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JPH0938081

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH0938081
[0001]
BACKGROUND OF THE INVENTION Although the resonance frequency of an ultrasonic
transducer changes in principle when the ultrasonic transducer comes in contact with an object,
the present invention uses an ultrasonic transducer having such a principle. The present
invention relates to a hardness sensor that quantitatively measures the degree of hardness of soft
tissue such as a human body.
[0002]
2. Description of the Related Art The operation of a conventional hardness sensor utilizing the
principle of an ultrasonic transducer is shown in FIG. 5, which will now be described. A contact
probe is attached to the end of one of the cylindrical ultrasonic transducers A, and a cylindrical
detection transducer C is provided between the ultrasonic transducers A and B. For example, the
whole of both the ultrasonic transducers a and b and the detecting transducer c are held by a
polyurethane holder d.
[0003]
In such an apparatus, when a voltage generated from an amplification circuit in the circuit E is
applied to the ultrasonic transducer via the filter circuit, the ultrasonic transducer produces an
electrostrictive action, but the ultrasound The distortion due to the vibrator is detected, and the
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detection vibrator generates a voltage. The voltage generated by the detection vibrator c is fed
back to the ultrasonic vibrator i again through the amplifier circuit and the filter circuit in the
circuit E, and self-oscillation occurs at the resonance frequency of the ultrasonic vibrator i. Under
such a condition, when the contactor abuts on the object M (for example, a human body) and
contacts the resonance frequency, the hardness of the object M is measured by measuring the
change amount of the resonance frequency with the frequency counter c. The degree of hardness
can be confirmed quantitatively with a hardness indicator.
[0004]
As described above, according to the conventional hardness sensor capable of quantitatively
confirming the degree of hardness of the object M by the change amount of the resonance
frequency of the cylindrical ultrasonic transducer i, the cylindrical shape is In the ultrasonic
transducer B, there are two vibration modes of the radial direction and the axial direction of the
ultrasonic transducer B, and the resonance state becomes complicated. Therefore, the signal from
the detection transducer C is ultrasonic wave There is a drawback that the filter adjustment
operation for feedback to the child is troublesome.
[0005]
In addition, since the entire ultrasonic transducer B and the detecting transducer C are held by
the polyurethane holder D, the ultrasonic transducer B and the transducer itself such as the
detecting transducer C have There is also a problem that the resonance mode is easily changed,
which causes an error in measurement of the degree of hardness of tissue such as an object.
In addition, since the hardness sensor can not simultaneously measure the degree of hardness of
an object by palpation, it is inconvenient for measuring the hardness of an object that is easily
changed over time. In particular, when the object is a soft tissue such as a human body, an error
tends to appear in the measurement of hardness depending on the magnitude of the pressing
pressure by the contactor.
[0006]
In order to solve these problems, a flat plate-like ultrasonic transducer that vibrates in the radial
direction, a detection transducer for detecting the vibration of the ultrasonic transducer, an
ultrasonic transducer and a detection transducer are used. Hardness sensor, etc., comprising a
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flat common electrode interposed between them, a contact connected to and attached to the
common electrode, and a holder that fixes the point contact of ultrasonic waves propagating
through the common electrode. Are being developed in various ways. However, since each
transducer of these hardness sensors is separately processed and bonded, an error is likely to
occur due to the bonding state or the difference in the natural frequency of each transducer.
[0007]
In view of the problems of the prior art as described above, the hardness sensor according to the
present invention simultaneously performs palpation on the object to be measured and
measurement of the degree of hardness by the sensor and at the same time attempts to reduce
measurement error as much as possible. It is.
[0008]
According to the invention of claim 1, the main body of the hardness sensor A is made of a
piezoelectric ceramic, and a circular electrostrictive ultrasonic transducer 1 which vibrates in the
radial direction by electrode-treating the surface. Between the ultrasonic transducer 1 and the
circular detection transducer 2 for detecting the vibration thereof, and the disc-like common
electrode 3 made of a conductor is interposed between the ultrasonic transducer 1 and the
ultrasonic transducer 1 for detection. The vibrator 2 and the common electrode 3 are integrally
polymerized in the central axis direction, and the common electrode 3 is characterized in that a
contact 4 which is in contact with an object M is joined and mounted.
