JP2008309663A - Resonance-type knocking sensor and its mounting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resonance-type knocking sensor capable of preventing loosening of uniting by screwing between a mounting screw member and the tapped hole part of a main body metal fitting, and ensuring conduction between the mounting screw member and the main body metal fitting. <P>SOLUTION: The resonance-type knocking sensor 1 is provided with a vibrating body 11 composed of a metallic vibrating plate 21 and a piezoelectric element 22 stuck to the vibrating plate 21 and provided with a pair of electrodes, the main body metal fitting 12 which is in the shape of a bottomed cylinder and houses the vibrating body 11, and is fixed to an engine block 200 whose potential is treated as a reference potential, and the metallic mounting screw member 13 which extends along the direction of an axis O, supports the vibrating body 11, and the screw part 41 of which is screwed into the tapped hole part 37 in the bottom part of the metal fitting 12 and is united. The gap between the tapped hole 37 and the screw part 41 of the screw member 13 is filled with conductive adhesive 25, and one of the pair of electrodes is set to the reference potential through the vibrating plate 21, the screw member 13, the conductive adhesive 25, and the metal fitting 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resonance type knocking sensor for detecting knocking of an internal combustion engine and a mounting structure thereof.

  Conventionally, various types of knocking sensors that are attached to an internal combustion engine and detect knocking that occurs in the internal combustion engine have been developed. One of them is a resonance type knocking sensor that detects the knocking by vibrating a vibrating body including a diaphragm and a piezoelectric element attached to the diaphragm.

  This type of resonant knocking sensor includes a vibrating body in which a piezoelectric element having a pair of electrodes is attached to a metal diaphragm, a bottomed cylindrical metal shell that houses the vibrating body, and an axial direction. And having a metal mounting screw member screwed into a screw hole formed at the bottom of the metal shell, while supporting the vibrating body at one end thereof. Then, by fixing the metal shell at a predetermined position of the engine block, the resonance type knocking sensor is attached to the engine block which is an attachment object.

In the resonance type knocking sensor configured as described above, one of the electrodes of the piezoelectric element is grounded to the engine block via the diaphragm, the mounting screw part, and the metal shell, and the other is connected via the lead wire or the like. It is connected to a terminal that outputs an electrical signal to an external device. That is, the potential of one of the electrodes is the same as the potential of the engine block and is the reference potential.
When the vibrating body vibrates due to the vibration of the internal combustion engine, the electric charge generated in the piezoelectric element is output to the outside as a detection (electrical) signal through the other electrode, lead wire, and terminal. . Then, the detection signal obtained from the resonance type knocking sensor is taken into an engine control device or the like, and it is determined whether or not knocking has occurred. (See Patent Document 1).
JP-A-9-269270

  In such a resonance type knocking sensor, since it is exposed to the vibration of the internal combustion engine for a long period of time, the other end portion (screw portion) of the mounting screw member and the screw hole portion of the metal shell are loosened by the vibration. there were. When the screwing is loosened, the fixing of the mounting screw member and the metal shell itself is also loosened, so that the vibration of the internal combustion engine is not transmitted to the vibrating body via the metal shell and the screw member, and the knocking generated in the internal combustion engine is accurate. Sometimes it could not be detected well.

  Therefore, a method of filling the gap between the other end portion (screw portion) of the mounting screw member and the screw hole portion of the metal shell can be considered. However, when an insulating material is used as the adhesive, in order to ensure electrical continuity between the mounting screw member and the metal shell, it protrudes outward in the radial direction formed on the rear end side from the threaded portion of the mounting screw member. The mounting screw member and the metal shell must be partially brought into contact, for example, by seating the flange portion on the bottom of the metal shell.

