Straight type flowmeter sensor

Abstract

The present invention addresses the problem of providing a straight type flowmeter sensor which can perform measurement while maintaining stable sensitivity in a wide temperature range including a high temperature range. A straight type flowmeter sensor 11 according to the present invention comprises a pair of shoes 61, a coupling material layer 81, an inner case 22, an outer case 21, a pressing plate 74, a screw member 73, and a coil spring 82. The pressing plate 74 is disposed between one shoe 61 and an inner wall surface 51a of the inner case 22 such that a plate front surface thereof is in surface contact with a first pressed portion P1 of the shoe 61. A screw tip of the screw member 73 abuts against a plate rear surface of the pressing plate 74, and, by being screwed, the screw member 73 presses the first pressed portion P1 toward the center of a pipe 1 via the pressing plate 74. A first end t1 of the coil spring 82 abuts against a second pressed portion P2 of the shoe 61, and the coil spring 82 presses the second pressed portion P2 toward the center of the pipe 2. Selected drawing: fig. 4

Description

Straight type flow meter sensor

[0001] The present invention relates to a straight-type flow meter sensor, and more particularly to a straight-type flow meter sensor having a plurality of legs that sandwich a pipe from both sides.

[0002] Various ultrasonic flowmeters that measure the flow rate of liquids have been proposed as measuring devices that use ultrasonic waves. In these ultrasonic flowmeters, a flow rate measurement pipe is provided in the middle of a pipe through which the liquid flows, and ultrasonic sensors are installed at upstream and downstream positions of the flow rate measurement pipe. These ultrasonic sensors transmit and receive ultrasonic waves, and the flow rate of the liquid is calculated based on the time difference between the propagation time of the ultrasonic waves propagating from the upstream side to the downstream side and the propagation time of the ultrasonic waves propagating from the downstream side to the upstream side.

[0003] Various types of ultrasonic flow meters have been proposed in the past, and for example, clamp-on ultrasonic flow meter sensors that can be attached by clamping them onto straight piping are well known (see, for example, Patent Documents 1 and 2).

[0004] Straight-type flowmeter sensors that are not clamp-on have also been proposed (see, for example, Patent Documents 3 and 4). These straight-type flowmeter sensors have a double-structure case (an inner case and an outer case that houses the inner case). A resin pipe is installed so as to pass through the case. A pair of shoes are housed inside the inner case, offset in the axial direction of the pipe. The pair of shoes has a main body that supports an ultrasonic transducer and multiple legs that sandwich the pipe from both sides.

[0005] Patent No. 5927394 Patent No. 6789766 Patent No. 7074390 Patent No. 7233795

[0006] The above-mentioned straight-type flowmeter sensor of the leg clamping type is not only used for measurements in an environment where a fluid at room temperature flows through a pipe, but is also sometimes used for measurements in an environment where a fluid at high temperature flows through a pipe.

[0007] However, even if a predetermined sensitivity is achieved during the initial measurement of a high-temperature fluid, the contact between the shoe and the pipe deteriorates when the temperature of the fluid flowing through the pipe (i.e., the temperature of the pipe) drops to room temperature. Once this deterioration in contact occurs, the sensitivity remains reduced regardless of whether the measurement is of a room-temperature fluid or a high-temperature fluid. If the sensitivity reduction is significant, the measurement may become impossible. Therefore, the conventional straight-type flowmeter sensor with clamped legs described above could not stably measure a wide temperature range, including high temperatures, without a decrease in sensitivity.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a straight-type flow meter sensor that can maintain sensitivity and perform stable measurements over a wide temperature range, including high temperatures.

[0009] In order to solve the above problems, the invention described in claim 1 is a straight type flowmeter sensor including a pair of shoes each having a main body portion arranged offset in the axial direction of a straight pipe through which a fluid flows and supporting an ultrasonic vibrator on an inclined surface on the front side, a plurality of legs protruding from a bottom surface of the shoes so as to sandwich the pipe from both sides, a coupling material layer arranged in contact with the outer peripheral surface of the pipe and the bottom surface of the shoes, an inner case that houses and positions the pair of shoes, and an outer case that houses the inner case, wherein the front surface of a plate is in contact with the front surface of the plate between the shoes and the inner wall surface of the inner case. The gist of the straight-type flow meter sensor is that it comprises: a pressure plate arranged in surface contact with a first pressure target portion of the shoe; a screw member provided within the inner case with its screw tip abutting the back surface of the pressure plate and screwed in to apply a pressure force that presses the first pressure target portion toward the center of the piping via the pressure plate; and a coil spring provided within the inner case with its first end abutting a second pressure target portion of the shoe and constantly compressed, and applying a biasing force that presses the second pressure target portion toward the center of the piping.

[0010] According to the first aspect of the present invention, a pressure corresponding to the degree of threading of the screw member acts to press the first pressure-receiving portion of the shoe toward the center of the pipe via the pressure plate, and the shoe is assembled in a state of intimate contact with the pipe. Furthermore, the coil spring is provided in the inner case in a constantly compressed state, and its biasing force constantly presses the second pressure-receiving portion of the shoe toward the center of the pipe. Therefore, even if the fluid temperature drops from high temperature to room temperature and the pressure acting via the pressure plate decreases or disappears, the shoe is pressed by the coil spring, maintaining intimate contact between the shoe and the pipe. Therefore, sensitivity is maintained over a wide temperature range, including high temperatures, enabling stable measurement without becoming impossible.

[0011] The invention described in claim 2 is characterized in that, in claim 1, the coil spring is provided as a pair at positions spaced apart in the front-rear direction of the shoe.

[0012] Therefore, according to the invention described in claim 2, it is possible to apply a pressing force to the shoe more evenly than when a coil spring is provided in only one location. Furthermore, when the pair of coil springs are spaced apart in the front-to-rear direction, the shoe is positioned stably, making it less likely to tilt or become misaligned.

[0013] The invention described in claim 3 is based on claim 2, and is characterized in that a front tongue is integrally formed on the lower part of the front side of the main body, and a rear tongue is integrally formed on the lower part of the rear side of the main body, the first ends of the pair of coil springs are provided within the inner case in a state of abutting against the upper surfaces of the front tongue and the rear tongue, which are the second pressed part, respectively, and the front surface of the pressure plate is arranged in face contact with the top surface of the shoe, which is the first pressed part.

