JP4457803B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that supplies and operates a plurality of types of fuels having different properties at an arbitrary supply ratio.

2. Description of the Related Art There are known multi-fuel supply internal combustion engines that are operated by supplying a plurality of types of fuels having different properties to a engine at a predetermined supply rate.
For example, this type of engine includes a fuel supply device that supplies a plurality of types of fuels having different octane numbers to the engine at an arbitrary supply ratio, and the fuel is operated according to the engine operating conditions or other appropriate conditions during engine operation. Some supply to the engine by changing the supply ratio.

  In this way, by changing the supply ratio of high-octane gasoline and low-octane gasoline according to the operating conditions, the engine is operated to change the overall octane number of the fuel supplied to the engine according to the operating conditions. Therefore, it becomes possible to select an optimal fuel octane number according to each operating condition.

  For example, during operation after engine cold start, etc., the supply ratio of low-octane gasoline with good ignitability is increased to stabilize engine combustion, or the supply ratio of high-octane gasoline is increased during high-load operation of the engine. Thus, it is possible to supply the engine with a fuel having an octane number suitable for each operating condition such as increasing the octane number of the fuel and increasing the engine output by advancing the ignition timing.

  On the other hand, in order to prevent the evaporated fuel from the fuel tank from being released into the atmosphere, the fuel vapor generated in the tank is led to a canister containing an adsorbent such as activated carbon, and the fuel vapor is adsorbed on the adsorbent. Evaporative purge systems that prevent the release of fuel vapor to the atmosphere are generally known.

In the evaporative purge system, normally, in order to prevent the adsorbent of the canister from being saturated with the adsorbed fuel vapor, purge air is passed through the canister under the predetermined operating condition of the engine, and the adsorbed fuel vapor is adsorbed. In addition, a mixture of purge air and desorbed fuel vapor (purge mixture) is introduced into the engine and burned in the engine.
Normally, an engine that supplies multiple fuels with different properties, such as high-octane gasoline and low-octane gasoline, has a fuel tank for each fuel and supplies fuel to the engine from each fuel tank. A system canister is also provided for each fuel tank.

Although not an evaporative purge system for a multiple fuel engine, an example of an evaporative purge system that targets multiple vapors with different properties is disclosed in Patent Document 1, for example.
In the evaporation purge system of Patent Document 1, fuel vapor generated in a single fuel tank is separated into a high-boiling component and a low-boiling component by a separation membrane, and a canister having appropriate adsorption performance for each component is provided. Used to adsorb high-boiling components and low-boiling components individually.

  In the evaporative purge system of Patent Document 1, only the low-boiling component canister is used when the engine intake passage negative pressure is small (the absolute pressure is high), and low boiling point when the negative pressure is large (the absolute pressure is low). Both the component and high boiling point canisters are purged, and the adsorbed fuel vapor is introduced into the engine.

JP-A-4-194356 Japanese Patent Laid-Open No. 9-42022 JP 11-315733 A JP 2000-179368 A

  When the canister is purged by the evaporation purge system, the fuel vapor in the purge mixture is supplied to the combustion chamber in addition to the normal fuel supplied from the fuel injection valve or the like to the engine. Normally, for example, when feedback control of the engine air-fuel ratio is performed based on the output of the air-fuel ratio sensor provided in the exhaust passage, even if fuel vapor is supplied to the engine by canister purge, the output of the air-fuel ratio sensor is increased. Based on this, the engine fuel injection amount is feedback controlled so that the engine air-fuel ratio becomes the target value. Therefore, the engine air-fuel ratio is not affected by the presence or absence of purge.

In an engine evaporative purge system having a plurality of fuel tanks for fuels having different properties as described above, a canister is provided for each fuel tank. Therefore, when each canister is purged, the properties (such as octane number) are obtained from each canister. Different fuel vapors are supplied to the engine.
Also in this case, if the engine performs air-fuel ratio feedback control, the fuel injection amount is adjusted according to the fuel vapor supplied as the purge mixture as in the case of a single fuel, so the engine air-fuel ratio is purged. Will not be affected by.

  However, in this case, since a plurality of types of fuel vapors having different octane numbers are supplied from each canister, the octane number of the fuel that is finally formed in the combustion chamber by the supplied fuel vapors although there is no change in the air-fuel ratio. There are cases where the properties such as are different.

  Normally, in an internal combustion engine that supplies a plurality of fuels, the ignition timing is set according to the supply ratio of each fuel (the ratio of the fuel injection amount), that is, according to the octane number of the entire supplied fuel. However, if fuel vapors with different octane numbers are supplied to the combustion chamber by purging, the octane number of the air-fuel mixture formed in the combustion chamber changes from the octane number determined from the fuel supply rate. Only by setting the ignition timing, there arises a problem that it becomes impossible to obtain an optimal ignition timing for the actual mixture octane number.

  However, as described above, Patent Document 1 does not recognize any problem of property change of the fuel mixture in the combustion chamber when fuel vapors having different properties are supplied from a plurality of canisters by purge. For this reason, in the apparatus of Patent Document 1, the ignition timing may not be suitable for the actual mixture octane number, and knocking or fuel consumption may be deteriorated.

