CN108845002A - A kind of methanol gasoline concentration detection apparatus and method - Google Patents

Abstract

The invention discloses a methanol gasoline concentration detection device and method. The detection device includes a measurement module, a signal processing module and a display module. The measurement module is composed of an arc-shaped capacitive sensor, which is placed in methanol-gasoline mixed fuel; the signal processing module is composed of a capacitor-voltage circuit, a Freescale microcontroller, an RS232 serial port circuit and a CAN bus communication circuit. The signal processing module sends the methanol concentration signal to the display module through the serial port through the conversion of the capacitor-voltage circuit and the processing of the single-chip microcomputer, and communicates with the general control system through the CAN bus communication circuit; the display module dynamically displays the current methanol-gasoline mixed fuel. concentration of methanol. The invention can quickly and accurately measure the methanol concentration in the methanol-gasoline blended fuel, and can display the concentration information in real time.

Description

Methanol gasoline concentration detection device and method

technical field

The invention relates to methanol concentration detection, in particular to a detection device and method for methanol concentration of methanol-gasoline mixed fuel.

Background technique

For new energy vehicles that use methanol-gasoline mixed fuel, methanol-gasoline can be used, or pure gasoline can be added when refueling. The fuel supply method is more flexible, but it is necessary to dynamically change the engine's fuel density according to the actual concentration of methanol in the mixed fuel in the car. The amount of fuel injected to ensure the power of the car. The real-time and accurate detection of the concentration of methanol in the mixed fuel provides a reference for the automobile ECU to dynamically change the fuel injection quantity of the engine.

In existing new energy vehicles filled with methanol-gasoline mixed fuel, the driver usually perceives the current vehicle power status and manually adjusts the fuel injection amount of the engine, which can easily lead to waste of fuel and damage to the engine.

The methanol concentration detection device utilizes the property that there is a certain difference in the dielectric constant of the mixed fuel with different methanol concentrations, and detects the methanol concentration in the mixed fuel through a capacitive sensor composed of a pair of flat plates (plates). Although it can provide a reference basis for the adjustment of the fuel injection quantity, due to the poor accuracy of the detection results, it cannot effectively reduce unnecessary fuel consumption while ensuring vehicle power.

Contents of the invention

In order to solve the problem of insufficient measurement accuracy of methanol concentration in methanol-gasoline mixed fuel, the invention provides a methanol-gasoline concentration detection device and method.

To achieve the above object, the present invention adopts the following technical solutions:

A methanol concentration detection device, the detection device includes a measurement module, the measurement module includes a capacitive sensor, and the capacitive sensor adopts an arc-shaped polar plate.

Preferably, the arc-shaped pole plate includes a body made of metallic copper and a layer of corrosion-resistant insulating material (such as green oil) uniformly covering the surface of the body, and the thickness of the layer of insulating material is 0.05-0.1 mm.

Preferably, the capacitive sensor includes two opposite arc-shaped pole plates, the shape of the arc-shaped pole plates is an arc surface with a radian of 120°, the inner diameter of the arc surface is 10mm, and the length of the arc-shaped pole plates (ie, the pole plate The distance between two arc-shaped edges) and the thickness are 80mm and 0.5mm respectively, and the maximum distance between two arc-shaped plates is 10mm.

Preferably, the capacitive sensor is arranged in the fuel injection pipe of the mixed-fuel vehicle to be tested, and the fuel injection pipe includes a section for installing an arc-shaped pole plate, the inner diameter of this section is 20mm, and the length is 100mm ( It is longer than the length of the arc plate, which is convenient for substrate installation and improves the detection accuracy).

Preferably, the arc-shaped pole plates are arranged symmetrically along the central axis of the fuel injection pipe, the concave sides of the two arc-shaped pole plates face each other, and the convex side of the arc-shaped pole plates passes through the inner wall of the fuel injection pipe. Nylon mounting brackets secure.

Preferably, the detection device also includes a signal processing module and a display module, the signal processing module includes a capacitance-voltage conversion circuit, a single-chip microcomputer, a display interface circuit and a dual CAN bus communication circuit; the capacitance-voltage conversion circuit includes sequentially connected The oscillator, limiting amplifier and frequency discriminator, the oscillator is connected with the capacitive sensor, the frequency discriminator, the display interface circuit and the dual CAN bus communication circuit are respectively connected with the single chip microcomputer, and the display module includes a touch screen connected with the display interface circuit .