[0009]
According to the configuration of the first aspect of the invention, the electrostrictive ultrasonic
transducer 1 is in the single vibration mode only in the radial direction, so filter adjustment for
self-oscillation is easy.
When the contactor 4 is not in contact with an object (for example, the human body M), it
oscillates at the natural frequency of the ultrasonic transducer 1, but when the contactor 4 is in
contact with the object M (for example, human body), resonance occurs The frequency changes.
The degree of change of the resonance frequency is measured by the frequency counter 9
through the amplification circuit 7 of the circuit 6 and the filter 8 to confirm the degree of
hardness of the object by the hardness indicator 10.
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[0010]
In the invention of claim 2 according to the invention of claim 1, the hardness sensor A is housed
and mounted in a pen-shaped housing B, and the common electrode 3 has a plurality of contacts
of ultrasonic waves for propagating vibration. It is characterized in that it is held by the holder 5
so as to be in point contact with h, h, h, h. According to the second aspect of the present
invention, the sensor unit is held in point contact to reduce the change in the resonant frequency
of the electrostrictive ultrasonic transducer 1 caused by the contact of the holder 5.
[0011]
According to the invention of claim 3, in the invention of claim 1, the finger F of the human body
is placed on the hardness sensor A, housed in the housing H, and the insulating portion is
interposed between the finger F and the hardness sensor A By providing the hardness sensor A
and the finger F so as not to be in direct contact with each other and feeling the pressing
pressure with the finger F when the contactor 4 contacts the object, the hardness of the object M
(for example, human body) by the hardness sensor A Measurement and palpation with a finger F
at the same time.
[0012]
According to the configuration of the third aspect of the present invention, even if it is an object
whose hardness changes with time, the comparison between the sense of the finger F and the
measurement of the hardness sensor A is accurately performed.
According to the invention of claim 4, in the invention of claim 3, the pressure sensor S is
installed between the finger F and the hardness sensor A, and the load monitor K is connected to
this, It is characterized in that the pressing pressure at the time of coming into contact with the
changing object is monitored by the load monitor K.
[0013]
According to the configuration of the fourth aspect of the present invention, even when the
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hardness changes due to the influence of the pressing pressure, reproducible measurement
values can be obtained. In each of the second, third, and fourth inventions, as in the first
invention, the ultrasonic transducer 1 is unique when the contactor 4 is not in contact with the
object M (for example, a human body). Although oscillating at a frequency, when the contactor 4
abuts on and contacts the object M, the resonant frequency changes. The degree of change of the
resonance frequency is measured by the frequency counter 9 through the amplification circuit 7
of the circuit 6 and the filter 8 to confirm the degree of hardness of the object by the hardness
indicator 10.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings. FIG. 1 shows an embodiment of the invention of
the hardness sensor according to the present invention, and FIG. 1 (a) is an external perspective
view of the hardness sensor, and FIG. 1 (b) is a line XX 'of the same. It is a cross-sectional front
view in. The main body of the hardness sensor is made of piezoelectric ceramic, and the surface
is subjected to electrode treatment (plating treatment such as nickel-chromium treatment) to
form a circular electrostrictive ultrasonic transducer 1 which vibrates in the radial direction. A
disk-shaped common electrode 3 made of a conductor such as Be-Cu is interposed between the
sensor 1 and the circular detecting transducer 2 for detecting its vibration, and the ultrasonic
transducer 1 and the detecting transducer A contact sensor 4 which contacts the object M (such
as a human body) is joined and attached to the common electrode 3 so as to form a hardness
sensor A. It is done.
[0015]
FIGS. 2, 3 and 4 are electric circuit diagrams for explaining the use of the hardness sensor
according to the present invention. FIG. 2 is an electric circuit diagram of a first application of the
hardness sensor according to the present invention. The hardness sensor A is housed and
mounted in a pen-shaped housing B, and the common electrode 3 is in point contact with a
plurality of ultrasonic contacts h, h, h, h for propagating vibrations. Is held by the holder 5.
[0016]
In a state where the contactor 4 is not in contact with the object M (for example, a human body),
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it oscillates at the natural frequency of the ultrasonic transducer 1 but when the contactor 4 is in
contact with the object M (for example a human body) Changes. The degree of change of the
resonance frequency is measured by the frequency counter 9 through the amplification circuit 7
and the filter 8 of the circuit 6, and the degree of hardness of the object M is confirmed by the
hardness indicator 10.
