JPH0554891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Coriolis force mass flowmeter that measures the mass flow rate of a fluid using the Coriolis force.

[Conventional technology]

BACKGROUND ART Conventionally, a mass flowmeter using the Coriolis force is known, as shown in Japanese Patent Application Laid-Open No. 59-92314.

The measurement principle of this type of mass flow meter is that when a fluid is passed through a rotating or vibrating curved tube, the velocity of the fluid mass moving in this curved tube and the angular velocity vector of the rotation or vibration of the curved tube are both perpendicular to each other. A Coriolis force (a force that causes twisting in a curved pipe) is generated,
Furthermore, since the amount of deflection or force based on this Coriolis force has a certain relationship with the mass flow rate in the curved pipe, the mass flow rate can be measured by detecting the Coriolis force by some means. I can do it.

This Coriolis force mass flowmeter has the advantage of being able to measure the flow velocity of high-viscosity materials because there are no obstacles to the fluid such as rotating blades.

The mass flowmeter described in the above publication uses an electromagnetic drive mechanism provided between the free ends of a U-shaped curved tube on one side and a U-shaped curved tube on the other side, which are arranged in parallel, to generate the vibration displacement necessary for generating the Coriolis force. Fluid is applied to the free ends of the U-shaped curved tubes on both sides while passing fluid from one end to the other, and the amount of deflection of the curved tubes is detected as a means of measuring the Coriolis force generated.

In order to detect the amount of this deflection, electromagnetic sensors consisting of coils and magnets are provided on the sides of the electromagnetic drive parts of the U-shaped curved tubes on both sides, that is, in the vicinity of the free ends where the curved tubes can move freely. The vibration displacement or amplitude of the flexible structure of the curved pipe is extracted as a Coriolis force measurement signal.

[Problem that the invention seeks to solve]

However, in order to extract such vibration displacement as output, it is necessary to give a large vibration displacement as input to the electromagnetic drive unit, and it is simple to use a flexible structure and extract vibration displacement (amplitude) as output. There is a problem in that the curved pipe vibration system is prone to coupled vibrations and also requires ingenuity in signal processing.

The purpose of the present invention is to change the shape of a curved pipe to obtain a large Coriolis force necessary for reliable measurement, and to provide a pressure-sensitive sensor that uses the Coriolis force in a hard structure part of a vibration system of a curved pipe. The object of this invention is to solve problems such as the above-mentioned coupled vibration by detecting force rather than displacement as in the conventional method.

[Means for solving problems]

The present invention provides free ends 17 of the bent pipe 14 on one side and the bent pipe 15 on the other side, which are provided parallel to the main body 11 of the device.
When fluid is passed from one end of each curved tube 14, 15 to the other end while applying vibration to the curved tubes 14, 15 on both sides,
The present invention relates to a Coriolis force mass flow meter that measures the flow rate of the fluid by detecting changes caused by the Coriolis force occurring in the Coriolis force.

That is, the curved tube 14 on one side and the curved tube 15 on the other side are each formed into an annular shape, and the fixed connection portions at one end and the other end of the curved tubes 14 and 15 on both sides are located on the opposite side from the free end 17. 16 are brought close to each other and fixedly connected to the device main body 11,
A pressure sensitive sensor 45 for detecting the Coriolis force generated between the curved tubes 14 and 15 on both sides is provided between the curved tubes 14 and 15 on both sides near the fixed connection portion 16.

[Effect]

The present invention provides a device in which a vibration input is applied to a relatively soft free end 17 of the curved tube that can be sufficiently displaced in the curved tube vibration system on both sides, and the Coriolis force related to the fluid flow rate is a hard part of the curved tube vibration system. Main body 1
The pressure sensitive sensor 45 detects the pressure between the fixed connection portion 16 and the vicinity of the fixed connection portion 16 relative to the pressure sensitive sensor 45 .

〔Example〕

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

1 to 4 show a first embodiment of the present invention, in which a bent pipe connecting portion 13 is integrally provided on the device main body 11 with a bolt 12, and one side of the bent pipe connecting portion 13 of the device main body 11 is provided. Bent pipe 14 and curved pipe 1 on the other side
Fixed connection parts 16 at one end and the other end of 5 are brought close to each other and fixedly connected, and the opposite side of the fixed connection part 16 is configured to be freely movable as a free end 17.

