KR100812423B1 - Method for calculating concentration of ethanol in fuel and apparatus for the same - Google Patents

Abstract

A method for calculating concentration of ethanol in fuel and a device of the same are provided to reduce manufacturing cost for an ethanol vehicle and to accurately compute ignition time, and fuel amount by using an oxygen sensor. A method for calculating concentration of ethanol in fuel comprises the steps: supplying fuel from cold-start fuel tank(14) which is storing only gasoline, to an engine; calculating a first learning value by subtracting a theory learning value from measured learning value; stopping fuel supply from the cold-start fuel tank and supplying fuel from a main fuel tank(11) to the engine; calculating a second learning value by using an oxygen sensor(17); and calculating concentration of ethanol by subtracting the first learning value from the second learning value.

Description

METHODS FOR CALCULATING CONCENTRATION OF ETHANOL IN FUEL AND APPARATUS FOR THE SAME

1 is a graph showing the theoretical performance ratio according to the gasoline concentration.

Figure 2 is a schematic diagram showing the configuration of the ethanol concentration calculation apparatus according to an embodiment of the present invention.

The present invention relates to a method and apparatus for calculating the ethanol concentration in fuel, and more particularly to a method and apparatus for calculating the ethanol concentration for calculating the exact ethanol concentration in consideration of the effects of hardware distortion using gasoline of the cold start fuel tank will be.

Recently, vehicles using ethanol fuel in place of gasoline vehicles have been actively developed. In general, ethanol vehicles are powered by bio ethanol, an alcohol made from plants instead of gasoline, and a fuel capable of minimizing heat generated by ethanol combustion for ethanol vehicles or coping with corrosion and condensation caused by the use of ethanol. Technological advances are being made in system components. In the following, the term ethanol is intended to include the concept of alcohol.

Vehicles using ethanol fuel have various specifications, such as using 10% ethanol mixed with gasoline or 100% ethanol. Especially in the case of FFV (Flexible Fuel Vehicle), the concentration of ethanol is from 0% to 100%. Fuels varying by% will be injected.

Since the concentration of ethanol contained in the fuel is variable as described above, it is essential to accurately measure the ethanol concentration in the fuel in a vehicle using the ethanol fuel. This is because the indication values such as the ignition timing and the fuel amount have to be changed according to the concentration of ethanol. For example, in fuel, the theoretical performance ratio is 9.0 when 100% ethanol and 0% gasoline, and the theoretical air-fuel ratio is 14.7 when 0% ethanol and 100% gasoline. The air-fuel ratio will change.

Conventionally, in order to measure the concentration of ethanol contained in the fuel, an expensive ethanol concentration sensor was mounted in the middle of the fuel line from the fuel tank to the fuel injection device. Increasing costs have been inevitable.

Therefore, a method of estimating ethanol concentration in fuel by using an air-fuel ratio shift, using only an oxygen sensor installed in an existing gasoline engine without using an ethanol concentration sensor, has been studied.

However, there is a problem in the method of estimating the concentration of ethanol using the learning amount by the oxygen sensor. In other words, when the ethanol concentration is estimated by the relationship between the theoretical air-fuel ratio and the ethanol concentration using the learning amount of the oxygen sensor, the air-fuel ratio caused by the hardware distortion is not reflected and the exact ethanol concentration cannot be obtained.

The present invention provides a method and apparatus for calculating an accurate ethanol concentration in a fuel without using an ethanol concentration sensor and reflecting an air-fuel ratio caused by a hardware distortion when the ethanol concentration is calculated using an oxygen sensor. For the purpose of

The method for calculating the ethanol concentration in fuel according to the present invention is a method for calculating the ethanol concentration in fuel in a vehicle that can store and use a gasoline and ethanol mixed fuel in a main fuel tank. Supplying fuel to the fuel, calculating a first learning value by subtracting the theoretical learning value from the learning value measured by the oxygen sensor mounted to the exhaust port of the engine, stopping the fuel supply from the cold start fuel tank, Starting fuel supply from the fuel tank to the engine, calculating a second learning value by an oxygen sensor, and subtracting the first learning value from the second learning value to calculate the ethanol concentration value from the learning value calculated. Steps.