  In view of the above problems, the present invention accurately obtains the change in the properties of the air-fuel mixture in the combustion chamber due to the supplied fuel vapor when a plurality of types of fuel vapors having different properties are introduced into the engine. It is an object of the present invention to provide a control device for an internal combustion engine that can control the engine control parameter to an optimum value in accordance with the actual characteristics of the air-fuel mixture.

  According to the first aspect of the present invention, there is provided a control device for an internal combustion engine operable with a plurality of types of fuels having different properties supplied to the combustion chamber at an arbitrary supply rate, wherein the internal combustion engine is A fuel tank that stores fuel of each type, and an evaporation purge device that introduces fuel vapor generated in each fuel tank into the engine combustion chamber to prevent release to the atmosphere, and the control device includes the fuel tanks An amount of each type of fuel vapor introduced from the engine to the engine, and calculating a property of a fuel mixture formed in the combustion chamber based on the obtained amount of fuel vapor An engine control device is provided.

  That is, according to the first aspect of the present invention, the amount of fuel vapor introduced into the engine from the evaporation purge device is acquired, and the acquired amount of each type of fuel vapor, the amount of each type of fuel supplied to the engine combustion chamber, and From this, the air-fuel mixture properties finally formed in the combustion chamber are calculated.

  Thereby, even if the property of the air-fuel mixture in the combustion chamber changes due to the fuel vapor introduced from the evaporation purge device into the combustion chamber, the final property of the air-fuel mixture after the change can be obtained. It is possible to perform optimal combustion control according to the characteristics of the air-fuel mixture, such as setting an optimal ignition timing according to the octane number of the air-fuel mixture, and to obtain an optimal combustion state.

  In this specification, “acquire” such as “acquire the amount of fuel vapor” is calculated based on a case where the target is directly detected using a sensor or the like and a detection value different from the target. It means both cases where the target value is obtained indirectly.

  According to a second aspect of the present invention, the evaporation purge device is provided for each of the fuel tanks, and adsorbs the fuel vapor generated in each of the fuel tanks. A purge passage for purging the canister and supplying a purge mixture containing fuel vapor adsorbed by the canister to the engine, and the control device supplies fuel in each purge mixture supplied to the engine from each purge passage. 2. The control device for an internal combustion engine according to claim 1, wherein the control device for the internal combustion engine according to claim 1, wherein the control device for the internal combustion engine according to claim 1, which acquires a vapor concentration and calculates an amount of each type of fuel vapor introduced into the engine based on the acquired fuel vapor concentration of each fuel. .

That is, in the invention of claim 2, the evaporation purge apparatus is provided with a canister that adsorbs the fuel vapor from each fuel tank, and the fuel vapor adsorbed on the canister is supplied to the engine as a purge mixture from each canister. The
In the present invention, the fuel vapor concentration in each purge mixture supplied to the engine is acquired, and the amount of each fuel vapor supplied to the engine is calculated based on the acquired fuel vapor concentration.

  The fuel vapor concentration may be obtained by disposing an air-fuel ratio sensor in each purge passage and detecting the air-fuel ratio of the purge mixture, for example, an air-fuel ratio control air-fuel ratio disposed in the engine exhaust passage It is also possible to obtain the sensor output based on a change due to the presence or absence of purge of the sensor output.

  According to the third aspect of the present invention, a purge control valve for controlling the flow rate of the purge mixture flowing through each purge passage is further provided, and the fuel vapor concentration in the purge mixture flowing through each purge passage is not less than a predetermined value. The internal combustion engine according to claim 2, wherein when there is a fuel vapor, the fuel vapor from the purge passage having a fuel vapor concentration equal to or higher than a predetermined value is preferentially introduced into the engine over the fuel vapor from other purge passages. A control device is provided.

That is, in the invention of claim 3, in addition to the invention of claim 2, when there is a purge mixture whose fuel vapor concentration is equal to or higher than a predetermined value, the purge mixture is preferentially supplied to the engine. .
For example, when fuel vapor is adsorbed using a canister, the concentration of fuel vapor in the purge mixture increases as the amount of adsorbed fuel vapor increases. For this reason, the higher the fuel vapor concentration in the purge mixture, the higher the possibility that the canister is saturated with the adsorbed fuel vapor.

  Therefore, in the present invention, when the fuel vapor concentration in the purge mixture from a certain canister (from a certain purge passage) exceeds a predetermined value, the canister is preferentially purged, for example, The flow rate of the purge mixture from the purge passage from the canister is throttled by using a purge control valve, and the flow rate of the par mixture from the canister having a high fuel vapor concentration is relatively increased.

  As a result, the canister with the increased amount of adsorbed fuel vapor is purged preferentially, so that the canister is prevented from being saturated with the fuel vapor.

  According to the invention described in each claim, when a plurality of types of fuel vapor having different properties are introduced into the engine, it is possible to accurately acquire the change in the property of the air-fuel mixture in the combustion chamber due to the supplied fuel vapor. Thus, the engine control parameters such as the ignition timing can be controlled to an optimum value according to the actual characteristics of the air-fuel mixture, and a common effect can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an embodiment when the present invention is applied to an internal combustion engine for an automobile.

  In FIG. 1, reference numeral 100 denotes an internal combustion engine for a vehicle, and a four-cylinder gasoline engine is used in this embodiment. 1, 110H and 110L show fuel injection valves provided in each cylinder of the internal combustion engine 1, respectively. In the present embodiment, the fuel injection valve 110H is a port injection valve that injects fuel into the intake port of each cylinder, and the fuel injection valve 110L is an in-cylinder injection valve that directly injects fuel into each cylinder.