  However, in such a case, if an insulating foreign material or edge adhesive enters the seating (abutment) surface between the mounting screw member and the metal shell, poor continuity is caused between the mounting screw member and the metal shell. May occur. In addition, even if the other end (screw portion) of the mounting screw member and the screw hole of the metal shell are loosened, the flange portion of the mounting screw member and the bottom of the metal shell do not come into contact with each other. There is a risk of defects. As described above, when a conduction failure occurs, the output signal may not be output correctly from the sensor.

  The present invention solves the above-described conventional problems, and suppresses loosening of the screwing between the mounting screw member and the screw hole portion of the metal shell, and ensures resonance between the mounting screw member and the metal shell. An object of the present invention is to provide a mold knocking sensor and its mounting structure.

  A resonance type knocking sensor of the present invention includes a vibrating body made of a metal diaphragm, a piezoelectric element attached to the diaphragm and having a pair of electrodes, and a bottomed cylindrical shape that houses the vibrating body. And a metal shell that is fixed to a mounting object having a reference potential, and that extends along the axial direction, supports the vibrating body at one end thereof, and the other end is the bottom of the metal shell. In the resonant knocking sensor including a metal mounting screw member screwed into the screw hole portion formed in the conductive hole, the gap between the screw hole portion and the other end portion of the mounting screw member is electrically conductive. An adhesive is filled, and one of the pair of electrodes is set to the reference potential via the diaphragm, the mounting screw member, the conductive adhesive, and the metal shell. .

Moreover, in this invention, the adhesive strength of the said conductive adhesive can be 10 N / mm < ² > or more.
Furthermore, in this invention, melting | fusing point of the said conductive adhesive can be 130 degreeC or more.

  On the other hand, the resonant knocking sensor mounting structure of the present invention includes a vibrating body composed of a metal diaphragm and a piezoelectric element attached to the diaphragm and having a pair of electrodes, and houses the vibrating body. A bottomed cylindrical metal shell that extends along the axial direction, supports the vibrating body at one end thereof, and is screwed into a screw hole formed at the bottom of the metal shell. In a resonance type knocking sensor mounting structure for fixing a resonance type knocking sensor comprising a metal mounting screw member to an attachment object, the screw hole portion and the other end portion of the mounting screw member The gap is filled with a conductive adhesive, and one of the pair of electrodes has the same potential as that of the attachment object.

According to the resonance type knocking sensor of the present invention, since the conductive adhesive is filled in the gap between the screw hole of the metal shell and the other end of the mounting screw member, the screw hole of the mounting screw member and the metal shell The loosening of the screwing can be suppressed.
In addition, even if loosening of the screwing between the mounting screw member and the metal hole of the metal shell occurs, as long as the other end of the mounting screw member is disposed (inserted) in the screw hole of the metal shell, It is possible to ensure conduction between the mounting screw member and the metal shell through the conductive adhesive.
Further, when an insulating adhesive is used, as described above, the mounting screw member and the metal shell need to be partially brought into contact with each other in order to ensure conduction between the mounting screw member and the metal shell. Therefore, it is necessary to change the shape of the mounting screw member or to apply only a predetermined portion of the insulating adhesive. However, if the conductive adhesive is used, the necessity is eliminated, and the manufacturing cost is reduced. .

  As described above, according to the present invention, there is provided a resonance type knocking sensor capable of suppressing looseness of screwing between the mounting screw member and the screw hole portion of the metal shell and ensuring the conduction between the mounting screw member and the metal shell. be able to.

Moreover, in this invention, it is preferable that the adhesive strength of a conductive adhesive shall be 10 N / mm < ² > or more. By setting the adhesive strength to 10 N / mm ² or more, loosening of the screwing can be further suppressed.

Furthermore, the melting point of the conductive adhesive is preferably 130 ° C. or higher. Since the resonance type knocking sensor is used by being attached to an internal combustion engine, it is likely to be exposed to a high temperature, and the screw hole portion of the metal shell may be heated to around 120 ° C. in some cases. In that case, if the melting point of the conductive adhesive is less than 130 ° C., the heat resistance of the conductive adhesive is low, so it deteriorates early and cannot function as an adhesive. There is a risk that loosening of the screw holes with the screw holes will occur. Therefore, by setting the melting point of the conductive adhesive to 130 ° C. or higher, loosening of the screwing between the mounting screw member and the screw hole portion of the metal shell can be further suppressed even when exposed to high temperatures.
Thus, a resonance type knocking sensor having excellent heat resistance can be provided.

