JPH0582891B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a mass flow rate system having a structure including a rotating body, a rotating body drive section, and a rotation detector that directly or indirectly detects the rotation speed of the rotating body. The present invention relates to a mass flowmeter that measures mass flow rate using a meter transmitter.

<Prior Art> A conventionally known mass flowmeter of this type is, for example, one described in "Aeronautical Engineering Course (4), Aviation Instruments" (published by Japan Aeronautical Technology Association). FIG. 3 is an exploded block diagram showing the outline of this mass flowmeter.

In Fig. 3, 1 indicates the measuring fluid (hereinafter referred to as "fluid").
This is a mass flow transmitter (hereinafter abbreviated as "transmitter") inserted into the measuring tube through which Q flows. Inside this transmitter 1, a power supply part E is assembled on the rotation center axis located parallel to the upstream tube axis, has a circulation port 2a on the periphery, and is connected to, for example, 28VDC.
Synchro motor M driven by power supplied from
and an impeller 2, which is a rotating body to which rotational force is applied by a gear train H, and a fixed disk 3 provided on the downstream side.
An arrow F that is connected to the impeller 2, has almost the same structure as the impeller 2, is provided on the same axis as the rotation center axis of the impeller 2, and is given rotational force by the impeller 2.
A turbine 4, which is a torque detection body for detecting the torque of the fluid Q, is provided. A restraining spring 5 has a function of restraining the rotation of the turbine 4 and balancing the turbine 4 at a displacement angle proportional to the flow rate of the fluid Q. That is, the fluid Q to which rotational force has been applied flows through the flow hole 2a of the impeller 2, through the flow hole 4a of the turbine 4, as shown by arrow F, and flows away to the outlet. At this time, the impeller 2 is rotated at a constant angular velocity ω by the synchro motor M, giving a certain rotational speed to the fluid Q flowing through the flow hole 2a, which flows into the turbine 4 and imparts torque. The shaft of the turbine 4 is stopped at a displacement angle where the torque given by the fluid Q and the restraining spring 5 are balanced, and this displacement angle is converted into an electric signal by a magnetine 6 electrically connected to the turbine shaft. be done.
This converted signal is sent to meter 7 to display the mass flow rate. In other words, the torque received from the fluid detected by the turbine 4 is directly proportional to the mass flow rate, so by displaying the displacement angle detected by the magnetine 6 on the instrument 7, the mass flow rate of the fluid Q that has passed can be determined. .

<Problems to be Solved by the Invention> In order to rotate the impeller at a constant speed, conventional mass flowmeters require a highly accurate and stable power source with a structure free from frequency fluctuations. on the other hand,
Even if such a highly accurate power source is used, the display accuracy is not good because the torque of the magnetine 6 is small, so it is difficult to improve the accuracy of the entire device. Furthermore, since the transmitter has an impeller 2, a turbine 4, etc. in its structure, it cannot be miniaturized beyond a certain level, and there is a problem that it is difficult to use it in a case where the installation space is limited, such as in an aircraft.

The present invention has been made in view of the problems of the conventional technology, and an object of the present invention is to provide a compact and highly accurate mass flow meter.

<Means for Solving the Problems> In order to achieve such an object, the present invention includes: an impeller that is provided in a pipe through which a fluid flows and rotates against reaction torque received from the fluid; a rotation detection section that detects the rotation speed of the impeller; a rotation control means that controls the rotation speed detected by the rotation detection section so that it always becomes a constant rotation; and the rotation control means controls the rotation of the impeller to be constant. A CPU that obtains the mass flow rate of the fluid based on a drive value.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings. In the following drawings, parts that overlap with those in FIG. 3 are given the same numbers, and their explanations will be omitted.

FIG. 1 is a structural block diagram showing a specific embodiment of the mass flowmeter of the present invention.