A method for detecting methanol concentration, comprising the following steps:

1) Place the above-mentioned capacitive sensor in the fuel injection pipe of the mixed-fuel vehicle to be tested;

2) using the capacitive sensor to measure the methanol concentration of the mixed fuel in the fuel injection pipe, and converting the measurement result of the capacitive sensor into a voltage signal by using the above-mentioned capacitance-voltage conversion circuit;

3) Utilize the above-mentioned single-chip microcomputer to calculate the methanol concentration according to the voltage signal, and then use the above-mentioned dual CAN bus communication circuit to output to the automobile CAN bus.

Preferably, said step 2) specifically includes the following steps:

2.1) First, the methanol concentration of the mixed fuel is converted into an oscillation signal of a corresponding frequency by using the above-mentioned oscillator and a capacitive sensor;

2.2) Utilize the above-mentioned limiting amplifier to shape the oscillating signal to eliminate high-frequency interference signals;

2.3) Using the above-mentioned frequency discriminator to convert the shaped oscillation signal obtained in step 2.2) into a voltage signal, the magnitude of which reflects the concentration of methanol.

Preferably, the step 3) further includes the following step: simultaneously using the display interface circuit and the touch screen to display the concentration of methanol.

The beneficial effects of the present invention are reflected in:

The present invention adopts a capacitive sensor composed of arc-shaped plates, effectively increases the area of the plates, has better measurement sensitivity, not only can detect the concentration of methanol in the mixed fuel accurately in real time, but also improves the detection accuracy of methanol concentration, which can be used for The car ECU dynamically changes the fuel injection quantity of the engine to provide a more accurate reference, effectively reducing unnecessary fuel consumption while ensuring car power. The invention adopts the capacitance-voltage conversion circuit to process the signal of the measurement result of the capacitance sensor, and can obtain the precise methanol concentration signal.

Furthermore, the capacitance-voltage conversion circuit proposed by the present invention uses the oscillation, shaping and frequency discrimination functional modules to realize the detection of the methanol concentration signal, which improves the detection accuracy.

Furthermore, the display interface circuit and the dual CAN bus communication circuit proposed by the present invention can realize real-time display of methanol concentration and provide accurate and timely methanol concentration information for the automobile control system (ECU).

Description of drawings

Fig. 1 is a system structure block diagram of the present invention;

Fig. 2 is the structural representation of the arc plate (electrode) of capacitive sensor of the present invention;

Fig. 3 is the side schematic diagram of arc-shaped pole plate (electrode) of the present invention;

Fig. 4a is the circuit diagram of the signal processing module of the present invention;

Fig. 4 b is the circuit diagram of frequency discriminator, limiting amplifier and oscillator of the present invention;

Fig. 5 is the schematic diagram of double CAN bus communication circuit of the present invention;

Figure 6 is a schematic diagram of the connection between the capacitive sensor and the original fuel injection pipe of the automobile;

Figure 7 is a schematic diagram of the installation of the capacitive sensor in the fuel injection pipe;

In the figure: 1 is the fuel injection pipe section installed with the capacitive sensor; 2 is the reserved original fuel injection pipe section; 3 is the fuel injection pipe; 4 is the capacitive sensor; 5 is the bracket; 6 is the wire.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Referring to Fig. 1, the methanol concentration detection device of the present invention is composed of a host computer and a lower computer, and all detection functions are controlled by the lower computer, and then transmitted to the upper computer for display and output. The lower computer detects the concentration of methanol in the mixed fuel, and processes the concentration signal, calculates the methanol concentration according to the processed signal and sends it to the upper computer; the upper computer receives the signal from the lower computer and displays the methanol concentration information, the upper computer and the lower computer The machine communicates through the ModBus protocol.

The upper computer is composed of a display module. The display module adopts a Kunlun touch screen with built-in MCGS embedded configuration software, which can display the concentration of methanol in the current mixed fuel in real time. The lower computer is composed of measurement module and signal processing module. The touch screen receives the methanol concentration information sent by the signal processing module, and displays the methanol concentration information in the mixed fuel in real time. The signal processing module acquires (using the measurement module), processes the methanol concentration signal, and outputs methanol concentration information.

