JP7027251B2 - Knocking sensor - Google Patents

Description

The present invention relates to a knocking sensor using a piezoelectric element.

A knocking sensor that detects a knocking phenomenon of an internal combustion engine of an automobile or the like is known, and the retard angle control of the ignition timing of the spark plug is performed according to the detection of the knocking sensor.
As the knocking sensor described above, a so-called center hole type non-resonant type knocking sensor having a mounting hole for mounting on a cylinder block or the like of an internal combustion engine at the center is known. This knocking sensor is provided with a main metal fitting having a cylindrical portion and a flange portion located at one end of the tubular portion, and an annular insulating member, a piezoelectric element, and a weight are provided on the outer periphery of the tubular portion in order from the flange portion side. And a nut is fitted. Then, the weight is locked by screwing a nut into the male screw portion on the outer peripheral surface of the tubular portion, and the piezoelectric element is sandwiched and fixed between the flange portion and the weight. Further, the knocking sensor is configured by covering the entire internal component in which the insulating member, the piezoelectric element, the weight, etc. are assembled to the main metal fitting with the resin. The inner surface of the tubular portion is the mounting hole described above (Patent Document 1).
Further, there is also disclosed a technique of plastically deforming and projecting the outer peripheral surface of the tubular portion to lock the weight to the tubular portion (Patent Document 2).

Japanese Unexamined Patent Publication No. 2010-101696 Japanese Patent No. 6175149

By the way, in recent years, improvement of the detection output of the knocking sensor has been required, and as a countermeasure, it is possible to increase the vibration by increasing the weight of the weight or to increase the detection value by including lead in the material of the piezoelectric element. Conceivable.
However, these measures are not sufficient when higher output is required.
Therefore, an object of the present invention is to provide a knocking sensor with improved detection output.

In order to solve the above problems, the knocking sensor according to the first aspect of the present invention extends in the axial direction, is located on the cylindrical portion and one end side of the tubular portion, and protrudes outward in the circumferential direction of the tubular portion. A main metal fitting having a flange portion, an annular weight having a top surface on the side opposite to the side facing the flange portion, and an annular weight fitted on the outer periphery of the tubular portion. A knocking sensor including an annular piezoelectric element sandwiched between the flange portion and the weight and an insulator interposed between the flange portion and the piezoelectric element, and is an outer peripheral surface of the cylindrical portion. Is provided with a protruding portion that protrudes from the inner surface of the tubular portion toward the outside in the circumferential direction while being plastically deformed, and is in contact with the top surface of the weight directly or via another member to lock the weight. The tubular portion has an extension portion extending in the axial direction between the protrusion portion and the flange portion, and the extension portion has a maximum thickness portion having a maximum thickness and a thickness greater than the maximum thickness. A thin thin-walled portion is formed , and a synthetic resin is filled between the extended portion and the weight .

According to this knocking sensor, a maximum thickness portion and a thin portion thinner and less rigid are interposed in the extending portion between the protruding portion, which is the fixed position of the weight of the tubular portion, and the flange portion. However, when the weight vibrates, the thin portion bends and the vibration is amplified, so that the detection output can be improved without increasing the weight of the weight. Further, it is possible to improve the output of the sensor using a low output piezoelectric element (for example, a lead-free piezoelectric element).

Further, the knocking sensor of the second aspect of the present invention extends in the axial direction and has a cylindrical portion and a flange portion located on one end side of the tubular portion and projecting outward in the circumferential direction of the tubular portion. The main metal fitting to be held, an annular weight fitted on the outer periphery of the tubular portion and having a top surface on the side opposite to the side facing the flange portion, and an annular weight fitted on the outer periphery of the tubular portion, the flange portion and the said A knocking sensor including an annular piezoelectric element sandwiched between a weight and an insulator interposed between the flange portion and the piezoelectric element, and a male screw is formed on the outer peripheral surface of the cylindrical portion. A portion is provided, further provided with a nut that is screwed to the male screw portion and is screwed to the top surface of the weight to lock the weight, and the cylindrical portion is the most axially oriented in the male screw portion. An extension portion extending in the axial direction is provided between the tip of the male screw portion, which is a portion on the flange portion side, and the flange portion, and the extension portion has a maximum thickness portion having a maximum thickness and a maximum thickness portion. A thin-walled portion having a thickness thinner than that is formed , and a synthetic resin is filled between the extending portion and the weight .