  As will be described later, the internal combustion engine 100 of the present embodiment is a multi-fuel supply internal combustion engine that injects fuels having different octane numbers from the fuel injection valves 110H and 110L at a supply rate according to engine operating conditions. Specifically, in this embodiment, high-octane gasoline is injected into the intake port from the fuel injection valve 110H, and low-octane gasoline is directly injected into the cylinder from the fuel injection valve 110L, and from the fuel injection valves 110H and 110L. Control is performed to change the ratio (supply ratio) of the fuel injection amount in accordance with engine operating conditions (for example, engine load).

  The high-octane gasoline injection valve 110H and the low-octane gasoline injection valve 110L are connected to the high-octane gasoline delivery pipe 20H and the low-octane gasoline delivery pipe 20L, respectively. Inject each.

  In the embodiment of FIG. 1, high-octane gasoline is injected from the port injector 110H and low-octane gasoline is injected individually from the in-cylinder injector 110L to each cylinder, but both the fuel injectors 110H and 110L are used. Both can be port injection valves or in-cylinder injection valves. Further, when both of these are port injection valves or in-cylinder injection valves, the delivery pipes 20H and 20L are simply provided without separately providing the high-octane gasoline injection valve 110H and the low-octane gasoline injection valve 110L. It may be connected to one in-cylinder fuel injection valve, and high octane number gasoline and low octane number fuel may be mixed at a predetermined ratio before the fuel injection valve is supplied or within the fuel injection valve after the fuel injection valve is supplied. .

  In FIG. 1, the fuel tanks of the engine 100 are indicated by 11H and 11L. In this embodiment, in order to inject two fuel oils having different octane numbers into the engine from the fuel injection valves 110H and 110L, each fuel tank is provided separately.

  In FIG. 1, high octane gasoline is stored in the fuel tank 11H, and low octane gasoline is stored in 11L. In the present embodiment, high-octane gasoline and low-octane gasoline are replenished separately to the tanks 11H and 11L from the outside. For example, commercially available normal gasoline has a high content of components having a high octane number. A fuel separator that separates high-octane gasoline into low-octane gasoline with a low content of high-octane components is disposed on the vehicle, and high-octane gasoline and low-octane gasoline produced by the fuel separator are tanks 11H and 11L. You may make it store in.

  The fuel stored in the fuel tanks 11H and 11L is boosted by the fuel injection pumps 21H and 21L having a discharge capacity control mechanism and supplied to the fuel injection valves 110H and 110L. It is injected into the cylinder.

  That is, in this embodiment, high-octane gasoline and low-octane gasoline are supplied to each cylinder of the engine 100 through mutually independent supply paths, and the fuel injection amount of each fuel injection valve is individually controlled. The supply ratio of high-octane gasoline and low-octane gasoline supplied to the engine can be arbitrarily set.

In FIG. 1, reference numerals 250H and 250L denote canisters that adsorb the evaporated fuel in the respective fuel tanks 11H and 11L.
The canisters 250H and 250L are each provided with an adsorbent such as activated carbon, and are connected to the upper liquid level space in the fuel tanks 11H and 11L by vapor passages 252H and 252L, respectively. As a result, the fuel vapor of the high-octane gasoline generated in the fuel tank 11H is guided to the canister 250H, and the fuel vapor of the low-octane gasoline generated in the fuel tank 11L is guided to the canister 250L via the vapor passages 252H and 252L, respectively. Since it is adsorbed and held by the adsorbent in the canisters 250H and 250L, it is prevented from being released from the fuel tanks 11H and 11L to the atmosphere.

  The canisters 250H and 250L are connected to the downstream side of a throttle valve (not shown) of the intake passage 3 by purge passages 251H and 251L, respectively, and purge control valves 253H and 253L are provided on the purge passages 251H and 251L, respectively. ing.

The purge control valves 253H and 253L include, for example, solenoid actuators, and open and close in response to drive pulse signals from the ECU 30 described later.
That is, the purge control valves 253H and 253L repeat the operation of opening the valve signal while the pulse signal is on and closing the valve signal when the pulse signal is off during one cycle of the drive pulse signal. Therefore, the purge gas flow rate passing through the purge control valve increases in accordance with the ratio (duty ratio) of the time during which the pulse signal is on in one cycle of the drive pulse signal.

  When a drive pulse signal is supplied to the purge control valves 253H and 253L during engine operation, the evaporated fuel adsorbed by the adsorbent in the canisters 250H and 250L flows into the canister from the air introduction passages 255H and 255L of the canisters. The purge air is released from the adsorbent and becomes a purge mixture, which flows into the intake passage 3 after passing through the purge control valves 253H and 253L. This prevents the adsorbent in the canister from being saturated with the adsorbed fuel vapor.

The purge air-fuel mixture flowing into the intake passage 3 from the canisters 250H and 250L through the purge control valves 253H and 253L is mixed with the intake air of the engine in the intake passage 3 to become a uniform air-fuel mixture in each cylinder of the engine. Inhaled and burned in the cylinder.
The flow rate of the purge mixture supplied to the engine from the canisters 250H and 250L can be arbitrarily adjusted from 0 to 100 percent by controlling the duty ratio of the purge control valves 253H and 253L.

