JP2010071754A - Knocking sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knocking sensor that allows reduction in the usage amount of metallic material of the part in an output terminal that comes into contact with a piezoelectric element. <P>SOLUTION: The first output terminal 21 comprises an annular insulated section 33 having an electrical insulation property, and a conductor section 35 having conductivity that extends from the insulated section 33. The insulated section 33 is an annular member, and a part of it is provided with a notch section 37 with which the tip of the conductor section 35 is engaged. The conductor section 35 is a plate-like member, comprising a non-annular electrode section 39 coming into contact with the piezo-electric element 17, and a terminal section 41, extending from the electrode section 39 toward the outside of the piezo-electric element 17. The electrode section 39 is not annular in shape but rather is different from the piezo-electric element 17 or insulated section 33, and is set to a dimension of 1/3 or less of the full circumference of the insulated section 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a knocking sensor such as a non-resonant knocking sensor that uses a piezoelectric element and detects vibration generated in an internal combustion engine, for example.

  Conventionally, for example, a knock sensor using a piezoelectric element has been developed to detect knock occurring in an internal combustion engine. As this type of knocking sensor, there is a non-resonant knocking sensor that holds a piezoelectric element pressed inside by a weight or the like, detects vibration generated in the internal combustion engine by the piezoelectric element, and outputs a detection signal to the outside.

  In general, the knocking sensor described above includes a metal support member having a cylindrical main body portion and a flange portion on the outer periphery of the main body portion, and an annular piezoelectric element and a weight are fitted on the support member. ing. A pair of output terminals are disposed on both sides of the piezoelectric element in the plate thickness direction in order to output detection signals generated in the piezoelectric element to the outside.

  The knocking sensor configured as described above is attached to the cylinder head of the internal combustion engine by a bolt inserted into the main body of the support member. As a result, the weight and the piezoelectric element constituting the knocking sensor vibrate together with the vibration generated in the internal combustion engine, and as a result, a detection signal having a waveform similar to the vibration generated in the internal combustion engine is output from the output terminal. It is output to the outside (see Patent Document 1).

This patent document 1 discloses an annular electrode plate that comes into contact with a piezoelectric element as an output terminal, and the electrode plate is not directly in contact with a collar or a weight (that is, not electrically short-circuited). In addition, an insulating powder is sprayed on one surface (surface opposite to the piezoelectric element) of the electrode plate to form an insulating layer.
JP 2004-251792 A

  However, since the knocking sensor described in Patent Document 1 uses an annular electrode plate, there is a problem that a large amount of metal material such as brass, which is a material of the electrode plate, is used. In other words, if the amount of metal material used is large, there is a problem that it cannot contribute to resource saving and leads to an increase in cost.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a knocking sensor that can reduce the amount of metal material used in a portion of the output terminal that contacts the piezoelectric element. And

  (1) The invention according to claim 1, which is made to achieve the above object, is a knocking sensor including an annular piezoelectric element and output terminals arranged on both sides in the thickness direction of the piezoelectric element. The output terminal includes an annular insulating portion and a conductor portion extending from the insulating portion. The conductor portion is integrated with the insulating portion and contacts the piezoelectric element, and the electrode portion. And a terminal portion extending toward the outside of the piezoelectric element.

  In the present invention, the conductor portion of the output terminal is provided with a non-circular electrode portion that is in contact with the piezoelectric element and integrated with the insulating portion. Can be reduced. Thereby, it contributes to resource saving and can aim at cost reduction.

  In other words, conventionally, since the electrode terminal having a planar shape (that is, an annular shape) similar to the annular piezoelectric element was provided as the output terminal, a large amount of metal material was used. For example, since a non-circular electrode portion such as an arc is used, the amount of metal material used can be reduced.

Hereinafter, each configuration of the present invention will be described.
-As a material of the said piezoelectric element, PZT is mentioned, for example.
The material of the conductive portion of the output terminal, and hence the electrode portion and the terminal portion, for example, is brass.

-As a material of an insulation part, polybutyl terephthalate (PBT), nylon 66, and polyethylene terephthalate (PET) are mentioned, for example.
(2) The invention of claim 2 is characterized in that the insulating portion is formed by injection molding and integrated with the electrode portion.