According to this knocking sensor, there is a maximum thickness part and a thin part that is thinner and less rigid than the maximum thickness part in the extension part between the tip of the male screw part near the fixed position of the weight of the tubular part and the flange part. When the weight vibrates, the thin portion bends and the vibration is amplified, so that the detection output can be improved without increasing the weight of the weight. Further, it is possible to improve the output of the sensor using a low output piezoelectric element (for example, a lead-free piezoelectric element).

In the knocking sensor of the present invention, the thin-walled portion may be connected to the flange portion.
According to this knocking sensor, when a thin-walled portion is formed from a tubular portion by cutting or the like, the upper surface of the flange portion can be used for alignment, so that the machining becomes easy.

In the knocking sensor of the present invention, the thickness of the thin portion may be ½ or more of the maximum thickness.
According to this knocking sensor, it is possible to cope with a case where it is required to secure the strength and durability of the thin-walled portion.

In the knocking sensor of the present invention, the length of the thin-walled portion in the axial direction may be ½ or less with respect to the length of the extended portion in the axial direction.
According to this knocking sensor, it is possible to cope with a case where it is required to secure the strength and durability of the thin-walled portion.

According to the present invention, a knocking sensor having an improved detection output can be obtained.

It is a front view which shows the appearance of the knocking sensor which concerns on embodiment of 1st Embodiment of this invention. It is sectional drawing of the knocking sensor which concerns on embodiment of 1st Embodiment of this invention. It is an exploded view of the internal structure of the knocking sensor which concerns on embodiment of 1st Embodiment of this invention. It is a partially enlarged sectional view of the modification of the knocking sensor which concerns on embodiment of 1st Embodiment of this invention. It is sectional drawing of the knocking sensor which concerns on embodiment of the 2nd Embodiment of this invention. It is an exploded view of the internal structure of the knocking sensor which concerns on embodiment of the 2nd aspect of this invention. It is a process drawing which shows an example of the manufacturing method of the knocking sensor which concerns on embodiment of 1st Embodiment of this invention. It is a figure which shows the relationship between the output voltage of the knocking sensor which concerns on embodiment of 1st Embodiment of this invention, and the thickness of a thin-walled portion. It is a figure which shows the relationship between the output voltage of the knocking sensor which concerns on embodiment of the 2nd Embodiment of this invention, and the thickness of a thin-walled portion.

First, the knocking sensor 1A according to the embodiment of the first aspect of the present invention will be described with reference to FIGS. 1 to 4.
FIG. 1 shows the appearance of the knocking sensor 1A, FIG. 2 shows a cross-sectional view of the knocking sensor 1A broken in the axial direction, FIG. 3 shows an exploded view of the internal structure of the knocking sensor 1A, and FIG. 4 shows the knocking sensor 1A. A partially enlarged cross-sectional view of a modified example is shown.
In FIG. 1, the knocking sensor 1A is a so-called center hole type non-resonant knocking sensor having a mounting hole 11 (see FIG. 2) for mounting on a cylinder block or the like of an internal combustion engine in the center. The knocking sensor 1A is covered with a case 3 made of a synthetic resin (for example, nylon 66) which is a resin mold material. The case 3 is composed of a cylindrical element accommodating portion 5 having a tapered upper portion and a connector portion 7 for connecting a connector from an ignition timing control device (not shown).

As shown in FIGS. 2 and 3, the knocking sensor 1A extends in the axis O direction and includes a main metal fitting 9 made of a metal material (for example, SPHD, SWCH25K), and the main metal fitting 9 is for inserting a bolt. It has a cylindrical tubular portion 13 having a mounting hole 11 and a flange portion 15 extending outward in the circumferential direction from the outer peripheral surface on one end side (lower side of FIG. 1) of the tubular portion 13.
On one side (upper surface in FIG. 1) of the flange portion 15 of the main metal fitting 9 in the thickness direction, a piezoelectric element 17 made of piezoelectric ceramics (for example, PZT) having an annular shape (cylindrical shape) fitted to the outer periphery of the tubular portion 13. Is placed.
Further, on the upper surface side of the piezoelectric element 17, a weight 19 made of a metal material (for example, SMF4050), which is an annular shape (cylindrical shape) fitted to the outer periphery of the tubular portion 13 and has a specific gravity that exerts an effect as a weight, is placed. Has been done.

