JPH067064B2 - Thermal type fuel level detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive fuel remaining amount detector for detecting a fuel remaining amount in a fuel tank of an automobile or the like.

Conventional technology Conventionally, most of the fuel level measuring methods of this type are contact slide type potentiometers attached to the end of the liquid level float, but in the conventional configuration using such a potentiometer, the contact points are Since it is exposed to liquid or steam, sulfides and other additives contained in the fuel cause contact failure and it is difficult to maintain a correct sliding resistance value for a long time.

Further, there is a problem that it is difficult to obtain a resistor shape proportional to the fuel tank shape, and the error is large.

Various methods have been devised to solve these problems, but none of them has been put to practical use in terms of cost and performance. For example, as disclosed in JP-A-59-148826, in a liquid level sensor in which a thermistor layer is continuously formed on a rod-shaped or long plate-shaped insulator,
Under a constant temperature condition, the liquid level can be grasped relatively accurately, but since the thermistor lacks the linearity of the change in resistance value with respect to temperature change, even if a temperature compensation sensor is introduced, the liquid and ambient temperature changes In that case, it was very difficult to accurately detect continuous liquid level fluctuation. The thermistor is gasoline containing sulfide,
In particular, it has a problem that it is extremely unreliable with respect to light oil and the like, and thus it was impossible to use it as a fuel remaining amount detector for automobiles and the like.

In addition, Nippon Denso Public Technical Report (issued on July 15, 1986,
In reference number 48-101), as shown in FIG. 9, one of the metal wires made of the same material and having the same temperature coefficient of resistance is a heat-sensitive resistance wire 40 for self-heating and the other is a temperature-compensating resistance wire 41.
As a self-heating thermosensitive resistance wire 40 is partially immersed in the fuel liquid, a potential difference between connection points 44 and 45 is amplified by a differential amplifier 46 by a bridge circuit configured with external resistors 42 and 43 having the same resistance value. The level of the liquid is detected by detecting the self-heating temperature difference of the resistance wire as a potential difference, but this method also has two major drawbacks. First, since the temperature compensating resistance wire 41 is installed in a portion of the fuel tank that is not soaked in the fuel liquid, it is possible to correct the fluctuation of the ambient temperature, but it is possible to correct the fluctuation of the temperature of the fuel liquid. Can not. Secondly, since the metal wire is used, the resistance value per unit length of the metal wire becomes extremely low even if the wire diameter is made the thinnest within the range in which the material strength of the metal wire can be secured. When a battery power source for automobiles is used, the current consumption becomes too large, which is not practical.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention is intended to solve such problems, and eliminates the contact failure, which is a defect in the float potentiometer, and accurately maintains the remaining fuel amount regardless of the ambient temperature and the fuel liquid temperature. In addition, the present invention aims to solve the drawbacks of the thermistor and the metal wire system by detecting with high reliability and low current consumption.

Means for Solving the Problem In order to solve this problem, the present invention forms a temperature-sensitive resistor for self-heating having a large temperature coefficient of resistance on an insulating substrate, and heat-sensitive resistor by vaporizing heat cooling of a fuel immersion portion. The value change is detected as a differential output voltage. Further, in order to prevent an error in the differential output voltage due to the correction of the ambient temperature in the fuel tank, the temperature correction temperature sensitive resistor is provided on the insulating substrate.

In the present invention, the self-heating temperature-sensitive resistor that self-heats when energized and the temperature-compensating temperature-sensitive resistor are formed to have substantially the same length, and the two temperature-sensitive resistors are compared to the thermistor. Since the linearity of the resistance change with respect to the ambient temperature change is very excellent, it is a film resistor made of platinum, gold, silver, palladium, ruthenium oxide, copper, nickel, iron or an alloy composition containing them as the main component. The remaining fuel amount can be accurately detected even with respect to the ambient temperature in the fuel tank and the temperature variation of the fuel liquid.

Moreover, since the self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor are film resistors, the resistance value per unit length can be made larger than that of a metal wire, so that the current consumption is reduced. It becomes a practical heat-sensitive fuel remaining amount detector with a small size.

