JP5056770B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention can adjust at least one of the opening timing of the intake valve of the internal combustion engine and the closing timing of the exhaust valve of the engine (hereinafter also referred to as “variable valve timing control device”). The present invention relates to a control device for an internal combustion engine including

  Conventionally, an internal combustion engine that can use a fuel in which alcohol such as ethanol is mixed (hereinafter also referred to as “alcohol mixed fuel”) has been proposed. Here, the alcohol-mixed fuel mixed with alcohol (so-called bioethanol, etc.) produced from biological resources reduces the amount of greenhouse gas emissions such as carbon dioxide compared to fuels consisting only of fossil fuels such as gasoline. It is believed that there is an advantage that it can be reduced. On the other hand, the alcohol contained in the alcohol-mixed fuel has a feature that it is difficult to be atomized particularly in a low temperature environment as compared with gasoline and the like.

  Therefore, for example, at the time of cold start of the engine, alcohol contained in the alcohol mixed fuel injected (supplied) into the intake passage of the engine is not sufficiently atomized. As a result, the amount of fuel contained in the air-fuel mixture introduced into the combustion chamber of the internal combustion engine becomes smaller in accordance with the “amount of alcohol not atomized” than the amount of fuel actually injected. In other words, the air-fuel ratio of the air-fuel mixture provided for combustion becomes a substantially leaner air-fuel ratio than the air-fuel ratio calculated from the amount of fuel actually injected. If the amount of fuel contained in the air-fuel mixture supplied for combustion becomes excessively small, the air-fuel mixture may not burn even if the air-fuel mixture is ignited. For this reason, an engine using an alcohol-mixed fuel may take time to cold start (cold startability is not good).

  Therefore, one conventional internal combustion engine uses a variable valve timing control device to promote atomization of the alcohol-mixed fuel during cold start. Specifically, in the conventional internal combustion engine, the intake top dead center (exhaust top dead center) is adjusted by adjusting the “opening timing of the intake valve and / or the closing timing of the exhaust valve” by the variable valve timing control device. In the vicinity, the gas in the combustion chamber is blown out toward the intake passage. Further, the conventional internal combustion engine collides with the blown gas “alcohol mixed fuel injected into the intake passage by the fuel injection device” to promote atomization of the fuel (for example, Patent Documents). 1). In this specification and the appended claims, fuel evaporation, atomization, vaporization, atomization, and the like are collectively referred to as “atomization”.

JP 2004-251157 A

  However, the inventor has found that even in the above engine, the alcohol-mixed fuel cannot be atomized properly, and the starting performance and the like of the engine may not be improved. This point will be described below.

  As an example of the “variable valve timing control device” used in the above-described conventional engine, a “hydraulic variable valve timing control device” that drives hydraulically a member that adjusts the opening / closing timing of the intake valve and the exhaust valve can be cited. (For example, refer to Japanese Patent Application Laid-Open No. 2007-303423.) The hydraulic variable valve timing control device includes an intake camshaft that opens and closes an intake valve, an intake timing changing mechanism provided at an end of the intake camshaft, an exhaust camshaft that opens and closes an exhaust valve, and an exhaust An exhaust timing changing mechanism provided at the end of the camshaft is provided.

  The intake timing changing mechanism is a mechanism that can advance and retard the phase of the intake camshaft by a desired angle by supplying and discharging hydraulic oil. Along with the advance and retard of the phase of the intake camshaft, the opening and closing timing of the intake valve is advanced and retarded by the same angle. This hydraulic oil is supplied to and discharged from the intake timing changing mechanism by a hydraulic pump and a hydraulic oil supply control valve provided outside the intake timing changing mechanism. The exhaust timing changing mechanism has the same structure as the intake timing changing mechanism described above, and the opening / closing timing of the exhaust valve can be advanced and retarded by a desired angle. That is, the above-described “hydraulic variable valve timing control device” adjusts the opening and closing timings of the intake valve and the exhaust valve by supplying and discharging hydraulic oil to and from the intake timing changing mechanism and the exhaust timing changing mechanism.

  The conventional engine first determines target timings corresponding to the opening / closing timings of the intake valve and the exhaust valve based on the operating state of the engine. Next, the conventional engine supplies / discharges hydraulic oil to / from the intake timing change mechanism and the exhaust timing change mechanism so that the actual opening / closing timings of the intake valve and the exhaust valve coincide with the corresponding target timings.

  However, from the time “the supply and discharge of hydraulic oil to the intake timing change mechanism and the exhaust timing change mechanism begins to be executed”, “the intake camshaft and the exhaust camshaft are at predetermined positions (rotational positions corresponding to the target timing). It takes time according to the viscosity of the hydraulic oil, the output of the hydraulic pump, the frictional resistance between the members, and the like until the point of reaching “. That is, it takes time for the actual opening / closing timings of the intake valve and the exhaust valve to reach the corresponding target timings.

  On the other hand, as another example of the “variable valve timing control device” used in the above-described conventional engine, an “electric variable valve timing control device” that drives a member for adjusting the opening / closing timing of the intake valve and the exhaust valve by an electric motor. (For example, refer to Japanese Patent Application Laid-Open No. 2004-150397). This electric variable valve timing control device is different from the hydraulic variable valve timing control device described above in that the phase of the intake camshaft and the exhaust camshaft is advanced and retarded using an electric motor and a plurality of gears. Yes. However, even if this “electric variable valve timing control device” is used, the actual moment of inertia of the gear, the output of the motor, and the It takes time according to the frictional resistance between the members. Hereinafter, “the engine until the actual opening timing of the intake valve reaches its target opening timing” and “the period until the actual closing timing of the exhaust valve reaches its target closing timing” are referred to as “response”. Collectively referred to as “delay period”.

  By the way, as described above, the conventional engine uses the variable valve timing control device to adjust the valve opening timing of the intake valve and / or the valve closing timing of the exhaust valve, so that the alcohol-mixed fuel at the time of cold start It is designed to promote atomization. However, in the above-mentioned “response delay period”, the opening and closing timings of the intake valve and the exhaust valve are not sufficiently adjusted, so that the alcohol-mixed fuel is not atomized to the expected level (that is, as described above, The amount of fuel contained in the air-fuel mixture becomes smaller.) Therefore, during the response delay period, the air-fuel mixture may not burn even if the air-fuel mixture is ignited. In other words, the start of the engine is delayed until the response delay period substantially elapses, and the time required to start the engine (particularly, cold start) may increase.

  Further, as described above, the air-fuel mixture that has not been combusted during the response delay period (unburned air-fuel mixture) is discharged into the exhaust passage of the engine in the exhaust stroke. For this reason, the unburned mixture continues to be discharged into the exhaust passage until the engine is started (that is, combustion starts). As a result, there is a problem that fuel that does not contribute to the operation of the engine (hereinafter also referred to as “invalid fuel”) is consumed until the engine is started. This amount of invalid fuel increases as the time required to start the engine increases.

  The present invention has been made to address the above problems. That is, the object of the present invention is to start the engine at an early stage even when using a fuel containing a fuel component (for example, alcohol) that is difficult to atomize in a low temperature environment, and as a result, invalid An object of the present invention is to provide a control device for an internal combustion engine that can reduce fuel consumption.

  An internal combustion engine control apparatus according to the present invention for achieving the above target is applied to an engine having a fuel injection means for injecting fuel into an intake passage, and includes a fuel injection amount determination means, a valve timing control means, a fine particle And an index value acquisition means and a valve timing determination means.

The fuel injection amount determining means includes
A “basic fuel amount”, which is “a basic amount of fuel injected from the fuel injection means”, is determined based on “a first operating parameter representing an operating state of the engine”.

  The first operating parameter is a parameter representing the current operating state of the engine. For example, “cooling water temperature, intake air temperature, engine load (intake air flow rate, engine rotational speed, load factor, in-cylinder intake air amount, throttle valve” Opening degree, accelerator pedal operation amount, etc.), the speed (vehicle speed) of the vehicle on which the engine is mounted, and the shift position of the transmission device mounted on the vehicle. Furthermore, the first operating parameter may include a content ratio (for example, alcohol concentration) of at least one component of the fuel used in the engine.

  For example, the fuel injection amount determining means determines a target air-fuel ratio from the coolant temperature, vehicle speed, shift position, etc., and determines a basic fuel amount from the cylinder intake air amount and the target air-fuel ratio. Since the value of the theoretical air-fuel ratio varies depending on the alcohol concentration, the fuel injection amount determining means determines the basic fuel amount according to the alcohol concentration if the alcohol concentration is acquired as the first operating parameter. Can be configured.

The valve timing control means includes
The valve opening / closing timing which is at least one of the opening timing of the intake valve of the engine and the closing timing of the exhaust valve of the engine is controlled so as to coincide with the target valve opening / closing timing.

  That is, the valve timing control means can change (adjust and control) at least one of the intake valve opening timing and the exhaust valve closing timing. The valve timing control means may be the hydraulic variable valve timing control device or the electric variable valve timing control device.

When the valve timing control means has a configuration that can control the intake valve opening timing and cannot control the exhaust valve closing timing, the valve opening and closing timing means "intake valve opening timing", The target valve opening / closing timing means “target timing for intake valve opening timing”.
When the valve timing control means has a configuration that can control the exhaust valve closing timing and cannot control the intake valve opening timing, the valve opening and closing timing means "exhaust valve closing timing", The target valve opening / closing timing means “target timing for exhaust valve closing timing”.
Further, when the valve timing control means has a configuration capable of controlling both the intake valve opening timing and the exhaust valve closing timing, the valve opening / closing timing is “intake valve opening timing and exhaust valve closing timing”. The target valve opening / closing timing means both “target timing of intake valve opening timing and target timing of exhaust valve closing timing”.

The atomization index value acquisition means includes
Based on the “second operating parameter representing the operating state of the engine”, a “atomization index value” representing “a degree of ease of atomization of the fuel injected from the fuel injection means” is acquired. It has become. “The degree of ease of atomization of fuel” refers not only to the property of the fuel itself (eg, volatility) but also to the operating state of the engine (eg, the temperature of the wall surface of the intake passage) that determines the degree of atomization of the fuel. It also changes depending on the cooling water temperature and the intake air temperature.

  Accordingly, the second operating parameter includes “a parameter indicating the current operating state of the engine” and / or “a content ratio of at least one component of the fuel used in the engine”. In particular, it is preferable that the second operating parameter includes one of parameters that greatly affect the “degree of ease of fuel atomization”. That is, the second operating parameter includes “cooling water temperature and / or intake air temperature” as a parameter representing the operating state, and “volatility is not good compared to gasoline” as a content ratio of at least one component of the fuel. It is desirable to include “the concentration of alcohol (for example, ethanol concentration)”.

The valve timing determining means includes
The target valve opening / closing timing is determined so that at least a part of the gas existing in the combustion chamber of the engine is blown back from the combustion chamber to the intake passage at the start timing of the exhaust stroke. In other words, when the actual valve opening / closing timing coincides with the target valve opening / closing timing, the valve timing determining means blows back the gas from the combustion chamber to the intake passage and atomizes the fuel by the blown back gas. The target valve opening / closing timing is determined so that the

This “blow-backed gas and fuel atomization by the gas” will be described with specific examples.
(1) When a negative valve overlap period is provided For example, as shown in FIG. 3A, the exhaust valve that has been opened in the exhaust stroke is closed before the intake top dead center. When closed at time EXc, as shown in FIGS. 4A and 4B, a part of the gas existing in the combustion chamber 25 at the start of the exhaust stroke, The gas remaining in the gas (gas that has not been discharged into the exhaust passage) is compressed in the combustion chamber 25.

  Next, as shown in FIG. 3A, when the intake valve is opened at the intake valve opening timing INo before the intake top dead center, as shown in FIG. By being compressed inside, “a gas having a pressure higher and higher than the pressure of the gas in the intake passage INP” is blown back from the combustion chamber 25 to the intake passage INP at a high flow rate.

  In this case, when fuel is injected from the fuel injection device 39 provided in the intake passage INP toward the “blowback gas”, the injected fuel is scattered and stirred by the “blowback gas” and heated. Is done. As a result, fuel atomization is promoted.

  On the other hand, when the fuel is injected into the intake passage INP from the fuel injection device 39 at a time before the “gas to be blown back” is generated, a part of the fuel is not atomized and the intake passage INP and the intake air It adheres to the back of the valve. Then, the fuel that has not been atomized is scattered (blown off) and heated by the “blow-backed gas”. As a result, fuel atomization is promoted. In this case, the period from the exhaust valve closing timing EXc to the intake valve opening timing INo is a “negative overlap period”.

  As is clear from the above, the valve timing determination means sets the target valve opening / closing timing as “a negative overlap period occurs and is blown back from the combustion chamber 25 to the intake passage INP after the end of the negative overlap period. When the gas is generated, the fuel can be atomized in the intake passage INP (at the time when atomization is promoted). The intake valve opening timing INo in this case may be after the intake top dead center as long as the gas pressure in the combustion chamber 25 is higher than the gas pressure in the intake passage INP. Furthermore, the degree to which the gas blown back to the intake passage INP can atomize the fuel (atomization ability) varies depending on “the flow velocity, temperature and total amount of the blown gas (particularly, the flow velocity is considered to be dominant). To do.

