TW200422621A - Shock sensor - Google Patents

Abstract

The present invention provides a shock sensor with high reliability that can surely sense a shock within a very short time period. The shock sensor (10) comprises a magnetostrictive element (12) whose magnetic permeability changes according to the acceleration of a shock, a bias electric field applying means (14) for applying a bias electric field to the magnetostrictive element (12), and an electric field measuring means (16) for measuring the intensity of the electric field in the vicinity of the magnetostrictive element (12).

Description

200422621 (1) Description of the invention [Technical field to which the invention belongs] The present invention relates to, for example, vibration sensors for computers and related equipment, AV (audiovisual) equipment, home appliances, transportation equipment, industrial equipment, etc. 0 [ Prior art

In the past, vibration sensors have been used in various fields for various purposes. For example, in a notebook computer, a digital camera, etc., there are examples of using a vibration sensor to detect vibrations such as dropping, stopping driving of internal components, writing data, and the like to protect recorded data and built-in components. In addition, automobiles use vibration sensors for airbags and the like. For such a vibration sensor, piezoelectric ceramics using pzt (lead titanate silicate) or the like (for example, refer to Japanese Patent Publication Nos. 2000-1-5 1 6 8 8 4) are well known.

Piezoelectric ceramics are deformed in response to the acceleration of vibration ', and corresponding to the magnitude of the deformation, charge polarization occurs. Vibration can be detected by measuring this polarized charge or voltage. However, since the time required for polarization of the piezoelectric ceramics is limited, high-speed response is limited, and vibrations within a small time cannot be detected. For example, although the so-called 1 μ s (microsecond) vibration detection is required for detecting accelerations of about 2000G (1G = lO ^ Nn ^ Kg · 2), vibration sensing using conventional piezoelectric ceramics is required. The device cannot reliably detect such vibration within a small time. -4- (2) 200422621 Because of the high impedance of piezoelectric ceramics, it is relatively sensitive to interference ’, so it is easy to get noise accidentally. Furthermore, the hysteresis of piezoelectric ceramics is large. Therefore, the vibration sensor using piezoelectric ceramics has a problem that the S / N ratio (ratio of signal to noise) is small.

In addition, a pair of electrodes for detecting polarization are mounted on both sides of the piezoelectric ceramic in the direction of self-vibration, and the lead portions are connected to the electrodes, respectively. Although external force acts on the piezoelectric ceramics due to installation work and vibration, the two lead portions are respectively bent with the piezoelectric ceramics. However, since these lead portions are arranged apart from each other in the direction of the vibration action, it appears as a whole. Because the rigidity is very high, it is not easy to bend, so excessive load may be applied to the lead portion, and the joint portion between the lead portion and the electrode may be damaged. [Summary of the Invention]

The present invention is a technique invented in view of the above problems, and an object thereof is to provide a highly reliable vibration sensor that can reliably detect vibration within a small time. The inventors of the present invention have solved the above problems by using a magnetostrictive element that responds more rapidly to vibration acceleration than a piezoelectric element and has a small impedance, that is, the present invention seeks to solve the above problems. (1) A vibration sensor, comprising: a magnetostrictive element that responds to vibration acceleration and changes in magnetic permeability; a bias magnetic field applying means for applying a bias magnetic field to the magnetostrictive element; and a method for measuring magnetostriction Magnetic field measurement method for the magnetic field strength near the telescopic element. (3) 200422621 (2) The vibration sensor according to item (1), characterized in that the aforementioned magnetostrictive element is a giant magnetostrictive element composed of lanthanide group elements and iron group elements. (3) The vibration sensor according to item (1) or (2), characterized in that the aforementioned means for applying a bias magnetic field is a permanent magnet.

(4) The vibration sensor according to any one of items (1) to (3), characterized in that the magnetic field measuring means is provided with a plurality of means for measuring accelerations in a plurality of directions of vibration. (5) The vibration sensor according to any one of items (1) to (4), wherein the magnetic field measuring means includes a coil disposed near the magnetoresistive element. (6) The vibration sensor according to any one of items (1) to (4), wherein the magnetic field measurement means has a structure including a magnetoresistive element. (7) The vibration sensor according to any one of items (1) to (4), wherein the magnetic field measurement means has a structure including a Hall element.