In addition, the ethanol calculation device in the fuel of the present invention includes a main fuel tank for storing fuel mixed with gasoline and ethanol, a cold starting fuel tank storing only gasoline, a main fuel tank, and an engine supplied with fuel from the cold starting fuel tank. A main body, an oxygen sensor mounted to an exhaust port of the engine main body, and a control unit for controlling fuel supply from the main fuel tank and the cold start fuel tank to the engine main body, wherein the control unit supplies fuel from the cold start fuel tank to the engine. To calculate the first learning value by subtracting the theoretical learning value from the learning value measured by the oxygen sensor, stopping the fuel supply from the cold start fuel tank, and starting the fuel supply from the main fuel tank to the engine. And calculating the second learning value measured by the oxygen sensor, subtracting the first learning value from the second learning value, and ethanol by the learning value calculated. Calculate the dogap.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a graph showing the theoretical performance ratio according to the gasoline concentration. The horizontal axis represents the gasoline concentration in the fuel. Gasoline concentrations can be from 0% to 100%, which is the ethanol concentration when calculating the 100-gasoline concentration. That is, the ethanol concentration changes from 100% to 0% as it goes to the right direction on the horizontal axis.

The vertical axis is the theoretical performance ratio, the theoretical performance ratio is 9 when the gasoline concentration is 0%, and the theoretical performance ratio is 14.7 when the gasoline concentration is 100%. This may vary depending on the configuration of the engine and the value is an example.

Since the theoretical performance ratio is 9 when the gasoline concentration is 0% and the theoretical performance ratio is 14.7 when the gasoline concentration is 100%, and the theoretical performance ratio generally increases linearly with the gasoline concentration, a graph of a straight line as shown in FIG. The linear interpolation can be used to calculate the theoretical fuel ratio and gasoline concentration. In the case of FIG. 1, the calculation formula of the theoretical performance ratio y according to gasoline concentration x (%) is y = 0.057x + 9. Therefore, if the theoretical performance ratio y is known, gasoline concentration x can be computed by the formula of x = (y-9) /0.057 (henceforth "expression 1").

The learning value obtained from the oxygen sensor mounted on the exhaust port of the engine main body is 1 when the gasoline concentration is 100% and 1.33 when the gasoline concentration is 0% (ethanol concentration 100%). If there is no ethanol concentration sensor, the method of calculating the ethanol concentration by the learning value of the oxygen sensor is as follows.

When the learning value of the oxygen sensor is 1.2, for example, the variation value of the theoretical performance ratio is 0.2 x 14.7, which is 2.94. Therefore, the theoretical performance ratio is calculated as 14.7-2.94 = 11.76, and since y = 11.76 in Equation 1, the gasoline concentration x is (11.76-9) /0.057=48.4%, and the ethanol concentration is 100-48.4 = 51.6 (%). It is a calculation. Therefore, without using an ethanol concentration sensor, it is possible to extract the indication value, such as the ignition timing, fuel amount according to the calculated ethanol concentration using the learning value of the oxygen sensor.

However, there is a problem even when calculating the ethanol concentration using the learning value of the oxygen sensor in this way. That is, even if the engine is in the same assembly state, hardware distortion caused by the difference between the engines of the hardware such as various sensors, injectors, and intake machines generally occurs about ± 4%, and this hardware distortion affects the air-fuel ratio distortion value. When the ethanol concentration is calculated using only the learning value of the oxygen sensor as described above, the air-fuel ratio shift due to the hardware distortion is not reflected, and the exact ethanol concentration cannot be calculated.

Therefore, the calculation of the ignition timing, fuel amount, etc., based on the incorrectly calculated ethanol concentration adversely affects the smooth running of the vehicle. Hereinafter, a method and apparatus for calculating the ethanol concentration by the learning value of the oxygen sensor reflecting the air-fuel ratio distortion caused by the hardware distortion will be described.

