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JP2003218805

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2003218805
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an electric
power and signal that enables ultrasonic waves to be used to supply power to implantable
devices and the like, as well as exchange various signals with these devices. The present
invention relates to a transmission apparatus. Here, the implantable device includes not only a
cardiac pacemaker and an artificial heart but also sensors such as a blood monitor.
[0002]
2. Description of the Related Art Conventionally, use of a primary battery such as a mercury
battery or a lithium battery is generally used as means for supplying power to implantable
devices and the like. A method of providing a secondary battery in the implantable device and
charging the secondary battery using ultrasonic energy is being proposed (JP-A 50-9041, JP-A
50-9042). According to this method, battery replacement due to surgery can be eliminated, and
physical burden on the patient can be alleviated.
[0003]
However, in a power transmission device using such ultrasonic waves, the transmission efficiency
of power is improved by matching the mechanical impedance and matching the electrical load
impedance. However, if there is a shift in the propagation axis (misalignment factor) between the
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transmitter placed outside the body and the receiver placed inside the body, the power
transmission efficiency will drop significantly. Here, the misalignment factor means the lateral
shift of the transmission and reception wavefronts in the transmitting and receiving ultrasonic
transducers, the non-parallel (inclination) of the opposing transmission and reception wavefronts,
and the transmission. -It is a distance between faces of the receiving surface. Further, the
conventional device is a system in which power transmission and control signal transmission are
alternately performed, and the transmission efficiency is reduced by the intermittent power
transmission.
[0004]
FIG. 6 shows the relationship of misalignment factors. In the figure, 11 is a first ultrasonic
transducer (transmission side), 12 is a drive source for supplying a drive signal to the first
ultrasonic transducer 11, 21 is a second ultrasonic transducer (reception side) And 22 are loads
such as a rectifier circuit connected to the second ultrasonic transducer 21. In FIG. 6 (a), r is the
diameter of the transmission / reception wavefront, Δr is the lateral displacement of the face
center of the transmission / reception wavefront, and the degree of displacement is represented
by Δr / r. Also, d is the distance between the transmitting and receiving surfaces. In FIG. 6 (b), θ
is the non-parallel (inclination) of the opposing transmitting and receiving wavefronts.
[0005]
That is, efficient power transmission can be realized by eliminating these misalignment factors.
The inter-plane distance d can not be zero in principle, so an optimum value is searched. In
addition, when eliminating the misalignment factor and realizing an efficient power transmission
state, it is possible to realize signal transmission with less noise by using this transmission path.
[0006]
According to the present invention, in the above-described power transmission device using
ultrasonic waves, it is possible to eliminate the cause of misalignment between the ultrasonic
transducers disposed opposite to each other and to supply power by continuous ultrasonic
signals. The purpose is to realize efficient power transmission.
[0007]
In addition, the present invention realizes a power and signal transmission device that supplies
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2
power to implantable devices and the like using ultrasonic waves and that can also transmit and
receive various signals with these devices. The purpose is to
[0008]
SUMMARY OF THE INVENTION In order to achieve the above object, the power and signal
transmission device using ultrasonic waves of the present invention is a secondary power supply
circuit for load circuits such as implantable devices. A battery, first and second ultrasonic
transducers manufactured to have the same characteristics and disposed to face each other, and
transmission / reception wavefronts of the first and second ultrasonic transducers, and their
nominal frequencies A metal matching plate having a plate thickness of about 1⁄4 wavelength, a
drive source for supplying a drive signal for power transmission to the first ultrasonic
transducer, and the second ultrasonic transducer A rectifier circuit which rectifies an obtained
output signal and supplies the same to the secondary battery, receives an output of the rectifier
circuit, generates a frequency signal according to the signal level, and uses the frequency signal
as a monitor signal to generate the second ultrasonic wave. Monitor circuit to supply the
vibrator, and An attitude control device that controls the attitude of a first ultrasonic transducer
and adjusts the propagation axis of the first ultrasonic transducer and the second ultrasonic
transducer, and the first ultrasonic transducer And a monitor reception circuit for detecting a
monitor signal received by the controller and returning the same to the attitude control device,
and selecting a frequency of a drive signal generated by the drive source as a first resonance
frequency band in the ultrasonic transducer. The frequency of the monitor signal generated by
the monitor circuit is selected as a second resonance frequency band in the ultrasonic
transducer.