Screw holes 21 are provided on both sides of the device main body 11, and an inlet port 22 and an outlet port 23 are provided in the screw holes 21 on both sides, respectively. Furthermore, the openings 22 and 23 are connected to the through holes 2 in the device main body 11.
4 and the through hole 25 in the bent pipe connecting part 13 to the fixed connecting parts 16 at both ends of the bent pipes 14 and 15 on both sides. The opening of the through hole 25 in the pipe connection part 13 is closed by a blind screw 26.

Furthermore, an electromagnetic drive mechanism 30 is provided that applies vibration input to the free ends 17 of the curved pipes 14 and 15 on both sides. That is, the screw 3 is attached to the device main body 11.
1, a magnet main body 32 shown in FIG. One end of a leaf spring 35, which also has the function of preventing the pipes 14, 15 from swinging in the left-right direction in FIG. 15 at the free end 17 thereof. A coil 37 is fixed to the inner surface of this leaf spring 35, and this coil 37 is attached to the gap 3 formed between the convex portion 32a of the magnet body 32 and the donut-shaped magnet 33.
8, it is fitted in so that it can move forward and backward. According to the electromagnetic drive mechanism 30 having this structure, the coil 37 is small and lightweight, so that the natural frequency of the bent pipes 14 and 15 can be increased and sufficient displacement can be obtained.

Moreover, the bent pipe 14 on one side and the bent pipe 15 on the other side
fixed connection 1 opposite said free end 17 at
A parallel portion 41 and an opening portion 42 perpendicular to the parallel portion 41 are formed near 6. Sensor mounting parts 43 are welded to the left and right opening parts 42 in FIG. Piezoelectric (ceramic) as a pressure sensitive sensor with nut 44
45 is maintained at a narrow pressure. This piezoelectric 45 is
It outputs a voltage according to the pressing force from the pressing plate parts 47 provided on both sides of the piezoelectric body 46,
8 is an output signal attachment part.

Then, by energizing the coils 37 of the electromagnetic drive mechanism 30 in the curved tube vibration systems on both sides, the free end 17 is made to repeatedly open and close at the relatively soft curved tube free end 17 that can be sufficiently displaced. Give vibration input.

At this time, if there is no flowing fluid in the curved tubes 14, 15, the left and right portions of the curved tubes 14, 15 vibrate symmetrically in opening and closing as shown in FIG. At this time, the piezoelectric elements 45 on both sides provided between the fixed connection part 16 and the vicinity of the device main body 11, which is a hard part of the curved tube vibration system, respond to changes in bending and torsional stress caused by the vibration of the curved tubes 14 and 15. An output is obtained, but since the vibration is symmetrical, when the difference between the outputs of the left and right piezoelectric elements 45 is extracted, the left and right piezoelectric outputs cancel each other out and become 0.

Further, when fluid flows into the vibrating bent pipes 14 and 15, a Coriolis force related to the flow rate of the fluid is generated, and as shown in FIG. A twisting phenomenon occurs in opposite directions on the left and right sides. This phenomenon is caused by the curved pipe 1
The larger the flow rate of the fluid in the fluids 4 and 15, the more noticeable the difference is, and the difference in the outputs of the piezoelectric elements 45 on both sides also appears in accordance with the flow rate. Therefore, by detecting the amplitude of the signal waveform of this difference, the fluid flow rate, which has a constant relationship with the Coriolis force, can be measured.

In this first embodiment, a piezoelectric element 45 is provided between the sensor mounting portion 43 as the pressure sensitive sensor.
However, the present invention is not limited to this. For example, a curved thin plate may be attached between the pair of sensor attachment portions 43, and a strain gauge may be stretched over this thin plate as a pressure-sensitive sensor. It's okay.

