Patent Description:
As a conventional ultrasonic flowmeter, there is an ultrasonic flowmeter in which a flow path is divided into a plurality of flow paths by a partition plate to form a multi-layer flow path, and ultrasonic signals are propagated to a part of or all of layers of the multi-layer flow path to measure a flow rate (for example, see PTLs <NUM> and <NUM>).

<FIG> is a cross-sectional view of a flow path included in a conventional ultrasonic flowmeter described in PTL <NUM>, and <FIG> is an enlarged view of a main part of <FIG>.

Flow path <NUM> is divided by partition plates <NUM>. Ultrasonic sensors <NUM> are mounted on flow path <NUM> one by one upstream and downstream of the flow path, and ultrasonic sensor <NUM> includes piezoelectric element <NUM>. Ultrasonic waves reach a receiving side from a transmitting side, and a flow rate of a fluid to be measured is calculated based on a propagation time.

Ultrasonic waves generally have high straightness, and are mainly transmitted and received vertically from a vibration surface of the piezoelectric element. In PTL <NUM>, in consideration of a case where a flow velocity ratio between layers of the divided flow path is not constant, the vibration surface of the piezoelectric element has a size that spans all layers of the divided flow path so as to measure all layers.

<FIG> is a cross-sectional view of a flow path portion of a conventional ultrasonic flowmeter described in PTL <NUM>. <FIG> is a cross-sectional view taken along line 7B-7B of <FIG>.

Measurement flow path body <NUM> is held in measurement portion <NUM>, and ultrasonic sensors 204a, 204b are mounted on measurement portion <NUM> so that the ultrasonic waves are transmitted and received through opening <NUM> of measurement flow path body <NUM>. Measurement flow path body <NUM> is divided into four layers by partition plates <NUM>, and a wave transmission/reception surface mainly faces two adjacent layers in the center. In addition, it is not necessary that cross-sectional areas of the four layers are all the same.

<CIT> discloses an ultrasonic flow meter wherein measuring accuracy is improved by dividing a flow passage into a plurality of measuring layers, and by improving flow material's two-dimensionality. The flow meter comprises a first ultrasonic vibrator and a second ultrasonic vibrator arranged across the flow rate measuring part; a flow rate computing part for computing a flow rate based on a signal of the ultrasonic vibrator; and a plurality of flow layers divided by partition plates, the partition plates dividing measuring part. With the above-described configuration, it becomes possible to increase the aspect ratio of the flow path cross section in each flow path, and to increase the two-dimensionality of the flow state, resulting to perform high-accuracy measurements. Other examples of a conventional ultrasonic flowmeter are disclosed in the International patent application <CIT>.

However, as shown in PTL <NUM>, if all layers are measured, the piezoelectric element having a size that spans all layers is required, which is costly.

Furthermore, as shown in PTL <NUM>, if the opening is provided only to a part of the layers of the multi-layer flow path to perform measurement, only the layer having the opening is influenced by a flow or vortex generated in the opening, which influences the flow velocity ratio between the layers. Since how the flow velocity ratio is influenced differs not only depending on the flow rate but also depending on various factors such as the gas type and temperature, it is difficult to correct the flow velocity ratio with software, and there is a problem that errors and variations occur in the measured flow rate.

The present invention provides an ultrasonic flowmeter capable of measuring a flow rate with high accuracy by eliminating a difference in influence by an opening on the flow velocity of a measurement flow path and a non-measurement flow path to suppress variations in a flow velocity ratio while reducing costs as compared with a conventional ultrasonic flowmeter.

The present invention is defined by the independent claim. Further embodiments of the present invention are described in the dependent claims.

With this configuration, the ultrasonic flowmeter of the present disclosure can measure a flow rate with high accuracy by suppressing variations in a flow velocity ratio between a measurement flow path and a non-measurement flow path while reducing costs as compared with a conventional ultrasonic flowmeter.

Hereinafter, an exemplary embodiment will be described with reference to the drawings.