  An electronic control unit (ECU) of the engine 100 is indicated by 30 in FIG. In the present embodiment, the ECU 30 is configured as a microcomputer having a known configuration in which a read only memory (ROM), a random access memory (RAM), an arithmetic unit (CPU), and an input / output port are connected by a bidirectional bus. In addition to performing basic control such as engine air-fuel ratio control, ignition timing of each cylinder, and control of fuel injection amount, in this embodiment, as will be described later, it flows into the engine as a purge mixture from canisters 250H and 250L. An operation of calculating the octane number of the air-fuel mixture formed in the engine combustion chamber is performed according to the amount of fuel vapor to be performed.

  For these controls, the output port of the ECU 30 is connected to the fuel injection valves 110H and 110L of each cylinder via a drive circuit (not shown) and controls the fuel injection amount of each fuel injection valve. It is connected to an ignition plug (not shown) of each cylinder through a circuit to control the ignition timing of the engine. In addition, at the input port of the ECU 30, the rotational speed of the engine 1 from the rotational speed sensor 33, the intake pressure of the engine from the intake pressure sensor 35 provided in the engine intake passage 3, and an empty space disposed in the engine exhaust passage 5 are provided. The air-fuel ratio of the engine exhaust is input from the fuel ratio sensor 31.

In the present embodiment, the ECU 30 calculates the engine intake air amount based on the intake pressure detected by the intake pressure sensor 35 and the engine rotational speed obtained by the rotational speed sensor 33, and engine combustion is performed with respect to this intake air amount. A fuel injection amount G ₀ (weight) required for setting the air-fuel ratio to the target air-fuel ratio (for example, the theoretical air-fuel ratio) is calculated.

The actual fuel injection amounts of the fuel injection valves 110H and 110L are controlled as fuel volumes QH and QL (ml) injected at a time, respectively, and are given by the following equations, respectively.
QH = G ₀ × KH × R × FAF × (1 + FGH)
QL = G ₀ × KL × (1−R) × FAF × (1 + FGL)

Here, KH and KL are coefficients for converting the fuel weight (G ₀ ) to the fuel volume (QH, QL), and are calculated in advance using the specific specific gravity of each of the high-octane gasoline and the low-octane gasoline. A constant value is used.
Further, FAF is an air-fuel ratio correction coefficient based on the above-described air-fuel ratio sensor 31, and FGH and FGL are learning correction coefficients described later.

  Further, R is the injection amount ratio of the fuel injection valve 110H that is closed to the entire fuel injection amount, that is, the supply ratio of high-octane gasoline, and is set by the ECU 30 based on a predetermined relationship according to the engine operating state (engine load). Is done.

  For example, when the engine is operated at a high load, the ECU 30 increases the supply ratio of the high-octane gasoline as compared with the case where the load is low. As a result, the octane number of the fuel supplied to the engine as a whole increases, so that it is possible to increase the engine output by performing an operation in which the ignition timing is sufficiently advanced to near the maximum output ignition timing.

  Further, when the engine temperature is low, the ECU 30 increases the supply ratio of the low octane gasoline to the engine. Since low-octane gasoline generally has good ignitability, this makes it possible to perform stable operation while maintaining good exhaust properties and good combustion even at low engine temperatures.

Next, the learning correction coefficient in the air-fuel ratio control will be described. As will be described later, in this embodiment, since the fuel vapor having different octane numbers is supplied from the canisters 250H and 250L to the engine combustion chamber, the octane number of the air-fuel mixture actually formed in the combustion chamber is the aforementioned supply ratio. It is different from the octane number determined from R.
In this embodiment, the amount of fuel vapor supplied from the canisters 250H and 250L is calculated using the learning correction coefficient, and the final octane number of the air-fuel mixture is calculated using the amount of fuel vapor and the supply ratio R. is doing.

In order to simplify the explanation, first, the learning correction coefficient will be described by taking the case where the engine is operated with a single fuel as an example. The fuel injection amount Q (ml) of the engine is Q = G ₀ × K × FAF. X (1 + FG).

Here, as described above, G ₀ is a fuel amount (reference fuel amount) necessary for setting the combustion air-fuel ratio to the target air-fuel ratio with respect to the engine intake air amount, and the engine intake air amount, the target air-fuel ratio, Is calculated from K is a conversion constant from weight (G ₀ ) to volume (Q), FAF is an air-fuel ratio correction coefficient, and FG is a learning correction coefficient.

FAF is a feedback correction coefficient for accurately matching the air-fuel ratio to the target air-fuel ratio even when the correspondence between G ₀ and the intake air amount is temporarily shifted due to fluctuations in operating conditions, etc. It is set at each fuel injection so that the exhaust air-fuel ratio measured by the sensor becomes the target air-fuel ratio.

  Further, the learning correction coefficient is for correcting a deviation due to, for example, variation in injection characteristics of the fuel injection valve. As described above, in the air-fuel ratio control, the fuel injection amount is corrected based on the output of the air-fuel ratio sensor 31 so that the exhaust air-fuel ratio (combustion air-fuel ratio) becomes the target air-fuel ratio. Even if there is a variation in the injection characteristics, the FAF value will change accordingly, so the influence of the variation should not occur.

