JP3827369B2 - Manufacturing method of knocking detection sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a knocking detection sensor for detecting knocking of an internal combustion engine such as an automobile engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a sensor for detecting knocking that occurs in an engine of an automobile or the like, a sensor that detects vibration caused by the knocking using a detection element such as a piezoelectric element has been widely used. In such a knocking detection sensor, a vibration detector having a piezoelectric element plate fixed to one side of a metal diaphragm is accommodated in the inner space of the casing, and the output from the piezoelectric element plate accompanying the addition of vibration is It is taken out of the casing by the connected terminal. Here, the vibration detection body is generally fixed to the casing by screwing, but there are disadvantages such as the number of parts increases by the use of the screw and the time required for making the screw hole. . Thus, attempts have been made to join the diaphragm to the fixed protrusion by resistance welding (projection welding) to reduce the number of parts and simplify the assembly process. In this case, the tip of the fixed protrusion is brought into contact with the plate surface of the vibration plate and pressurized, and resistance heat is concentrated on the contact portion by passing an electric current through this to perform welding.
[0003]
[Problems to be solved by the invention]
By the way, the piezoelectric element plate used for the knocking detection sensor is subjected to polarization treatment prior to assembly to the casing in order to orient the direction of spontaneous polarization of the crystal in one direction. However, when the above-described projection welding is performed, heat generated in the welded portion is transmitted to the piezoelectric element plate through the thin diaphragm, and there is a problem that the orientation of the spontaneous polarization of the crystal is disturbed and the sensor characteristics are easily impaired. In addition, there is a concern that the adhesive layer that joins the piezoelectric element plate to the vibration plate is thermally altered and the joining state of the two deteriorates.
[0004]
An object of the present invention, the vibration detector by resistance welding by bonding to the casing, reduces the number of assembly steps and parts, moreover deterioration occurs difficulty innocua Kkingu detection sensor of the sensor characteristics due to thermal effect in welding It is in providing the manufacturing method of.
[0005]
[Means for solving the problems and actions / effects]
In the present invention, in order to detect knocking generated in an internal combustion engine, a vibration detector in which a piezoelectric element plate is laminated and integrated on one surface of a metal diaphragm is accommodated in an inner space of a casing. In order to solve the above-described problem, a vibration detector in which a piezoelectric element plate is laminated and integrated on one plate surface of the vibration plate is connected to the other plate surface of the vibration plate. The end of the fixed protrusion provided to protrude from the bottom of the inner space of the casing in the endothermic protrusion integrally provided so as to protrude from the plate surface and increase the thickness of the diaphragm at the protruding position. It is characterized by being fixed by resistance welding.
[0006]
That is, since the vibration plate of the vibration detector is fixed to the fixed protrusion in the casing by resistance welding, the number of assembly steps is larger than that of a conventional knocking detection sensor in which the vibration detector is attached by screwing. And the number of parts can be reduced. The diaphragm is welded to the fixed protrusion at the endothermic protrusion that protrudes from the plate surface, so that heat generated by the welding is absorbed by the endothermic protrusion and is not easily transmitted to the piezoelectric element plate. Deterioration of characteristics is prevented or suppressed. In addition, when the vibration plate and the piezoelectric element plate are bonded to each other by adhesive, it is possible to prevent the deterioration of the bonded state due to thermal alteration of the adhesive.
[0007]
The endothermic protrusion can be easily formed by joining a plate member separate from the diaphragm to the plate surface of the diaphragm by brazing or welding. On the other hand, the endothermic protrusion may be formed integrally with the diaphragm by forging or cutting the plate member.
[0008]
Next, a convex portion projecting from the distal end surface can be formed continuously or intermittently on the distal end surface of the fixed projecting portion, and the endothermic projecting portion can be fixed to the convex portion. As a result, the contact area between the endothermic protrusion and the fixed protrusion is reduced by the formation of the protrusion, and the current during resistance welding is concentrated here, so that the two can be reliably joined. In addition, the said convex part can be made into the convex strip part formed along the periphery of the said front end surface.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. Figure 1 is a knocking detection sensor manufactured by the present invention (hereinafter, simply referred to as a sensor) shows an example of a 1 in cross-section structure, vibration detection member 2, terminal 3, terminal holder 4, the casing 5, the seal A member 6 is provided.