(2) When a positive valve overlap period is provided As shown in FIG. 5A, during the period in which the exhaust valve is open and the intake valve is closed in the exhaust stroke, the gas in the combustion chamber 25 is Exhaust into the exhaust passage EXP. After that, as shown in FIG. 3B and FIG. 5B, when the intake valve is opened at the intake valve opening timing INo, which is a predetermined timing within the period in which the exhaust valve is still open, As shown in FIG. 5C, a part of the gas existing in the combustion chamber 25 at the start of the exhaust stroke and remaining in the combustion chamber 25 (discharged to the exhaust passage EXP). The gas that has not been discharged is also pushed out to the intake passage INP. That is, also in this case, “gas blown back from the combustion chamber 25 to the intake passage INP” is generated.

  Therefore, even in this case, when fuel is injected from the fuel injection device 39 provided in the intake passage toward the “blowback gas”, the injected fuel is scattered and stirred by the “blowback gas”. . As a result, fuel atomization is promoted. On the other hand, when the fuel is injected from the fuel injection device 39 into the intake passage INP before the occurrence of the “returned gas”, the fuel adhering to the wall surface of the intake passage INP, the back surface of the intake valve, etc. It is scattered (blowed off) by the “blowed back gas”. As a result, fuel atomization is promoted. In this case, the period from the intake valve opening timing INo to the exhaust valve closing timing EXc is the “positive overlap period”.

  As is clear from the above, the valve timing determining means determines that the target valve opening / closing timing is “a positive overlap period occurs and gas is blown back into the intake passage INP during the positive overlap period. The time when fuel atomization in the intake passage INP occurs (promotes) can be determined. In this case, the intake valve opening timing INo is before the intake top dead center. Furthermore, the degree to which the gas blown back into the intake passage INP can atomize the fuel (atomization ability) varies depending on “the total amount and flow velocity of the gas blown back”.

Further, the valve timing determining means includes
The smaller the “degree of ease of atomization of the fuel” indicated by the atomization index value is, the more the fuel is atomized in the intake passage by the gas blown back into the intake passage. That is, the target valve opening / closing timing is determined so that the fuel atomization ability by the blown-back gas is improved. In other words, the valve timing determining means determines the target valve opening / closing timing so that at least one of the total amount of gas blown back, the flow velocity, the temperature, and the like increases as the fuel is more difficult to atomize.

  As described above, it takes time (that is, a response delay period occurs) for the actual valve opening / closing timing (actual valve opening / closing timing) to reach the target valve opening / closing timing. During the response delay period, the above-described “gas blown back to the intake passage” is not sufficiently suitable for the atomization index value, so that the fuel is not atomized appropriately.

Therefore, the fuel injection amount determining means is
“Correcting (increasing) the basic fuel amount” based on “valve opening / closing timing delay amount” indicating “the difference between the actual valve opening / closing timing and the target valve opening / closing timing, which is the actual timing of the valve opening / closing timing”. Thus, the “final amount of fuel” actually injected from the fuel injection means is determined.

  Thereby, in the period when the atomization ability of the fuel by the blown-back gas becomes insufficient (that is, the response delay period), the fuel injection amount is increased so as to compensate for the shortage of the atomization ability. Accordingly, since the air-fuel mixture containing “a sufficient amount of atomized fuel” is supplied into the combustion chamber, the cold startability of the engine is improved even when fuel that is difficult to atomize is used. be able to. Furthermore, as a result, the consumption of invalid fuel can be reduced.

  Thus, the fuel injection amount determination means corrects the fuel injection amount so that the fuel injection amount increases as the valve opening / closing timing delay amount increases. For this reason, when the valve opening / closing timing delay amount is very large, the fuel injection amount is increased by an extremely large amount. As a result, there is a possibility that the “total amount of invalid fuel increased by increasing by the correction” is larger than the “total amount of invalid fuel reduced by the cold start of the engine early”. In other words, by correcting the fuel injection amount as described above, the amount of fuel consumed before the engine is cold-started may increase.

Therefore, the control device according to the present invention is:
When the valve opening / closing timing delay amount is equal to or greater than a predetermined response delay threshold value, it is preferable to include a fuel injection stop unit that stops fuel injection from the fuel injection unit.

  According to this, when there is a high possibility that the fuel injection amount is excessively increased (that is, when the valve opening / closing timing delay amount is excessively large), the fuel injection is stopped. When the valve opening / closing timing delay amount gradually decreases with time (the actual valve opening / closing timing gradually approaches the target valve opening / closing timing) and the valve opening / closing timing delay amount becomes smaller than the response delay threshold, Is started. The amount of fuel injected at this time is “the fuel injection amount corrected according to the valve opening / closing timing delay amount at this time”, and “corrected when the valve opening / closing timing delay amount is equal to or greater than the response delay threshold value”. Smaller than the “performed fuel injection amount”. As a result, since it is possible to avoid the fuel injection amount from being corrected to increase excessively, the amount of fuel consumed before the engine is cold-started can be further reduced.

In this case, the fuel injection stopping means is
It is preferable to include a response delay threshold value determination unit that determines the response delay threshold value so that the response delay threshold value decreases as the coolant temperature of the engine decreases or the alcohol content in the fuel increases. is there.

Alternatively, the fuel injection stopping means is
The response delay threshold value is determined such that the response delay threshold value decreases as “the degree of ease of atomization of the fuel indicated by the atomization index value” decreases, that is, as the fuel becomes more difficult to atomize. It is preferable to include a response delay threshold value determining means. That is, the response delay threshold value can be determined, for example, such that the response delay threshold value decreases as the engine coolant temperature decreases, and the response delay threshold value decreases as the alcohol content in the fuel increases.

  According to these, fuel injection is stopped until the valve opening / closing timing delay amount reaches a smaller amount as the fuel is more difficult to be finely divided. This is because the amount of increase in the fuel injection amount increases as the fuel is more difficult to be finely divided even if the valve opening / closing timing delay amount is the same. As a result, since it is possible to more reliably avoid the fuel injection amount from being corrected to increase excessively, the amount of fuel consumed before the engine is cold-started can be further reliably reduced.

  Furthermore, the control device of the present invention may include “a cranking prohibiting unit that prohibits (stops) cranking of the engine during a period in which the fuel injection is stopped by the fuel injection stopping unit”. Good. According to this, since the useless cranking is not executed while the fuel injection is stopped, the power consumed for the useless cranking can be saved. In addition, the control device according to the present invention may be configured to notify the operator of the engine that the cranking is stopped when the cranking of the engine is prohibited by the cranking prohibiting unit (for example, It may be configured to include a display lamp that indicates stop / execution of cranking by turning on / off.

1 is a schematic cross-sectional view of an internal combustion engine to which a control device of the present invention is applied. It is the schematic which shows the combustible intake timing control apparatus of the internal combustion engine shown in FIG. It is a figure which shows the change with respect to the crank angle of the lift amount of the intake valve of an internal combustion engine, and the lift amount of an exhaust valve. It is a schematic diagram which shows the operating state of the piston of an internal combustion engine, an intake valve, and an exhaust valve when a negative overlap period is set. It is a schematic diagram which shows the operating state of the piston of an internal combustion engine, an intake valve, and an exhaust valve when a positive overlap period is set. It is a figure which shows the atomization index value table employ | adopted when acquiring the atomization index value in the 1st control apparatus of this invention. It is a figure which shows the 1st correction coefficient table employ | adopted when determining a 1st correction coefficient in the 1st control apparatus of this invention. It is a figure which shows the 2nd correction coefficient table employ | adopted when determining a 2nd correction coefficient in the 1st control apparatus of this invention. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 1st control apparatus of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 1st control apparatus of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 1st control apparatus of this invention performs. It is a figure which shows the response delay threshold value acquisition table employ | adopted as the 2nd control apparatus of this invention. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 2nd control apparatus of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 3rd control apparatus of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 3rd control apparatus of this invention performs.

  Embodiments of an internal combustion engine control apparatus according to the present invention will be described below with reference to the drawings.

(First embodiment)
<Outline of device>
FIG. 1 shows a schematic configuration of a system in which a control device according to a first embodiment of the present invention (hereinafter also referred to as “first control device”) is applied to an internal combustion engine 10. The engine 10 is a four-cycle spark ignition multi-cylinder (four-cylinder) engine. FIG. 1 shows only a cross section of a specific cylinder of the engine 10, but other cylinders have the same configuration.

  The engine 10 supplies a gasoline mixture to the cylinder block unit 20 including a cylinder block, a cylinder block lower case, an oil pan, etc., a cylinder head unit 30 fixed on the cylinder block unit 20, and the cylinder block unit 20. And an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside, and a fuel system 60 for supplying fuel to the intake system 40.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The wall surface of the cylinder 21 and the upper surface of the piston 22 form a combustion chamber 25 together with the lower surface of the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft (not shown) that drives the intake valve 32, and a phase angle of the intake camshaft. The variable intake timing control device 33 that changes continuously, the actuator 33a of the variable intake timing control device 33, the exhaust port 34 that communicates with the combustion chamber 25, the exhaust valve 35 that opens and closes the exhaust port 34, and the exhaust cam that drives the exhaust valve 35 A variable exhaust timing control device 36 that includes a shaft (not shown) and continuously changes the phase angle of the exhaust camshaft, an actuator 36a of the variable exhaust timing control device 36, a spark plug 37, and a high voltage applied to the spark plug 37 Igna including ignition coil generated Motor 38 and, comprises an injector (fuel injection means) 39 for injecting into the intake port 31 of the fuel.

  The variable intake timing control device 33 (variable valve timing mechanism) is a well-known device as described in, for example, Japanese Patent Application Laid-Open No. 2007-303423. Hereinafter, the variable intake timing control device 33 will be briefly described with reference to FIG. 2, which is a schematic sectional view of the variable intake timing control device 33.

  The variable intake timing control device 33 includes a timing pulley 33b1, a cylindrical housing 33b2, a rotating shaft 33b3, a plurality of partition walls 33b4, and a plurality of vanes 33b5.

  The timing pulley 33b1 is configured to be rotated in the direction of arrow R by the crankshaft 24 of the engine 10 via a timing belt (not shown). The cylindrical housing 33b2 rotates integrally with the timing pulley 33b1. The rotating shaft 33b3 rotates integrally with the intake camshaft and can rotate relative to the cylindrical housing 33b2. The partition wall 33b4 extends from the inner peripheral surface of the cylindrical housing 33b2 to the outer peripheral surface of the rotating shaft 33b3. The vane 33b5 extends from the outer peripheral surface of the rotating shaft 33b3 to the inner peripheral surface of the cylindrical housing 33b2 between two adjacent partition walls 33b4. With such a structure, an advance hydraulic chamber 33b6 and a retard hydraulic chamber 33b7 are formed on both sides of each vane 33b5. The advance hydraulic chamber 33b6 and the retard hydraulic chamber 33b7 are configured such that when hydraulic oil is supplied to one, the hydraulic oil is discharged from the other.

  The hydraulic oil supply control (supply / discharge) to the advance hydraulic chamber 33b6 and the retard hydraulic chamber 33b7 is performed by the actuator 33a shown in FIG. 1 including the hydraulic oil supply control valve and a hydraulic pump (not shown). Done. The actuator 33a is of an electromagnetic drive type and performs supply control of the hydraulic oil in response to an instruction signal (drive signal). That is, when the phase of the cam of the intake camshaft is to be advanced, the actuator 33a supplies hydraulic oil to the advance hydraulic chamber 33b6 and discharges hydraulic oil in the retard hydraulic chamber 33b7. At this time, the rotation shaft 33b3 is rotated relative to the cylindrical housing 33b2 in the direction of the arrow R. On the other hand, when the phase of the cam of the intake camshaft is to be retarded, the actuator 33a supplies hydraulic oil to the retard hydraulic chamber 33b7 and discharges hydraulic fluid in the advance hydraulic chamber 33b6. At this time, the rotation shaft 33b3 is rotated relative to the cylindrical housing 33b2 in the direction opposite to the arrow R.

  Further, when the actuator 33a stops supplying and discharging hydraulic fluid to the advance hydraulic chamber 33b6 and the retard hydraulic chamber 33b7, the relative rotation operation of the rotary shaft 33b3 with respect to the cylindrical housing 33b2 is stopped, and the rotary shaft 33b3 The relative rotational position at that time is held. Thus, the variable intake timing control device 33 can advance and retard the phase of the cam of the intake camshaft by a desired amount. Furthermore, the variable intake timing control device 33 is configured such that the period during which the intake valve 32 is open (the valve opening crank angle width) is constant. Therefore, when the intake valve opening timing is advanced or retarded by a predetermined angle by the variable intake timing control device 33, the closing timing of the intake valve 32 is also advanced or retarded by the predetermined angle.

  The above-described variable intake timing control device 33 may be replaced with, for example, an “electric variable intake timing control device” disclosed in Japanese Patent Application Laid-Open No. 2004-150397. This electric variable intake timing control device includes an electromagnetic coil and a plurality of gears. This device changes the relative rotational positions of the plurality of gears by the magnetic force generated by the electromagnetic coil in response to an instruction signal (drive signal), thereby leading or shifting the phase of the cam of the intake camshaft by a desired amount. It can be retarded.

