JPH09152365A - Liquid level detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the degree of freedom in design without limit of tank shape, meet various tanks having different shapes and prevent the entry of liquid by providing a differential detecting part outside a tank, connecting the detecting part and tank with each other by a coupling tube, leading a coupling tube from the bottom of a hydraulic chamber, and forming an air layer. SOLUTION: A differential sensor 2 is connected with a coupling tube 4 led from the upper side of a fuel tank 4. A pressure sensing element 24 is fixed on a pedestal 23 in the sensor 2. The pedestal 23 is provided with a hydraulic leading passage 25 connecting with the tube 3 on its lower side, and the liquid pressure within the tank 1 is introduced into a hydraulic chamber 21. The sensor 2 is at the same level as the bottom of the tank 1, and a coupling tube 3 is led downward from the bottom of the tank 1, bent on the midway, and further bent upward to be connected to the tube 25 from its lower side. Therefore, an air layer 31 is securely formed in the end part of the chamber 21, so that a fuel 11 hardly enters the chamber 21. The upper part in the element 24 becomes a gas pressure chamber 22, and when the tube 4 is connected to a gas pressure leading passage 26, the pressure of a gas 12 within the tank 1 is led to the element 24. The element 24 outputs an electric signal corresponding to a difference between liquid pressure and gas pressure, as a result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device used for a fuel gauge of an automobile.

[0002]

2. Description of the Related Art There is a liquid level detecting device which detects the liquid level of a fuel tank by using a pressure sensor in order to know the remaining amount of fuel in a vehicle fuel tank. The pressure sensor is usually fixed to the outer wall of the fuel tank as seen in Japanese Utility Model Laid-Open No. 62-115629, and the liquid pressure of the fuel is provided in one of the sensors partitioned into the two chambers and the atmospheric pressure is provided in the other. Is introduced and the liquid surface is detected by these differential pressures.

[0003]

However, in the method of directly fixing the sensor to the outer wall of the tank in this way, since the tank needs a large number of flat portions, the degree of freedom in the shape of the tank is limited, and there are restrictions in design. Was becoming. In order to prevent the fuel from directly touching the sensor, when the sensor is fixed on the upper surface of the tank, in order to introduce the hydraulic pressure of the fuel existing in the lower part of the tank into the sensor, a pipe with high rigidity with vibration resistance is used. It is necessary to use it, and there is a problem that the structure and mounting are complicated.

In addition, in order to further improve the detection accuracy of the sensor, when the liquid level of the fuel tank is detected from the pressure difference between the fuel liquid pressure and the gas pressure in the fuel tank, the gas pressure in the tank is detected by the sensor. The need for installation within makes it more complex in structure and installation. Further, there is a problem in versatility such that it is necessary to change the device structure according to the size and shape of the tank.

Therefore, according to the present invention, the degree of freedom in designing the fuel tank is improved, the structure is simplified to facilitate the manufacture and installation, the versatility is enhanced, and the reliability and detection accuracy of the apparatus are improved. The purpose is to let.

[0006]

As shown in FIG. 1, a liquid level detecting device according to a first aspect of the present invention is a tank 1 for containing a liquid 11.
A hydraulic chamber 21 communicating with the hydraulic pressure of the liquid 11
And a gas pressure chamber 22 into which the reference gas pressure is introduced. The differential pressure detection unit 2 is installed outside the tank 1, and a connecting pipe 3 extending from the bottom of the tank 1 is connected to the hydraulic chamber 21 from below so that the hydraulic chamber of the connecting pipe 3 is connected. An air layer 31 is formed at the end on the 21 side.

In the above structure, a hydraulic pressure is introduced into the hydraulic chamber 21 of the differential pressure detecting section 2 through the air layer 31, and a reference gas such as atmospheric pressure is introduced into the gas pressure chamber 22. It The liquid level height can be detected by detecting these differential pressures with the differential pressure detection unit 2.

