JP2001324481A - Apparatus for detecting air bubbles in liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To objectively comprehend air bubbles in a liquid. SOLUTION: A sonic wave transmitter 2 is arranged at one end part of a manifold 1, and a sonic wave receiver 3 is arranged to the other end part of the manifold 1 and sonic waves having different frequencies are transmitted from the sonic wave transmitter 2 to the sonic wave receiver 3, and the output of the sonic wave receiver 3 is inputted to a ratio operator 6 and air bubbles in the liquid are detected from the output of the ratio operator 6 via a display means 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a device for detecting bubbles in a liquid in a liquid circuit.

[0002]

2. Description of the Related Art In a liquid circuit represented by a hydraulic circuit, air bubbles such as air may be present in the liquid of a manifold constituting the liquid circuit. Bubbles generally have an adverse effect on the operation of equipment downstream therefrom, such as a malfunction, and are therefore required to be removed. This is called "air draining", and is usually performed by manually opening and closing an air drain valve provided on the manifold to allow a certain amount of liquid to flow out. On the other hand, in general-purpose hydraulic circuits, the "air removal" work is required only when setting up the equipment and when replacing or replacing components. Under normal operating conditions, new air bubbles may enter the hydraulic circuit. Is less.

In an internal combustion engine of a vehicle or the like, a fuel injection system for injecting an appropriate amount of high-pressure fuel into an intake system or a cylinder of the engine in a timely manner includes a fuel tank, a fuel filter, a fuel high-pressure pump,
It is composed of a manifold (or common rail), a plurality of injectors and a relief valve to form a liquid circuit. That is, the fuel high-pressure pump sucks up fuel from the fuel tank, removes dirt and moisture in the fuel with a fuel filter, compresses the fuel to a high pressure, sends it to the manifold, and sends the high-pressure fuel in the manifold to a plurality of injectors. And some are injected into the combustion chamber and consumed,
This is because the remainder is returned to the fuel tank and further released to the fuel tank by the operation of the relief valve.

[0004] Air trapped in the fuel tank due to swaying of the fuel at the time of relief or running, etc. is mixed into the fuel and becomes bubbles by the operation of the high-pressure fuel pump. The bubbles mixed into the fuel return to the fuel tank via the plurality of injectors and the relief valve, and circulate in the liquid circuit. Then, unlike the above-mentioned general-purpose hydraulic circuit, while the fuel high-pressure pump is operating, bubbles continue to be newly mixed into the liquid circuit.

[0005] If bubbles are mixed in the fuel sent to the injector, the fuel injection amount and the injection timing change from those in the normal state, and the output and exhaust gas characteristics change (generally deteriorate).

[0006]

Therefore, conventionally, the operation of the fuel high-pressure pump is stopped to allow the fuel to stand still, and the air vent valve is manually opened and closed to allow a certain amount of liquid to flow to the outside. Bubbles mixed with fuel in the manifold are removed (Japanese Patent Application Laid-Open Nos. 7-293393 and 8-189).
434), there is a problem that the amount of bubbles is not objectively grasped.

The present invention has been made for the purpose of solving such a problem of the prior art.

[0008]

Means for solving the above problems will be described below with reference to FIG. 1 corresponding to an embodiment.
explain. According to the present invention, a sound wave transmitter 2 is installed at one end of a manifold 1 and a sound wave receiver 3 is installed at the other end of the manifold 1, and sound waves having different frequencies are transmitted from the sound wave transmitter 2 to the sound wave receiver 3. The output of the sound wave receiver 3 is calculated by a ratio calculator 6
To detect bubbles in the liquid from the output of the ratio calculator 6 via the display means 7.

[0009] In the above configuration, the presence or absence of bubbles in the liquid and the amount of bubbles are displayed on the display means 7.

[0010]

FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, 1 is a manifold, 2 is a sound wave transmitter, 3 is a sound wave receiver, 4 is a filter, 5 is a rectifying / smoothing means, 6 is a ratio calculator, 7 is a display means, T is a fuel tank, and F is fuel. A filter, P is a fuel high-pressure pump, I is an injector, L is a relief valve, and K is a pipeline.

The sound wave transmitter 2 is fixed to one end of the manifold 1 and emits a sound wave f1 + f2 obtained by combining sound waves f1 and f2 having different frequencies toward the other end.
If air bubbles are mixed in the liquid in the manifold 1, sound waves (amplitude) propagated by the cushioning action and the irregular reflection action.
Is attenuated. The degree of the attenuation increases as the size of the bubble increases, as the amount of the bubble increases, and as the frequency increases. Therefore, a sound wave having two frequencies of f1 having a large frequency of sound attenuation and f2 having a small frequency is used. That is, the frequency is f1> f2. Preferably, f1 is a sound wave having a large attenuation in the size and amount of bubbles that affect the injection amount of an injector or the like, and f2 is a sound wave having a frequency with a small attenuation under the above conditions. Used.

The sound wave receiver 3 is fixed to the other end of the manifold 1, and receives sound waves f1 + f2 attenuated by bubbles. The output of the sound wave receiver 3 is provided to a filter 4.

The filter 4 is composed of a high-pass filter 4A that passes without being attenuated above the frequency f1, and a low-pass filter 4B that passes without being attenuated below the frequency f2. The combined sound wave f1 + f2 transmitted from the sound wave transmitter 2 is separated by the filter 4 into the sound wave f1 and the sound wave f2. Note that the filter 4 may be composed of two band filters having different cutoff frequencies.