[Embodiment] The following describes the embodiment of the present invention in detail with reference to the drawings. Fig. 1 is a perspective view illustrating the structure of the vibration sensor 10 of this embodiment. The vibration sensor 10 is provided with a magnetostrictive element 1 that responds to vibration acceleration and changes in permeability. 2. A bias magnetic field application means 14 for applying a bias magnetic field to the magnetostrictive element 1 2 and a magnetostrictive measurement method. Coil (magnetic field measuring means) 16 for the magnetic field strength near the element 1 2. -6-(4) 200422621 The magnetostrictive element 12 is a giant magnetostrictive element composed of a lanthanoid group element and an iron group element, and is formed into a substantially rectangular body. Herein, the so-called "iron group element" in this specification is used in the collective term of the elements of group 8 in the fourth cycle of the periodic table, that is, F e (iron), Ni (nickel), and C 0 (cobalt). The variation of the permeability of this type of giant magnetostrictive element with respect to deformation has reached 40% or more.

Specifically, the 3′-biasing field application means 14 is a ferrite magnet (permanent magnet) having a substantially rectangular plate-like body, and is connected to the bottom surface of the magnetostrictive element 12. The bias magnetic field applying means 14 is supported on the substrate 24 by the side opposite to the bonding surface of the magnetostrictive element 12. Specifically, the coil 16 is a member formed continuously and equidistantly along a common plane of a plurality of loops, and is arranged adjacent to and opposite to the magnetostrictive element 12 along the longitudinal direction of the magnetostrictive element 12. A voltmeter 18 (not shown) is connected to both ends of the coil 16 via an amplifier circuit 17 (the details are omitted).

Next, the function of the vibration sensor 10 will be described. A bias magnetic field is generated around the bias magnetic field applying means 14, and the magnetic flux passes through the magnetostrictive element 12 and the coil 16. If the vibration is transmitted to the magnetostrictive element 12 through the substrate 24, the magnetostrictive element 12 is deformed in response to the acceleration of the vibration, so that the magnetic permeability of the magnetostrictive element 12 changes. Since this magnetostrictive effect is not accompanied by electrostrictive charge polarization, such as piezoelectric ceramics, the time required to change the permeability of the magnetostrictive element 12 in response to the acceleration of vibration is longer than the charge pole of piezoelectric ceramics. It takes less time to change. Therefore, the magnitude of the magnetic flux (5) (5) 200422621 passing through the coil 16 rapidly changes, and an induced electromotive force is generated in the coil 16. By measuring the voltage across the coil 16 with a voltmeter 18, vibration can be detected. The magnetostrictive element 12 is a giant magnetostrictive element and has a large change in magnetic permeability. On the other hand, since the induced electromotive force is large and is not easily affected by interference, the induced electromotive force of the coil 16 can be measured with high accuracy. The vibration sensor 10 can detect vibration in such a small amount of time with high reliability. Because the coil 16 and the two lead portions connected to it can be arranged on one side of the magnetostrictive element 12, it is not necessary to arrange the two lead portions to the magnetostrictive element 1 2 such as a vibration sensor using a piezoelectric ceramic. It is easy to arrange the two lead parts on both sides of the cable, and it is easy for the cymbal to flex, and it is difficult to work with excessive load. That is, breakage of a lead portion and the like is unlikely to occur, and in this respect, the reliability of the vibration sensor 10 is still high. Further, since the giant magnetostrictive element constituting the magnetostrictive element 12 can be formed into various shapes by powder metallurgy or the like, the productivity of the vibration sensor 10 is excellent. Furthermore, the structure of the vibration sensor 10, which is a combination of a substantially rectangular magnetostrictive element 12 and a rectangular plate-like bias magnetic field application means 14, is simple and small, so it can be easily mounted on a substrate by a chip mounter. , Generality Bureau. Next, a second embodiment of the present invention will be described. As shown in FIG. 2, the vibration sensor 20 of the second embodiment is provided with a magnetoresistive element 2 instead of the coil 16 as a magnetic field measurement means compared to the vibration sensor 10 of the first embodiment. member. And, instead of -8- (6) 200422621 voltmeter 18, resistance meter 24 is connected to magnetoresistive element 22. Since the other structures are the same as those of the vibration sensor 10 described above, the description is omitted.

