to the external circuit 30.

  Further, as shown in FIG. 3, the sensor unit 20 includes a connection member 26 made by molding a resin material. In the present embodiment, the connection member 26 has a frame shape along the outer edge of the wiring substrate 21, and has one end (the upper end on the paper surface in FIG. 1) and the other end (the lower end on the paper surface in FIG. 1). ) Between the projections 26a projecting inward. And the one end part side of the protrusion part 26a is a part of the wiring board 21 so that one end part side is arrange | positioned along the side surface of the wiring board 21, and the other end part side protrudes from the one surface 21a of the wiring board 21. It is joined to the outer edge part of the one surface 21a through the adhesive 27.

  Further, a protective member 28 is disposed on the one surface 21 a side of the wiring board 21 so as to seal the sensor chip 22, the circuit chip 23, and the bonding wire 24 in a space surrounded by the connection member 26. That is, the connection member 26 has a function as a dam that suppresses the protection member 28 from spreading wet. As the protective member 28, for example, a material excellent in corrosion resistance, chemical resistance, or the like such as silicone gel or fluorine gel is used.

  The above is the configuration of the sensor unit 20. As shown in FIGS. 1 and 2, the sensor unit 20 is mounted in the recess 11 so as to close the opening of the pressure introducing hole 13 formed in the bottom surface of the recess 11. Specifically, the other end portion side of the connection member 26 is mounted on the bottom surface of the recess 11 with an adhesive 29 so that the one surface 21 a of the wiring board 21 faces the bottom surface of the recess 11.

  In addition, by mounting the sensor unit 20 in the recess 11, the chamber 14 is formed between the protective member 28 and the bottom surface of the recess 11. That is, in the pressure sensor of this embodiment, the measurement medium introduced into the pressure introducing hole 13 is applied to the sensor chip 22 after being introduced into the room 14. That is, in this embodiment, the pressure introduction hole 13 and the room 14 constitute the introduction path of the present invention.

  Further, the case 10 is provided with a plurality of metal rod-like terminals 40 electrically connected to the wiring board 21. Each terminal 40 is formed integrally with the case 10 by insert molding. 10.

  Specifically, each terminal 40 is held in the case 10 such that one end protrudes into the recess 11 and the other end protrudes into the opening 12. One end of each terminal 40 protruding into the recess 11 is electrically connected to the wiring board 21 via a bonding wire 50. The other end of each terminal 40 is electrically connected to the external circuit 30 via an external wiring member (not shown). That is, a signal from the circuit chip 23 is output to the external circuit 30 via the terminal 40.

  In addition, a lid 60 made by molding a resin material is joined to the case 10 via an adhesive (not shown) so as to close the recess 11. Furthermore, between the one end part and the other end part of the case 10, a bolt 70 for attaching the pressure sensor to the attached member is also insert-molded.

  The above is the configuration of the pressure sensor in the present embodiment. In such a pressure sensor, an introduction path (resonance tube) 80 having a predetermined resonance frequency is constituted by the pressure introduction hole 13 and the chamber 14 as shown in FIG. Note that the resonance frequency of the introduction path 80 is different from the frequency that the measurement medium may have. In this embodiment, since the frequency that the measurement medium may have is several hundred Hz, the introduction path 80 is designed so that the resonance frequency is several to several tens KHz.

  For this reason, as shown in FIG. 5B, when a sound having a frequency component matching the resonance frequency is applied from the external sound source 90, a peak value appears in the sensor signal due to resonance.

  As shown in FIG. 6A, when the foreign matter 100 adheres to the pressure introduction hole 13, the cross-sectional area of the pressure introduction hole 13 becomes small, and the path through which the measurement medium passes becomes narrow. For this reason, as shown in FIG. 6B, the resonance frequency of the introduction path 80 becomes low, and the peak value fluctuates.

  In addition, when the foreign material 100 adheres to the room 14, the volume of the room 14 becomes small, so that the resonance frequency of the introduction path 80 becomes high.

  Next, the operation of the pressure sensor will be specifically described. The pressure sensor is used by being attached to a space in a vehicle door, for example. In addition, the space in the door of a vehicle is the space pinched | interposed into the outer panel which comprises the outdoor side of a door, and the door trim of a room inner side. When the inner trim is arranged between the outer panel and the door trim, the space in the door is the space between the outer panel and the inner panel, or the space between the inner trim and the door trim. That is.

  When the measurement medium is introduced into the pressure introducing hole 13, a sensor signal corresponding to the pressure of the measurement medium is output from the sensor chip 22. When a sound having a frequency that matches the resonance frequency of the introduction path 80 is applied from a sound source 90 such as a speaker mounted on the vehicle, a peak value appears at that frequency.

