JP2017166388A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress unevenness in balanced attachment amounts in intake passages, when two fuel injection valves different in fuel injection timing are respectively disposed one by one in two intake passages opened to one cylinder.SOLUTION: A fuel injection control device making a first fuel injection valve and a second fuel injection valve implement fuel injection in an internal combustion engine in which a first intake passage and a second intake passage are disposed in each cylinder, the first fuel injection valve is disposed in the first intake passage, and the second fuel injection valve is disposed in the second intake passage, sets injection pulse signals to the first fuel injection valve and the second fuel injection valve so as to alternately switch two fuel injection timings by every prescribed number of combustion cycles while having phase difference in two injection timings of the injection timing of the fuel injection by the first fuel injection valve and the injection timing of the fuel injection by the second fuel injection valve in each combustion cycle.SELECTED DRAWING: Figure 3

Description

  The present invention provides an internal combustion engine that includes a first intake passage and a second intake passage for each cylinder, a first fuel injection valve is disposed in the first intake passage, and a second fuel injection valve is disposed in the second intake passage. On the other hand, the present invention relates to a fuel injection control device for injecting fuel from a first fuel injection valve and a second fuel injection valve.

  For an internal combustion engine that includes a first intake passage and a second intake passage for each cylinder, the first fuel injection valve is disposed in the first intake passage, and the second fuel injection valve is disposed in the second intake passage. As a fuel injection control device for injecting fuel from a fuel injection valve and a second fuel injection valve, there are two injection timings: an injection timing at which the first fuel injection valve injects and an injection timing at which the second fuel injection valve injects. What provided the phase difference is known (for example, refer patent document 1).

JP 2012-229653 A

  By the way, for example, one of the injection timing of the first fuel injection valve and the injection timing of the second fuel injection valve is synchronized with the intake stroke to promote the mixing of air and fuel. It is conceivable that the intake air amount in each intake passage differs depending on the injection timing of the second fuel injection valve. As the intake air amount increases, the amount of adhering fuel that adheres to the inner wall of the intake passage without increasing the amount of fuel injected due to the inertia of the intake air flow at the curved portion of the intake passage increases.

  Therefore, if the injection timing of the first fuel injection valve and the injection timing of the second fuel injection valve are fixed with a phase difference between them, in each intake passage having a large intake air amount at the injection timing, each combustion cycle Since new adhering fuel is generated and the equilibrium adhering amount on the inner wall of the intake passage is increased, fluctuations in the air-fuel ratio during transient operation increase, which may adversely affect exhaust emission and fuel efficiency.

  The present invention has been made in view of the above problems, and includes the injection timing of the first fuel injection valve disposed in the first intake passage and the injection timing of the second fuel injection valve disposed in the second intake passage. It is an object of the present invention to provide a fuel injection control device that suppresses a deviation in the amount of equilibrium adhesion between a first intake passage and a second intake passage when a phase difference is provided.

  Therefore, the fuel injection control device according to the present invention includes a first intake passage and a second intake passage for each cylinder, a first fuel injection valve is disposed in the first intake passage, and a second intake passage is provided in the second intake passage. Injecting fuel into an internal combustion engine having a fuel injection valve by causing the first fuel injection valve and the second fuel injection valve to inject fuel, and the first fuel injection valve injects fuel in each combustion cycle The two injection timings are alternately switched every predetermined number of combustion cycles while providing a phase difference between the two injection timings of the timing and the injection timing at which the second fuel injection valve injects the fuel.

  According to the fuel injection control device of the present invention, there is a phase difference between the injection timing of the first fuel injection valve arranged in the first intake passage and the injection timing of the second fuel injection valve arranged in the second intake passage. Even if this is done, it is possible to suppress a bias in the amount of equilibrium adhesion between the first intake passage and the second intake passage.