[0010]
As shown in FIG. 2, in the vibration detector 2, a piezoelectric ceramic (for example, PZT (zircon), for example, is formed on one plate surface of a vibration plate 30 made of a metal such as an Fe-42 wt% Ni alloy. The piezoelectric element plate 31 formed into a disk shape by lead oxalate titanate) is fixed via an adhesive layer (not shown), and protrudes from the plate surface at the center of the other plate surface of the diaphragm 30. An endothermic protrusion 32 is provided. As shown in FIG. 2A, the endothermic protrusion 32 is formed by, for example, using a metal plate 33 formed of a metal having the same material as that of the diaphragm 30 and having a smaller diameter than the diaphragm 30 as a brazing material layer ( For example, it is formed by bonding to the diaphragm 30 via a copper brazing layer) 34. The endothermic protrusion 32 is preferably made of the same material as that of the diaphragm 30, but may be made of a different material. In the latter case, as the material of the endothermic protrusion 32, a material having the same or larger hardness as that of the diaphragm 30 and capable of satisfactorily transmitting the vibration associated with knocking to the diaphragm 30 is used. Is good.
[0011]
As shown in FIG. 1, the vibration detection body 2 is accommodated in a recess (inner space) 7 a of a metal shell 7 that forms the lower side of the casing 5. A mounting portion 7b is formed projecting downward from the center of the lower surface of the metal shell 7, and a screw portion 7c for mounting the sensor 1 to an engine block (not shown) is formed on the outer peripheral surface thereof. On the other hand, a fixed protrusion 35 protruding upward from the bottom surface 7d is formed at the center of the bottom surface 7d of the recess 7a, and the vibration detecting body 2 has a tip end surface 35a of the fixed protrusion 35 at the endothermic protrusion 32. Are joined by resistance welding. The fixed protrusion 35 is integrally formed with the metal shell 7 by forging or cutting. For example, when the endothermic protrusion 32 is made of an Fe-42 wt% Ni alloy, the material can be welded with it, and vibrations associated with knocking can be satisfactorily transmitted to the diaphragm 30. For example, mild steel can be preferably used.
[0012]
As shown in FIG. 2 (b), a protrusion 35 b is formed along the outer edge of the distal end surface 35 a of the fixed protrusion 35, and between the protrusion 35 b and the endothermic protrusion 32. A resistance weld 36 is formed so that the two are joined. In addition, the outer peripheral surface 35c of the fixed protrusion 35 is a tapered surface so that the diameter of the distal end surface 35a is reduced. In the center of the vibration plate 30 and the endothermic protrusion 32, holes 30a and 32a penetrating them in the thickness direction are formed. Further, a through hole 31a having a diameter larger than that of the through hole 30a of the diaphragm 30 is formed in the center of the piezoelectric element plate 31, and the upper surface side periphery of the through hole 30a of the diaphragm 30 is formed in the through hole 31a. The part 30b is exposed.
[0013]
Returning to FIG. 1, on the upper surface side of the piezoelectric element plate 31, an electrode portion is formed by coating a metal layer, and one end of the wire 11 for connection is soldered. The terminal 3 is formed in an L shape by bending the lower end side of the band-shaped metal member to the side. On the other hand, as shown in FIGS. 3A and 3B, the terminal holder 4 is a plastic member integrally molded with the terminal 3, and has a circular plane shape and covers the vibration detector 2 from above. The center portion of the terminal 3 is formed in an inverted dish shape, and one side of the terminal 3 is cut away to form a window-like open portion 4a. A bent portion of the terminal 3 is embedded and integrated at the center of the top portion, and a lower end portion 3b of the terminal 3 bent sideways protrudes into the open portion 4a from the side surface of the open portion 4a. . Further, the tip of the lower end portion 3b of the terminal 3 is bent slightly upward, and the other end side of the wire 11 for connection is soldered here.
[0014]
On the other hand, the upper end side of the terminal 3 extends upward from the top surface of the terminal holder 4. An annular ridge portion 12 is formed on the top surface of the terminal holder 4 so as to surround the terminal 3, and a concave portion 13 is formed on the inside thereof. Silicon rubber is cast into the recess 13 to form the seal member 6. Specifically, the seal member 6 is integrally formed with the terminal 3 and the terminal holder 4 by injecting and curing the uncured silicone rubber having fluidity into the recess 13. As the silicone rubber, for example, heat-curing vinyl silicone rubber or phenyl silicone rubber is used.
[0015]
Next, as shown in FIG. 1, the upper side of the casing 5 is a cover member (second portion) 14 that is separate from the metal shell 7. As shown in FIGS. 4A and 4B, the cover member 14 is a plastic molded body whose center portion bulges upward corresponding to the terminal holder 4, and as shown in FIG. 4 (and vibration detection body 2) are arranged so as to cover from the upper side, and are supported by the upper surface outer edge portion of the metal shell 7 via a sealing member 15 such as an O-ring at the lower surface outer edge portion. Further, at a position corresponding to the terminal 3, a terminal insertion hole 16 through which the upper end side of the terminal 3 is inserted and led to the outside of the casing 5 is formed at the top.
