JPH0618321A - Vibration detector - Google Patents

Abstract

PURPOSE:To obtain a vibration detector which can secure the contact position between a vibrating plate and a housing highly accurately irrespective of the fabricating accuracy and detect the vibration with high accuracy. CONSTITUTION:A housing 1 has a screw part 1a at one end, a caulking part 1b at the other end and a mounting part 1c thereinside. A projecting part 7 is formed at the uniform height in the whole of the innermost peripheral edge of the mounting part 1c. The periphery of a disc-shaped vibrating plate 2 is fixed to the projecting part 7 via a washer 3 and a cover 5 by caulking of the caulking part 1b. When the vibrating plate 2 is set in housing 1, the contact position of the innermost periphery of the vibrating part 2 is regulated by the projecting part 7. A piezoelectric element 4 for converting the vibration of the vibrating plate 2 to an electric amount is securely bonded onto the vibrating plate 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration detector for detecting knocking of an object to be vibrated, for example, an engine.

[0002]

2. Description of the Related Art FIG. 4 is a cross-sectional view showing an example of a conventional vibration detector. In FIG. 4, reference numeral 1 denotes a housing having a screw portion 1a at one end, a crimp portion 1b at the other end, and a mounting portion 1c inside. 2 is a disc-shaped diaphragm disposed around the mounting portion 1c of the housing 1 via the washer 3 and the cover 5 by caulking of the caulking portion 1b, and 4 is adhesively fixed on the diaphragm 2. The piezoelectric element 4 is a piezoelectric element as a vibration-electric quantity conversion element that converts the vibration of the diaphragm 2 into an electric quantity.
For example, PZT or the like can be used. Reference numeral 6 is a terminal for taking out the output signal of the piezoelectric element 4 to the outside.

Next, the operation of the conventional vibration detector will be described. The vibration detector thus configured is attached and fixed to the object to be detected by vibration, for example, the engine by the screw portion 1a. Then, the vibration generated in the engine is transmitted to the housing 1 and the diaphragm 2 vibrates. At this time,
Since the periphery of the diaphragm 2 is fixed, it vibrates in a resonance mode according to the diameter of the free vibration end. That is, with respect to the vibration of the housing 1, the vibration of the diaphragm 2 vibrates only in response to the vibration of the specific frequency f ₀ , and the output from the piezoelectric element 4 via the terminal 6 as shown by the waveform A in FIG. Is obtained.

Therefore, the knocking of the engine can be detected by adjusting the inner diameter of the mounting portion 1c so that the vibration of the diaphragm 2 becomes a resonance mode at the knocking frequency of the engine.

[0005]

As described above, in the conventional vibration detector, since the periphery of the diaphragm 2 is planarly fixed to the mounting portion 1c, the seating surface of the mounting portion 1c may be damaged due to poor machining accuracy or the like. When the surface is rough, as shown in FIG. 5, the innermost peripheral contact position between the mounting portion 1c and the diaphragm 2 is displaced, and the diameter of the free vibration end of the diaphragm 2 is changed. Therefore, the resonance frequency of the diaphragm 2 shifts from f ₀ to f _b ,
As shown in FIG. 6, there is a problem in that the output waveform shifts from the waveform A to the waveform B, and the vibration detection accuracy decreases.

The present invention has been made in order to solve the above problems, and can ensure the contact position between the diaphragm and the housing with high accuracy and detect vibration with high accuracy regardless of the processing accuracy. The purpose is to obtain a vibration detector.

[0007]

A vibration detector according to the present invention is provided with a contact point for defining an innermost peripheral contact position of a diaphragm on a mounting portion.

[0008]

According to the present invention, the contact point provided on the mounting portion defines the innermost peripheral contact position of the diaphragm when fixing the periphery of the diaphragm to the mounting portion, and It is possible to suppress the fluctuation of the diameter and the fluctuation of the resonance frequency of the diaphragm.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. 1 is a sectional view of a vibration detector according to a first embodiment of the present invention. In the figure, the same or corresponding parts as those of the conventional vibration detector shown in FIG. . In the figure, 7 is a protrusion as a contact point formed at a uniform height over the entire circumference of the innermost peripheral end of the mounting portion 1c.

