JPH10267748A - Knocking sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a sensor by heightening an insulating strength in a knocking sensor to detect the knocking from the vibration of an internal combustion engine. SOLUTION: A lower side lead plate 6, a piezoelectric element 5, an upper side lead plate 7, an insulation sheet 8, a weight 22 and a disc spring 10 are inserted in order into the cylindrical part 3b of a housing 3. An annular projection 23 is formed on the outer periphery of the upper face of the weight 22, and a regulating stepped part 24 to fit with the outer periphery side of the disc spring 10 is composed of the inner periphery 23A of the projection 23. Thus the regulating stepped part 24 can prevent the disc spring 10 from being eccentric to the weight 22 at the time of fastening a nut 11, and string-shaped shaving chips produced hitherto can therefore be eliminated to prevent a defective insulation due to the shaving chips.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock sensor for detecting, for example, vibration of an internal combustion engine by a piezoelectric element having a piezo effect.

[0002]

2. Description of the Related Art In general, to increase the thermal efficiency of a gasoline engine, it is effective to increase the compression ratio.
This is subject to gasoline octane limitations. In particular, in the case of a turbocharged engine in which an air-fuel mixture is pre-pressed by an exhaust turbocharger, knocking becomes a problem. Therefore, a knock control system is employed in order to minimize the compression ratio of the turbocharged engine.

This knock control system detects a vibration of the internal combustion engine by a knock sensor attached to the internal combustion engine, and when the knock sensor detects the occurrence of knocking, the control unit controls the ignition timing to be advanced. Is what you do.

In this system, by avoiding knocking, the engine is operated at an ignition timing close to the knocking occurrence limit, thereby improving combustion efficiency and improving output and fuel efficiency.

Here, a knock sensor using a piezoelectric body as a prior art will be described with reference to FIG. 5. In FIG. 1, reference numeral 1 denotes a knock sensor covered with a resin portion 2 having an outer shape.
A connector portion 2A is formed in the resin portion 2 of the knock sensor 1.

Reference numeral 3 denotes a stepped cylindrical housing which forms the base of the knock sensor 1. The housing 3 includes a disk-shaped flange 3A, a cylindrical portion 3B extending in the axial direction from the flange 3A, and A male screw portion 3C formed on the outer peripheral surface on the distal end side of the cylindrical portion 3B, an upper groove portion 3D located on the distal end portion of the cylindrical portion 3B and above the male screw portion 3C, and the flange portion 3A. And a lower groove 3 </ b> E having three flanges formed on the outer peripheral surface thereof. The upper groove 3D and the lower groove 3E prevent water or the like from entering from outside.

Reference numeral 4 denotes an insulating tube attached to the outer periphery of the cylindrical portion 3B of the housing 3. The insulating tube 4 is formed of a heat-shrinkable tube. The side extends to the center of the cylindrical portion 3B (below the male screw portion 3C). Further, since the insulating tube 4 is formed by a heat-shrinkable tube, the insulating tube 4 is disposed so as to be substantially fixed to the cylindrical portion 3B. The insulating tube 4 insulates the cylindrical portion 3B located on the inner peripheral side from the lower lead plate 6, the piezoelectric element 5, the upper lead plate 7, and the weight 9 located on the outer peripheral side, which will be described later. .

Reference numeral 5 denotes an annular piezoelectric element. The piezoelectric element 5 is inserted into the cylindrical portion 3B of the housing 3 and is provided on the side of the flange 3A. Further, the piezoelectric element 5 is made of a piezoelectric material such as lead titanate, and the piezoelectric element 5 is formed of, for example, a d33 element in which each of a stress axis, a polarization axis, and a signal axis is equal to an axial direction. The piezoelectric element 5 generates an axially applied vibration pressure as an axial voltage signal.

Reference numeral 6 denotes a lower lead plate formed of a conductive metal material into an annular plate, and the lower lead plate 6 has a disk portion 6A and a radially projecting portion from the disk portion 6A. The arm 6B is provided with a terminal 6C welded to the arm 6B. The lower lead plate 6 is inserted into the cylindrical portion 3B of the housing 3 while the piezoelectric element 5 is inserted.
Is in contact with the lower surface.

