JP3106970B2 - Acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor used for detecting a shock in a hard disk drive (HDD) device, and more particularly, to a structure of a bimorph-type detecting element used in forming an acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, as an acceleration sensor, FIG.
In general, the device includes a bimorph-type detection element (hereinafter, referred to as a detection element) 11 configured as shown in FIG. A pair of piezoelectric ceramic plates 1 each having a signal extraction electrode 12 and an intermediate electrode 13 formed thereon
The piezoelectric ceramic plates 14 are joined face-to-face with the intermediate electrodes 13 interposed therebetween. Here, each of the piezoelectric ceramic plates 14 is polarized in advance in a direction (indicated by arrows X and Y in the figure) opposite to the other side while being along the respective plate thickness directions.

The signal extraction electrode 12 of the detection element 11
A pair of holding parts 15 each having a “U” shape in a side view are arranged on both sides facing each other so as to sandwich the detection element 11. Depending on these ceramic holding parts 15, detection is performed. Both ends along the longitudinal direction of the element 11 are fixedly supported. That is, the detection element 11 here has a support structure called a double-supported type by being held by the holding component 15.

Further, at this time, each of the signal extraction electrodes 12 formed on the main surface of the detection element 11 is provided with a pair of holding parts 15 and a pair of case parts (not shown) attached on their opening side surfaces. ) These are connected to external extraction electrodes 16 and 17 formed for each different end face. Therefore, in such an acceleration sensor according to the related art, the detection element 11 housed in the holding component 15 is used.
Are deformed by the action of the inertial force when the acceleration G is applied, and electric charges are generated at the signal extraction electrodes 12 as the detection element 11 is deformed. Is generated by the external extraction electrode 1
As a result, the application state of the acceleration G is detected.

[0005]

However, in recent years, since the acceleration sensor has been required to be further reduced in size, it has been necessary to reduce the size of the detection element 11 itself. However, if the detection element 11 having the double-supported support structure is reduced in size,
The deformation of the detection element 11 at the time of application of acceleration becomes very small, and the amount of electric charge generated due to the deformation of the detection element 11 becomes too small. As a result, there is a problem that the detection sensitivity of the acceleration sensor is greatly reduced. Would.

The present invention has been made in view of such inconvenience, and it is an object of the present invention to provide an acceleration sensor configured to realize both miniaturization and detection sensitivity.

[0007]

SUMMARY OF THE INVENTION An acceleration sensor according to the present invention comprises a pair of piezoelectric ceramic plates on each of which a signal extraction electrode and an intermediate electrode are formed on a main surface thereof. a bimorph type detection element comprising facing bonding a piezoelectric ceramic plates are provided with a pair of holding parts that are arranged to sandwich from both sides the direction opposite to the bimorph type detection element a signal extraction electrode, of these holding parts all SANYO fixed supporting only one end portion along the longitudinal direction of the bimorph type detection element, the longitudinal direction of the other holding part
A ceramic member is sandwiched between the ends . The ceramic member is a piezoelectric
It is preferably a lamic plate.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view showing a detecting element of the acceleration sensor according to the present embodiment, and FIG. 2 is an exploded perspective view showing a manufacturing procedure of the detecting element according to the present embodiment.

The acceleration sensor according to the present embodiment is provided with a detecting element 1 as shown in FIG.
At this time, the detecting element 1 includes a pair of piezoelectric ceramic plates 4 on each of which a signal extraction electrode 2 and an intermediate electrode 3 are formed on the main surface. And then face-to-face joined. In addition, each of these piezoelectric ceramic plates 4 is in the direction opposite to the other side while being along the respective plate thickness directions (indicated by arrows X and Y in the drawing), as in the conventional embodiment.
Is polarized along.

A pair of holding parts 5 each having a U-shape in a side view are disposed on both sides of the detection element 1 facing the signal extraction electrodes 2 with the detection element 1 interposed therebetween. Only one end of the detection element 1 along the longitudinal direction is fixed and supported by these ceramic holding parts 5. That is, in this case, the detecting element 1 has a pair of piezoelectric ceramic plates 4 having a shorter length in the longitudinal direction than the detecting element 11 according to the conventional embodiment.
And a pair of holding parts 5 arranged opposite to each other.
Thus, only one end along the longitudinal direction is fixed and supported, so that it has a support structure called a cantilever type. In the present embodiment, it is sufficient that only one end along the longitudinal direction of the detection element 1 is fixedly supported at one end along the longitudinal direction of each holding component 5, as shown in FIG. In addition, it goes without saying that a ceramic member 6 equivalent to the piezoelectric ceramic plate 4 constituting the detecting element 1 may be interposed between the other end portions of the holding component 5 for convenience in production.