According to the present invention, a configuration in which an electrode portion and an insulating portion are integrated can be easily realized.
(3) The invention of claim 3 is characterized in that the electrode portion is 1/3 or less of the entire circumference of the insulating portion.

  In this invention, since an electrode part is 1/3 or less of the perimeter of an insulation part, a metal material can be reduced significantly. Here, the entire circumference indicates one circumference when the annular insulating portion is viewed from the axial direction.

In addition, it is suitable for an electrode part that it is 1/30 or more of the perimeter of an insulation part because an electrode part and an insulation part will be integrated firmly.
(4) In the invention of claim 4, the exposed surface of the electrode portion on the piezoelectric element side and the surface of the insulating portion on the piezoelectric element side around the electrode portion are flush with each other. And

In the present invention, since the surface of the electrode portion on the piezoelectric element side and the surface of the insulating portion on the piezoelectric element side are flush, the electrode portion and the insulating portion can be brought into close contact with the surface of the piezoelectric element.
(5) In the invention of claim 5, the insulating part has a shape in which a disk-like plate-like part and a cylindrical cylindrical part protruding in the thickness direction of the plate-like part are integrally formed. It is characterized by that.

  In this invention, since the cylindrical part is provided in the plate | board thickness direction of the insulation part, this cylindrical part can be arrange | positioned inside cyclic | annular piezoelectric elements. Therefore, when the support member is made of metal and the electrode portion extends to reach the inner peripheral surface of the insulating portion, the metal powder is also made up of the (metal) support member and the piezoelectric element. Even if it exists between the output terminal and the output terminal, insulation between the support member and the electrode portion of the output terminal can be easily ensured.

(6) The invention of claim 6 is characterized in that the insulating portion and the electrode portion are provided with a retaining mechanism for preventing the electrode portion from falling off the insulating portion.
In the present invention, since the retaining mechanism is provided, it is possible to prevent the electrode portion from falling off from the insulating portion. As the retaining mechanism, for example, a configuration in which the insulating portion and the electrode portion are locked to each other by a concavo-convex shape can be employed.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
a) First, a schematic configuration of a non-resonant type knocking sensor (hereinafter, simply referred to as “knocking sensor”) of the present embodiment will be described with reference to FIGS.

1 shows the appearance of the knocking sensor, FIG. 2 is a cutaway view of the knocking sensor, and FIG. 3 is an exploded view of the internal structure of the knocking sensor.
As shown in FIG. 1, the knocking sensor 1 of the present embodiment is covered with a case 3 made of a synthetic resin (for example, nylon 66). The case 3 includes a cylindrical element storage portion 5 whose upper portion is formed in a tapered shape, and a connector portion 7 for connecting a connector from an ignition timing control device (not shown).

  2 and 3, the knocking sensor 1 includes a support member 9 made of a metal material (for example, SWCH35K), and the support member 9 has a cylindrical shape having an insertion hole 11 for inserting a bolt. A main body 13 and a flange 15 projecting outward from the outer peripheral wall on one end side (lower side in FIG. 2) of the main body 13 are provided.

  An annular shape (cylindrical shape) made of piezoelectric ceramics (for example, PZT) fitted on the outer peripheral side of the main body portion 13 on one surface (upper surface in FIG. 2) side of the thickness direction (axial direction) of the flange portion 15 of the support member 9. The piezoelectric element 17 is placed.

  In addition, a cylindrical weight 19 made of a metal material (for example, SPCC) that is fitted on the outer peripheral side of the main body portion 13 is placed on one side (the upper surface side in FIG. 2) of the piezoelectric element 17 in the thickness direction. Yes.

  Further, as will be described in detail later, a first output terminal 21 is disposed between the flange portion 15 and the piezoelectric element 17, and a first output terminal 21 is disposed between the weight 19 and the piezoelectric element 17. The second output terminal 23 is disposed. Hereinafter, the piezoelectric element 17 and the output terminals 21 and 23 are referred to as a piezoelectric element portion 25.

The support member 9 is made of a metal material (for example, SK5M), and an annular leaf spring 27 is attached to press the weight 19 in the direction of the flange 15 (downward in the figure).
Further, a nut 29 is disposed on the upper portion of the leaf spring 27, and the nut 29 is screwed into a screw portion 31 on the outer periphery of the main body portion 13.