Reference numeral 7 denotes an upper lead plate formed of a conductive metal material on an annular plate, and the upper lead plate 7 is provided with a disk portion 7A and protrudes radially from the disk portion 7A. It is composed of an arm 7B and a terminal 7C welded to the arm 7B. The upper lead plate 7 is inserted into the cylindrical portion 3B of the housing 3, and the piezoelectric element 5
Is provided in contact with the upper surface of the.

Reference numeral 8 denotes an insulating sheet formed in a thin annular shape with an insulating resin. The insulating sheet 8 is inserted into the cylindrical portion 3B of the housing 3 and provided on the upper surface of the upper lead plate 7. . And the insulating sheet 8
Is to insulate the upper lead plate 7 from a weight 9 described later.

Reference numeral 9 denotes an annular thick weight. The weight 9 is inserted into the cylindrical portion 3B of the housing 3 and provided on the upper surface of the insulating sheet 8. The weight 9 applies a preload to the piezoelectric element 5 together with a disk spring 10 and a nut 11, which will be described later, and is made of a metal material such as iron.

Reference numeral 10 denotes a disk spring. The disk spring 10 is formed of, for example, a disc spring or a corrugated washer. The disk spring 10 is inserted into the cylindrical portion 3B of the housing 3 and located above the weight 9. It is provided.

Reference numeral 11 denotes a nut. The nut 11 is provided by screwing to the external thread 3C of the housing 3. Here, the lower lead plate 6, the piezoelectric element 5, the upper lead plate 7, the insulating sheet 8, the weight 9, and the disk spring 10 are fixed to the housing 3 by screwing the nut 11 to the male screw portion 3C. A preload is applied to the piezoelectric element 5 via the disk spring 10 and the weight 9.

Reference numeral 12 denotes a self-diagnosis resistor connected between the lead plates 6 and 7 and having a resistance value of, for example, 560 kΩ.

Here, in order to manufacture the knock sensor 1,
The insulating tube 4 is attached to the cylindrical portion 3B of the housing 3.
Next, the lower lead plate 6, the piezoelectric element 5, the upper lead plate 7, the insulating sheet 8, and the weight 9 are sequentially inserted into the cylindrical portion 3B of the housing 3. Next, with the disk spring 10 inserted above the weight 9, the nut 11 is screwed to the external thread 3C of the housing. Then, it is covered with the resin part 2 by resin molding. At this time, the connector portions 2A from which the terminal portions 6C and 7C of the lead plates 6 and 7 protrude to the outside are simultaneously formed.

The knock sensor 1 thus configured is
It is attached to an internal combustion engine (neither is shown) by bolts inserted into the cylindrical portion 3B of the housing 3. And
When knocking vibration occurs in the internal combustion engine, the knock sensor 1 converts the vibration into a voltage signal by the piezoelectric element 5, and the voltage signal is transmitted to the lower lead plate 6 and the upper lead plate 7.
Derived to the outside through

[0018]

In the knock sensor 1 according to the prior art described above, an insulating tube 4 is provided on the outer periphery of the cylindrical portion 3B of the housing in order to prevent a short circuit, and the upper lead plate 7 and the weight 9 are connected to each other. Although an insulating sheet 8 is provided between them, insulation failure may occur rarely.

The inventors of the present invention have analyzed the cause of the cause and conducted intensive experiments and researches. As a result, the present inventors have been able to find out the location of the occurrence of insulation failure and the location of burrs and debris causing insulation failure. It turned out that it was the position of the part a (disk spring 10 and nut 11) in FIG.

FIG. 6 shows the problem of the part a.
When the disk spring 10 moves in the radial direction and becomes eccentric when the nut 11 is tightened, the eccentric disk spring 10 comes into contact with the external thread portion 3C, and thread-like shavings 13 are generated. The shavings 13 may enter between the upper lead plate 7 and the weight 9 or into the gap between the tubular portion 3B and the insulating tube 4, and may cause insulation failure.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a knock sensor capable of preventing insulation failure.

[0022]

In order to solve the above-mentioned problems, a knock sensor according to the present invention comprises a housing having a cylindrical portion extending from a flange portion in an axial direction and a male screw portion at a tip end of the cylindrical portion; An insulating tube provided on the outer periphery of the cylindrical portion of the housing, a piezoelectric element positioned on the outer peripheral side of the insulating tube and inserted into the cylindrical portion of the housing, and positioned on the lower surface and the upper surface of the piezoelectric element; A lower lead plate and an upper lead plate provided; an insulating sheet provided above the upper lead plate; a weight provided above the insulating sheet; and an upper surface of the weight. A disk spring provided at a position,
A nut is fastened to the external thread of the housing to apply a preload to the piezoelectric element by the weight and the disk spring.