Output terminals 21 and 23 made of a conductive material (for example, brass) are provided between the flange portion 15 and the piezoelectric element 17, and between the weight 19 and the piezoelectric element 17, that is, on both sides of the piezoelectric element 17 in the thickness direction, respectively. It is arranged so as to be in contact with the piezoelectric element 17. The portion of the output terminals 21 and 23 in contact with the piezoelectric element 17 is annular.
Further, between the flange portion 15 and the output terminal 21, and between the output terminal 23 and the weight 19, annular insulators 25 and 27 made of a film-like synthetic resin (for example, PET) having an insulating property are respectively. It is arranged so that the output terminals 21 and 23 are not short-circuited with the flange portion 15 and the weight 19 of the main metal fitting 9.

An annular space 20 is formed between the inner peripheral surface of the piezoelectric element 17, the weight 19, the output terminals 21, 23 (annular portion), the insulators 25, 27, and the outer peripheral surface of the tubular portion 13. The annular space 20 is also filled with the synthetic resin. Further, the main metal fitting 9 is attached with an annular leaf spring 29 made of a metal material (for example, SK-5M) and pressing the weight 19 in the flange portion 15 direction (lower part of the figure).
The leaf spring 29 has a shape that rises diagonally from the outer peripheral surface in a truncated cone shape and extends horizontally inward in the radial direction, and the center of the horizontal portion opens.
At least a part of the lower surface of the leaf spring 29 is in contact with the upper surface (upper surface of FIG. 1) 19a of the weight 19, and the upper surface 19a of the weight 19 corresponds to the "top surface" in the claims. Further, the leaf spring 29 corresponds to the "other member" in the claims. Further, the insulator 25 between the flange portion 15 and the output terminal 21 corresponds to the "insulator" in the claims.

Further, at the position above the leaf spring 29, the outer peripheral surface of the tubular portion 13 is provided with a protruding portion 13p that plastically deforms and protrudes from the inner surface 13a of the tubular portion 13 toward the outside in the circumferential direction. Further, a recess 13r is formed on the inner surface 13a of the tubular portion 13 corresponding to the protruding portion 13p.
Then, when the protruding portion 13p comes into contact with the upper surface of the leaf spring 29, the leaf spring 29 is pressed downward, and the weight 19 is further locked by the elastic force of the leaf spring 29, and the weight 19 is between the weight 19 and the flange portion 15. The laminated structure (piezoelectric element 17, output terminals 21, 23, insulators 25, 27) is fixed to the main metal fitting 9.
That is, in the present embodiment, the protruding portion 13p is in contact with the top surface 19a of the weight 19 via the leaf spring 29, and the weight 19 is indirectly pressed toward the flange portion 15 of the main metal fitting 9. It is locked to the main metal fitting 9.
The protruding portion 13p may protrude from the outer peripheral surface of the tubular portion 13 by about 0.1 to 0.2 mm.

As described above, by locking the weight 19 to the main metal fitting 9 by the protruding portion 13p provided on the tubular portion 13 without using the nut, the cost of the nut parts is reduced and the cost of the knocking sensor 1A is reduced. be able to.

Here, as shown in FIG. 2, the tubular portion 13 has an extending portion R1 extending in the axis O direction between the lower surface of the protruding portion 13p and the upper surface of the flange portion 15. The extended portion R1 is formed with a maximum thickness portion W1 having a maximum thickness t1 and a thin portion W2 having a thickness t2 thinner than the maximum thickness t1.
By doing so, the maximum thickness portion W1 and the thickness t2 are thinner and the rigidity is lower in the extending portion R1 between the protruding portion 13p, which is the fixed position of the weight 19 of the tubular portion 13, and the flange portion 15. When the thin-walled portion W2 intervenes and the weight 19 vibrates, the thin-walled portion W2 bends and amplifies the vibration, so that the detection output can be improved without increasing the weight of the weight 19. Further, it is possible to improve the output of the sensor using a low output piezoelectric element (for example, a lead-free piezoelectric element).
The extending portion R1 is a region along the axis O direction between the position of the protruding portion 13p on the most protruding portion 15 side and the position of the flange portion 15 on the most protruding portion 13p side.