[0016]
As shown in FIG. 4B, an annular ridge 17 is formed around the terminal insertion hole 16 on the inner surface side of the cover member 14 so as to surround the terminal insertion hole 16. The ridge portion 17 is formed to have a smaller diameter than the ridge portion 12 (FIG. 1) on the terminal holder 4 side, and abuts against the seal member 6 and elastically bites into the seal member 6 from above, whereby the seal member 6, a closed sealing surface is formed so as to surround the terminal 3. This prevents water or the like from entering the casing 5 from the terminal insertion hole 16.
[0017]
Next, a stepped portion formed on the outer edge portion of the cover member 14 is formed on the outer edge portion of the upper surface of the metal shell 6 with the upper portion of the cylindrical portion 18 a (FIG. 6) formed over the entire circumference of the metal shell 7 . By caulking inward toward the surface 14b, a caulking joint 18 for joining and integrating the metal shell 7 and the cover member 14 is formed.
[0018]
Hereinafter, a method for assembling and using the sensor 1 will be described.
First, as shown in FIG. 5A, the endothermic protrusion 32 is formed by brazing a metal plate 33 to one plate surface of the diaphragm 30. Next, the vibration detecting body 2 is obtained by bonding a disk-shaped piezoelectric element plate 31 having a through-hole 31a formed at the center thereof to the other plate surface of the vibration plate 30 using an adhesive. The diaphragm 30 has an exposed portion 30b in the through hole 31a. Next, one end of the connection wire 11 is joined to the upper surface of the piezoelectric element plate 31 bonded to the vibration plate 30 by soldering. Then, the endothermic protrusion 32 is joined to the fixed protrusion 35 on the metal shell 7 side by projection welding. Specifically, the lower surface of the endothermic protrusion 32 is overlaid on the tip surface 35 a of the fixed protrusion 53, and the tip of the electrode 50 is applied to the exposed portion 30 b of the diaphragm 30 in the through hole 31 a of the piezoelectric element plate 31. Yeah. And it supplies with electricity with the welding power supply 51, pinching | interposing the vibration detection body 2 between the electrode 50 and the fixed protrusion part 35 with the pressurization mechanism which is not shown in figure.
[0019]
As shown in FIG. 5B, the current is collected on the tip surface 35a of the fixed protrusion 35 whose side surface is a tapered surface 35c, and further concentrated on the contact portion between the protrusion 35b and the endothermic protrusion 32. And the welding part 36 shown in FIG.2 (b) is formed by the resistance heat_generation | fever, and the heat absorption protrusion part 32 and the fixed protrusion part 35 are joined. At this time, heat generated by welding is absorbed by the endothermic protrusion 32 and is not easily transmitted to the piezoelectric element plate 31, and deterioration of sensor characteristics due to thermal effects is prevented or suppressed. Further, thermal alteration of the adhesive layer that joins the vibration plate 30 and the piezoelectric element plate 31 is prevented or suppressed.
[0020]
For example, when the piezoelectric element plate 31 is composed of PZT, the orientation state of spontaneous polarization of the crystal obtained by the polarization treatment is greatly impaired when the instantaneous heating temperature accompanying welding exceeds 180 ° C., and the sensor output characteristics are sufficient. There is a risk that it will not be secured. In this case, it is desirable that the height t2 of the endothermic protrusion 32 is set so as to absorb the heat generated by welding and the instantaneous heating temperature of the piezoelectric plate 31 does not exceed 180 ° C. In this case, t 2 is appropriately set according to the welding conditions and the value of the thickness t 1 of the diaphragm 30. For example, the thickness t 1 of the diaphragm 30 is 0.5 mm and the welding condition is 1.9 kA. In the case of 50 msec, if t2 is set to 1 mm or more, preferably 1.5 mm or more, the heat generated by welding is sufficiently absorbed by the endothermic protrusion 32, and the instantaneous heating temperature of the piezoelectric element plate 31 is set to the above value or less. can do.