Specifically, the 'magneto-resistive element 22 is an indium · antimony compound or the like, and has a property that the resistance 値 changes in response to a change in magnetic flux near the magnetostrictive element 12 caused by vibration. By measuring this change in resistance 値 with a resistance meter 24, vibration can be detected. Since the magnetostrictive element 12 is a giant magnetostrictive element, the change in the magnetic permeability is large, and relatively, the resistance 値 is large, and it is not easily affected by interference. That is, the vibration sensor 20 is also like the vibration sensor 10, and can reliably measure vibration within a small time, and has high reliability. Next, a third embodiment of the present invention will be described. As shown in FIG. 3, the vibration sensor 30 of the third embodiment is a vibration sensor 10 of the first embodiment, and includes a Hall element 32 instead of a coil 6 as a magnetic field measurement means. Building blocks. Since other structures are the same as those of the aforementioned vibration sensor 10, the description is omitted.

Specifically, the Hall element 32 is an indium · antimony compound, gallium · arsenic compound, or the like, and outputs a Hall voltage in response to a change in magnetic flux near the magnetostrictive element 12 caused by vibration. By measuring this Hall voltage with a voltmeter 18, vibration can be detected. The magnetostrictive element 12 is a giant magnetostrictive element and has a large change in magnetic permeability. Because the Hall voltage is so large that it is not easily affected by interference, the Hall voltage can be measured with high accuracy. That is, the vibration sensor 30, like the vibration sensors 10 and 20, can reliably measure the transmission of vibrations within the micrometer time, and has high reliability. Next, a fourth embodiment of the present invention will be described. (7) 200422621 As shown in FIG. 4, the vibration sensor 40 of the fourth embodiment is a vibration sensor 1 0 of the first embodiment, and the coil 16 is used as the first coil. The second coil 42 is provided to detect the acceleration in a plurality of directions. The second coil 42 has the same shape as the first coil 16 and is arranged close to one end surface in the longitudinal direction of the magnetostrictive element 12.

By providing two coils in this way, it is possible to detect the acceleration in the plural directions relative to the ground, and to detect vibrations in various modes. For example, it is possible to detect changes in the magnetic field in the multiple direction based on the induced electromotive force of the multiple coils, and to process vibrations in different directions by processing the detection results of each coil. It is also possible to detect the maximum chirp among vibration accelerations that vary in direction. In addition, as will be described later, a plurality of coils are appropriately arranged and connected to synthesize the induced electromotive force, and the detection result of each coil is not processed, the influence of the direction is excluded, and the maximum acceleration 检测 is detected.

Furthermore, it is also possible to relatively obtain a strong electrical signal by synthesizing the induced electromotive force of the complex line coil, reduce the influence of noise, and further improve the accuracy of vibration detection. In addition, although a plurality of (two) coils are provided as the magnetic field measurement means in the fourth embodiment, if a plurality of magnetoresistive elements shown in the second embodiment and a Hall element shown in the third embodiment are provided as Magnetic field measurement means will of course achieve the same effect. (Sinus Example 1) -10- (8) 200422621 The magnetostrictive element 12 is formed into a substantially rectangular body of 3.2 X 2 X 0 · 4 mm (mm), and the first coil 16 and the second coil 42 are respectively arranged in The top surface of the magnetostrictive element 12 and one end surface in the longitudinal direction (refer to FIG. 4). The number of turns of the coils 16 and 42 is 20 respectively. A horizontal vibration is applied to the thus-formed vibration sensor 40.