  However, the value of FAF originally has a center of fluctuation of 1.0 unless there is an error such as variations in sensor and fuel injection valve characteristics. For the purpose of preventing control divergence, the FAF value has a predetermined upper limit value and lower limit value centered on 1.0. For this reason, if there is a variation in the injection characteristics of the fuel injection valve, the FAF value changes around a value (or a smaller value) greater than 1.0, and the change range up to the upper limit value of the FAF. There is a problem that the control range is restricted because the (or change range up to the lower limit) becomes narrow.

  Therefore, in normal air-fuel ratio control, for example, a constant change such as a variation in the injection characteristic of the fuel injection valve is corrected using a learning correction coefficient, and FAF is always the center of the upper limit value and the lower limit value ( 1.0) Temporary changes in the air-fuel ratio due to changes in operating conditions are corrected so as to fluctuate in the vicinity.

  That is, the value of the learning correction coefficient FG is set to a value at which the center value of the fluctuation of the air-fuel ratio correction coefficient FAF is equal to 1.0. For example, when the FAF value fluctuates around 1.005, the FG value is set to 0.005 (1 + FG = 1.005). By setting the learning correction coefficient FG in this way, the FAF value always varies around 1.0.

  The ECU 30 calculates a time average value of the air-fuel ratio correction coefficient FAF by a separately performed learning correction coefficient calculation operation, and sets and stores a value that makes this average value 1.0 as a learning correction coefficient FG. As a result, even when the air-fuel ratio is temporarily shifted due to a change in the operating state, the air-fuel ratio can be corrected to match the target value with good response.

Since the value of this learning correction coefficient FG also changes depending on operating conditions such as engine load, the normal engine operating load area is divided into several areas, and the value of the learning correction coefficient FG is set for each area. ing.
Further, when a plurality of fuels are injected from individual fuel injection valves as in this embodiment, a learning correction coefficient is set for each fuel injection valve.
For this reason, in this embodiment, the learning correction coefficient is individually set for both the high-octane gasoline injection valve 110H and the low-octane gasoline injection valve 110L.

  The learning correction coefficient FG compensates for a constant change such as a variation in the injection characteristics of the fuel injection valve or a shift due to wear, etc., and becomes 0 if the injection characteristics match the standard state. Further, as the deviation from the standard state increases, the absolute value of FG increases, and the deviation between the value of (1 + FG) and 1 increases.

  As described above, when purging from the canister is performed, in this embodiment, fuel vapor of high-octane gasoline is supplied from the canister 250H and fuel vapor of low-octane gasoline is supplied from the canister 250L to the engine combustion chamber. Therefore, even when high-octane gasoline and low-octane gasoline are injected from the fuel injection valves 110H and 110L at a predetermined supply ratio, the octane number of the air-fuel mixture actually formed in the combustion chamber is lower than that of high-octane gasoline. This is different from the value calculated from the supply ratio (fuel injection ratio) with octane gasoline.

  Also in this case, when the learning correction is performed, the engine air-fuel ratio is accurately maintained at the target air-fuel ratio. However, since the optimal ignition timing changes according to the octane number of the mixture, if the octane number of the mixture in the combustion chamber changes due to the purge mixture from the canister, the optimal ignition timing is also suitable for the octane number calculated from the above supply ratio. If the engine is operating at the ignition timing determined from the supply rate, the engine will be knocked, or the ignition timing will be sufficiently advanced even though the ignition timing can be advanced to increase the output sufficiently. Since the vehicle is driven without making a corner, the engine performance and fuel consumption may deteriorate.

  In this embodiment, the fuel vapor amounts of the high-octane gasoline and the low-octane gasoline in the purge mixture flowing in from the canister are obtained, and the mixture gas formed in the combustion chamber is determined from this fuel vapor amount and the supply ratio of each fuel. The above problem is solved by calculating the actual octane number and setting the optimal ignition timing based on the actual octane number.

  The amount of fuel vapor in the purge mixture from the canister is determined by providing an air-fuel ratio sensor in each purge passage or engine intake passage, and detecting the purge mixture or intake air-fuel ratio at the time of purge execution to detect the fuel vapor from each canister Although the concentration may be obtained directly, in this embodiment, the fuel vapor concentration from each canister is calculated based on the change in the value of the learning correction coefficient of the air-fuel ratio control depending on whether or not purge is executed.

As described above, the value of the learning correction coefficient FG changes according to variations or deviations in the injection characteristics of the fuel injection valve, but fuel other than the fuel injected from the fuel injection valve, for example, purge mixture from each canister It also changes when the fuel vapor inside is supplied to the engine combustion chamber.
For example, it is assumed that the value of the learning correction coefficient has converged to FG ₀ before the purge is started. It is assumed that when purging is started in this state, the value of the learning correction coefficient changes and converges to (FG ₀ −α).

As described above, the fuel injection amount Q of the engine is represented by Q = G ₀ × K × FAF × (1 + FG). Therefore, in this case, the fuel injection amount Q ₀ before starting the purge is Q ₀ = G ₀ × K × FAF × (1 + FG ₀ ), and the fuel injection amount Qpg after the purge is executed is Qpg = G ₀ × K × FAF. X (1+ (FG-α)).

