JP2004093274A - Impact sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impact sensor capable of eliminating the need of a power supply for operation, holding impact record without requiring the power supply, and electrically detecting the record. <P>SOLUTION: An elastic hinge 4 connected between a frame 2 and a mass part 3 is brought in the state of being bent in the longitudinal direction, and the mass part 3 is buckled so as to be deviated upward or downward relative to the position of the frame 2. Also, an electrode 5 is formed on a base 1. When the sensor receives an impact and the mass part 3 is displaced upward, the mass part 3 is held at a new position by the buckling of the hinge 4. The presence or absence of the impact is stored as the position of the mass part 3. The presence or absence of the impact can be detected by detecting a variation in capacitance between the mass part 3 and the electrode 5 due to the positional change of the mass part 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an impact sensor that detects an impact equal to or greater than a predetermined value and stores that the impact is applied.
[0002]
[Prior art]
As this type of conventional shock sensor, there is a liquid shock sensor. In this liquid-type shock sensor, when a shock exceeding a specified level is applied, a chemical change occurs in the built-in liquid, and the chemical change accompanies discoloration of the liquid and maintains the color after the change, The presence or absence of a shock is detected based on the presence or absence of discoloration, and the color of the liquid memorizes the shock.
[0003]
Another conventional shock sensor of this type is a shock sensor provided in a hard disk drive of a computer. This shock sensor is a piezoelectric acceleration sensor that electrically detects the electromotive force generated in the piezoelectric element due to the applied shock. When a shock is detected during use of the device, the movable part of the device that is vulnerable to shock is fixed. Automatically move to.
[0004]
[Problems to be solved by the invention]
The liquid type impact sensor described above records the presence or absence of an impact due to the discoloration of the liquid, but it is difficult to electrically detect the color change. An impact sensor that cannot easily electrically detect the presence or absence of an impact is unsuitable for use in collecting stored records quickly and undoubtedly.
[0005]
On the other hand, a piezoelectric acceleration sensor can easily detect an impact electrically, but requires a power supply for operation. Further, in order to record the presence or absence of the operation, an electronic circuit for separately latching the signal of the sensor is required. However, this latch circuit also loses its memory when the power is turned off.
[0006]
Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide an impact sensor which does not require a power supply during operation, can hold a record of an impact, and can electrically detect the record.
[0007]
[Means for Solving the Problems]
The present invention provides the following means to solve the above-mentioned problems.
[0008]
(1) It has a base, a frame joined to the base, a mass part, and an elastic hinge connected between the frame and the mass part,
The impact sensor according to claim 1, wherein the hinge buckles such that the mass part is unevenly distributed upward or downward with respect to the position of the frame.
[0009]
(2) The impact sensor according to (1), wherein the mass portion, the hinge, and the frame are made of a conductive material, and an electrode is provided on the base.
[0010]
(3) The impact sensor according to (2), wherein the presence or absence of an impact is detected based on a change in capacitance between the mass portion and the base.
[0011]
(4) The mass portion is located above the electrode, and the lower side of the mass portion is in contact with the electrode, and the fact that the mass portion has moved due to an impact loses conduction between the mass portion and the base. The impact sensor according to (2), wherein the presence / absence of an impact is detected.
[0012]
(5) The impact sensor according to (1), wherein a piezo element is provided on the hinge.
[0013]
(6) The impact sensor according to (1), wherein a piezo element is fixed to the hinge, and the presence or absence of an impact is detected by measuring a resistance value of the piezo element.
[0014]
(7) A difference in thermal expansion coefficient between the frame, the mass part, and a member constituting the hinge and the base is large, and the buckling occurs in the hinge based on the difference in thermal expansion coefficient. The impact sensor according to 1).
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a sectional view schematically showing an impact sensor according to the first embodiment of the present invention. The impact sensor of FIG. 1 includes a base 1, a frame 2, a mass 3, a hinge 4, and an electrode 5. In FIG. 1 and other drawings, the base 1 and the electrodes 5 on the base 1 are drawn without hatching. The shock sensor of FIG. 1 employs a structure in which a shock is detected based on a change in capacitance between the mass unit 3 and the electrode 5 and stored.