Further, when the temperature sensitive resistor film is formed by applying or printing a plating method or a metal organic material, and baking it,
Alternatively, the temperature-sensitive resistor is formed in a chip shape, and glass epoxy, polyethylene terephthalate (PET), polyester, polyimide and its modified products, polyparabanic acid resin, aramid film, bismaleimide triazine resin (manufactured by Mitsubishi Gas Chemical Co., Inc.), When a chip-shaped temperature sensitive resistor is mounted on a supporting substrate made of Vectra (manufactured by Polyplastics Co., Ltd.), polyacetal, glass, etc., it is a low-cost, high-precision, high-sensitivity thermal-type fuel level detector.

Examples Examples of the present invention will be shown below.

(Embodiment 1) FIGS. 1A and 1B are diagrams showing a pattern configuration of a temperature sensitive resistor in a detection portion of a fuel quantity detector according to an embodiment of the present invention. In FIG. 1, 1 is a support substrate. Is an insulating ceramic substrate. 2 is SiO ₂ —Al ₂ O ₃ —B ₂ O having a softening point of 920 ° C. coated on the ceramic substrate 1.
_{It is a 3} series underglaze glass. 3 is a self-heating temperature-sensitive resistor having a large temperature coefficient of resistance formed on the underglaze glass 2 by printing and firing, and 4 is the same material as the self-heating temperature-sensitive resistor 3 and has substantially the same length. Is a temperature-sensitive resistor for temperature compensation. In this example, a pattern was printed using a platinum metal organic paste in which a resin acid or a modified product thereof was added as a binder to platinum salts of sulfides of terpenes of 4,5 or mercaptide, and baked at 900 ° C., This is a platinum thin film temperature-sensitive resistor with a thickness of about 4000Å. The resistance value at 0 ° C is 20Ω for the self-heating temperature-sensitive resistor and 5K for the temperature compensating resistor.
In Ω, the temperature coefficient of resistance is about 3700 ppm / ° C. 5 is a take-out electrode having a low conductor resistance,
In this embodiment, silver palladium (thickness: about 15 μm) is used.

Further, a lead borosilicate-based overcoat glass film 6 is formed on the temperature-sensitive resistors 3 and 4 and the electrode 5 in order to secure oil resistance, chemical resistance, and insulation, and a protective coating is applied. There is.

FIG. 2 shows that the first temperature sensing element 7 including the temperature sensing resistor for self-heating and the second temperature sensing element 8 including the temperature sensing resistor for temperature compensation are provided in a pair in the fuel tank. It is a diagram showing a state in which it is installed in the fuel pump unit 9, and these elements are electrically connected by the circuit shown in FIG. In the figure, reference numeral 11 denotes the detection unit shown in FIG. 2, which includes the temperature sensing resistor 12 for self-heating and the temperature sensing resistor 13 for temperature compensation shown in FIG.
And these temperature-sensitive resistors 12, 13
Are connected to resistors 14 and 15, respectively, thereby forming a resistor bridge circuit.

The output terminal of the bridge circuit is connected to the inverting input terminal and the non-inverting input terminal of the operational amplifier 16 that constitutes the differential amplifier circuit via resistors 17 and 18, respectively.
19 is a resistance.

That is, in this circuit, the resistance value of the temperature-sensitive resistor 12 that is self-heating due to the supply of a constant voltage or a constant current changes depending on the liquid level of the fuel, and this change is differential as a change in the potential at the output end of the bridge circuit. Input to the amplifier circuit,
The difference voltage is output from the output end of the differential amplifier circuit, and the change in the fuel liquid level can be extracted by changing the voltage.

Further, since the temperature-compensating temperature-sensitive resistor 13 is thermally separated from the self-heating temperature-sensitive resistor 12, the heat generated by the self-heating temperature-sensitive resistor 12 is transferred to the temperature-compensating temperature-sensitive resistor 13. Not transmitted.

Therefore, the temperature compensating function of the temperature compensating temperature-sensitive resistor 13 with respect to the atmospheric temperature in the gasoline tank is sufficiently exerted, so that the fuel level can be detected with high accuracy.

