JPH0349373B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an ultrasonic flowmeter that allows ultrasonic waves to pass through multiple locations in a fluid flowing in a flow pipe and measures the flow rate of the fluid from the difference in propagation time. It is used for measuring the air intake amount of internal combustion engines.

(Prior art) Conventionally, so-called ultrasonic technology involves emitting ultrasonic waves to a fluid such as gas or liquid flowing in a flow pipe, and calculating the flow velocity of the fluid from the difference in propagation time to determine the fluid flow rate. Sonic flowmeters are widely known (for example, Japanese Patent Application Laid-open No. 1964-23-1982).

FIG. 3 is a cross-sectional view of a conventional ultrasonic flowmeter and a block diagram of an associated electrical circuit.

In the figure, 1 is a channel pipe through which fluid passes, 4 is an ultrasonic transmitter that emits ultrasonic waves toward the fluid, and 5
a, 5b are receivers, 6 is an adjustment screw for adjusting the position of the receiver 5b, 7, 7a, 7b are lead wires, 8 is a rectifier plate, 9 is a bypass, 10 is a division flow adjustment screw,
Reference numeral 11 denotes a sound absorbing lining provided on the inner wall of the flow pipe 1.

In addition, the electric circuit in the figure includes a transmitting circuit 20,
Amplifiers 21a, 21b, waveform shapers 22a, 22
b, phase shifters 23a and 23b that control the phase, a phase comparator 24, and an integrator 25.

In such an ultrasonic flowmeter, two receivers 5a and 5b at different positions receive ultrasonic waves emitted from an ultrasonic transmitter 4, amplify and compare the phases, and transmit the ultrasonic waves to the main flow pipe 1. The flow rate of the fluid flowing through it is calculated.

For this purpose, the ultrasonic transmitter 4 is connected to the receiver 5a,
5b, and it is necessary to arrange it perpendicularly to the side surface of the flow path pipe 1.

Furthermore, some of the ultrasonic waves emitted from the ultrasonic transmitter 4 reach the receivers 5a and 5b directly, while others reach the receivers after being reflected from the inner wall of the channel tube 1. In order to prevent the latter, the ultrasonic waves are A sound absorbing lining 11 is attached to the inner wall of the pipe 1.

However, in the conventional ultrasonic flowmeter described above, in order to improve measurement accuracy in the case of a low flow rate, the inner diameter of the flow pipe 1 is made thinner, and the ultrasonic transmitter 4 and the receiver 5a are , 5b needed to be increased.

Ultrasonic transmitters generally have high directivity and are structured so that the sound pressure of ultrasound waves traveling in the vertical direction from the vibration surface is highest. The ultrasonic waves that reach the area have poor directivity and are not used in the most effective range.

Therefore, it has the strongest directivity (highest sound pressure)
Ultrasonic waves within this range are absorbed by the sound-absorbing lining 11 provided on the inner wall of the flow pipe 1, and the difference in level between the directly received ultrasonic waves and the reflected ultrasonic waves that are received becomes small, making measurement difficult. There was a problem with the accuracy being poor.

Therefore, in such an ultrasonic flowmeter, in order to improve the measurement accuracy in the case of low flow rate, it is necessary to reduce the inner diameter of the flow pipe 1, and also to reduce the inner diameter of the ultrasonic transmitter 4, receiver 5a, There was also a problem in that it was structurally difficult to increase the distance between it and 5b.

(Problems to be Solved by the Invention) The present invention was invented as a result of intensive studies to solve the problems of the prior art described above.

Therefore, an object of the present invention is to provide an ultrasonic flowmeter that has excellent measurement accuracy even when the fluid flow rate is low, improves the signal-to-noise ratio, and has a small pressure drop in the pipe of the fluid.

(Means for Solving the Problems) That is, the ultrasonic flowmeter of the present invention includes a flow pipe through which a fluid passes, an ultrasonic transmitter disposed on the side of the flow pipe, and a a prism-shaped reflector that receives emitted ultrasonic waves at a position perpendicularly opposed to the ultrasonic transmitter and reflects them in multiple directions; at least one pair of receivers that receive the ultrasonic waves reflected from the reflector; The present invention is characterized in that the ultrasonic wave passing surface of the flow path tube is provided with a transparent foil that blocks fluid and allows ultrasonic waves to pass through.

In the ultrasonic flowmeter of the present invention, the reflector is arranged at a position perpendicularly facing the transmitter, that is, at a position where it receives the ultrasonic waves emitted from the ultrasonic transmitter with the best directivity.

As the reflector, a prism-type one that can reflect ultrasonic waves in multiple directions, preferably two directions is used.

Further, as the transmission foil disposed on the ultrasonic wave passing surface of the channel tube, it is preferable to use a tightly woven cloth or the like.

(Example) Hereinafter, an example of the ultrasonic flowmeter of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the ultrasonic flowmeter of the present invention.

That is, in FIG. 1, an ultrasonic transmitter (hereinafter simply referred to as an transmitter) 4 is disposed on one side of a flow path pipe 1 through which a fluid such as gas passes, and a flow path On the other side of the tube 1, receivers 5a and 5b for receiving ultrasonic waves are arranged at equally spaced positions upstream and downstream of the transmitter 4, respectively.

At positions vertically facing the transmitter 4, there are receivers 5a, 5 that efficiently receive the ultrasonic waves emitted from the transmitter 4 in the most directional range.
A prism-shaped reflector is arranged to propagate to b, and further on the receivers 5a, 5b side of the flow pipe 1,
An adjustment screw 6 is provided for equally adjusting the propagation distance of the ultrasonic waves.

