JPH09138160A - Knocking detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the reliability while reducing the labor required for assembling work. SOLUTION: A vibration detector 20 comprises a piezoelectric element 21, silver electrodes 22, 23, 25, and a load resistor 24. The piezoelectric element 21 is polarized in the reverse direction to the thickness direction on the opposite sides in radial direction. The load resistor 24 is printed using resistive paste between the silver electrodes 22, 23 of different polarity provided on one end face of the piezoelectric element 21 and the signal voltage of piezoelectric element 21 is generated across the load resistor 24. When a wire harness and a pair of caulked terminal plates are brought into contact with the silver electrodes 22, 23, respectively, signal voltage generated from the piezoelectric element 21 can be delivered to an ECU(electronic control unit). Since the terminal plate is required to be connected electrically with only one end face of the piezoelectric element 21, assembling work is facilitated. Furthermore, labor required for the assembling work can be reduced because the vibration detector 20 comprising arranged with the load resistor 24 can be handled as one component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine (hereinafter referred to as "internal combustion engine").
The present invention relates to a knocking detection device (referred to as "engine"), and particularly to a knocking detection device used for controlling ignition timing of an engine.

[0002]

2. Description of the Related Art Conventionally, there has been known a knocking detecting device which detects knocking by detecting mechanical vibration of an engine as an electric signal. The knocking detection device is often attached to a cylinder block or the like of the engine, which is a vibration detection target, and the vibration transmitted to the cylinder block due to the knocking of the engine is converted into an electric signal by a vibration detection body including a piezoelectric element, for example, and electronically controlled It is output to a unit (hereinafter, "electronic control unit" is referred to as ECU). As such a knocking detection device, Japanese Utility Model Laid-Open No. 58-180427 and Japanese Patent Laid-Open No. 21892/1990.
A non-resonant type knocking detection device disclosed in Japanese Patent No. 7 is known.

However, the actual exploitation of Sho 58-180427
In the knocking detection device disclosed in Japanese Patent Application Laid-Open No. 2-218927 and Japanese Patent Application Laid-Open No. 2-218927, the piezoelectric element as the vibration detecting body is polarized only in one direction in the thickness direction, and therefore terminals are connected to both end surfaces of the piezoelectric element. It is necessary to take out an electric signal. Therefore, there is a problem that the assembling work becomes complicated and the assembling man-hour increases.

In order to solve such a problem, Japanese Unexamined Patent Publication No.
In the vibration sensor disclosed in Japanese Patent No. 63603,
By making the polarization applied in the thickness direction of the piezoelectric element in the opposite direction on the left and right, the terminal is connected only to either side of both end faces of the piezoelectric element and the electrical signal is taken out from this terminal to reduce the assembly time of the terminal. It is decreasing.

[0005]

However, in the vibration sensor disclosed in the above-mentioned Japanese Patent Laid-Open No. 7-63603, the load resistance for extracting the output signal from the piezoelectric element is a member separate from the piezoelectric element. Yes, it is necessary to connect to each terminal separately from the piezoelectric element.
Since the connection of the load resistance is usually performed by caulking, soldering, welding or the like, there is a problem that the number of assembling steps increases.
Further, when connecting by soldering or welding, there is a problem that the reliability of the resistance connecting portion may be impaired due to thermal deformation.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a knocking detection device with a reduced number of assembling steps and a high reliability.

[0007]

According to the knocking detection device of the first aspect of the present invention, by polarizing the piezoelectric element in the opposite direction to the thickness direction, the piezoelectric element is formed from one end face in the thickness direction of the piezoelectric element by the terminal. The electrical signal of can be taken out. Therefore, the terminal can be easily assembled, and the number of assembling steps is reduced.

Further, by disposing a load resistor electrically connected in parallel with both electrodes between electrodes of different polarities provided at intervals on one end face in the thickness direction of the piezoelectric element, the load resistance can be reduced. Since the connected piezoelectric element can be handled as one component, the device can be downsized and the number of assembly steps of the device can be reduced. According to the knocking detection device of the second aspect of the present invention, by disposing the electronic circuit on the same end face of the piezoelectric element in which the load resistor is arranged, the knocking detection device can be made highly functional and the external electronic circuit can be achieved. Since the number of elements of the external electronic circuit is reduced, the circuit configuration of the external electronic circuit can be simplified.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; (First Embodiment) A first embodiment of the present invention is shown in FIGS. As shown in FIG. 2, the knocking detection device 10 is a non-resonance type knocking detection device, and is tightened and fixed by a bolt 60 to a cylinder block 50 of an engine which is a vibration detection target.