In FIG. 1, reference numeral 10 denotes a mass flowmeter transmitter (hereinafter abbreviated as "transmitter") which is inserted and assembled into a measuring tube (not shown) through which fluid Q flows. This transmitter 10 consists of a rotating body 2, which is composed of an impeller that is assembled on a rotation center axis located parallel to the tube axis and receives a reaction torque from a fluid Q that is directly proportional to the mass flow rate.
0 and (when the fluid Q passes through the impeller, it receives a force in the direction of rotation, and the inertia coefficient of the fluid I×
At the same time that an angular momentum of the angular velocity ω is applied to the impeller, the impeller receives a reaction load from the fluid in the opposite direction to the rotational direction, which is a reaction torque of an angular momentum of Iω. Although the explanation is omitted, this reaction torque is directly proportional to the mass flow rate), and the impeller 20 is driven (rotated) at a constant rotation speed via a coupling K consisting of a pair of components, such as a pulse motor, a DC motor, or a synchronous motor. A rotation drive unit 11 consisting of a motor etc. (in this example, a pulse motor is used and will be explained below), and a rotation detector (in this example, a rotation detector for directly or indirectly detecting the rotation speed of the impeller 20). 12 (showing a case where it is assembled on a motor shaft for indirect detection), and a cavity 13 provided to house one coupling K, the pulse motor 11, and the rotation detector 12 and isolate them from the fluid Q. , a connector C that relays a cable for introducing a drive signal (pulse) to the pulse motor 11 and a cable for deriving a detected value from the rotation detector 12. Reference numeral 30 inputs the rotation detection value from the rotation detector 12, calculates a drive value that maintains the rotation speed of the impeller 20 at a constant value regardless of the flow rate of the fluid Q, and outputs the drive value to the pulse motor 11, as well as the calculated drive value. Fluid Q based on
This is a mass flow rate calculation unit that obtains the mass flow rate value. More specifically, the mass flow rate calculation section 3 in this embodiment
0 is composed of a calculation section 31, a pulse generation means 32, and a display section 33, and the calculation section 31 first outputs an initial pulse setting value to the pulse generation means 31 in order to keep the impeller 20 at a constant rotation speed, After this, the rotation speed of the impeller 20 tends to decrease due to the torque received from the fluid Q, so the state at this time is input sequentially from the rotation detector 12, and the rotation speed of the impeller 20 is kept at a constant value regardless of the flow rate of the fluid Q. A new pulse setting value to be maintained is calculated, and the calculated new pulse setting value is outputted to the pulse generator 32, and a mass flow rate value of the fluid Q based on the calculation result is outputted to the display section 33. For this purpose, the arithmetic unit 31 can be configured with a microcomputer.
Specifically, for example, a calculation unit (CPU) 31a,
A read-only memory (ROM) 31b stores the calculation method of the CPU 31a, and a random access memory (RAM) 31c stores and reads the calculation results and the characteristics of the flow rate Q.
, a rotation detection input interface 31d into which the rotation detection value from the rotation detector 12 is input, and a fluid Q.
An initial setting value output I/F 31e that outputs the first pulse setting value based on the , a change rotation output I/F 31f that outputs the new pulse setting value, a mass flow rate output I/F 31g that outputs the mass flow rate, and an external input For example, it includes an input I/F 31h for inputting information regarding calculation conditions and flow rate. Pulse generating means 32
outputs a pulse signal, which is a drive signal, to the pulse motor 11 in accordance with the pulse setting value set by the calculation section 31. Although the display section 33 is designed to display the output from the mass flow rate output I/F 31g, the mass flow rate is calculated by counting the pulse setting value of the pulse generating means 32 as a pulse per unit time. The configuration may be such that it is displayed. However, if it is configured as shown in Figure 1, it can be applied to other applied display methods in addition to counting and displaying, and it can also be configured to derive this output to external equipment (not shown). It is possible. Furthermore, it goes without saying that when a DC motor is used instead of the pulse motor 12, the pulse generating means becomes a DC current generating means. The point depends on the rotary drive unit used, and it may be unnecessary in some cases.

FIG. 2 is a flow sheet showing the operation of the mass flowmeter of the present invention.

Now that the flow velocity of the fluid Q is zero, the mass flow rate calculation section 30 first sets the initial setting value to the CPU.
31b and stores it in the RAM 31c, and at the same time outputs the initial setting value to the pulse generating means 32 I/F 3.
1e to drive the pulse motor 11 with the drive signal from the pulse generating means to drive the impeller 20.
is rotated, and the rotation of the pulse motor 11 is detected by the rotation detector 12 and input to the rotation detection input 31d of the mass flow rate calculation section 30. At this time, it is confirmed that the detected rotational speed value is a constant value, and the mass flow rate when the flow velocity is zero is calculated based on the initial setting value and displayed on the display section 33. After this, fluid Q is caused to flow. The rotation speed of the impeller 20 decreases as the fluid Q flows. This state is detected by the rotation detector 12. Based on the detected rotational speed, a new set value is calculated in the calculation section 31 of the mass flow rate calculation section 30 to increase the rotation of the impeller 20. Based on this new set value, pulses are transmitted from the pulse generating means 32 to the pulse motor 1.
1, the rotation of the pulse motor 11 increases, and the rotation of the impeller 20 increases. This series of operations continues during the ascent. The mass flow rate is calculated every time a new set value is calculated, so
The successively updated values are displayed on the display section 33. The mass flow rate of the fluid Q at that point is when the rotational speed reaches a constant value. Thereafter, such operations are continued during the measurement period.

<Effects of the Invention> As described above in detail with reference to the embodiments, according to the mass flowmeter of the present invention, it is possible to configure a mass flowmeter transmitter that has a simple structure and can be downsized. Since the structure can eliminate the deterioration in indication accuracy due to the influence caused by the use of magnesine, a highly accurate mass flowmeter can be provided at a low cost. Furthermore, when a pulse motor is used as shown in FIG. 1, signal processing is facilitated by using pulse signals, which has the effect of facilitating design.

[Brief explanation of the drawing]

Fig. 1 is a structural block diagram showing a specific embodiment of the mass flow meter of the present invention, Fig. 2 is a flow sheet showing the operation of the mass flow calculation section of the present invention, and Fig. 3 is an outline of a conventional mass flow meter. FIG. 1,10...Mass flow transmitter (transmitter), 2,
20... Rotating body (impeller), 4... Turbine,
5...Block spring, 11...Pulse motor,
12... Rotation detector, 30... Mass flow rate calculation unit.

Claims (1)

[Scope of Claims] 1. An impeller that is installed in a pipe through which a fluid flows and rotates against reaction torque received from the fluid; a rotation detection section that detects the number of rotations of this impeller; and a rotation detection section that detects the rotation speed of this impeller. A rotation control means for controlling the detected rotation speed so that it always becomes a constant rotation; and a CPU for obtaining the mass flow rate of the fluid based on a drive value by which the rotation control means controls the rotation of the impeller to be constant. A flow rate mass meter characterized by: