JP2004117270A - Resonant knocking sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resonant knocking sensor for preventing an adhesive used in laminating a vibration plate and a piezoelectric element from flowing out into a region around the center of the vibration plate to be fixed to a shell. <P>SOLUTION: The resonant knocking sensor is constructed to detect vibration generated in an internal combustion engine by vibrating the piezoelectric element 12 laminated on the vibration plate 11 via the adhesive 31, together with the vibration plate 11. It has a recessed portion 11a is formed on the single face of the vibration plate 11 in a region being the same as or inside of the inner diameter of the piezoelectric element 12. As a result, the adhesive 31 flowing out when adhering the vibration plate 11 to the piezoelectric element 12 stays in a step portion created by forming the recessed portion 11a in the vibration plate 11, therefore preventing the adhesive 31 from flowing out into the region inside of the recessed portion 11a. It is acceptable that the recessed portion 11a is formed in the vibration plate 11, as a circular grooved portion. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a resonance knocking sensor that detects vibration generated in an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various types of knocking sensors that are attached to an internal combustion engine and detect knocking generated in the internal combustion engine have been developed. One of them is a resonance knocking sensor that detects vibrations generated in an internal combustion engine by vibrating a piezoelectric element adhered to the vibration plate together with the vibration plate, and outputs a detection signal to the outside. (For example, see Patent Document 1)
This type of resonance knocking sensor includes a metal shell for housing the components, an annular piezoelectric element for detecting vibration, and a disk-shaped diaphragm laminated with the piezoelectric element via an adhesive. And The diaphragm is fixed to a predetermined portion of the metal shell by welding, screwing, or the like. Then, by fixing the metal shell to an engine block or the like, the resonance knocking sensor is attached to the internal combustion engine.
[0003]
Here, the bonding between the piezoelectric element and the vibration plate is generally performed by applying an adhesive to the piezoelectric element, then pressing the vibration plate against the piezoelectric element, and drying it with a drier or the like.
In the resonance knocking sensor configured as described above, the vibration of the internal combustion engine is transmitted to the piezoelectric element via the metal shell, and a detection signal generated by the piezoelectric element is output to the outside.
[0004]
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 knocking has occurred.
The size and thickness of the piezoelectric element and the diaphragm are adjusted so that the diaphragm and the piezoelectric element adhered thereto resonate at the knocking frequency inherent to the internal combustion engine, and the maximum output is generated from the piezoelectric element. Have been.
[0005]
[Patent Document 1]
Registered Utility Model No. 1923169
[Problems to be solved by the invention]
As described above, the resonance type knocking sensor detects the vibration of the engine using the diaphragm and the piezoelectric element. When the diaphragm and the piezoelectric element are laminated with an adhesive, the diaphragm and the piezoelectric element are stacked. The adhesive that has overflowed from between the element and the diaphragm is an area inside the inner diameter of the through-hole of the piezoelectric element on the diaphragm and near the center for fixing to the metal shell (hereinafter, referred to as “the center of the diaphragm”). Department).
[0007]
Here, “the area on the diaphragm that is inside the inner diameter of the through hole of the piezoelectric element and near the center for fixing to the metal shell” is the diaphragm on which the piezoelectric elements are laminated. , A region cut by a virtual plane extending in the stacking direction along the inner wall surface of the piezoelectric element forming the through hole.
[0008]
When the adhesive flows out to the center of the diaphragm, fixing failure may occur between the diaphragm and the metal shell.
For example, in the method in which the diaphragm and the metal shell are fixed by welding, the center of the vibration plate on which the piezoelectric element is not laminated and the distal end face of the fixing portion of the metal shell are overlapped, and the piezoelectric element is laminated. A welding electrode connected to a welding power source is applied to the center of the diaphragm and the metal shell, and welding is performed by applying a current from the welding power source while applying pressure to the distal end surface of the metal shell fixing part by pressing the diaphragm. Is At this time, if an adhesive exists at the center of the diaphragm, the flow of current is obstructed by the adhesive, so that welding failure such as spatter occurs, and fixing failure occurs between the diaphragm and the metal shell. There was something.
[0009]
Further, for example, in a method of fixing the diaphragm and the metal shell with screws, a through hole formed in the center of the diaphragm is inserted into a screw portion protruding from a fixing portion of the metal shell, and a nut is inserted from above the diaphragm. Screwing is performed. At this time, if the adhesive is present at the center of the diaphragm, a gap is generated between the nut and the diaphragm, the screw cannot be sufficiently screwed, and a fixing failure between the diaphragm and the metal shell occurs. Occurred.