The ultrasonic waves transmitted from the transmitter 4 upon receiving the electric signal from the transmitter circuit 20 are transmitted to the receiver 5.
a, 5b, and the received signals are amplified by amplifiers 21a, 21b, waveform shaped by waveform shapers 22a, 22b, and then processed by a phase comparator 24 and an integrator 25 to convert fluid (gas, etc.) The flow rate is calculated and output. .

The transmission foils 3, 3a, and 3b are made of a material (such as fine cloth) that allows ultrasonic waves to pass through but can block fluids, and they are made of a material that can pass ultrasonic waves but block fluids (for example, fine-mesh cloth, etc.). (Places corresponding to receivers 5a and 5b)
It is located in

Next, the operation of the ultrasonic flowmeter of the present invention will be explained.

First, when an electric signal is sent from the transmitter circuit 20 to the transmitter 4, this electric signal vibrates resonantly at the resonant frequency of the transmitter 4, is converted into an ultrasonic wave, and is transmitted from the transmitter 4.

The ultrasonic waves emitted from the transmitter 4 are reflected by the prism-shaped reflector 2 toward the receivers 5a and 5b.

At this time, the ultrasonic wave is reflected from the angle with the highest level of directivity by the reflector 2 placed perpendicularly to the transmitter 4, so that the ultrasonic wave reaches the receivers 5a and 5b. The sound pressure level of the sound waves is strong and the reception efficiency is excellent.

In addition, in order to improve measurement accuracy in the case of low flow rates, the inner diameter of the flow path pipe 1 may be made smaller, and the transmitter 4 may be made smaller.
Even when the distance between the reflector 2 and the receivers 5a and 5b is increased, high accuracy can be obtained by appropriately setting the angle of the reflector 2.

Next, the ultrasonic waves simultaneously transmitted from the transmitter 4 to the upstream and downstream sides of the flow pipe 1 are transmitted to the receivers 5a and 5b with a time difference proportional to the flow rate of the fluid passing through the flow pipe 1. and reach it.

The received signals from the receivers 5a and 5b are
Via amplifiers 21a and 21b, waveform shaper 22
a, 22b, the waveform is shaped, and then the phase comparator 2
By detecting the propagation time difference in step 4 and calculating it in integrator 25, the flow rate of the fluid (gas, etc.) is output.

Note that by providing the transparent foils 3, 3a, and 3b, the fluid flow is smoothed and the pressure loss within the flow path pipe 1 is reduced.

FIG. 2 shows a second embodiment of the ultrasonic flowmeter of the present invention.

In this second embodiment, the transmitter 4 and the pair of receivers 5a and 5b are arranged on the same side of the flow pipe 1, and the reflector 2 is arranged on the other side of the flow pipe 1. However, this embodiment is different from the first embodiment described above.

That is, the ultrasonic waves emitted from the transmitter 4 on one side of the flow pipe 1 are transmitted to the vertically opposing position of the transmitter 4 on the other side of the flow pipe 1, that is, the position with the strongest directivity. The signal is reflected in two directions by a reflector 2 placed on the same side as the transmitter 4, and is received by receivers 5a and 5b placed on the same side as the transmitter 4.

In addition, in the ultrasonic flowmeter of the present invention, it is also possible to arrange the transmitter and the receiver outside the outer wall of the flow pipe.

(Effects of the Invention) As explained above, the ultrasonic flowmeter of the present invention exhibits the following excellent effects and is extremely useful for applications such as measuring the air intake amount of internal combustion engines. It is.

(b) A prism-shaped reflector is placed at the position vertically facing the transmitter and has the strongest sound pressure directivity to reflect the ultrasonic waves, so the ultrasonic reception sensitivity of the receiver is high, especially for low The accuracy of fluid measurement of flow rate can be increased.

(b) Ultrasonic waves in a range with strong sound pressure directivity can be received, so even if the inner diameter of the flow pipe is made smaller or the distance between the transmitter and receiver is increased, The reception sensitivity is high and the SN ratio can be improved.

(c) By using a transparent foil on the ultrasonic wave passing surface of the flow pipe, fluid flow becomes smooth and pressure loss within the flow pipe is reduced.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view and a block diagram of the attached electric circuit showing the first embodiment of the ultrasonic flowmeter of the present invention, Fig. 2 is a cross-sectional view of the second embodiment, and Fig. 3 is a conventional ultrasonic flowmeter. FIG. 3 is a cross-sectional view of the flowmeter and a block diagram of the attached electric circuit. 1... Channel pipe, 2... Reflector, 3, 3a, 3b
... Transparent foil, 4 ... Transmitter, 5a, 5b ... Receiver, 21a, 21b ... Amplifier, 22a, 22b
... Waveform adjuster, 24 ... Phase comparator, 25 ...
Integrator.

Claims (1)

[Claims] 1 A flow pipe through which a fluid passes, an ultrasonic transmitter placed on the side of the flow pipe, and an ultrasonic transmitter that transmits the ultrasonic waves from the ultrasonic transmitter at a position perpendicularly facing the ultrasonic transmitter. a prism-type reflector that receives the ultrasonic waves and reflects the ultrasonic waves in a plurality of directions; and at least a pair of receivers that receive the ultrasonic waves reflected from the reflector; An ultrasonic flowmeter characterized by being equipped with a transparent foil that blocks fluid and allows ultrasonic waves to pass through.