Ultrasonic flowmeter

Details Ultrasonic flowmeter Ultrasonic flowmeter

2001-11-07

2004-06-15

Lefkowitz, Edward (Department: 2855)

Measuring and testing

Volume or rate of flow

By measuring vibrations or acoustic energy

C073S861180, C073S335110

Reexamination Certificate

active

06748811

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an ultrasonic flow meter for ultrasonically measuring a flow rate and/or a flow velocity of a gas or a fluid.
BACKGROUND ART
Conventionally, ultrasonic flow meters of this type are known in the art such as that disclosed in Japanese Laid-Open Publication No. 11-351926. As illustrated in
FIG. 44
, an ultrasonic flow meter includes measurement pipe
1
for allowing a fluid to flow from one end to the other end thereof, an upstream ultrasonic transducer
2
a
, and a downstream ultrasonic transducer
2
b
. The upstream ultrasonic transducer
2
a
and the downstream ultrasonic transducer
2
b
oppose each other via the measurement pipe
1
therebetween with a predetermined angle with respect to the center line of the measurement pipe
1
. The upstream ultrasonic transducer
2
a
and the downstream ultrasonic transducer
2
b
are housed in depressions
3
a
and
3
b
, respectively, of the measurement pipe
1
. A flow variation suppressing section
5
is further provided on an inlet side
4
of the measurement pipe
1
. A fluid entering the measurement pipe
1
is regulated by the flow variation suppressing section
5
so as to reduce the inclination of the flow line in the measurement section and/or to suppress the generation of a vortex, thereby reducing the variation in the ultrasonic reception level due to the reflection and/or refraction of the ultrasonic wave at the interface of a flow disturbance, and thus preventing the measurement precision from deteriorating.
Other conventional examples are known in the art such as that disclosed in Japanese Laid-Open Publication No. 63-26537. As illustrated in
FIG. 45
, a pair of the ultrasonic transducers
2
a
and
2
b
are provided along the wall surface of the measurement pipe
1
respectively on the upstream side and the downstream side with respect to each other. The ultrasonic transducers
2
a
and
2
b
are housed in the depressions
3
a
and
3
b
, respectively, provided in the measurement pipe
1
, with a bulk ultrasonically transmissive member
3
c
in the cavity space of each of the depressions
3
a
and
3
b
, so as to prevent a flow from entering the depressions
3
a
and
3
b
, thereby providing a high-precision flow rate measurement.
With the conventional structure as illustrated in
FIG. 44
, it is possible to reduce flow disturbances in the measurement section of the measurement pipe
1
and the depressions
3
a
and
3
b
by the flow variation suppressing section
5
, thereby reducing the deterioration of the measurement precision. However, when the flow rate through the measurement pipe
1
increases, the fluid flows into the depressions
3
a
and
3
b
to cause a vortex, thereby increasing the flow disturbance between the ultrasonic transducers
2
a
and
2
b
. In such a case, the ultrasonic wave is reflected or refracted by the increased vortex, thereby lowering the ultrasonic reception level. Thus, it is difficult to reduce the driving input for the ultrasonic transducers
2
a
and
2
b.
With the conventional structure as illustrated in
FIG. 45
in which the bulk ultrasonically transmissive member
3
c
is provided in each of the depressions
3
a
and
3
b
, a propagation loss may occur during the propagation of the ultrasonic wave through the bulk ultrasonically transmissive member
3
a
, thereby lowering the ultrasonic transmission output or the ultrasonic reception sensitivity. Moreover, because the ultrasonic wave is propagated through a solid as it passes through the bulk ultrasonically transmissive member
3
a
, the rectilinear property thereof is reduced so that it is difficult to radiate the ultrasonic wave toward the opposing ultrasonic transducer. Thus, it is difficult to reduce the power consumption of the flow meter so that it can be used as a device such as a gas meter for measuring the amount of a fuel gas for household use such as town gas or LPG which is used over an extended period of time, e.g., 10 years, with only a small electric cell capacity.
The present invention solves the above-described problems. An objective of the present invention is to reduce the generation of flow disturbances or vortices between ultrasonic transducers so as to enhance the ultrasonic reception level, thereby increasing the measurement precision and the upper limit value for the flow rate measurement, and reducing the power consumption by reducing the driving input for the ultrasonic transducers.
DISCLOSURE OF THE INVENTION
An ultrasonic flow meter of the present invention includes: a measurement flow path through which a fluid to be measured flows; ultrasonic transducers provided respectively on an upstream side and a downstream side with respect to each other along the measurement flow path; an upstream aperture hole and a downstream aperture hole, the aperture holes for exposing the ultrasonic transducers to the measurement flow path; a first influent suppressor provided in a vicinity of at least the downstream aperture hole for reducing inflow of the fluid to be measured into the aperture hole; a second influent suppressor provided on an upstream side of the measurement flow path with respect to the aperture holes for reducing the inflow of the fluid to be measured into the aperture holes; a measurement control section for measuring a propagation time of an ultrasonic wave between the ultrasonic transducers; and a calculation section for calculating a flow rate based on a signal from the measurement control section, wherein the first influent suppressor provided for the downstream aperture hole includes an aperture hole sealing section having at least one ultrasonically transmissive hole. Thus, it is possible to stabilize the flow between the ultrasonic transducers so as to enhance the ultrasonic reception level, thereby increasing the measurement precision and the upper limit value for the flow rate measurement, and to reduce the driving input for the ultrasonic transducers by the enhancement of the ultrasonic reception level and by improving the attenuation of the ultrasonic wave by providing the influent suppressor.
Another ultrasonic flow meter of the present invention includes: a measurement flow path through which a fluid to be measured flows; ultrasonic transducers provided respectively on an upstream side and a downstream side with respect to each other along the measurement flow path; an upstream aperture hole and a downstream aperture hole, the aperture holes for exposing the ultrasonic transducers to the measurement flow path; a first influent suppressor and a second influent suppressor for reducing inflow of the fluid to be measured into the aperture holes for both a forward flow and a reverse flow of the fluid to be measured; a measurement control section for measuring a propagation time of an ultrasonic wave between the ultrasonic transducers; and a calculation section for calculating a flow rate based on a signal from the measurement control section, wherein: the first influent suppressor provided for the aperture hole which is on the downstream side when the fluid flows in a forward direction is an aperture hole sealing section having at least one ultrasonically transmissive hole; and the second influent suppressor is provided on both an inlet side and an outlet side of the measurement flow path. Thus, even when the flow has a pulsation and causes a momentary reverse flow, it is possible to reduce, as in the case of a forward flow, the inflow of the fluid to be measured into the aperture hole, and to significantly reduce flow disturbances between the ultrasonic transducers, thereby increasing the measurement precision and the upper limit value for the flow rate measurement.
Another ultrasonic flow meter of the present invention includes: a measurement flow path through which a fluid to be measured flows; ultrasonic transducers provided respectively on an upstream side and a downstream side with respect to each other along the measurement flow path; aperture holes for exposing each ultrasonic transducer to the measurement flow path; a propagation pa

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