[0010]
As described above, when the fixing failure occurs between the diaphragm and the metal shell, there is a problem that the sensor characteristics are deteriorated, and in some cases, the sensor cannot be used as a product, and the yield is deteriorated. .
Therefore, in the present invention, there is provided a resonance type knocking sensor capable of preventing the adhesive from flowing out to the center of the diaphragm in order to eliminate the above-described fixing failure between the diaphragm and the metal shell. With the goal.
[0011]
Means for Solving the Problems and Effects of the Invention
The invention according to claim 1, which has been made to achieve the above object, is a piezoelectric element which is laminated on one side of the diaphragm via an adhesive and has a through hole in a thickness direction. And a fixing portion for fixing an area inside the inner diameter of the through hole in the diaphragm on which the piezoelectric element is laminated, and in a state where the diaphragm is fixed to the fixing portion, the internal combustion engine A resonance type knocking sensor including a fixable metal shell, on one surface of the vibration plate on which the piezoelectric element is stacked, in the same region as the inside diameter of the through hole or inside the inside of the inside diameter, It is characterized in that a recess is formed.
[0012]
As a result, the adhesive that has flowed out when the vibration plate and the piezoelectric element are bonded to each other is accumulated in a step formed by providing the concave portion in the vibration plate. Therefore, it is possible to prevent the adhesive from flowing out to a region inside the stepped portion. In addition, if the diaphragm is fixed to the fixing portion of the metal shell in a region inside the stepped portion, it is possible to reliably prevent a fixing failure between the diaphragm and the metal shell.
[0013]
As described above, since the fixing failure between the diaphragm and the metal shell can be prevented, the deterioration of the sensor characteristics can be suppressed, the yield can be improved, and the manufacturing cost can be reduced.
In order to prevent the adhesive from flowing out to the area inside the inner diameter of the through hole of the piezoelectric element which is a vibration plate, the diaphragm has the inner diameter of the through hole as described in claim 1. The concave portion may be formed in the same region or in a region inside the inner diameter of the through hole. However, as described in claim 2, on one surface of the diaphragm on which the piezoelectric element is laminated, the inner diameter of the through hole is Alternatively, an annular groove may be formed in a region inside the inner diameter.
[0014]
In other words, when the annular groove is formed in the diaphragm, the fixing failure between the diaphragm and the metal shell can be prevented, as in the case of the first aspect. The effect of improving the yield and reducing the manufacturing cost can be obtained.
[0015]
In addition, in the case where the annular groove is formed in the diaphragm, unlike the case where the concave portion is formed in the diaphragm, not only the step on the outer peripheral side of the groove generated when the groove is formed, but also the inner peripheral side of the groove. Since the adhesive can be stored even at the stepped portion, it is possible to more effectively prevent the adhesive from flowing out to the center of the diaphragm.
[0016]
The shape of the vibration plate and the piezoelectric element may be any shape, but more preferably, the vibration plate has a disk shape and the piezoelectric element has an annular shape. It is preferable that the diaphragm and the piezoelectric element are stacked with their central axes aligned.
The diaphragm has a disk shape and the piezoelectric element has an annular shape, so that the weight of the adhesive overflowing between the diaphragm and the piezoelectric element is almost uniform regardless of the location near the inner diameter of the through hole. Therefore, the influence of the weight of the adhesive on the vibration characteristics can be reduced.
[0017]
In addition, since the shape of the vibration plate and the piezoelectric element is circular, the adjustment of the resonance frequency is facilitated, and the output characteristics of the resonance knocking sensor can be improved.
It is preferable that the recess has a depth of 0.025 mm or more. Preferably, the groove has a depth of 0.015 mm or more and a width of 0.1 mm or more. With such recesses and grooves, it is possible to reliably prevent the adhesive from flowing out to the center of the diaphragm. However, in consideration of the influence on the strength and vibration characteristics of the diaphragm, it is preferable that the depth of the concave portion and the groove is not more than 以下 of the thickness of the diaphragm.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 is a sectional view of a resonance knocking sensor according to a first embodiment to which the present invention is applied. The structure of the resonance knocking sensor 1 will be described below with reference to FIG.
