JP4054515B2 - Non-resonant knock sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-resonant knock sensor that is attached to an internal combustion engine and electrically detects the occurrence of knocking.
[0002]
[Prior art]
An annular electrode plate electrically connected to the electrode layer is disposed on the front and back surfaces of the annular piezoelectric element having electrode layers formed on the front and back surfaces in a case attached to the internal combustion engine. Various non-resonant knock sensors that are held in a shape have been proposed, such as Japanese Patent Application Laid-Open No. 61-153530. This non-resonant type knock sensor generates a signal voltage between the electrodes by applying a strain in the thickness direction corresponding to the knocking frequency to the piezoelectric element sandwiched in the case in accordance with the occurrence of knocking. Knocking is detected by extracting a potential difference from the pair of plates.
[0003]
[Problems to be solved by the invention]
Since the annular electrode plate is brought into uniform contact with the annular piezoelectric element, the inner and outer diameters thereof are substantially matched with the inner and outer diameters of the annular piezoelectric element. By the way, this annular electrode plate is formed by punching a metal plate into a predetermined shape. Therefore, a burr of about 40 μm along the hitting direction is generated on the inner and outer edges of the annular electrode plate. For this reason, when the annular electrode plate is arranged on the piezoelectric element, the burr comes into direct contact with the electrode layer on the surface where the burr protrudes toward the contact surface with the electrode layer.
[0004]
A weight or the like is arranged on the upper surface of the annular electrode plate, and a nut is fastened to apply a preload to the annular piezoelectric element. When the nut is fastened, the piezoelectric element is rotated and the electrode layer is damaged by the burr. In some cases, burrs may interfere with the stacking and create gaps with the piezoelectric element. In either case, the output signal from the piezoelectric element may decrease or the capacitance of the piezoelectric element may change, There is a possibility that problems such as loss of consistency with the processing circuit may occur. Furthermore, metal powder may be generated due to the deletion of the electrode layer, which may cause a short circuit. On the other hand, as means for solving this problem, there has been proposed means for precisely polishing the front and back surfaces of the electrode plate to remove burrs. However, an extra polishing step is required, resulting in a problem that the manufacturing cost increases.
This invention provides the structure which can prevent the influence by the burr | flash formed in the inner and outer edge of an electrode plate, without requiring a new process.
[0005]
[Means for Solving the Problems]
According to the present invention, an annular electrode plate electrically connected to an electrode layer is disposed on the front and back surfaces of an annular piezoelectric element having electrode layers formed on the front and back surfaces in a case attached to an internal combustion engine. In what holds the element in a pinched state,
An inner diameter and an outer diameter of the annular piezoelectric element are substantially the same as the annular electrode plates disposed on the front and back sides, and an electrode removal edge having no electrode layer on the inner and outer edges of the front and back surfaces of the annular piezoelectric element, The non-resonant knock sensor is characterized in that an electrode removal edge is provided around the burr generated on the inner and outer edges of the electrode plate .
[0006]
In this configuration, even if burrs are formed on the inner and outer edges of the annular electrode plate that is pressed onto the annular piezoelectric element, the electrode layer of the annular piezoelectric element is removed at the inner and outer edges. It will be in contact with the part without. For this reason, even if the annular piezoelectric element is rotated by tightening a nut or the like, the electrode layer is not removed or worn by the burr, and the characteristics and the like do not change. In addition, when a burr of about 40 μm occurs, the thickness of the electrode layer is also about 4 to 10 μm. Therefore, by applying a preload, the burr that has been crushed within a minimal step between the surface without the electrode layer and the electrode layer surface Almost fits and no gap occurs between the annular electrode plate and the piezoelectric element due to burrs during lamination.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An example of a non-resonant knock sensor will be described with reference to FIG.
A synthetic resin case 1 for holding each member includes a cylindrical main body 2, and a metal sleeve 4 is mounted in the center of the inside. The metal sleeve 4 has a flange 5 formed in the lower part and a screw 7 formed around the upper part of the cylindrical part 6. Furthermore, a plurality of engagement steps are formed around the upper end of the cylindrical portion 6 and the flange portion 5 so as to improve the bonding strength with the synthetic resin case 1.
[0008]
An annular piezoelectric element 8 having electrode layers formed on the front and back and polarized in the thickness direction is externally fitted to the cylindrical portion 6, and the annular electrode plates 20 a and 20 b are disposed in close contact with the front and back surfaces of the cylindrical portion 6. Sitting on 5 Here, the upper annular electrode plate 20a (see FIG. 3) is a signal extraction electrode, and the lower annular electrode plate 20b (see FIG. 4) is a ground side electrode. The electrode plates 20a and 20b are protruded from the annular electrode plates 20a and 20b so as to be eccentric to the left and right so that the connection terminals 21 and 21 do not overlap each other in the vertical direction (see FIG. 2). Further, the connection terminal rod 21 of the upper annular electrode plate 20a is bent once (see FIG. 3), and the connection terminal rod 21 of the lower annular electrode plate 20b is bent twice (see FIG. 4) to connect the connection terminal. The heights of the end portions of the flanges 21 and 21 are matched.
[0009]
The annular piezoelectric element 8 and the electrode plates 20 a and 20 b are insulated from the metal sleeve 4 by the insulating cylinder piece 10. The insulating cylindrical piece 10 is an insulating member that is externally fitted to the cylindrical portion 6 and covers the flange portion 5 to insulate the inner edges of the annular piezoelectric element 8 and the annular electrode plates 20a and 20b from the metal sleeve 4. It consists of the pipe part 10b. As described above, the insulation between the annular piezoelectric element 8 and the annular electrode plates 20a and 20b and the metal sleeve 4 is ensured by continuously insulating from the flange portion 5 to the cylindrical portion 6 of the metal sleeve 4. I am doing so.