  As shown in FIG. 3, the sensor signal output from the sensor chip 22 is amplified by the amplifier circuit 23a and then input to the low pass filter 23b and the band pass filter 23c. The signal output from the low-pass filter 23b is input to the external circuit 30. The external circuit 30 detects the pressure of the measurement medium based on the signal.

  The signal output from the bandpass filter 23c is input to the phase synchronization circuit 23d. Then, the phase synchronization circuit 23d outputs a signal corresponding to the phase difference between the phase of the signal input from the bandpass filter 23c and the phase of the reference signal.

  Here, as described above, when the foreign matter 100 is attached to the introduction path 80, the resonance frequency changes, so the signal output from the phase synchronization circuit 23d is the adhesion state of the foreign matter 100 in the introduction path 80. It depends on. Then, the determination circuit 23e determines whether or not the signal is within a predetermined range, and determines that the foreign material 100 is attached to the introduction path 80 when the signal is out of the predetermined range. Is input to the external circuit 30. That is, when the resonance frequency of the introduction path 80 is outside the predetermined frequency range, the determination circuit 23e determines that the foreign material 100 is attached to the introduction path 80 and inputs the determination result to the external circuit 30.

  When the pressure sensor is mounted on a vehicle and used, the external circuit 30 notifies the occupant that the pressure sensor is abnormal. For example, the external circuit 30 displays an abnormality occurrence on a liquid crystal display arranged in a part of an instrument display panel arranged in front of the handle or in the center of the dashboard, or plays an abnormality occurrence sound from the sound source 90. Etc. can be notified to the passenger.

  As described above, the self-diagnosis is performed to determine whether or not the foreign material 100 is attached to the introduction path 80 by determining whether or not the resonance frequency of the introduction path 80 is outside the predetermined frequency range. be able to. By performing the self-diagnosis in this way, for example, when the pressure sensor is mounted on a vehicle and used, the occupant can be notified of the abnormality of the pressure sensor, and the pressure can be detected while the introduction path 80 is closed. It can suppress performing detection.

  Moreover, in the said pressure sensor, even if the introduction path | route 80 is not obstruct | occluded completely, it can determine. That is, by appropriately setting the frequency range to be compared by the determination circuit 23e, it can be determined that there is an abnormality when the measurement medium cannot be properly introduced even if the introduction path 80 is not completely blocked.

  Furthermore, in the pressure sensor, it is not necessary to arrange a new separate member for performing a self-diagnosis, and the structure can be prevented from becoming complicated.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in the first embodiment, the introduction path 80 may be formed by only the pressure introduction hole 13.

  In the first embodiment, the circuit chip 23 may be disposed on the other surface 21 b of the wiring board 21. Similarly, the electronic component 25 may be disposed on the one surface 21 a of the wiring board 21.

  In the first embodiment, the introduction path 80 may be configured to have a resonance frequency lower than a frequency that the measurement medium may have.

  Further, in the first embodiment, disturbance noise (white noise) such as engine sound generated while the vehicle is running may be used as the sound source 90. Further, the sound source 90 may be disposed in the recess 11, for example. That is, a pressure sensor including the sound source 90 may be used.

  In the first embodiment, the case 10 may be composed of two members. For example, the case 10 may be configured by assembling a first member in which the pressure introduction hole 13 is formed and a second member on which the sensor unit 20 is mounted.

DESCRIPTION OF SYMBOLS 10 Case 13 Pressure introduction hole 22 Pressure detection element 23 Diagnosis means 80 Introduction path 100 Foreign material

Claims (3)

A case (10) in which a pressure introduction hole (13) for introducing the pressure of the measurement medium is formed;
A pressure detection element (22) mounted on the case and outputting a sensor signal in accordance with the pressure of the measurement medium;
An introduction path (80) for introducing the measurement medium into the pressure detection element includes the pressure introduction hole,
The introduction path has a resonance frequency different from the frequency of the measurement medium;
When the resonance frequency of the introduction path is out of a predetermined frequency range, diagnostic means (23) for performing self-diagnosis for determining that a foreign substance (100) is attached to the introduction path is provided. Pressure sensor. A chamber (14) is formed between the pressure introduction hole and the pressure detection element,
The pressure sensor according to claim 1, wherein the introduction path includes the pressure introduction hole and the room. The diagnostic means includes a first filter (23b) that passes a frequency component of the measurement medium in the sensor signal, and a second filter (23c) that passes a resonance frequency component of the introduction path of the sensor signal. A phase synchronization circuit (23d) connected to the second filter and outputting a signal corresponding to a phase difference between a signal input from the second filter and a reference signal, and connected to the phase synchronization circuit and The pressure sensor according to claim 1 or 2, further comprising: a determination circuit (23e) that determines whether or not a signal input from the phase synchronization circuit is within a predetermined range.

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