In this embodiment, the thickness t2 of the thin portion W2 is ½ or more of the maximum thickness t1. By doing so, it is possible to cope with the case where it is required to secure the strength and durability of the thin-walled portion W2.
Further, in the present embodiment, the length of the thin portion W2 in the axis O direction is ½ or less with respect to the length of the extension portion R1 in the axis O direction. By doing so, it is possible to cope with the case where it is required to secure the strength and durability of the thin-walled portion W2.

The thin-walled portion W2 in FIG. 2 has a stepwise reduced diameter from the outer peripheral surface of the tubular portion 13 near the central portion of the extension portion R1 in the axis O direction, and the thin-walled portion W2 is the same at any position in the axis O direction. It has a diameter.
However, for example, as shown in the modified example of FIG. 4, the thickness of the extending portion R1 may change along the axis O direction, and in this case, the portion having the minimum thickness t2 is regarded as the thin-walled portion W2.

Next, the knocking sensor 1B according to the second embodiment of the present invention will be described with reference to FIGS. 5 to 6.
FIG. 5 shows a cross-sectional view of the knocking sensor 1B broken in the axial direction, and FIG. 6 shows an exploded view of the internal structure of the knocking sensor 1B.
The knocking sensor 1B according to the second embodiment is not provided with a protruding portion 13p, but is provided with a male screw portion 13s on the tubular portion 13B of the main metal fitting 9B and is screwed to the male screw portion 13s. The point that the nut 31 is provided is different from the knocking sensor 1A according to the first embodiment, but since the other configurations are the same, the same components are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 5, a male screw portion 13s is provided on the outer surface of the tubular portion 13B of the main metal fitting 9B on the rear end side. A nut 31 is arranged on the upper portion of the leaf spring 29, and the nut 31 is screwed to the male screw portion 13s.
Therefore, by tightening the nut 31, the leaf spring 29 is pressed downward, the weight 19 is further locked by the elastic force of the leaf spring 29, and the laminated structure (piezoelectric element 17) between the weight 19 and the flange portion 15B is engaged. , Output terminals 21, 23, insulators 25, 27) are fixed to the main metal fitting 9.
In this way, by locking the weight 19 to the main metal fitting 9B using a nut, it can be assembled without using a special device or jig for forming the protruding portion 13p.

Here, as shown in FIG. 5, the tubular portion 13B extends between the tip of the male screw portion, which is the portion closest to the flange portion 15B in the axial O direction in the male screw portion 13s, and the upper surface of the flange portion 15B. A thin portion W3 having a thickness t4 thinner than the maximum thickness t3 forming the minimum thickness in the male screw portion 13s is formed on the setting portion R1.
Also in this case, there is an extension portion R1 extending in the axis O direction between the tip of the male screw portion 13s near the fixed position of the weight 19 of the tubular portion 13B and the upper surface of the flange portion 15B. The extension portion R1 is formed with a maximum thickness portion W3 having a maximum thickness t3 and a thin portion W4 having a thickness t4 thinner than the maximum thickness t3.
In this way, the maximum thickness portion W3 and the thin-walled portion W4 having a thinner thickness t4 and lower rigidity are interposed in the extending portion R1, and when the weight 19 vibrates, the thin-walled portion W4 bends and amplifies the vibration. The detection output can be improved without increasing the weight of the weight 19. Further, it is possible to improve the output of the sensor using a low output piezoelectric element (for example, a lead-free piezoelectric element).

The maximum thickness t3 is the thickness of the valley portion of the male screw portion 13s.
Further, in the present embodiment, the thin-walled portion W4 is connected to the upper surface of the flange portion 15B. By doing so, when the thin-walled portion W4 is formed from the tubular portion 13B by processing such as cutting, the upper surface of the flange portion 15B can be used for alignment, so that the processing becomes easy.
Further, from the viewpoint of increasing the swing width to improve the output of the sensor, as shown in FIG. 5, the thin-walled portion W4 is located at the boundary between the extension portion R1 and the flange portion 15 farthest from the weight 19. Is good.