  On the other hand, the variable exhaust timing control device 36 is attached to the end of the exhaust camshaft. The variable exhaust timing control device 36 has the same configuration as the hydraulic variable intake timing control device 33 described above. Furthermore, the variable intake timing control device 33 and the variable exhaust timing control device 36 can control the opening / closing timing of the intake valve 32 and the exhaust valve 35 independently of each other. The variable exhaust valve timing control device 36 may also be replaced with an electric variable exhaust timing control device, as described above.

  Referring again to FIG. 1, the intake system 40 includes an intake pipe 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, and an air filter 42 provided at an end of the intake pipe 41. And a throttle valve 43 in the intake pipe 41 that makes the opening cross-sectional area of the intake passage variable. The throttle valve 43 is rotationally driven in the intake pipe 41 by a throttle valve actuator 43a made of a DC motor.

  The exhaust system 50 includes an exhaust manifold 51 including a plurality of branches connected at one end to the exhaust port 34 of each cylinder, and the other ends of the branches of each exhaust manifold 51 and all branches are assembled. An exhaust pipe 52 connected to the collecting portion, and a known three-way catalyst (catalyst) 53 disposed in the exhaust pipe 52 are provided. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  The fuel system 60 includes a fuel tank 61, a fuel supply pipe 62, and a fuel heating device 63.

  The fuel tank 61 stores “a fuel in which gasoline and ethanol are mixed”. The fuel tank 61 may be filled with a fuel made of only gasoline that does not contain any ethanol, or a fuel made of only ethanol that does not contain any gasoline.

  The fuel supply pipe 62 is a pipe that connects the fuel tank 61 and the injector 39. The fuel in the fuel tank 61 is pumped to the injector 39 via the fuel supply pipe 62 by a fuel pump (not shown) disposed in the fuel tank 61.

  The fuel heating device 63 is a known fuel heating device (for example, an electric heater) as described in, for example, Japanese Patent Application Laid-Open No. 2007-198308. The fuel heating device 63 is switched to an operating state and a stopped state based on the instruction signal. Further, the fuel heating device 63 can adjust “the amount of heat generated during operation” based on the instruction signal. Thereby, the fuel heating device 63 can heat the fuel flowing through the fuel supply pipe 62 and adjust (increase) the temperature of the fuel supplied to the injector 39.

  The first control device includes a hot-wire air flow meter 71, an intake air temperature sensor 72, a throttle position sensor 73, an intake cam position sensor 74, an exhaust cam position sensor 75, a crank position sensor 76, a water temperature sensor 77, an upstream air-fuel ratio sensor 78, A downstream air-fuel ratio sensor 79, an accelerator opening sensor 81, a vehicle speed sensor 82, a shift position sensor 83 for the transmission, and an alcohol concentration sensor 84 are provided.

  The air flow meter 71 corresponds to the mass flow rate of intake air flowing through the intake pipe 41 (the mass of air sucked into the engine 10 per unit time. In the present invention, it is also referred to as “intake air flow rate”) Ga. A signal is output.

  The intake air temperature sensor 72 outputs a signal corresponding to the temperature THA of the intake air flowing through the intake pipe 41.

  The throttle position sensor 73 detects the opening (throttle valve opening) of the throttle valve 43 and outputs a signal corresponding to the throttle valve opening TA.

  The intake cam position sensor 74 is disposed in the vicinity of the intake cam shaft. The intake cam position sensor 74 generates a signal having one pulse every time the intake cam shaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °).

  The exhaust cam position sensor 75 is disposed in the vicinity of the exhaust cam shaft. The exhaust cam position sensor 75 generates a signal having one pulse every time the exhaust cam shaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °).

  The crank position sensor 76 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a wide pulse every time the crankshaft 24 rotates 360 °.

  The water temperature sensor 77 detects the temperature of the cooling water of the engine 10 and outputs a signal corresponding to the cooling water temperature THW.

  The upstream air-fuel ratio sensor 78 is disposed on the exhaust passage, upstream of the catalyst 53 and downstream of the collection portion of the branches of the exhaust manifold 51. The upstream air-fuel ratio sensor 78 is a well-known limit current type oxygen concentration sensor, and corresponds to the air-fuel ratio of exhaust gas (detected gas) flowing through a portion in the exhaust passage where the upstream air-fuel ratio sensor 78 is disposed. Output value is output.

  The downstream air-fuel ratio sensor 79 is disposed on the downstream side of the catalyst 53 in the exhaust passage. The downstream air-fuel ratio sensor 79 is a known electromotive force type oxygen concentration sensor, and outputs an output value corresponding to the air-fuel ratio of the exhaust gas flowing through the portion where the downstream air-fuel ratio sensor 79 is disposed. Yes.

  The accelerator opening sensor 81 outputs a signal corresponding to the opening Accp of the accelerator pedal AP operated by the driver.

  The vehicle speed sensor 82 outputs a signal corresponding to the vehicle speed SPD based on a pulse generated each time the driving wheel rotates by a certain angle.

  The shift position sensor 83 of the transmission outputs a signal corresponding to the shift lever position (shift position) P of the automatic transmission that transmits the output of the engine 10 to the drive wheels.

  The alcohol concentration sensor 84 is, for example, a well-known capacitance type sensor (a sensor capable of measuring the relative dielectric constant of a measurement object using a pair of electrodes) as described in JP-A-6-27073. It is. The alcohol concentration sensor 84 utilizes the fact that the relative permittivity of the alcohol-mixed fuel changes according to the alcohol concentration, and the alcohol concentration of the fuel flowing through the portion in the fuel supply pipe 62 where the alcohol concentration sensor 84 is disposed ( The engine 10 outputs an output value corresponding to the ethanol concentration Cetha).

  The electric control device 90 is a microcomputer including a CPU 91, a ROM 92, a RAM 93, a backup RAM 94, an interface 95 including an AD converter, and the like connected to each other by a bus.

  The interface 95 is connected to the sensors and the like, and supplies signals from the sensors and the like to the CPU 91. Further, the interface 95 is connected to each actuator (the actuator 33a of the variable intake timing control device 33, the actuator 36a of the variable exhaust timing control device 36, etc.), the injector 39, the fuel heating device 63, etc. in accordance with an instruction from the CPU 91. A drive signal (instruction signal) is transmitted.

  Next, the operation of the first control device will be described. The first control device acquires a “atomization index value” indicating the degree of ease of atomization of fuel (degree of atomization of fuel) based on the operating state of the engine 10 and the like, and the atomization index value Based on the above, the “target valve opening / closing timing” is determined. More specifically, the first control device blows back into the intake passage as the “degree of ease of fuel atomization” indicated by the atomization index value decreases (that is, the degree of difficulty in atomizing fuel). “The target of the exhaust valve” is such that the fuel is atomized more in the intake passage by the gas to be discharged (ie, the fuel atomization by the gas blown back into the intake passage is “promoted”). Determine the valve closing time.

  Then, the first control device controls the closing timing of the exhaust valve so that the “actual closing timing of the exhaust valve” matches the “target closing timing of the exhaust valve”. Further, the first control device acquires a difference (valve opening / closing timing delay amount) between the actual valve closing timing of the exhaust valve and the target valve closing timing of the exhaust valve, and corrects (increases) the fuel injection amount according to the difference. to correct. Thereby, even when the actual valve closing timing of the exhaust valve is different from the target valve closing timing of the exhaust valve, a sufficient amount of “atomized fuel (fuel droplets)” is sucked into the combustion chamber 25. be able to. Therefore, the first control device can improve the starting performance of the engine 10.

  Hereinafter, before explaining the actual operation of the first control device, “the atomization of the fuel by the blow-back gas to the intake passage” adopted by the first control device and the control device according to another embodiment of the present invention to be described later. The outline of “acceleration control” will be described. Hereinafter, the control device according to each embodiment of the present invention is simply referred to as “control device”.

<Fuel atomization promotion control by blow-back gas>
The control device changes at least one of “the opening timing of the intake valve” and “the closing timing of the exhaust valve” in accordance with the atomization index value. As will be described later, even if any one of “intake valve opening timing” and “exhaust valve closing timing” is changed, “the degree of acceleration of atomization of fuel by the gas blown back into the intake passage (that is, the intake passage) The amount of gas blown back into the fuel is such that the fuel can be atomized, and is simply referred to as “atomization ability”).

  Therefore, when the control device attempts to change the atomization capability by changing the “intake valve opening timing”, the “intake valve target opening timing” which is the target value of the “intake valve opening timing”. And the variable intake timing control device 33 is driven so that the actual intake valve opening timing (actual intake valve opening timing) matches the intake valve target valve opening timing. Alternatively, when the control device attempts to change the atomization capability by changing the “exhaust valve closing timing”, the “exhaust valve target closing timing” which is the target value of the “exhaust valve closing timing”. And the variable exhaust timing control device 36 is driven so that the actual exhaust valve closing timing (actual exhaust valve closing timing) matches the exhaust valve target closing timing.

  As is apparent from the above description, the control device determines “both” of “target intake valve opening timing” and “target exhaust valve close timing” according to the atomization index value, and opens the actual intake valve. The variable intake timing control device 33 is driven so that the valve timing matches the intake valve target opening timing, and the variable exhaust timing control device 36 so that the actual exhaust valve closing timing matches the exhaust valve target closing timing. May be driven.

  On the other hand, the control device may determine “only one” of “intake valve target opening timing” and “exhaust valve target closing timing” according to the atomization index value. If the control device is configured to determine only the “intake valve target opening timing” of these two target timings, the actual intake valve opening timing matches the intake valve target opening timing. The variable intake timing control device 33 is driven and the exhaust valve closing timing is fixed. Therefore, in this case, the engine 10 may not include the variable exhaust timing control device 36. If the control device is configured to determine only the “exhaust valve target closing timing” of these two target timings, the actual exhaust valve closing timing matches the exhaust valve target closing timing. The variable exhaust timing control device 36 is driven, and the intake valve opening timing is fixed. Therefore, in this case, the engine 10 may not include the variable intake timing control device 33.

  In the present specification and the appended claims, the term “intake valve opening timing and exhaust valve closing timing” which is changed for the purpose of changing the atomization capability is “valve opening / closing timing”. Collectively. Similarly, “target intake valve opening timing and exhaust valve target closing timing”, which are target values of valve opening / closing timing, are collectively referred to as “target valve opening / closing timing”.

  The control device sets the target valve opening / closing timing according to the gas blown back into the intake passage as the “degree of ease of fuel atomization” indicated by the atomization index value becomes smaller (that is, the fuel is less likely to atomize). It is determined that the fuel is atomized more in the intake passage (that is, the fuel atomization by the gas blown back into the intake passage is “promoted”). “The atomization of fuel by the gas blown back into the intake passage is further promoted” is synonymous with “the ability to atomize the blow-back gas is increased”.

  The control device controls either one of the so-called “negative overlap period (negative valve overlap period)” and the so-called “positive overlap period (positive valve overlap period)”. Control ability. The negative overlap period is a period in which both the intake valve 32 and the exhaust valve 35 are “closed” when the exhaust stroke is shifted to the intake stroke. The positive overlap period is a period in which both the intake valve 32 and the exhaust valve 35 are “open” when shifting from the exhaust stroke to the intake stroke.

  Hereinafter, this point will be described in more detail with reference to FIGS. FIG. 3A shows “change in lift amount of intake valve 32 and exhaust valve 35 with respect to crank angle” when a negative overlap period is set. FIG. 3B shows “change in lift amount of intake valve 32 and exhaust valve 35 with respect to crank angle” when a positive overlap period is set. FIG. 4 is a schematic diagram showing “the operating states of the piston 22, the intake valve 32, and the exhaust valve 35 of the engine 10” when the “negative overlap period” is set. FIG. 5 is a schematic diagram showing the “operating states of the piston 22, the intake valve 32, and the exhaust valve 35 of the engine 10” when the “positive overlap period” is set.

-Fuel atomization by negative overlap period As shown to Fig.3 (a), the control apparatus can set the negative overlap period OLn. More specifically, the control device sets the intake valve opening timing INo to a timing advanced by the “first angle Din” from the intake top dead center (intake TDC), and sets the exhaust valve closing timing Exc. It is set at a time when the angle is advanced by “a second angle Dex larger than the first angle Din” from the intake top dead center. The negative overlap period OLn corresponds to a “difference” between the second angle Dex and the first angle Din.

  When the exhaust valve 35 is changed from the open state to the closed state at the exhaust valve closing timing EXc during the exhaust stroke in which the intake valve 32 is in the closed state and the exhaust valve 35 is in the open state, FIG. As shown in 4 (a), the gas is confined in the combustion chamber 25 of the engine 10. That is, the exhaust valve closing timing EXc is the starting point of the negative overlap period OLn. As shown in FIG. 4B, when the piston rises toward the intake top dead center as the crank angle of the engine 10 increases, the gas in the combustion chamber 25 (in the cylinder) is compressed. . At this time, since the gas in the combustion chamber 25 is considered to be substantially adiabatically compressed, the pressure and temperature rise as the gas in the combustion chamber 25 is compressed.

  The pressure of the air in the intake passage INP is at most atmospheric pressure. The pressure of air in the intake passage INP generally matches the atmospheric pressure when the engine is cold started. On the other hand, the pressure of the gas compressed in the combustion chamber 25 is usually greater than atmospheric pressure. Therefore, when the intake valve 32 is opened at the end point of the negative overlap period OLn (that is, the intake valve opening timing INo), as shown by the arrow G in FIG. The gas inside blows out toward the intake passage INP. Blowing the gas in the combustion chamber 25 toward the intake passage INP is referred to as “blowback”.