Make the vibration acceleration constant, change the direction, and measure the terminal voltage of the two coils 16 and 42. Fig. 5 shows the relationship between the acceleration direction of the vibration, the terminal voltages of the two coils 16 and 42 and their combined voltages. It can be seen from Fig. 5 that the terminal voltages of the coils 16 and 42 change with the vibration direction, and the resultant voltage is approximately constant regardless of the vibration direction. That is, the detection result of each line can be ignored, the influence of the direction can be excluded, and the maximum acceleration of the acceleration can be detected. It can be seen from FIG. 5 that the combined voltage of the terminal voltages of the two wires 616 and 42 is proportional to the magnitude of the acceleration, and it is possible to reliably detect vibrations whose acceleration exceeds 2000G.

(Embodiment 2) The magnetostrictive element 12 has a shape equivalent to that of the embodiment 1. On the other hand, a Hall element (Asahi Kasei Corporation) HW-108A is provided on the upper surface of the magnetostrictive element 12 and one end in the longitudinal direction, respectively, as a magnetic field measurement method (refer to FIG. 4). A horizontal direction vibration is applied to the thus constructed vibration sensor. As in the first embodiment, the vibration direction is changed, and the Hall voltage output from the two Hall elements is measured. Figure 7 shows the relationship between the acceleration direction of the vibration, the Hall voltage of the two Hall element, and the resultant voltage. Moreover, the magnitude of the acceleration is strange. Fig. 8 shows the relationship between the magnitude of acceleration and the combined voltage of the Hall voltages of the two Hall elements. It can be seen from Fig. 7 that 'the Hall voltage output by each Hall element changes with the vibration direction' On the other hand, the resultant voltage is almost constant regardless of the vibration direction.

In addition, it can be seen from FIG. 8 that the combined voltage of the Hall voltages of the two-Hall element is proportional to the magnitude of the acceleration, and it is possible to reliably detect vibrations whose acceleration exceeds 2000 G. Moreover, in the foregoing first to fourth embodiments, although a line coil, a magnetoresistive element, and a Hall element are shown as the field measurement means, the present invention is not limited to this, as long as the magnetic field can be measured within the micrometering time. A magnetic field measurement means may be used in which the magnitude of the magnetic field in the vicinity of the telescopic element is changed, and its type and structure are not limited.

In the first to fourth embodiments, magnetic field measuring means (coil, magnetoresistive element, and Hall element) are provided near the magnetostrictive element 12. However, the present invention is not limited to this. A magnetic field measuring means is arranged at a position near the magnetostrictive element at a magnetic field distance from the magnetostrictive element. A magnetic field measuring means may be provided in contact with the magnetostrictive element. In the fourth embodiment described above, the two magnetic field measurement means (coil) is used. However, the present invention is not limited to this, and three or more magnetic field measurement means may be used. In this way, more kinds of vibration can be detected. Further, in the first to third embodiments, the coil 16, the magnetoresistive element 2 and the Hall element 3 2 are arranged on the magnetostrictive element 12, -12- (10) 200422621 In the fourth embodiment, a second wire coil 42 is further disposed on one end surface of the magnetostrictive element 12 in the longitudinal direction as a magnetic field measurement method. However, the present invention is not limited to this. The acceleration direction of vibration is appropriately set.

In the first to fourth embodiments, the bias magnetic field applying means 14 is a ferrite magnet having a substantially rectangular plate-like body. However, the present invention is not limited to this, and other types of permanent magnets may be used. It is also possible to use an electromagnet. In the aforementioned first to fourth embodiments, although the magnetostrictive element 12 is substantially rectangular, the shape of the magnetostrictive element can be appropriately selected depending on the application, and for example, it may be a cylindrical magnetostrictive element.

