JPH0843190A - Impact sensor - Google Patents

Abstract

PURPOSE:To detect a very weak signal with a sufficient S/N and excellent sensitivity by adhering a piezoelectric element to a member having a specific mechanical resonance system, and bonding it to a material to be vibrated. CONSTITUTION:A piezoelectric element 6 is adhered to a member 2 having a specific mechanical resonance system to constitute an impact sensor 1. The element 6 is composed of an electrode part 7 having an upper partial electrode 7a and a lower partial electrode 7b, and a pedestal 8 provided under an electrodeless part 9. The pedestal 8 is adhered to a piezoelectric element bonding part 4, and bonded to the member 2. The vibration from the element 6 is propagated from the part 4 to the element 6 via the pedestal 8, and the element 6 is vibrated only at the part 7. Since the part 7 is floated via the pedestal 8, it can be independently vibrated, and not affected by the influence of damping due to bonding and the shift of a resonance point. Accordingly, the element 6 becomes one having a resonance frequency as designed and the vibration can be detected with high sensitivity by making it coincide with the resonance frequency of the member 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact sensor that detects an impact using a piezoelectric body. In particular, the present invention relates to an impact sensor using a piezoelectric body, which has excellent sensitivity by attaching a piezoelectric body to a member having a mechanical resonance system.

[0002]

2. Description of the Related Art In a shock sensor using a piezoelectric material,
There are a resonance type having a sharp peak sensitivity at a specific frequency and a wide band type having a wide and flat sensitivity characteristic. In order to detect weak signals with high sensitivity, a resonance type that uses the resonance point of the piezoelectric body is used.Since the resonance point is determined by the shape and size of the piezoelectric body, the frequency of the detection signal and the resonance of the piezoelectric body High-sensitivity detection is performed by matching the points.

[0003]

However, since the resonance phenomenon of the piezoelectric body undergoes damping or shift of the resonance point due to adhesion with the vibrating body, a sufficient S / N ratio (signal There is a problem that the noise-to-noise ratio cannot be obtained and effective detection is difficult, and there is a strong demand for a shock sensor using a piezoelectric body that does not cause damping or resonance point shift during bonding.

The present invention has been made in view of the above conventional circumstances, and an object thereof is to provide an impact sensor capable of detecting a weak signal with a sufficient S / N ratio with high sensitivity.

[0005]

The impact sensor of the present invention comprises:
In order to achieve the above object, a piezoelectric body is attached to a member having a specific mechanical resonance system, and the piezoelectric body is adhered to a vibrated body.

[0006]

If the piezoelectric body is directly adhered to the vibrating body, damping and shift of the resonance point occur, the resonance frequency of the vibrating body and the resonance frequency of the piezoelectric body cannot match, and sufficient S / Although the N ratio cannot be obtained, the resonance frequency of the vibrated body and the resonance frequency of the member having the mechanical resonance system having a structure that is not affected by the adhesion are matched, and the piezoelectric body is adhered to the member to detect with high sensitivity. can do. Further, by providing a partial electrode on the piezoelectric body to be adhered to the member and providing a pedestal on the electrodeless portion for adhesion, it becomes possible to match the three resonance frequencies of the vibrating body, the mechanical resonance system and the piezoelectric body. It can be detected with high sensitivity.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an impact sensor of the present invention. Impact sensor 1
Is mainly composed of a member 2 having a specific mechanical resonance system and a piezoelectric body 6 attached to the member 2. The member 2 having a mechanical resonance system is a material that causes mechanical vibration, and for example, an elinvar with a large mechanical quality factor Q is preferably used. The resonance frequency of the member 2 is determined by the material and shape of the member, and is designed according to the resonance frequency of the vibrating body. For example, the resonance frequency of the vibrating body is measured in advance so that the resonance frequencies match. The member 2 is defined. The member 2 shown in FIG. 1 is an example in which the vibrating body bonding portion 3 and the piezoelectric body bonding portion 4 are constituted by a doubly supported beam connected by a hinge portion 5. Either one of the above may be omitted, and a cantilever may be used.

By virtue of the fact that the vibrating body (not shown) is adhered only by the adhering section 3, the vibration received from the vibrating section is propagated from the adhering section 3 to the piezoelectric adhering section 4 via the hinge section 5. . Since the output voltage of the piezoelectric body is proportional to the magnitude of the vibration amplitude, increasing the vibration amplitude of the piezoelectric body bonding portion 4 increases the sensitivity. Therefore, in the shock sensor shown in FIG. 1, the piezoelectric bonding portion 4 can independently vibrate without being affected by the bonding, and thus the detection can be performed with high sensitivity.