Figure 2 is a schematic diagram showing the configuration of the ethanol concentration calculation apparatus according to an embodiment of the present invention. The engine main body 10 includes a spark plug, a piston, and the like, and is used in a general engine as a part for repeatedly generating an driving force of a vehicle by repeating an explosion with fuel and air supplied.

In this engine body 10, fuel supplied from the main fuel tank 11 through the fuel line 12 is injected through the fuel injection device 13, and the fuel is supplied by the air supply unit 16. Mixed with The main fuel tank 11 stores fuel mixed with ethanol and gasoline.

In the case of ethanol, since cold start is not good, in the case of ethanol, a cold start fuel tank 14 for cold start is provided separately from the main fuel tank 11, and during cold start, the cold start fuel injector 15 is provided. Refuel. In the cold start fuel tank 14, 100% of gasoline fuel is stored. And the oxygen sensor 17 is mounted on the exhaust port of the engine main body 10 to measure the oxygen concentration, so that the control unit (not shown) of the vehicle can calculate the ethanol concentration by the learning value of the oxygen sensor.

According to an embodiment of the present invention, a method of measuring an accurate ethanol concentration sensor by reflecting the air-fuel ratio distortion caused by the hardware (various sensors, injectors, intake, etc.) is as follows.

In the present invention, by using the cold start fuel tank 14 provided for cold start, the air-fuel ratio shift due to the hardware twist is calculated and used for the ethanol concentration calculation. If the engine is sufficiently warmed up when the fuel is injected into the main fuel tank 11 of the vehicle or when a predetermined time has elapsed, and the vehicle has traveled a certain traveling distance, the controller supplies the fuel supply from the main fuel tank 11. It stops and the fuel supply from the cold start fuel tank 14 is started. In the cold start fuel tank 14, 100% of gasoline fuel is stored.

In theory, for 100% gasoline, the learning value of the oxygen sensor should be 1.0. However, due to hardware distortion, the learning value of the oxygen sensor can deviate from 1.0, and fuel is supplied to the engine main body 10 from the cold start fuel tank 14 storing 100% of gasoline, and the oxygen sensor 17 By measuring the oxygen concentration it is possible to calculate the distortion of the hardware.

It is assumed that fuel is supplied from the cold start fuel tank 14 to the engine main body 10, and the learning value of the oxygen sensor is measured to be 1.03. If there is no hardware distortion, the theoretical learning value of the oxygen sensor should be 1.00 when 100% of gasoline fuel is supplied, and the learning value of the oxygen sensor is 1.03 due to the hardware distortion. Therefore, the value 0.03 (first learning value) can be regarded as a misalignment value of hardware.

The control unit memorizes this value 0.03, stops the fuel supply from the cold start fuel tank 14 and resumes the fuel supply from the main fuel tank 11. Assuming that the learning value of the oxygen sensor is calculated as an average of 1.23 (second learning value) when fuel is supplied from the main fuel tank 11, since the value of 0.03 here is a value due to hardware misalignment, When calculating the ethanol concentration by the learning value, the calculation is performed except for the value of 0.03. That is, the learning value of the oxygen sensor is subtracted from the learning value 1.23 (second learning value) of the oxygen sensor by subtracting the learning value 0.03 (first learning value) of the oxygen sensor when fuel is supplied from the cold start fuel tank 14. When the ethanol concentration is calculated as 1.2, the ethanol concentration becomes 51.6% as described above.

If the ethanol concentration is calculated using the learning value of the oxygen sensor as 1.23 without considering the hardware distortion, it is calculated to be different from 51.6%, and the ignition timing and fuel amount are calculated based on the incorrectly calculated ethanol concentration. As a result, it will adversely affect the smooth running of the vehicle.

By using the fuel stored in the gasoline 100% cold-start fuel tank which is generally provided in the ethanol fuel vehicle, the air-fuel ratio caused by the hardware can be compensated for whenever the predetermined conditions are satisfied, thereby providing an ethanol concentration sensor. Instead, when the ethanol concentration is calculated by the learning value of the oxygen sensor, the exact ethanol concentration can be calculated.