  On the other hand, the fuel is injected from the injector 39 into the intake passage INP. Therefore, when fuel is injected toward the above-mentioned “returned gas”, the fuel collides with “returned gas that has become hot due to being compressed in the combustion chamber 25”. As a result, the injected fuel is atomized in the intake passage INP by heating and stirring.

  On the other hand, for example, in particular, when fuel is injected “before” the gas is blown back into the intake passage INP, a part of the fuel is part of the wall surface of the intake passage INP (for example, the wall surface of the intake port 31) and the intake valve 32. Adhere to the surroundings. Even in this case, the attached fuel can be blown off by the above-mentioned “blow-backed gas”. The fuel blown off is further heated by the blown-back gas. As a result, the injected fuel and attached to the wall surface of the intake passage INP is atomized in the intake passage INP.

  As described above, when the exhaust valve closing timing is set before the intake top dead center and a “negative overlap” occurs in the vicinity of the intake top dead center, the gas in the combustion chamber 25 is compressed, The gas temperature and pressure increase. Then, by setting the intake valve opening timing to “a timing when the gas pressure in the combustion chamber 25 is higher than the gas pressure in the intake passage INP”, the gas in the combustion chamber 25 is blown back into the intake passage INP. As a result, fuel atomization can be promoted.

  The temperature and flow rate of the blown-back gas increase as the gas pressure in the combustion chamber 25 increases at the intake valve opening timing INo. Therefore, when the atomization of fuel is promoted by providing the negative overlap period OLn, the “exhaust valve with respect to the volume VinO of the combustion chamber 25 at the intake valve opening timing INo (end point of the negative overlap period OLn)”. The greater the ratio (VexC / VinO) of the volume VexC of the combustion chamber 25 at the valve closing timing Exc (start point of the negative overlap period OLn), the greater the atomization ability of the blow-back gas.

  Generally, the intake valve opening timing INo is set before the intake top dead center. Accordingly, if the intake valve opening timing INo is fixed at a timing advanced by a slight predetermined angle from the intake top dead center, the negative overlap period OLn becomes larger (that is, the exhaust valve closing time). As the valve timing Exc moves away from the intake top dead center and approaches the exhaust bottom dead center (expansion bottom dead center), the atomization ability of the blow-back gas increases. Further, if the exhaust valve closing timing Exc is fixed at a predetermined angle before the intake top dead center, the blown-back gas atomization ability increases as the intake valve opening timing INo approaches the intake top dead center. Become.

  Based on the viewpoint described above, the control device determines the “target valve opening / closing timing” according to the “atomization index value” of the fuel, and accordingly, the length of the negative overlap period and the negative overlap period are determined. By changing the existing period, the “blowing gas atomization ability” is changed. In other words, the control apparatus increases the atomization ability of the blow-back gas as the fuel is less atomized. Therefore, if the actual “valve opening / closing timing” coincides with the “target valve opening / closing timing”, the fuel is appropriately atomized, so the amount of atomized fuel to be used for combustion in the combustion chamber 25 Is the appropriate amount. As a result, for example, the starting performance at the time of cold starting of the engine 10 is improved. The intake valve opening timing INo in this case may be after the intake top dead center as long as the gas pressure in the combustion chamber 25 is higher than the gas pressure in the intake passage INP.

-Fuel atomization by the positive overlap period As shown in FIG. 3 (b), the control device may change the "spraying gas atomization ability" by changing the positive overlap period OLp. it can. More specifically, the control device sets the intake valve opening timing INo to a timing advanced by the “first angle Din” from the intake top dead center (intake TDC), and sets the exhaust valve closing timing Exc. It is set at a time when the intake angle is advanced by “a second angle Dex smaller than the first angle Din” from the intake top dead center. The positive overlap period OLp corresponds to a “difference” between the first angle Din and the second angle Dex.

  When both the intake valve 32 and the exhaust valve 35 are in the closed state, as shown in FIG. 5A, when the exhaust valve 35 is changed from the closed state to the open state, the exhaust passage EXP Communicates with the combustion chamber 25. Then, as indicated by an arrow G in FIG. 5B, the gas in the combustion chamber 25 is discharged to the exhaust passage EXP. After that, as shown in FIG. 5B, the intake valve 32 is changed from the closed state to the open state at the intake valve opening timing INo (that is, the start point of the positive overlap period OLp). Then, the intake passage INP also communicates with the combustion chamber 25. Then, as shown in FIG. 5 (c), when the piston rises as the crank angle of the engine increases, the gas in the combustion chamber 25 is blown out toward both the intake passage INP and the exhaust passage EXP. (Extruded)

  Here, when fuel is injected from the injector 39 into the intake passage INP during the period when the gas is blown back into the intake passage INP, as in the case where the above-described “negative overlap” occurs, the injected fuel is The gas collides with the gas blown back into the intake passage INP. As a result, the injected fuel is atomized in the intake passage INP by scattering and stirring.

  Further, when fuel is injected “before” the gas is blown back into the intake passage INP, the fuel adhering to the wall surface of the intake passage INP is blown off by the “blowed back gas” described above. As a result, the fuel that has been injected and adhered to the wall surface or the like of the intake passage INP is atomized in the intake passage INP.

  As described above, if a “positive overlap” occurs near the intake top dead center, the atomization of fuel is caused by the gas blown back to the intake passage INP, as in the case of the “negative overlap”. Can be promoted. The amount of gas blown back increases as the positive overlap period OLp existing before the intake top dead center increases. That is, by increasing the positive overlap period OLp existing before the intake top dead center, it is possible to increase the atomization ability of the blown-back gas. Also, the amount of gas blown back varies depending on the time when the positive overlap period exists.

  Based on the viewpoint described above, the control device determines the “target valve opening / closing timing” in accordance with the “atomization index value” of the fuel, so that the length of the positive overlap period and the positive overlap period are determined. By changing the existing period, the “blowing gas atomization ability” is changed. In other words, the control apparatus increases the atomization ability of the blow-back gas as the fuel is less atomized. Therefore, if the actual “valve opening / closing timing” coincides with the “target valve opening / closing timing”, the fuel is appropriately atomized, so the amount of atomized fuel to be used for combustion in the combustion chamber 25 Is the appropriate amount. As a result, for example, the starting performance at the time of cold starting of the engine 10 is improved.

  However, when the “positive overlap” is generated, the gas in the combustion chamber 25 is not compressed by the intake valve opening timing INo, unlike the case of generating the “negative overlap” described above. Therefore, the temperature of the gas blown back does not substantially increase. Further, the flow velocity of the gas blown back in the positive overlap period is often smaller than the flow velocity of the gas blown back when the “negative overlap” is generated. Therefore, when the engine 10 is cold-started, rather than determining the target valve opening / closing timing so as to generate a “positive overlap” in the vicinity of the intake top dead center, the “negative overlap” in the vicinity of the intake top dead center. It is preferable to determine the target valve opening / closing timing so as to cause

  On the other hand, once the engine 10 is started (that is, after the first explosion after the first combustion), burned gas generated by the combustion is generated in the combustion chamber 25. Therefore, the pressure and temperature of the gas in the combustion chamber 25 at the expansion bottom dead center are extremely high. Therefore, the temperature of the gas blown back to the intake passage INP in the positive overlap period OLp is extremely higher than the gas (such as the atmosphere) in the intake passage INP, and the flow velocity of the blown back gas is also large. As a result, once the engine is started, fuel atomization can be more effectively promoted by determining the target valve opening / closing timing so as to generate a “positive overlap” in the vicinity of the intake top dead center. can do.

  As described above, the control device determines whether the target valve opening / closing timing (that is, the target valve opening / closing timing for determining the length and existence time of the positive overlap period, or the length and existence time of the negative overlap period). The target valve opening / closing timing for determining the fuel is such that the smaller the “degree of ease of atomization of the fuel” indicated by the atomization index value, the greater the atomization ability by the gas blown back to the intake passage INP. decide. The atomization ability varies depending on the flow rate, temperature and total amount of gas blown back into the intake passage. Therefore, the target valve opening / closing timing can be determined in advance by experiments in consideration of them.

<Fuel atomization promotion control by the blow back gas of the first control device>
The first control device promotes fuel atomization by adjusting the “negative overlap period”. More specifically, the first control device optimizes fuel atomization by changing the “exhaust valve closing timing Exc”, which is the starting point of the negative overlap period OLn, according to the atomization index value. To do. Here, the first control device fixes “the intake valve opening timing INo”, which is the end point of the negative overlap period OLn, to “the timing advanced by a slight predetermined angle from the intake top dead center”.

<Acquisition of atomization index value>
As described above, the first controller acquires the fuel atomization index value based on the operating state of the engine 10. Hereinafter, the method for obtaining the atomization index value employed by the first control device will be described with reference to FIG. As described above, the fuel atomization index value is a value indicating the degree of ease of atomization of the fuel, and is a value indicating that the larger the value, the easier the fuel is atomized.

  The first controller stores the atomization index value table MapAtmz (THW, Cetha, THA) shown in FIG. This atomization index value table MapAtmz (THW, Cetha, THA) predetermines “relationship between cooling water temperature THW, ethanol concentration Cetha and intake air temperature THA, and atomization index value Atmz” based on experimental data. It is a look-up table (3-input 1-output type). The first control device applies the actual “cooling water temperature THW, ethanol concentration Cetha and intake air temperature THA” acquired from the output value of the sensor to the atomization index value table MapAtmz (THW, Cetha, THA). The index value Atmz is acquired.

  In FIG. 6A, the solid line A1low and the broken line A1high are both “isolines” in which the atomization index value Atmz takes the “first value (maximum value A1)”. However, the solid line A1low is an isoline when the intake air temperature THA is “first intake air temperature”, and the broken line A1high is when the intake air temperature THA is “second intake air temperature higher than the first intake air temperature”. It is a value line.

  Both the solid line A2low and the broken line A2high are isoline lines in which the atomization index value Atmz takes a “second value A2 smaller than the first value”. However, the solid line A2low is an isoline when the intake air temperature THA is the first intake air temperature, and the broken line A2high is an isoline when the intake air temperature THA is the second intake air temperature.

  The solid line A3low and the broken line A3high are isoline lines in which the atomization index value Atmz takes a “third value A3 smaller than the second value”. However, the solid line A3low is an isoline when the intake air temperature THA is the first intake air temperature, and the broken line A3high is an isoline when the intake air temperature THA is the second intake air temperature.

  Further, the atomization index value Atmz between “one isoline” and “other isolines adjacent to the one isoline” is the atomization index indicated by the one isoline. It is obtained by interpolation (for example, well-known linear interpolation) based on the value and the atomization index value indicated by another isoline.

  Since the atomization index value Atmz is a value indicating that the fuel is more easily atomized as the value is larger, as shown in FIG. 6A, the higher the cooling water temperature THW, the larger the ethanol concentration Cetha. It is determined to be larger. Further, the atomization index value Atmz is determined so as to increase as the intake air temperature THA increases. Hereinafter, this point will be described in more detail with reference to FIG.

  FIG. 6B shows the “relationship between the cooling water temperature THW and the intake air temperature THA and the atomization index value Atmz obtained when the ethanol concentration Cetha is a fixed value C1 (Cetha = C1) in FIG. 6A. It is the graph which showed. Also in FIG. 6B, the solid line shows the atomization index value Atmz when the intake air temperature THA is the first intake air temperature, and the broken line shows the second intake air temperature when the intake air temperature THA is higher than the first intake air temperature. Shows the atomization index value Atmz.

  As shown by the “solid line” in FIG. 6B, when the intake air temperature THA is the “relatively low first intake air temperature”, the atomization index value Atmz is obtained when the cooling water temperature THW is lower than the temperature T1. The coolant temperature THW increases as the coolant temperature THW increases, and reaches the maximum value A1 when the coolant temperature THW reaches the temperature T1. Further, the atomization index value Atmz maintains the maximum value A1 when the cooling water temperature THW is equal to or higher than the temperature T1.

  In addition, as shown by the “broken line” in FIG. 6B, when the intake air temperature THA is “relatively high second intake air temperature”, the atomization index value Atmz has the cooling water temperature THW “from the temperature T1. When the cooling water temperature THW increases, the maximum value A1 is reached when the cooling water temperature THW reaches the temperature T2. Further, the atomization index value Atmz maintains the maximum value A1 when the cooling water temperature THW is equal to or higher than the temperature T2.

  That is, in the range where the cooling water temperature THW is lower than the temperature T1, even if the cooling water temperature THW is the same, the atomization index value Atmz increases as the intake air temperature THA increases (at the temperature T3 in FIG. 6B). (See the example shown.) In other words, the atomization index value Atmz increases as the intake air temperature THA increases in a range where the coolant temperature THW is lower than the temperature T1. As a result, in FIG. 6A showing the tendency of the atomization index value table MapAtmz (THW, Cetha, THA), the higher the intake air temperature THA, the more the contour line becomes “the direction in which the atomization index value Atmz becomes smaller. (Upper left) ”. Thus, according to the atomization index value table MapAtmz (THW, Cetha, THA), the atomization index value Atmz is obtained so as to have the above-described tendency.

