JP3090515B2 - Assembling method of annular piezoelectric sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly of a piezoelectric sensor used in an in-cylinder pressure detector for holding a cylinder head of an engine and detecting a pressure change in the cylinder due to knocking or fuel injection by a piezoelectric element. About the method.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional in-cylinder pressure detecting device of this type is constructed by wrapping an integrated body formed by stacking an annular piezoelectric element and upper and lower buffer rings and the like with a metal outer cover. Various proposals have been made in which an annular piezoelectric sensor S is seated on a plug mounting portion R to apply a distortion to a piezoelectric element in the piezoelectric sensor by a clamping force of an ignition plug T to extract an output signal. More specifically, the plug mounting portion R includes a large-diameter plug insertion hole r ₁ sequentially drilled from the outer surface of the cylinder head P toward the combustion chamber Q, a plug seat r _2, and a small-diameter plug screwing. consists hole r ₃ Prefecture, the plug insertion hole r ₁ from the spark plug T is inserted, is screwed to the male screw t ₁ in screw hole r _3, the seat surface via a gasket ring optionally t ₂ The piezoelectric sensor S on the plug seat r ₂ is strongly pressed between the spark discharge portion t ₂ and the spark discharge portion t ₃ so as to face the combustion chamber Q.

The vibration of the cylinder head P causes a compressive strain in the piezoelectric element in the piezoelectric sensor S, and an output signal synchronized with the vibration is extracted from the piezoelectric element, and is used for detecting knocking and fuel injection timing. Can be

[0004]

As described above, the piezoelectric sensor S is of a type in which the pressure is clamped by tightening a spark plug. It acts through the ring and applies torsional stress in addition to compressive stress. For this reason, the characteristics are deteriorated, and the piezoelectric element having low shear strength is easily broken. In view of the above, the locking member is usually used in combination with a locking member having various structures. However, the use of the locking member complicates the sensor structure, impairs productivity and economy, increases the price, and increases the cost of the piezoelectric sensor S. The spark discharge portion t ₃ of the spark plug T which rises and protrudes into the combustion chamber
Is difficult to set at a predetermined position.

Therefore, the outer peripheral wall is eccentric with respect to the inner peripheral wall, and at least the annular piezoelectric element and the lowermost part are arranged by a metal outer skin having a detent periphery that protrudes radially around the outer peripheral wall. A piezoelectric sensor S has been proposed in which the integrated body including the eccentric ring plate is wrapped and the joint of the metal outer skin is positioned on the lower surface of the eccentric ring plate. Due to the eccentric configuration, the piezoelectric sensor S is formed with a detent periphery that protrudes in the radial direction, so that the torsional stress is not applied to the piezoelectric sensor S by the tightening torque without using the detent member as described above. Things. By the way, in such a configuration, except for the eccentric ring plate, the stack is concentrically fitted to the inner peripheral wall of the metal outer skin, so that a gap is generated between the outer peripheral wall and the stack. This gap creates a usefulness in facilitating wiring for taking out an output signal.
When caulking the metal outer skin by this gap, there is no support at the gap part, so the caulking force is biased,
There arises a problem that it cannot be assembled properly. The present invention has such a configuration and provides an optimal method for assembling an annular piezoelectric sensor.

[0006]

SUMMARY OF THE INVENTION According to the present invention, an outer peripheral wall and an inner peripheral wall are vertically suspended by extending a folding margin at each end of a metal outer cover, and an eccentricity is provided between the two peripheral walls. A storage space is formed in advance in an annular shape, and the eccentric ring plate is positioned at the outermost position in the storage space, and the integrated body is fitted therein, and the storage space is shielded by the eccentric ring plate. An annular piezoelectric sensor which is assembled by crimping the inner peripheral wall so as to closely contact the inner edge of the eccentric ring plate, and then crimping the outer peripheral wall so as to closely contact the outer peripheral edge of the eccentric ring plate. Is an assembling method.

[0007]

The stack is stored in the storage space of the metal shell of the sky and the inner peripheral wall is crimped first, and the aggregate is fitted along the inner peripheral wall to form a solid shape. Therefore, the fixing is secured inside. Then, when the margin of the outer peripheral wall is crimped, since the inside of the eccentric ring plate is held, even if there is a gap between the outer peripheral wall and the aggregate, the aggregate may not be inclined due to the caulking pressure. In addition, uniform caulking can be performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a piezoelectric sensor S will be described with reference to FIG. 1. Reference numeral 1 denotes an integrated body, which is stacked via an insulating plate 4 made of a ring-shaped piezoelectric element 2, an electrode ring 3, alumina and the like. A ring plate 5 made of a metal material such as copper, aluminum or stainless steel is arranged on the upper surface, and an eccentric ring plate 6 of the same material is arranged on the lower surface, and the integrated body 1 is wrapped with a metal outer skin 7 by drawing. The joint 8 is located on the lower surface of the eccentric ring plate 6. The corners of the ring plate 5 and the eccentric ring plate 6 may be chamfered to improve the adhesion to the outer skin 7.