[0014] Therefore, according to the invention described in claim 3, since it is easy to secure a space for accommodating a pair of coil springs in the front and rear regions of the shoe, assembling the pair of coil springs becomes easy. Also, since the upper surfaces of the front and rear tongue pieces have second pressed portions of the required size, the first end can be placed in stable contact with the upper surfaces. Furthermore, since the top surface of the shoe has a first pressed portion of the required size, the front surface of the pressure plate can be placed in stable surface contact with the top surface.

[0015] The invention described in claim 4 is characterized in that, in claim 3, the second ends of the pair of coil springs are arranged within the inner case in a state in which they are each in contact with the front surface of the pressing plate.

[0016] Therefore, according to the invention described in claim 4, the second end side of the pair of coil springs receives resistance from the inner wall surface of the inner case, thereby generating a spring force that presses against the shoe on the opposite side, the first end side.

[0017] The invention described in claim 5 is characterized in that, in claim 4, the upper surface of the front tongue piece and the upper surface of the rear tongue piece are each provided with a first locking portion for positioning the first ends of a pair of the coil springs.

[0018] Therefore, according to the fifth aspect of the present invention, the first ends of the pair of coil springs are engaged with the first engaging portions, thereby positioning the first ends at suitable positions on the upper surfaces of the front and rear tongue pieces, respectively. This allows the biasing force of the pair of coil springs to be reliably applied to the shoe. Furthermore, the pair of coil springs can be easily assembled.

[0019] The invention described in claim 6 is based on claim 5, and is characterized in that a second locking portion is provided on the front surface of the pressing plate for positioning the second ends of the pair of coil springs.

[0020] Therefore, according to the sixth aspect of the present invention, the second ends of the pair of coil springs are locked in the second locking portions, thereby positioning the second ends at suitable positions on the pressure plate, thereby ensuring that the biasing force of the pair of coil springs is applied to the shoe.

[0021] The invention described in claim 7 is characterized in that, in claim 3, the second ends of the pair of coil springs are arranged within the inner case in a state in which they are each in contact with the inner wall surface of the inner case.

[0022] Therefore, according to the seventh aspect of the present invention, the second ends of the pair of coil springs receive resistance from the inner wall surface of the inner case, so that a biasing force that presses the shoe can be generated on the opposite side, the first ends. Furthermore, with this configuration, the pair of coil springs do not press the pressure plate, so the biasing force can be set independently of the pressing force via the pressure plate.

[0023] The invention described in claim 8 is based on claim 3, and is characterized in that insertion portions into which a pair of the coil springs can be inserted are formed at both longitudinal ends of the pressure plate, and the second ends of the pair of the coil springs are inserted into the insertion portions and are provided within the inner case in a state in which they are each in contact with the inner wall surface of the inner case.

[0024] Therefore, according to the invention described in claim 8, the second ends of the pair of coil springs are inserted into the insertion portions of the pressure plate, so that the pair of coil springs can be arranged inside the inner case while avoiding interference with the pressure plate.

[0025] The invention described in claim 9 is characterized in that, in claim 8, the upper surface of the front tongue piece and the upper surface of the rear tongue piece are each provided with a first locking portion for positioning the first ends of a pair of the coil springs.

[0026] Therefore, according to the ninth aspect of the present invention, by engaging the first ends of the pair of coil springs with the first engaging portions, the first ends are positioned at suitable positions on the upper surfaces of the front and rear tongue pieces, respectively. This allows the biasing force of the pair of coil springs to be reliably applied to the shoe. Furthermore, the pair of coil springs can be easily assembled.

[0027] The invention described in claim 10 is characterized in that, in any one of claims 1 to 9, the multiple legs are a total of four, consisting of a pair of front legs and a pair of rear legs, and when the axial direction of the piping is used as a reference, the multiple legs are arranged in a position relatively close to the screw member, and the pair of coil springs are arranged in a position relatively far from the screw member.

[0028] Therefore, according to the invention described in claim 10, the pair of coil springs are located farther from the screw member than the pair of front legs and the pair of rear legs, making it easier to apply a uniform pressure force to the shoe, which makes it easier to stably position the shoe and makes it less likely for the shoe to tilt or become misaligned.

[0029] The invention described in claim 11 is characterized in that, in any one of claims 1 to 9, the piping is made of a resin material having a heat resistance of 200°C, and the flow meter sensor is used in an environment in which the fluid flows through the piping at a temperature of 90°C or higher.

[0030] As described above in detail, according to the inventions described in claims 1 to 11, it is possible to provide a straight-type flow meter sensor that can perform measurements while maintaining stable sensitivity over a wide temperature range, including high temperatures.

[0031] 1 is a perspective view showing a straight-type flow meter sensor according to an embodiment of the present invention; 2 is a perspective view of the straight-type flow meter sensor according to the first embodiment, viewed from a different angle; 3 is an exploded perspective view of the straight-type flow meter sensor according to the first embodiment; 4 is a plan view showing the straight-type flow meter sensor according to the first embodiment with the upper case split piece and the top cover member removed; 5 is an exploded perspective view for explaining the arrangement of each component housed in the inner case; 6 is a perspective view for explaining the arrangement of each component housed in the inner case; 7 is a cross-sectional view showing a pair of shoes, a coupling material layer, and piping for explaining problems of a conventional straight-type flow meter sensor; 8 is a plan view showing a pair of shoes, a coupling material layer, piping, etc. for explaining problems of a conventional straight-type flow meter sensor; and 9 is a plan view showing a pair of shoes, a coupling material layer, piping, etc. for explaining advantages of the straight-type flow meter sensor according to the present embodiment. 10A and 10B are plan views showing a state in which an upper case divided piece and an upper cover member are removed in a straight-type flowmeter sensor according to a second embodiment, a plan view showing a pressing plate of the straight-type flowmeter sensor according to the second embodiment, and a plan view showing a state in which an upper case divided piece and an upper cover member are removed in a straight-type flowmeter sensor according to a third embodiment.