[0016]
In this impact sensor, the frame 2, the mass 3 and the hinge 4 are symmetrical with respect to a WW line passing through the center of gravity of the mass 3. And the frame 2, the mass part 3, and the hinge 4 have an integral structure. The left side and the right side of the frame 2 in the shape of the impact sensor viewed from the direction of the arrow 103, that is, the plane shape, are respectively rectangular, and the outline of the mass portion 3 as viewed from the direction of the arrow 103 is square. The hinge 4 has a thin plate shape, and the contours of the left side and the right side of the hinge 4 as viewed from the direction of the arrow 103 are each rectangular.
[0017]
The frame 2, the mass 3 and the hinge 4 of the shock sensor of FIG. 1 can be integrally manufactured by selectively performing etching on one silicon substrate by, for example, silicon microfabrication technology. The base 1 can be manufactured, for example, by performing etching on a glass substrate, forming a concave portion corresponding to a gap with the mass portion 3, and providing an electrode 5 at the bottom of the concave portion by sputtering or the like. The base 1 and the frame 2 are fixed by bonding or joining.
[0018]
The hinge 4 is a thin plate having elasticity, and is compressed, bent, and buckled in the directions indicated by arrows 101 and 102 in FIG. Assuming that the hinge 4 is not buckled, the hinge 4 has a flat plate shape, and the center of the hinge 4 and the mass portion 3 in the vertical direction is on the line ZZ in FIG. In the present embodiment, since the hinge 4 is bent and buckled in advance, the center of gravity of the mass portion 3 is displaced below the ZZ line. The frame 2, the mass 3 and the hinge 4 are made of a conductive material in the embodiment of FIG.
[0019]
The principle of operation of the shock sensor of FIG. 1 will be described with reference to FIGS. 2 (A) and 2 (B).
[0020]
As shown in FIG. 2A, when a downward acceleration 104 is input to the impact sensor, an upward inertial force 105 acts on the mass unit 3. At this time, when the acceleration 104 exceeds the force displacing the mass portion 3 due to the buckling of the hinge 4, as shown in FIG. 2B, the mass portion 3 assumes that the hinge 4 is not buckled. (The position of the hinge 4 when the center plane in the thickness direction of the hinge 4 is at the ZZ line in FIG. 1), and moves to another deformed position due to the buckling of the hinge 4. Further, once the mass portion 3 is displaced, the original position [(] is easily obtained unless an acceleration that generates an inertial force exceeding the force displacing the mass portion 3 due to the buckling of the hinge 4 is input in the direction opposite to the acceleration 104. The position does not return to the position shown in FIG. That is, the presence / absence of the application of the impact is held and stored as the position of the mass unit 3.
[0021]
Since the distance between the mass 3 and the electrode 5 changes from D1 to D2 by the operation of the impact sensor, the capacitance between the mass 3 and the electrode 5 decreases. By detecting this change in capacitance, the presence or absence of an impact can be detected.
[0022]
The impact force at which the impact sensor operates is mainly determined by the following items.
(1) Mass of mass 3 (2) Thickness, width, length and Young's modulus of hinge 4 (3) Magnitude of compressive force acting on hinge 4 In assembling the impact sensor according to the present invention described above, the hinge 4 FIGS. 3A and 3B show an example of a method for obtaining a compressive force required to cause buckling.
[0023]
As shown in FIG. 3A, a part of an integral structure including a mass part 3, a hinge 4 symmetrically disposed with respect to the mass part 3 and elastically supporting the mass part 3, and a frame 2 is formed by a length L of the base 1. Is also lengthened by 2 L. As shown in FIG. 3B, the base 1 is fixed by the jig 1 and the jig 2 so as to have the length L, and the base 1 and the frame 2 are fixed by bonding or joining. At this time, the left and right hinges 4 are always compressed in the longitudinal direction by ΔL.
[0024]
In addition, a material having a large difference in thermal expansion coefficient is used for the base 1 and the component having an integral structure including the mass portion 3, the hinge 4 that is symmetrically disposed with respect to the mass portion 3 and elastically supports the mass portion 3, and the frame 2. When these are bonded or joined at a high temperature, thermal stress occurs at room temperature. A method of using this thermal stress as a compressive force required to cause buckling of the hinge 4 is also given as an example. For example, an integrated structure that forms the frame 2, the mass 3, and the hinge 4 is made of silicon, and the base 1 is made of glass whose coefficient of thermal expansion is much larger than that of silicon. Then, the two are joined in a high-temperature environment, and if the integrated structure and the base 1 are returned to a normal temperature environment in a posture where the integrated structure is located above the base 1 as shown in FIG. While receiving the force, the base 1 contracts more than the integrated structure, so that the hinge 4 receives the compressive forces 101 and 102 in FIG. 1 and the hinge 4 is displaced below the ZZ line as shown in FIG. It buckles and the impact sensor of FIG. 1 can be manufactured.