FIG. 2 shows the piezoelectric body 6 provided in the central portion of the piezoelectric body bonding portion 4. The piezoelectric body 6 is composed of an electrode portion 7 including an upper partial electrode 7a and a lower partial electrode 7b, and a pedestal 8 provided below the electrodeless portion 9, and the piezoelectric body 6 is attached to a member 2 having a mechanical resonance system. This is performed by adhering the pedestal 8 on the piezoelectric bonding portion 4. The vibration from the vibrating body propagates from the piezoelectric body bonding portion 4 to the piezoelectric body 6 via the pedestal 8, and the piezoelectric body 6 vibrates only in the portion where the electrode portion 7 is provided. This is because only the portion where the electrode portion 7 is provided is subjected to the polarization treatment and only that portion has a function as a piezoelectric body. In addition, since the electrode portion 7 floats in the pedestal 8 and can vibrate independently, there is no influence such as damping due to adhesion. Therefore, it is possible to manufacture the piezoelectric body 6 having a resonance frequency according to the design, and by matching the resonance frequency of the member 2, it is possible to perform detection with higher sensitivity.

Next, an application example in which the impact sensor 1 is used for detecting a collision between a disk and a head in a magnetic disk device will be described. FIG. 3 is a schematic view of a collision detection mechanism for a disk and a head using the impact sensor 1 of the present invention. The core slider 11 floats on the disk 10 rotating at a high speed at submicron intervals for recording and reproduction. When contact occurs on the medium surface of the disk 10 due to mixing of protrusions or dust, the disk 10 and the core slider 11 are contacted with each other. No. 11 crashes, recording / reproducing becomes impossible, and a fatal failure occurs.

Conventionally, as a sensor for detecting the collision between the disk and the head, since the detection signal has a weak amplitude and a high frequency component, the core slider 11 is equipped with the AE sensor 14 as shown by the dotted line, and Detection was performed near the source. However, due to the higher density of the disk 10, the shape of the core slider 11 becomes smaller, and it becomes difficult to mount the AE sensor 14 on the core slider 11. Therefore, there is a demand for a sensor that can detect with high sensitivity even in the vicinity of the signal generation source.

The impact sensor 1 of the present invention comprises a core slider 1
By bonding the vibrating body bonding portion 3 of the shock sensor 1 onto the gimbal 12 that connects the arm 1 and the arm 13, it is possible to detect a highly sensitive collision between the disk and the head, and the material and shape of the core slider 11. By making the peak level frequency of the unique spectrum pattern determined by the dimensions and the resonance frequency of the member 2 and the piezoelectric body 6 of the impact sensor 1 all coincide with each other, detection with higher sensitivity can be performed.

[0013]

As can be understood from the above description, according to the present invention, it is possible to detect with a sufficient S / N ratio and with high sensitivity without being affected by damping due to adhesion or shift of resonance frequency. It is possible to provide an impact sensor. Further, it is extremely effective when applied as a sensor for detecting a collision between a disk and a head for detecting a weak signal.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a structure of an impact sensor of the present invention.

FIG. 2 is a diagram illustrating a structure of a piezoelectric body of the present invention.

FIG. 3 is a schematic diagram of a collision detection mechanism between a disk and a head, for explaining an application example of the impact sensor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impact sensor 2 Member having a mechanical resonance system 3 Vibrating body adhesive portion 4 Piezoelectric body adhesive portion 5 Hinge portion 6 Piezoelectric body 7 Electrode portion 8 Pedestal 9 Piezoelectric electrodeless portion 10 Disk 11 Core slider 12 Gimbal 13 Arm 14 AE Sensor

Claims (8)

[Claims] 1. A shock sensor comprising a member having a specific mechanical resonance system and a piezoelectric body attached to the member. 2. The shock sensor according to claim 1, wherein the member having a specific mechanical resonance system includes a piezoelectric body bonding portion and a vibrating body bonding portion which are connected via a hinge portion. 3. The shock sensor according to claim 2, wherein the vibrating body bonding portion of the member having the specific mechanical resonance system is bonded to the vibrating body. 4. The impact sensor according to claim 3, wherein the member having the specific mechanical resonance system matches the resonance frequency of the vibrated body. 5. The piezoelectric body comprises an electrode portion provided with a partial electrode and a pedestal provided on the electrodeless portion, and the piezoelectric body is attached by adhering the pedestal and a member having the specific mechanical resonance system. The shock sensor according to any one of claims 1 to 4, wherein the shock sensor is a shock sensor. 6. The shock sensor according to claim 5, wherein the pedestal and the piezoelectric bonding portion of the member having the specific mechanical resonance system are bonded together. 7. The shock sensor according to claim 3, wherein the piezoelectric body has a resonance frequency of a vibrated body. 8. The vibrating body is a head slider that floats above a magnetic disk medium.
7. The impact sensor according to any one of 7.