[0032] First Embodiment A straight-type flow meter sensor 11 according to one embodiment of the present invention will now be described in detail with reference to FIGS.

[0033] 1 to 7, the straight type flow meter sensor 11 of this embodiment includes a pipe 1, an inner case 22, an outer case 21, an ultrasonic vibrator 64, a shoe 61, and a coupling material layer 81. The straight type flow meter sensor 11 is used not only in an environment where a low-temperature liquid of, for example, 0° C. or higher but lower than 90° C. (particularly, a room-temperature liquid of about 20° C.±15° C.) flows through the pipe 1, but also in an environment where a high-temperature liquid of 90° C. or higher (particularly, a high-temperature liquid of 90° C. or higher but lower than 200° C.) flows.

[0034] The pipe 1 is a resin tube member with a circular cross section, at least partially straight. A fluid whose flow rate is to be measured flows through the pipe 1. In this embodiment, a high-temperature liquid, particularly a liquid with a temperature of approximately 90°C to 200°C, flows through the pipe 1. The pipe 1 is made of a thermoplastic resin material that is heat-resistant at least in the temperature range of 90°C to 200°C. Specifically, in this embodiment, a fluororesin, such as PFA (perfluoroalkoxyalkane), is selected as the resin material. This type of fluororesin is preferable because it has chemical resistance that prevents deterioration or corrosion even when exposed to high temperatures, strong acids, or strong alkalis. A sheet-like coupling material layer 81 is disposed on the outer surface of the pipe 1 at the shoe installation location. The coupling material layer 81 is disposed in contact with the outer surface of the pipe 1 and the shoe bottom surface 65 (described later). In this embodiment, the coupling material layer 81 is a rectangular sheet material with a thickness of approximately 0.5 mm to 1 mm, and is made of an elastic material that is heat-resistant at least in the temperature range of 90°C to 200°C. Specifically, in this embodiment, a fluororubber having high heat resistance (for example, FKM (propylene hexafluoride-vinylidene fluoride copolymer, etc.)) is selected as the elastic material.

[0035] A pair of shoes (also referred to as acoustic prisms) 61 support ultrasonic vibrators 64 capable of transmitting and receiving ultrasonic waves and also propagate ultrasonic waves from the ultrasonic vibrators 64 toward the fluid in the pipe 1 (see FIGS. 5 and 6 ). The pair of shoes 61 are arranged in a substantially opposing positional relationship on the outer circumferential surface of the pipe 1 to form the transmission-type straight flowmeter sensor 11. The pair of shoes 61 support the ultrasonic vibrators 64 in a manner that allows ultrasonic waves to be incident obliquely onto the straight pipe 1 through which the fluid flows, and are arranged offset in the axial direction D1 of the pipe 1. The pair of shoes 61 are made of a resin material that is heat-resistant at least in a temperature range of 90°C to 200°C. Specifically, in this embodiment, PES (polyethersulfone) is selected as the resin material.

[0036] As shown in Figures 5 and 6, the pair of shoes 61 in this embodiment are the same size and shape. More specifically, each shoe 61 has a block shape that is elongated in the front-to-rear direction (the left-to-right direction in Figures 5 and 6) and is formed, for example, from a resin material that can efficiently transmit ultrasonic waves. The front side of the main body 62 that constitutes the shoe 61 is formed with a front inclined surface 63 that forms a predetermined angle (approximately 60° in this embodiment) with respect to the shoe bottom surface 65. A disc-shaped ultrasonic vibrator 64 made of a sintered ceramic is adhesively supported on the front inclined surface 63. In this embodiment, the ultrasonic vibrator 64 generates ultrasonic waves of, for example, 2 MHz, but it is also possible to use one that generates ultrasonic waves of other frequencies. Furthermore, the ceramic sintered body that constitutes the ultrasonic vibrator 64, which is a piezoelectric element, is selected from a porous sintered body of alkali niobate piezoelectric ceramics, such as potassium sodium niobate, but it is also possible to use other ceramic sintered bodies. The ultrasonic wave emitting surfaces of these ultrasonic vibrators 64 are arranged in a state inclined toward the straight pipe 1.

[0037] A front tongue 68 is integrally formed on the lower part of the front side of the main body 62. The front tongue 68 is a rectangular flat plate and extends toward the front side of the main body 62. A rear tongue 69 is integrally formed on the lower part of the rear side of the main body 62. The rear tongue 69 is a rectangular flat plate and extends toward the rear side of the main body 62. The lengths of the front tongue 68 and the rear tongue 69 are not particularly limited, but are set to, for example, about 1 / 6 to 1 / 3 of the length of the main body 62. Furthermore, the thicknesses of the front tongue 68 and the rear tongue 69 are not particularly limited, but are set to, for example, about 1 / 6 to 1 / 3 of the thickness of the main body 62.

[0038] A plurality of legs 66 are integrally formed on a shoe bottom surface 65 (i.e., the surface facing the pipe 1) of the main body 62 constituting each shoe 61. In this embodiment, the shoe bottom surface 65 is flat, but may be concavely curved to fit the shape of the outer peripheral surface of the pipe 1. These legs 66 extend in the same direction and hold and secure the pipe 1 by sandwiching it from both sides. In this embodiment, there are four legs 66 (two pairs on the left and right, a pair of front legs 66a and a pair of rear legs 66b), each of which has the same shape and size. Note that the number of legs 66 is not limited to four and may be three or less, or five or more. Each leg 66 is formed to be slightly shorter than the diameter of the pipe 1. The pair of front legs 66a and the pair of rear legs 66b are disposed at a distance greater than the width of the legs 66. The reason for this is that the leg 66 belonging to one shoe 61 can be arranged with ample space in the region between the front leg 66a and rear leg 66b belonging to the other shoe 61.

