JPS6117288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking detector that detects knocking based on vibrations of an internal combustion engine.

It is known that knocking in an internal combustion engine can be detected by attaching a vibration detector using a piezoelectric element to the engine body and measuring the output voltage caused by the vibration. This takes advantage of the fact that when knocking occurs, combustion occurs rapidly, creating shock waves within the combustion chamber that are transmitted to various parts of the engine as particularly large vibrations.

A conventional vibration detector using a piezoelectric element has a structure in which an inertial mass is mounted on the piezoelectric element, and a bolt is passed in the axial direction to tightly attach the inertial mass and the piezoelectric element to a housing. For this reason, the force applied to the piezoelectric element varies greatly depending on the tightening torque of the bolt, etc. Also, since the coefficient of thermal expansion between the piezoelectric element, the inertial mass, and the bolt differs, the stress applied to the piezoelectric element also changes depending on the temperature. This has the drawback of requiring careful consideration of the tightening torque, etc. during assembly.

Therefore, the present invention includes a housing that is attached to an internal combustion engine and vibrates together, and a housing that is in contact with the housing on one side and the other side is connected to a conductor that outputs electrical output to the outside via a conductive spring member. A piezoelectric element attached to the housing and pressed against the piezoelectric element and the housing with a constant load via the conductor and the spring member.
By attaching and fixing the piezoelectric element to the casing and also including a spring member and an insulating spacer that electrically insulates the conductor from the casing, the set load applied to the piezoelectric element is determined by the spring member and is controlled by the thermal expansion of each component. To provide a knocking detector that can absorb stresses caused by differences and variations in processing accuracy with a spring member, prevent damage to the piezoelectric element during assembly, and also use the spring member as an electrode, making the structure simple and inexpensive. The purpose is to

The present invention will be explained below with reference to embodiments shown in the drawings.
FIG. 1 shows a structural cross section of a knocking detector according to an embodiment of the present invention. Reference numeral 1 denotes a housing which is attached to an internal combustion engine main body (not shown) through a threaded portion 1a and vibrates integrally with the internal combustion engine main body. A piezoelectric element 2 is polarized by elastic strain and generates charges at both ends. One end surface of the piezoelectric element 2 is in contact with the inner bottom surface of the casing 1, and the other end is in contact with a leaf spring 3 made of a conductive member. As shown in the figure, the leaf spring 3 has a cylindrical structure in the shape of a truncated cone. Reference numeral 4 denotes a conductor that takes out electrical output to the outside via the leaf spring 3. 5 holds the piezoelectric element 2 in the housing 1 with a constant load using the conductor 4 and the leaf spring 3.
It is an insulating spacer that electrically insulates the leaf spring 3 and the conductor 4 from the housing 1 while being pressed against the housing 1, and is fixed by wrapping around the opening edge 1b of the cup-shaped housing 1. Moreover, the piezoelectric element 2 can move freely in the axial direction without the leaf spring 3.
The conductor 4 is caulked and fixed between a flange portion 4a at the upper end and a shoulder portion 4b at the center so as to sandwich a convex portion 5a projecting into the upper interior of the insulating spacer 5. Also, the conductor 4 has a screw hole 4 in the axial direction from the top.
c is formed. Reference numeral 6 denotes a terminal for external output connection, which is attached and connected to the conductor 4 with screws 7 and spring washers 8. Screw 7 is conductor 4
is screwed into the screw hole 4c.

Next, to describe the operation of the above-mentioned device, the knocking detector shown in FIG. 1 is attached to the engine body (not shown) by the threaded portion 1a of the housing 1, so engine vibrations when the engine knocks are absorbed by the knocking detector. The vibration is transmitted to the casing 1 and further to the contact surface 1c of the casing 1 with the piezoelectric element 2, causing the piezoelectric element 2 to undergo elastic strain. Therefore, a voltage matching the magnitude of vibration is generated at both ends of the piezoelectric element 2, and this voltage output is taken out via the leaf spring 3 and the conductor 4 from the electrode terminal 6 to an external electrical device.

FIG. 2 shows another embodiment of the present invention, and the only difference is that a conductive weight 10 serving as an inertial mass body is inserted between the piezoelectric element 2 and the leaf spring 3 as shown in FIG. This configuration is different from that of the embodiment shown in FIG. 1 above, and this configuration has the effect of increasing the value of the output voltage of the piezoelectric element 2.

In each of the above embodiments, the leaf spring 3 is used as the spring member, but it goes without saying that a spring washer may be used instead, or a coil spring may be used to achieve the same effect.

As described above, the knocking detector of the present invention includes a housing that is attached to the internal combustion engine body and vibrates together with the internal combustion engine body, one side of which is in contact with the housing, and the other side that is connected to the outside via a spring member. a piezoelectric element connected to a conductor for extracting electrical output;
an insulating member that is attached to the casing and presses and fixes the piezoelectric element against the casing with a predetermined load via the conductor and a spring member, and electrically insulates the conductor from the casing; Because of this structure, the load applied to the piezoelectric element is determined by the spring member, and the stress caused by differences in thermal expansion of each member due to temperature changes and changes in stress applied to the piezoelectric element due to variations in processing accuracy of each member are alleviated by the spring member. A roughly constant initial setting load can be applied to the piezoelectric element, which prevents damage due to excessive stress when assembling the piezoelectric element, and the spring member also serves as one electrode of the piezoelectric element, so a new lead wire can be used. There is no need to make a profit, and it is not only simple and inexpensive, but also has the excellent effect of improving reliability because the lead wire does not break due to vibrations of the internal combustion engine.

Furthermore, in the second invention, since the weight is provided, the value of the output voltage of the piezoelectric element can be increased.
This has the effect of improving the knocking detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the knocking detector of the present invention, and FIG. 2 is a sectional view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Housing, 2... Piezoelectric element, 3... Leaf spring forming a spring member, 4... Electric conductor, 5... Insulating spacer forming an insulating member, 10... Weight. 〓〓〓〓

Claims (1)

[Scope of Claims] 1. A housing that is attached to the internal combustion engine body and vibrates together with the internal combustion engine body, a piezoelectric element whose one surface is in contact with the inner bottom surface of the housing, and an insulator fixed to the opening of the housing. between a member, a conductor that is electrically insulated and fixed to the casing via the insulating member and for extracting electrical output to the outside, and the other surface of the piezoelectric element and the conductor; and a spring member made of a conductive material that presses and fixes the piezoelectric element against the housing with a predetermined load and electrically connects the other surface of the piezoelectric element and the conductor. Knocking detector for internal combustion engines. 2. A heavy-duty device consisting of a housing that is attached to the internal combustion engine body and vibrates together with the internal combustion engine body, a piezoelectric element whose one side is in contact with the inner bottom of the housing, and a conductive material whose one side is in contact with the other side of the piezoelectric element. a weight, an insulating member fixed to the opening of the casing, a conductor fixed to the casing in an electrically insulated manner via the insulating member for extracting electrical output to the outside; It is interposed between the conductor and the other surface of the weight, and presses and fixes the piezoelectric element against the casing with a predetermined load through the weight, and also acts on the piezoelectric element through the weight. A knocking detector for an internal combustion engine, comprising a spring member made of a conductive material that electrically connects the other surface and the conductor.