Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity
Reexamination Certificate
2000-02-22
2002-12-10
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Viscosity
C073S054270, C073S054410, C310S324000, C310S338000
Reexamination Certificate
active
06490911
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a sensor device having a piezoelectric element for measuring the viscosity, the density, the concentration, etc., of a fluid.
Up to now, in order to measure the viscosity, the density, the concentration etc., of a fluid, a sensor device using a vibrator such as a piezoelectric element has been used.
FIGS. 20A and 20B
show an example of the sensor device of this type, in which
FIG. 20A
is a perspective view of the sensor device, and
FIG. 20B
is a partially enlarged cross-sectional view of the sensor device taken along a line VI—VI. The sensor device
40
includes a base body
12
having a thin vibrating portion
14
. Onto one surface of the vibrating portion
14
is fixed a piezoelectric element
20
having a piezoelectric film
22
and a pair of electrodes
24
a
and
22
b
which are disposed to be in contact with the piezoelectric film
22
, and the other surface of the vibrating portion
14
faces a space (surrounded space)
16
defined in the interior of the base body.
Also, introduction holes
18
that communicate with the space
16
are defined in the vicinity of a tip of the sensor device
40
in such a manner that a fluid flowing into the space
16
from the introduction holes
18
is led to the vibrating portion
14
. The piezoelectric element
20
is covered with a protective cover
17
so as not to be in direct contact with the fluid
In the sensor device
40
thus structured, a fluid to be measured is allowed to flow into the space
16
from the introduction holes
18
so as to be in contact with the vibrating portion
14
. In this situation, a voltage is applied to the piezoelectric film
22
to vibrate the vibrating portion
14
, as a result of which in the case where the viscosity of the fluid is large, the amplitude of the vibrating portion
14
becomes small whereas in the case where the viscosity of the fluid is small, the amplitude of the vibrating portion
14
becomes large, thereby being capable of measuring the viscosity of the fluid by detecting a current corresponding to that amplitude. Also, in the case where the viscosity of the fluid correlates with the concentration of the fluid or the density of components in the fluid, the concentration and the density of the fluid can be measured.
As one application of the above described sensor device, there is a case in which the sensor device is built in a lead storage battery to measure a change in the density of an electrolyte. In other words, since a sulfuric acid aqueous solution is used as the electrolyte in the lead storage battery, and the viscosity of the sulfuric acid aqueous solution correlates with the density thereof, the density can be detected by the above sensor device. Also, since the density of the electrolyte changes depending on the charge and discharge of the battery, the charge and discharge state of the battery can be notified by measuring a change in the density.
FIG. 21
shows a state in which the above sensor device
40
is built in the lead storage battery. A porous sheet (separator)
34
is interposed between a pair of electrodes
32
a
and
32
b
of the battery, and the sensor device
40
is embedded in the porous sheet
34
. The sensor device
40
in this state is accommodated within a battery case, and the electrolyte is injected thereinto in such a manner that the electrolyte is infiltrated into the porous sheet
34
so as to be fully supplied between the electrodes
32
a
and
32
b,
and the electrolyte that percolates from the porous sheet
34
enters the introduction holes
18
, flows into the space
16
and is then led to the vibrating portion
14
.
By the way, in order that the electrolyte is allowed to flow into the space
16
as described above, it is necessary that an air existing in the space
16
is exhausted to the exterior simultaneously, that is, the air is replaced by the flow-in electrolyte. However, in the conventional sensor device
40
, when the sensor device
40
is built in the battery as shown in the figure, an opening end of the introduction holes
18
that communicate with the space
16
is in a state where it is in contact with the porous sheet
34
. This makes it hard to discharge the air within the space
16
, and the entrance of the electrolyte to the introduction holes
18
is irregular. As a result, there arises such a problem that it is difficult to replace the air within the space
16
with the electrolyte.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems with the prior art, and therefore an object of the present invention is to provide a sensor device which is capable of readily replacing an air by a fluid to be measured within a space.
In order to solve the above problems, according to the present invention, there is provided a sensor device which comprises: a base body having a vibrating portion; a piezoelectric element fixed onto one surface of said vibrating portion and having a piezoelectric film and a pair of electrodes which are in contact with said piezoelectric film; a space that allows a fluid to lead to the other surface of said vibrating portion; and introduction holes that communicate with said space; wherein said sensor device is in a longitudinal shape, and a recess which contains at least an opening end of the introduction holes on the surface side of the sensor device (a fluid flow-in side) in its region and extends up to the rear end portion of the sensor device is formed on the surface of the sensor device by a protrusion disposed on the surface of said sensor device so as to extend substantially continuously from the periphery of said introduction holes to the rear end portion of said sensor device (an end portion on a side far from said introduction holes).
Also, according to the present invention there is provided a sensor device which comprises: a base body having a vibrating portion; a piezoelectric element fixed onto one surface of said vibrating portion and having a piezoelectric film and a pair of electrodes which are in contact with said piezoelectric film; a space that allows a fluid to lead to the other surface of said vibrating portion; and introduction holes that communicate with said space; wherein said sensor device is in a longitudinal shape, and a plurality of introduction holes are provided and a first recess which contains at least opening ends of a part of the introduction holes on the surface side of the sensor device in its region and extends continuously up to the rear end portion of the sensor device and a second recess which contains at least opening ends of other introduction holes on the surface side of the sensor device in its region are formed by a protrusion disposed on the surface of the sensor device, the protrusion is covered with a cap member in such a manner that a cylindrical space that opens only on a side of the rear end portion of the sensor device (an end portion on a side far from the introduction hole) is formed by said protrusion, said cap member and said first recess, and said first recess and said second recess are isolated from each other.
Further, according to the present invention, there is provided a sensor device which comprises: a base body having a vibrating portion; a piezoelectric element fixed onto one surface of said vibrating portion and having a piezoelectric film and a pair of electrodes which are in contact with said piezoelectric film; a space which is defined within said base body and allows a fluid to lead to the other surface of said vibrating portion; and introduction holes that communicate with said space; wherein said sensor device is in a longitudinal shape, and said space forms a cylindrical space and has a gas exhaust hole that opens on one end portion of said cylindrical space.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4721874 (1988-01-01), Emmert
patent: 4741200 (1988-05-01), Ha
Namerikawa Masahiko
Shibata Kazuyoshi
Takeuchi Yukihisa
Larkin Daniel S.
NGK Insulators Ltd.
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