<FIG> is a configuration diagram of an ultrasonic flowmeter according to an exemplary embodiment. <FIG> is a perspective view of a flow path of the ultrasonic flowmeter according to the exemplary embodiment. <FIG> is a plan view of the flow path of the ultrasonic flowmeter according to the exemplary embodiment. <FIG> is a cross-sectional view taken along line 2C-2C of <FIG>.

An ultrasonic flowmeter of the present exemplary embodiment includes flow path <NUM>, a pair of ultrasonic sensors 2a, 2b, and flow rate calculator <NUM>.

Flow path <NUM> is formed with mounting portions 3a, 3b that mount ultrasonic sensors 2a, 2b, two partition plates <NUM> that divide flow path <NUM> into three layered flow paths <NUM>, 13a, 13b, flow path inlet <NUM>, and flow path outlet <NUM>.

The pair of ultrasonic sensors 2a, 2b transmit and receive ultrasonic waves to each other. For example, the ultrasonic waves transmitted from ultrasonic sensor 2a on a transmitting side are reflected by flow path bottom surface <NUM>, pass through propagation paths P1, P2, and reach ultrasonic sensor 2b on a receiving side. When the ultrasonic waves are transmitted from ultrasonic sensor 2b, the ultrasonic waves are reflected by flow path bottom surface <NUM> and reach ultrasonic sensor 2a. Flow rate calculator <NUM> calculates a measured flow rate based on a propagation time of the ultrasonic waves between ultrasonic sensors 2a, 2b.

Note that, as will be described later, the ultrasonic waves transmitted from ultrasonic sensors 2a, 2b propagate mainly to layered flow path <NUM>. As described above, since a flow rate of a fluid to be measured is measured in layered flow path <NUM>, hereafter, layered flow path <NUM> will be referred to as a measurement flow path, and layered flow paths 13a, 13b will be referred to as non-measurement flow paths, for convenience.

Ultrasonic sensors 2a, 2b to are mounted on mounting portions 3a, 3b without gaps, so that the fluid to be measured is prevented from flowing from other than flow path inlet <NUM> and flow path outlet <NUM>. As illustrated in <FIG>, opening 14b is formed on an upstream side of layered flow path <NUM>, which is the measurement flow path, and opening 14e is formed on a downstream side of layered flow path <NUM>, which is the measurement flow path. Openings 14a, 14c are formed on an upstream side of layered flow paths 13a, 13b, which are the non-measurement flow paths, and openings 14d, 14f are formed on a downstream side of layered flow paths 13a, 13b, which are the non-measurement flow paths.

Mounting portions 3a, 3b need to mount ultrasonic sensors 2a, 2b at an angle with respect to flow path <NUM> so that the ultrasonic waves can be transmitted and received between the pair of ultrasonic sensors 2a, 2b. Therefore, space 9a exists between ultrasonic sensor 2a and openings 14a to 14c, and space 9b exists between ultrasonic sensor 2b and openings 14d to 14f.

<FIG> is a perspective view of the ultrasonic sensor of the ultrasonic flowmeter according to the exemplary embodiment. <FIG> is a cross-sectional view taken along line 3B-3B of <FIG>.

As illustrated in <FIG>, in ultrasonic sensors 2a, 2b, acoustic matching layer <NUM> is adhered to one surface of metal support <NUM> with an adhesive, and piezoelectric element <NUM> is adhered to the other surface of support <NUM> with a conductive adhesive. Lead wire 26a is electrically connected to an electrode of piezoelectric element <NUM> that is not adhered to support <NUM>, and lead wire 26b is electrically connected to support <NUM>, and is electrically connected, via support <NUM>, to an electrode of piezoelectric element <NUM> that is adhered to support <NUM>.

Furthermore, a portion other than acoustic matching layer <NUM> is covered with insulating vibration damping member <NUM>, but support <NUM> has two facing portions extending outward from insulating vibration damping member <NUM>. On the portions of support <NUM> extending outward from insulating vibration damping member <NUM>, mounted portions <NUM> each formed in an arc shape are formed, and mounted portions <NUM> are fixed to mounting portion 3a, 3b. In addition, ultrasonic sensors 2a, 2b are connected to flow rate calculator <NUM> via lead wires 26a, 26b.