According to the mounting structure of the resonance type knocking sensor of the present invention, the conductive adhesive is filled in the gap between the screw hole of the metal shell and the other end of the mounting screw member. Looseness of screwing with the screw hole portion can be suppressed.
In addition, even if loosening of the screwing between the mounting screw member and the metal hole of the metal shell occurs, as long as the other end of the mounting screw member is disposed (inserted) in the screw hole of the metal shell, It is possible to ensure conduction between the mounting screw member and the metal shell through the conductive adhesive.
As described above, according to the present invention, the mounting structure of the resonance type knocking sensor capable of suppressing loosening of the screwing between the mounting screw member and the screw hole portion of the metal shell and ensuring the conduction between the mounting screw member and the metal shell. Can be provided.

Hereinafter, a resonance type knocking sensor and its mounting structure according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional perspective view of a resonance type knocking sensor 1 of the present embodiment.
In the present embodiment, among the directions of the axis O of the resonance type knocking sensor 1 of FIG. 1, the lower side of FIG. 1 (the bottom side of a metal shell 12 described later) is the “tip side”, and the upper side of FIG. It will be described as “rear end side”.

  As shown in FIG. 1, the resonant knocking sensor 1 includes a vibrating body 11 that converts vibration into an electrical signal, a bottomed cylindrical metal shell 12 that houses the vibrating body 11, and an axis O direction. A metal mounting screw member 13 for fixing the vibrating body 11 to the metal shell 12, a terminal 17 for transmitting the electric vibration generated in the vibrating body 11 to the outside via the lead wire 19, and an external impact And a cap 20 for protecting the components from water and an O-ring 23.

  The vibrating body 11 is formed in a disk shape using a metal such as a nickel alloy, for example, and a disk 21 made of a piezoelectric ceramic such as lead zirconate titanate, for example. And a piezoelectric element 22 attached to the main surface of the substrate. The diaphragm 21 and the piezoelectric element 22 are formed with a through hole 26 and a through hole 27 for inserting a rear end portion (a shaft portion 42 described later) of the mounting screw member 13, respectively.

  The metal shell 12 is formed in a bottomed cylindrical shape, and is formed with a recess 31 that is open on the rear end side. Furthermore, a screw hole 37 for fixing the mounting screw member 13 to the metal shell 12 is formed in the bottom 36 of the recess 31. Further, a male screw portion 32 for attaching the resonance type knocking sensor 1 to an engine block 200 of the internal combustion engine (corresponding to an attachment object of the present invention) is provided on the front end side of the metal shell 12.

The attachment screw member 13 is formed with a screw portion 41 that is inserted into and screwed into the screw hole portion 37 on the tip end side, and a mounting tool is attached to the rear end side of the screw portion 41 when attaching to the screw hole portion 37. A hexagonal portion 24 that protrudes outward in the radial direction is formed. And the conductive adhesive 25 is apply | coated to the screw part 41 of the attachment screw member 13, and after inserting and screwing it in the screw hole part 37, the conductive adhesive 25 is hardened. As described above, the attachment screw member 13 is fixed to the metal shell 12, and the conductive adhesive 25 is filled in the gap between the screw portion 41 and the screw hole portion 37 of the attachment screw member 13.
Further, a rod-shaped shaft portion 42 extending in the direction of the axis O is formed on the rear end side of the hexagonal portion 24, and a screw groove 46 is formed on the rear end side of the shaft portion 42. Then, the lower washer 16, the vibrator 11, the upper washer 15, and the nut 14 are inserted into the shaft portion 42 in this order, and the screw groove 46 and the nut 14 are screwed together, so that the nut 14 and the hexagonal portion 24 are The vibrating body 11 is fastened and fixed. As described above, the rear end portion (hexagonal portion 24, shaft portion 42, screw groove 46) of the mounting screw member 13 has a function of supporting the vibrating body 11.