That is, after the purge is started, the fuel injection amount is reduced by (Q ₀ −Qpg) = G ₀ × K × FAF × α. Here, the engine air-fuel ratio is maintained the same by the air-fuel ratio feedback control before and after the start of the purge, and the total amount of fuel supplied to the engine combustion chamber is the same. For this reason, the decrease in the fuel injection amount after the start of the purge is equal to the amount of fuel vapor supplied to the engine combustion chamber as a purge mixture.

Therefore, the amount of fuel supplied from the canister to the engine as a purge mixture is (Q ₀ −Qpg) G ₀ × K × FAF × α. Here, when the amount of fuel is expressed by weight, the conversion factor K is not necessary (K = 1.0), and the average value of FAF is 1.0. The amount (weight) of inflowing fuel vapor is obtained as G ₀ × α.

  The purge mixture flow rate is given as a function of the purge control valve opening (duty ratio) and the engine intake pressure. Therefore, the amount of fuel vapor obtained from the amount of change in the learning correction coefficient during purge execution as described above, and the purge mixture flow rate obtained from the purge control valve opening and the engine intake pressure are used. The fuel vapor concentration can be calculated.

In this embodiment, the value of the purge mixture flow rate is stored in advance in the ROM of the ECU 30 in the form of a two-dimensional numerical table using the purge control valve opening and the engine intake pressure as parameters.
The ECU 30 obtains a learning correction coefficient FG (reference learning correction coefficient) when the canisters 250H and 250L are not purged, and then purges the canisters 250H and 250L individually to obtain the learning correction coefficient. Find the change in value from the reference learning correction factor.

  That is, for example, the ECU 30 first holds the purge control valve 253H of the high-octane gasoline canister 250H at a predetermined opening (duty ratio) (for example, fully open), and obtains the change ΔH of the learning correction coefficient coefficient at this time. Then, the purge control valve 253H of the canister 250H is fully closed, and the purge control valve 253L of the low-octane gasoline canister 250L is held at a predetermined opening (for example, the previous time), and the learning correction coefficient FG at this time Is obtained.

Then, the ECU 30 calculates the fuel vapor concentrations VPH and VPL from the canisters 250H and 250L from the learning correction coefficient change amounts ΔH and ΔL and the flow rate of the purge mixture.
It has been found that the fuel vapor concentration of the purge mixture from the canister depends on the fuel vapor adsorption amount of the canister, and does not change much even if the flow rate of the purge mixture changes.

  Therefore, as will be described later, the ECU 30 uses the fuel vapor concentration in the purge mixture calculated as described above to calculate a change in the octane number of the combustion chamber mixture due to the fuel vapor in the purge mixture during the purge operation under different operating conditions. .

  Further, during normal purge operation, each canister is purged at the same time. When the fuel vapor concentration in the purge mixture from each canister calculated as described above is equal to or higher than a predetermined value, the ECU 30 determines the fuel vapor concentration. A canister with a value equal to or greater than a predetermined value is purged preferentially. That is, when the fuel vapor concentration is equal to or higher than a predetermined value, the amount of fuel vapor adsorbed by the canister increases. For this reason, the ECU 30 sets the purge control valve opening of this canister to be larger than the purge control valve opening of the other canister so that the purge mixture flow rate from this canister is larger than the purge mixture flow rate from the other canisters. Set to. As a result, fuel vapor desorption from the canister having a large amount of adsorbed fuel vapor is promoted, and the canister is prevented from being saturated with fuel vapor.

2 to 4 are flowcharts for specifically explaining the above operation.
FIG. 2 is a flowchart for explaining the fuel vapor concentration acquisition operation of the purge mixture from each canister, which is executed by the ECU 30.

  In the operation of FIG. 2, first, at step 201, it is determined whether or not the acquisition of the reference learning correction coefficient has been completed. The reference learning correction coefficient is a learning correction coefficient when the canister is not purged, and corresponds to a steady deviation such as a deviation in the fuel injection characteristics of the fuel injection valves 110H and 110L. .

  In this embodiment, since the high-octane gasoline fuel injection valve 110H and the low-octane gasoline fuel injection valve 110L are used, the reference learning correction coefficient is also used for the fuel injection valve 110H value FGHI and the fuel injection valve 110L. Two values, FGLI, are determined separately. The reference learning correction coefficients FGHI and FGLI indicate that the purge is not executed in the operation region (the region where the engine is operated with only the high-octane gasoline or the low-octane gasoline only) in which the fuel injection is performed by each fuel injection valve alone. Obtained at.

If the reference learning correction coefficient is not acquired in step 201, the operation of FIG. 2 is terminated, and the fuel vapor concentration acquisition operation is not executed until the reference learning correction coefficient is acquired.
If the acquisition of the reference learning correction coefficient has been completed in step 201, it is next determined in step 203 whether the purge execution permission condition is satisfied.

The purge execution permission condition in the present embodiment is, for example, that the warm-up of the engine has been completed (the engine coolant temperature is equal to or higher than a predetermined value) and the air based on the current air-fuel ratio sensor 31 output. The fuel ratio feedback control is being executed.
If the purge execution permission condition in step 203 is not satisfied, the operation of FIG. 2 is terminated, and the fuel vapor concentration acquisition operation is not executed.

  If the purge execution permission condition of step 203 is satisfied, the routine proceeds to step 205, where it is determined whether the value of the flag XFGH is set to 1. XFGH is a flag indicating whether or not the acquisition of the fuel vapor concentration from the high-octane gasoline canister 250H is completed. The flag is set to 0 when the engine is started, and is set to 1 after the completion of acquisition of the fuel vapor concentration (step 213). Set.