Next, FIGS. 5 to 7 show a second embodiment of the present invention, in which the parallel portions 4 of the curved pipes 14 and 15 on both sides
The sensor mounting part 43 is welded to the fifth part.
The piezoelectric element 45 is protruded in the left-right direction in the figure, and the piezoelectric element 45 is sandwiched between upper and lower sensor mounting parts 43 on the left and right sides. In this case, when the Coriolis force is generated, both torsional and bending stress are applied to the piezoelectric element 45. Furthermore, the parallel part 41 is made sufficiently long, and the piezoelectric element 45 is connected to the parallel part 41 and the opening part 42. If it is installed at a position close to , the gist of the present invention, which is to make the vibration system of the curved pipes 14 and 15 sufficiently soft and the output sensor portion sufficiently hard, is achieved, and the S/N ratio is improved. The other structures and operations are the same as those of the first embodiment, so their explanation will be omitted.

Next, FIGS. 8 to 10 show a third embodiment of the present invention, in which sleeves 52 are fitted in two places on the device main body 51, and each sleeve 52 has a pair of collars 5.
3 and 54 are fitted, and the bent pipe 55 on one side and the bent pipe 56 on the other side connected to the collars 53 and 54 are connected to one end and the fixed connection portion 57 at the other end of the device. It is fixed to the main body 51, and the opposite side of the fixed connection part 57 is configured to be freely movable as a free end 58.

An inlet portion 61 and an outlet portion 62 are provided at one end openings of the two sleeves 52, respectively. The openings 61 and 62 are connected to the curved pipes 55 and 56 on both sides through the inner holes in the sleeve 52.
It is communicatively connected to the fixed connection part 57 of. The opening at the other end of the sleeve 52 is closed by a blind screw 63.

Further, an electromagnetic drive mechanism 64 is provided for applying a vibration input to the free ends 58 of the curved pipes 55 and 56 on both sides. That is, a magnet mounting plate 65 is welded to the curved pipe 55 on one side, a magnet 66 is fixed to this mounting plate 65, and a coil mounting plate 67 is welded to the curved pipe 56 on the other side.
A coil 68 that fits into the magnet 66 is attached to this mounting plate 67. Further, one end of a leaf spring 70 for preventing the bent pipes 55 and 56 from swinging in the left-right direction in FIG. The other end is fixed to the free end 58 of each of the curved pipes 55 and 56 via a weld 71.

Moreover, the bent pipe 55 on one side and the bent pipe 56 on the other side
fixed connection 5 opposite said free end 58 at
A parallel portion 75 is formed near 7. As shown in FIG. 9, a pair of torque arms 76 are welded to the parallel portions 75 of the bent pipes 55 and 56 on both sides, respectively. 77 is fixed, and these left and right leaf springs 77 are attached to the sensor mounting rod 7.
Further, a pressure receiving collar 79 is fitted on both side shaft portions 78a of this rod 78, and a piezoelectric (ceramic) 80 as a pressure sensitive sensor is fitted on the outer peripheral surface of this pressure receiving collar 79. has been done. This piezoelectric element 80 has the same structure as the piezoelectric element 45, and the flange portion 8 of the collar 79
1 and a sensor attachment part 83 attached to the device main body 51 with a screw 82, and are held under pressure by a predetermined tightening force of a nut 84 screwed into the shaft part 78a.

Then, by energizing the coils 68 of the electromagnetic drive mechanism 64 in the curved tube vibration systems on both sides, the free end 58 is made to repeatedly open and close at the relatively soft curved tube free end 58 that can be sufficiently displaced. Give vibration input. This opening/closing vibration of the free ends 58 of the curved pipes 55, 56 is converted into a twisting motion and acts on the parallel portion 75.

At this time, if there is no flowing fluid in the curved pipes 55 and 56, the torsional movement of the left and right parallel parts 75
This occurs symmetrically in the figure. Therefore, the left and right torsional movements cancel each other out through the leaf spring 77 and the rod 78, and there is no change in the output from the left and right piezoelectric elements 80.

