JP4225468B2 - Fuel level detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a remaining fuel amount detection device, and more particularly to a remaining fuel amount detection device that can accurately detect the remaining amount even when the remaining amount of fuel in a fuel tank is extremely small.
[0002]
[Prior art]
Conventionally, a float arm type device has been used as a fuel remaining amount detection device. However, there are problems such as that it cannot be used for a fuel tank having a structure in which it is difficult to secure a space for the arm supporting the float to move, and that the arm may be difficult to move due to the inclination of the fuel liquid level. Therefore, various fuel remaining amount sensors that do not require an arm have been conceived by combining a float having a permanent magnet and a magnetic sensor such as a Hall element.
[0003]
For example, Japanese Patent Laid-Open No. 9-120808 discloses a device in which a fuel gauge composed of a float having a permanent magnet and a Hall element is integrated in a fuel pump. In addition, Japanese Utility Model Publication No. 2-41544 discloses a fuel liquid level in which a support column in which a plurality of reed switches are vertically arranged is erected in a fuel tank, and a float with a magnet is slidably fitted to the support column. A sensor is disclosed.
[0004]
[Problems to be solved by the invention]
Conventional fuel remaining amount sensors have insufficient detection accuracy, and it has been difficult to display an accurate remaining amount particularly when the amount of fuel is reduced to such an extent that the bottom surface of the float contacts the bottom surface of the fuel tank.
[0005]
An object of the present invention is to provide a fuel remaining amount detecting device capable of accurately displaying the remaining amount even when the amount of fuel in the fuel tank is extremely small.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a remaining fuel amount detection device having a float with a magnet provided in a float chamber and a magnetic sensor for detecting the remaining fuel amount in the fuel tank based on the height of the float. The first feature resides in that the float chamber is provided inside the fuel tank so that the fuel in the fuel tank can flow in and out, while the magnetic sensor is disposed below the bottom of the fuel tank.
[0007]
According to the first feature, since the magnetic sensor is provided further below the bottom of the fuel tank, the remaining amount detection output is generated until the remaining amount of fuel becomes extremely low and the bottom reaches the float. Can do.
[0008]
In addition, the present invention has a second feature in that the float chamber has an injection hole for fuel inflow and outflow and a filter disposed adjacent to the injection hole. According to the second feature, the fuel flows in and out of the float chamber through the filter and the ejection hole. Therefore, by setting the shape and the number of the filters and the ejection holes, the inflow and outflow amounts of the fuel can be adjusted so that the fuel level in the float chamber does not fluctuate rapidly.
[0009]
According to the present invention, the magnetic sensor includes a bridge circuit including a set of saturable coils for obtaining a differential output, and a logarithmic amplifier connected to the output side of the bridge circuit. There is a third feature in that the set of saturable coils are arranged horizontally, and the distance between one of the saturable coils and the magnet is different from the distance between the other and the magnet. .
[0010]
According to the third feature, even when a magnetic field in the same direction acts on a set of saturable coils, a differential output is generated due to the difference in distance. The differential output is an exponential output with respect to the distance between the magnetic sensor and the magnet, and the remaining fuel amount is detected linearly by a logarithmic amplifier.
[0011]
Furthermore, the present invention has a fourth feature in that irregularities are formed on the surface of the float. According to the 4th characteristic, since the surface which has an unevenness | corrugation opposes a float chamber inner wall, a mutual contact area becomes small and it can slide smoothly even if the gap of a float and a float chamber is filled. Therefore, the detection accuracy is improved, and it is possible to prevent the float from moving due to dust clogging.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a fuel tank of a motorcycle to which the fuel detection device of the present invention is applied, FIG. 2 is a front cross-sectional view of a fuel remaining amount detection device, FIG. 3 is a right cross-sectional view, and FIG. FIG. 5 is a cross-sectional view of the main part of the float part. 5 is a cross-sectional view taken along the line AA in FIG. In FIG. 1, a fuel tank 1 is made of synthetic resin, and a fuel remaining amount detection device 3 and a fuel pump 4 are provided on a bottom plate 2. The bottom plate 2 is attached to a frame body 5 fixed to the bottom surface of the fuel tank 1 by means of welding or adhesion using bolts 6. A coupler 7 provided at the tip of a hose connected to a fuel injection valve (not shown) is connected to the discharge port 4a of the fuel pump 4. As the fuel pump 4, since a conventionally known fuel supply pump can be used, detailed description thereof is omitted.
