Communications: electrical – Vehicle detectors
Reexamination Certificate
1998-08-27
2002-06-18
Pope, Daryl (Department: 2736)
Communications: electrical
Vehicle detectors
C340S572100, C340S572800, C340S941000, C428S928000, C148S304000, C148S311000
Reexamination Certificate
active
06407676
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetostrictive resonator whose presence can be detected by a magnetostrictive resonator detection apparatus based on a magnetostriction phenomenon, a road in which the magnetostrictive resonator is buried, and a method of burying the magnetostrictive resonator.
2. Description of the Related Art
In recent years, application of magnetostrictive resonators has widened in such a manner that magnetostrictive resonators are buried in a road for detecting a vehicle on the road or that a magnetostrictive resonator is attached to a commodity product: in a store for finding the commodity product not yet paid for and illegally taken out at the exit of the store.
A phenomenon in which dimension change called “Joule effect” is caused by applying ani external magnetic field to ferrite, amorphous material of ferromagnetic material, etc., is referred to as a magnetostriction phenomenon. If an AC magnetic field is applied to a magnetostrictive member having such nature by a calling electromagnetic wave while a bias magnetic field like a direct current is applied to the magnetostrictive member, when the AC magnetic field gives magnetostrictive displacement to magnetostrictive resonator and the frequency of the AC magnetic field matches the resonance frequency of the magnetostrictive member, the maximum magnetostrictive displacement can be given to the magnetostrictive resonator. If the AC magnetic field caused by the calling electromagnetic wave is stopped, mechanical resonance of the magnetostrictive resonator causes an electromagnetic wave to be generated only for a short time, thus the electromagnetic wave can be detected for detecting the presence of the magnetostrictive resonator.
The detection method will be simply discussed. As shown in
FIG. 9
, a rectangular magnetostrictive member
31
is made of a thin plate provided by extending a ferromagnetic substance of amorphous material, etc., and a magnetized magnetic member
32
like a tape belt, for example, is placed near the magnetostrictive member
31
. In this state, a calling electromagnetic wave is projected from the arrow X direction for AC excitation. When the frequency is changed and matches the resonance frequency of the magnetostrictive member
31
, the magnetostrictive member
31
vibrates in the length direction thereof.
FIG. 10
shows the magnetization displacement characteristic. If the magnetic member
32
does not exist, vibration of displacement width Mo is produced for AC excitation Ho; if magnetic bias Hd caused by the magnetic member
32
is applied, vibration of displacement width MA can be produced for AC excitation HA caused by the calling electromagnetic wave. If the calling electromagnetic wave is stopped, mechanical resonance of the magnetostrictive member
31
continues for a short time and the magnetostrictive member
31
is generated by a villery effect in which the magnetization state changes in response to deformation of the magnetostrictive member
31
because of a mechanical stress caused by the mechanical resonance, thus the electromagnetic wave can be detected for knowing the presence of the magnetostrictive member. If a number of magnetostrictive members different in resonance frequency are combined and placed, a combination of the resonance frequencies is detected, whereby specific information indicated by the position can also be known.
FIG. 11
shows a conventional magnetostrictive resonator example. The magnetostrictive resonator comprises two magnetostrictive members
41
a
and
41
b
like extended thin plates placed in a frame
42
and brought close to a magnetic material
43
of a ferromagnetic substance magnetized. The magnetostrictive members
41
a
and
41
b
differ in length and resonate with different resonance frequencies, thus can cover different calling frequencies.
Since the conventional magnetostrictive resonator as shown in
FIG. 11
comprises a number of magnetostrictive members housed in the frame
42
, the magnetostrictive members
41
a
and
41
b
may come in contact with each other depending on the attitude, causing the vibration mode to change or the frequency to shift as hindrance. It is also feared that play in the shorter magnetostrictive member
41
b
may occur in the frame
42
and the magnetostrictive member
41
b
may move in the frame, so that the magnetostrictive member goes away from a detection antenna.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a small and compact magnetostrictive resonator that can comprise various magnetostrictive members in combination, a road in which the magnetostrictive resonator is buried, and a method of burying the magnetostrictive resonator.
To the end, according to a first aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a first magnetostrictive member placed facing one side of the magnetic member, a second magnetostrictive member placed facing the opposite side of the magnetic member, a first storage body provided with a storage section for storing the first magnetostrictive member, and a second storage body provided with a storage section for storing the second magnetostrictive member, so that the magnetostrictive resonator having two magnetostrictive members placed on both sides of the magnetic member can be formed small and compact.
In a second aspect of the invention, in the magnetostrictive resonator according to a first aspect of the invention, the first and second magnetostrictive members differ in length, so that the magnetostrictive resonator having two different resonance frequencies can be formed small and compact.
In a third aspect of the invention, in the magnetostrictive resonator according to a second aspect of the invention, one end in the length direction of the first magnetostrictive member and one end in the length direction of the second magnetostrictive member are at symmetrical positions with each other with the belt-like magnetic member between, so that the magnetostrictive resonator having two different resonance frequencies can be formed small and compact and the radio wave emitted from the magnetostrictive member can be detected with high sensitivity at an antenna disposed on such one end.
In a fourth aspect of the invention, in the magnetostrictive resonator according to the second or third aspect of the invention, the storage sections of the first and second storage bodies differ in dimensions matching the dimensions of the first and second magnetostrictive members stored in the first and second storage bodies, so that play in the magnetostrictive member in the storage section can be eliminated.
In a fifth aspect of the invention, in a first aspect of the magnetostrictive resonator, the belt-like magnetic member is magnetized on both sides as different patterns, so that if the size of the magnetostrictive member or the storage section in the frame is not changed, the resonance frequency can be changed only by changing the magnetization method and the types of parts can be lessened.
According to a sixth aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a plurality of magnetostrictive members facing one side of the magnetic member and being aligned in the length direction, and a storage body provided with a storage section for separately storing the magnetostrictive members. According to a seventh aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a plurality of magnetostrictive members facing one side of the belt-like magnetic member and being placed so that the long sides of the magnetostrictive members are aligned, and a storage body provided with a storage section for separately storing the magnetostrictive members. Thus, the magnetostrictive resonator having a plurality of magnetostrictive members can be formed small and comp
Kamata Joji
Tanji Yoshihiko
Yoshioka Toshihiro
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Pope Daryl
LandOfFree
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