JP4696904B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine that can be used by mixing a plurality of fuels.

  For example, in an internal combustion engine using gasoline as fuel, the maximum output can be obtained on the rich side (for example, 12.5) from the stoichiometric air-fuel ratio. This is because by setting the rich air-fuel ratio, the combustion temperature decreases, so that thermal dissociation can be suppressed. Therefore, in the full load state, it is made richer than the theoretical air-fuel ratio. By the way, the theoretical air-fuel ratio differs depending on the fuel. Therefore, when a plurality of fuels are mixed, the theoretical air-fuel ratio varies depending on the mixing ratio. Therefore, a technique for performing feedback control while correcting the theoretical air-fuel ratio based on the fuel mixing ratio is known. (For example, refer to Patent Document 1).

For example, in an internal combustion engine using gasoline as fuel, the fuel amount is corrected by multiplying the fuel amount at the stoichiometric air-fuel ratio by a certain correction coefficient in order to make the air-fuel ratio rich when obtaining the maximum output. Is going. If such a correction is applied as it is to an internal combustion engine that uses a mixture of a plurality of fuels, the maximum output may not be obtained. This is because different fuel types have different combustion temperatures, so that the air-fuel ratio at which the maximum output can be obtained is also different.
Japanese Utility Model Publication No. 6-34599 Japanese Patent Laid-Open No. 5-18282

  The present invention has been made in view of the above-described problems, and provides a technique capable of obtaining a maximum output at the concentration even when a plurality of fuels are mixed in a fuel supply device for an internal combustion engine. For the purpose.

In order to achieve the above object, the internal combustion engine fuel supply apparatus according to the present invention employs the following means. That is, the fuel supply device for an internal combustion engine according to the present invention includes:
A fuel supply device for an internal combustion engine using a mixture of a plurality of fuels,
Fuel supply means for supplying fuel to the internal combustion engine;
Load detecting means for detecting or estimating the load of the internal combustion engine;
Fuel concentration detecting means for detecting the concentration of a predetermined type of fuel supplied to the internal combustion engine;
Intake air amount detection means for detecting or estimating the intake air amount of the internal combustion engine;
A theoretical air-fuel ratio fuel amount calculating means for calculating a fuel supply amount that becomes a theoretical air-fuel ratio based on the intake air amount of the internal combustion engine and the concentration detected by the fuel concentration detecting means;
When the load detected by the load detecting means is equal to or higher than a predetermined load and when more fuel is supplied than the fuel supply amount calculated by the theoretical air-fuel ratio fuel amount calculating means, the fuel concentration detecting means A fuel amount changing means having a rich degree to obtain a maximum output according to the concentration detected by
It is characterized by comprising.

The internal combustion engine uses a mixture of a plurality of fuels as a mixed fuel. The stoichiometric air-fuel ratio of the mixed fuel varies depending on the stoichiometric air-fuel ratio of each fuel contained in the mixed fuel and the ratio of each fuel. Here, the theoretical air-fuel ratio of each fuel can be obtained in advance as the theoretical air-fuel ratio of the fuel that is expected to be mixed. The ratio of each fuel can be detected by the fuel concentration detecting means. Then, the theoretical air-fuel ratio fuel amount calculating means can calculate the fuel supply amount in the intake air amount at that time based on the intake air amount of the internal combustion engine and the theoretical air-fuel ratio of the mixed fuel.

  Here, when the combustion temperature is lowered by setting the rich air-fuel ratio, the output of the internal combustion engine is improved. For example, when a mixed fuel with a high proportion of fuel having a low combustion temperature is used, the degree of enrichment may be relatively small. Thus, by changing the degree of richness according to the concentration detected by the fuel concentration detecting means, the maximum output of the mixed fuel at that time can be obtained. The “predetermined load” may be a full load or a load near the full load, and may be a load that requires a maximum output for the internal combustion engine.

  According to the present invention, the maximum output at the concentration can be obtained even when a plurality of fuels are mixed.

  Hereinafter, specific embodiments of a fuel supply device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which a fuel supply device for an internal combustion engine according to the present embodiment is applied, and an intake system and an exhaust system thereof. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle engine. The internal combustion engine 1 can use a mixed fuel in which gasoline and alcohol are mixed at an arbitrary ratio.

  An intake passage 3 that leads to the combustion chamber 2 is connected to the internal combustion engine 1. An air flow meter 4 for measuring the intake air amount of the internal combustion engine 1 is attached in the middle of the intake passage 3. The air flow meter 4 in this embodiment corresponds to the intake air amount detection means in the present invention. A throttle 5 is provided in the intake passage 3 closer to the internal combustion engine 1 than the air flow meter 4. A throttle opening sensor 51 that outputs a signal corresponding to the opening of the throttle 5 is attached to the throttle 5. The load on the internal combustion engine 1 can be detected from the output signal of the throttle opening sensor 51. In this embodiment, the throttle opening sensor 51 corresponds to the load detecting means in the present invention.