Further, similarly to the present embodiment, a metal or metal oxide thin film may be formed using a metal organic material of gold, silver, ruthenium, or palladium, and this may be used as a temperature sensitive resistor. In this embodiment, the self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor are formed on different substrates, but if necessary, they may be formed on the same substrate as shown in FIG. I don't care.

(Embodiment 2) As shown in FIG. 1, a self-heating temperature-sensitive resistor and a temperature-compensating temperature-sensitive resistor were made of a nickel metal organic substance such as nickel octylate and an iron metal organic substance such as iron octylate. Screen-print the paste mixed with modified rosin etc. as a binder and mixed in the ratio of 1: 1 at 620 ° C in air.
After using the nickel-iron thin film having a thickness of about 2000Å and a temperature coefficient of resistance of about 4500 ppm / ° C, which is obtained by firing and reducing in a reducing atmosphere at 550 ° C, the borosilicate-based overglass at 600 ° C in a nitrogen atmosphere. Example 1 A temperature-sensitive element formed by applying a coat
Used in the same manner as.

Further, in the same manner as in this example, using a copper metal organic matter,
It is also possible to form a copper thin film and use it as a temperature sensitive resistor.

(Example 3) The temperature sensing resistor for self-heating and the temperature sensing resistor for temperature compensation in FIG. 1 are nickel boron thin films obtained by electroless nickel boron plating, and the temperature is 600 in a nitrogen atmosphere.
By forming the borosilicate-based overcoat glass at ℃, the film of nickel boron thin film is heat-aged, and the sintered compactness of the film is improved.
Å, Nickel boron thin film with temperature coefficient of resistance of about 4200ppm / ℃.

If necessary, electroplating can be performed.

The temperature sensitive element thus formed can be used as in the first embodiment.

Further, in the same manner as in this embodiment, a resistor thin film is formed by platinum, gold, silver, palladium, copper, chromium, cobalt, iron or an alloy plating film containing them as a main component, and this is formed into a temperature sensitive resistor. Can also be

By the way, if the temperature coefficient of resistance of the self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor are the same, ideal fuel level measurement can be performed, but it is difficult to actually make them both the same. Therefore, practically, if the difference between the two is within 500 ppm / ° C., there is no problem. Therefore, if the difference in the temperature coefficient of resistance is within 500 ppm / ° C,
The materials of the temperature compensating temperature sensitive resistors do not necessarily have to be the same. Further, in order to make the temperature compensating function act on all the fuel liquid levels, it is desirable that the temperature compensating temperature sensing resistor has the same length as the self-heating temperature sensing resistor. However, this does not apply if the pattern design of the temperature sensitive resistor is unavoidable.

(Embodiment 4) FIGS. 5A and 5B are views showing a detecting portion of a fuel remaining amount detector according to another embodiment of the present invention.

In FIG. 5, reference numeral 20 is a supporting substrate made of a polyimide film having a thickness of 50 μm, and a conductor 21 having a predetermined wiring pattern is formed on the supporting substrate 20. Reference numeral 22 is a platinum thermosensitive resistor chip for self-heating, which is formed by printing a platinum metal organic paste on an underglaze-treated forsterite substrate, firing it at 900 ° C., and then applying an electrode paste containing silver as a primary component. Printed as electrodes, 600 ℃
After being baked in, a lead borosilicate-based overcoat glass was applied, and the resistance temperature coefficient was 3700 ppm / ° C. and the resistance value at 0 ° C. was 1.0 Ω. Reference numeral 23 is a temperature-compensating platinum temperature-sensitive resistor chip manufactured in the same manner as the self-heating temperature-sensitive resistor chip, and has a resistance temperature coefficient of 3700 ppm / ° C.
The resistance value at 0 ° C. was 50Ω. The self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor thus formed are connected to the circuit shown in FIG. Excellent and accurate fuel level detection.

In this embodiment, the self-heating temperature-sensitive resistor chip and the temperature-compensating temperature-sensitive resistor chip are mounted on separate support substrates.
They may be mounted on the same support substrate. Further, the temperature compensating temperature sensitive resistor also uses a chip-shaped resistor group, but as shown in FIG. 1b, a temperature compensating temperature sensitive resistor formed on a ceramic substrate may be used. good.