[0013]
1 to 5, the remaining fuel amount detection device 3 includes a float portion 8 and a sensor portion 9. The float unit 8 includes a float 10 and a container that forms a vertically long float chamber that accommodates the float 10, that is, a float case 80. By fixing the float case 80 to the bottom plate 2, the remaining fuel amount detection device 3 can be supported on the bottom of the fuel tank 1. The float case 80 is provided with jets or ejection holes 11 (see FIGS. 2 and 3) and 12 (see FIG. 5) on the upper and lower side surfaces, respectively. The fuel in the fuel tank 1 is introduced into the float case 80 through these jets 11 and 12 so that the fuel level in the float case 80 can represent the remaining amount of fuel in the fuel tank 1. Due to the acceleration / deceleration of the motorcycle, the fuel in the fuel tank 1 mounted on the motorcycle sways violently in the fuel tank 1. The diameters of the jets 11 and 12 are set so that the vibration does not directly reach the float case 80, that is, the fuel does not suddenly enter the float case 80 and is not discharged from the float case 80.
[0014]
Filters 13 and 14 are provided on the front surface, that is, outside of the jets 11 and 12, respectively. The filters 13 and 14 have a large number of filter holes 15 and 16 to prevent dust from entering the float case 80. In the filter 14, filter holes 16 are formed not only on the front surface of the filter 14 but also on the outer peripheral surface. The filter holes 15 and 16 also have the same function as the jets 11 and 12 that regulate the amount of fuel flowing into and out of the float case 80. Therefore, the diameter and number of the jets 11 and 12 and the filter holes 15 and 16 are comprehensively considered. An example of the arrangement of the filter holes 15 and 16 formed in front of the filters 13 and 14 is shown in an enlarged manner in FIG.
[0015]
The upper filter 13 is welded or bonded to a plate 17 on which the jet 11 is formed. The plate 17 is attached to the top of the float case 80 with a set screw 18. On the other hand, the lower filter 14 is attached to the lower side surface of the float case 80 with a set screw 19.
[0016]
The float 10 floats on the fuel liquid level and is accommodated in the float case 80 so that the float 10 can be easily moved up and down in accordance with fluctuations in the fuel liquid level. The position where the float 10 has floated to the top is indicated by reference numeral 10a (FIG. 2). The float 10 is embedded with a permanent magnet 21 for detecting the remaining amount of fuel in the fuel tank 1 in combination with the magnetic sensor 20 of the sensor unit 9.
[0017]
The sensor unit 9 includes a housing 22 that houses the sensor 20 and a stay 23 that is attached to the housing 22 from the lower surface and holds the sensor 20. The housing 22 is positioned on the bottom of the float case 80 with pins 24 and fixed with bolts 25.
[0018]
The float 10 will be further described. The float 10 must move up and down freely in the float case 80 according to the change in the fuel level. If the gap between the side surface of the float 10 and the inner surface of the float case 80 is small, the float 10 is difficult to move in the float case 80, and if the gap is large, the float 10 tilts. In this case, the detection error increases. The movement also gets worse. Therefore, a large number of protrusions are provided on the outer periphery of the float 10 to improve the movement of the float 10. FIG. 7 is a perspective view of the float 10. As shown in this figure, the protrusion 26 is formed on the outer periphery of the float 10 so that the top of the protrusion 26 contacts the inner surface of the float case 80 to guide the float 10. In this way, the contact area between the float 10 and the inner surface of the float case 80 is reduced so that the float 10 can move up and down smoothly even with a small gap. The shape of the protrusion 26 is not limited to the partial sphere as shown in the figure, and may be a bowl-shaped unevenness or a large number of dimples. In short, the contact area between the float 10 and the inner surface of the float case 10 is large. It is only necessary that the gap between the float 10 and the float case 80 be substantially increased.
