Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-12-26
2004-06-01
Budd, Mark (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S340000, C310S344000
Reexamination Certificate
active
06744178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pulse detection device using a piezoelectric element and a method of manufacturing the pulse detection device.
2. Description of the Related Art
A pulse in a living body contains important information for diagnosis of a sickness. In recent years, studies have been conducted on application of a system in which a portable pulse detection device is worn about an arm of a patient at a medical office of a medical institution, e.g., a hospital, and data on a pulse detected from the patient, which is transmitted from the portable pulse detection device, is received on the hospital side to grasp the condition of the patient. Use of a piezoelectric element in a pulse detection device is advantageous in terms of the effect of reducing the device in size and in weight. The development of pulse detection devices, including those suitably applicable to the above-described system, is being advanced.
FIGS. 19 and 20
show a conventional pulse detecting device
100
using a piezoelectric element. As shown in
FIG. 19
, the pulse detection device
100
has two piezoelectric elements
110
and
120
fixed by being embedded in a resin
130
(or gel).
FIG. 20
is a side view of the pulse detection device
100
shown in FIG.
20
. The piezoelectric elements
110
and
120
are fixed while being spaced apart by a distance g. Further, the fixing step is controlled such that the thickness t between the piezoelectric elements
110
and
120
and a surface
150
to be brought into contact with a skin is set to a predetermined value.
In each of the piezoelectric elements
110
and
120
, metal electrodes (not shown) are formed on two surfaces opposite from each other in the direction of thickness. Probes (terminals, leads, or the like) (not shown) for application of a drive voltage are connected to both the electrodes of the piezoelectric element
110
while probes (not shown) for outputting a voltage signal are connected to the upper and lower electrodes of the piezoelectric element
120
.
This pulse detection device
110
is used to detect a pulse of a patient at the time of medical examination in a hospital. More specifically, when a drive voltage is applied to both the electrodes of the piezoelectric element
110
, the piezoelectric element
110
is excited to generate ultrasound, which is transmitted into the living body through the resin
130
. The ultrasound transmitted into the living body is reflected by a bloodstream in the living body. The reflected ultrasound is received by the piezoelectric element
120
through the resin
130
.
At this time, a difference is caused between the frequency of the ultrasound transmitted by the piezoelectric element
110
and the frequency of the ultrasound received by the piezoelectric element
120
by the Doppler effect of the bloodstream. Since the speed of the bloodstream changes in synchronization with pulsation, a pulse in the living body is detected from changes in the frequency of the ultrasound.
In the above-described pulse detection device using the piezoelectric elements, there is a need to precisely place the ultrasound transmitting piezoelectric element
110
and the ultrasound receiving piezoelectric element
120
for the purpose of improving the ultrasound receiving sensitivity. The pulse detection sensitivity changes largely with respect to the spacing g between the two piezoelectric elements
110
and
120
. An optimum range of this spacing is from 0.1 to 0.5 mm. The sensitivity also changes largely with respect to the thickness t of the block of the resin
130
. For example, if the piezoelectric elements
110
and
120
are driven at 9.0 MHz, an optimum value of the thickness t is about 140 &mgr;m.
However, it is difficult to precisely place the piezoelectric elements
110
and
120
of the above-described pulse detection device
100
, because the manufacturing process of the pulse detection device
100
uses the step of pouring the resin
130
after placing the two piezoelectric elements
110
and
120
at predetermined positions and there is a possibility of occurrence of changes in the positions and the angles of the placed piezoelectric elements when the resin is poured.
Therefore, there is a possibility of the conventional pulse detection devices
100
being manufactured with considerable variation in quality. In the step of forming the piezoelectric element by pouring the resin
130
, it is difficult to control the thickness h of the resin
130
in accordance with the desired thickness, so that there is a possibility of occurrence of considerable variation in sensitivity.
Further, because of the need to apply a voltage between the two surfaces opposite in the thickness direction of each of the piezoelectric elements
110
and
120
embedded in the resin
130
, the step of attaching thin wires or the like to the two surfaces of the piezoelectric elements
110
and
120
is required before the step of pouring the resin
130
. Therefore, it is difficult to suitably place the piezoelectric elements
110
and
120
, and the number of steps is increased. Thus, it is difficult to manufacture the pulse detection device.
SUMMARY OF THE INVENTION
In view of the above-described problems, an object of the present invention is to provide a pulse detection device in which an ultrasound transmitting piezoelectric element and an ultrasound receiving piezoelectric element are precisely placed to effectively limit variation in quality, and a method of manufacturing the pulse detection device.
Another object of the present invention is to provide a pulse detection device which is formed by using a base plate having a prescribed thickness to have an optimum pulse detection sensitivity, instead of resin, and which can be manufactured with improved reproducibility.
Still another object of the present invention is to provide a pulse detection device in which wiring for application of a voltage to piezoelectric elements is provided on a supporting base plate to easily manufacture the pulse detection device.
A further object of the present invention is to provide a pulse detection device having an improved pulse detection sensitivity.
To achieve the above-described objects, according to an aspect of the present invention, there is provided a pulse detection device comprising a transmitting piezoelectric element (e.g., transmitting piezoelectric element
41
shown in
FIG. 4
) excited in accordance with a drive signal to generate ultrasound and to transmit the ultrasound into a living body, a receiving piezoelectric element (e.g., receiving piezoelectric element
42
shown in
FIG. 4
) for receiving reflected waves of the ultrasound transmitted into the living body and reflected by a bloodstream in the living body, and for converting the reflected waves into an electrical signal, a detection section (e.g., processing computation section
31
shown in
FIG. 3
) for detecting a pulse from the ultrasound generated by the transmitting piezoelectric element and the reflected waves received by the receiving piezoelectric element, and a transmitting/receiving base plate (e.g., transmitting/receiving base plate
43
) having the transmitting piezoelectric element and the receiving piezoelectric element placed and fixed on its one surface, the other surface of the transmitting/receiving base plate being brought into contact with the living body.
In the thus-constructed pulse detection device, both the transmitting piezoelectric element and the receiving piezoelectric element are placed and fixed on the transmitting/receiving base plate. Therefore, these piezoelectric elements can be placed with accuracy in accordance with a design.
There is no functional problem since the ultrasound generated by the transmitting piezoelectric element is transmitted into the living body through the transmitting/receiving base plate, and the waves reflected by the bloodstream in the living body propagate from the living body to the receiving piezoelectric element through the transmitting/receiving base
Muramatsu Hiroyuki
Odagiri Hiroshi
Shinogi Masataka
Adams & Wilks
Budd Mark
Seiko Instruments Inc.
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