(Embodiment 5) FIG. 6 is a diagram showing a pattern configuration of a temperature sensitive resistor in a detecting portion of a fuel quantity detector according to another embodiment of the present invention. In FIG. 6, 24 is a ceramic as a supporting substrate. The substrate. Reference numeral 25 is a thin-film, ultrafine wire-shaped temperature-sensitive resistor for self-heating, which has a large temperature coefficient of resistance and is formed on the ceramic substrate 24 by printing and firing. A platinum metal organic paste is sintered in air at 900 ° C. And thickness 400
It is a thin film platinum resistor with 0Å and has a temperature coefficient of 3
It is 700 ppm / ° C. This ultra-fine linear temperature-sensitive resistor 25
Are formed so as to be arranged in a plurality of stages in parallel with the liquid surface of the fuel. In this embodiment, a total of 13 temperature-sensitive resistors 25 are formed at positions where the remaining fuel amount is divided into 12. Further, in the present embodiment, the temperature sensitive resistor is arranged so as to be parallel to the liquid surface, but it may be arranged so as to have a constant angle with the liquid surface if necessary. Then, they are connected by an electrode (thickness: about 15 μ) 26 made of silver palladium or the like having a low conductor resistance to form a parallel resistance circuit. Reference numeral 27 is an extraction electrode provided at the end of each temperature-sensitive resistor 25.
A chip resistor 29 having a small temperature coefficient, which is connected in series with the temperature sensitive resistor 25, is mounted, and a signal line 30 is formed on the back surface through a through hole 32 to detect a variation in the differential output voltage. The board 31 is soldered. Further, a lead borosilicate-based overcoat glass film 28 is formed and protectively coated on the temperature-sensitive resistors 25 and the electrodes 26 in order to secure oil resistance and chemical resistance.

FIG. 7 shows a circuit diagram of a fuel liquid level detection device using the detection unit shown in FIG. 6, in which 33 is a detection unit, and twelve self-heating temperature-sensitive resistors connected in parallel. Three
4 and a resistor 36 having a small temperature coefficient of resistance connected in series with the temperature-sensitive resistor 34 are a temperature-sensitive resistor 35 formed at the lowest point of the detection unit and a resistance temperature connected in series with the temperature-sensitive resistor 35, respectively. A resistor 37 having a small coefficient and a resistor bridge circuit are configured.

The temperature sensitive resistors 34 and 35 have substantially the same temperature coefficient of resistance, and ideally, it is preferable that they have substantially the same resistance value.

The output ends of these bridge circuits are respectively connected to the inverting input terminal and the non-inverting input terminal of the operational amplifier 38 forming the differential amplifier circuit.

That is, in this circuit, it is always immersed in fuel,
Of the temperature-sensitive resistors 35 whose resistance value does not fluctuate due to self-heating and the temperature-sensitive resistors 34 depending on the liquid level of the fuel, the bridge circuit composed of the temperature-sensitive resistors immersed in the fuel is
As shown in Figure a, there is almost no differential output voltage,
A differential output voltage instantly appears from the bridge circuit composed of the temperature sensitive resistor 35 and the temperature sensitive resistor exposed in the air as shown in FIG. 8B. After the differential output voltage is amplified by the operational amplifier 38, the calculation unit 39 counts the number X of the temperature sensitive resistors in which the differential output voltage is not generated.

For example, if X is 5, the remaining fuel amount is 5/12 of the total.
It shows that it remains.

Although the remaining fuel amount is detected in this way, the thermal fuel remaining amount detector according to the present invention only detects whether or not the differential output voltage is generated, and It does not detect the absolute value itself. Therefore,
It is possible to accurately grasp the remaining fuel amount instantaneously without waiting until the value of the differential output voltage becomes a constant value. Further, due to such excellent responsiveness, it is possible to detect the remaining fuel amount without energizing constantly, for example, by energizing the operating voltage Vcc or the constant current I every two minutes in a pulsed manner. As a result, the power consumption of the present heat-sensitive fuel remaining amount detector can be greatly reduced, and the reliability of the detection element can be improved.

Further, in the present embodiment, the remaining fuel amount was detected by comparing the thermosensitive resistor immersed in the fuel with the rest of the thermosensitive resistor at all times. , It may be compared with the rest of the thermal resistor.