[0009]
Further, the power and signal transmission apparatus using ultrasonic waves according to the
present invention utilizes a metal case such as an implantable device as a metal matching plate
joined to the transmission / reception wavefront of the second ultrasonic transducer. It is.
[0010]
Furthermore, in the power and signal transmission apparatus using ultrasonic waves according
to the present invention, transmission and reception of signals other than monitor signals using
resonant frequency bands other than the first resonant frequency band in the first and second
ultrasonic transducers. It is also characterized by
[0011]
Thus, when a metal matching plate having a plate thickness of about 1⁄4 wavelength with respect
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to the nominal frequency is joined to the transmission / reception wavefront of the ultrasonic
transducer, the ultrasonic transducer can have multi-channel characteristics. While transmitting
power using the first channel (resonance frequency band) and transmitting the monitor signal for
positioning using the other channel (resonance frequency band), it is possible to face each other.
While eliminating the cause of misalignment between the ultrasonic transducers, it is possible to
realize efficient power transmission, and it is possible to supply power by continuous ultrasonic
signals, and to realize further efficient power transmission. Can.
[0012]
Further, by utilizing the multi-channel characteristic of the ultrasonic transducer, it is possible to
exchange information signals other than the monitor signal via another channel (resonance
frequency band).
[0013]
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described
below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a power and signal transmission apparatus
using ultrasonic waves according to the present invention.
The device shown is illustrative of the case where power is supplied to an implantable device
such as a cardiac pacemaker.
In the figure, the same components as those in FIG. 6 are denoted by the same reference
numerals.
1 is an extracorporeal unit, 2 is an intracorporeal unit.
The first and second ultrasonic transducers 11 and 21 are ultrasonic transducers manufactured
to have the same characteristics, and the transmitting and receiving wavefronts of the first
ultrasonic transducer 11 have the nominal frequency fo A metal matching plate 13 having a
plate thickness ts of approximately 1⁄4 wavelength is joined.
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Here, the nominal frequency fo refers to the half-wave thickness resonant frequency of the
piezoelectric ceramic vibrator, and the plate thickness ts of approximately 1⁄4 wavelength refers
to the resonant frequency of the vibrator alone and the acoustic impedance of the vibrator
material and It is a thickness of 1⁄4 wavelength calculated using the longitudinal wave
propagation velocity (sound velocity).
Reference numeral 23 denotes a metal case of the internal unit 2, which is processed to the same
thickness ts as the metal matching plate 13 and joined to the transmission / reception wavefront
of the second ultrasonic transducer 21. That is, the second ultrasonic transducer 21 uses the
metal case 23 as a metal matching plate.
[0014]
Usually, the in-vivo device is covered with a metal plate such as titanium or stainless steel, which
has a large shielding effect against ultrasonic waves, but as described above, the plate thickness
of the metal case 23 By selecting a value of 4 wavelengths, it can act as an acoustic impedance
converter (matching layer) between the biological medium and the second ultrasonic transducer
21 and reduce the shielding effect of ultrasonic waves in the metal case 23 . Hereinafter, the
metal case 23 is referred to as a metal matching plate 23.
[0015]
Reference numeral 24 denotes a cardiac pacemaker, and reference numeral 25 denotes a
secondary battery for supplying power to the cardiac pacemaker 24. 26 rectifies the output
signal obtained from the second ultrasonic transducer 21 and supplies it to the secondary
battery 25, and generates a frequency signal according to the received wave level, and this
frequency signal is used as a monitor signal as a second monitor signal. Of the ultrasonic
transducer 21 of FIG. The first and second ultrasonic transducers 11 and 21 are disposed
opposite to each other at a distance of 5 to 20 mm via the skin and subcutaneous tissue. 14 is an
attitude control device that controls the attitude of the first ultrasonic transducer 11 and adjusts
the propagation axis of the first ultrasonic transducer 11 and the second ultrasonic transducer
21; 15 is a first The monitor reception circuit detects a monitor signal received by the ultrasonic
transducer 11 and feeds it back to the attitude control device 14. The attitude control device 14
adjusts the position and inclination of the first ultrasonic transducer 11 in the three-dimensional
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direction so as to eliminate the misalignment factor of the propagation axis as shown in FIG.