[0019]
The resonance-type knocking sensor 1 is stacked on the metal shell 13 for accommodating components and transmitting vibration from the internal combustion engine, a disk-shaped diaphragm 11 made of, for example, 42 nickel, and the diaphragm 11. For example, an annular piezoelectric element 12 made of, for example, lead zirconate titanate for generating a detection signal, a lead wire 14 for transmitting the detection signal generated from the piezoelectric element 12 to the outside, a connection portion 15, and a terminal 16, a cap 17 for protecting components from external impact and water, and an O-ring 18. Note that electrodes are formed on both sides in the thickness direction of the piezoelectric element.
[0020]
The metal shell 13 is formed in a bowl shape so that components can be housed therein, and has a fixing portion 13b for welding the diaphragm 11 at the center of the bottom. The piezoelectric element 12 is laminated on the diaphragm 11 via an adhesive (for example, an acrylic adhesive). The diaphragm 11 has the piezoelectric element 12 adhered thereto, and the central portion of the diaphragm on which the piezoelectric element 12 is not adhered is fixed to the fixing portion 13b by welding.
[0021]
The output from the piezoelectric element 12 is taken out from the terminal 16 via the lead wire 14. The connection portion 15 between the electrode of the piezoelectric element 12 and the lead wire 14 and the connection portion 15 between the lead wire 14 and the terminal 16 are all joined by soldering, and are covered with silicon from above. To prevent disconnection due to vibration.
[0022]
A cap 17 is inserted into the opening 13c of the metal shell 13 so as to protect components such as the vibration plate 11 and the piezoelectric element 12, and a gap between the metal shell 13 and the cap 17 is O. Sealing is performed using the elastic force of the ring 18. The cap 17 has a connector portion 17a formed on an upper portion, and the terminal 16 protrudes from the connector portion 17a.
[0023]
The resonance-type knocking sensor 1 configured as described above is attached to an engine block or the like of an internal combustion engine (not shown) using a male screw portion 13a provided at a lower portion of the metal shell 13.
In the present embodiment (first embodiment), in the resonance type knocking sensor 1, as shown in FIG. 2, a region inside the inner diameter of the piezoelectric element 12 Is provided with a circular concave portion 11a (0.05 mm in depth).
[0024]
2A is a top view of the diaphragm 11, FIG. 2B is a cross-sectional view of the diaphragm 11, and FIG. 2C is an enlarged view when the diaphragm 11 and the piezoelectric element 12 are bonded.
The bonding between the vibration plate 11 and the piezoelectric element 12 will be described with reference to FIG. 2C, which is an enlarged view when the vibration plate 11 and the piezoelectric element 12 are bonded.
[0025]
An adhesive 31 is applied to one surface of the piezoelectric element 12, and the diaphragm 11 and the piezoelectric element 12 are pressed against each other, so that the diaphragm 11 and the piezoelectric element 12 are bonded.
At this time, the adhesive 31 may flow out toward the center of the diaphragm. However, the adhesive 31 accumulates on the inner wall surface of the piezoelectric element 12 and the step formed by forming the concave portion 11a on the diaphragm 11, thereby preventing the adhesive 31 from flowing out to the center of the diaphragm. Can be. Therefore, by using the vibration plate 11 for the resonance knocking sensor 1, it is possible to eliminate poor welding between the vibration plate 11 and the metal shell 13.
[0026]
As a result, a decrease in sensor characteristics can be suppressed, the yield of products can be improved, and manufacturing costs can be reduced.
Although the adhesive 31 used in the present embodiment is insulative, the lower surface of the piezoelectric element 12 (the surface on the side of the vibration plate 11) and the vibration plate 11 have sufficient electrical conduction by many point contacts (not shown). Since it is secured and the adhesive 31 is present so as to fill the gap between the point contacts, an output can be taken out from the resonance type knocking sensor 1 using the metal shell 13 and the terminal 16.
[0027]
Also, a resonance type knocking sensor having a through hole in the center of the diaphragm 11 for inserting a fixing member such as a bolt and fixing the diaphragm 11 and the metal shell 13 by screws is also used. The use of the vibration plate 11 can prevent the adhesive 31 from flowing out to the center of the vibration plate, and can eliminate defective fixing between the vibration plate 11 and the metal shell 13.
[0028]
In addition, the diaphragm 11 used in the present embodiment is formed with the circular concave portion 11a, but the shape of the concave portion 11a is not limited to a circle, and may be a waveform or a polygon.