  Accordingly, when the nut 29 is tightened, the leaf spring 27 is pressed in the direction of the flange portion 15 (downward in the figure), so that the piezoelectric element 17 and the weight 19 are supported together with the output terminals 21 and 23 by the leaf spring 27. It is fixed to the member 9.

b) Next, the first and second output terminals 21 and 23 which are the main parts of the present embodiment will be described with reference to FIGS.
4 shows the first output terminal 21, FIG. 5 shows the retaining mechanism, FIG. 6 shows the second output terminal 23, and FIGS. 7 and 8 show the piezoelectric element portion 25.

  As shown in FIG. 4, the first output terminal 21 includes an annular insulating portion 33 made of, for example, PBT having electrical insulation, and a conductor portion 35 made of, for example, brass having electrical conductivity extending from the insulating portion 33. It is configured. The first output terminal 21 is formed by integrally forming the insulating portion 33 and the conductor portion 35 (specifically, the electrode portion 39) by forming the insulating portion 33 by injection molding.

The insulating portion 33 is an annular member having an outer diameter of 23 mm, an inner diameter of 15 mm, and a thickness of 1 mm, for example, and a cutout portion 37 into which the tip of the conductor portion 35 is fitted is formed in a part thereof.
The cutout portion 37 has a side parallel to the piezoelectric element 17 (the upper surface side in FIG. 4B) opened in a substantially parallelogram shape, and the outer peripheral side of the insulating portion 33 opened in a trapezoidal shape. That is, as shown in FIG. 5 (section AA ′ in FIG. 4A), the notch 37 is a long space having a trapezoidal cross section.

  On the other hand, as shown in FIG. 4A, the conductor portion 35 includes a non-circular electrode portion 39 that contacts the piezoelectric element 17 and a terminal portion 41 that extends from the electrode portion 39 toward the outside of the piezoelectric element 17. The plate-like member is arranged in parallel with a predetermined diameter direction (the left-right direction in the figure) so as to be slightly displaced from the center of the insulating portion 33.

Among these, the electrode part 39 is not annular like the piezoelectric element 17 and the insulating part 33, but is set to a size of 1/3 or less of the entire circumference of the insulating part 33 (here, about 1/30 of the circumference). ing.
Moreover, the electrode part 39 is a substantially rectangular shape (thickness is 0.3 mm) with the tip cut obliquely, and the cross-sectional shape thereof fits in the notch part 37 of the insulating part 33 without a gap as shown in FIG. It is a trapezoidal shape.

  Further, the surface of the electrode portion 39 (which corresponds to the upper side of the trapezoid) on the piezoelectric element 17 side is exposed to the outside from the insulating portion 33, and the exposed surface and the surface of the surrounding insulating portion 33 are exposed. Are coplanar (so-called flush).

  The trapezoidal notch 37 and the trapezoidal electrode part 39 fitted thereto, that is, the structure in which the notch 37 and the electrode part 39 are engaged with each other, prevents the electrode part 39 from coming off to the upper surface side of the figure. A retaining mechanism 43 is provided to prevent this.

  On the other hand, as shown in FIG. 4B, the terminal portion 41 is a long plate bent at four locations, and the direction of the connector portion 7 is such that the tip thereof extends outside the piezoelectric element 17. It extends diagonally upward to match.

  Further, as shown in FIG. 6, the second output terminal 23 has substantially the same structure as the first output terminal 21, and an annular insulating portion 45 having electrical insulation and a conductive property extending from the insulating portion 45. It is comprised from the conductor part 47 which has. Note that the second output terminal 23 is also integrally formed with the insulating portion 45 and the conductor portion 47 by injection molding.

The insulating portion 45 is an annular member having the same dimensions as the first output terminal 21, and a cutout portion 49 having the same shape (as the first output terminal 21) is formed in a part thereof.
On the other hand, the conductor portion 47 is also composed of a non-annular electrode portion 51 in contact with the piezoelectric element 17 and a terminal portion 53 extending from the electrode portion 51 toward the outside of the piezoelectric element 17 in substantially the same manner as the first output terminal 21. The insulating part 51 is arranged in parallel with a predetermined diameter direction. In addition, this electrode part 51 is also set to the dimension of 1/3 or less (here 1/30 of the circumference) of the perimeter of the insulating part 51.