  A fuel injection valve 6 that injects fuel into the intake passage 3 is attached to the intake passage 3 closer to the internal combustion engine 1 than the throttle 5. In this embodiment, the fuel injection valve 6 corresponds to the fuel supply means in the present invention. A fuel supply pipe 61 is connected to the fuel injection valve 6, and fuel flows in the fuel supply pipe 61. Further, an alcohol concentration sensor 62 for detecting the alcohol concentration of the fuel flowing through the fuel supply pipe 61 is attached to the fuel supply pipe 61. In this embodiment, the alcohol concentration sensor 62 corresponds to the fuel concentration detecting means in the present invention.

  On the other hand, an exhaust passage 7 leading to the combustion chamber 2 is connected to the internal combustion engine 1. An air-fuel ratio sensor 8 for detecting the air-fuel ratio of the exhaust gas flowing through the exhaust passage 7 is attached in the middle of the exhaust passage 7.

The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 controls the operation state of the internal combustion engine 1 according to the operation conditions of the internal combustion engine 1 and the request of the driver. The ECU 10 is connected to the sensors via electrical wiring, and the output signals of these sensors are input. On the other hand, the fuel injection valve 6 is connected to the ECU 10 through electric wiring, and the fuel injection valve 6 is controlled by the ECU 10.

  In this embodiment, when the internal combustion engine 1 is operated at a partial load, the fuel injection amount is determined with the theoretical air-fuel ratio (or the excess air ratio being 1) as a target. That is, the amount of fuel injected from the fuel injection valve 6 is feedback controlled so that the air-fuel ratio detected by the air-fuel ratio sensor 8 becomes the stoichiometric air-fuel ratio. Here, the theoretical air-fuel ratio varies depending on the alcohol concentration. Therefore, the target theoretical air-fuel ratio is determined based on the alcohol concentration obtained by the alcohol concentration sensor 62.

  On the other hand, at the full load and in the vicinity thereof, the fuel injection amount is determined with the target of the air / fuel ratio (hereinafter referred to as the output air / fuel ratio) at which the output of the internal combustion engine 1 is maximum. The output air-fuel ratio is richer than the stoichiometric air-fuel ratio and varies depending on the alcohol concentration. Therefore, in this embodiment, the degree of richness from the stoichiometric air-fuel ratio is changed according to the alcohol concentration.

  Next, the calculation flow of the fuel supply amount according to this embodiment will be described. FIG. 2 is a flowchart showing a flow of calculating the fuel supply amount according to this embodiment. This routine is repeatedly executed every predetermined time.

  In step S101, the alcohol concentration is read. In this step, the alcohol concentration of the fuel is detected by the alcohol concentration sensor 62, and the value is stored in the ECU 10. Instead of using the alcohol concentration sensor 62, the alcohol concentration may be estimated from a feedback value at the time of feedback control of the fuel supply amount based on the air-fuel ratio detected by the air-fuel ratio sensor 8.

  In step S102, the intake air amount is read. In this step, the intake air amount of the internal combustion engine 1 is detected by the air flow meter 4 and the value is stored in the ECU 10.

  In step S103, the basic injection amount A when the alcohol concentration is 0 is calculated. The basic injection amount A is a fuel injection amount that can obtain a theoretical air-fuel ratio when the fuel is assumed to be only gasoline. That is, in this step, the basic injection amount A is calculated by dividing the intake air amount by the theoretical air fuel ratio of gasoline.

  In step S104, the fuel injection amount when the internal combustion engine 1 is operated at a partial load is calculated. In this step, the fuel injection amount for obtaining the stoichiometric air-fuel ratio in the mixed fuel is calculated based on the alcohol concentration. In addition, correction that is normally performed in an internal combustion engine, such as the amount of fuel injected from the fuel injection valve 6 to the intake passage 3, is also performed. In this step, the fuel injection amount F is calculated by the following equation.

  F = (A ・ C + D) ・ B

  However, A is a basic injection amount, B is a correction coefficient based on the alcohol concentration, and C and D are correction coefficients for correction conventionally performed in an internal combustion engine.

  A correction coefficient B based on the alcohol concentration (hereinafter referred to as a concentration correction coefficient B) can be obtained based on the map shown in FIG. Here, FIG. 3 is a diagram showing the relationship between the alcohol concentration and the concentration correction coefficient B. The concentration correction coefficient B is set so that the fuel injection amount F increases as the alcohol concentration increases. That is, the higher the alcohol concentration, the lower the stoichiometric air-fuel ratio of the mixed fuel. This is because the theoretical air-fuel ratio of alcohol is lower than that of gasoline.

  Since the standard injection amount A is based on gasoline-only fuel, the concentration correction coefficient B is 1 when the alcohol concentration is 0%. Further, when the alcohol concentration is 100% (in FIG. 3, when the concentration correction coefficient B is 1.55), the fuel injection amount is such that a theoretical air-fuel ratio can be obtained when only alcohol fuel is used. The fuel injection amount F may be obtained in the same manner as in the prior art. In this embodiment, the ECU 10 that calculates the fuel injection amount F corresponds to the theoretical air-fuel ratio fuel amount calculation means in the present invention.

  In step S105, it is determined whether the opening of the throttle 5 is equal to or greater than a predetermined opening. The predetermined opening is an opening at which the internal combustion engine 1 can be assumed to be full load. This is because the full load state is reached when the opening of the throttle 5 is large. Further, instead of the opening of the throttle 5, it may be determined whether or not the intake air amount is a predetermined amount or more. In this step, it is determined whether or not fuel increase for generating the maximum output is necessary. That is, it is determined whether or not the output air-fuel ratio needs to be set. If an affirmative determination is made in step S105, the process proceeds to step S106, whereas if a negative determination is made, the process proceeds to step S107.

  In step S106, a value obtained by multiplying the fuel injection amount F by the output air-fuel ratio correction coefficient P is newly set as the fuel injection amount F. That is, the fuel injection amount F is updated by the following equation.

  F = F ・ P

The output air-fuel ratio correction coefficient P is a correction coefficient determined according to the alcohol concentration, and is a coefficient for obtaining a fuel injection amount for obtaining a maximum output. The output air-fuel ratio correction coefficient P can be obtained based on the map shown in FIG. Here, FIG. 4 is a diagram showing the relationship between the alcohol concentration and the output air-fuel ratio correction coefficient P. Excess air ratio maximum output is obtained by the fuel gasoline only (e.g. lambda = 0.85), and excess air ratio the maximum output is obtained at an alcohol concentration of that time, the P ratio output air-fuel ratio correction coefficient Become. The excess air ratio at which the maximum output can be obtained can be obtained in advance by experiments or the like. In this step, the fuel injection amount increase control may be performed to suppress overheating of the catalyst. In this embodiment, the ECU 10 that executes the process of step S106 corresponds to the fuel amount changing means in the present invention.

  In step S107, feedback control of the fuel injection amount is performed in order to set the air-fuel ratio obtained by the air-fuel ratio sensor 8 to the target air-fuel ratio. The target air-fuel ratio is, for example, a theoretical air-fuel ratio that is determined according to the alcohol concentration at that time, and is determined in advance through experiments or the like. Then, a new fuel injection amount F is set by feedback control. Thus, in this embodiment, the fuel injection amount is determined with the theoretical air-fuel ratio as a target, except when the maximum output is obtained. This feedback control can also use a conventional technique.

  In step S108, in order to inject the fuel injection amount F from the fuel injection valve 6, the valve opening time of the fuel injection valve 6 is determined, and a signal is sent to the fuel injection valve 6 so as to be the valve opening time. Thus, an amount of fuel corresponding to the load at that time is supplied.

  As described above, according to the present embodiment, by changing the fuel injection amount based on the alcohol concentration at the full load of the internal combustion engine 1 and the load in the vicinity thereof, the maximum fuel with the alcohol concentration at that time can be obtained. Output can be obtained.

It is a figure which shows schematic structure of the internal combustion engine which applies the fuel supply apparatus of the internal combustion engine which concerns on an Example, and its intake system and exhaust system. It is the flowchart which showed the calculation flow of the fuel supply amount which concerns on an Example. It is the figure which showed the relationship between alcohol concentration and the density | concentration correction coefficient B. It is the figure which showed the relationship between alcohol concentration and the output air fuel ratio correction coefficient P.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Combustion chamber 3 Intake passage 4 Air flow meter 5 Throttle 51 Throttle opening sensor 6 Fuel injection valve 61 Fuel supply pipe 62 Alcohol concentration sensor 7 Exhaust passage 8 Air-fuel ratio sensor 10 ECU

Claims (2)

A fuel supply device for an internal combustion engine using a mixture of a plurality of fuels,
Fuel supply means for supplying fuel to the internal combustion engine;
Load detecting means for detecting or estimating the load of the internal combustion engine;
Fuel concentration detecting means for detecting the concentration of a predetermined type of fuel supplied to the internal combustion engine;
Intake air amount detection means for detecting or estimating the intake air amount of the internal combustion engine;
A theoretical air-fuel ratio fuel amount calculating means for calculating a fuel supply amount that becomes a theoretical air-fuel ratio based on the intake air amount of the internal combustion engine and the concentration detected by the fuel concentration detecting means;
When the load detected by the load detecting means is equal to or higher than a predetermined load and when more fuel is supplied than the fuel supply amount calculated by the theoretical air-fuel ratio fuel amount calculating means, the fuel concentration detecting means A fuel amount changing means having a rich degree to obtain a maximum output according to the concentration detected by
A fuel supply device for an internal combustion engine, comprising:   The internal combustion engine uses a mixture of alcohol and gasoline,
  The fuel concentration detection means detects the concentration of alcohol,
  2. The fuel supply device for an internal combustion engine according to claim 1, wherein the fuel amount changing means increases the rich degree as the alcohol concentration detected by the fuel concentration detecting means is higher.

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