[0019]
The operation of the fuel remaining amount detection device will be described. FIG. 8 is a diagram illustrating a positional relationship between the permanent magnet 21 and the sensor 20, and FIG. 9 is a circuit diagram illustrating an example of a detection circuit. In FIG. 8, the sensor 20 has two saturable coils LA and LB. The saturable coil LA is for detection, and the saturable coil LB is for external magnetic cancellation, and they are arranged in a direction perpendicular to the extension line of the permanent magnet 21 in the vertical movement direction. The sensor 20 is not on the extension line of the permanent magnet 21 in the vertical movement direction, and is arranged with a deviation D with respect to the permanent magnet 21. The stroke ST of the permanent magnet 21 and the distance d in the height direction between the permanent magnet 21 and the coils LA and LB at the lowest point are determined in consideration of the characteristics described later.
[0020]
In FIG. 9, the saturable coils LA and LB form a bridge circuit together with the resistors R and R. When the magnetic fluxes linked to the coils LA and LB are equal, the resistors R and LB are set so that the sensor output V becomes zero. R is set. A logarithmic amplifier Amp is connected to convert the sensor output V into a linear value. In this differential connection, when magnetic fluxes in the same direction act on each other, the sensor outputs V cancel each other, and when magnetic fluxes in opposite directions act on each other, an output V corresponding to the difference between the magnetic fluxes is obtained. By using the differential connection, the sensor output V is canceled for a large parallel magnetic field such as geomagnetism. Furthermore, it is possible to eliminate the influence of temperature drift that acts on the coils LA and LB in the same manner. Further, since the distance from the sensor 20 is far from the leakage magnetism of other components, the magnetic flux of the leakage flux is linked to the coils LA and LB in the same way. It is.
[0021]
In this way, the sensor output V cancels out an external magnetic field, that is, a magnetic field other than the permanent magnet 21, and depends on a difference in distance between the permanent magnet 21 and the coils LA and LB with respect to the magnetic field of the permanent magnet 21. Value.
[0022]
If the distance between the float 10 and the sensor 20 is long, the magnetic force acting on the sensor 20 is weakened, and the difference in distance between the coils LA and LB and the permanent magnet 21 is small, so the sensor output V is small. On the contrary, if the distance between the float 10 and the sensor 20 is too short, the magnetic force becomes strong and the change in output also becomes large. Accordingly, such magnetic characteristics and output characteristics are taken into account in determining the distance d, the deviation D, and the effective stroke between the coils LA and LB and the permanent magnet 21.
[0023]
Further, if the distance between each coil LA, LB and the permanent magnet 21 is too short, the direction in which the magnetic flux of the permanent magnet 21 links the coils LA, LB is reversed, and the coil LA, LB and the permanent magnet 21 are Despite the approaching distance, the output V decreases. Therefore, in this way, the lowermost point of the permanent magnet 21 must be positioned more than the position where the direction of the magnetic flux interlinking the coils LA and LB is reversed.
[0024]
For example, when the vertical motion stroke ST of the permanent magnet 21 is 40 mm and the deviation D is 13 mm, the saturable coil LA. The height difference d from LB is 10 mm.
[0025]
In the above configuration, when the permanent magnet 21 moves up and down together with the float 10, the magnetic flux exerted on the sensor 20 by the permanent magnet 21 changes, and the sensor 20 generates a sensor output V corresponding to the change in the magnetic flux. The sensor output is converted to a linear output V ′ by a logarithmic amplifier Amp.