Further, the surface of the electrode portion 51 on the piezoelectric element 17 side is also flush with the surface of the insulating portion 51, similarly to the first output terminal 21, and a similar retaining mechanism 55 is also provided.
The terminal portion 53 is bent at two points in the middle thereof (unlike the first output terminal 21), and the tip thereof extends to the outside of the piezoelectric element 17.

  Therefore, in the piezoelectric element part 25 provided with both the output terminals 21 and 23 mentioned above, as shown in FIG. 7, both the output terminals 21 and 23 are arrange | positioned so that each insulation part 33 and 45 may become parallel. At the same time, the electrode portions 39 and 51 are disposed so that the exposed portions of the electrode portions 39 and 51 are in contact with the piezoelectric element 17, that is, the electrode portions 39 and 51 are directed inward.

  Specifically, as shown in FIG. 8, the first output terminal 21 is disposed on the lower side of the piezoelectric element 17 so that the exposed portion of the electrode portion 39 is on the upper side. Thereby, the terminal portion 41 is arranged so that the position (height) is aligned with the terminal portion 53 of the second output terminal 23 and the tip thereof extends obliquely upward.

  On the other hand, the second output terminal 23 is disposed on the upper side of the piezoelectric element 17 so that the exposed portion of the electrode portion 51 faces downward. Thereby, the terminal part 53 is arrange | positioned diagonally upward (it is the same direction as the terminal part 41 of the 1st output terminal 21).

  The knocking sensor 1 configured as described above has a cylinder head (not shown) of an internal combustion engine (not shown) by a bolt (not shown) inserted into an insertion hole 11 formed in the main body 13 of the support member 9 as in the conventional device. And used in the same manner as a conventional apparatus.

c) Next, a method for assembling the knocking sensor 1 of the present embodiment will be briefly described.
First, an injection mold (not shown) (for forming the insulating portions 33 and 45) is included in advance so as to include the distal end sides (electrode portions 39 and 51 side) of the conductor portions 35 and 47 of the output terminals 21 and 23. ), And a liquid resin member (insulating material) is injected and solidified.

  In this injection molding, in the completed output terminals 21 and 23, the surface of one of the electrode portions 39 and 51 (the surface on the piezoelectric element 17 side) is exposed from the insulating portions 33 and 45. The exposed surface is kept in close contact with the mold.

Thereby, both the output terminals 21 and 23 in which the conductor portions 35 and 47 and the insulating portions 33 and 45 are integrated are manufactured.
As shown in FIG. 2, the first output terminal 21, the piezoelectric element 17, the second output terminal 23, and the weight 19 are placed on the flange portion 15 so as to be fitted to the outer peripheral side of the main body portion 13 of the support member 9. Are placed in order. At this time, the first output terminal 21, the piezoelectric element 17, and the second output terminal 23 are assembled with the output terminals 21 and 23 in parallel (see FIG. 7A).

Next, a plate spring 27 is press-fitted into the main body 13, and a nut 29 is fitted on the plate spring 27 and tightened to press the plate spring 27.
As a result, each component (piezoelectric element 17, weight 19, both output terminals 21 and 23) is fixed to the support member 9 while being pressed toward the flange 15 by the leaf spring 27.

  Thereafter, the support member 9 and the component parts are surrounded by an injection mold (not shown), and a liquid resin member (insulating material) is injected and solidified so as to cover the component parts, thereby forming the case 3. . Thereby, knocking sensor 1 is manufactured.

  d) In this manner, in the knocking sensor 1 of the present embodiment, the conductor portions 35 and 47 of the output terminals 21 and 23 are in contact with the piezoelectric element 17 and are non-annularly integrated with the insulating portions 33 and 45. Since the electrode portions 39 and 51 are provided, that is, the electrode portions 39 and 51 are 1/3 or less of the entire circumference of the insulating portions 33 and 45, the metal used for the electrode portions 39 and 51 compared to the conventional case. The amount of material used can be reduced. Thereby, it contributes to resource saving and can aim at cost reduction.

Moreover, in this embodiment, since the said insulation parts 33 and 45 and the electrode parts 39 and 51 are integrated by injection molding, each output terminal 21 and 23 can be produced easily.
Furthermore, in the present embodiment, the exposed surfaces of the electrode portions 39 and 51 on the piezoelectric element 17 side and the surfaces of the insulating portions 33 and 45 on the piezoelectric element 17 side are in the same plane. The insulating portions 33 and 45 can be brought into close contact with the surface of the piezoelectric element 17. Thereby, knocking can be detected with high accuracy.