Then, a method of modeling the ignition timing based on the ethanol concentration obtained as described above is proposed. Usually, RON (octane number) value of ethanol is 107, and RON value of gasoline is 92 (variable according to gasoline type). When ethanol and gasoline are mixed, the RON value changes proportionally. For example, when 80% of ethanol and 20% of gasoline are mixed, the RON value is 107 × 0.8 + 92 × 0.2 = 104. However, when the RON value is 97 or more, knocking does not occur, so that the spark can be made into MBT (Minimum spark advance for Best Torque), and as the ethanol concentration increases, the combustion speed increases and the MBT is perceived. In other words, the ignition timing is increased by increasing the ignition timing from 0% at 33% to, for example, 33%, and the ignition timing is decreased by knocking from 33% to 100%. As the ethanol concentration increases as described above, the ignition timing tends to fall after a certain concentration after the rise, and it is found that it is desirable to model the quadratic curve.

Therefore, in the present invention, the secondary curve coefficient is obtained using the relationship between the ethanol concentration and the ignition timing, and the ignition timing according to the ethanol concentration is determined by using the same. First, a, b of y = ax ² + bx + c (where y is the ignition timing and x is the ethanol concentration) by a test at a specific ethanol concentration, for example 0%, 33%, 80%, 100% Calculate the coefficient of, c, table a, b, c values according to each rotation speed and engine load, and when driving the vehicle, refer to this table to ignite the ethanol concentration according to the specific rotation speed and engine load. You can decide when. In this way, the method of determining the ignition timing according to the ethanol concentration can also be used to determine the fuel amount according to the ethanol concentration.

Therefore, it is possible to prevent the ignition timing caused by inaccurate control and the increase in fuel amount, thereby improving fuel economy, and in the case of inaccuracy, the ignition timing is set to be much lower than the dangerous level, which may cause deterioration of vehicle performance. According to the present invention, the ignition timing can be optimally set, and the performance of the vehicle can be improved.

According to the present invention, since the ethanol concentration is calculated without using the ethanol concentration sensor, the manufacturing cost of the ethanol vehicle can be greatly reduced, and the air-fuel ratio is distorted due to hardware distortion when the ethanol concentration is calculated using the oxygen sensor. By calculating the exact ethanol concentration in the fuel reflecting this, it is possible to calculate the exact ethanol concentration, it is possible to accurately extract the indication values such as the ignition timing, the fuel amount.

Claims (2)

As a method of calculating the ethanol concentration in fuel in a vehicle that can store a mixture of gasoline and ethanol in the main fuel tank, Supplying fuel to the engine from a cold start fuel tank storing only gasoline, Calculating a first learning value by subtracting a theoretical learning value from the learning value measured by an oxygen sensor mounted at an exhaust port of the engine, Stopping fuel supply from the cold start fuel tank and starting fuel supply from the main fuel tank to the engine, Calculating a second learning value by the oxygen sensor, and And calculating the ethanol concentration value by the learning value calculated by subtracting the first learning value from the second learning value. A main fuel tank for storing fuel mixed with gasoline and ethanol, a cold start fuel tank storing only gasoline, an engine body supplied with fuel from the main fuel tank and the cold start fuel tank, and oxygen mounted in an exhaust port of the engine body An apparatus for calculating the ethanol concentration in fuel in a vehicle having a sensor and a control unit for controlling a fuel supply from the main fuel tank and the cold start fuel tank to an engine main body, The control unit, Starting fuel supply from the cold start fuel tank to the engine, Calculating a first learning value by subtracting a theoretical learning value from the learning value measured by the oxygen sensor, Stopping fuel supply from the cold start fuel tank, starting fuel supply from the main fuel tank to the engine, By calculating a second learning value measured by the oxygen sensor, And calculating the ethanol concentration by the learning value calculated by subtracting the first learning value from the second learning value.

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