[Second embodiment]
Next, a second embodiment will be described.
[0029]
The resonance type knocking sensor of the present embodiment is different from the resonance type knocking sensor 1 of the first embodiment only in that only the diaphragm 11 is different. Accordingly, here, the same portions as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and only the diaphragm 11 will be described in detail.
[0030]
In the present embodiment (second embodiment), in the resonance type knocking sensor 1, as shown in FIG. 3, a region inside the inner diameter of the piezoelectric element 12 is located on the side of the diaphragm 11 on which the piezoelectric element 12 is stacked. Is provided with an annular groove 11b (depth 0.04 mm, width 0.2 mm).
[0031]
As in FIG. 2, FIG. 3A is a top view of the diaphragm 11, FIG. 3B is a cross-sectional view of the diaphragm 11, and FIG. 3C is an enlarged view when the diaphragm 11 and the piezoelectric element 12 are bonded. The figures are shown respectively.
When the annular groove 11b is formed in the diaphragm 11 as in the present embodiment, the adhesive 31 can be prevented from flowing to the center of the diaphragm, as in the case of the first embodiment. Poor fixing between the diaphragm 11 and the metal shell 13 can be prevented.
[0032]
In addition, when the annular groove 11b is formed in the diaphragm 11, unlike the case where the concave portion 11a is formed in the diaphragm 11, the outer peripheral side (piezoelectric element side) generated when the annular groove 11b is formed. Since the adhesive 31 can be accumulated not only at the step portion but also at the step portion on the inner peripheral side (center side), it is possible to more effectively prevent the adhesive 31 from flowing out to the center portion of the diaphragm.
[0033]
As a result, a decrease in sensor characteristics can be suppressed, the yield of products can be improved, and manufacturing costs can be reduced.
As in the case of the diaphragm 11 used in the first embodiment, an insertion hole for inserting a fixing member such as a bolt is provided at the center of the diaphragm 11, and the diaphragm 11 and the metal shell 13 are fixed by screws. Even in the case of a fixed-type resonance knocking sensor, the use of the diaphragm 11 can eliminate a fixing failure between the diaphragm 11 and the metal shell 13.
[0034]
Further, the diaphragm 11 used in the present embodiment is formed with the annular groove 11b. However, the shape of the groove 11b is not limited to an annular shape. You may.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a resonance knocking sensor according to an embodiment.
FIG. 2 is an explanatory diagram showing a shape of a diaphragm having a concave portion according to the embodiment.
FIG. 3 is an explanatory diagram illustrating a shape of a diaphragm having a groove according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Resonance type knocking sensor, 11 ... Vibration plate, 11a ... Concave part, 11b ... Annular groove part, 12 ... Piezoelectric element, 13 ... Metal shell, 13a ... Male screw part, 13b ... Fixed part, 13c ... Opening part, 14 ... Lead wire, 15 connection section, 16 terminal, 17 cap, 17a connector section, 18 O-ring, 31 adhesive.

Claims (3)

A diaphragm,
A piezoelectric element laminated on one side of the vibration plate via an adhesive and having a through hole in a thickness direction;
A fixing portion for fixing an area inside the inner diameter of the through-hole in the vibration plate on which the piezoelectric element is laminated, and which can be fixed to an internal combustion engine in a state where the vibration plate is fixed to the fixing portion; Metal fittings,
A resonance knocking sensor having
A resonance type knocking sensor, wherein a concave portion is formed on one surface of the vibration plate on a side on which the piezoelectric element is laminated, in a region equal to or inside the inner diameter of the through hole. A diaphragm,
A piezoelectric element laminated on one side of the vibration plate via an adhesive and having a through hole in a thickness direction;
A fixing portion for fixing an area inside the inner diameter of the through-hole in the vibration plate on which the piezoelectric element is laminated, and which can be fixed to an internal combustion engine in a state where the vibration plate is fixed to the fixing portion; Metal fittings,
A resonance knocking sensor having
A resonance type knocking sensor, wherein an annular groove is formed on one surface of the vibration plate on the side on which the piezoelectric element is stacked, in a region equal to or inside the inside diameter of the through hole. The vibration plate has a disk shape, and the piezoelectric element has an annular shape,
3. The resonance knocking sensor according to claim 1, wherein the vibration plate and the piezoelectric element are stacked with their respective central axes aligned. 4.

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