If the fuel vapor concentration acquisition from the high octane gasoline canister 250H is not completed in step 205 (XFGH = 0), the high octane gasoline vapor concentration acquisition operation of step 207 is executed.
That is, in step 207, the purge control valve 253H of the high-octane gasoline canister 250H is held at a predetermined opening (full open in this embodiment) with the purge control valve 253L of the low-octane gasoline canister 250L fully closed. After waiting for the change of both values of the learning correction coefficients FGHI and FGLI to end, the amounts of change (−ΔHH) and (−ΔLH) due to the purge of FHGI and FGLI are obtained.

From these changes, the fuel amount (weight) ΔGH supplied to the combustion chamber as fuel vapor is expressed as ΔGH = (G ₀ × R × ΔHH) + (G ₀ × (1−R) × ΔLH). calculate.

The fuel vapor concentration (high octane gasoline vapor concentration) VPH in the purge mixture from the high octane gasoline canister 250H is calculated as VPH = ΔGH / GPG.
Here, GPG is the purge gas mixture flow rate in step 207, which is given as a function of the engine intake pressure and the purge control valve opening during the fuel vapor acquisition operation.

  After completing the calculation of the fuel vapor concentration VPH in step 207, it is determined in step 209 whether or not the fuel vapor concentration exceeds a predetermined upper limit value VPHmax. After the value of the concentration flag FGHA is set to 1, or if it is equal to or less than VPHmax, the value of the flag FGHA is set to zero in step 213, and then the value of the high octane number gasoline vapor concentration acquisition completion flag XFGH is set to 1, respectively. Set and go to step 217.

  In steps 217 to 227, operations similar to those in steps 205 to 235 are performed on the low-octane gasoline canister 250L, and the low-octane gasoline vapor concentration VPL is calculated.

  When the acquisition of both the high octane gasoline vapor concentration VPH and the low octane gasoline vapor concentration VPL is completed, the value of the fuel vapor concentration acquisition completion flag XFGHL is set to 1 in step 229. Note that the values of the flags XFGHL and XFGL are reset to zero when the engine is started, similarly to the flag XFGH.

  2, the high octane gasoline vapor concentration VPH from the canister 250H and the low octane gasoline vapor concentration VPL from the canister 250L at the time of purging are calculated.

  As described above, the fuel vapor concentrations VPH and VPL are not calculated indirectly from the change in the learning correction coefficient as described above, but are supplied to the purge passages 251H and 251L or the intake passage 3 downstream of the purge passage connection portion. It is also possible to detect directly using the arranged intake air-fuel ratio sensor.

Next, referring to FIG. 3, the final property (in this embodiment, octane number) of the air-fuel mixture in the combustion chamber using the fuel vapor concentration calculated in the operation of FIG. 2, and the ignition timing correction operation based on the calculation result Will be described in detail.
The operation shown in FIG. 3 is performed by the ECU 30 at a predetermined ignition timing setting timing.

  In the operation of FIG. 3, first, in step 301, it is determined whether or not the fuel vapor concentration acquisition of each canister is completed based on the value of the fuel vapor concentration acquisition completion flag XFGHL, and the acquisition is not completed (XFGHL = At 0), the final octane number calculation and the ignition timing correction at step 303 and after are not performed, and the operation ends.

In this case, the octane number and the ignition timing of the air-fuel mixture are set based on the reference supply ratio R by an ignition timing setting operation separately executed by the ECU 30.
If the fuel vapor concentration acquisition has been completed in step 301 (XFGHL = 1), then in step 303, the current fuel supply ratio R to the engine is read.

  In the present embodiment, the fuel supply ratio R is defined as the ratio of the injection amount of high octane gasoline (fuel injection valve 110H) to the total amount of fuel injection from the fuel injection valves 110H and 110L. The fuel supply ratio R is basically a reference determined by a fuel supply ratio setting operation separately executed by the ECU 30 based on a predetermined relationship from the engine load ratio, the rotational speed, and the intake pressure (intake air amount). The supply ratio is used, but if necessary, the reference fuel ratio is changed by taking into account the remaining amount of fuel in the fuel tanks 11H and 11L (consumption balance of both fuels), occurrence of knocking, etc. It may be used.

In steps 305 and 307, the amounts of high-octane gasoline vapor and low-octane gasoline vapor in the purge mixture flowing into the combustion chamber are calculated.
That is, in step 305, the current purge mixture flow rate GPGH of the canister 250H is calculated from the opening degree (duty ratio) of the purge control valve 253H of the high octane gasoline canister 250H and the intake pressure of the engine. From the high-octane gasoline vapor concentration VPH in the purge mixture obtained in the operation 2, the high-octane gasoline vapor amount GVPH flowing into the combustion chamber is calculated.

  In step 307, the low octane gasoline vapor amount GVPL flowing into the combustion chamber is calculated in the same manner as in step 305.

In step 309, a high octane gasoline injection amount and a low octane gasoline injection amount are obtained from the fuel injection amounts of the current fuel injection valves 110H and 110L, respectively, and a high octane gasoline vapor amount GVPH supplied by purging to these is obtained. Low octane number gasoline vapor amount GVPL is added, and octane number RON after mixing these is calculated.
That is, the octane number RON calculated in step 309 is the octane number of the air-fuel mixture finally formed in the combustion chamber.