A feature of the structure adopted by the first aspect of the present invention is that, on the upper surface of the weight, an outer peripheral side of a disc spring is fitted, and a regulating step for regulating the radial movement of the disc spring is provided. It is to have provided.

With this configuration, when the outer peripheral side of the disc spring is fitted to the regulating step, the disc spring is prevented from moving in the radial direction with respect to the weight, and the disc spring is eccentric when tightened. Can be prevented. As a result, it is possible to eliminate thread-like shavings which have conventionally been caused by the disk spring being eccentric and hitting against the external thread portion of the housing.

According to a second aspect of the present invention, an annular projection is formed on the outer periphery of the upper surface of the weight, and the regulating step is formed by the inner peripheral surface of the annular projection.

With this configuration, when the outer peripheral side of the disc spring is fitted to the regulating step formed by the inner peripheral surface of the annular projection, the disc spring is prevented from moving in the radial direction with respect to the weight. can do.

A third aspect of the present invention resides in that a plurality of arc-shaped projections are formed on the outer periphery of the upper surface of the weight, and the regulating step is constituted by the inner peripheral surface of each of the arc-shaped projections.

With this configuration, when the outer peripheral side of the disk spring is fitted to the regulating step formed by the inner peripheral surface of each arc-shaped projection, the disk spring moves in the radial direction with respect to the weight. Can be regulated.

According to a fourth aspect of the present invention, a plurality of arc-shaped projections are formed on the outer periphery of the upper surface of the weight, and the regulating step is formed by the inner peripheral surface of each of the arc-shaped projections. Is characterized in that radial projections are formed to restrict rotation of the disk spring by engaging between the arc-shaped projections.

With this configuration, when the outer peripheral side of the disk spring is fitted to the regulating step formed by the inner peripheral surface of each arc-shaped projection, the disk spring moves in the radial direction with respect to the weight. Can be regulated. In addition, by engaging the arc-shaped projections with the respective arc-shaped projections, the rotation of the disc spring with respect to the weight can be restricted. As a result, it is possible to eliminate the thread-like shavings that have conventionally been caused by the disk spring being eccentric and hitting the screw portion in one side.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIGS. 1 to 4 show an embodiment according to the present invention.

In the embodiment, the same reference numerals are given to the same components as those in the above-described prior art, and the description thereof will be omitted.

First, a first embodiment according to the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 21 denotes a knock sensor according to the present embodiment. The knock sensor 21 is a knock sensor described in the prior art. In substantially the same manner as the sensor 1, an insulating tube 4 attached to the outer periphery of the cylindrical portion 3B of the housing 3, a lower lead plate 6, a piezoelectric element 5, an upper lead plate 7, and an insulating sheet 8 sequentially inserted into the cylindrical portion 3B. And a weight 22, a disk spring 10, and a nut 11, which will be described later. However, the knock sensor 21 according to the present embodiment
Differs from the knock sensor 1 according to the prior art in the shape of the weight 22.

Reference numeral 22 denotes a weight according to the present embodiment. The weight 22 has an annular projection 23 described later formed on the outer periphery of the upper surface thereof. The weight 22 applies a preload to the piezoelectric element 5 together with the disk spring 10 and the nut 11.

Reference numeral 23 denotes an annular projection. The annular projection 23 is formed on an outer periphery of the upper surface of the weight 22 so as to project annularly.

Numeral 24 denotes a regulating step formed by the inner peripheral surface 23A of the annular projection 23. The regulating step 24 is fitted to the outer peripheral side of the disc spring 10 so that the disc spring 10 The disk spring 10 is prevented from being eccentric with respect to the weight 22.

The knock sensor 21 according to the present embodiment is configured as described above. However, since the operation as the knock sensor 21 is the same as that of the knock sensor 1 according to the prior art, the description thereof will be omitted.

In this embodiment, however, the annular projection 23 is formed on the outer periphery of the upper surface of the weight 22, and the regulating step 24 is constituted by the inner peripheral surface 23A of the annular projection 23. By fitting the outer peripheral side of the disc 10, the radial movement of the disc spring 10 can be restricted. Thus, the disc spring 10 is prevented from being eccentric with respect to the weight 22, and the disc spring 10 can be prevented from hitting against the male screw portion 3C.