At this time, since the differential pressure detector 2 is provided outside the tank 1 and the two are connected by the connecting pipe 3, the tank 1
The shape is not restricted and the degree of freedom in design is improved. In addition, since it is possible to cope with tanks having different sizes and shapes by changing the length of the connecting pipe 3, etc., it is excellent in versatility.
Cost can be reduced by sharing the device. further,
Since the connecting pipe 3 communicating with the tank 1 is connected to the hydraulic chamber 21 from below and the air layer 31 is formed at the connecting end, the liquid 11 does not enter the hydraulic chamber 21. Therefore, the pressure sensitive portion is not adversely affected, and the reliability is improved.

It is preferable that the differential pressure detector 2 is installed at substantially the same position as the bottom of the tank 1 (claim 2).
Since the differential pressure detection unit 2 detects the liquid pressure of the liquid 11 located above the installation position, by placing it at substantially the same height as the bottom of the tank 1, the detection accuracy is further improved. .

Further, the gas pressure chamber 2 of the differential pressure detector 2
2 may be connected to the upper portion of the tank 1 by a connecting pipe 4, and the gas pressure in the tank 1 may be introduced into the gas pressure chamber 22 (claim 3). The gas pressure in the tank 1 increases and decreases due to temperature changes, fuel consumption, etc., and the liquid pressure introduced into the hydraulic pressure chamber 21 also changes accordingly. Therefore, the liquid level height may not be accurately detected. However, the gas pressure chamber 22
By introducing the gas pressure in the tank 1 to, the fluctuation of the pressure can be canceled, and more accurate liquid level detection can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall configuration of a liquid level detecting device of the present invention. In FIG. 1A, reference numeral 1 is a fuel tank, and a differential pressure sensor 2 serving as a differential pressure detection unit is arranged close to the outside of the fuel tank. A connecting pipe 3 extending from the bottom surface of the fuel tank 1 of the automobile is connected to the differential pressure sensor 2, and
A connecting pipe 4 extending from the upper surface of the tank 1 is connected.

As shown in FIG. 1B, the differential pressure sensor 2 has a pressure sensitive element 24 which is supported and fixed inside on a pedestal 23.
Having. A hydraulic pressure introducing passage 25 to which the connecting pipe 3 is connected is provided below the pedestal 23, and the hydraulic pressure introducing passage 25 is provided.
The hydraulic pressure in the tank 1 is introduced into the hydraulic chamber 21 provided in the pedestal 23 via the above. here,
The differential pressure sensor 2 is installed at substantially the same height as the bottom surface of the tank 1 (FIG. 1 (a)), and the connecting pipe 3 is directed downward from the bottom surface of the tank 1 and then the differential pressure sensor on the way. It bends in the direction of the pressure sensor 2 and further bends upward to connect to the hydraulic pressure introducing passage 25 from below. Then, the connecting pipe 3
An air layer 31 is always formed at the end of the liquid pressure chamber 21 side, and the fuel 11 does not enter the liquid pressure chamber 21.

On the other hand, the space above the element 24 forms a gas pressure chamber 22, and a gas pressure introducing passage 26 provided above the gas pressure chamber 22.
The pressure of the gas 12 in the fuel tank 1 is introduced by connecting the connecting pipe 4 to the. The connecting pipe 4 is not limited to the upper surface of the tank 1 and may be connected to any place where the fuel gas 12 surely exists.

Thus, the connecting pipe 3 is connected to the hydraulic chamber 21.
As a result, the liquid pressure of the fuel 11 is introduced into the gas pressure chamber 22 through the connecting pipe 4 and the gas pressure in the tank 1 is introduced.
4 outputs an electric signal according to the differential pressure between the liquid pressure and the gas pressure. The pressure sensitive element 24 is connected to the terminal 28 by a wire 27 (FIG. 1 (b)).
The output of 4 is taken out through the wire 27 and the terminal 28 and is input to the drive circuit 5 (see FIG. 1).
(A)). The drive circuit 5 drives the meter 6 according to the differential pressure-residual amount value as shown in FIG. 2, and displays the liquid level height, that is, the remaining fuel amount.

