JPH0377022A - Liquid level detecting device - Google Patents

Abstract

PURPOSE:To improve the detection accuracy of a liquid level by finding the liquid level from the electrostatic capacity between four couples of liquid level detection sensors which are dipped in the liquid at specific intervals in a front- rear and a right-left direction, and performing arithmetic processing. CONSTITUTION:The detecting device 1 consists of the liquid level detector 7, composed of the four couples of liquid level detecting sensors 2 - 5 having small-diameter cylindrical electrodes and large-diameter cylindrical electrodes concentrically and a circuit part 6, and an arithmetic unit (computer) 8. The liquid level detector 7 has the sensors 2 - 5 fixed on the reverse surface of a discoid base 9 while the parallelism between the sensors is held. Further, the sensors 2 and 4 which are positioned on a diagonal of a square are fitted to a fuel tank in the front-rear direction of a vehicle. The sensors 3 and 5 are therefore in the right-left direction of the vehicle. The arithmetic unit 8 finds liquid levels at the positions of the respective sensors 2 - 5 from a fre quency outputted by the circuit part 6 and operates the real liquid level from the simple mean value of the liquid levels in the front-rear and right-left directions and the tilt angle of the liquid surface by composition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid level detection device suitable for detecting a liquid level in a fuel tank.

[Prior art and its section B] Conventionally, in order to detect the liquid level of fuel stored in a fuel tank, a float type liquid level detection device equipped with a float that moves according to the displacement of the liquid level, Alternatively, there is a capacitive liquid level detection device that determines the height of the fuel level from the capacitance formed between a pair of electrodes immersed in the fuel.

However, such conventional liquid level detection devices are unable to detect the correct liquid level when the vehicle is tilted or when the liquid level fluctuates due to acceleration or deceleration.

The present invention has been made based on the above-mentioned circumstances, and an object thereof is to provide a liquid level detection device with improved accuracy in detecting liquid level.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides at least three pairs of electrodes immersed in a liquid at predetermined intervals in the front-rear direction and left-right direction, and multiple pairs thereof. The technical means includes an arithmetic device that calculates the true liquid level height based on each liquid level height determined from the capacitance formed between the electrodes. do.

[Operations and Effects of the Invention] The liquid level detection device of the present invention having the above configuration, for example, determines the liquid level height of each of the multiple pairs of electrodes from the capacitance formed between the electrodes disposed in the front and back direction, The simple average value of the liquid level height and the inclination angle of the liquid level in the front-rear direction are calculated. Similarly, each liquid level height is determined from the capacitance between multiple pairs of electrodes arranged in the left and right direction, and the simple average value of the liquid level height and the slope of the liquid level in the left and right direction are calculated. Calculate the angle.

Then, the true liquid level height is calculated by combining the simple average value of the liquid level heights obtained in the front-rear direction and the left-right direction and the inclination angle of the liquid level.

As described above, in the present invention, by providing at least three pairs of electrodes at predetermined intervals in the front-rear direction and left-right direction, the liquid level can be maintained even if the liquid tank storing the liquid is tilted. Since it can be specified, the true liquid level height can be detected with high accuracy.

[Embodiment] Next, a liquid level detection device of the present invention will be explained based on an embodiment shown in the drawings.

FIG. 1 is a block diagram showing the configuration of the liquid level detection device.

The liquid level detection device 1 of this embodiment includes four liquid level detection sensors (
It is composed of sensors 2 to 5 (hereinafter referred to as sensors), a liquid level detector 7 connected to a circuit section 6, and a computer 8.

The liquid level detector 7 includes four sensors 2 as shown in FIG.
5 are fixed to the lower surface of the disc-shaped base 9 while maintaining parallelism between the respective sensors. Each of the sensors 2 to 5 is attached to the base 9 so as to be located at each vertex of a square, as shown in FIG. Note that FIG. 2 is a side view of the liquid level detector 7, and FIG. 3 is a view from A in FIG. 2.

As shown in FIG.
111 are arranged concentrically.

The circuit section 6 is assembled on the upper surface of the base 9, converts the capacitance measured by each sensor 2 to 5 into a frequency, and is composed of a frequency conversion circuit 6a and a frequency division circuit 6b.

This liquid level detector 7 is located on the diagonal of the square.
The sensor 2 and the third sensor 4 are attached to a fuel tank (not shown) so as to be in the longitudinal direction (traveling direction) of the vehicle. Therefore, the second sensor 3 and the fourth sensor 5 are located in the left and right direction of the vehicle.