[0039] The pair of shoes 61 are arranged with their legs 66 offset from each other in the axial direction D1 of the pipe 1, and are arranged so as not to come into contact with the legs 66 of different shoes 61 (i.e., the mating shoe 61). The reason for avoiding contact between the legs 66 in this way is to prevent the ultrasonic vibrations emitted by the ultrasonic vibrator 64 belonging to one shoe 61 from being directly transmitted to the other shoe 61. The multiple legs 66 are also arranged so as to avoid the center of the ultrasonic beam emitted from the ultrasonic vibrator 64. This is to reduce the loss of ultrasonic vibrations caused by the ultrasonic beam being transmitted to the legs 66, and to avoid a decrease in measurement accuracy and sensitivity.

[0040] As shown in Figures 3 and 4, the inner case 22 is a rectangular box-shaped container that houses a pair of shoes 61 and serves to hold and fix them in the correct position relative to the pipe 1. The inner case 22 may also serve as an electromagnetic shield to protect the ultrasonic vibrator 64 housed therein from magnetic influences. The material for the inner case 22 is not particularly limited, and examples of materials that can be used include PPS and fluororesin. However, when the inner case 22 is to function as an electromagnetic shield, it is preferable to use a metal material with magnetic shielding properties. The inner case 22 is composed of an upper cover member 51 and a lower cover member 52. A substantially U-shaped notch 54 is formed in the center of each end surface of the upper cover member 51 and the center of each end surface of the lower cover member 52. When the lower cover member 52 is placed over the upper cover member 51, these notches 54 form a circular pipe insertion hole.

[0041] A pair of shoes 61 are housed in the internal space of the inner case 22, sandwiching and fixing the pipe 1 from both sides. In this state, the coupling material layer 81 is interposed between the outer peripheral surface of the pipe 1 and the shoe bottom surface 65 of the shoe 61, and is arranged in contact with them. Both shoe side surfaces of the shoe 61 are in a state of almost contacting the inner wall surface of the inner case 22.

[0042] 1 to 4, the outer case 21 is a rectangular box-shaped container that is slightly larger than the inner case 22, and serves to house and protect the inner case 22, which is a sensor module. The material from which the outer case 21 is made is not particularly limited, but examples include PPS and fluororesin. The outer case 21 is composed of a lower case segment 31 (first case segment) and an upper case segment 41 (second case segment).

[0043] The lower case segment 31 has an opening on its entire upper surface, and the edge of the opening forms the dividing plane P1 of the outer case 21. The lower case segment 31 has a first side wall 31a on only one side. A pipe insertion portion 33 having a first insertion hole 32 protrudes from the center of the outer surface of the first side wall 31a. The first insertion hole 32 receives the first end portion T1 of the pipe 1. A connector portion 34 for cable connection protrudes from the outer surface of the first side wall 31a, next to the pipe insertion portion 33. As shown in FIG. 3 and other figures, a rectangular frame-shaped wall portion 36 is provided in the center of the inner bottom surface of the lower case segment 31. The inner case 22 is fitted into a recess formed by the wall portion 36, thereby positioning and fixing the inner case 22 to the lower case segment 31. Cylindrical bosses 35 are provided at the four corners of the inner bottom surface of the lower case segment 31. These bosses 35 are used to fasten the upper case segment 41 with screws. Each boss 35 is formed with a female thread.

[0044] On the other hand, the upper case segment 41 has an opening on its entire underside, with the edge of the opening forming the dividing plane P1 of the outer case 21. The upper case segment 41 has a second side wall 41a on only one side. The second side wall 41a is positioned opposite the first side wall 31a of the outer case 21. A pipe insertion portion 43 having a second insertion hole 42 protrudes from the center of the outer surface of the second side wall 41a, and the second end portion T2 of the pipe 1 is inserted through the second insertion hole 42. The upper case segment 41 differs from the lower case segment 31 in that it does not have the connector portion 34, boss portion 35, or wall portion 36. Furthermore, screw insertion portions 45 are formed at the four corners of the bottom surface of the upper case segment 41, facing the boss portion 35 of the lower case segment 31. A screw 71 is inserted into each screw insertion portion 45, and a screw cap 72 is provided to hide the screw 71.

[0045] A waterproof gasket 23 is attached to the interface where the lower case segment 31 and the upper case segment 41 are joined at their joining surface P1. In this embodiment, the gasket 23 has the same rectangular shape as the opening edge and is made of a fluororesin such as FPM. This waterproof gasket 23 is compressed by tightening the screws 71 from above and below while positioned between the lower case segment 31 and the upper case segment 41. As a result, no gaps are formed at the interface between the lower case segment 31 and the upper case segment 41, improving the seal and making the outer case 21 waterproof.

[0046] Next, we will explain the structure (contact maintaining structure) for maintaining contact between the shoe 61 and the pipe 1 in this embodiment. As shown in Figures 3 to 6, the contact maintaining structure in this embodiment is composed of a pressure plate 74, a screw member 73, and a coil spring 82.

[0047] The pressure plate 74 is a rectangular metal plate having heat resistance and rigidity at least between 90°C and 200°C. In this embodiment, the pressure plate 74 has a length equivalent to that of the shoe 61. The pressure plate 74 is disposed between one of the two shoes 61 (the upper shoe 61 in FIGS. 3 to 6 ) and the inner wall surface 51a of the inner case 22. The pressure plate 74 is disposed such that its front surface is in surface contact with the first pressed portion P1 of the shoe 61 (the top surface 67 of the shoe 61). Note that both longitudinal ends of the pressure plate 74 are not in surface contact with the top surface 67 of the shoe 61, and each protrude in the front-to-rear direction of the main body 62.

[0048] The screw member 73 is a male screw member with a thread groove (not shown) formed on its outer periphery, tapered toward its tip, and flat. The screw member 73 is inserted into the female screw hole 58 provided in the inner case 22. The screw tip of the screw member 73 reaches the inside of the inner case 22 and abuts against the approximate center of the back surface of the pressure plate 74. When the screw member 73 is threaded, it applies a pressing force that presses the first pressed portion P1 toward the center of the pipe 1 via the pressure plate 74. As a result, the pair of shoes 61 are held and fixed to the inner case 22 and the pipe 1 so as not to shift position. The contact pressure of the shoe 61 against the pipe 1 during assembly at room temperature can be set by adjusting the degree of threading of the screw member 73. The legs 66 are located relatively close to the screw member 73 when the axial direction D1 of the pipe 1 is used as a reference.