  In step 311, the optimal ignition timing IG is set based on a predetermined relationship using the final octane number RON calculated above and the engine speed and load.

  As a result, even when the octane number of the air-fuel mixture in the combustion chamber changes due to the canister purge, the optimal ignition timing is set for the changed octane number, and knocking and fuel consumption are prevented from deteriorating.

  Next, FIG. 4 is a flowchart specifically explaining the purge operation of the canisters 250H and 250L. In this operation, the purge control valve opening of each canister at the time of purge execution is determined.

In the operation of FIG. 4, it is first determined in step 401 whether or not the purge execution permission condition is satisfied. The purge execution permission condition in step 401 is the same as the purge execution permission condition in step 203 in FIG.
If the purge execution permission condition is not satisfied in step 401, the operation is immediately terminated. If the purge execution permission condition is satisfied, step 403 and subsequent steps are executed.

  That is, in step 403, it is first determined whether or not a high octane gasoline vapor high concentration flag FGHA is set to 1. FGHA is a flag that is set to 1 when the fuel vapor concentration in the purge mixture of the high-octane gasoline canister 250H exceeds the predetermined value in the operation of FIG. 2, and FGHA is set to 1. Means that the fuel vapor adsorption amount of the high octane gasoline canister 250H is increased.

Therefore, in this case, the process proceeds to step 405, and the purge control valve 253H opening (duty ratio) DRH of the canister 250H is set to a value larger than the opening (duty ratio) DRL of the purge control valve 253L of the canister 250L.
As a result, the purge air amount of the canister 250H becomes larger than the purge air amount of the canister 250L, and the canister 250H is purged preferentially over the canister 250L, thereby preventing the canister 250H from being saturated with the adsorbed fuel vapor. Is done.

  If the flag FGHA is not set to 1 in step 403, it is next determined in step 407 whether the value of the low octane gasoline vapor high concentration flag FGLA is set to 1 and set to 1. If so, in step 409, the opening (duty ratio) DRL of the purge control valve 253L is set to a value larger than the opening (duty ratio) DRH of the purge control valve 253H, and the low-octane gasoline canister 250L has priority. Purge to prevent the canister 250L from being saturated with adsorbed fuel vapor.

  If FGLA = 1 is not satisfied in step 407, the amount of adsorbed fuel vapor has not increased in both the canisters 250H and 250L. Therefore, the process proceeds to step 411 and the opening degrees DRH and DRL of the purge control valves 253H and 253L are set to normal values ( DRH = DRL) to finish the operation. As a result, the canisters 250H and 250L are purged almost evenly.

  In the above embodiment, the case where two canisters, namely, a high-octane gasoline canister 250H and a low-octane gasoline canister 250L are installed as an example. However, when the number of canisters (types of fuel) is three or more, However, it goes without saying that the actual octane number of the air-fuel mixture in the combustion chamber can be obtained by the same operation as in the above embodiment, and the ignition timing can be adjusted accordingly.

It is a figure explaining schematic structure of an embodiment at the time of applying the present invention to an internal-combustion engine for vehicles. It is a flowchart explaining fuel vapor concentration acquisition operation. It is a flowchart explaining ignition timing correction operation. It is a flowchart explaining purge operation of a canister.

Explanation of symbols

3 Intake passage 11H, 11L Fuel tank 30 Electronic control unit (ECU)
31 Air-fuel ratio sensor 35 Intake pressure sensor 110H, 110L Fuel injection valve 250H, 250L Canister 251H, 251L Purge passage 253H, 253L Purge control valve

Claims (3)

A control device for an internal combustion engine operable with a plurality of types of fuels having different properties to be supplied to the combustion chamber at an arbitrary supply rate,
The internal combustion engine includes a fuel tank that stores the fuel of each type, and an evaporation purge device that introduces fuel vapor generated in each fuel tank into the engine combustion chamber to prevent the emission to the atmosphere.
The control device acquires the amount of each type of fuel vapor introduced from each fuel tank into the engine, and determines the characteristics of the fuel mixture formed in the combustion chamber based on the acquired fuel vapor amount. A control apparatus for an internal combustion engine, characterized in that the calculation is performed. The evaporation purge device is provided for each of the fuel tanks, and canisters that adsorb fuel vapor generated in the fuel tanks;
A purge passage for purging each of the canisters during operation of the engine, and supplying a purge mixture containing fuel vapor adsorbed to the canister to the engine;
The control device acquires the fuel vapor concentration in each purge gas mixture supplied to the engine from each purge passage, and the respective types of fuel introduced into the engine based on the acquired fuel vapor concentration of each fuel The control device for an internal combustion engine according to claim 1, wherein the amount of steam is calculated.   Furthermore, a purge control valve for controlling the flow rate of the purge mixture flowing through each purge passage is provided, and when there is a fuel vapor concentration exceeding a predetermined value in the purge mixture flowing through each purge passage, the fuel vapor concentration 3. The control device for an internal combustion engine according to claim 2, wherein the fuel vapor from the purge passage where the gas becomes equal to or greater than a predetermined value is introduced into the engine preferentially over the fuel vapor from the other purge passages.

Images