[0009] The piezoelectric sensor S, a metal the shape of the outer peripheral wall 7a of the outer cover 7 substantially coincide with the outer periphery of the plug mount the plug seat r _2, which is formed in the R of the cylinder head P, and plug the plug screw hole the center L of r ₃ by the center D and offset of the plug seat r, plug screw hole r is eccentric with arc center of the outer peripheral wall 7a of the arc center of the inner peripheral wall 7b of the metallic outer skin 7
₃ center L and so as to coincide with (the axis of the spark plug T). As a result, the planar (bottom) shape of the piezoelectric sensor S is formed into an annular shape having different radial widths over the entire circumference, as shown in FIG. 4, and a detent peripheral edge α is formed on the deflection surface of the outer peripheral wall 7a. Is done. Then, the above-mentioned integrated body 1 is
It is arranged along. Here, the upper metal ring plate 5 has an annular shape in which the inner edge and the outer edge are concentric, similar to the piezoelectric element 2, but the eccentric ring plate 6 matches the eccentric shape of the metal outer skin 7, The center of the inner edge and the center of the outer edge are respectively displaced, so that the eccentric ring plate 6 constitutes the bottom plate.

A further description will be given of the means for electrically extracting the piezoelectric sensor S. A connection branch 3a is extended from the electrode ring plate 3 so that the connection branch 3a is displaced within the metal sheath 7 by the deflection of the center of the arc. Peripheral edge and outer peripheral wall 7 of formed integrated body 1
a connecting branch 3a is drawn out of a drawing hole 8 drilled in the metal outer casing 7 immediately above the gap s, and the connecting branch 3a is inserted into the metal guide pipe 9. After that, the guide pipe 9 is fixed to the draw-out hole 8, and a signal transfer lead wire 10 is connected to the connection branch 3 a by soldering 11, and the protection pipe 12 is fitted to the outside.
Thus, an output signal is taken out from the signal carrying lead wire 10.

With such a configuration, the annular piezoelectric sensor S
When pressure is applied to the upper and lower surfaces of the piezoelectric sensor S by the spark plug T, the pressure directly acts on the upper and lower surfaces of the metal outer cover 7 and the piezoelectric force is applied via the ring plate 5 and the eccentric ring plate 6. Acts on element 2. Thus, the piezoelectric element 2 includes:
A voltage proportional to the pressure fluctuation is generated, and the electrode ring plate 3
Is output as an output signal via the signal carrying lead wire 10.

[0012] According to such a structure, the piezoelectric sensor S tightening torque acts by shear stress and pressure upon its seat surface t ₂ mounting the spark plug T, addition torsional stress compressive stress applied to overlap. However the axis of the spark plug T has deviated from the (plug screw hole r ₃ of the center L) and the plug seat r ₂ of the center D (the center of the outer peripheral surface of the piezoelectric sensor S), Therefore, the piezoelectric sensor S is arresting rim α formed on the outer peripheral surface of the non-rotatable and abuts the inner peripheral wall of the plug insertion hole r _1. Therefore, only the compressive stress is applied to the piezoelectric sensor S, and the breakage of the piezoelectric element 2 due to the shear stress is prevented without using the rotation stopper.

[0013] Incidentally, the anti-rotation peripheral α formed on the outer peripheral surface of the piezoelectric sensor S, for example, the peripheral shape of the outer peripheral wall 7a of the metal outer skin 7 as a polygon, which inner peripheral wall of the plug insertion hole r ₁ , A detent edge α is formed on the entire circumference. Also by projecting a part of the peripheral wall 7a outward, and the projecting end with arresting rim alpha, locked in contact with the inner circumferential wall when slightly rotated the projecting end of the plug insertion hole r _1, the rotation May be prevented.

An assembling method of the piezoelectric sensor S having the following configuration will be described. As shown in FIG. 3, in a state before the metal shell 7 is assembled, the metal outer shell 7 extends the folds x and y at its respective ends to vertically separate the outer peripheral wall 7 a and the inner peripheral wall 7 b. It is formed beforehand in a helically annular shape that hangs down and creates an eccentric storage space between the two peripheral walls 7a, 7b. The fold allowance x at the lower edge of the inner peripheral wall 7b is longer than the fold allowance y at the lower edge of the outer peripheral wall 7a. Then, the stack 1 in which the eccentric ring plate 6 is disposed at the lowermost position is fitted concentrically along the inner peripheral wall 7b, and the storage gap is shielded by the eccentric ring plate 6, and as shown in FIG. Each of the folds x and y of the outer cover 7 is folded and swaged, and the joint 13 is positioned on the lower surface.