<Calculation of fuel injection amount (correction)>
As described above, the first control device determines the “valve opening / closing timing delay amount” which is the difference between the actual exhaust valve closing timing (actual valve opening / closing timing) and the exhaust valve target closing timing (target valve opening / closing timing). The fuel injection amount is corrected according to the valve opening / closing timing delay amount. Hereinafter, the fuel injection amount calculation (correction) method employed by the first control device will be described with reference to FIGS. 7 and 8.

  First, the first control device determines a fuel injection amount (basic fuel amount TAUbase) before correction based on a first operating parameter representing an operating state of the engine 10. The base fuel amount TAUbase is based on the assumption that fuel atomization is assumed to be in advance (for example, the coolant temperature THW is a temperature indicating completion of warm-up and the ethanol concentration is 0%). It is determined using a predetermined look-up table, a correction coefficient, and the like so that an appropriate air-fuel ratio corresponding to the ten operating states can be obtained.

  The first operating parameter is a parameter that represents the current operating state of the engine 10. For example, “cooling water temperature THW, intake air temperature THA, engine load (intake air flow rate Ga, engine rotational speed NE, load factor KL, in-cylinder” Intake air amount Mc, throttle valve opening TA, accelerator pedal operation amount Accp, etc.), vehicle speed (vehicle speed SPD) on which the engine is mounted, and shift position P of the transmission mounted on the vehicle, etc. Including at least one. Further, the first operating parameter includes a content ratio of at least one component of the fuel used in the engine 10.

  “At least one component of the fuel” can be a “fuel component that is difficult to atomize in a low temperature environment” among the fuel components contained in the fuel. Examples of the “fuel component that is difficult to atomize in a low temperature environment” include alcohols such as methanol, ethanol, butanol and propanol. The engine 10 to which the first control device is applied uses “a fuel in which gasoline and ethanol are mixed”. Therefore, the first control device adopts the ethanol concentration Cetha of the fuel as “a content ratio of at least one fuel component contained in the fuel”.

  As described above, the first control device optimizes fuel atomization by changing the “exhaust valve closing timing Exc”, which is the starting point of the negative overlap period OLn, according to the atomization index value. . That is, the first control device determines the “exhaust valve target closing timing” based on the atomization index value, and the variable exhaust timing control device so that the actual exhaust valve closing timing coincides with the exhaust valve target closing timing. 36 is driven. However, due to the viscosity of the hydraulic oil used by the variable exhaust timing device 36, the output of the hydraulic pump, the frictional resistance between the members, and the like, the actual exhaust valve closing timing immediately matches the exhaust valve target closing timing. Instead, after the predetermined “response delay period” has elapsed, the exhaust valve target valve closing timing is reached. Therefore, during this response delay period, the fuel is not atomized to the expected extent. For this reason, during this response delay period, the amount of “atomized fuel” that is supplied to the combustion chamber 25 in the form of fine particles and can contribute to combustion becomes insufficient. Therefore, the first control device compensates for the shortage of the atomized fuel by increasing and correcting the base fuel amount TAUbase. That is, the first control device acquires the difference between the actual exhaust valve closing timing and the exhaust valve target closing timing as the valve opening / closing timing delay amount ΔTexc, and corrects the basic fuel amount TAUbase according to the difference.

  More specifically, the first control device corrects the base fuel amount TAUbase based on the coolant temperature THW and the valve opening / closing timing delay amount ΔTexc, and further corrects the corrected base fuel amount TAUbase based on the ethanol concentration Cetha. Thus, the final fuel injection amount TAU is calculated. Hereinafter, this point will be further described.

-Correction based on coolant temperature THW and valve opening / closing timing delay amount ΔTexc The first controller determines a first correction coefficient k1 using the first correction coefficient table Mapk1 (THW, ΔTexc) shown in FIG. The base fuel amount TAUbase is corrected by “multiplying” the base fuel amount TAUbase by one correction coefficient k1 to obtain “primary correction fuel injection amount TAUint (= k1 · TAUbase)”.

  The first control device stores the first correction coefficient table Mapk1 (THW, ΔTexc) shown in FIG. This first correction coefficient table Mapk1 (THW, ΔTexc) is a lookup table in which “the relationship between the cooling water temperature THW and the valve opening / closing timing delay amount ΔTexc and the first correction coefficient k1” is determined based on experimental data. (2-input 1-output type). The first control device applies the actual “cooling water temperature THW and valve opening / closing timing delay amount ΔTexc” obtained from the sensor output value and the like to the first correction coefficient table Mapk1 (THW, ΔTexc), thereby performing the first correction. The coefficient k1 is acquired.

  In FIG. 7, the solid line with the numerical value “1.00” is an “isoline” in which the first correction coefficient k1 takes “1.00” (maximum value). Similarly, a solid line to which a numerical value “α (= 1.05, 1.10, 1.15)” is attached is an isoline where the first correction coefficient k1 takes “α”. Further, in FIG. 7, the first correction coefficients k1 in the region on the right side of the solid line with the numerical value “1.00” are all “1.00”.

  Further, the value of the first correction coefficient k1 between “one isoline” and “another isoline adjacent to the one isoline” is the same as the value indicated by the one isoline. Is obtained by interpolation (for example, well-known linear interpolation) based on the value indicated by the isoline.

  According to the first correction coefficient table Mapk1 (THW, ΔTexc), the first correction coefficient k1 is determined so as to decrease toward 1.00 as the valve opening / closing timing delay amount ΔTexc decreases. That is, as the valve opening / closing timing delay amount ΔTexc is increased, the “insufficient amount of atomized fuel” increases, so that the base fuel amount TAUbase is corrected so as to increase as the valve opening / closing timing delay amount ΔTexc increases. Further, when the valve opening / closing timing delay amount ΔTexc is zero (that is, when the actual exhaust valve closing timing coincides with the exhaust valve target closing timing), the atomized fuel does not run short, so the first correction coefficient k1 Is maintained at “1.00” regardless of the cooling water temperature THW. As a result, the primary correction fuel injection amount TAUint (= k1 · TAUbase) becomes the same as the basic fuel amount TAUbase. In other words, at this time, the base fuel amount TAUbase is not corrected.

  According to the first correction coefficient table Mapk1 (THW, ΔTexc), the first correction coefficient k1 is determined so as to decrease toward 1.00 as the coolant temperature THW increases. That is, when the valve opening / closing timing delay amount ΔTexc is not “0”, the lower the cooling water temperature THW, the “insufficient amount of atomized fuel” becomes larger. Is done. Further, when the coolant temperature THW is higher than a predetermined value (that is, when the temperature of a member to which fuel such as an intake passage may adhere and the gas to be blown back is high), the valve opening / closing timing delay amount ΔTexc is Even if it is not “0”, the fuel is sufficiently atomized during the response delay period. Accordingly, the first correction coefficient k1 is maintained at “1.00”. As a result, the primary correction fuel injection amount TAUint is the same as the basic fuel amount TAUbase. Thus, the first correction coefficient k1 is set to a larger value as the “insufficient amount of atomized fuel” increases.

Correction Based on Ethanol Concentration Cetha Next, the first control device further corrects the primary correction fuel injection amount TAUint based on the ethanol concentration Cetha. That is, the first control apparatus determines the second correction coefficient k2 using the second correction coefficient table Mapk2 (Cetha, ΔTexc) shown in FIG. 8, and uses the second correction coefficient k2 as the primary correction fuel injection amount TAUint. By “multiplying”, the primary correction fuel injection amount TAUint is corrected to calculate “final fuel injection amount TAU (= k2 · TAUint)”.

  The first control device stores the second correction coefficient table Mapk2 (Cetha, ΔTexc) shown in FIG. This second correction coefficient table Mapk2 (Cetha, ΔTexc) is a lookup table in which “the relationship between the ethanol concentration Cetha and the valve opening / closing timing delay amount ΔTexc and the second correction coefficient k2” is determined based on experimental data. (2-input 1-output type). The first control device applies the actual “ethanol concentration Cetha and valve opening / closing timing delay amount ΔTexc” obtained from the sensor output value and the like to the second correction coefficient table Mapk2 (Cetha, ΔTexc) to perform the second correction. The coefficient k2 is acquired.

  In FIG. 8, the solid line shows the relationship between the ethanol concentration Cetha and the second correction coefficient k2 when the valve opening / closing timing delay amount ΔTexc is not zero (that is, during the response delay period). On the other hand, the broken line indicates the ethanol concentration Cetha and the second correction coefficient k2 when the valve opening / closing timing delay amount ΔTexc is zero (that is, when the actual exhaust valve closing timing and the exhaust valve target closing timing coincide). Shows the relationship.

  When the valve opening / closing timing delay amount ΔTexc is zero, there is no shortage of atomized fuel. Therefore, according to the second correction coefficient table Mapk2 (Cetha, ΔTexc), the second correction coefficient k2 is maintained at “1.00” as indicated by the “broken line” in FIG. As a result, the fuel injection amount TAU corrected based on the second correction coefficient k2 becomes the same as the primary correction fuel injection amount TAUint. In other words, at this time, the primary correction fuel injection amount TAUint is not corrected.

  Further, when the valve opening / closing timing delay amount ΔTexc is not zero, the shortage of atomized fuel increases as the ethanol concentration Cetha increases. Therefore, according to the second correction coefficient table Mapk2 (Cetha, ΔTexc), as shown by the “solid line” in FIG. 8, the second correction coefficient k2 is determined so as to increase as the ethanol concentration Cetha increases. When the ethanol concentration Cetha is zero (that is, when the fuel consists only of gasoline containing no ethanol), there is no shortage of atomized fuel. Therefore, in this case, according to the second correction coefficient table Mapk2 (Cetha, ΔTexc), the second correction coefficient k2 is set to “1.00”. At this time, the primary correction fuel injection amount TAUint is not corrected. As described above, the second correction coefficient k2 is set to a larger value as the “insufficient amount of atomized fuel” is larger, like the first correction coefficient k1.

  As described above, the first control device determines the base fuel amount TAUbase based on the first operating parameter. Then, the first control device sequentially multiplies the basic fuel amount TAUbase by the first correction coefficient k1 and the second correction coefficient k2 to calculate the final fuel injection amount TAU. In this way, the first control device corrects the fuel injection amount according to the valve opening / closing timing delay amount.

<Actual operation>
Hereinafter, the actual operation of the first control device will be described. The CPU 91 is configured to repeatedly execute each routine shown in the flowcharts in FIGS. 9 to 11 every elapse of a predetermined time. Hereinafter, “At this time, an operator of the engine 10 has performed an operation for starting the engine 10 (an ignition key switch (not shown) is rotated to a starting position, and the engine 10 is required to perform a cold start). The explanation is continued assuming “

  The CPU 91 executes a “valve timing control routine” shown by a flowchart in FIG. 9 every time a predetermined time elapses. By this routine, the CPU 71 determines the exhaust valve target closing timing Texc according to the fuel atomization index value Atmz, and the actual exhaust valve closing timing (actual exhaust valve closing timing Texcact) is determined as the exhaust valve target closing. The variable exhaust timing control device 36 is controlled so as to coincide with the valve timing Texc.

  Therefore, when the predetermined timing is reached, the CPU 91 starts processing from step 900 in FIG. 9 and proceeds to step 910 to determine whether or not the engine rotational speed NE is equal to or lower than the threshold rotational speed NEth. Here, the threshold rotational speed NEth may be “a value at which it can be determined that the engine 10 has not started (not rotated by combustion) when the engine rotational speed NE is equal to or lower than the threshold rotational speed NEth”. The threshold rotation speed NEth can be set to, for example, 500 rotations / minute.

  According to the above assumption, the current time is immediately after the engine 10 is requested to start cold, so that it is immediately after cranking is started by a starter (not shown). Therefore, the engine 10 has not been started yet. That is, the engine rotational speed NE is equal to or lower than the threshold rotational speed NEth. Accordingly, the CPU 91 determines “Yes” in step 910 and proceeds to step 920 to set the value of the engine start flag XES to “0”. The engine start flag XES indicates that the state of the engine 10 is before start when the value is “0”, and indicates that the state of the engine 10 is after start when the value is “1”. The value of the engine start flag XES is set to “0” in an initial routine that is executed when an ignition key switch (not shown) is changed from OFF to ON.

  Next, the CPU 91 proceeds to step 930, acquires the cooling water temperature THW based on the output value of the water temperature sensor 77, acquires the ethanol concentration Cetha based on the output value of the alcohol concentration sensor 84, and outputs the intake air temperature sensor 72. The intake air temperature THA is acquired based on the value. Then, the CPU 91 obtains the atomization index value Atmz at the present time by applying these acquired parameters to the atomization index value table MapAtmz (THW, Cetha, THA) described above.

  Further, the CPU 91 proceeds to step 940 to set the exhaust valve target valve closing timing table MapTexc (Atmz) to “Step 930” in the “relation between the atomization index value Atmz and the exhaust valve target valve closing timing Texc”. The exhaust valve target closing timing Texc is acquired by applying the atomization index value Atmz acquired in the above. In the exhaust valve target closing timing table MapTexc (Atmz), the exhaust valve target closing timing Texc is represented by an advance angle (° BTDC) with reference to the intake top dead center. Hereinafter, this step 940 will be described in more detail.