  A cap 20 is fitted into the opening of the metal shell 12 so that components such as the vibrating body 11 can be protected, and the gap between the metal shell 12 and the cap 20 is the elasticity of the O-ring 23. Sealed using force. A connector portion 18 to which an external connector connected to an external device (for example, an ignition timing control device) is connected is formed on the rear end side of the cap 20, and a terminal 17 projects from the connector portion 18. .

  The resonance type knocking sensor 1 configured as described above is attached to a predetermined mounting hole 201 of the engine block 200 of the internal combustion engine using a male screw portion 32 provided on the distal end side of the metal shell 12.

A pair of electrodes is formed on both surfaces of the piezoelectric element 22 by coating a metal layer.
Among these, the electrode formed on the rear end side (upper surface) of the piezoelectric element 22 is connected to a terminal 17 that outputs an electrical signal to an external device via a lead wire 19. The electrode and the lead wire 19 and the lead wire 19 and the terminal 17 are joined by soldering.
The electrode formed on the tip side (lower surface) of the piezoelectric element 22 is grounded to the engine block 200 via the diaphragm 21, the lower washer 16, the mounting screw member 13, the conductive adhesive 25 and the metal shell 12. ing. That is, the potential of this electrode is made substantially the same as the potential of the engine block 200.

Next, the conductive adhesive 25 described above will be described. As the conductive adhesive 25, an epoxy-based conductive adhesive or the like can be used. In the present invention, a conductive adhesive composed of silver powder, a phenol novolac liquid epoxy resin, a phenol resin, and ethylene glycol diglycidyl ether. An agent (eg, Dotite XA-874 manufactured by Fujikura Chemical Co., Ltd.) is used. Such a conductive adhesive 25 is filled in the gap between the screw portion 41 and the screw hole portion 37 of the mounting screw member 13. The conductive adhesive 25 has an adhesive strength of 19 N / mm ² and a melting point of 330 ° C.
Thereby, loosening of the screwing between the mounting screw member 13 and the screw hole portion 37 of the metal shell 12 can be suppressed.
Even if the screwing between the mounting screw member 13 and the screw hole 37 of the metal shell 12 is loosened, the screw portion 41 of the mounting screw member 13 is disposed in the screw hole 37 of the metal shell 12 ( As long as it is inserted, the electrical connection between the mounting screw member 13 and the metal shell 12 can be ensured via the conductive adhesive 25.

  The resonant knocking sensor 1 of the present embodiment was subjected to a thermal shock test (heated at 130 ° C. for 30 minutes with the sensor 1 being exposed to the air atmosphere, cooled at −40 ° C. for 30 minutes, and again at 130 ° C. for 30 minutes. After the heating process was repeated 1500 times, the loosening of the screwing between the mounting screw member 13 and the screw hole 37 of the metal shell 12 was confirmed. As a result, the loosening of the screwing did not occur. Further, as a result of confirming the output of the resonance type knocking sensor 1 at the knocking frequency, the sensor output was kept high, and the continuity between the mounting screw member and the metal shell was ensured.

Further, the adhesive strength of the conductive adhesive 25 of the present embodiment is 10 N / mm ² or more. By setting the adhesion strength to 10 N / mm ² or more, loosening of the screwing can be further suppressed. The adhesive strength can be measured using a known method such as a die shear test.