Further, when fluid flows into the vibrating bent pipes 55, 56, a Coriolis force related to the flow rate of the fluid is generated, and as shown in FIG. Since a torsion phenomenon occurs in opposite directions on the left and right sides, and the left and right leaf springs 77 are deformed in the same direction as shown by the chain lines, pressure is applied to one piezoelectric element 80 while depressurization is applied to the other piezoelectric element 80. The action is applied, and the piezoelectric elements 80 on both sides
There will be a difference in the output. This phenomenon is caused by the bent pipe 55,
The larger the flow rate of the fluid in the fluid 56, the more noticeable it becomes, and the difference in the outputs of the piezoelectric elements 80 on both sides also appears depending on the flow rate. Therefore, by detecting the amplitude of the output difference waveform of the piezoelectric elements on both sides, the fluid flow rate, which has a constant relationship with the Coriolis force, can be measured.

In this third embodiment, the piezoelectric sensor 80 is used as the pressure sensitive sensor, but the present invention is not limited to this. For example, the pair of leaf springs 77
A strain gauge may be installed as a pressure sensitive sensor in the tube.

Although FIG. 11 schematically shows the relationship between the curved pipes on one side and the other side and the pressure sensitive sensor in the first, second and third embodiments, the present invention is limited to this form. Instead, as shown in Fig. 12, the parallel part B bent outward from the bent pipe main body A may be fixedly connected to the device main body, or as shown in Figs. 13 and 14. As shown in FIG. 15, the tube C may be bent into an elliptical shape, and in this case, the influence of the Coriolis force will be noticeable on the pressure sensitive sensor D. Furthermore, the tube C may be bent into an arc shape as shown in FIG. The portion E may be used as a fixed connection portion to the main body of the device and a portion in the vicinity thereof.

Further, the cross sections of the curved pipes on one side and the other side are not limited to perfect circles, and pipes having an oval cross section, a rectangular cross section, or the like may be used as the curved pipes.

〔Effect of the invention〕

According to the present invention, the bent pipe on one side and the bent pipe on the other side are each formed in an annular shape, and the fixed connection portions at the one end and the other end located on the opposite side of the free end of the bent pipes on both sides are mutually connected. A pressure-sensitive sensor is installed near the fixed connection part of the curved pipes on both sides to detect the Coriolis force generated between the curved pipes on both sides. The sensor near the base of the pipe allows the influence of Coriolis force to be detected with high sensitivity, allowing reliable measurement. In addition, since the Coriolis force can be directly detected using a pressure-sensitive sensor installed in the hard structure of this curved pipe vibration system, the large vibration displacement that is present when detecting vibration displacement as in the conventional method can be used as an input. Problems such as the need to provide a signal, the tendency of a curved pipe vibration system to cause coupled vibration, and the need for ingenuity in signal processing can all be solved in one fell swoop.

[Brief explanation of drawings]

Figure 1 shows the first diagram of the Coriolis force mass flowmeter of the present invention.
A plan view showing the embodiment, FIG. 2 is a front view thereof, and FIG.
The figure is a side view, FIG. 4 is an exploded view of the electromagnetic drive mechanism, FIG. 5 is a partial plan view showing the second embodiment of the present invention, FIG. 6 is a front view thereof, and FIG. A side view, FIG. 8 is a plan view showing a third embodiment of the present invention,
9 is a sectional view taken along the line -- in FIG. 8, FIG. 10 is a sectional view taken along the line X--X in FIG. 8, and FIGS. It is a schematic diagram showing a modification of the tube. 11... Device body, 14, 15... Bent pipe, 16
... fixed connection part, 17 ... free end, 45 ... pressure sensitive sensor.

Claims (1)

[Claims] 1. When fluid is passed from one end of each curved tube to the other end while applying vibration to the free ends of the curved tubes on one side and the curved tubes on the other side, which are installed parallel to the main body of the device, the difference between the curved tubes on both sides In a Coriolis force mass flowmeter that measures the flow rate of the fluid by detecting changes based on the Coriolis force that occurs, the curved pipe on one side and the curved pipe on the other side are each formed in an annular shape, and the curved pipes on both sides The fixed connection parts of one end and the other end located on the opposite side of the free end are brought close to each other and fixedly connected to the device main body, and the bent pipes on both sides are connected between the parts near the fixed connection parts of the bent pipes on both sides. A Coriolis force mass flowmeter characterized in that a pressure sensitive sensor is provided for detecting a Coriolis force generated between the two.