[0025]
FIG. 4 is a diagram showing a second embodiment of the present invention. The shock sensor of FIG. 4 has the same components as the shock sensor of FIG. 1, but the mass part 3 and the electrode 5 are separated in FIG. The part 3 and the electrode 5 are in contact. Due to this difference in configuration, FIG. 1 shows a structure in which the impact is detected by changing the capacitance between the mass portion 3 and the electrode 5 due to the impact as described above, whereas FIG. When the impact sensor is actuated by an impact, the mass 3 made of a conductive material separates from the electrode 5, so that the impact is detected by the presence or absence of conduction between the mass 3 and the electrode 5.
[0026]
FIG. 5 is a diagram showing a third embodiment of the present invention. The impact sensor of FIG. 5 includes a base 1, a frame 2, a mass 3, a hinge 4, and a piezo element 6. In this embodiment, the piezo element 6 is fixed to the hinge 4. When the buckling state of the hinge 4 is reversed due to an impact of a certain value or more, the stress acting on the piezo element 6 changes from tension to compression. Since the resistance of the piezo element 6 changes due to stress, the impact is stored as a change in the resistance, and the presence or absence of the impact can be detected by measuring the resistance of the piezo element 6.
[0027]
【The invention's effect】
As described in detail above, according to the present invention, the mass part that has been previously displaced due to the buckling of the hinge is forcibly displaced to the opposite side by an impact force equal to or greater than a predetermined value, and the displaced mass part Is not easily returned to the original position unless a shock of a predetermined value or more is applied in the direction opposite to the input, so the displacement of this mass part can be stored as the presence or absence of the impact force, and the stored displacement of the mass part is saved And detected electrically. In this way, the displacement of the mass is stored and saved without the need for a power supply. Electrically detecting the displacement of the mass portion can be easily detected by providing an electrode on the base or forming a piezo element on the hinge. As described above, according to the present invention, it is possible to provide an impact sensor which does not require a power supply during operation, can hold a record of an impact without requiring a power supply, and can electrically detect the record.
[Brief description of the drawings]
FIG. 1 is a sectional view schematically showing an impact sensor according to a first embodiment of the present invention.
2A and 2B are diagrams for explaining the operation principle of the shock sensor of FIG. 1, wherein FIG. 2A is a diagram showing a state before receiving a shock, and FIG. 2B is a diagram showing a state after receiving a shock; It is.
3A and 3B are diagrams showing an example of a method of obtaining a compressive force for causing buckling of a hinge in assembling the impact sensor of the present invention, wherein FIG. 3A is a diagram showing a state before assembly, and FIG. () Is a diagram showing a state in which buckling occurs in the hinge using a jig.
FIG. 4 is a cross-sectional view schematically illustrating an impact sensor according to a second embodiment of the present invention.
FIG. 5 is a sectional view schematically showing an impact sensor according to a third embodiment of the present invention.
[Explanation of symbols]
1: Base 2: Frame 3: Mass part 4: Hinge 5: Electrode 6: Piezo element 101, 102: Compressive force 103: Direction of viewing the plane shape of the impact sensor 104: Acceleration 105: Inertial force

Claims (7)

A base, a frame joined to the base, a mass portion, and an elastic hinge connected between the frame and the mass portion;
The impact sensor according to claim 1, wherein the hinge buckles such that the mass part is unevenly distributed upward or downward with respect to the position of the frame. The impact sensor according to claim 1, wherein the mass part, the hinge, and the frame are made of a conductive material, and an electrode is provided on the base. The impact sensor according to claim 2, wherein the presence or absence of an impact is detected based on a change in capacitance between the mass part and the base. The mass section is located above the electrode, and the lower side of the mass section is in contact with the electrode, and the movement of the mass section due to the impact is caused by the loss of conduction between the mass section and the base. The impact sensor according to claim 2, wherein the presence or absence of presence is detected. The impact sensor according to claim 1, wherein a piezo element is provided on the hinge. The impact sensor according to claim 1, wherein a piezo element is fixed to the hinge, and the presence or absence of an impact is detected by measuring a resistance value of the piezo element. 2. The difference in thermal expansion coefficient between the frame, the mass portion, and a member constituting the hinge and the base, and the buckling occurs in the hinge based on the difference in thermal expansion coefficient. 3. Impact sensor.

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