JPS5896154A - Detection of mixed-ratio of fuel and apparatus thereof - Google Patents

Abstract

PURPOSE:To correctly measure the mixed-ratio of gasoline and alcohol by feeding a resonance frequency signal to the fuel whose mixed-ratio is to be detected and detecting the variation of the resonance frequency due to the variation of said fuel. CONSTITUTION:An input connection loop 3 for matching with an input coaxial circuit 2 is installed on the top edge of a cylindrical cavity resonator 4, and a high frequency signal is supplied from a ultra-high frequency oscillator 1 through said input coaxial circuit 2. An output connection loop 7 is installed on the lower edge of the cavity resonator 4, and mixed fuel 6 passes through a dielectric pipe 5. The mixed ratio of alcohol is detected by measuring the resonance frequency of the cavity resonator 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting a mixture ratio of mixed fuel, and more particularly to a fuel mixture ratio detection method and device for detecting the alcohol content concentration in a mixed fuel of gasoline and alcohol.

Traditionally, gasoline has been the main fuel for engines such as automobiles, but alcohol fuels such as methanol have been attracting attention due to the recent rise in crude oil prices and resource shortages.

This alcohol fuel does not depend on petroleum and does not generate sulfur dioxide gas compared to petroleum, so it is less polluting and can be used in current automobile engines without major modifications.

For this reason, countries such as the United States, West Germany, and Brazil convert their own resources into alcohol and mix it into gasoline for use as automobile fuel.

When mixing alcohol with gasoline, the ignition point of gasoline and the ignition point of methanol are different, so it is important to know the mixing ratio accurately and control the engine to optimal combustion conditions. That is, the difference in the mixing ratio of gasoline and methanol directly manifests itself as a difference in ignition temperature and output, and directly affects the ignition timing.

Therefore, the mixing ratio of gasoline and methanol (alcohol) is basic information for optimally controlling the engine, and it is necessary to easily and accurately know this mixing ratio.

There are many methods for measuring the mixing ratio of gasoline and methanol (alcohol), including an infrared absorption method, a heat of vaporization method, a modified heat conduction method, an electrical conductivity method, and a capacitance method. When these various methods are actually put into practical use in automobiles, there are various constraints such as temperature changes, power supplies, and installation space, and it is currently considered that the capacitance method is the most appropriate.

An object of the present invention is to provide a fuel mixture ratio detection method and apparatus that can accurately measure the mixture ratio of gasoline and alcohol.

In the present invention, two oscillators that oscillate at a resonance frequency specific to the cavity resonator are provided, and one cavity resonator has a

Mixed fuel is flowed through a pipe made of dielectric material, and an oscillation frequency signal that changes according to the fuel mixture ratio is obtained.
This oscillation frequency signal and the oscillation frequency signal obtained from the other oscillator are input to a mixer circuit, and the mixing ratio of gasoline and alcohol is detected by detecting the frequency difference between the two.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic diagram for explaining the present invention in detail.

In the figure, an input coupling loop 3 for matching with an input coaxial circuit 2 is provided at the upper end of a single cylindrical cavity resonator 4, and a high frequency signal is transmitted from an ultra high frequency oscillator 1 through this input coaxial circuit 2. Supplied. Further, an output coupling loop 7 is provided at the lower end of the cavity resonator 4, and an output coaxial circuit 8 is connected thereto. A frequency meter is connected via this output coaxial circuit 8. In addition, the cavity resonator 4
A dielectric pipe 5 is provided therethrough.

The mixed fuel 6 is configured to pass through the dielectric pipe 5.

Therefore, the output of the super high frequency oscillator 1 is the input coaxial circuit 2
The signal is input to the cavity resonator 4 through the input coupling loop 3.

At this time, the oscillation frequency of the super high frequency oscillator 1 is the same as that of the cavity resonator 4.
are pulled into the resonant frequency f'o, and become the same frequency.

Now, when the mixed fuel 6 is flowed through the dielectric pipe 5, the resonance frequency of the cavity resonator 4 becomes the resonance frequency characteristic A shown in FIG.
As shown in the figure, the resonance frequency exhibits a characteristic that as the alcohol mixing ratio increases, the resonance frequency decreases, and as the gasoline mixing ratio increases, the resonance frequency increases. Therefore, the alcohol mixing ratio can be determined by measuring the resonance frequency of the cavity resonator.

This principle is based on the fact that when a dielectric material is inserted into a cavity resonator, the resonant frequency increases depending on the relative permittivity and dielectric loss angle of the material and its volume.

Decrease. Now, Teflon is used as the material for the fuel pipe. As a result, the ratio of the resonance frequency change due to the Teflon pipe to the change when mixed fuel is actually flowing is approximately 5.
However, with the configuration shown in Figure 1, it is affected by the ambient temperature,
As shown in the temperature characteristic B shown in FIG. 3, the resonant frequency of the cavity resonator 4 decreases as the temperature rises. This value corresponds to the coefficient of thermal expansion of the material of the cavity resonator. Therefore, accurate detection cannot be performed unless this change in resonant frequency due to temperature change is compensated for.

To compensate for this temperature characteristic, it is necessary to use a low expansion material such as Invar or Super Invar, or to take measures to compensate for the temperature characteristic, but both methods have the problem of high manufacturing costs, making them impractical. Not suitable for

An embodiment of the present invention in which this temperature compensation is applied is shown in FIG.

In the drawings, parts denoted by the same reference numerals as those in FIG. 1 are the same parts and have the same functions. A cavity resonator 14 having the same resonant frequency is arranged in parallel to this cavity resonator 4. An input coupling loop 13 is provided at the upper end of this cavity resonator 14, and an input coaxial circuit 12 is connected to this input coupling loop 13. The super high frequency oscillator 11 is connected to the input coaxial circuit 12 via this input coaxial circuit 12
High frequency power is supplied from In addition, cavity resonator 1
An output/power coupling loop 17 is provided at the lower end of 4, and an output coaxial circuit 18 is connected to this output coupling loop 17. The output coaxial circuit 18 and the output coaxial circuit 8 are configured to output an output difference frequency in the mixer diode 10. The frequency passed through this mixer diode 10 is input to a counter 15, a difference frequency is measured, and the difference frequency is outputted from an output terminal 16.

Therefore, in this embodiment, two oscillators with cavity resonators are used.
A dielectric pulp 5 is passed through one side of the pipe 5, and a mixed fuel 6 is flowed into the dielectric pipe 5.

With this configuration, before the mixed fuel 6 flows, the resonance frequencies of the two cavity resonators 4 and 14 are adjusted to be almost the same, so the output from the mixer diode 10 is zero. be. If the resonance frequencies of the two cavity resonators 4 and 14 are different from each other, the difference frequency is output.

That is, using the output value of the mixer diode 10 before flowing the mixed fuel 6 into the dielectric pipe 5 as a reference, the frequency of the mixer output when fuel of an appropriate mixing ratio is flowing is counted by the counter 15 and converted into a voltage signal. A voltage corresponding to the mixing ratio is output to the output terminal 14.

When two cavity resonators 4 and 14 are used in this way, changes due to the surrounding environment such as temperature characteristics will change with the same temperature characteristics for both cavities, so the difference in frequency between before and after the change will be due to the difference between the two cavity resonators. 4 and 14 are substantially constant, and only the frequency change caused by the mixed fuel 6 flowing in the dielectric pipe 5 is outputted from the mixer diode 10, so that the temperature of the cavity resonator is sufficiently compensated. Further, although the output voltage level of the mixer diode 10 is affected by temperature, in the detection of four frequencies, it is not affected at all and an output that is extremely stable with respect to temperature can be obtained.

The circuit shown in FIG. 4 can be expressed as an equivalent circuit as shown in FIG.

In the figure, the same reference numerals as those used in FIG. 4 correspond to the circuits shown in FIG. When the cavity resonator 4°14 is expressed as an equivalent circuit, the inductance is 20°25 and the capacitance is 21, 26. Represented by resistance 22.27, dielectric pipe 5 and mixed fuel 6
can be represented by a variable capacitor 23 and a variable resistor 24.

That is, the resonant frequency of the cavity resonators 4 and 14 is determined by the parallel resonance of the inductance 20.25 and the capacitance 21.26, and the variable capacitance 23 of the mixed fuel 6 is added thereto to change the resonant frequency. Since the amount of change changes depending on the position and volume of the dielectric pipe 5 inserted into the cavity resonator, the sensitivity for detecting one frequency can be freely selected.

The calculation formula for the cavity resonators 4 and 14 used in this example is: where the diameter of one cylinder is Dφ and the length 'kL, the resonance frequency is f. C: Speed of light S: Number of waves riding in the L direction Xmn: A constant determined by a Bessel function.

Figure 6 shows a circuit that converts the difference frequency obtained from the mixer diode 10 into an analog output.
0, a counter 31, a timing controller 32, and a D/A converter 33. In this embodiment, the difference frequency is set to about 10 to 200 MH2, and frequency-voltage conversion is performed to obtain an output voltage of 0.5 V to 10 V.

7 and 8 are implementations of the embodiment shown in FIG. 4 of the present invention, with FIG. 7 being a view seen from the oscillator side and FIG.
The figure is a diagram seen from the mixer circuit and frequency-voltage conversion circuit side.

In FIG. 7, the oscillator substrate 51 is a thin plate made of Teflon or ceramic with low high-frequency loss, and has a strip on its surface.
A super high frequency oscillation circuit 52tl is formed in the form of an IJ tube line, and a transistor 53 (for example, a high frequency transistor, FE, T, etc.) is provided at a predetermined position, and a bias voltage terminal 5 is provided.
Approximately 10G when applying a voltage of 5 to 10 to 4 and 55
Oscillation of H2 occurs.

Its output is fed by the input coupling loop 3.13 to the cavity resonators 4, 14, and at the same time the oscillation frequency is pulled into the resonant frequency of the cavities 4, 14. The operations of the two oscillators and cavity resonators 4 and 14 are exactly the same.

In FIG. 8, the output of the cavity resonators 4, 14 is detected by the output coupling loop 7.17 and the mixer circuit board 57.
Mixer diode 10 and pulse shaping circuit 3 configured above
0. The signal is output from the D/A converter 33 via the counter 31 and the like.

Although not shown in FIGS. 7 and 8, the oscillator, mixer circuit, and signal processing circuit are provided with dust-proof and moisture-proof cases.

FIG. 9 shows the output characteristic C corresponding to the mixing ratio obtained in this example. Voltage ratios and voltage levels can be adjusted.

Therefore, according to this embodiment, the cavity resonator does not require any correction of temperature characteristics, so it can be easily manufactured by die-casting aluminum, and the oscillator and mixer circuits can be manufactured using a high-frequency printed circuit board or a ceramic substrate. Since it can be manufactured using thick film printing, it can be produced in large quantities at low cost.

Although a high frequency transistor or FET is used as the oscillation element, a two-terminal element such as a Gunn diode or an invat diode can also be used.

Also, the overall size of the sensor is limited to high frequencies (e.g. 100H).
2 or more), the size can be reduced, but even in the 5 to 10 GH2 band, by selecting a small resonance mode order of the cavity resonator, it is possible to manufacture the size to about 5 crr1 x 5 crn x 7 m or less.

FIG. 10 is a configuration diagram in which the sensor of the present invention is incorporated into a part of an engine control system, in which mixed fuel is sent from a fuel tank 100 to a fuel pump 101, and the mixture ratio is determined by a valve attached to a fuel supply pipe 102. It is measured by the fuel mixture ratio sensor 103 of the invention.

The fuel is then controlled by an injection controller 104 and injected into the combustion chamber from an injector 105.

The injection amount and timing and the ignition timing of the spark plug 107 connected to the igniter 106 are determined by the pressure sensor 1.
08, crank angle sensor 109. Throttle sensor 11
0. Each signal from the air flow sensor 111.0□ sensor 112 is processed by the computer 113 to obtain optimal combustion conditions.

As explained above, according to the present invention, the mixing ratio of gasoline and alcohol can be accurately measured.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a principle characteristic graph, Fig. 3 is a temperature characteristic diagram of a cavity resonator, Fig. 4 is a configuration diagram showing an embodiment of the present invention, Fig. 5 Fig. 4 is an equivalent circuit diagram of the illustrated embodiment, Fig. 6 is a circuit diagram for converting the difference frequency of the mixer diode into voltage, Figs. 7 and 8 are external configuration diagrams of this embodiment, and Fig. 9 is an equivalent circuit diagram of the illustrated embodiment. FIG. 10, which is an output voltage characteristic diagram corresponding to the mixture ratio obtained in the embodiment of the present invention, is a diagram in which the present embodiment is incorporated into an engine control system. 1.11...Ultra high frequency oscillator, 3.13...Input coupling. Loop, 4.14... Cavity resonator, 5... Dielectric pipe, 6... Mixed fuel, 7.17... Output coupling loop. 8.18...Output coaxial circuit, 10...Mixadaio early l Prison alcohol mixing umbrella → Fig. 3

Claims (1)

[Claims] 1. Supplying a resonant frequency signal to the fuel whose mixture ratio is to be detected;
A fuel mixture ratio detection method that detects a fuel mixture ratio by detecting a change in resonance frequency that is changed by the fuel. 2. The same resonance frequency is applied to the first cavity resonator and the second cavity resonator through which the dielectric pipe is penetrated, and to the first cavity resonator and the second cavity resonator. a first means for supplying, a second means for extracting the resonant frequency of the first cavity resonator, a third means for extracting the resonant frequency of the second cavity resonator; 1. A fuel mixture ratio detection device comprising: fourth means for detecting the frequency difference between the output from the second means and the output from the third means.