Furthermore, the melting point of the conductive adhesive 25 of the present embodiment is 130 ° C. or higher. Since the resonance type knocking sensor 1 is used by being attached to the engine block 200 of the internal combustion engine, the resonance type knocking sensor 1 is easily exposed to a high temperature, and the vicinity of the screw hole 37 of the metal shell may be heated to around 120 ° C. in some cases. In that case, if the melting point of the conductive adhesive 25 is less than 130 ° C., the heat resistance of the conductive adhesive 25 is low, so it deteriorates early and cannot function as an adhesive. There is a risk that loosening of the threaded engagement with the screw hole 37 of the metal shell 12 may occur. However, by setting the melting point of the conductive adhesive 25 to 130 ° C. or higher, the looseness of the screwing between the mounting screw member 13 and the screw hole portion 37 of the metal shell 12 can be further suppressed even when exposed to high temperatures. Can do.
Thus, the resonance type knocking sensor 1 excellent in heat resistance can be provided.

  In this embodiment, the conductive adhesive 25 is provided only in the gap between the screw portion 41 of the mounting screw member 13 and the screw hole portion 37 of the metal shell, but the seating surface between the mounting screw member 13 and the metal shell 12 is provided. Alternatively, a conductive adhesive 25 may be provided. In this case, since the conductive adhesive 25 is interposed not only in the gap between the screw portion 41 and the screw hole portion 37 but also on the seating surface of the mounting screw member 13 and the metal shell 12, the mounting screw member 13 and the main body are more strongly fixed. The metal fitting 12 is fixed. Therefore, loosening of the screwing between the mounting screw member 13 and the screw hole portion 37 of the metal shell 12 can be further suppressed.

In addition, this invention is not limited to this embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.
For example, in the resonant knocking sensor 1 of the above embodiment, the hexagonal portion 24 of the mounting screw member 13 and the bottom portion 36 of the concave portion 31 of the metal shell 12 are seated, but the hexagonal portion 24 and the bottom portion 36 of the concave portion 31 are You do not have to sit down. In this case, the shape of the mounting screw member 13 can be freely changed.

It is a cross-sectional perspective view of the resonance type knocking sensor 1 and its mounting structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Resonance type knocking sensor, 11 ... Vibrating body, 12 ... Metal fitting, 13 ... Mounting screw, 18 ... Connector part, 20 ... Cap, 21 ... Diaphragm, 22 ... Piezoelectric element, 24 ... Flange, 25 ... Conductive adhesive, 37 ... Screw hole, 41 ... Screw, 200 ... Engine block

Claims (4)

A vibrating body composed of a metal diaphragm and a piezoelectric element attached to the diaphragm and having a pair of electrodes;
A bottomed cylindrical shape that accommodates the vibrating body, and a metal shell that is fixed to an attachment object that is set to a reference potential;
A mounting screw member made of metal that extends along the axial direction and supports the vibrating body at one end portion thereof, and the other end portion is screwed into a screw hole portion formed in the bottom portion of the metal shell. Resonance type knocking sensor
The gap between the screw hole and the other end of the mounting screw member is filled with a conductive adhesive,
One of the pair of electrodes is set to the reference potential via the diaphragm, the mounting screw member, the conductive adhesive, and the metal shell, The resonance type knocking sensor according to claim The resonant knocking sensor according to claim 1, wherein the adhesive strength of the conductive adhesive is 10 N / mm ² or more.   The resonance type knocking sensor according to claim 1 or 2, wherein the conductive adhesive has a melting point of 130 ° C or higher. A vibrating body composed of a metal diaphragm and a piezoelectric element attached to the diaphragm and having a pair of electrodes;
A bottomed cylindrical metal shell for housing the vibrator,
A mounting screw member made of metal that extends along the axial direction and supports the vibrating body at one end portion thereof, and the other end portion is screwed into a screw hole portion formed in the bottom portion of the metal shell. In the mounting structure of the resonance type knocking sensor for fixing the resonance type knocking sensor to the mounting object,
The gap between the screw hole and the other end of the mounting screw member is filled with a conductive adhesive,
A mounting structure for a resonance type knocking sensor, wherein one of the pair of electrodes has the same potential as that of the mounting object.

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