The rectifying / smoothing means 5 rectifies and smoothes the output of the filter 4, and converts the oscillating sound waves into DC voltages Vf1, Vf2.
Convert to As shown in FIG. 2, the output of the rectifying / smoothing means 5 is lower at the high frequency f1 than at the low frequency f2, regardless of the amount of bubbles. That is, Vf1 <
Vf2. Further, as the amount of bubbles increases, the output difference between the two increases. The attenuation characteristics of the frequencies f1 and f2 are as follows:
Since it differs depending on the type, pressure, temperature, etc. of the liquid, it is obtained in advance by experiments and stored as data as shown in FIG.

The ratio calculator 6 receives the outputs Vf1 and Vf2 of the rectifying / smoothing means 5, and calculates and outputs the ratio Vf1 / Vf2. The reason for calculating the ratio is to avoid the influence of pressure fluctuation of the manifold 1 or mechanical noise other than the sound wave transmitter 2 and to make the degree of attenuation clearer.
The determination of bubbles in the liquid is based on the ratio V of the output of sound waves having different frequencies.
f1 / Vf2 is compared with a threshold to determine the presence or absence of bubbles and the amount of bubbles. FIG. 3 is a graph for obtaining the bubble amount from the calculated ratio value, and these are also obtained as experimental values under various conditions.

The display means 7 outputs the output Vf1 of the ratio calculator 6.
/ Vf2 is displayed in analog or digital form. Alternatively, the amount of air bubbles after starting the engine may be displayed as a magnification or a percentage based on the amount of air bubbles when the engine is stopped. Further, when the output Vf1 / Vf2 of the ratio calculator 6 falls below a certain value, a warning may be issued or the air removal valve may be electromagnetically operated.

The above is the case where the sound wave transmitter 2 is installed at one end of the manifold 1. However, the same effect can be obtained by using the noise generated by the operation of the engine as a sound source instead of the sound wave transmitter 2. Specifically, as shown in FIG. 1, the noise generated in the fuel high-pressure pump P is transmitted to the manifold 1 through the pipe K. In this case, the sound wave transmitter 2 is unnecessary.

Although the above description has been made with reference to a common rail and a manifold for fuel for a vehicle engine, the present invention is not limited to this, and a hydraulic circuit for lubricating oil or hydraulic oil may be used. Similar effects can be obtained in other pipelines and the like in which bubbles are mixed.

In the above description, the determination is made based on the ratio of the two frequencies, but the determination may be made based on the difference.

In the above description, two frequencies are combined to form one sound wave and transmitted and received by one transmitter and one receiver, but may be transmitted by separate transmitters and receivers. A split type transmitter that can transmit and receive two frequencies,
A receiver can also be used.

Further, in the above description, the transmission type and the receiver are provided at one end and the other end in the transmission type. However, it is also possible to provide the transmitter and the receiver only at one end.

[0022]

As described above, the present invention provides:
A sound wave transmitter is installed at one end of the manifold and a sound wave receiver is installed at the other end of the manifold, sound waves having different frequencies are transmitted from the sound wave transmitter to the sound wave receiver, and the output of the sound wave receiver is ratio-controlled. It is input to a calculator and detects bubbles in the liquid from the output of the ratio calculator via display means. Therefore, the bubbles in the liquid are displayed on the display means. Therefore, according to the present invention, it is possible to obtain an effect that the bubbles in the liquid can be objectively grasped.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between output, frequency and bubbles in liquid according to the present invention.

FIG. 3 is a diagram showing a relationship between an output of a ratio calculator according to the present invention and bubbles in a liquid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Manifold 2 Sound wave transmitter 3 Sound wave receiver 4 Filter 5 Rectification / smoothing means 6 Ratio calculator 7 Display means

Claims (7)

[Claims] 1. A sound wave transmitter is installed at one end of a manifold and a sound wave receiver is installed at the other end of the manifold, and sound waves having different frequencies are transmitted from the sound wave transmitter to the sound wave receiver. Liquid bubble detection device for inputting the output of the device to a ratio calculator and detecting bubbles in the liquid from the output of the ratio calculator via display means 2. The bubble detecting device according to claim 1, wherein the sound waves having different frequencies are formed by a combination of a high frequency having a large attenuation and a low frequency having a small attenuation. 3. The air bubble detection device according to claim 1, wherein the determination of air bubbles in the liquid is performed by comparing the ratio of the outputs of sound waves having different frequencies with a threshold value to determine the presence or absence of air bubbles and the amount of air bubbles. 4. The output of the sound wave receiver is inputted to a ratio calculator through two filters and a rectifying / smoothing means.
4. An apparatus for detecting bubbles in liquid according to any one of claims 1 to 3. 5. The air bubble detecting device according to claim 4, wherein the two filters are a low-pass filter and a high-pass filter. 6. The apparatus according to claim 4, wherein the two filters are bandpass filters. 7. A sound wave receiver is provided at the other end of the manifold toward one end of the manifold, and noise generated by operation of an engine is received by the sound wave receiver, and an output of the sound wave receiver is provided. From two different frequencies to a ratio calculator, and detects bubbles in the liquid from the output of the ratio calculator via display means.