The calculation device 8 calculates the liquid level height at each sensor 2 to 5 position from the frequency output from the circuit section 6, and calculates the true liquid level height from each liquid level height.

An example of the operation of this arithmetic device 8 will be explained based on the flowchart shown in FIG.

First, in step S1, each frequency from the circuit section 6 is input.

In step S2, the liquid level height at the position of each sensor 2 to 5 is determined based on each frequency input in step S1.

In step S3, it is determined whether the liquid level heights obtained in step S2 are on the same plane.

If the determination result in step S3 is No, it is determined that the liquid level is fluctuating, and the process returns to step S1.

If the judgment result in step S3 is YES, step S
4, the simple average value of each liquid level height at the first sensor 2 and the third sensor 4, and the second sensor 3 and the fourth sensor 5, and the inclination angle of the liquid level are calculated.

In step S5, a correction value is calculated from the static characteristics that are known in advance based on various conditions such as the shape of the fuel tank and the arrangement of the sensors 2 to 5 in the fuel tank, and the inclination angle of the liquid level calculated in step S3. .

In step S6, the true liquid level height is calculated by combining the simple average value of each liquid level height in the front-back direction and the left-right direction and the correction value calculated in step S5.

In step S1, the average value of the liquid level heights continuously calculated during a certain period of time is determined.

Next, the operation of this embodiment will be explained based on FIG. 6.

Note that FIG. 6 shows the state of each sensor (the first sensor 2 and the third sensor 4) and the liquid level during tilting (tilting in the traveling direction).

As shown in FIG. 6, when considering the inclination of the vehicle in the longitudinal direction, the first sensor 2 and the third sensor arranged in the longitudinal direction
Based on the liquid level heights Hl and H3 at sensor 4 and the pitch between both sensors, the simple average (i!'(H
0 and the liquid level inclination angle α in the backward direction.

Also, the shape of the fuel tank, each sensor 2 in the fuel tank,
The correction value ΔH is calculated from the static characteristics that are known in advance based on various conditions such as the arrangement of parts 5 and the liquid level inclination angle α.

Then, the true liquid level height H is determined from the simple average value HO and the correction value ΔH.

Furthermore, by calculating the average within a certain period of time, the true liquid level height can be determined with high accuracy.

Even when tilting in the left-right direction, the true liquid level height can be determined in the same manner as in the case of tilting in the front-rear direction described above.

Therefore, no matter how the vehicle is tilted, the true liquid level height can be determined by calculating the simple average value of each liquid level height determined in the longitudinal direction and left/right direction, and the correction value. be able to.

In addition, since the liquid level state can be detected even when it is stationary or when it is swinging, it is possible to improve the averaging accuracy by eliminating invalid data.

(Modification) The calculation process by the calculation device 8 for determining the liquid level height shown in this embodiment is an example, and the calculation process is not limited to this calculation process.

In this example, the number of sensors is four, but it is not necessary to limit the number to four, and three or five or more sensors may be used. However, with three sensors, it is not possible to detect the liquid part oscillation state due to acceleration and deceleration. However, since it is possible to specify the liquid level when tilting, accuracy can be improved over current technology.

Further, each sensor 2 to 5 has a configuration in which a small diameter cylindrical electrode 10 and a large diameter cylindrical electrode 11 are arranged concentrically, but for example,
A structure in which flat electrodes are arranged in parallel may also be used.

Although the liquid level height was determined by converting the capacitance measured by each sensor 2 to 5 into a frequency, it may be converted into a current value or a voltage value.

In the operation of the arithmetic unit 8, if the liquid level heights determined in step S2 are not on the same plane, the input data is invalidated and the process returns to step S1, but the previous valid data is carried over as is. You may do so.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the liquid level detection device, Fig. 2 is a side view of the liquid level detector, Fig. 3 is A homeland in Fig. 2,
The figure is a perspective view of the electrodes constituting the sensor, FIG. 5 is a flowchart showing the operation of the arithmetic unit, and FIG. 6 is a diagram showing the state of the sensor and the liquid level during tilting. In the figure 1...Liquid level detection device 8...Arithmetic device 10...
Small diameter cylindrical electrode 11...Large diameter cylindrical electrode Figure 5

Claims (1)

[Claims] 1) (a) at least three pairs of electrodes immersed in a liquid with predetermined intervals in the front-rear direction and left-right direction, and (b) configured between each pair of electrodes. A liquid level detection device comprising: a calculating device that calculates the true liquid level height based on each liquid level height by determining the liquid level height from the capacitance of each liquid level.