As a result, when tightening the nut 11,
Even if the disc spring 10 is dragged with respect to the weight 22, the disc spring 10 is restricted from moving in the radial direction by the regulating step 24, so that contact between the disc spring 10 and the external thread 3C is prevented. Can be prevented.

Thus, the knock sensor 2 according to the present embodiment
In the prior art 1, an annular projection 23 is formed on a weight 22 after locating the cause of shavings generated when a nut is tightened, and an inner peripheral surface 23A of the annular projection 23 is defined as a regulating step 24. Since the outer peripheral side of the spring 10 is fitted, the disc spring 1 is
0 can be restricted from moving in the radial direction, and generation of shavings can be prevented. Then, it is possible to prevent the occurrence of insulation failure in knock sensor 21 due to the shavings.

As a result, the voltage signal generated from the piezoelectric element 5 is prevented from flowing through the shavings to the cylindrical portion 3B of the housing 3 or the weight 9, and the reliability of the knock sensor 21 can be improved.

Next, a second embodiment of the present invention will be described with reference to FIG.
In describing this embodiment, the feature of this embodiment is that the weight 3
The four arc-shaped projections 32 are formed on the outer periphery of the upper surface of the first projection 1, and the regulating step 33 is constituted by the inner peripheral surface 32 </ b> A of each of the arc-shaped projections 32.

However, in this embodiment, four arc-shaped projections 32 are formed on the outer periphery of the upper surface of the weight 31 and the inner peripheral surface 32A of each of the arc-shaped projections 32 is defined as the regulating step 33. By fitting the outer peripheral side of the disc spring 10 between the step portions 33, the radial movement of the disc spring 10 can be restricted. Thus, similarly to the first embodiment described above, the eccentricity of the disc spring 10 is regulated, and the disc spring 10 is
Can be prevented.

As a result, when the nut 11 is tightened, it is possible to prevent the disk spring 10 from coming into contact with the external thread portion 3C and to prevent the generation of shavings. In addition, it is possible to prevent the occurrence of insulation failure in the knock sensor due to the shavings, thereby improving the reliability of the knock sensor.

Further, a third embodiment of the present invention will be described with reference to FIG. 4. The feature of this embodiment is that four arc-shaped projections 32 are formed on the outer periphery of the upper surface of the weight 31. The regulating step 33 is formed by the inner peripheral surface 32A of each arc-shaped projection 32.
And a radial projection 42 engaging between the arc-shaped projections 32 is provided on the outer peripheral edge of the disc spring 41.
It has been formed individually.

However, in this embodiment, four arc-shaped projections 32 are formed on the outer periphery of the upper surface of the weight 31, and the inner peripheral surface 3 is formed.
Since the regulating step 33 is formed by 2A, the radial movement of the disc spring 10 can be regulated by fitting the outer peripheral side of the disc spring 10 between the regulating steps 33.

Further, by engaging the radial projections 42 of the disc spring 31 between the arc-shaped projections 32,
The rotation of the disc spring 41 can be stopped.

Thus, also in this embodiment, similarly to the first embodiment described above, the eccentricity of the disk spring 41 with respect to the weight 31 is restricted, and the disk spring 41 is prevented from hitting against the male screw portion 3C. it can.

Further, in this embodiment, since the rotation of the disk spring 41 is also stopped, it is possible to prevent the disk spring 41 from being dragged by the rotation of the nut 11 when the nut 11 is tightened. 31 can be prevented from being eccentric.

As a result, when the nut 11 is tightened, it is possible to reliably prevent the disk spring 10 from coming into contact with the external thread portion 3C and to prevent the generation of shavings. Then, it is possible to prevent the occurrence of insulation failure in the knock sensor due to the shavings, thereby improving the reliability of the knock sensor.

In the second and third embodiments, arc-shaped projections 32, 32,.
However, the present invention is not limited to this.
.. May be formed as long as the disk springs 10 (41) are positioned in the radial direction. Also, the radial projection 42 according to the third embodiment.
Can be engaged with the arc-shaped projection 32,
Only one disc spring may be formed on the outer periphery of the disc spring 41.