The measuring module includes an arc-shaped capacitive sensor 4 , which is completely placed in the fuel injection pipe 3 when the arc-shaped capacitive sensor 4 is actually used. See Figure 6, the installation method of the sensor is as follows: cut off a section of the original fuel injection pipe 3 of the car, and connect a section of the pipe with the sensor fixed inside to the gap of the fuel injection pipe 3 formed after the cut-off, so that the sensor is fixed on the fuel injection pipe of the car 3 middle positions. When the automobile engine injects fuel, the arc-shaped capacitive sensor 4 will be completely submerged in the mixed fuel of methanol and gasoline.

The signal processing module includes a capacitance-voltage conversion circuit, and the capacitance-voltage conversion circuit converts the methanol concentration signal. The signal processing module also includes a Freescale single-chip microcomputer, which digitally converts the analog voltage signal, calculates the methanol concentration according to the voltage-concentration formula and displays it, and then calculates the widening width according to the concentration-pulse width formula, which is used to sequentially control the fuel injection signal, and at the same time start the CAN bus for communication. The signal processing module also includes an RS232 serial interface circuit, and the RS232 serial interface circuit serves as an interface circuit (display interface circuit) for communication between the upper computer and the lower computer. The signal processing module also includes a dual CAN bus communication circuit, and the dual CAN bus communication circuit is used for communication between the signal processing module and the vehicle general control system, which effectively improves the reliability of system communication.

Referring to FIG. 2 , FIG. 3 and FIG. 7 , the arc-shaped capacitive sensor 4 includes a pair of opposite plates. The material of the polar plates is metal copper, and the surfaces of the two polar plates are uniformly covered with green oil as an insulating material, and four cylinders of nylon material (nylon has good corrosion resistance to methanol) are used on the opposite side (outer side) of the two polar plates. The body bracket 5 is fixed on the inner wall of the fuel injection pipe 3 . The shape of the pole plate is arc-shaped (that is, a part of the cylindrical surface intercepted along the circumference), protruding outward, its arc is 120 °, its length is 80mm, the diameter of the arc surface is 10mm, and the thickness is 0.5mm. The maximum distance between plates is 10mm (capacitive sensors composed of arc-shaped plates are called arc-shaped capacitive sensors, which have better measurement sensitivity by effectively increasing the area of the plates). The arc-shaped capacitive sensor 4 is placed in the fuel injection pipe 3 of the automobile. The section where the sensor is placed on the fuel injection pipe 3 of the automobile is made separately, with an inner diameter of 20mm and a length of 100mm. Each pole plate all leads out a wire 6, and its material is metallic copper, and the wire surface is all covered with green oil.

The capacitance model of the arc electrode is as follows:

In the formula, c is the capacitance value, and ε is the dielectric constant of methanol gasoline, which is determined by the concentration of methanol. It can be seen from the above formula that the capacitance value is proportional to the dielectric constant.

Referring to Fig. 4a, the capacitance-voltage conversion circuit includes an oscillator, a limiting amplifier and a frequency discriminator. The two polar plates of the arc-shaped capacitive sensor 4 are respectively connected to the oscillator through the wire 6, the oscillator is connected with the limiting amplifier, the limiting amplifier is connected with the frequency discriminator, and the frequency discriminator is connected with the flying discriminator. The Scale microcontroller is connected, and the Freescale SCM is connected with the RS232 serial interface circuit. The touch screen is connected with the RS232 serial interface circuit through a nine-pin serial port line DB9. The type selection of the Freescale microcontroller is MC9S12XEP100. The RS232 serial interface circuit uses MAX232 as the core device, and four 1uF capacitors C1, C2, C3, and C4 are configured on the periphery of the MAX232 to stably transmit and receive signals.

Referring to Fig. 4b, an oscillation circuit is composed of a chip 555, resistors _RA , _RB and an arc capacitor C (corresponding to an arc-shaped capacitive sensor). The output waveform period T is determined by _RA , _RB and arc capacitance C:

T＝0.7*(R _A +2R _B )*C

In the limiting amplifier, the impedance transformation circuit is composed of the operational amplifier OP07.

The filter circuit is composed of resistors R1, R2, R6 and capacitors C1, C2, C4, and the amplitude comparison circuit is composed of resistor R3 and capacitor C3.

The analog voltage signal is output by pin 1 of LM331. R5 and C3 form a charging circuit, and R3 and R4 form a voltage divider circuit.

Referring to Fig. 5, the methanol concentration detection device is installed on the automobile, and communicates with the ECU master control system of the automobile by using the CAN bus communication circuit. Since MC9S12XEP100 has 5 CAN modules, dual CAN communication is adopted to improve the anti-interference ability, TJA1050 is used for CAN drive, and a 120-ohm matching resistor is configured to eliminate terminal reflection.