  As described above, the first control device fixes the intake valve opening timing to “a timing advanced by a predetermined angle slightly more than the intake top dead center” and sets the exhaust valve target closing timing Texc to “atomization”. By changing according to the index value, the atomization ability by the gas blown back into the intake passage is changed. At this time, as described above, as the exhaust valve target closing timing Texc is advanced from the intake top dead center toward the exhaust bottom dead center, the negative overlap period becomes longer. Can be increased.

  The smaller the fuel atomization index value Atmz is, the more difficult it is to atomize the fuel. Therefore, the first control device determines the exhaust valve target valve closing timing Texc so that the “atomization ability of blow-back gas” increases as the atomization index value Atmz decreases. On the other hand, when the atomization index value Atmz is sufficiently large, the fuel is appropriately atomized without promoting atomization by the blow-back gas. Therefore, when the atomization index value Atmz is larger than the predetermined value A1, the first control device determines the exhaust valve target valve closing timing Texc so that the blow-back gas is not substantially generated.

  Specifically, as shown in the exhaust valve target closing timing table MapTexc (Atmz) in step 940, the exhaust valve target closing timing Texc is equal to the atomization index when the atomization index value Atmz is smaller than the predetermined value A1. It is determined to increase as the value Atmz decreases. Further, the exhaust valve target closing timing Texc is determined to be zero when the atomization index value Atmz is equal to or greater than the predetermined value A1. Here, the predetermined value A1 is set to coincide with the maximum value A1 of the atomization index value Atmz shown in FIG. In this way, by making the predetermined value A1 coincide with the maximum value of the atomization index value Atmz, it is possible to perform control that “when the atomization index value Atmz reaches the maximum value, atomization promotion by the blow-back gas is not performed”. it can.

  After obtaining the atomization index value Atmz as described above, the CPU 91 proceeds to step 950 to control the variable exhaust timing control device 36 so that the actual exhaust valve closing timing Texcact coincides with the exhaust valve target closing timing Texc. To do. That is, the CPU 91 instructs the actuator 36a of the variable exhaust timing control device 36 to supply and discharge hydraulic oil. Thereafter, the CPU 91 proceeds to step 995 to end the present routine tentatively.

  Further, the CPU 91 determines the first correction coefficient k1 and the second correction coefficient k2 described above by executing the “correction coefficient determination routine” shown by the flowchart in FIG. 10 every time a predetermined time has elapsed. ing.

  Accordingly, when the predetermined timing is reached, the CPU 91 starts processing from step 1000 in FIG. 10 and proceeds to step 1010 to determine whether or not the value of the engine start flag XES is “0”. As described above, since the current value of the engine start flag XES is “0”, the CPU 91 determines “Yes” in step 1010 and proceeds to step 1020.

  In step 1020, the CPU 91 acquires the actual exhaust valve closing timing Texcact at the present time based on the output value from the exhaust cam position sensor 75, and the exhaust valve target closing timing acquired in step 940 of FIG. The “valve opening / closing timing delay amount ΔTexc”, which is the difference between Texc and the actual exhaust valve closing timing Texcact, is calculated. Here, the actual exhaust valve closing timing Texcact is represented by the advance angle (° BTDC) from the intake top dead center, as described above.

  Next, the CPU 91 proceeds to step 1030 to apply the current coolant temperature THW and the valve opening / closing timing delay amount ΔTexc acquired in step 1020 to the first correction coefficient table Mapk1 (THW, ΔTexc) described above. As a result, the first correction coefficient k1 is obtained.

  Next, the CPU 91 proceeds to step 1040, and obtains the second correction coefficient k2 by applying the fuel ethanol concentration Cetha and the valve opening / closing timing delay amount ΔTexc to the above-described second correction coefficient table Mapk2 (Cetha, ΔTexc). . Thereafter, the CPU 91 proceeds to step 1095 to end the present routine tentatively.

  Further, the CPU 91 performs the “fuel injection control routine” shown by the flowchart in FIG. 11 according to a predetermined crank angle before the intake top dead center (for example, 90 ° crank angle before intake top dead center) θf. It is executed repeatedly every time it matches. Thereby, the CPU 91 calculates the final fuel injection amount TAU and instructs the fuel injection. The cylinder whose crank angle coincides with the predetermined crank angle θf before the intake top dead center and reaches the intake stroke is hereinafter also referred to as “fuel injection cylinder”. The crank angle θf is preferably an angle at which the fuel injected from the crank angle θf collides with the gas blown back.

  Therefore, when the crank angle of an arbitrary cylinder reaches the predetermined crank angle θf, the CPU 91 starts processing from step 1100 in FIG. 11 and proceeds to step 1110. In step 1110, the CPU 91 acquires the intake air flow rate Ga based on the output value of the air flow meter 71, acquires the engine rotational speed NE based on the output value of the crank position sensor 76, and the cooling water temperature as described above. Obtain THW, intake air temperature THA, and ethanol concentration Cetha. Then, the CPU 91 applies the acquired parameters to the fuel injection amount table MapTAU (Ga, NE, THW, THA, Cetha) in which “the relationship between these parameters and the fuel injection amount TAU” is determined in advance. , Get the base fuel amount TAUbase.

  Next, the CPU 91 proceeds to step 1120 to determine whether or not the value of the engine start flag XES is “0”. As described above, since the current value of the engine start flag XES is “0”, the CPU 91 determines “Yes” in step 1120 and proceeds to step 1130.

  In step 1130, the CPU 91 adds the first correction coefficient k1 acquired in step 1030 of FIG. 10 and the second correction coefficient acquired in step 1040 of FIG. 10 to the fuel injection amount TAUbase acquired in step 1110. Multiply k2 to obtain the final fuel injection amount TAU. As a result, the fuel injection amount TAUbase is corrected according to the valve opening / closing timing delay amount ΔTexc and the ethanol concentration Cetha.

  Next, the CPU 91 proceeds to step 1140, and gives an instruction to the injector 39 to inject the fuel of the final fuel injection amount TAU from the injector 39 provided corresponding to the fuel injection cylinder. Thereafter, the CPU 91 proceeds to step 1195 to end the present routine tentatively.

  Here, it is assumed that the engine 10 controlled as described above has started at the present time. At this time, when the CPU 91 starts processing from step 900 in FIG. 9 at a predetermined timing, the CPU 91 proceeds to step 910. If the above assumption is followed, since the engine 10 is started at the present time, the engine rotational speed NE is larger than the threshold rotational speed NEth. Accordingly, the CPU 91 makes a “No” determination at step 910 to proceed to step 960 to set the value of the engine start flag XES to “1”. Next, the CPU 91 proceeds directly to step 995 to end the present routine tentatively. That is, at this time, the control of the variable intake timing control device 33 in steps 930 to 950 is not executed. However, in practice, the CPU 91 sets “a predetermined value unrelated to the atomization index value Atmz” as the exhaust valve target closing timing Texc, and the actual exhaust valve closing timing Texcact and the exhaust gas are processed by the same processing as step 950. The valve target closing timing Texc is made to coincide.

  Further, at this time, when the CPU 91 starts processing from step 1000 in FIG. 10 at a predetermined timing, the CPU 91 proceeds to step 1010. As described above, since the current value of the engine start flag XES is “1”, the CPU 91 makes a “No” determination at step 1010 to directly proceed to step 1095 to end the present routine tentatively. That is, at this time, acquisition of the correction coefficient in steps 1020 to 1040 is not executed.

  Further, at this time, when the CPU 91 starts processing from step 1100 in FIG. 11 at a predetermined timing, the CPU 91 proceeds to step 1120 through step 1110. Similarly to the above, since the current value of the engine start flag XES is “1”, the CPU 91 makes a “No” determination at step 1120 to proceed to step 1150. In step 1150, the CPU 91 stores the base fuel amount TAUbase in the final fuel injection amount TAU, and proceeds to step 1140. Then, the CPU 91 gives an instruction to the injector 39 to inject the fuel of the final fuel injection amount TAU from the injector 39 provided corresponding to the fuel injection cylinder. Thereafter, the CPU 91 proceeds to step 1195 to end the present routine tentatively. That is, at this time, the basic fuel amount TAUbase becomes the final fuel injection amount TAU.

  As described above, the first control device performs the target valve closing according to the fuel atomization index value Atmz during the period from when the engine 10 is requested to be cold-started to when the engine 10 is started. Determine the timing Texc. Further, the first control device controls the variable intake timing control device 33 so that the actual exhaust valve closing timing Texcact of the exhaust valve 35 coincides with the exhaust valve target closing timing Texc. In addition, the first control device performs fuel injection according to the valve opening / closing timing delay amount ΔTexc (difference between the exhaust valve target closing timing Texc and the actual exhaust valve closing timing Texcact), the ethanol concentration of the fuel Cetha, etc. Correct the amount (base fuel amount TAUbase). Then, after the engine 10 is started, the first control device stops the exhaust valve closing timing control and the fuel injection amount correction described above.

That is, the first control device
The present invention is applied to an internal combustion engine provided with fuel injection means (injector 39) for injecting fuel into an intake passage of the internal combustion engine 10.

The first control device
Fuel injection amount determining means for determining a basic fuel amount TAUbase, which is a basic amount of fuel injected from the fuel injection means 39, based on a first operating parameter representing the operating state of the engine 10 (step of FIG. 11) 1110)
The valve opening / closing timing which is at least one of the opening timing of the intake valve 32 of the engine 10 and the closing timing of the exhaust valve 35 of the engine 10 is set as the target valve opening / closing timing (in this example, the exhaust valve target closing timing). Valve timing control means (see the routine of FIG. 9) for controlling to match Texc),
Atomization index value acquisition for acquiring an atomization index value Atmz indicating the degree of ease of atomization of the fuel injected from the fuel injection means 39 based on a second operation parameter indicating the operating state of the engine 10 Means (step 930 in FIG. 9);
The target valve opening / closing timing (exhaust valve target closing timing Texc) is set such that at least a part of the gas existing in the combustion chamber 25 of the engine 10 is blown back from the combustion chamber 25 to the intake passage 41 at the start timing of the exhaust stroke. ) For determining the valve timing (step 940 in FIG. 9);
Is provided.

In the first control device,
The valve timing determining means includes
As the degree of ease of atomization of the fuel indicated by the atomization index value Atmz decreases, the fuel is atomized more in the intake passage 41 by the gas blown back to the intake passage 41. Determining the target valve opening / closing timing (exhaust valve target closing timing Texc) (step 940 in FIG. 9);
The fuel injection amount determining means includes
Based on the valve opening / closing timing delay amount ΔTexc representing the difference between the actual valve opening / closing timing (in this example, the actual exhaust valve closing timing Texcact) that is the actual timing of the valve opening / closing timing and the target valve opening / closing timing. The final fuel amount TAU actually injected from the fuel injection means 39 is determined by correcting the fuel amount TAUbase (Steps 1020 and 1030 in FIG. 10 and Steps in FIG. 11). 1130).

  In this way, the first control device corrects the fuel injection amount according to the valve opening / closing timing delay amount (increase correction), thereby avoiding the shortage of the amount of fuel contained in the air-fuel mixture during the response delay period. can do. Therefore, the first control device can cold start the engine 10 early. Furthermore, since the engine 10 is started at an early stage, the consumption of invalid fuel can be reduced.

(Second Embodiment)
Hereinafter, a control device (hereinafter also referred to as “second control device”) according to a second embodiment of the present invention will be described. The second control device is applied to an internal combustion engine similar to the engine 10 to which the first control device is applied. Therefore, a detailed description of the internal combustion engine to which the second control device is applied is omitted.

  Next, the operation of the second control device will be described. The second control device employs the “fuel atomization promotion control by the blow-back gas to the intake passage” similar to the first control device. In other words, the second control device first acquires the “atomization index value Atmz” indicating the degree of ease of atomization of fuel based on the operating state of the engine 10. Then, the second control device optimizes the atomization of the fuel by adjusting the negative overlap period OLn according to the atomization index value Atmz (that is, by changing the atomization ability). More specifically, like the first control device, the second control device fixes the intake valve opening timing to “a timing advanced by a slight predetermined angle from the intake top dead center” and “exhaust gas”. Change the valve closing timing. Further, the second control device acquires (calculates) the final fuel injection amount TAU by correcting the base fuel amount TAUbase in accordance with the “valve opening / closing timing delay amount ΔTexc”, similarly to the first control device.

  Further, the second control device, when there is a high possibility that the acquired (calculated) fuel injection amount TAU is excessively large (that is, when the valve opening / closing timing delay amount ΔTexc is excessively large), Stop. More specifically, the second control device determines that the “response delay threshold is a value of the valve opening / closing timing delay amount ΔTexc that can be determined that the fuel injection amount TAU increases excessively” based on the operating state of the engine 10. ΔTexcth ”is determined, and when the valve opening / closing timing delay amount ΔTexc is larger than the response delay threshold ΔTexcth, fuel injection is stopped. Thereby, it can avoid that the fuel increased excessively is injected. Therefore, the second control device can further reduce the amount of fuel consumed before the engine is cold started. Hereinafter, the “method for determining the response delay threshold ΔTexcth” employed by the second control device will be described before describing the actual operation of the second control device.