[0049] The pair of coil springs 82 are disposed on the upper shoe 61 side of the inner case 22 in FIGS. 3 to 6 , in other words, on the same side as the pressure plate 74, and are provided at positions spaced apart in the front-to-rear direction of the shoe 61. In this embodiment, the coil springs 82 are made of a metal wire having heat resistance and elasticity at least between 90°C and 200°C. Note that, when the axial direction D1 of the piping 1 (the front-to-rear direction D2 of the shoe 61) is used as a reference, the pair of coil springs 82 are provided at positions relatively far from the screw member 73. The pair of coil springs 82 have the same spring constant and are both constantly compressed. The pair of coil springs 82 are provided within the inner case 22 with their first ends t1 abutting against the second pressed portion P2 of the shoe 61. More specifically, first locking portions 68a are provided at the center of the upper surface of the front tongue piece 68 and the center of the upper surface of the rear tongue piece 69, respectively, to position the first ends t1 of the pair of coil springs 82. In this embodiment, the first locking portions 68a are cylindrical protrusions, and the first ends t1 of the coil springs 82 are fitted onto and fixed to these protrusions. In other words, the first ends t1 of the pair of coil springs 82 are provided within the inner case 22 in a state of abutting against the upper surfaces of the front tongue piece 68 and the rear tongue piece 69, which are the second pressed portion P2, respectively.

[0050] Additionally, second locking portions 75a are provided on the front surface of the pressure plate 74 to position the second ends t2 of the pair of coil springs 82. The second locking portions 75a are positioned opposite the first locking portions 68a. In this embodiment, the second locking portions 75a are cylindrical protrusions, and the second ends t2 of the coil springs 82 are fitted onto and fixed to the protrusions. That is, the second ends t2 of the pair of coil springs 82 are provided within the inner case 22 while abutting against the front surface of the pressure plate 74. The pair of coil springs 82 constantly apply a biasing force that presses the second pressed portion P2 toward the center of the piping 1. The biasing force of the pair of coil springs 82 increases in proportion to the degree of threading of the screw member 73 and is smaller than the pressing force of the screw member 73.

[0051] Here, the problems of the conventional leg clamping type straight-type flowmeter sensor will be described with reference to FIG. 7. FIGS. 7(a) to 7(e) are cross-sectional views schematically illustrating a pair of shoes 61, a coupling material layer 81, and a pipe 1 to explain the above-mentioned problems. FIG. 7(a) shows the state after these components have been assembled at room temperature. The shoe bottom surfaces 65 of the pair of shoes 61 contact the pipe 1 with a predetermined contact pressure via the coupling material layer 81. This contact pressure is set in advance by adjusting the degree of threading of the screw members 73, as described above. Note that at this point, the pipe 1 has not yet undergone thermal deformation (thermal expansion). Incidentally, this state is maintained even when the initial flow rate measurement is performed in an environment where a room-temperature liquid flows before a high-temperature liquid is flowed.

[0052] Figure 7(b) shows the state during flow measurement in an environment where a high-temperature liquid flows, showing the pipe 1 softening and thermal expansion, resulting in an expansion in diameter. However, the pipe 1, which has softened and thermally expanded, actually deforms as shown in Figure 7(c), with its outer surface pressed against the inner surface of the leg 66 and the coupling material layer 81, forming a tight seal. In other words, because the pipe 1 is housed in a space with a rectangular cross section, even if it originally had a circular cross section, heating causes it to deform to approach the rectangular cross section of the housing space. In this state, the tight seal between the shoe bottom surface 65 and the pipe 1 via the coupling material layer 81 is maintained. Therefore, sensitivity does not decrease.

[0053] Figures 7(d) and 7(e) both show the state after flow rate measurement in an environment where a high-temperature liquid flows, when the temperature of the liquid flowing through the pipe 1 (i.e., the temperature of the pipe 1) has dropped to room temperature. At this time, the pipe 1 hardens in a state of reduced diameter due to contraction. For example, in Figure 7(d), the inner surface of the leg 66 is not pressed against the pipe 1, creating a gap G1 between them. On the other hand, the coupling material layer 81 is in contact with and pressed against the pipe 1. Therefore, in this state, an ultrasonic propagation path from the ultrasonic vibrator 64 to the liquid in the pipe 1 is secured, preventing a decrease in sensitivity. In contrast, in Figure 7(e), the inner surface of the leg 66 is in contact with and pressed against the pipe 1. In other words, the leg 66 clamps and fixes the pipe 1 from both sides (left and right in Figure 1), making it difficult for the pipe 1 to move (deform) in the vertical direction. Therefore, in Figure 7(e), the coupling material layer 81 is not pressed against the pipe 1, creating a gap G1 between them. Therefore, the ultrasonic wave propagation path cannot be secured, making measurement impossible. Furthermore, even if the coupling material layer 81 is in contact with the pipe 1, sufficient contact pressure cannot be obtained, resulting in a decrease in sensitivity. Of course, if the decrease in sensitivity is significant, measurement will become impossible. Once the adhesion between the shoe bottom surface 65 and the pipe 1 via the coupling material layer 81 is reduced, the sensitivity will remain reduced thereafter, regardless of whether a room temperature fluid or a high temperature fluid is being measured, and will never recover.

[0054] 8(a) and 8(b) are schematic plan views of a pair of shoes 61, a coupling material layer 81, a pipe 1, a screw member 73, and a pressure plate 74 in a conventional leg-clamping type straight-type flowmeter sensor. Similar to FIG. 7(a), FIG. 8(a) shows the state after these components are assembled at room temperature. At this time, a predetermined contact pressure is set by adjusting the degree of threading of the screw member 73, and a relatively large pressure force (see arrow A1) is applied to the shoe 61. Similar to FIGS. 7(d) and 7(e), FIG. 8(b) shows the state after the temperature of the pipe 1 has cooled to room temperature after a flow rate measurement was performed in an environment where a high-temperature liquid was flowing. In FIG. 8(b), for example, a gap G1 is generated between the top surface 67 of the shoe 61 and the pressure plate 74, so that no pressure is applied to the top surface 67 of the shoe 61.