Next, with reference to FIG. 7, an example of a method for manufacturing the knocking sensor 1A according to the embodiment of the first aspect of the present invention will be described.
First, the main metal fitting rough shape material 9x is prepared. The main metal fitting rough material 9x has a tubular portion 13x in which a recess 13r is not formed on the inner surface 13a and a protruding portion 13p is not formed on the outer peripheral surface, and the above-mentioned above-mentioned one end side (lower side) of the tubular portion 13x. It has a collar 15 (see FIG. 3). Then, the insulating member 25, the output terminal 21, the piezoelectric element 17, the output terminal 23, the insulating member 27, the weight 19, and the leaf spring 29 are sequentially mounted on the flange portion 15 so as to be fitted on the outer peripheral side of the tubular portion 13x. Place.
Further, the press jig 110 is inserted into the inner surface of the tubular portion 13x from the flange portion 15 side (lower side) (FIG. 7A). The press jig 110 is composed of individual pieces divided into four by four notches, and the overhanging portion 110f located on the lower end side of each piece is held by one annular holding ring 140. It is formed and has a substantially cylindrical shape having a substantially circular hole into which a piston 130 described later can be inserted. The overhanging portion 110f of each piece constituting the press jig 110 abuts on the lower surface of the flange portion 15 to position the insertion depth.

Further, on the upper end side of the press jig 110 (each piece), a convex portion 110p protruding outward in the circumferential direction and four notches (not shown) extending in the axial direction are formed, and the convex portion 110p is formed. Is separated into four in the circumferential direction at the notch. Therefore, by closing or opening the notch portion, the convex portion 110p can be reduced in diameter and expanded in the circumferential direction, and when the press jig 110 is inserted into the inner surface of the tubular portion 13x, the cylinder is formed. Pressed against the inner surface of the shaped portion 13x, the convex portion 110p is reduced in diameter in the circumferential direction.

Next, the cylindrical pin 120 is lowered from above, and the leaf spring 29 is pressed by the lower surface of the cylindrical pin 120 to be elastically deformed so that the upper surface of the leaf spring 29 becomes horizontal (FIG. 7 (b)).
Next, with the cylindrical pin 120 lowered, the piston 130 is inserted from above into the upper end side (hole inside the press jig 110) of the press jig 110 (FIG. 7 (c)). The piston 130 has a tapered shape that narrows toward the tip, and when the piston 130 is inserted into the press jig 110, the upper end side of the press jig 110 is expanded, each piece moves outward in the circumferential direction, and the convex portion 110p. Expands the diameter (FIG. 7 (d)).

Therefore, the inner surface of the tubular portion 13x in contact with the convex portion 110p is plastically deformed and protrudes toward the outside in the circumferential direction to form the concave portion 13r. At this time, since the position of the concave portion 13r (that is, the position of the convex portion 110p) is substantially the same as the upper surface of the leaf spring 29 in the pressed state, the protruding portion 13p is formed on the upper surface side of the leaf spring 29. Then, when the cylindrical pin 120 is released, the leaf spring 29 elastically returns, and the top surface 19a of the weight 19 is pressed toward the flange portion 15 by the elastic force of the leaf spring 29 while in contact with the protruding portion 13p, and the above-mentioned laminated structure is formed. The body is fixed to the main metal fitting 9.
After assembling the knocking sensor 1A in this way, the case 3 is formed by injecting and solidifying a resin mold material (synthetic resin) so as to cover the above-mentioned laminated structure including the main metal fitting 9, and the knocking sensor 1A is formed. Is completed.

It goes without saying that the present invention is not limited to the above embodiments and extends to various modifications and equivalents included in the idea and scope of the present invention.
The cross-sectional shape and thickness of the thin-walled portion are not particularly limited.
As the type of the insulator, in addition to the above-mentioned film-shaped synthetic resin, a ceramic material may be used, or an insulating adhesive may be applied. Further, in the above embodiment, the protruding portion 13p is in contact with the top surface 19a of the weight 19 via the leaf spring 29, and the weight 19 is locked. This is because the insulators 25 and 27 made of synthetic resin are thinned by thermal creep. This is because a gap is generated in the axial direction, and this gap is filled with the elastic deformation of the leaf spring 29. On the other hand, when an insulator such as ceramic that does not cause thermal creep is used, the weight 19 may be locked by directly contacting the protruding portion 13p with the top surface 19a of the weight 19 without using the leaf spring 29.
Instead of the leaf spring 29, an annular disc spring may be used for another member.