<Determination of response delay threshold>
The second control apparatus determines the response delay threshold value ΔTexcth using the response delay threshold value table MapΔTexcth (THW, Cetha) shown in FIG. More specifically, the second control device stores the response delay threshold value table MapΔTexcth (THW, Cetha) shown in FIG. This response delay threshold table MapΔTexcth (THW, Cetha) is a lookup table (two inputs and one output) that predetermines “relationship between cooling water temperature THW and ethanol concentration Cetha and response delay threshold ΔTexcth” based on experimental data. Type). The second control device acquires the response delay threshold value ΔTexcth by applying the actual “cooling water temperature THW and ethanol concentration Cetha” acquired from the sensor output value and the like to the response delay threshold value table MapΔTexcth (THW, Cetha). It is like that. In this response delay threshold value table MapΔTexcth (THW, Cetha), the response delay threshold value ΔTexcth is expressed as “angle difference (° CA) between exhaust valve target valve closing timing Texc and actual exhaust valve closing timing Texcact”. Has been.

  In FIG. 12, the solid line with the numerical value “100” indicates the cooling water temperature THW and the response delay threshold ΔTexcth when the ethanol concentration Cetha is 100% (that is, when the fuel is made of only ethanol that does not contain gasoline at all). The relationship is shown. Similarly, the solid line with the numerical value “β (= 80, 50, 0)” shows the relationship between the cooling water temperature THW and the response delay threshold ΔTexcth when the ethanol concentration Cetha is β%. Note that “the ethanol concentration Cetha is 0%” means “the fuel is composed only of gasoline containing no ethanol”.

  Furthermore, the relationship between the cooling water temperature THW and the response delay threshold ΔTexcth between the “solid line representing one ethanol concentration” and the “solid line representing another ethanol concentration adjacent to the one solid line” is It is obtained by interpolation (for example, well-known linear interpolation) based on those relationships indicated by solid line values and those relationships indicated by other solid lines.

  According to the response delay threshold value table MapΔTexcth (THW, Cetha), the response delay threshold value ΔTexcth is obtained so as to decrease as the coolant temperature THW decreases. This is because the amount of increase in the fuel injection amount becomes larger as the fuel is more difficult to be atomized, even if the valve opening / closing timing delay amount is the same. For the same reason, according to the response delay threshold value table MapΔTexcth (THW, Cetha), the response delay threshold value ΔTexcth is required to increase as the ethanol concentration Cetha decreases.

<Actual operation>
Hereinafter, the actual operation of the second control device will be described. The second control apparatus is different from the first control apparatus only in that the CPU 91 executes the process shown in the flowchart of FIG. 13 instead of the flowchart shown in FIG. Therefore, “the operator of the engine 10 has performed an operation for starting the engine 10 at the present time (the ignition key switch (not shown) is rotated to the starting position, and the engine 10 is cold-started. The description will be continued focusing on the differences between the first control device and the second control device.

  Similar to the first control device, the second control device repeatedly executes each routine shown in the flowcharts of FIGS. 9 and 10 every elapse of a predetermined time. That is, the second control device acquires the atomization index value Atmz based on the current coolant temperature THW, ethanol concentration Cetha, and intake air temperature THA. Then, the second control device acquires the exhaust valve target closing timing Texc based on the atomization index value Atmz, and is variable so that the exhaust valve target closing timing Texc and the actual exhaust valve closing timing Texcact coincide with each other. Control the intake timing control device. Further, the second control device corrects the fuel injection amount TAUbase based on the difference between the exhaust valve target closing timing Texc and the actual exhaust valve closing timing Texcact (valve opening / closing timing delay amount ΔTexc) and the ethanol concentration Cetha. The first correction coefficient k1 and the second correction coefficient k2 are obtained. If the above assumption is followed, the CPU 91 determines “Yes” in step 910 in FIG. 9, proceeds to step 920, and executes the processing in step 920. That is, at the present time, the value of the engine start flag XES is “0”.

  Further, the CPU 91 performs the “fuel injection control routine” shown by the flowchart in FIG. 13 according to a predetermined crank angle before the intake top dead center (for example, 90 ° crank angle before intake top dead center) θf. It is executed repeatedly every time it matches. Thereby, the CPU 91 calculates the final fuel injection amount TAU and instructs the fuel injection. The routine shown in FIG. 13 is different from the routine shown in FIG. 11 only in that steps 1310 and 1320 are added. Therefore, in FIG. 13, steps for performing the same processing as the steps shown in FIG. 11 are denoted by the same reference numerals as those given to such steps in FIG. 11. Detailed description of these steps will be omitted as appropriate.

  That is, when the crank angle of an arbitrary cylinder reaches the predetermined crank angle θf, the CPU 91 starts the process from step 1300 in FIG. 13 and proceeds to step 1110, where the current intake air flow rate Ga, engine rotational speed NE, cooling Acquire the water temperature THW, the intake air temperature THA, and the ethanol concentration Cetha, and obtain the basic fuel amount TAUbase by applying them to the fuel injection amount table MapTAU (Ga, NE, THW, THA, Cetha) described above. . Next, the CPU 91 proceeds to step 1120. As described above, since the current value of the engine start flag XES is “0”, the CPU 91 determines “Yes” in step 1120 and proceeds to step 1130.

  In step 1130, the CPU 91 corrects the basic fuel amount TAUbase with the first correction coefficient k1 and the second correction coefficient k2 to obtain the final fuel injection amount TAU. Next, the CPU 91 proceeds to step 1310.

  In step 1310, the CPU 91 obtains the current cooling water temperature THW and ethanol concentration Cetha, and obtains the response delay threshold ΔTexcth by applying them to the response delay threshold table MapΔTexcth (THW, Cetha) described above. To do. Next, the CPU 91 proceeds to step 1320 and determines whether or not the current valve opening / closing timing delay amount ΔTexc is smaller than the response delay threshold ΔTexcth acquired in step 1310.

  Here, the present time is immediately after the start of the above-described “control for matching the actual exhaust valve closing timing Texcact and the exhaust valve target closing timing Texc (see step 950 in FIG. 9)”. Assume that the delay amount ΔTexc is equal to or greater than the response delay threshold ΔTexcth. According to this assumption, the CPU 91 makes a “No” determination at step 1320 to directly proceed to step 1395 to end the present routine tentatively. That is, at this time, the fuel injection in step 1140 is not executed.

  Thereafter, it is assumed that the valve opening / closing timing delay amount ΔTexc decreases with time, and the valve opening / closing timing delay amount ΔTexc becomes smaller than the response delay threshold ΔTexcth. At this time, when the CPU 91 starts processing from step 1300 in FIG. 13, it proceeds to step 1320 through step 1110 to step 1130 and step 1310. According to the above assumption, the CPU 91 determines “Yes” in step 1320 and proceeds to step 1140. Then, an instruction is given to the injector 39 to inject the fuel of the final fuel injection amount TAU from the injector 39 provided corresponding to the fuel injection cylinder. Thereafter, the CPU 91 proceeds to step 1395 to end the present routine tentatively.

  As described above, the second control device, like the first control device, sets the fuel atomization index value Atmz during the period from when the engine 10 is requested to cold start until the engine 10 starts. Accordingly, the exhaust valve target closing timing Texc is determined. Then, the second control device controls the variable intake timing control device 33 so that the actual exhaust valve closing timing Texcact of the exhaust valve 35 coincides with the exhaust valve target closing timing Texc. Further, the second control device determines the fuel injection amount (the difference between the exhaust valve opening / closing timing delay ΔTexc (difference between the exhaust valve target closing timing Texc and the actual exhaust valve closing timing Texcact)) and the fuel ethanol concentration Cetha ( Base fuel amount TAUbase) is corrected. In addition, the second control device executes fuel injection only when the valve opening / closing timing delay amount ΔTexc is smaller than a predetermined response delay threshold value ΔTexcth.

That is, the second control device
In addition to the configuration of the first control device,
When the valve opening / closing timing delay amount ΔTexc is equal to or greater than a predetermined response delay threshold value ΔTexcth (when it is determined “No” in step 1320 of FIG. 13), the fuel injection means 39 indicates that fuel is injected. Fuel injection stopping means for stopping (step 1320 in FIG. 13) is provided.

Furthermore, this fuel injection stopping means
The response delay threshold value ΔTexcth is determined so that the response delay threshold value ΔTexcth becomes smaller as “the cooling water temperature THW of the engine 10 is lower” or “the alcohol content ratio Cetha in the fuel is higher”. (See the response delay threshold table MapΔTexcth (THW, Cetha) in FIG. 12 and step 1310 in FIG. 13).

  Thereby, since it is possible to avoid the fuel injection amount from being corrected to increase excessively, the amount of fuel consumed before the engine is cold-started can be further reduced.

  The second control device acquires the response delay threshold ΔTexcth based on the cooling water temperature THW and the ethanol concentration Cetha. However, the control device of the present invention determines the response delay threshold ΔTexcth so that the response delay threshold ΔTexcth decreases as the degree of ease of atomization of the fuel indicated by the atomization index value Atmz decreases. It may be configured as follows. Further, the response delay threshold ΔTexcth may be a constant value. Further, the second control device may be configured to correct the response delay threshold value ΔTexcth determined as described above with a correction coefficient corresponding to an engine operating parameter (for example, intake air temperature, fuel temperature, etc.). .

(Third control device)
Hereinafter, a control device according to a third embodiment of the present invention (hereinafter also referred to as “third control device”) will be described. The third control device is applied to the same engine as the engine 10 to which the first control device is applied. Therefore, detailed description of the engine to which the third control device is applied is omitted.

  Next, the operation of the third control device will be described. First, the third control device acquires the “atomization index value Atmz” representing the degree of ease of atomization of the fuel based on the operating state of the engine 10 as in the first control device. Then, the third control device determines a “fuel temperature threshold value Tfuelth” that is “a lower limit value of a fuel temperature range in which fuel injection can be performed” based on the atomization index value Atmz. The fuel temperature threshold value Tfuelth is determined so as to increase as the “degree of ease of atomization of fuel” indicated by the atomization index value Atmz decreases (that is, the degree of difficulty in atomization of fuel).

  When the actual fuel temperature Tfuel is lower than the fuel temperature threshold value Tfuelth, the third control device “stops” the fuel injection and “heats” the fuel. Then, the third control device executes fuel injection after the fuel temperature Tfuel rises to the fuel temperature threshold value Tfuelth by this heating. As a result, even when a fuel containing a fuel component that is difficult to atomize in a low-temperature environment is used, fuel atomization can be optimized by heating the fuel and raising its temperature. 10 can be quickly cold started. Therefore, the third control device can improve the starting performance of the engine 10.

<Actual operation>
Hereinafter, the actual operation of the third control device will be described. The CPU 91 is configured to repeatedly execute each routine shown in the flowcharts of FIGS. 14 and 15 every elapse of a predetermined time. Hereinafter, “At this time, an operator of the engine 10 has performed an operation for starting the engine 10 (an ignition key switch (not shown) is rotated to a starting position, and the engine 10 is required to perform a cold start). The explanation is continued assuming “

  The CPU 91 executes a “fuel heating control routine” shown by a flowchart in FIG. 14 every time a predetermined time elapses. The CPU 71 determines whether or not the fuel needs to be heated by this routine, and executes the heating of the fuel when it is determined that the fuel needs to be heated. The routine shown in FIG. 14 shows the point of determining whether or not the engine 10 is started based on the engine rotational speed NE and the point of determining the atomization index value Atmz based on the operating state of the engine. Processing similar to 9 is performed. Therefore, in FIG. 14, steps for performing the same processing as the steps shown in FIG. 9 are denoted by the same reference numerals as those given to such steps in FIG. 9. Detailed description of these steps will be omitted as appropriate.

  Therefore, when the predetermined timing is reached, the CPU 91 starts processing from step 1400 in FIG. 14 and proceeds to step 910. According to the above assumption, the current time is immediately after the engine 10 is requested to start cold, so that it is immediately after cranking is started by a starter (not shown). Therefore, the engine 10 has not been started yet. That is, the engine rotational speed NE is equal to or lower than the threshold rotational speed NEth. Therefore, the CPU 91 determines “Yes” in step 910 and proceeds to step 920 to set the value of the engine start flag XES to “0”.

  Next, the CPU 91 proceeds to step 930 to apply the cooling water temperature THW and the ethanol concentration Cetha to the above-described atomization index value table MapAtmz (THW, Cetha, THA), thereby acquiring the atomization index value Atmz at the present time. .

  Then, the CPU 91 proceeds to step 1420, and the atomization index value Atmz acquired in step 930 in the fuel temperature threshold value table MapTfuelth (Atmz) in which “a relationship between the atomization index value Atmz and the fuel temperature threshold value Tfuelth” is determined in advance. To obtain the fuel temperature threshold value Tfuelth. Hereinafter, this step 1420 will be described in more detail.

  As described above, the third control device optimizes atomization of the fuel by heating the fuel. Therefore, the third control device determines the fuel temperature threshold value Tfuelth so that the fuel is heated to a higher temperature as the atomization index value Atmz is smaller (that is, the fuel is more difficult to atomize). Specifically, as shown in the fuel temperature threshold value table MapTfuelth (Atmz) in step 1420, the fuel temperature threshold value Tfuelth is determined so as to increase as the atomization index value Atmz decreases.