[0010]
Further, an insulating plate 11 and a weight 12 are sequentially laminated on the upper annular electrode plates 20a and 20b, and further, a nut 13 is disposed on the upper portion of the insulating plate 11 and a weight 12, and each member is fixed by screw tightening. The pressure is held between the flange 5 and the nut 13. A synthetic resin case 1 is molded around the metal sleeve 4. In this synthetic resin case 1, a cylindrical connector portion 17 is formed continuously from the peripheral surface of the main body portion 2, and the tapered shape of the two connection terminal rods 21, 21 described above is formed in the cylindrical wall 16. Enclose the tips 22 and 22 (one is hidden and cannot be seen). The connection terminals 21 and 21 generate a potential difference in proportion to the strain in the thickness direction of the piezoelectric element 8 accompanying the occurrence of knocking. In order to take out this potential difference as a signal voltage, a female coupler 19 is fitted into the connector portion 17 and connected to the connection terminals 21 and 21.
[0011]
FIG. 5 shows the annular piezoelectric element 8, and silver electrode layers 9 and 9 having a thickness of 4 to 10 μm are formed on the front and back surfaces thereof. The annular piezoelectric element 8 is polarized in the thickness direction, and has an inner diameter and an outer diameter substantially the same as those of the electrode plates 20a and 20b. The present invention is characterized in that, in the silver electrode layers 9 and 9 of the annular piezoelectric element 8, electrode removal edges x and y without electrode layers are provided around the inner and outer edges of the front and back surfaces of the annular piezoelectric element. Is.
[0012]
Here, since the electrode plates 20a and 20b are formed by punching a conductive plate material into a predetermined shape, a burr z of up to 40 microns is generated at the inner and outer edges thereof as shown in FIG. Moreover, the electrode plates 20a and 20b are punched and formed in large quantities, sent to the next process by a feeder, and processed. For this reason, when the electrode plates 20a and 20b are arranged on the front and back of the annular piezoelectric element 8 and the nut 13 is rotated, the annular piezoelectric element 8 also follows and rotates due to the shearing force. It contacts the inner and outer edges of the element 8. However, since the electrode removal edges x and y are formed on the inner and outer edges of the annular piezoelectric element 8 as shown in the figure, the silver electrode layers 9 and 9 are not worn by the burr z.
[0013]
Further, when a burr of about 40 μm is generated, the thickness of the electrode layer 9 is also about 4 to 10 μm. Therefore, by applying a preload, the burr is crushed into a minimal step between the surface without the electrode layer and the electrode layer surface. Is almost contained, and no gap is generated between the annular electrode plate and the piezoelectric element due to burrs during lamination.
[0014]
【The invention's effect】
The non-resonant type knock sen of the present invention has an annular electrode plate electrically connected to the electrode layer on the front and back sides of an annular piezoelectric element having electrode layers formed on the front and back surfaces in a case attached to the internal combustion engine. The annular piezoelectric element is held in a pinched state, and the inner diameter and the outer diameter of the annular piezoelectric element are substantially the same as the annular electrode plates disposed on the front and back surfaces, and the inner and outer surfaces of the annular piezoelectric element are inside and outside. Since the electrode removal edge without the electrode layer is provided around the edge, even if burrs are formed on the inner and outer edges of the annular electrode plate in pressure contact with the annular piezoelectric element, the electrode layer of the annular piezoelectric element is not limited to the inner and outer edges. Since it is removed at the edge, the burr comes into contact with the portion without the electrode layer. For this reason, even if the annular piezoelectric element is rotated with respect to the seating surface by tightening a nut or the like, the electrode layer is not removed or worn by the burr, and the characteristics and the like do not change. Also, when burrs occur, the thickness of the electrode layer is also almost within the minimum step between the electrode layer surface and the electrode layer surface, and the burrs cause a gap between the annular electrode plate and the piezoelectric element during lamination. Will not occur. Therefore, problems such as a decrease in the output signal from the piezoelectric element and a change in the capacitance of the piezoelectric element, which impairs the consistency with the signal processing circuit, are prevented, and an extra polishing step is required. Thus, there are excellent effects such as no increase in manufacturing cost.
[Brief description of the drawings]
FIG. 1 is a longitudinal side view of a non-resonant knock sensor.
FIG. 2 is a plan view of an upper annular electrode plate 20a having a connection terminal rod 21. FIG.
FIG. 3 is a side view of an upper annular electrode plate 20a having a connection terminal rod 21. FIG.
4 is a side view of a lower annular electrode plate 20b having a connection terminal rod 21. FIG.
5 is a perspective view of an annular piezoelectric element 8. FIG.
6 is a longitudinal side view exaggeratingly showing a laminated state of the annular piezoelectric element 8 and the annular electrode plates 20a and 20b. FIG.
[Explanation of symbols]
8 annular piezoelectric element 9 silver electrode layer 20a, 20b annular electrode plate 21 connection terminal 杆 x, y electrode removal edge z burr

Claims (1)

An annular electrode plate electrically connected to the electrode layer is disposed on the front and back surfaces of the annular piezoelectric element having electrode layers formed on the front and back surfaces in a case attached to the internal combustion engine. In what is held in the shape,
The inner and outer diameters of the annular piezoelectric element are substantially the same as the annular electrode plates disposed on the front and back sides,
The inner and outer edges of the front and back surfaces of the annular piezoelectric element, a no electrode removal edges of the electrode layer, characterized by being provided around the electrode removal edge for pay burrs produced inside and outside edge of the annular electrode plate Non-resonant knock sensor.

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