In addition, in the present embodiment, since the output terminals 21 and 23 are provided with the retaining mechanisms 43 and 55, the electrode portions 39 and 51 can be prevented from falling off from the insulating portions 33 and 45.
[Second Embodiment]
Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be simplified.

The knocking sensor of the present embodiment is particularly different from the knocking sensor of the first embodiment in the configuration of the insulating portion.
As shown in FIG. 9, the knocking sensor 61 of the present embodiment is provided with a support member 67 including a main body portion 63 and a flange portion 65 in substantially the same manner as in the first embodiment, and on the flange portion 65. The first output terminal 69, the piezoelectric element 71, the second output terminal 73, and the weight 75 are sequentially placed, and are integrally fixed by a leaf spring 77 and a nut 79.

  In particular, in the present embodiment, as shown in FIG. 10, the first output terminal 69 includes an annular insulator 81 and a conductor portion 83 extending from the insulator 81, and the insulator 81 has a disk shape. It consists of a plate-like portion 85 and a cylindrical tubular portion 87. That is, the insulating part 81 has a structure in which the cylindrical part 87 is erected on the inner peripheral end of the plate-like part 85.

  This embodiment has the same effect as the first embodiment, and the cylindrical portion 87 is disposed between the main body portion 63 and the piezoelectric element 71, so that the insulation with the support member 67 is easily ensured. There is an advantage that you can.

  In particular, although not shown, for example, when the electrode portion of the second output terminal 73 extends to reach the inner peripheral surface of the insulating portion, or at that time, the metal powder is transferred to the support member 67 and the piezoelectric element 71 or the like. Even when it exists between the 2nd output terminal 73, the insulation between the support member 67 and the electrode part of the 2nd output terminal 73, etc. can be ensured easily.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various forms can be taken as long as they belong to the technical scope of the present invention.

It is a front view which shows the external appearance of the knocking sensor of 1st Embodiment. It is sectional drawing of the knocking sensor of 1st Embodiment. It is explanatory drawing which decomposes | disassembles and shows the internal structure of the knocking sensor of 1st Embodiment. (A) is the top view seen from the electrode part side of the 1st output terminal, (b) is the front view. It is A-A 'sectional drawing of Fig.4 (a). (A) is the top view seen from the electrode part side of the 2nd output terminal, (b) is the front view. (A) is a top view of a piezoelectric element part, (b) is the front view. It is a perspective view which shows a piezoelectric element part. It is sectional drawing of the knocking sensor of 2nd Embodiment. (A) is a top view of a 1st output terminal, (b) is explanatory drawing which fractures | ruptures and shows the front surface partially.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 61 ... Knocking sensor 17, 71 ... Piezoelectric element 21, 23, 69, 73 ... (first, second) output terminal 33, 45, 81 ... Insulating part 35, 47, 83 ... Conductor part 39, 51 ... Electrode Part 41, 53 ... Terminal part 43, 55 ... Retaining mechanism 85 ... Plate-like part 87 ... Cylindrical part

Claims (6)

An annular piezoelectric element;
Output terminals disposed on both sides of the piezoelectric element in the thickness direction;
In the knocking sensor with
The output terminal includes an annular insulating portion and a conductor portion extending from the insulating portion,
The knocking sensor, wherein the conductor portion includes a non-circular electrode portion integrated with the insulating portion and in contact with the piezoelectric element, and a terminal portion extending from the electrode portion toward the outside of the piezoelectric element. .   The knocking sensor according to claim 1, wherein the insulating portion is formed by injection molding and integrated with the electrode portion.   The knocking sensor according to claim 1 or 2, wherein the electrode part is 1/3 or less of the entire circumference of the insulating part.   The surface exposed on the piezoelectric element side of the electrode portion and the surface on the piezoelectric element side around the electrode portion of the insulating portion are flush with each other. The knocking sensor described in 1.   The said insulating part is a shape in which the disk-shaped plate-shaped part and the cylindrical cylindrical part which protrudes in the thickness direction of this plate-shaped part are formed integrally. The knocking sensor in any one of.   The knocking sensor according to any one of claims 1 to 5, wherein the insulating part and the electrode part are provided with a retaining mechanism for preventing the electrode part from falling off the insulating part.

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