[0026]
In the above embodiment, the sensor unit 9 is protruded from the bottom of the fuel tank 1 to the outside. Therefore, in consideration of the magnetic characteristics and output characteristics described above, the height of the permanent magnet 21 and the coils LA and LB when the float 10 is positioned on the bottom surface of the fuel tank 1 is set to substantially zero. Until this time, the remaining amount of fuel can be obtained as a linear output V.
[0027]
Note that due to the difference in the shape of the fuel tank 1, even with the same sensor output V ′, the actual remaining fuel amount differs for each fuel tank. This difference is particularly significant when the remaining amount is extremely small. However, according to the present embodiment, since the logarithmic output V ′ changes linearly in a measurement region where the remaining amount is extremely small, this difference can be easily corrected by an external circuit that processes the sensor output. That is, the operation of adjusting the attachment position of the fuel remaining amount detection device 3 in the fuel tank 1 for each individual fuel tank is unnecessary.
[0028]
【The invention's effect】
According to the first to fifth aspects of the present invention, it is possible to accurately detect the amount of fuel that has accumulated at the bottom of the fuel tank to a very small area. Further, a detection output that is not affected by the shape of the fuel tank can be obtained. In particular, according to the third aspect of the present invention, the inflow and outflow amounts of fuel are limited so that a rapid change in the fuel level in the float chamber does not occur. Therefore, the remaining amount of fuel can be accurately detected when used in a vehicle such as a motorcycle.
[0029]
According to the fourth aspect of the invention, the differential output can eliminate the influence of geomagnetism, leakage magnetism of external equipment, and the like, and a linear output can be obtained. According to the invention of claim 5, since the float can be smoothly moved up and down without being locked in the float chamber, an accurate detection output can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fuel tank including a fuel remaining amount detection device according to an embodiment of the present invention.
FIG. 2 is a front sectional view of a fuel remaining amount detection device.
FIG. 3 is a side view of the remaining fuel amount detection device.
FIG. 4 is a plan view of the remaining fuel amount detection device.
FIG. 5 is a cross-sectional view of a main part of a float case of the fuel remaining amount detection device.
FIG. 6 is a plan view showing an arrangement example of filter holes.
FIG. 7 is a perspective view of a float.
FIG. 8 is a diagram showing a positional relationship between a permanent magnet and a sensor.
FIG. 9 is a circuit diagram illustrating an example of a detection circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Bottom plate, 3 ... Fuel remaining amount detection apparatus, 5 ... Frame, 8 ... Float part, 9 ... Sensor part, 10 ... Float, 11, 12 jet (spout hole), 13, 14 ... Filter 15, 16 ... Filter hole, 20 ... Magnetic sensor, 21 ... Magnet, 26 ... Projection, 80 ... Float chamber (float case)

Claims (3)

In a fuel remaining amount detecting device having a float with a magnet provided in a float chamber so as to be movable up and down, and a magnetic sensor for detecting the remaining amount of fuel in the fuel tank based on the height of the float,
The magnetic sensor comprises a bridge circuit including a pair of saturable coils for obtaining a differential output, and a logarithmic amplifier connected to the output side of the bridge circuit,
The two saturable coils are arranged side by side in a direction perpendicular to the extension line in the vertical movement direction of the magnet, and are arranged to be shifted in the horizontal direction with respect to the extension line.
While providing the float chamber inside the fuel tank to allow the fuel in the fuel tank to flow in and out,
A fuel remaining amount detecting device, wherein the magnetic sensor is disposed below the bottom of the fuel tank.   2. The fuel remaining amount detecting device according to claim 1, wherein the float chamber has an ejection hole for inflow and outflow of fuel and a filter disposed adjacent to the ejection hole.   The fuel remaining amount detecting device according to claim 1, wherein unevenness is formed on a surface of the float.

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