[0021]
When the welding of the vibration detector 2 to the fixed protrusion 35 is completed, as shown in FIG. 6, the other end side of the connecting wire 11 is connected to the lower end 3 b of the terminal 3 by soldering. In this state, the lower edge portion of the terminal holder 4 is fitted and fixed to a step portion 7 f formed along the upper edge of the inner surface of the concave portion 7 a of the metal shell 7. Subsequently, an O-ring-shaped seal member 15 is attached to the metal shell 7, and a cover member 14 is attached so as to cover the terminal holder 4 while inserting the upper end side of the terminal 3 into the terminal insertion hole 16. To do. At this time, the mounting of the cover member 14 is guided by the inner peripheral surface of the cylindrical portion 18 a of the metal shell 7. Then, the upper portion of the cylindrical portion 18a (FIG. 6) is caulked toward the stepped surface 14b of the cover member 14 to form the caulking coupling portion 18 (FIG. 1), and the sensor 1 is assembled. At the time of caulking, the ridges 17 of the cover member 14 are pressed against the seal member 6 and elastically bite into the seal member 6, while the seal member 15 is compressed between the cover member 14 and the metal shell 7 to join them. To seal.
[0022]
The sensor 1 assembled as described above is attached to the engine block at the threaded portion 7 c of the metal shell 7, and vibrations generated when the engine is knocked are transmitted to the vibration detector 2. The vibration detection body 2 converts the vibration into an electric signal by the piezoelectric effect and outputs it from the terminal 3.
[0023]
As shown in FIG. 7, the endothermic protrusion 32 may be formed integrally with the diaphragm 30 by forging or cutting a plate member. In addition, as shown in FIG. 8, the outer peripheral surface of the fixed protrusion 35 can be a cylindrical surface 35e that is substantially perpendicular to the bottom surface 7d of the recess 7a (FIG. 5B), instead of being a tapered surface. On the other hand, as shown in FIG. 9, the endothermic protrusion 32 can have a reduced diameter on the welding side with the fixed protrusion 35, for example, by making the outer peripheral surface a tapered surface 32 c. Thereby, in the endothermic protrusion 32 side, resistance heat generation can be concentrated on the reduced diameter side, and as a result, the joining state between the endothermic protrusion 32 and the fixed protrusion 35 can be further improved. .
[Brief description of the drawings]
FIG. 1 is a front sectional view showing an example of a knocking detection sensor of the present invention.
2 is an enlarged cross-sectional view of a main part of the knocking detection sensor of FIG. 1;
FIG. 3 is a plan view and a front sectional view of a terminal and a terminal holder.
FIG. 4 is a plan view and a front sectional view of a cover member.
FIG. 5 is a process explanatory view showing a method for assembling the sensor of FIG. 1;
6 is a process explanatory diagram following FIG. 5. FIG.
FIG. 7 is a cross-sectional view showing an example in which an endothermic protrusion and a diaphragm are integrally formed.
FIG. 8 is a cross-sectional view showing an example in which the side surface of the fixed protrusion is a cylindrical surface.
FIG. 9 is a cross-sectional view showing an example in which the outer peripheral surface of the endothermic protrusion is a tapered surface.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Knocking detection sensor 2 Vibration detection body 7 Main metal fitting 7a Recessed part (inside empty part)
7d Bottom surface 30 Diaphragm 31 Piezoelectric element plate 32 Endothermic projection 33 Metal plate 34 Brazing material layer 35 Fixed projection 35a Tip surface 35b Projection

Claims (5)

Knock having a structure in which a vibration detection body in which a piezoelectric element plate is laminated and integrated on one plate surface of a metal vibration plate is housed in an inner space of a casing in order to detect knocking generated in an internal combustion engine In the manufacturing method of the sensor, the vibration detecting body in which the piezoelectric element plate is laminated and integrated on one plate surface of the vibration plate protrudes from the plate surface to the other plate surface of the vibration plate , and In the endothermic protrusion integrally provided so as to increase the thickness of the diaphragm at the protrusion position, the heat absorption protrusion is fixed to the tip of the fixed protrusion provided to protrude from the inner bottom surface of the casing by resistance welding. A manufacturing method of a knocking detection sensor.   The method of manufacturing a knocking detection sensor according to claim 1, wherein the endothermic protrusion is formed by joining a plate member separate from the diaphragm to the plate surface of the diaphragm by brazing or welding.   The method of manufacturing a knocking detection sensor according to claim 1, wherein the endothermic protrusion is integrally formed with the diaphragm by forging or cutting a plate member. 4. The convex portion projecting from the distal end surface is formed continuously or intermittently on the distal end surface of the fixed projecting portion, and the endothermic projecting portion is fixed to the convex portion. A method of manufacturing the knocking detection sensor according to claim 1.   The method of manufacturing a knocking detection sensor according to claim 4, wherein the convex portion is a convex strip portion along a peripheral edge of the tip end surface.

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