[0016]
FIG. 2 is a block diagram showing an embodiment of the charging circuit 26. As shown in FIG. As
shown in the figure, the charging circuit 26 is composed of a rectifying circuit 261 and a
monitoring circuit 262. The rectifying circuit 261 rectifies the output signal So obtained from the
second ultrasonic transducer 21, and the secondary battery 25 is Supply to The monitor circuit
262 receives the output Sd of the rectifier circuit 261, generates a frequency signal according to
the signal level, and supplies this frequency signal as the monitor signal Sm to the second
ultrasonic transducer 21. The ultrasonic transducer 21 is excited. That is, an ultrasonic signal for
supplying power is transmitted from the first ultrasonic transducer 11 to the second ultrasonic
transducer 21, and the monitor signal Sm is transmitted from the second ultrasonic transducer
21 to the first ultrasonic transducer 21. It is transmitted to the acoustic transducer 11.
[0017]
When the position of the first ultrasonic transducer 11 changes and the misalignment factor of
the propagation axis changes, the transmission efficiency of the ultrasonic waves changes, and
the signal level of the output Sd changes. Therefore, as in a general servo mechanism, if the
position (posture) of the first ultrasonic transducer 11 is controlled while detecting the level of
the output Sd, the misalignment factor of the propagation axis is eliminated, and the efficient
transmission state Can be realized. The attitude control device 14 adjusts the position (attitude)
of the first ultrasonic transducer 11 while detecting the change of the monitor signal Sm, and
sequentially optimizes the deviation Δr / r of the propagation axis, the inclination θ, and the
inter-plane distance d. It will be set to the state. Since the monitor signal Sm periodically changes
every 2d / λm with respect to the change of the inter-plane distance d, it is also possible to
determine the optimum position. λ m is the wavelength in the medium.
[0018]
Referring back to FIG. 1, when the first and second ultrasonic transducers 11 and 21 are joined
to the metal matching plates 13 and 23 having a plate thickness ts of about 1⁄4 wavelength with
respect to the nominal frequency fo, The actual resonance points of the first and second
ultrasonic transducers 11 and 21 deviate from the nominal frequency fo and take a plurality of
values.
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[0019]
FIG. 3 shows an example of the frequency characteristics of the first and second ultrasonic
transducers 11 and 21. In the example shown in the figure, two resonance points (f1 at
approximately symmetrical positions from the point of f = fo) are shown. , F2) appear.
In the figure, the solid line is the theoretical value and the broken line is the experimental value.
This is due to the relationship between the nominal frequency fo of the vibrator and the
thickness ts of the metal matching plate, and depending on the thickness of the metal matching
plate, three resonance points (f1, f2,. f3) may appear. This is called multi-channel characteristics
of the ultrasonic transducer. This multi-channel characteristic is a characteristic realized by using
a metal matching plate having high values of both acoustic impedance and longitudinal wave
propagation velocity (sound velocity), and is a plastic material used for transducers for medical
imaging. Does not appear if you use. In the present invention, power is transmitted using the first
channel (resonance frequency band), and the monitor signal for positioning is transmitted using
the other channel (resonance frequency band).
[0020]
That is, the drive source 12 generates a drive signal of the frequency f1 belonging to the first
resonance frequency band to drive the first ultrasonic transducer 11. Further, the monitor circuit
252 generates a monitor signal Sm having a frequency f2 belonging to the second resonant
frequency band as a basic frequency, and drives the second ultrasonic transducer 21. The
monitor reception circuit 15 extracts the monitor signal Sm from the output signal of the first
ultrasonic transducer 11 using a filter circuit or the like, and feeds it back to the attitude control
device 14.
[0021]
As described above, when power transmission and monitor signal transmission are performed
using different channels (resonance frequency bands), continuous ultrasonic signals can be used
for power transmission, and transmission efficiency is further enhanced. You can get
[0022]
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In the above description, although the case of adjusting the propagation axis using monitor signal
Sm has been exemplified, similarly, a drive signal for exciting first ultrasonic transducer 11 using
monitor signal Sm Can be controlled to an optimal value.
That is the signal path shown by the broken line in the figure.