[0055] FIG. 8( c ) is a plan view schematically illustrating the pair of shoes 61, the coupling material layer 81, the pipe 1, the screw member 73, the pressure plate 74, and the pair of coil springs 82 in this embodiment. FIG. 8( c ) shows the state after these components are assembled at room temperature. At this time, a predetermined contact pressure is set by adjusting the degree of threading of the screw member 73, and a relatively large pressing force (see arrow A1) is applied to the shoe 61. Furthermore, a relatively small biasing force (see arrow A2) is also applied to the shoe 61 by the pair of coil springs 82, which are constantly compressed. FIG. 8( d ) illustrates the state after the temperature of the pipe 1 has cooled to room temperature after flow rate measurement in an environment where a high-temperature liquid flows. In FIG. 8( d ), for example, a gap G1 is generated between the top surface 67 of the shoe 61 and the pressure plate 74, so that no pressing force is applied to the top surface 67 of the shoe 61. However, the biasing force of the pair of coil springs 82 is still applied to the shoe 61, so that the contact pressure is maintained at or above a predetermined value.

[0056] [Example] Evaluation tests performed on the straight type flow meter sensor 11 of this embodiment will be described below.

[0057] In this evaluation test, the straight-type flowmeter sensor 11 of this embodiment was prepared, and the pair of coil springs 82 was removed, and the pipe 1 was set between the pair of shoes 61, and the sensor 11 was then reassembled. In Test 1, the sensitivity of this sensor 11 was measured at room temperature. The results are shown in Table 1 (Comparative Example 1). Here, the "GAIN value" was determined as an index representing sensitivity. The GAIN value is a numerical value indicating the amount of amplification required to bring the measured ultrasonic signal to a certain level. Incidentally, a high GAIN value means that the ultrasonic propagation strength is low and a large amount of amplification is required (i.e., low sensitivity).

[0058] In Test 2, the sensor 11 used in Test 1 was left at 170°C for 1 hour, then returned to room temperature, and this was repeated several times, after which the sensitivity was measured at room temperature using the above-mentioned method. The results are shown in Table 1 (Comparative Example 2).

[0059] In Test 3, a pair of "type A" coil springs 82 was attached to the sensor 11 used in Test 2, and in this state, the pipe 1 was set between a pair of shoes 61, and the sensor 11 was reassembled. The type A coil spring 82 was a stainless steel coil spring with a spring constant of 0.49 N / mm and an outer diameter of 3 mm. The sensor 11 was then left at 170°C for one hour and then returned to room temperature once, after which the sensitivity was measured at room temperature using the above-described method. The results are shown in Table 1 (Example 1).

[0060] In Test 4, a pair of "type B" coil springs 82 was attached to the sensor 11 used in Test 2, and in this state, the pipe 1 was set between a pair of shoes 61, and the sensor 11 was reassembled. The type B coil spring 82 was a stainless steel coil spring with a spring constant of 0.29 N / mm and an outer diameter of 3 mm. The sensor 11 was then left at 170°C for one hour and then returned to room temperature once, after which the sensitivity was measured at room temperature using the above-mentioned method. The results are shown in Table 1 (Example 2).

[0061] As shown in Table 1, in Comparative Example 1, which had not yet been exposed to a high-temperature environment, the GAIN value was "54," whereas in Comparative Example 2, which had been exposed to a high-temperature environment, the GAIN value was "110," which was found to be significantly higher. In contrast, in Example 1, in which type A coil spring 82 was added, the GAIN value was "59," and it was confirmed that the value returned to approximately the same as in Comparative Example 1. Also, in Example 2, in which type B coil spring 82, which has a smaller spring constant, was added, the GAIN value was "60," and it was confirmed that the value returned to approximately the same as in Comparative Example 1. In other words, it was found that in Examples 1 and 2, in which a pair of coil springs 82 was added, sensitivity was maintained even after exposure to a high-temperature environment.

[0062] Therefore, according to this embodiment, the following effects can be obtained.

[0063] (1) According to the configuration of the straight-type flowmeter sensor 11 of this embodiment, a pressing force corresponding to the degree of threading of the screw member 73 acts to press the first pressed portion P1 of the shoe 61 toward the center of the pipe 1 via the pressing plate 74, and the shoe 61 is assembled in a state of intimate contact with the pipe 1. Furthermore, the coil spring 82 is provided in the inner case 22 in a constantly compressed state, and its biasing force constantly presses the second pressed portion P2 of the shoe 61 toward the center of the pipe 1. Therefore, even if the fluid temperature drops from a high temperature to room temperature and the pressing force acting via the pressing plate 74 decreases or disappears, the shoe 61 is pressed by the coil spring 82. Therefore, the intimate contact between the shoe bottom surface 65 and the pipe 1 via the coupling material layer 81 is maintained, thereby ensuring a suitable ultrasonic propagation path. Therefore, a straight-type flowmeter sensor 11 can be provided that maintains sensitivity over a wide temperature range, including high temperatures, and can perform stable measurements without becoming unable to measure.

[0064] (2) In this embodiment, the pair of coil springs 82 are provided at positions spaced apart in the front-to-rear direction of the shoe 61. Therefore, compared to when the coil spring 82 is provided at only one location, it is possible to apply a uniform pressing force to the shoe 61. Furthermore, when the pair of coil springs 82 are spaced apart in the front-to-rear direction, the shoe 61 is stably positioned. As a result, tilting or misalignment of the shoe 61 is less likely to occur.

[0065] (3) In this embodiment, the front tongue 68 is integrally formed on the lower portion of the front side of the main body 62, and the rear tongue 69 is integrally formed on the lower portion of the rear side of the main body 62. The first ends t1 of the pair of coil springs 82 are disposed within the inner case 22 in contact with the upper surfaces of the front tongue 68 and the rear tongue 69, respectively, which form the second pressed portion P2. The front surface of the pressure plate 74 is disposed in surface contact with the top surface 67 of the shoe 61, which forms the first pressed portion P1. This configuration therefore facilitates securing a suitable space for accommodating the pair of coil springs 82 in the front and rear regions of the shoe 61. This facilitates assembly of the pair of coil springs 82. Furthermore, the upper surfaces of the front tongue 68 and the rear tongue 69 provide the second pressed portion P2 of the required size. Therefore, the first ends t1 can be stably disposed in contact with the respective upper surfaces. Furthermore, a first pressed portion P1 of a required size is secured on the top surface 67 of the shoe 61. Therefore, the front surface of the pressing plate 74 can be placed in stable surface contact with the top surface 67.