In the first embodiment, the vibrating plate 2 is arranged around the projection 7 of the mounting portion 1c of the housing 1 via the washer 3 and the cover 5 by the crimping of the crimping portion 1b. . Therefore, even if the machining accuracy is poor and the seating surface of the mounting portion 1c is rough, the innermost peripheral contact position of the diaphragm 2 is defined by the protrusion 7, and the fluctuation of the diameter of the free vibration end can be suppressed. Further, even if the upper surface of the protruding portion 7 is rough, the width of the protruding portion 7 is narrow, so that the fluctuation of the innermost peripheral contact position of the diaphragm 2, that is, the fluctuation of the diameter of the free vibration end can be extremely reduced.

Therefore, regardless of the processing accuracy, the contact position between the diaphragm 2 and the housing 1 is ensured with high accuracy, and the resonance frequency of the diaphragm 2 can be matched with the frequency of the detected vibration with high accuracy. Can be detected with high accuracy.

The operation of the first embodiment operates in the same manner as the conventional vibration detector.

As described above, according to the first embodiment, since the protrusion 7 is formed over the entire circumference of the innermost peripheral end of the mounting portion 1c of the housing 1, the protrusion 7 is the innermost portion of the diaphragm 2. There is an effect that the circumferential contact position is defined, the contact position between the diaphragm 2 and the housing 1 can be secured with high accuracy, and the vibration can be detected with high accuracy regardless of the processing accuracy.

Example 2. In the first embodiment described above, the projection 7 is formed over the entire circumference of the innermost peripheral end of the mounting portion 1c of the housing 1, but in the second embodiment, the seat surface other than the innermost peripheral end of the mounting portion 1c is formed. Protrusion 7 over the entire circumference
Are formed to achieve the same effect.

Example 3. Second Embodiment FIG. 2 is a sectional view of a vibration detector showing a third embodiment of the present invention, in which 8 is a mounting portion 1.
The seating surface of c is processed into a taper shape over the entire circumference, and the mounting portion 1
It is an edge portion as a contact point formed at the innermost peripheral edge of c.

In the third embodiment, the vibrating plate 2 is arranged around the edge portion 8 of the mounting portion 1c of the housing 1 via the washer 3 and the cover 5 by the crimping of the crimping portion 1b. .

Therefore, according to the third embodiment, even if the machining accuracy is poor and the seating surface of the mounting portion 1c is rough, the innermost peripheral contact position of the diaphragm 2 is defined by the edge portion 8 and the free vibrating end. The fluctuation of the diameter can be suppressed, and the same effect as that of the first embodiment can be obtained.

Example 4. In the first embodiment, the mounting portion 1c
Although the circumference of the disk-shaped diaphragm 2 is fixed over the entire circumference by the projections 7 formed on the circumference, in the fourth embodiment, as shown in FIG. 3, the circumference of the disk-shaped diaphragm 2 is fixed. The cutout portions 2a are formed at equal intervals, and the periphery of the diaphragm 2 is partially fixed on the circumference by the protrusions 7, and the same effect is obtained.

[0019]

As described above, according to the present invention, since the contact point that defines the innermost peripheral contact position of the vibration plate is provided in the mounting portion, the contact point provided in the mounting portion can improve the processing accuracy. Regardless, when fixing the periphery of the diaphragm to the mounting part, the innermost peripheral contact position of the diaphragm is regulated, the fluctuation of the diameter of the free vibration end of the diaphragm is suppressed, and the fluctuation of the resonance frequency of the diaphragm is suppressed. Thus, there is an effect that a vibration detector capable of detecting vibration with high accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a vibration detector showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a vibration detector showing a third embodiment of the present invention.

FIG. 3 is a plan view of a vibration plate of a vibration detector according to a fourth embodiment of the present invention.

FIG. 4 is a sectional view showing an example of a conventional vibration detector.

FIG. 5 is an enlarged sectional view of an essential part showing an example of a conventional vibration detector.

FIG. 6 is a graph showing an example of an output signal from a conventional vibration detector.

[Explanation of symbols]

 1 Housing 1c Mounting part 2 Vibration plate 4 Piezoelectric element (vibration-electric quantity conversion element) 7 Projection part (contact point) 8 Edge part (contact point)

Claims (1)

[Claims] 1. A housing to be attached to an object to be vibrated, a vibrating plate having a periphery fixed to a mounting portion provided on the housing, and a vibration-electricity converting vibration of the vibrating plate into an electric quantity. A vibration detector including a quantity conversion element, wherein a contact point that defines an innermost peripheral contact position of the diaphragm is provided on the mounting portion.