[0023]
FIG. 5 is a block diagram showing another embodiment of the power and signal transmission
apparatus using ultrasonic waves according to the present invention. The apparatus shown in the
figure exemplifies an implantable sensor such as a blood monitor as the implantable device, and
supplies power from the extracorporeal unit 1 to the intracorporeal unit 2 (sensor), and the
extracorporeal unit 1 and the intracorporeal unit 2 Between the sensor and the control
information signal for controlling the sensor. In the figure, 27 is a sensor such as a blood
monitor, 16 belongs to the extracorporeal unit 1 and receives a measurement information signal
Ss transmitted by the sensor 27 or an information input for transmitting a control information
signal Sc for controlling the sensor 27. It is an output circuit. Here, assuming that the first and
second ultrasonic transducers 11 and 21 have three resonance points (f1, f2, f3) as shown in FIG.
4, the sensor 27 has a third resonance frequency band. The measurement information signal Ss
is transmitted using the frequency f3 belonging to. The information input / output circuit 16
selectively receives the measurement information signal Ss belonging to the third resonant
frequency band, and transmits the control information signal Sc using the same third resonant
frequency band. The measurement information signal Ss includes information such as a
measurement value and measurement time, and the control information signal Sc includes setting
information of the measurement cycle for the sensor 27 and the like. Transmission from the
sensor 27 and transmission from the information input / output circuit 16 are generally
performed alternately in time division.
[0024]
As described above, by transmitting and receiving information using the third resonance
frequency band, signal transmission with less noise can be realized without affecting the
transmission of power. In the above example, the monitor signal Sm is transmitted using the
second resonance frequency band, and other signals (the measurement information signal Ss and
the control information signal Sc) are transmitted using the third resonance frequency band.
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Although the case of performing transmission is illustrated, the method of using the resonant
frequency band is not limited to this, and, for example, the monitor signal Sm and the other
signals are time-division using the same second resonant frequency band It is also possible to do.
[0025]
As described above, the power and signal transmission apparatus using ultrasonic waves
according to the present invention is manufactured in line with characteristics of a secondary
battery for supplying power to a load circuit such as an implantable device. First and second
ultrasonic transducers disposed opposite to each other, and the transmitting and receiving
wavefronts of the first and second ultrasonic transducers, and having approximately a quarter
wavelength with respect to the nominal frequency thereof A metal matching plate having a plate
thickness, a drive source for supplying a drive signal for power transmission to the first
ultrasonic transducer, and rectifying an output signal obtained from the second ultrasonic
transducer; A rectifier circuit for supplying to a secondary battery, and a monitor circuit which
receives an output of the rectifier circuit and generates a frequency signal according to the signal
level and supplies the frequency signal as a monitor signal to the second ultrasonic transducer
The figure of the first ultrasonic transducer Control device for controlling the transmission axis
of the first ultrasonic transducer and the second ultrasonic transducer by controlling the first
ultrasonic transducer and the monitor signal received by the first ultrasonic transducer; And a
monitor receiving circuit for returning to the attitude control device, wherein a frequency of a
drive signal generated by the drive source is selected as a first resonant frequency band in the
ultrasonic transducer and a monitor signal generated by the monitor circuit is selected. Since the
frequency is selected in the second resonance frequency band in the ultrasonic transducer,
misalignment factors between the opposing ultrasonic transducers can be eliminated, and
efficient power transmission can be realized, and continuous It is possible to supply power by
means of a typical ultrasonic signal, and to realize more efficient power transmission.
[0026]
Further, in the power and signal transmission device using ultrasonic waves according to the
present invention, a plate having a wavelength of about 1⁄4 of the nominal frequency as a metal
matching plate joined to the transmission / reception wavefront of the second ultrasonic
transducer. Since the metal case having a thickness is used, the metal case acts as an acoustic
impedance converter (matching layer) between the biological medium and the second ultrasonic
transducer to shield the ultrasonic wave in the metal case. The effect can be reduced.
[0027]
Furthermore, in the power and signal transmission apparatus using ultrasonic waves according
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to the present invention, transmission and reception of signals other than monitor signals using
resonant frequency bands other than the first resonant frequency band in the first and second
ultrasonic transducers. Therefore, it is possible to realize signal transmission with less noise
without affecting power transmission.
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