The detection principle of the above-mentioned methanol concentration detection device is:

In the actual measurement, the arc-shaped capacitive sensor 4 is completely submerged in the methanol-gasoline mixed fuel, and at the same time, the two plates of the arc-shaped capacitive sensor 4 are connected to the oscillator circuit of the capacitance-voltage conversion circuit, see Fig. 4a, Figure 4b. After the detection device is powered on, the oscillator will charge and discharge the arc-shaped capacitive sensor 4 to generate periodic oscillation. The concentration of methanol in the mixed fuel is different, the corresponding dielectric constant and capacitance are different, and the oscillation signal generated by the oscillator is different. The frequency is also different. The oscillating signal is shaped by the limiting amplifier in the capacitor-voltage conversion circuit, and the shaped signal is converted into a voltage signal by a frequency discriminator, which is an analog signal. The analog voltage signal is sent to the Freescale microcontroller, which converts the analog voltage signal into a digital signal, calculates the methanol concentration according to the voltage-concentration formula, and sends it to the touch screen through the RS232 serial interface circuit. After the touch screen receives the signal Displays methanol concentration information.

In a word, the structure design of the present invention is reasonable, and the function division is clear. The functional modules cooperate with each other, can accurately and quickly detect the concentration of methanol in the mixed fuel, and can display the concentration information in real time.

Claims (9)

1. a kind of methanol concentration detection device, it is characterised in that：The detection device includes measurement module, and the measurement module includes Capacitance type sensor (4), the capacitance type sensor (4) use arc pole plate.

2. a kind of methanol concentration detection device according to claim 1, it is characterised in that：The arc pole plate includes by metal Ontology and uniform fold made of copper in the corrosion resistant insulation material layer of the body surface, the insulation material layer with a thickness of 0.05-0.1mm。

3. a kind of methanol concentration detection device according to claim 1, it is characterised in that：Capacitance type sensor (4) packet Two opposite arc pole plates are included, arc pole plate is the arc surface that radian is 120 °, and cambered surface internal diameter is 10mm, the length of arc pole plate Degree and thickness are respectively 80mm and 0.5mm, and the maximum spacing of two arc pole plates is 10mm.

4. a kind of methanol concentration detection device according to claim 1, it is characterised in that：The capacitance type sensor (4) sets It is placed in the spray bar (3) of fuel combination automobile to be measured, the spray bar (3) includes the section for installing arc pole plate, should The internal diameter of section is 20mm, length 100mm.

5. a kind of methanol concentration detection device according to claim 1, it is characterised in that：The arc pole plate is along the oil spout Pipe (3) central axis is arranged symmetrically, and passes through nylon mounting bracket (5) between convex side and spray bar (3) inner wall of arc pole plate It is fixed.

6. a kind of methanol concentration detection device according to claim 1, it is characterised in that：The detection device further includes signal Processing module and display module, the signal processing module include capacitance-voltage conversion circuit, single-chip microcontroller, display interface circuit And CAN bus telecommunication circuit；The capacitance-voltage conversion circuit includes the oscillator, limiting amplifier and mirror being sequentially connected Frequency device, oscillator are connected with the capacitance type sensor (4), frequency discriminator, display interface circuit and CAN bus telecommunication circuit point It is not connected with single-chip microcontroller, display module includes the touch screen being connected with display interface circuit.

7. a kind of methanol concentration detection method, it is characterised in that：Include the following steps：

1) capacitance type sensor (4) is placed in the spray bar (3) of fuel combination automobile to be measured, capacitance type sensor (4) uses Arc pole plate；

2) methanol concentration of fuel combination in spray bar (3) is measured using capacitance type sensor (4), by capacitive sensing The measurement result of device (4) is converted to voltage signal；

3) methanol concentration is calculated according to voltage signal, be then output in the CAN bus of the automobile.

8. a kind of methanol concentration detection method according to claim 7, it is characterised in that：The step 2) specifically includes following Step：

2.1) methanol concentration of fuel combination is converted to the vibration of respective frequencies first with oscillator and capacitance type sensor (4) Swing signal；

2.2) shaping is carried out to oscillator signal using limiting amplifier；

2.3) oscillator signal Jing Guo shaping is converted into voltage signal using frequency discriminator.

9. a kind of methanol concentration detection method according to claim 7, it is characterised in that：The step 3) further includes following step Suddenly：Methanol concentration is shown simultaneously.