  After acquiring the fuel temperature threshold value Tfuelth as described above, the CPU 91 proceeds to step 1425 to determine whether or not the actual fuel temperature Tfuel at the present time is smaller than the fuel temperature threshold value Tfuelth acquired in step 1420. . The actual fuel temperature Tfuel is acquired based on an output value of a fuel temperature sensor (not shown) provided in the fuel supply pipe 62. Here, it is assumed that the actual fuel temperature Tfuel is smaller than the fuel temperature threshold value Tfuelth at the present time. According to this assumption, the CPU 91 makes a “Yes” determination at step 1425 to proceed to step 1430 to execute fuel heating. That is, the CPU 91 instructs the fuel heating device 63 to heat the fuel.

  Next, the CPU 91 proceeds to step 1435 to set the value of the fuel heating flag XFH to “1”. The fuel heating flag XFH indicates that the fuel is being heated when the value is “1”, and indicates that the fuel is not being heated when the value is “0”. Note that the value of the fuel heating flag XFH is set to “0” in the initial routine. Thereafter, the CPU 91 proceeds to step 1495 to end the present routine tentatively.

  Further, the CPU 91 performs the “fuel injection control routine” shown by the flowchart in FIG. 15 according to a predetermined crank angle before the intake top dead center (for example, 90 ° crank angle before the intake top dead center) θf. It is executed repeatedly every time it matches. As a result, the CPU 91 calculates the fuel injection amount TAU and instructs fuel injection.

  Therefore, when the crank angle of an arbitrary cylinder reaches the predetermined crank angle θf, the CPU 91 starts processing from step 1500 in FIG. 15 and proceeds to step 1510. In step 1510, the CPU 91 obtains the intake air flow rate Ga, the engine rotational speed NE, the cooling water temperature THW, the intake water temperature THA, and the ethanol concentration Cetha acquired in the same manner as in the first control device, and the fuel injection amount TAU for them. The fuel injection amount TAU is acquired by applying the relationship to a predetermined fuel injection amount table MapTAU (Ga, NE, THW, THA, Cetha).

  Next, the CPU 91 proceeds to step 1520 to determine whether or not the value of the engine start flag XES is “0”. As described above, since the current value of the engine start flag XES is “0”, the CPU 91 determines “Yes” in step 1520 and proceeds to step 1530.

  In step 1530, the CPU 91 determines whether or not the value of the fuel heating flag XFH is “0”. As described above, since the current value of the fuel heating flag XFH is “1”, the CPU 91 makes a “No” determination at step 1530 to directly proceed to step 1595 to end the present routine tentatively. That is, at this time, since the process of step 1540 is not executed, fuel is not injected.

  Here, it is assumed that the heating of the fuel is continued and the actual fuel temperature Tfuel becomes equal to or higher than the fuel temperature threshold value Tfuelth as time elapses. At this time, when the CPU 91 starts processing from step 1400 in FIG. 14, it proceeds to step 1425 through step 910 to step 930 and step 1420. According to the above assumption, the CPU 91 makes a “No” determination at step 1425 to proceed to step 1440 to stop heating the fuel. That is, the CPU 91 instructs the fuel heating device 63 to stop heating the fuel. Next, the CPU 91 proceeds to step 1445 to set the value of the fuel heating flag XFH to “0”. Thereafter, the CPU 91 proceeds to step 1495 to end the present routine tentatively.

  At this time, when the CPU 91 starts processing from step 1500 in FIG. 15, it proceeds to step 1530 through step 1510 and step 1520. As described above, the current value of the fuel heating flag XFH is “0”, so the CPU 91 determines “Yes” in step 1530 and proceeds to step 1540. Next, in step 1540, the CPU 91 gives an instruction to the injector 39 to inject fuel of the fuel injection amount TAU from the injector 39 provided corresponding to the fuel injection cylinder. In response to this instruction, fuel injection is started. Thereafter, the CPU 91 proceeds to step 1595 to end the present routine tentatively.

  Here, it is assumed that the fuel is injected as described above and the engine 10 is started. At this time, the CPU 91 starts processing from step 1400 in FIG. 14 at a predetermined timing and proceeds to step 910. If the above assumption is followed, since the engine 10 is started at the present time, the engine rotational speed NE is larger than the threshold rotational speed NEth. Accordingly, the CPU 91 makes a “No” determination at step 910 to proceed to step 960 to set the value of the engine start flag XES to “1”. Next, the CPU 91 proceeds directly to step 1495 to end the present routine tentatively. That is, at this time, the processing shown in Steps 1415 to 1430 is not executed, so that the state where the heating of the fuel is stopped is maintained.

  Further, at this time, when the CPU 91 starts processing from step 1500 in FIG. 15 at a predetermined timing, the CPU 91 proceeds to step 1520 through step 1510. As described above, since the current value of the engine start flag XES is “1”, the CPU 91 makes a “No” determination at step 1520 and proceeds to step 1540 to supply fuel of the fuel injection amount TAU. The injector 39 is instructed to inject from the injector 39 provided corresponding to the injection cylinder. Thereafter, the CPU 91 proceeds to step 1595 to end the present routine tentatively. That is, at this time, the processing shown in step 1530 is not executed, so that fuel of the fuel injection amount TAU is necessarily injected.

  As described above, the third control device sets the fuel temperature threshold value Tfuelth according to the fuel atomization index value Atmz during the period from when the engine 10 is requested to be cold-started to when the engine 10 is started. decide. When the actual fuel temperature Tfuel is lower than the fuel temperature threshold value Tfuelth, the third control device heats the fuel and stops fuel injection. Further, when the fuel temperature Tfuel becomes equal to or higher than the fuel temperature threshold value Tfuelth by this heating, the third control device stops heating the fuel and starts fuel injection. In addition, the third control device does not perform the above-described heating of the fuel after the engine 10 is started.

That is, the third control device
The present invention is applied to an internal combustion engine provided with fuel injection means (injector 39) for injecting fuel into an intake passage of the internal combustion engine 10.

The third control device
The fuel injection amount TAU, which is the amount of fuel injected from the fuel injection means 39, is determined based on a third operating parameter (similar to the first operating parameter) representing the operating state of the engine 10. Amount determining means (step 1510 in FIG. 15);
Fuel temperature threshold value acquisition means (step 1420 in FIG. 14) for acquiring a fuel temperature threshold value Tfuelth, which is a threshold value of the temperature of fuel injected from the fuel injection means 39, based on the fourth operating parameter representing the operating state of the engine 10. )When,
Fuel temperature adjusting means (step 1425, step 1430 and step 1440 in FIG. 14) for adjusting the temperature of the fuel;
Is provided.

In the third control device,
The fuel temperature adjusting means includes
When the actual fuel temperature Tfuel is smaller than the fuel temperature threshold value Tfuelth (when it is determined “Yes” in step 1425 in FIG. 14), the fuel is heated (step 1430 in FIG. 14),
The fuel injection means includes
When the actual fuel temperature Tfuel is smaller than the fuel temperature threshold value Tfuelth (when “Yes” is determined in Step 1425 of FIG. 14 and the value of the fuel heating flag XFH is set to “1” in Step 1435) ), The fuel injection is stopped (see step 1530 and step 1540 in FIG. 15).

  As described above, when the fuel temperature is lower than the predetermined fuel temperature threshold, the third control device stops the fuel injection and heats the fuel. Thereby, since the temperature of the fuel rises, atomization of the fuel is optimized. Furthermore, since the fuel injection is stopped and the fuel is heated, the temperature of the fuel can be quickly raised. Therefore, the engine can be cold started early. As a result, the consumption of invalid fuel can be reduced.

  As described above, the third control device heats the fuel by the fuel heating device 63 provided on the fuel supply pipe 62. However, the control device of the present invention may be configured to heat the fuel by heating the fuel injection device (injector 39).

  The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, the variable intake timing control device 33 may be configured to be able to continuously change the lift amount of the intake valve 32 in addition to the opening / closing timing of the intake valve 32. Similarly, the variable exhaust timing control device 36 may be configured to continuously change the lift amount of the exhaust valve 35 in addition to the opening / closing timing of the exhaust valve 35.

  Further, the control device of the present invention determines the target air-fuel ratio afr from, for example, the cooling water temperature THW and the intake air temperature THA, and the in-cylinder intake air amount Mc (one cylinder once) from the intake air flow rate Ga and the engine rotational speed NE. The amount of intake air in the intake stroke of the engine is determined, and the in-cylinder intake air amount Mc is divided by the target air-fuel ratio afr to obtain a basic fuel injection amount (basic fuel amount in the first control device and the second control device) The TAUbase and the fuel injection amount TAU) in the third control device may be obtained. In this case, since the value of the theoretical air-fuel ratio changes depending on the ethanol concentration Cetha, the basic fuel injection amount may be corrected according to the ethanol concentration Cetha.

  In addition, each control device described above determines the fuel injection amount based on predetermined operating parameters (that is, intake air flow rate Ga, engine speed NE, cooling water temperature THW, intake air temperature THA, and ethanol concentration Cetha). is doing. However, the control device of the present invention obtains the fuel injection amount based on “the operation parameter, the throttle valve opening TA acquired based on the output value of the throttle position sensor 73, and the output value of the accelerator opening sensor 81. The accelerator pedal opening Accp, the shift position P acquired based on the output value of the vehicle speed SPD shift position sensor 83 acquired based on the output value of the vehicle speed sensor 82, and the engine load (for example, for a certain cylinder) A parameter group consisting of: cylinder intake air amount Mc, throttle valve opening TA, accelerator pedal operation amount Accp, filling rate KL, etc.) that is the amount of air taken into the cylinder in one intake stroke It may be configured to determine based on one or more of the following.

  Further, each control device described above fixes the opening timing of the intake valve to “a timing advanced by a slight angle from the intake top dead center”, and also sets the target valve closing timing of the exhaust valve to the atomization index. Determined based on the value. However, the control device of the present invention may be configured to fix the closing timing of the exhaust valve at a predetermined timing and determine the opening timing of the intake valve based on the atomization index value Atmz. Furthermore, the control device of the present invention may be configured to determine both the “target valve opening timing of the intake valve” and the “target valve closing timing of the exhaust valve” according to the atomization index value. When either one of “target intake valve opening timing” or “exhaust valve target valve closing timing” is fixed, the fixed value is advanced by a predetermined angle slightly smaller than the intake top dead center. For example, it may be a value within a range from “intake top dead center −10 °” to “intake top dead center + 10 °”.

  Further, as described above, the control device according to the present invention has the length of the positive overlap period and the time when the positive overlap period exists, and the length of the negative overlap period and the negative overlap period. It may be configured to change the atomization ability by the blown-back gas by controlling any of the existing periods.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 21 ... Cylinder, 22 ... Piston, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 33 ... Variable intake timing control device, 34 ... Exhaust port, 35 ... Exhaust valve, 36 ... Variable exhaust Timing control device 37 ... Spark plug 39 ... Injector 41 ... Intake pipe 51 ... Exhaust manifold 61 ... Fuel tank 62 ... Fuel supply pipe 63 ... Fuel heating device 71 ... Air flow meter 72 ... Intake temperature sensor 76 ... Crank position sensor, 77 ... Water temperature sensor, 84 ... Alcohol concentration sensor, 90 ... Electric control device, 91 ... CPU.

Claims (4)

Applied to an internal combustion engine having fuel injection means for injecting fuel into an intake passage of the internal combustion engine;
Fuel injection amount determining means for determining a basic fuel amount, which is a basic amount of fuel injected from the fuel injection means, based on a first operating parameter representing an operating state of the engine;
Valve timing control means for controlling the valve opening / closing timing which is at least one of the opening timing of the intake valve of the engine and the closing timing of the exhaust valve of the engine so as to coincide with the target valve opening / closing timing;
Atomization index value acquisition means for acquiring an atomization index value representing a degree of ease of atomization of fuel injected from the fuel injection means based on a second operation parameter representing an operating state of the engine;
Valve timing determining means for determining the target valve opening / closing timing so that at least a part of the gas existing in the combustion chamber of the engine is blown back from the combustion chamber to the intake passage at the start timing of the exhaust stroke;
In a control device for an internal combustion engine comprising:
The valve timing determining means includes
The target valve is configured such that as the degree of ease of atomization of the fuel indicated by the atomization index value becomes smaller, the fuel is atomized more in the intake passage by the gas blown back into the intake passage. Decide opening and closing time,
The fuel injection amount determining means includes
The fuel injection means actually injects the fuel by correcting the basic fuel amount based on the valve opening / closing timing delay amount representing the difference between the actual valve opening / closing timing and the target valve opening / closing timing, which is the actual timing of the valve opening / closing timing. Configured to determine the amount of final fuel that will be
Control device for internal combustion engine. A control device for an internal combustion engine according to claim 1,
Control means for an internal combustion engine comprising fuel injection stop means for stopping fuel injection from the fuel injection means when the valve opening / closing timing delay amount is equal to or greater than a predetermined response delay threshold. The control apparatus for an internal combustion engine according to claim 2,
The fuel injection stopping means is
Control means for an internal combustion engine, including response delay threshold value determining means for determining the response delay threshold value such that the response delay threshold value decreases as the cooling water temperature of the engine decreases or the content ratio of alcohol contained in the fuel increases. The control apparatus for an internal combustion engine according to claim 2,
The fuel injection stopping means is
A control apparatus for an internal combustion engine, including response delay threshold value determining means for determining the response delay threshold value so that the response delay threshold value decreases as the degree of ease of atomization of the fuel indicated by the atomization index value decreases. .

Images