Further, in this embodiment, the chip resistor is used as the resistor having a small temperature coefficient of resistance, but a glaze resistor such as ruthenium oxide may be formed on the ceramic substrate by printing and firing.

As described above in the present embodiment, by arranging the temperature-sensitive resistors that indicate the remaining liquid level according to the shape of the fuel tank in a pattern, the accurate remaining amount corresponding to the temperature-sensitive resistor part is detected. can do. It is also easy to detect the remaining liquid level according to the odd-shaped fuel tank. Further, when the self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor are disposed separately from each other, the heat-sensitive responsiveness on each combustion surface of the fuel is excellent. Further, it is possible to automatically correct a change in the ambient temperature in the fuel tank, and since it is a heat-sensitive type, it is possible to detect various gasoline fuels without causing a significant difference. Furthermore, since the temperature-sensitive resistor is coated with overcoat glass, which has excellent compactness and stability, it can maintain its reliability and quality for a long time even when immersed in various fuels containing additives such as alcohols and sulfides. It is a thing.
When a plating method or a metal organic paste is used, a desired thin film pattern of the temperature sensitive resistor can be easily obtained by printing and sintering, which does not require a material loss or an etching step such as a sputtering method, and improves productivity. It can be manufactured at low cost.

Further, in a thermal type fuel remaining amount detector formed by mounting a chip-shaped temperature sensitive element on a supporting substrate such as a glass epoxy substrate, even in a large fuel tank whose substrate length is, for example, 50 cm, This is very useful industrially because it can be easily dealt with, the substrate cost is lower than that of the ceramic substrate, and the heat capacity is small, so that the detection speed is further increased.

EFFECTS OF THE INVENTION As described above, according to the present invention, by arranging the temperature-sensitive resistors that indicate the remaining liquid surface according to the shape of the fuel tank in a pattern, it is possible to accurately measure the temperature of the temperature-sensitive resistors. The remaining amount can be detected. Further, the remaining liquid level corresponding to the odd-shaped fuel tank can be easily detected, which is extremely useful in industry.

[Brief description of drawings]

1A and 1B are plan views showing a detection unit used in a fuel liquid level detection device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the detection unit arranged in a fuel tank, and FIG. FIG. 4 is a circuit diagram of the same device, and FIG. 4 is a plan view showing a detecting portion of a thermal type fuel remaining amount detector in which a self-heating temperature sensitive resistor 3 and a temperature compensating resistor are formed on one insulating substrate. 5a and 5b are plan views showing a detection part of a thermosensitive fuel level detector formed by mounting a thermosensitive resistor chip on a support substrate, and FIG. 6 shows a thermosensitive resistor for self-heating. FIG. 8 is a plan view showing a detecting portion of a thermal type fuel residual amount detector of a type in which the liquid level is digitally detected by being connected in parallel, FIG. 7 is a circuit diagram of the detector shown in FIG. 6, and FIG. a is a characteristic diagram showing a differential output voltage generated from a bridge circuit in which both heat-sensitive systems are in fuel, and FIG. Characteristic diagram showing the differential output voltage one of the antibodies is produced from the bridge circuit which is exposed in the air,
FIG. 9 is a circuit diagram of a conventional example in which a metal wire is used as a fuel remaining amount detector. 1, 24 ... Ceramic substrate, 2 ... Underglaze glass, 3, 25 ... Self-heating temperature-sensitive resistor, 4 ... Temperature-compensating temperature-sensitive resistor, 5, 26, 27 ... Electrode, 6, Two
8 ... overcoat glass film, 7 ... first temperature sensitive element, 8 ... second temperature sensitive element, 9 ... fuel pump unit, 11,33 ... detector, 12,34 ... self-heating Temperature sensitive resistor, 13 ... Temperature sensitive resistor for temperature compensation, 14, 15,
17, 18, 19, 36, 37 ... Resistance, 16, 38 ...
... operational amplifier, 20 ... support substrate, 21 ... conductor, 22
...... Self-heating platinum temperature sensitive resistor chip, 23 ...... Temperature compensation platinum temperature sensitive resistor chip, 29 ...... Chip resistor, 3
0 ... Signal line, 31 ... Flexible board, 32 ...
… Through hole, 35 …… Temperature-sensitive resistor, 39 …… Calculator.