[0066] (4) In this embodiment, first locking portions 68a, 69a that position the first ends t1 of the pair of coil springs 82 are provided on the upper surfaces of the front and rear tongues 68, 69, respectively. Furthermore, second locking portions 75a that position the second ends t2 of the pair of coil springs 82 are provided on the front surface of the pressure plate 74, with which the second ends t2 of the pair of coil springs 82 abut. Therefore, with this configuration, the first ends t1 are locked by the first locking portions 68a, 69a, thereby positioning the first ends t1 at preferred positions on the upper surfaces of the front and rear tongues 68, 69, respectively. Furthermore, the second ends t2 are locked by the second locking portions 75a, thereby positioning the second ends t2 at preferred positions on the front surface of the pressure plate 74. As a result, the first ends t1 and the second ends t2 of the pair of coil springs 82 are less likely to shift laterally in the spring radial direction. Therefore, the biasing force of the pair of coil springs 82 can be reliably applied to the shoe 61. Furthermore, the pair of coil springs 82 can be easily assembled into the inner case 22.

[0067] Second Embodiment Next, a straight-type flow meter sensor 11A according to a second embodiment will be described in detail with reference to Figures 9 and 10. Note that only the configurations different from those of the first embodiment will be described here, and the same components will be denoted by the same reference numerals and will not be described.

[0068] As shown in FIG. 9 , this straight-type flowmeter sensor 11A has a contact maintenance structure composed of a pressure plate 74A, a screw member 73, and a coil spring 82. The pressure plate 74A, the screw member 73, and the coil spring 82 are all arranged on the side of one of the two shoes 61 (the upper shoe 61 in FIG. 9 ). The pressure plate 74A used in this embodiment is different from the pressure plate 74 of the first embodiment. Specifically, insertion portions 89 into which a pair of coil springs 82 can be inserted are formed at both ends of the pressure plate 74A in the longitudinal direction (see FIG. 10 ). In this embodiment, the insertion portions 89 are U-shaped notched grooves. These notched grooves have a width slightly larger than the diameter of the coil springs 82, allowing the coil springs 82 to be inserted.

[0069] In this embodiment, the pair of coil springs 82 are provided inside the inner case 22 with their first ends t1 in contact with the second pressed portion P2 of the shoe 61, which is the same as in the first embodiment. However, unlike the first embodiment, in which the second ends t2 in contact with the front surface of the pressing plate 74, in this embodiment the second ends t2 in contact with the inner wall surface 51a of the inner case 22. In other words, the pair of coil springs 82 are disposed inside the inner case 22 in a state where they do not interfere with the pressing plate 74A.

[0070] Even in the straight-type flowmeter sensor 11A configured as described above, the shoe 61 is pressed by the coil spring 82, thereby maintaining close contact between the shoe 61 and the pipe 1. Therefore, as in the first embodiment, flow rate measurement can be performed while maintaining stable sensitivity over a wide temperature range, including high temperatures. Furthermore, with the configuration of this embodiment, the second ends t2 of the pair of coil springs 82 receive resistance from the inner wall surface 51a of the inner case 22, so that a biasing force pressing the shoe 61 can be generated on the opposite side, the first ends t1. Furthermore, because the pair of coil springs 82 do not press the pressing plate 74A, the biasing force can be set independently of the pressing force via the pressing plate 74A.

[0071] [Third Embodiment] Next, a straight-type flow meter sensor 11B according to a third embodiment will be described in detail with reference to Fig. 11. Note that only the configurations different from those of the first embodiment will be described here, and the same components will be denoted by the same reference numerals and will not be described.

[0072] As shown in FIG. 11 , this straight-type flowmeter sensor 11B is similar to the first embodiment in that it includes a contact maintaining structure composed of a pressure plate 74, a screw member 73, and a coil spring 82. However, the pressure plate 74A and the screw member 73 are disposed on the side of one of the two shoes 61 (the upper shoe 61 in FIG. 11 ), and the pair of coil springs 82 are disposed on the side of the other shoe 61 (the lower shoe 61 in FIG. 9 ). That is, while all of the above three components are disposed on the side of one shoe 61 in the first embodiment, this embodiment differs in that some of the above three components are disposed on the side of the other shoe 61. Note that in this embodiment, second ends t2 of the pair of coil springs 82 are engaged with protrusions that serve as second engaging portions 52a protruding from the inner wall surface 51a of the inner case 22.

[0073] Even in the straight-type flowmeter sensor 11B configured in this manner, the shoe 61 is pressed by the coil spring 82, thereby maintaining close contact between the shoe 61 and the pipe 1. Therefore, similar to the first embodiment, flow rate measurement can be performed while maintaining stable sensitivity over a wide temperature range, including high temperatures.

[0074] The above embodiment may be modified as follows.

[0075] In the first embodiment and the like, a cylindrical protrusion is provided as the first engaging portion 68a, and the first ends t1 of the pair of coil springs 82 are inserted thereinto, but this is not limited to this. For example, in another embodiment, a protrusion having a shape other than a cylindrical shape (e.g., a hemispherical shape) may be provided. Also, a recess may be provided instead of the protrusion, and the first ends t1 of the pair of coil springs 82 may be inserted and fixed into the recess. Of course, a configuration without the protrusion or recess may be used, in which case, for example, the first ends t1 may be fixed by adhesive to the second pressed portion P2.

[0076] In the first embodiment and the like, a cylindrical protrusion is provided as the second locking portion 75a, and the second ends t2 of the pair of coil springs 82 are inserted thereinto. However, this is not limited to this. For example, in another embodiment, a protrusion having a shape other than a cylindrical shape (e.g., a hemispherical shape) may be provided. Also, a recess may be provided instead of the protrusion, and the second ends t2 of the pair of coil springs 82 may be inserted and fixed into the recess. Of course, a configuration without the protrusion or recess may be used. In this case, for example, the second ends t2 may be fixed by adhesive to the pressing plate 74 or the inner wall surface 51a.