Furthermore, a size of piezoelectric element <NUM> is such that length W of a side in a direction perpendicular to partition plates <NUM> illustrated in <FIG> is equivalent to a width of layered flow path <NUM>, which is the measurement flow path, in the direction perpendicular to partition plates <NUM>, that is, the width of layered flow path <NUM>, which is the measurement flow path, and a portion having acoustic matching layer <NUM> faces opening 14b, 14e of layered flow path <NUM>, which is the measurement flow path. Therefore, the ultrasonic waves radiated from ultrasonic sensors 2a, 2b mainly propagate only in layered flow path <NUM>, which is the measurement flow path. As a result, the size of piezoelectric element <NUM> can be reduced and costs required for ultrasonic sensors 2a, 2b can be reduced as compared with a case of measuring all layers.

Flow path <NUM> has a rectangular cross section, and layered flow path <NUM>, which is the measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths, have rectangular cross-sectional shapes having the same dimensions. Openings 14a, 14b, 14c and openings 14d, 14e, 14f are rectangles having the same dimensions, and formed so that sides in the direction perpendicular to partition plates <NUM> are aligned on the same line, as illustrated in <FIG>.

Note that, since the flow velocity is not the same between layered flow path <NUM>, which is the central measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths, as in flow path <NUM> illustrated in <FIG>, cross-sectional areas of layered flow path <NUM>, which is the measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths, and sizes of openings 14a, 14b, 14c, 14d, 14e, 14f may be adjusted so that a change in the flow velocity ratio is a target value. Furthermore, each of shapes of openings 14a to 14f may be a shape other than a rectangle, for example, an uneven shape may be provided on a side, or an edge or a side may be formed in an arc shape.

Around openings 14a to 14f, flows and vortices are generated and influence pressure losses of layered flow path <NUM>, which is the measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths. Therefore, when openings 14b, 14e are formed only in layered flow path <NUM>, which is the measurement flow path, different flows and vortices are generated around the openings depending on the flow rate, temperature, gas type, or the like, and the flowability of the fluid to be measured in layered flow path <NUM>, which is the measurement flow path, is influenced, which causes a change in the flow velocity ratio that cannot be corrected.

In the present exemplary embodiment, since openings 14a to 14f are formed in all layers, the shape of each layered flow path is the same, and flow conditions can be the same. Thus, even if the flow rate, temperature, gas type, or the like changes, the flow velocity ratio does not easily vary. As a result, it is possible to measure the flow rate with higher accuracy.

Furthermore, as illustrated in <FIG>, flow path inlet <NUM> may be provided with turbulence device <NUM> including two rod-shaped portions 15a, 15b connecting two opposite sides of flow path inlet <NUM> to make the fluid to be measured turbulent. Turbulence device <NUM> is mounted on flow path inlet <NUM> and makes the fluid to be measured flowing into flow path inlet <NUM> turbulent. Furthermore, turbulence device <NUM> may be integrally molded with flow path inlet <NUM>, and may have a mesh structure. When the same flow rate flows through layered flow path <NUM>, which is the measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths, the flows and vortices generated around the openings 14a to 14f are equal between layered flow path <NUM>, which is the measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths, even if the flow rate, temperature, gas type, or the like changes. When the fluid to be measured is turbulent at flow path inlet <NUM>, the fluid to be measured flows evenly to layered flow path <NUM>, which is the measurement flow path, and layered flow paths 13a, 13b, which are the non-measurement flow paths, and as a result, the variations in the flow velocity ratio can be further suppressed, and the flow rate can be measured with higher accuracy.