[0052]

As described above in detail, according to the first aspect of the present invention, the outer periphery of the disk spring is fitted to the upper surface of the weight, thereby restricting the radial movement of the disk spring. Since the regulating step is provided, it is possible to prevent the disk spring from being eccentric with respect to the weight and to prevent the disk spring and the external thread from hitting each other. Thus, when the nut is tightened, the thread portion is prevented from being shaved by the disk spring, and thread-like shavings that have conventionally occurred can be eliminated. As a result, it is possible to prevent the shavings from causing insulation failure in the knock sensor, thereby improving the reliability of the knock sensor.

According to the second aspect of the present invention, since the annular projection is formed on the outer periphery of the upper surface of the weight, and the regulating step is formed by the inner peripheral surface of the annular projection, the outer peripheral side of the disc spring is fitted into the regulating step. By doing so, the movement of the disk spring in the radial direction with respect to the weight can be restricted, and shavings generated when the nut is tightened can be eliminated.

According to the third aspect of the present invention, the regulating step is formed with a plurality of arc-shaped projections on the outer periphery of the upper surface of the weight, and the regulating step is constituted by the inner peripheral surface of each of the arc-shaped projections. By fitting the disc spring between the regulating steps, it is possible to regulate the radial movement of the disc spring with respect to the weight. This makes it possible to eliminate shavings at the time of tightening the nut and prevent insulation failure due to the shavings.

According to the fourth aspect of the present invention, a plurality of arc-shaped projections are formed on the outer periphery of the upper surface of the weight, and the regulating step is formed by the inner peripheral surface of each of the arc-shaped projections. By fitting the disk spring between the restriction steps, it is possible to restrict the disk spring from moving in the radial direction with respect to the weight. Further, by engaging the radial projection of the disc spring between the annular projections, the rotation of the disc spring with respect to the weight can be restricted. As a result, thread-like shavings, which have conventionally been caused by the disk spring being eccentric and colliding with the screw portion, can be eliminated, and insulation failure due to the shavings can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a knock sensor according to a first embodiment.

FIG. 2 is a perspective view showing a weight and a disk spring separately.

FIG. 3 is a perspective view showing a weight and a disk spring according to a second embodiment separately.

FIG. 4 is a perspective view showing a weight and a disk spring according to a third embodiment separately.

FIG. 5 is a longitudinal sectional view showing a knock sensor according to the related art.

FIG. 6 is an enlarged cross-sectional view showing a part a in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 Housing 3A Flange part 3B Tube part 3C Male thread part 4 Insulation tube 5 Piezoelectric element 6 Lower lead plate 7 Upper lead plate 8 Insulation sheet 10, 41 Disk spring 11 Nut 21 Knock sensor 22, 31 Weight 23 Annular projection 23A, 32A Inner peripheral surface 24, 33 Regulation step 32 Arc-shaped projection 42 Radial projection

Claims (4)

[Claims] 1. A housing in which a cylindrical portion extends in the axial direction from a flange portion, a distal end side of the cylindrical portion is a male thread portion, an insulating tube provided on an outer peripheral portion of the cylindrical portion of the housing, and an outer peripheral side of the insulating tube. A piezoelectric element positioned and inserted into the cylindrical portion of the housing, a lower lead plate, an upper lead plate positioned on the lower and upper surfaces of the piezoelectric element, and a piezoelectric element disposed above the upper lead plate. An insulating sheet provided at a position, a weight provided at an upper surface of the insulating sheet, a disk spring provided at an upper surface of the weight, and the piezoelectric element by the weight and the disk spring. A knock sensor comprising a nut fastened to an external thread of the housing for applying a preload, wherein a disk spring is provided on an upper surface of the weight. A knock sensor, wherein an outer peripheral side of the ring is fitted, and a regulating step is provided to regulate the radial movement of the disc spring. 2. The knock sensor according to claim 1, wherein an annular projection is formed on an outer periphery of an upper surface of the weight, and the regulating step is formed by an inner peripheral surface of the annular projection. 3. The knock sensor according to claim 1, wherein a plurality of arc-shaped projections are formed on the outer periphery of the upper surface of the weight, and the regulating step is constituted by an inner peripheral surface of each of the arc-shaped projections. 4. A plurality of arc-shaped projections are formed on the outer periphery of the upper surface of the weight, and the regulating step is formed by the inner peripheral surface of each of the arc-shaped projections. 2. The knock sensor according to claim 1, further comprising: a radial projection that is engaged between the arc-shaped projections to restrict rotation of the disk spring.