[0017]
FIG. 3 is an electric circuit diagram of a second application of the hardness sensor according to
the present invention. The finger F of the human body is placed on the hardness sensor A and
housed in the inside of the housing H. However, in this state, an insulating portion (not shown) is
provided between the finger F and the hardness sensor A so that the hardness sensor A and the
finger F do not come in direct contact with each other. In this second usage schematic, the
pressing force when the contactor 4 abuts on the object M (for example, the shoulder of the
human body) can be felt with the finger F, and the hardness sensor A measures the hardness of
the object M And palpation with the finger F can be performed simultaneously.
[0018]
FIG. 4 is an electric circuit diagram of a third application of the hardness sensor according to the
present invention. The finger F of the human body is placed on the hardness sensor A and stored
in the housing H. However, the pressure sensor S is installed between the finger F and the
hardness sensor A, and the load monitor K is It is possible to constantly reproduce a constant
value of load by monitoring the pressing pressure at the time of contact with an object M (for
example, the shoulder of a human body) whose hardness changes due to the influence of
pressing pressure by the contacts 4 connected by the load monitor K To reduce the measurement
error.
[0019]
The electric circuit diagram of the second use procedure shown in FIG. 3 and the electric circuit
diagram of the third use procedure shown in FIG. 4 both show the operation of the amplifier
circuit 7, the filter 8 and the frequency counter 9 in FIG. It is the same as the case of the
electrical circuit diagram of the first use point.
[0020]
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the
amount of change in the resonant frequency of the ultrasonic transducer 1 shown in FIGS. 1, 2, 3
and 4 is determined by the frequency counter 9 via the amplifier circuit 7 and the filter 8 of the
circuit 6. In measurement, the resonance frequency fm is generally determined by the following
equation.
fm (Hz) = (αt / 2πr2) √ {Y / 12ρ × (1−σ2)} where fm is a resonance frequency, α is a
boundary condition constant, t is a thickness of the common electrode, and r is a value of the
common electrode 3. A radius, Y is a Young's modulus, ρ is a density of the common electrode 3,
and σ is a Poisson's ratio. For example, when the outer diameter of the common electrode 3
made of a conductor such as Be-Cu material is 9 mm and the thickness is 0.8 mm, the peripheral
support diameter is about φ 6.8 and the resonance frequency fm is fm 51 51 kHz.
[0021]
The hardness sensor A preferably has a diameter of 5 mm to 20 mm and a thickness of 2 mm or
less from the viewpoint of simultaneously performing measurement of hardness by the hardness
sensor A and palpation with a finger F.
[0022]
According to the first aspect of the present invention, the degree of hardness of the object can be
confirmed by the hardness indicator by measuring the amount of change of the resonance
frequency with the frequency counter through the amplification circuit and the filter of the
circuit.
According to the second aspect of the invention, in addition to the advantage of the first aspect of
the invention, the sensor unit can be held in point contact to reduce the change in the resonant
frequency of the electrostrictive ultrasonic transducer due to the contact of the holder.
[0023]
According to the third aspect of the invention, in addition to the advantages of the first aspect of
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the invention, it is possible to accurately compare the sense of the finger with the measurement
by the hardness sensor even for an object whose hardness varies with time. According to the
invention of claim 4, in addition to the advantages of the invention of claim 1 and claim 3, even
in the case of an object whose hardness changes under the influence of the pressing pressure,
reproducible measurement values can be obtained.
[0024]
Brief description of the drawings
[0025]
1 shows an embodiment of the invention of the hardness sensor according to the present
invention, (a) is an external appearance perspective view of the hardness sensor, (b) is a crosssectional front view along the line XX 'of the same FIG.
[0026]
2 is an electrical circuit diagram showing a first use of the hardness sensor according to the
present invention.
[0027]
3 is an electric circuit diagram showing a second use point of the same.
[0028]
4 is an electric circuit diagram showing a third use point of the same.
[0029]
5 is an electric circuit diagram showing a usage of the conventional hardness sensor.
[0030]
Explanation of sign
[0031]
1 electrostrictive ultrasonic transducer 2 transducer for detection 3 common electrode 4
contactor A hardness sensor
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