JP2550077Y2 - Knock sensor for internal combustion engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock sensor mounted on an engine body (cylinder block or the like) for detecting knocking in a combustion chamber of an internal combustion engine and detecting vibration thereof.

[0002]

2. Description of the Related Art As a knock sensor of this kind, there is a center hole type in which a mounting hole is formed in a center portion (see Japanese Utility Model Laid-Open No. 2-113133). That is, as shown in FIG. 3, the base of the cylindrical portion 1a is formed on the outer periphery of the cylindrical portion 1a of the metal housing 1 including the cylindrical portion 1a and the flange 1b at the base end thereof via the insulating sleeve 2 made of resin. From the end side to the front end side, a ground side lead plate 3, a piezoelectric element 4 (see FIG. 4), an output side lead plate 5, an insulating sheet 6, and a metal weight 7 for applying a stress to the piezoelectric element 4 by vibration acceleration. Each of the annular members is inserted in turn, and the threaded portion 1 on the outer periphery of the cylindrical portion 1a is
The nut 9 is screwed and fastened together.

[0003] These piezoelectric elements 4, weights 7,
The periphery of the nut 9 and the like is covered with a mold resin 10 to form a case. The ground-side lead plate 3 and the output-side lead plate 5 are led out through terminals 12 and 13 to a connector 11 that is disposed so as to protrude substantially in the radial direction of the cylindrical portion.

In such a knock sensor, a bolt (not shown) is inserted through a hollow portion 1c of a cylindrical portion 1a, and the knock sensor is attached to a cylinder block or the like with the bolt. When the knock sensor receives the vibration of the cylinder block or the like, the knock sensor generates an electric signal corresponding to the vibration acceleration in the piezoelectric element 4 and outputs the signal to an external control unit, thereby detecting the knocking vibration in the control unit. Is what you do.

[0005]

However, in such a conventional knock sensor, since the connector 11 is provided so as to protrude substantially in the radial direction of the cylindrical portion 1a, as shown in FIG. There is a problem that swell of the frequency characteristic occurs due to the asymmetry of the knock sensor.

Therefore, there is a piezoelectric element in which a non-polarized portion is formed on the connector side or the non-connector side of the piezoelectric element to avoid the influence of asymmetry (Japanese Patent Laid-Open No. 2-154).
119, JP-A-2-218927, JP-A-2-221820 and JP-A-2-221819), but these have the disadvantage that the manufacturability is inferior, and the connector side of the piezoelectric element is cut off. There is a missing part (Japanese Utility Model Laid-Open No. 2-41129), but there is an inconvenience that simply cutting out the connector side is still insufficient for flattening the frequency characteristics.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a knock sensor having good manufacturability and having stable frequency characteristics without disturbance in frequency characteristics.

[0008]

In order to achieve the above object, the present invention provides a housing cylinder comprising a cylindrical portion into which a bolt for fitting to an engine body is fitted and a flange formed at a base end thereof. A piezoelectric element is disposed on the outer periphery of the internal combustion engine, and a terminal for output extraction connected to the piezoelectric element is led out to a connector provided so as to protrude in a substantially radial direction of the cylindrical portion. in the knock sensor, the piezoelectric element, the central angle formed by two arc-shaped body of less than 180 degrees, by relatively disposed across the cylindrical portion in a direction substantially perpendicular to the projecting direction of the connector , The circumferential space between these two arcs
It is configured to be filled with resin .

[0009]

According to the above arrangement, no piezoelectric element is arranged on the connector side and the opposite side of the connector, which are largely affected by the asymmetry of the knock sensor, and a knock signal is not taken out of these portions so that the connector is not connected. Only a signal having stable frequency characteristics can be obtained from the two arc-shaped piezoelectric elements arranged to face each other with the cylindrical portion interposed therebetween in a direction substantially perpendicular to the protruding direction of the piezoelectric element.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same parts as those of the conventional example are denoted by the same reference numerals, and the description of those parts will be omitted. As shown in FIG. 1, a piezoelectric element (for example, PZT) is formed of two arc-shaped bodies 4a and 4b having a central angle of substantially 90 degrees, and a cylindrical portion 1a is formed in a direction substantially perpendicular to the projecting direction of the connector 11. Are arranged to face each other.

The portions of the connector 11 and the side opposite to the connector where the arc-shaped members 4a and 4b do not exist are filled with resin when the case resin is molded. Since the vibration of the connector 11 does not appear in the signal of the piezoelectric element, the frequency characteristic of the knock sensor using such a piezoelectric element is flattened as shown in FIG.

As described above, according to the present embodiment,
No piezoelectric elements are placed on the connector side and anti-connector side where the knock sensor has a large effect of asymmetry. Since a knock signal is taken out from the element, a knock sensor with good flatness and frequency characteristics can be realized with good manufacturability.

[0013]

[Effect of the invention] As described above, according to the invention,
A piezoelectric element is not placed on the connector side and the opposite side of the connector, which has a large influence of the asymmetry of the connector protruding in the radial direction of the cylindrical part, so that knock signals are not taken out, and the direction of the connector is almost perpendicular to the projecting direction. Since a signal is extracted from the two arc-shaped piezoelectric elements arranged, a knock sensor having good flatness and good frequency characteristics without swelling of the conventional frequency characteristics can be realized with good manufacturability. .

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a knock sensor showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating frequency characteristics of the knock sensor according to the present embodiment.

FIG. 3 is a cross-sectional view of a conventional knock sensor.

FIG. 4 is a perspective view of a conventional piezoelectric element.

FIG. 5 is a diagram showing a frequency characteristic of a conventional knock sensor.

[Explanation of symbols]

 1a Cylindrical part 1b Flange part 4a Arc-shaped body 4b Arc-shaped body 7 Weight 11 Connector 12 Terminal 13 Terminal

Claims (1)

(57) [Scope of request for utility model registration] 1. A piezoelectric element is disposed on the outer periphery of a cylindrical portion of a housing comprising a cylindrical portion into which a bolt for mounting to an engine body is fitted and a flange formed at a base end thereof, and is fixed together with a weight by fastening. A knock sensor for an internal combustion engine in which a terminal for output takeout connected to the piezoelectric element is led out to a connector provided so as to protrude substantially in the radial direction of the cylindrical portion; wherein the piezoelectric element has a central angle of less than 180 degrees. It is formed by two arc-shaped bodies, and is disposed so as to be opposed to the cylindrical portion in a direction substantially perpendicular to a projecting direction of the connector.
A knock sensor for an internal combustion engine, characterized in that a circumferential space between the two arc-shaped bodies is filled with a resin .