[0077] In each of the above embodiments, a total of four legs 66 are protruded from the shoe bottom surface 65 of the main body 62 that constitutes the shoe 61 in order to clamp and hold the piping 1 from both sides, but this number may be changed.

[0078] In the above-described embodiments, the shoe 61 has a main body 62 that is substantially trapezoidal in side view. However, the present invention is not limited to this. For example, the shoe 61 may have a main body 62 that is substantially triangular in side view.

[0079] In the ultrasonic vibrator 64 of each of the above embodiments, an ultrasonic vibrator 64 made of a porous sintered body of potassium sodium niobate (alkali niobate) is used, but the material of which the ultrasonic vibrator 64 is made is not particularly limited. For example, lead zirconate titanate (PZT), barium titanate, PMN-PT (Pb(Mg １／３ Nb ２／３ ) O ３ -PbTiO ３ ) single crystal, PZNT (Pb(Zn １／３ Nb ２／３ ) O ３ -PbTiO ３ ) single crystal, LiNbO ３ An ultrasonic vibrator 64 made of a single crystal ceramic sintered body may also be used.

[0080] Next, in addition to the technical ideas set forth in the claims, the technical ideas grasped by the above-mentioned embodiments are listed below. (1) In claim 1 etc., further comprising a coupling material layer arranged in contact with the outer circumferential surface of the pipe and the bottom surface of the main body of the shoe, and the coupling material layer is made of a heat-resistant material that is heat-resistant in a temperature range of 90°C to 200°C. (2) In claim 1 etc., the pressure plate and the coil spring are arranged on one side of the pair of shoes. (3) In claim 1 etc., the pressure plate is arranged on one side of the pair of shoes, and the coil spring is arranged on the other side.

[0081] 1: Pipe 11, 11A, 11B: Straight type flow meter sensor 21: Outer case 22: Inner case 51a: Inner wall surface (of inner case) 52a, 75a: Second locking portion 61: Shoe 62: Main body 63: Inclined surface 64: Ultrasonic vibrator 65: Bottom surface of shoe 66: Leg 66a: Front leg 66b: Rear leg 67: Top surface (of shoe) 68: Front tongue 68a, 69a: First locking portion 69: Rear tongue 73: Screw member 74, 74A: Pressing plate 81: Coupling material layer 82: Coil spring 89: Insertion portion D1: Axial direction (of pipe) D2: Front-rear direction of shoe P1: First pressed portion P2: Second pressed portion t1: First end t2: Second end

Claims

1. A straight flow meter sensor comprising: a pair of shoes arranged offset in the axial direction of a straight pipe through which a fluid flows, the pair of shoes having a main body supporting an ultrasonic vibrator on an inclined surface on the front side and a plurality of legs protruding from the bottom surface of the shoes so as to sandwich the pipe from both sides; a coupling material layer arranged in contact with the outer circumferential surface of the pipe and the bottom surface of the shoes; an inner case that houses and positions the pair of shoes; and an outer case that houses the inner case, wherein the straight flow meter sensor comprises: a pressure plate arranged between the shoes and the inner wall surface of the inner case, with the front surface of the plate in surface contact with a first pressed portion of the shoe; and a screw member arranged within the inner case with the tip of the screw abutting against the back surface of the pressure plate, and screwed in to apply a pressing force that presses the first pressed portion towards the center of the pipe via the pressure plate. a coil spring that is provided within the inner case with a first end abutting against a second pressed portion of the shoe and being constantly compressed, and that applies a biasing force that presses the second pressed portion toward the center of the piping.

2. A straight type flow meter sensor according to claim 1, wherein a pair of said coil springs are provided at positions spaced apart in the front-rear direction of said shoe.

3. A straight-type flow meter sensor as described in claim 2, characterized in that a front tongue is integrally formed on the lower part of the front side of the main body, and a rear tongue is integrally formed on the lower part of the rear side of the main body, the first ends of the pair of coil springs are provided within the inner case in a state of abutting against the upper surfaces of the front tongue and the rear tongue, which are the second pressed part, respectively, and the front surface of the pressing plate is arranged in surface contact with the top surface of the shoe, which is the first pressed part.

4. A straight-type flow meter sensor as described in claim 3, characterized in that the second ends of the pair of coil springs are provided within the inner case in a state where they are each in contact with the front surface of the pressing plate.

5. A straight-type flow meter sensor as described in claim 4, characterized in that a first locking portion for positioning the first ends of the pair of coil springs is provided on the upper surface of the front tongue piece and the upper surface of the rear tongue piece.

6. A straight-type flow meter sensor according to claim 5, characterized in that a second locking portion for positioning the second ends of the pair of coil springs is provided on the front surface of the pressure plate.

7. A straight-type flow meter sensor as described in claim 3, characterized in that the second ends of the pair of coil springs are arranged within the inner case in a state where they are each in contact with the inner wall surface of the inner case.

8. A straight-type flow meter sensor as described in claim 3, characterized in that insertion portions into which the pair of coil springs can be inserted are formed at both longitudinal ends of the pressure plate, and the second ends of the pair of coil springs are inserted into the insertion portions and are provided within the inner case in a state in which they are each in contact with the inner wall surface of the inner case.

9. A straight-type flow meter sensor as described in claim 8, characterized in that the upper surface of the front tongue and the upper surface of the rear tongue are each provided with a first locking portion for positioning the first ends of the pair of coil springs.

10. A straight-type flow meter sensor as described in any one of claims 1 to 9, characterized in that the multiple legs are a total of four, consisting of a pair of front legs and a pair of rear legs, and when the axial direction of the piping is used as a reference, the multiple legs are located relatively close to the screw member, and the pair of coil springs are located relatively far from the screw member.

11. A straight type flow meter sensor according to any one of claims 1 to 9, characterized in that the piping is made of a resin material having a heat resistance of 200°C, and the flow meter sensor is used in an environment where the fluid flows through the piping at a temperature of 90°C or higher.

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