The knocking sensor 1A according to the first embodiment of the structure shown in FIG. 2 and the knocking sensor 1B according to the second embodiment of the structure shown in FIG. 5 are provided with the thickness t2 of the thin portion W2 and W4, respectively. A plurality of products were manufactured by changing t4.
Further, for comparison, a conventional knocking sensor without thin-walled portions W2 and W4, respectively, was manufactured.
For each of the obtained knocking sensors, a constant vibration was applied and the output voltage of the sensor was measured.
Then, the output voltage of the sensor was obtained as a relative value when the output voltage of the conventional knocking sensor was 1.

FIG. 8 shows data when the (maximum thickness t1 / thickness t2 of the thin portion W2) of the knocking sensor 1A according to the first embodiment is the horizontal axis and the relative value of the output voltage of the sensor is the vertical axis. show. In the case of a conventional knocking sensor without a thin wall portion, t1 / t2 = 1.
Similarly, FIG. 9 shows the case where the (maximum thickness t3 / thickness t4 of the thin portion W3) of the knocking sensor 1B according to the second embodiment is the horizontal axis and the relative value of the output voltage of the sensor is the vertical axis. The data of is shown. In the case of a conventional knocking sensor having no thin wall portion, t3 <t4, so t1 / t2 <1.
As is clear from FIGS. 8 and 9, it can be seen that the output voltage of the sensor is improved by providing the thin-walled portion as compared with the conventional sensor having no thin-walled portion. Further, it can be seen that the output voltage of the sensor is further improved as the thickness of the thin portion is reduced.
When (t1 / t2) ≦ 1.3 and (t3 / t4) ≦ 1.3, the output voltage of the sensor is surely improved.

1A, 1B Knocking sensor 9, 9B Main metal fitting 13, 13B Cylindrical part 13p Protruding part 13s Male thread part 15, 15B flange part 17 Piezoelectric element 19 Weight 19a Weight top surface 25 Insulator 29 Other member 31 Nut O Axis line P1, Cutting-edge part of P2 contact point R1 Extension part W1, W3 Maximum thickness part W2, W4 Thin-walled part t1, t3 Maximum thickness t2, t4 Thin-walled part thickness

Claims (5)

A main metal fitting that extends in the axial direction and has a cylindrical portion and a flange portion that is located on one end side of the tubular portion and protrudes outward in the circumferential direction of the tubular portion.
An annular weight that is fitted around the outer circumference of the tubular portion and has a top surface on the side opposite to the side facing the flange portion.
An annular piezoelectric element fitted to the outer periphery of the tubular portion and sandwiched between the flange portion and the weight.
A knocking sensor provided with an insulator interposed between the flange portion and the piezoelectric element.
The outer peripheral surface of the tubular portion protrudes from the inner surface of the tubular portion while being plastically deformed toward the outside in the circumferential direction, and is in contact with the top surface of the weight directly or via another member to lock the weight. Protruding part is provided,
The tubular portion has an extension portion extending in the axial direction between the protrusion portion and the flange portion, and the extension portion has a maximum thickness portion having a maximum thickness and a thickness greater than the maximum thickness. A thin thin part is formed ,
A knocking sensor in which a synthetic resin is filled between the extension portion and the weight . A main metal fitting that extends in the axial direction and has a cylindrical portion and a flange portion that is located on one end side of the tubular portion and protrudes outward in the circumferential direction of the tubular portion.
An annular weight that is fitted around the outer circumference of the tubular portion and has a top surface on the side opposite to the side facing the flange portion.
An annular piezoelectric element fitted to the outer periphery of the tubular portion and sandwiched between the flange portion and the weight.
A knocking sensor provided with an insulator interposed between the flange portion and the piezoelectric element.
A male screw portion is provided on the outer peripheral surface of the tubular portion, and a nut that is screwed to the male screw portion and is in contact with the top surface of the weight to lock the weight is provided.
The tubular portion has an extension portion extending in the axial direction between the tip of the male screw portion, which is the portion of the male screw portion closest to the flange portion in the axial direction, and the flange portion. A maximum thickness portion having a maximum thickness and a thin wall portion thinner than the maximum thickness are formed in the setting portion.
A knocking sensor in which a synthetic resin is filled between the extension portion and the weight . The knocking sensor according to claim 1 or 2, wherein the thin-walled portion is connected to the flange portion. The knocking sensor according to any one of claims 1 to 3, wherein the thickness of the thin portion is ½ or more of the maximum thickness. The knocking sensor according to any one of claims 1 to 4, wherein the length of the thin portion in the axial direction is ½ or less with respect to the length of the extended portion in the axial direction.

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