The metal base 11 of the knocking detection device 10 is composed of a bottom portion 11a and a tubular portion 11b, and is formed in an inverted T shape. An insulating plate 26, a vibration detector 20, a wire subassembly 40, which will be described later, a weight 33, and a spring washer 34 are inserted into the cylindrical portion 11b in this order on the bottom portion 11a, and each member is attached to the bottom portion 11a by a nut 35. Has been tightened towards. The periphery of each of these members is covered with a resin cover 12 to prevent foreign matter and water from entering.

As shown in FIGS. 1 and 3, one of the notches 21a and 32a formed at the radial ends of the piezoelectric element 21 and the insulating plate 32 of the vibration detector 20 and one of the outer peripheries of the terminal plates 30 and 31, respectively. The notches 30a and 31a formed at the respective places have surfaces formed so as to be in the same direction as the take-out direction of the wire harness 41 to be described later when assembled. Weight 33 not shown
Notches are formed in the same direction on both ends in the radial direction.
This makes it easy to position each member when assembling it and prevent the take-out position of the wire harness 41 from varying depending on each device.

A through hole 11c into which the bolt 60 can be inserted is formed in the axial direction of the base 11. Since a wavy groove 11d having a predetermined width is formed on the outer periphery of the bottom 11a of the base 11 and the outer periphery of the top of the cylindrical portion 11b, the seal length between the base 11 and the cover 12 is long. Therefore, the invasion of water from the outside is prevented well, and the resin biting when the cover 12 is molded is improved.

As shown in FIG. 1, the vibration detector 20 includes a piezoelectric element 21, silver electrodes 22, 23 and 25, and a load resistor 24.
Consists of As shown in FIG. 1A, the piezoelectric element 21
A through hole 21b for inserting into the tubular portion 11b is formed in the central portion of the. As shown in FIG. 1B, the piezoelectric element 21 is polarized in the opposite direction of the thickness direction on both sides in the radial direction across the diameter. The arrow shown in FIG. 1B indicates the polarization direction of the piezoelectric element 21. The polarization of the piezoelectric element 21 is performed by applying high voltage in opposite directions on both sides in the radial direction. Silver electrodes 22 and 23 are formed on one end surface of the piezoelectric element 21 on which electrode surfaces having different polarities are formed, that is, on the upper end surface in FIG. The load resistor 24 is printed between the silver electrodes 22 and 23 by using a resistance paste, and a signal voltage of the piezoelectric element 21 is generated across the load resistor 24. The silver electrode 25 is formed on the opposite side of the silver electrodes 22 and 23, and the silver electrode 22 and the silver electrode 2 are formed.
3 and 3 are electrically connected in series. An insulating plate 26 is provided between the silver electrode 25 and the bottom portion 11a of the base 11 to electrically insulate the silver electrode 25 and the base 11 from each other. The load resistor 24 is provided in two places between the silver electrodes 22 and 23, but it is also possible to provide only one of them.

As shown in FIG. 3, the wire subassembly 40 comprises terminal plates 30 and 31, an insulating plate 32, a wire harness 41 and a rubber plug 42. The terminal plates 30 and 31 are formed in a semi-circular shape, and fixed to the wire harness 41 by caulking. A rubber plug 42 is fitted around the connection portion of the wire harness 41 with the terminal plates 30 and 31. The terminal plates 30 and 31 are provided with notches 30a and 31 so as not to make electrical contact with each other and to prevent the terminal plates 30 and 31 from protruding outward in the radial direction of the base 11 during assembly.
The a and the notch 32a are parallel to each other and attached to the insulating plate 32 with a cyanoacrylate adhesive. Rubber stopper 4
2 is formed in a bellows shape and has a long sealing length with the cover 12, so that intrusion of water from the outside can be favorably prevented.

The weight 33 shown in FIG. 2 is for applying a predetermined set load to the piezoelectric element 21, and the spring washer 34 is for adjusting the fastening force of the nut 35 applied to the piezoelectric element 21. Next, a procedure for assembling the knocking detection device 10 will be described. As shown in FIG. 3, the rubber plug 42 is inserted into the tip of the wire harness 41 to connect the terminal plates 30 and 31 to the wire harness 41.
Secure by crimping. Terminal plates 30 and 31
The insulating plate 32 and the insulating plate 32 are bonded and fixed by aligning the positions of the notches 30a, 31a and 32a to form the wire subassembly 40.

Silver electrodes 22, 2 are attached to the polarized piezoelectric element 21.
3 and 25 are electrically connected to the load resistance 24 to form the vibration detector 20. The piezoelectric elements 21 may be polarized after the silver electrodes 22 and 23 and the load resistor 24 are connected first. The insulating plate 26, the vibration detector 20, the wire subassembly 40, and the weight 3 are attached to the cylindrical portion 11b of the base 11.
3. After inserting the spring washer 34 and aligning the take-out direction of the wire harness 41 with each notch, tighten the nut 35 with a predetermined load.