The caulking means will be described with reference to FIG.
As shown in the lower part of the figure, the folding allowances x and y are caulked individually by caulking tools 20 and 21, respectively. In this procedure, first, the fold allowance x of the inner peripheral wall 7b is bent by the caulking tool 20, and thereafter, the fold allowance y of the outer peripheral wall 7a is
To be bent. That is, in a state where the stack 1 is stored in the storage space of the metal outer cover 7, first, when the bent portion x of the inner peripheral wall 7 b is swaged, the stack 1 is fitted along the inner peripheral wall 7 b, Since the inner peripheral wall 7b has a solid shape on the side of the inner peripheral wall 7b, when the fold x is swaged by the swaging tool 20, the swaging pressure is supported by the integrated body 1, and the fold x is in close contact with the eccentric ring plate 6, The inner edge of the stack 1 is stably held by the folding margin x. Then, when the margin y of the outer peripheral wall 7a is caulked with the caulking tool 21, even if a gap s is generated between the outer peripheral wall 7a and the integrated body 1, the integrated body does not tilt due to the caulking pressure. Uniform caulking can be performed. Thus, the integrated body 1 is tightly wrapped in the metal shell 7 by the caulking.

By the way, in the caulking state as described above, since the folding allowance x is longer than the folding allowance y, as shown in FIG. 1, each of the folding allowances x and y of the metal outer cover 7 is crimped. When the joint 13 is located on the lower surface, the inner end 13a of the joint 13 extends beyond the outer end 13b, and the inner end 13a substantially covers the piezoelectric element 2 from the lower surface. ing. Therefore, when a squeezing pressure acts on the piezoelectric element 2 due to knocking or the like, the pressure acts almost uniformly on the entire lower surface of the piezoelectric element 2 via the inner end portion 13a. Good responsiveness can be obtained without sometimes causing hysteresis.

Further, a joint 13 of the metal outer cover 7 is provided.
The order that is positioned on the lower surface, the joint 13 is in contact plug seat r ₂ and the surface, because the inner end portion 13a and the outer end portion 13b is subjected to a uniform force in the crimping direction, always laminate 1 It is housed tightly in the metal sheath 7 and can produce a stable output.

[0018]

According to the method of assembling the annular piezoelectric sensor of the present invention, as described above, the margin x,
The eccentric ring plate 6 is positioned in the eccentric storage space formed between the outer peripheral wall 7a extending y and the inner peripheral wall 7b, and the integrated body 1 including the piezoelectric element 2 is first fitted therein. Inner wall 7b
Caulking the crease x so that the inner edge of the eccentric ring plate 6 is in close contact,
Next, since the outer peripheral wall 7a is assembled by caulking the fold y of the outer peripheral wall 7 and closely contacting the outer peripheral edge of the eccentric ring plate, even if a gap s is formed between the outer peripheral wall 7a and the integrated body 1, it is caulked. There is an excellent effect that the integrated body does not tilt due to the pressure and can be uniformly caulked.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a main part of an in-cylinder pressure detecting device according to an embodiment of the present invention.

FIG. 2 is a partially cutaway plan view of FIG. 1;

FIG. 3 is a longitudinal sectional side view showing a caulking process of a metal outer cover 7;

FIG. 4 is a bottom view of the piezoelectric sensor S.

FIG. 5 is a longitudinal sectional front view schematically showing a cylinder pressure detecting device according to a conventional example.

[Explanation of symbols]

 S Piezoelectric sensor 1 Integrated body 2 Piezoelectric element 5 Metal ring plate 6 Eccentric ring plate 7 Metal outer skin 7a Outer peripheral wall 7b Inner peripheral wall 13 Joint x, y Folding s Gap α Peripheral edge

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-15838 (JP, A) JP-A-5-118946 (JP, A) Fully open 1987-6-5244 (JP, U) Really open 1986 104348 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01L 23/22

Claims (1)

(57) [Claims] An outer peripheral wall is eccentric with respect to an inner peripheral wall, and at least a ring-shaped piezoelectric element and a lowermost part are disposed by a metal outer cover formed with a detent periphery extending radially around the outer peripheral wall. The metal shell is wrapped around the stack including the eccentric ring plate, and the joint of the metal shell is positioned on the lower surface of the eccentric ring plate, and is sandwiched between the plug seat formed in the plug mounting portion of the cylinder head and the spark plug. In the annular piezoelectric sensor that detects the pressure in the cylinder while being held under pressure, the outer peripheral wall and the inner peripheral wall vertically hang down by extending the metal outer cover at each end, and both peripheral walls An eccentric storage gap is formed between the eccentric rings in advance, the eccentric ring plate is positioned at the outermost position in the storage gap, and the integrated body is fitted therein, and the storage gap is shielded by the eccentric ring plate. At the same time, first, make allowance for the inner peripheral wall In close contact with the inner edge of the eccentric ring plate Te, then the method of assembling the annular piezoelectric sensor, characterized in that assembled by closely folding strip of the outer peripheral wall on the outer periphery of the eccentric ring plate by caulking.