As described above, an ultrasonic flowmeter in a first disclosure includes a flow path that has a rectangular cross section and through which a fluid to be measured flows, a partition plate that divides the flow path into a plurality of layers to form layered flow paths, and a pair of ultrasonic sensors that are arranged upstream and downstream of a surface forming the flow path and transmitting and receiving ultrasonic signals. Furthermore, the ultrasonic flowmeter includes a flow rate measurer that detects a flow rate of the fluid to be measured based on a propagation time from when the ultrasonic signals are transmitted from one of the pair of ultrasonic sensors until when the ultrasonic signals are received by another one of the pair of ultrasonic sensors after propagating through the fluid to be measured, mounting portions that mount the ultrasonic sensors on the flow path, and openings that are provided directly below the mounting portions and through which ultrasonic waves pass. Furthermore, each of the openings has a size facing a plurality of layers of the layered flow paths, and the ultrasonic sensors mainly propagate the ultrasonic waves only to some layer of the layered flow paths.

With this configuration, it is possible to measure the flow rate with high accuracy by eliminating a difference in influence by an opening on the flow velocity of a measurement flow path and a non-measurement flow path to suppress variations in a flow velocity ratio while costs are reduced as compared with a conventional ultrasonic flowmeter.

In the ultrasonic flowmeter in a second disclosure, particularly in the first disclosure, the number of the layered flow paths may be an odd number, and the ultrasonic sensors may mainly propagate the ultrasonic waves to a central layer of the layered flow paths.

In the ultrasonic flowmeter in a third disclosure, particularly in the first disclosure, each of the ultrasonic sensors may include a metal support and a piezoelectric element bonded to the metal support, and a width of a vibration surface of the piezoelectric element is substantially same as a width of the layer that propagates the ultrasonic waves.

In the ultrasonic flowmeter in a fourth disclosure, particularly in the second disclosure, each of the ultrasonic sensors may include a metal support and a piezoelectric element bonded to the metal support, and a width of a vibration surface of the piezoelectric element is substantially same as a width of the layer that propagates the ultrasonic waves.

In the ultrasonic flowmeter in a fifth disclosure, particularly in any one of the first to fourth disclosures, the flow path may be provided with a turbulence device that makes the fluid to be measured turbulent at an inlet portion through which the fluid to be measured passes.

With this configuration, the flow velocity ratio between the measurement flow path and the non-measurement flow path is uniform, so that it is possible to measure the flow rate with high accuracy while the costs are reduced as compared with the conventional ultrasonic flowmeter.

Claim 1:
An ultrasonic flowmeter comprising:
a flow path (<NUM>) that has a rectangular cross section and through which a fluid to be measured flows;
a partition plate (<NUM>) that divides the flow path (<NUM>) into a plurality of layers to form layered flow paths (<NUM>, 13a, 13b);
a pair of ultrasonic sensors (2a, 2b) that are arranged upstream and downstream of a surface (<NUM>) forming the flow path (<NUM>) and transmitting and receiving ultrasonic signals;
a flow rate calculator (<NUM>) configured to detect a flow rate of the fluid to be measured based on a propagation time from when the ultrasonic signals are transmitted from one of the pair of ultrasonic sensors (2a, 2b) until when the ultrasonic signals are received by another one of the pair of ultrasonic sensors (2a, 2b) after propagating through the fluid to be measured;
mounting portions (3a, 3b) that mount the ultrasonic sensors (2a, 2b) on the flow path (<NUM>); and
openings that are provided directly below the mounting portions (3a, 3b) and through which ultrasonic waves pass,
each of the openings is open to face a plurality of layers of the layered flow paths (<NUM>, 13a, 13b), characterised in that
the plurality of layered flow paths (<NUM>, 13a, 13b) includes a measurement flow path (<NUM>) for detecting the flow rate of the measured fluid and non-measurement flow paths (13a, 13b) other than the measurement flow path (<NUM>),
each of the openings comprises a smaller opening (14b, 14e) facing the measurement flow path (<NUM>) and smaller openings (14a, 14c, 14d, 14f) each facing a corresponding one of the non-measurement flow paths (13a, 13b) and that
the ultrasonic sensors (2a, 2b) are configured to propagate the ultrasonic waves mainly to the measurement flow path (<NUM>).