Claims (11)

[Claims] 1. A self-heating temperature-sensitive resistor having a large resistance temperature coefficient and a relatively small resistance value, and a resistance temperature coefficient substantially the same as the self-heating temperature-sensitive resistor and a relatively resistance. A temperature compensating temperature sensitive resistor with a large value is formed on a support substrate, and the change in the resistance value of the temperature sensitive resistor due to evaporative heat cooling of the fuel immersion portion is detected as a differential output voltage to determine the liquid level. A heat-sensitive fuel remaining amount detector characterized by detecting. 2. A first sensor for detecting a change in temperature-sensitive resistance value due to evaporative heat cooling of a fuel immersion portion as a differential output voltage by forming a temperature-sensitive resistor for self-heating having a large resistance temperature coefficient on a supporting substrate. Thermosensitive residual fuel amount detection comprising a temperature element and a second temperature element having a temperature compensating temperature resistor having resistance temperature characteristics similar to those of the self-heating temperature sensitive resistor formed on a supporting substrate. vessel. 3. The first temperature-sensitive element is constituted by mounting one or a plurality of self-heating temperature-sensitive resistors having a large temperature coefficient of resistance formed on a chip-shaped insulating substrate on a supporting substrate. The heat-sensitive fuel remaining amount detector according to claim 2, wherein 4. A vaporization heat of a fuel-immersed portion, which is formed by mounting one or a plurality of self-heating temperature-sensitive resistors having a large temperature coefficient of resistance formed on a chip-shaped insulating substrate on a supporting substrate. A first temperature-sensitive element that detects a resistance value change of the temperature-sensitive resistor due to cooling as a differential output voltage, and a chip-shaped insulating substrate that has resistance temperature characteristics similar to those of the self-heating temperature-sensitive resistor. A thermosensitive fuel residual amount detector configured with a second temperature sensing element configured by mounting the formed temperature sensing temperature sensing resistor on a support substrate. 5. The thermal type fuel level detector according to claim 4, wherein the first temperature sensitive element and the second temperature sensitive element are mounted on the same supporting substrate. 6. A plurality of temperature-sensitive resistors for self-heating having a large resistance temperature coefficient, which generate heat when energized, are arranged in multiple stages on a supporting substrate, and the resistors having a small temperature coefficient of resistance are arranged for each temperature. By connecting in series to the resistor, the resistor group connected in series is connected in parallel, by detecting the temperature-sensitive resistance change due to evaporative cooling of the fuel immersion site as a variation of the differential output voltage, A heat-sensitive fuel residual amount detector characterized by detecting a fuel liquid level. 7. A self-heating temperature-sensitive resistor having a large temperature coefficient of resistance is a temperature-sensitive resistor formed in advance on a chip-shaped insulating substrate, and the temperature-sensitive resistor is mounted on a supporting substrate. The heat-sensitive fuel residual amount detector according to claim 6, which is a battery. 8. The thermosensitive fuel residual amount detector according to claim 1, wherein the temperature sensing resistor for self-heating and the temperature sensing resistor for temperature compensation have substantially the same length. 9. The self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor are platinum, gold, silver, palladium, ruthenium oxide, copper, nickel, iron, chromium, cobalt or an alloy containing them as a main component. 7. The heat-sensitive fuel residual quantity detector according to claim 1, which is a membrane resistor made of a composition. 10. A self-heating temperature-sensitive resistor and a temperature-compensated temperature-sensitive resistor comprising platinum, gold, silver, palladium, ruthenium oxide, copper, nickel, iron, chromium, cobalt, or an alloy composition containing them as a main component. 10. The heat-sensitive fuel residual amount detector according to claim 9, which is formed by applying or printing a metal-organic substance of the product and then firing it. 11. The heat-sensitive type according to claim 1, 2, 4 or 6, wherein the surfaces of the resistor films of the self-heating temperature-sensitive resistor and the temperature-compensating temperature-sensitive resistor are protected by an insulator such as glass or resin. Fuel level detector.