Further, at this time, each of the signal extraction electrodes 2 formed on the main surface of the detection element 1 has a pair of holding parts 5 and a pair of case parts (shown in FIG. ) Is connected to a pair of external extraction electrodes 7 and 8 formed apart from each other on the same end face as in FIG. Therefore, in the acceleration sensor according to the present embodiment, the other end of the detection element 1 housed in the holding component 5 is deformed by the action of the inertial force when the acceleration G is applied. As a result, electric charges are generated at each signal extraction electrode 2, and the generation of electric charges at these signal extraction electrodes 2 is detected through the external extraction electrodes 7 and 8, so that the application state of the acceleration G is detected. Become. Then, such a cantilevered detection element 1 is deformed more than the conventional cantilevered detection element 11, and a charge having a size corresponding to the large deformation amount is generated in the signal extraction electrode 2. Therefore, the acceleration sensor including the cantilevered detection element 1 can be downsized while maintaining or improving the detection sensitivity.

By the way, when manufacturing the double-supported detection element 11 according to the conventional form, as shown in FIG. 2, an electrode pattern (not shown) serving as the signal extraction electrode 12 and the intermediate electrode 13 is provided. A ceramic motherboard 21 for the piezoelectric ceramic plate 14 formed on each of the main surfaces and a motherboard 23 for a sandwiching component in which a concave groove 22 having a predetermined width is formed at each predetermined position on the inner surface side are prepared. , A sandwiching component master board 23 from the outside of each of the ceramic master boards 21 that face each other with the electrode pattern serving as the intermediate electrode 13 interposed therebetween.
Are applied and joined together, and then they are cut along a predetermined cutting line S. Therefore, when manufacturing the cantilevered detection element 1 according to the present embodiment, the same manufacturing procedure as that of the double-sided detection element is followed. In this case, the size of the piezoelectric ceramic plate 4 is changed to the size of the piezoelectric ceramic. The formation of the through-groove 24 having a predetermined width so as to be shorter than the plate 14 is formed at each predetermined position of the ceramic parent substrate 21 in advance.

[0014]

As described above, according to the acceleration sensor according to the present invention, since the detection element has a cantilever type support structure, a larger deformation than the detection element having a double-sided support structure is obtained. As a result, the amount of charge generated due to the deformation of the detection element increases. Therefore, even when the detection element and the acceleration sensor are miniaturized, the detection sensitivity of the acceleration sensor does not decrease, and an effect that both miniaturization and detection sensitivity can be realized is obtained.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing a detection element of an acceleration sensor according to the present embodiment.

FIG. 2 is an exploded perspective view showing a procedure for manufacturing a detection element according to the present embodiment and a conventional embodiment.

FIG. 3 is an external perspective view showing a detection element of an acceleration sensor according to a conventional embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Detection element (bimorph type detection element) 2 Signal extraction electrode 3 Intermediate electrode 4 Piezoelectric ceramic plate 5 Holding component 6 Ceramic member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-148970 (JP, A) JP-A-3-92764 (JP, A) JP-A-4-111177 (JP, U) JP-A-4-19771 1455 (JP, U) WO 91/13364 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01P 15/09 H01L 41/08

Claims (2)

(57) [Claims] 1. A pair of piezoelectric ceramic plates (4) each having a signal extraction electrode (2) and an intermediate electrode (3) formed on each of the main surfaces. A bimorph-type detection element (1) in which piezoelectric ceramic plates (4) are joined face-to-face, and a pair of bimorph-type detection elements (1) sandwiched from both sides facing the signal extraction electrode (2). and a holding part (5), these holding parts (5) are all SANYO that only one end portion along the longitudinal direction and fixed support of the bimorph type detection device (1), holding part (5) The other end of the
An acceleration sensor , wherein a mic member is sandwiched . 2. The acceleration sensor according to claim 1, wherein said ceramic member is a piezoelectric ceramic plate.