According to the above construction, the differential pressure sensor 2 only needs to be provided outside the tank 1 and connected to the upper and lower surfaces of the tank 1 by the connecting pipes 3 and 4, and the liquid level can be easily detected with a simple structure. You can At this time, the tank 1 does not necessarily have a flat shape, so that the shape of the tank is not restricted, and the degree of freedom in design is improved. Further, it can be attached to various tanks having different sizes and shapes simply by changing the lengths of the connecting pipes 3 and 4, and the versatility is high. Therefore, it is not necessary to change the device structure according to the shape of the tank, and the cost can be reduced by sharing the device. Moreover, the air layer 31 is always provided at the connection end of the differential pressure sensor 2 and the connecting pipe 3 communicating with the tank 1.
Since the structure is formed, the fuel 11 does not enter the inside of the hydraulic chamber 21. Therefore, the pressure-sensitive element does not come into contact with the fuel to be damaged, and the reliability is improved.

Here, the pressure in the tank 1 rises with time as shown in FIG. 3, and when it reaches a certain pressure, the pressure regulating valve opens and begins to decrease, and when the valve closes it begins to rise again.
As described above, since the pressure in the tank 1 is fluctuating, it is necessary to cancel the fluctuation in the pressure in the tank in order to accurately know the remaining amount of fuel, that is, the liquid level height. In the above configuration, since the differential pressure sensor 2 is connected to the upper surface of the tank 1 by the connecting pipe 4 so that the gas pressure in the tank 1 is introduced, the pressure proportional to the liquid surface height can always be output. it can. Further, since the differential pressure sensor 2 is arranged at substantially the same height as the bottom surface of the tank 1, the hydraulic pressure introduced into the hydraulic chamber 21 matches the actual hydraulic pressure of the fuel in the tank 1. Thus, the remaining fuel amount can be detected more accurately, and the detection accuracy is improved.

When the accuracy of the remaining amount detection is rough, the connecting pipe 4 is not provided, the gas pressure introducing passage 26 is opened to the atmosphere, and the atmosphere is introduced to the upper surface of the pressure sensitive element 24, so that the atmosphere and the liquid are discharged. The pressure difference from the pressure may be detected. Similarly, when the remaining amount is measured only when the pressure inside the tank 1 is constant or under a certain condition, the connection pipe 4 may not be provided. Further, the height of the differential pressure sensor 2 does not necessarily have to match the bottom surface of the tank 1, and if the differential pressure sensor 2 is installed at a position higher than the bottom surface of the tank 1, the air layer 31 will always remain, so that the intrusion of fuel is ensured. It can be prevented.

[Brief description of the drawings]

FIG. 1 (a) is an overall configuration diagram of a liquid level detection device of the present invention, and FIG. 1 (b) is an overall sectional view of a differential pressure sensor.

FIG. 2 is a diagram showing a relationship between tank internal pressure and time.

FIG. 3 is a diagram showing a relationship between a differential pressure sensor output and a display of a fuel gauge.

[Explanation of symbols]

 1 Fuel Tank 11 Fuel (Liquid) 12 Tank Gas 2 Differential Pressure Sensor (Differential Pressure Detection Section) 21 Hydraulic Pressure Chamber 22 Gas Pressure Chamber 23 Pedestal 24 Pressure Sensing Element 25 Liquid Pressure Introducing Path 26 Gas Pressure Introducing Path 27 Wire 28 Terminal 3 connecting pipe 31 air layer 4 connecting pipe 5 drive circuit 6 instrument

Claims (3)

[Claims] 1. A differential pressure detecting section, which is in communication with a tank containing a liquid and has a hydraulic pressure chamber into which the hydraulic pressure of the liquid is introduced, and a gas pressure chamber into which a reference gas pressure is introduced, The differential pressure detector is installed outside the tank, and a connecting pipe extending from the bottom of the tank is connected to the hydraulic chamber from below, and an air layer is formed at the end of the connecting pipe on the hydraulic chamber side. The liquid level detecting device is characterized in that the liquid level is detected from the differential pressure between the liquid pressure and the gas pressure introduced into the hydraulic chamber via the air layer. . 2. The liquid level detection device according to claim 1, wherein the differential pressure detection unit is installed at substantially the same position as the bottom of the tank. 3. The gas pressure chamber of the differential pressure detector is connected to the upper portion of the tank by a connecting pipe so that the gas pressure in the tank is introduced into the gas pressure chamber. 2. The liquid level detection device according to 2.