Moreover, in the aforementioned first to fourth embodiments, although the magnetostrictive element 12 is a giant magnetostrictive element composed of lanthanide and iron group elements, the present invention is not limited to this, as long as it is magnetostrictive The element of the telescopic effect is sufficient. The material is not particularly limited. In order to surely detect vibrations within a small amplitude time, it is preferable to use a giant magnetostrictive element with a large magnetic permeability relative to deformation. The industrial applicability is as described above. According to the present invention, it is possible to reliably detect vibrations within a small amplitude time. Excellent effect. [Brief description of the drawings] Fig. 1 is a side view illustrating the structure of a vibration sensor -13- (11) 200422621 according to the first embodiment of the present invention. Fig. 2 is a side view illustrating the structure of a vibration sensor according to a second embodiment of the present invention. Fig. 3 is a side view illustrating the structure of a vibration sensor according to a third embodiment of the present invention. Fig. 4 is a side view illustrating the structure of a vibration sensor according to a fourth embodiment of the present invention.

Fig. 5 is a graph showing the relationship between the vibration acceleration direction and the measured voltage of the vibration sensor according to the first embodiment of the present invention. Fig. 6 is a graph showing the relationship between the magnitude of vibration acceleration and the measured voltage of the same vibration sensor. Fig. 7 is a graph showing a relationship between a vibration acceleration direction and a measured voltage of a vibration sensor according to a second embodiment of the present invention. Fig. 8 is a graph showing the relationship between the vibration acceleration direction and the measured voltage of the same vibration sensor.

Main documents comparison table 10, 20, 30, 40: Vibration sensor 1 2: Magnetostrictive element 1 4: Bias magnetic field applying means 16, 42: Coil (magnetic field measuring means) 1 7: Amplifying circuit 1 8: Voltage Meter 22: magnetoresistive element-14- 200422621

Claims (1)

(1) (1) 200422621 Pick up and apply for patent scope 1. A vibration sensor, characterized in that it has a magnetostrictive element that responds to the acceleration of the seismic number and changes in permeability, and is used to apply a bias magnetic field to the magnetostrictive element Means for applying a bias magnetic field and magnetic field measuring means for measuring the strength of a magnetic field near a magnetostrictive element. 2. The vibration sensor according to item 1 of the scope of patent application, wherein the magnetostrictive element is a giant magnetostrictive element composed of lanthanide group elements and iron group elements. % 3. The vibration sensor according to item 1 of the patent application range, wherein the aforementioned biasing magnetic field application means is a permanent magnet. 4. The vibration sensor according to item 2 of the patent application range, wherein the aforementioned means for applying a bias magnetic field is a permanent magnet. 5. The vibration sensor according to any one of claims 1 to 4, in which the aforementioned magnetic field measuring means is provided with a plurality of means to measure the acceleration in the complex direction of the vibration. 6 · Vibration sensor according to any one of the scope of patent applications 1 to 4. The magnetic field measuring means has a structure including a coil arranged near the magnetostrictive element. 7. The vibration sensor according to item 5 of the patent application, wherein the magnetic field measuring means has a structure provided with a coil disposed near the magnetostrictive element 1. 8. The vibration sensor according to any one of claims 1 to 4, wherein the aforementioned magnetic field measurement means is a structure provided with a magnetoresistive element. 9. The vibration sensor according to item 5 of the scope of patent application, wherein the aforementioned magnetic field measurement means -16-(2) (2) 200422621 has a structure having a magnetoresistive element. 10. The vibration sensor according to item 6 of the patent application scope, wherein the magnetic field measurement means is a structure having a magnetoresistive element. 1 1. The vibration sensor according to item 7 of the patent application, wherein the magnetic field measurement means is a structure having a magnetoresistive element. 1 2. The vibration sensor according to any one of claims 1 to 4, wherein the aforementioned magnetic field measurement means has a structure having a Hall element. 1 3. The vibration sensor according to item 5 of the patent application scope, wherein the aforementioned magnetic field measurement means is a structure provided with a Hall element. 14. The vibration sensor according to item 6 of the patent application scope, wherein the aforementioned magnetic field measurement means is a structure provided with a Hall element. 15. The vibration sensor according to item 7 of the patent application scope, wherein the aforementioned magnetic field measurement means is a structure provided with a Hall element. 16. The vibration sensor according to item 8 of the scope of patent application, wherein the magnetic field measurement means is a structure provided with a Hall element.