JPH0519787Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a configuration in which the connector plug is integrally formed with a resin material that surrounds a common part of a knocking sensor, the elastic modulus of the resin material of the plug is By selecting a specific range, unnecessary vibrations of the plug can be suppressed.

(Prior art) A knocking sensor is a sensor in which a small common part of a sensor including a piezoelectric element is surrounded by a resin material, and a connector plug from which a terminal of a piezoelectric element electrode protrudes is integrally formed in the resin material. , 4, a piezoelectric element d, an insulating plate f, and a weight g having electrode plates c and e on both sides of the flange b of a sleeve a, through which a vault attached to the cylinder block of an internal combustion engine passes through the center. A sensor h is provided, and a mold i is applied to the outer periphery of the sensor h using a resin material except for the lower surface of the flange b and the upper end surface of the sleeve a,
A connector plug j provided with terminals k and l connected to electrode plates c and e is protruded from the outer periphery of the mold, and a female connector m is tightly fitted into the plug j for connection. In addition, in the example shown in Fig. 5, a sensor h _-1 consisting of a piezoelectric element d _-1 and a weight g _-1 is fixed to the bottom of a caulking case a _-1 , and a resin material i is attached to the upper opening of the caulking case a _-1 . _-1 and place the electrode plate c _-1 on top of it.
A connector plug j _-1 , which has terminals k _{-1 and} l _-1 connected to e _-1 inside, protrudes from the top surface, and a female connector m _-1 is tightly fitted into the plug so that connection can be made.

(Problems to be Solved by the Invention) However, the connector plugs j, j _-1 , etc. resonate in the radial direction of the arrow x in FIG. 6 along with the vibration of the internal combustion engine. Therefore, the original output characteristic of the sensor is
As shown by the solid line in the figure, the output voltage actually rises abnormally at 2 to 3 KHz and around 10 KHz, which corresponds to the knocking frequency of the internal combustion engine, as shown by the chain line. This rise is caused by the resonance of the connector plug b being added as a noise component, and has the disadvantage that knocking detection becomes unclear.

As a result of intensive study on the above-mentioned resonance phenomenon of the connector plug, the present inventor found that the resonance phenomenon of the plug is caused by the rigidity of the resin material constituting the connector plug.

In other words, this type of knocking sensor is firmly attached to the body of an internal combustion engine, so the outer case mold is made of a resin material with high strength, high rigidity, and excellent heat resistance, usually glass fiber.
% or more, such as polybutylene terephthalate (PBT) resin, is used, but since the connector plug is also molded integrally with the mold, the bending elastic modulus is 12 × 10 ⁴
It has high rigidity of Kg/cm ² or more, and therefore has a large Q.
This is because it becomes easier to resonate.

(Means for solving the problem) The present invention aims to solve the problem mentioned in the previous section. ,
In a knocking sensor, in which a connector plug is formed with a terminal protruding inside that is electrically connected to an electrode plate, and a female connector is tightly connected to the connector plug, the resonance level is minimized from being added as noise to the sensor output. Allowable bending modulus of elasticity 10×
Relating to a knocking sensor plug characterized in that the connector plug is formed of a resin material having a value of 10 ⁴ Kg/cm ² or less, it is possible to effectively suppress resonance of the connector plug that is harmful to sensor output detection. .

(Example) The principle behind the establishment of this invention is as follows.

As shown by the chain line in Fig. 7, the maximum spurious of the conventional knocking sensor occurs near the frequency of 10 KHz, so as shown in Fig. 1, the magnitude of the spurious pattern is taken as _VN and is representative of the sensor output. If we take the output voltage of 1KHz as a point and set it as V,
The influence of the noise component due to the resonance of the connector plug on the sensor output can be determined by the following formula: R=V _N /V _S (R is the mantissa)...Equation 1.

On the other hand, 0% glass fiber (second
Dot 1 in the figure, the same applies hereafter), 5% (dot 2), 10%
(3 RBIs), 15% (4 RBIs), 20% (5 RBIs), 30%
(Point 6) The third,
Molds i and i _-1 in Figure 5 and connector plugs j,
Configure j _-1 .

The results of the study on the relationship between R and the bending elastic modulus are shown in FIG. In Figure 2, it is optimal to select R to be 0.3, which is the minimum allowable value for the resonance level of the connector plug to be added as noise to the sensor output, so the bending elastic modulus is 10×10 ⁴ Kg/ ^cm2 or less.

In the present invention, the resin material forming the connector plug of the knocking sensor has a bending elastic modulus of 10×10 ⁴ Kg/cm ² or less based on the graph in FIG. 2.

In the above example, PBT resin was used as the resin material, but in the present invention, any resin may be used as long as it has a bending elastic modulus of 10×10 ⁴ Kg/cm ² or less.

(Effect) The present invention reduces the Q of the connector plug by selecting a bending elastic modulus of the resin material of 10×10 ⁴ Kg/cm ² or less for the connector plug resonance suppression effect produced by fitting the female connector. This has the advantage of suppressing the resonance and significantly improving the S/N ratio.

[Brief explanation of the drawing]

Figure 1 is a graph illustrating Equation 1 for calculating the influence of the connector plug on sensor output, and Figure 2 shows R (mantissa) obtained by Equation 1 on the vertical axis and the bending elastic modulus on the horizontal axis. 3 is a longitudinal sectional view of the center showing an example of the knocking sensor, FIG. 4 is a plan view of the same, and FIG. 5 is a longitudinal sectional view of the center showing another example of the knocking sensor. FIG. 6 is a front view showing radial resonance of the connector plug, and FIG. 7 is a graph showing an abnormal rise in the knocking sensor output voltage.

Claims (1)

[Claims for Utility Model Registration] A connector plug is formed in a resin member that partially surrounds a sensor including a piezoelectric element having electrode plates on both sides, and has a terminal protruding inside that is electrically connected to the electrode plate, and the connector plug In a knocking sensor that suppresses the vibration of the connector plug as much as possible by tightly connecting a female connector to the sensor, the bending elastic modulus is such that the resonance level of the connector plug is minimally allowed to be added as noise to the sensor output. A knocking sensor plug characterized in that the connector plug is formed of a resin material having a value of 10×10 ⁴ Kg/cm ² or less.