After assembling the respective members to the base 11 as described above, the assembled product is set in a molding die, and an appropriate portion is clamped so that the wire harness take-out portion does not shift during molding. deep. Then, the mold resin is injected from a molding resin injection port of a molding die (not shown) to cover the cover 1.
2 is formed into a predetermined shape. The knocking detection device 10 thus assembled is fastened and fixed to the cylinder block 50 with bolts 60, and the wire harness 41 is connected to the ECU. The ECU inputs a signal voltage generated at both ends of the piezoelectric element 21 according to the applied stress from the engine, detects the occurrence of knocking based on this signal voltage, and optimally controls the ignition timing of the engine.

In the comparative example shown in FIG. 5, terminal plates 30 and 3 are provided outside the piezoelectric element as a separate member from the piezoelectric element.
1 and the load resistor 70 are connected, and the terminal plates 30 and 31 and the load resistor 70 are connected by caulking, soldering or welding. In the case of connecting the load resistor to the terminal as a member different from the piezoelectric element as in the comparative example, the number of assembling steps increases, and the terminal plates 30 and 3 are formed by soldering or welding.
When the load resistor 70 is connected to 1, the connection portion between the load resistor 70 and the terminal plates 30 and 31 may have a poor connection due to thermal deformation.

On the other hand, in the first embodiment, the piezoelectric element 21
A load resistor 24 is formed by printing between the silver electrodes 22 and 23 formed on one end surface of the one using a resistance paste. Therefore, the vibration detecting body 20 in which the load resistance 24 is arranged on the piezoelectric element 21 can be handled as one component, and it is not necessary to connect an external resistance to the terminal plates 30 and 31, so that the number of assembling steps can be reduced. Furthermore, the silver electrode 22
There is no risk of connection failure at the connection between the load resistors 24 and 23 and the load resistor 24.

(Second Embodiment) A second embodiment of the present invention is shown in FIG.
Shown in In the second embodiment, a disc spring 37 is used instead of the spring washer 34 and the nut 35 of the first embodiment. The disc spring 37 is press-fitted between the weight 33 and the locking portion 11e formed on the top side of the tubular portion 11b. The vibration detector 20 is pressed toward the bottom portion 11a of the base 11 by the set load of the weight 33 and the biasing force of the disc spring 37. The disc spring 37 is biased by the locking portion 11.
It can be easily changed by changing the formation position of e.

In the second embodiment, the disc spring 37, which is a single member, presses the vibration detecting body 20 toward the bottom portion 11a, so that the number of parts and the number of assembling steps can be reduced. In the above-described embodiment of the present invention described above, since both sides of the piezoelectric element 21 in the radial direction are polarized in opposite directions in the thickness direction, assembling of the terminal becomes easier as compared with a piezoelectric element polarized in the same direction. Further, since the polarized portions of the piezoelectric element are connected in series, it is possible to secure substantially the same element capacitance by reducing the thickness of the piezoelectric element, so that the axial length of the device can be shortened.

Further, by disposing an electronic circuit such as a detection circuit on the same end face of the piezoelectric element 21 as the side on which the load resistor 24 is disposed, the amount of elements in the external circuit can be reduced and the configuration of the external circuit can be simplified. At the same time, it is possible to enhance the functionality of the knocking detection device.

[Brief description of the drawings]

1A is a plan view showing a vibration detector according to a first embodiment of the present invention, FIG. 1B is a sectional view taken along line BB of FIG. 1A, and FIG. 6 is a cross-sectional view taken along the line CC of FIG.

FIG. 2 is a sectional view showing a knocking detection device according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a positional relationship between a terminal plate and an insulating plate according to the first embodiment.

FIG. 4 is a plan view showing a knocking detection device before resin molding according to the first embodiment.

FIG. 5 is a plan view showing a comparative example of the first embodiment.

FIG. 6 is a sectional view showing a knocking detection device according to a second embodiment of the present invention.

[Explanation of symbols]

 10 Knocking Detection Device 11 Base 12 Cover 20 Vibration Detection Body 21 Piezoelectric Element 22, 23, 25 Silver Electrode (Electrode) 24 Load Resistance 26 Insulation Plate 33 Weight 34 Spring Washer 40 Wire Subassembly 41 Wire Harness

Claims (2)

[Claims] 1. A piezoelectric element that polarizes in the opposite direction in the thickness direction and converts the vibration of a vibrating body that is a vibration detection target into an electric signal; a weight that applies a load to the piezoelectric element in the thickness direction; and the piezoelectric element. Electrodes having different polarities provided on one of the end faces in the thickness direction at different intervals, a load resistor disposed between the electrodes and electrically connected in parallel with the electrodes, and the electrodes respectively electrically. A knocking detection device comprising: a pair of terminals connected to the. 2. The knocking detection device according to claim 1, wherein an electronic circuit is provided on the same end surface of the piezoelectric element as the side on which the load resistor is provided.