JPS5856414B2 - Flow rate measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate measuring device for measuring the flow rate of air, gas, liquid, or other fluid.

Various types of devices have been known for measuring the flow rate (flow rate) of fluid flowing in a flow path, but among them, devices that provide almost no resistance to the flow and can withstand even the slightest sudden change in flow speed are particularly popular. Impeller-type current meters are widely used as they can track the flow rate without delay.

An impeller-type current meter places an impeller in the flow and uses the kinetic energy of the fluid, that is, the impeller rotates in proportion to the flow velocity, to determine the flow velocity of the fluid.
Flow velocity (flow rate) without applying any external energy
It has the advantage of being able to detect

However, in conventional impeller-type current meters, when the fluid flow velocity is low, mechanical losses such as frictional resistance in the bearing decisively affect the detection accuracy, and in the low flow velocity region, the impeller does not work as intended. It has the disadvantage of not exhibiting any behavior and resulting in inaccurate detected values.

The present invention provides an impeller that can accurately determine the flow velocity over a wide range from a low flow velocity region to a high flow velocity region without being affected by mechanical loss such as frictional resistance. This is a vehicle-type flow velocity measuring device.

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

FIGS. 1 and 2 show one embodiment of the present invention, in which an impeller 3 driven by a two-phase servo motor 2 is installed in the center of a flow path 1, and the impeller 3 has two rotations. It is configured to be forcibly rotated by a phase servo motor 2 in the flow direction or in the opposite direction.

The two-phase servo motor 2 is a known motor consisting of a control winding 4, an excitation winding 5, a phase advance capacitor 6, and a rotor 7, as shown in FIG. An AC power supply voltage e is applied to the control winding 5, and a control current IC having the same phase as the power supply voltage e is applied to the control winding 4 by an AC amplifier 8 for current adjustment.

The excitation current im flowing through the excitation winding 5 is applied to the control winding 4 when the rotor 7 is stationary due to the phase advancing capacitor 6.
A leading phase of -z (90) is given to the control current ic (in other words, the AC power supply voltage C) flowing to the control current ic (in other words, the AC power supply voltage C).

The rotation torque generated in the rotor 7 of the two-phase servo motor 2 and the rotation speed have a relationship as shown in FIG. 3.

The phase detection circuit 9 detects a control current ic flowing through the control winding 4 of the two-phase servo motor 3 and an excitation current im flowing through the excitation winding 5.
This circuit detects the phase difference between the two and outputs a voltage proportional to the phase difference.

The flow velocity conversion circuit 10 is a circuit that converts the output voltage of the phase detection circuit 9 into a flow velocity and displays it. For example, when displaying the flow velocity with a meter, the simplest method is to use a voltmeter with a flow velocity scale. Bye.

To explain the operation of the above device assuming that the chair and impeller 3 are rotated in the direction of flow by the two-phase servo motor 2, the fluid in the flow path 1 is not flowing, that is, the flow velocity v
-O, the impeller 3 receives no rotational load due to fluid resistance and mechanical friction between the two-phase servo motor 2.
and is driven to the operating point P in FIG.

The rotation speed N corresponding to Rotate with.

The two-phase servo motor 2 has an internal impedance that changes in accordance with the slippage of the motor due to a load change corresponding to the flow velocity, and the internal impedance changes between the excitation current im flowing through the excitation winding 5 and the control current im flowing through the control winding 4. Change the phase difference.

This phase difference is a variable corresponding to the flow velocity, and as shown in FIG. 3, the phase difference θ0 is smaller than 1 (90°).

At this phase difference θ0, the output voltage of the phase detection circuit 9 is O
If it is adjusted so that the flow velocity value V displayed on the flow velocity conversion circuit 10 becomes O.

Next, when the fluid in the flow path 1 is flowing at the flow velocity v1, the rotational direction of the impeller 30 coincides with the flow direction, so the rotational load on the impeller 3 becomes lighter in proportion to the flow velocity ■1. .

As a result, the two-phase servo motor 2 rotates at an operating point P1 that outputs a rotational torque corresponding to the rotational load, and the internal impedance changes according to the rotational speed N1, that is, the slip of the motor, and the current flows to the excitation winding 5. Excitation current im
The phase difference between the control current IC flowing through the control winding 4 and the third
As shown in the figure, θ1 corresponds to the rotational speed N1.

Therefore, since the phase detection circuit 9 uses the phase difference θ0 as a reference phase and generates an output according to the phase difference from θ0 as described above, the output voltage at the flow velocity v1 has a voltage value proportional to θ0−θ.

The flow velocity conversion circuit 10 receives the output voltage of the phase detection circuit 9, converts the output voltage into a flow velocity, and displays the flow velocity V1 on a meter or the like.

As is clear from the above operation, the present invention can automatically measure the flow velocity from the phase change of the exciting current im of the two-phase servo motor.

In addition, although the above-mentioned example showed the case where the flow rate of the fluid flowing in the flow path 1 is determined, when determining the flow rate, it is sufficient to simply multiply the flow rate value by the pipe cross-sectional area of the flow path 1. For example, this can be easily done by changing the conversion coefficient of the flow rate conversion circuit 10.

As explained above, the present invention drives an impeller placed in a flow path one rotation by a two-phase servo motor, and detects a phase change in the excitation winding current of the two-phase servo motor that changes depending on the flow velocity of the fluid. Since the configuration determines the flow velocity, there is no effect on detection accuracy due to mechanical loss such as frictional resistance of the impeller bearing, and accurate measurement is possible even in the low flow velocity region, improving detection ability and detection accuracy. It has the remarkable effect of greatly improving both range.

Furthermore, the present invention allows the response time constant of the motor to be varied in various ways by arbitrarily selecting the slope of the characteristic curve of rotational torque and rotational speed of the two-phase servo motor, and to Optimal measurements can be performed.

In addition, two-phase servo motors do not have commutators or brushes, so there is no frictional resistance in the rotating parts other than the bearings, and because of the simple structure, there are fewer failures and stable measurement performance can be ensured over a long period of time. Since all transmission signals are alternating current, it has the advantage of being able to perform accurate measurements without being affected by drift, noise, etc.

In addition, if the device of the present invention is used as a device for measuring the amount of intake air in the manifold of an internal combustion engine such as a vehicle, the correlation between the detection output and the airflow velocity and the repeatability are good, so it can be used for small-load rotation such as idle link or low-speed operation. It is possible to accurately control the mixture ratio applied at the time, and furthermore, a supercharging effect can be expected due to the rotation of the impeller, and there are effects such as improving the thermal efficiency of the engine.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the device of the present invention, and FIG.
Figure 3 is an electrical circuit diagram of the device, and Figure 3 is a characteristic diagram of a two-phase servo motor. 1... R path, 2... Two-phase servo motor, 3... Impeller, 4... Control winding, 5...
... Excitation winding, 9 ... Phase detection circuit, 10
...Flow rate conversion circuit, im...Exciting current, ic...Control current.

Claims (1)

[Claims] 1 An impeller rotationally driven by a two-phase servo motor is arranged in a flow path, and a phase difference between a control current flowing through a control winding of the two-phase servo motor and an excitation current flowing through an excitation winding is detected. A flow velocity measuring device characterized by comprising a phase detection circuit that outputs a voltage proportional to a phase difference, and a flow velocity conversion circuit that converts the output voltage of the phase detection circuit into a flow velocity.