1 is a system configuration diagram of an internal combustion engine according to an embodiment of the present invention. It is a schematic diagram which shows the fuel injection in the intake port of the embodiment, (a) is a primary injection, (b) is a secondary injection. It is a time chart of the injection pulse signal which shows injection timing exchange of the embodiment. It is a flowchart which shows the setting process of the injection pulse signal in the embodiment. It is a time chart of the injection pulse signal which shows the setting of the fuel sharing rate in the embodiment, (a) is a low load low rotation speed side, (b) is a high load high rotation speed side. It is a time chart of the injection pulse signal which shows the setting of the injection timing in the primary injection of the embodiment, (a) is a low load low rotation speed side, (b) is a high load high rotation speed side. It is a time chart of the injection pulse signal which shows the setting of the injection timing in the primary injection of the embodiment, (a) is a low load low rotation speed side, (b) is a high load high rotation speed side. It is a time chart of the injection pulse signal which shows the setting of the injection timing in the secondary injection of the embodiment. It is a time chart of the injection pulse signal which shows the injection timing replacement timing in the embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a system configuration diagram of an internal combustion engine (four-cycle engine) in the embodiment.

In the internal combustion engine 10, the downstream side of the intake pipe 12 branches into a first intake port 14 and a second intake port 16, and the downstream ends of the first intake port 14 and the second intake port 16 are independently connected to the cylinder 18. Open. The intake pipe 12 and the first intake port 14 form a first intake passage, and the intake pipe 12 and the second intake port 16 form a second intake passage.
An intake valve 20 is interposed in the portion where the first intake port 14 and the second intake port 16 open to the cylinder 18, and opens and closes the open portions of the intake ports 14 and 16.

  On the other hand, the upstream ends of two independent first exhaust ports 22 and second exhaust ports 24 open to the cylinder 18, and the first exhaust port 22 and the second exhaust port 24 join downstream to form an exhaust pipe (not shown). ). Opening portions of the first exhaust port 22 and the second exhaust port 24 are opened and closed by an exhaust valve 26.

  A first fuel injection valve 28 is disposed on the first intake port 14 side (or the first intake port 14) of the intake pipe 12, and on the second intake port 16 side (or the second intake port 16) of the intake pipe 12. The second fuel injection valve 30 is disposed, and the first fuel injection valve 28 and the second fuel injection valve 30 are umbrellas of the intake valves 20 interposed with respect to the first intake port 14 and the second intake port 16, respectively. Fuel is injected toward the portion 20a.

  The first fuel injection valve 28 and the second fuel injection valve 30 are electromagnetic fuel injection valves that are opened by lifting a valve body by a magnetic attractive force of an electromagnetic coil. In this manner, since the shared injection amount of one fuel injection valve can be reduced by using the two fuel injection valves 28 and 30, an injection valve excellent in atomization with small injection holes can be used.

  The fuel (gasoline) in the fuel tank 32 is pumped by the fuel pump 34 to the first fuel injection valve 28 and the second fuel injection valve 30, and the fuel supply pressure is discharged from the fuel pump 34. The target pressure is controlled by controlling the amount.

  The fuel injected from the first fuel injection valve 28 and the second fuel injection valve 30 is sucked into the combustion chamber 36 through the intake valve 20. The fuel sucked into the combustion chamber 36 is ignited and burned by spark ignition of the spark plug 38, and the combustion exhaust is discharged from the first exhaust port 22 and the second exhaust port 24 through the exhaust valve 26.

  An engine control unit (hereinafter referred to as “ECU”) 40 has a built-in microcomputer and inputs output signals from various sensors for detecting the operating conditions of the internal combustion engine 10 to control the fuel pump 34 and the spark plug 38. In addition to the control device, the fuel injection control device is configured to cause the first fuel injection valve 28 and the second fuel injection valve 30 to inject fuel.

  The various sensors include a crank angle sensor 42 that outputs a rotation pulse signal POS synchronized with the rotation of the crankshaft of the internal combustion engine 10, an airflow sensor 44 that outputs a flow rate detection signal Q indicating the intake air amount of the internal combustion engine 10, and an internal combustion engine. A water temperature sensor 46 for outputting a temperature detection signal TW indicating ten cooling water temperatures is provided.

  The first fuel injection valve 28 and the second fuel injection valve 30 open at an injection timing and an injection period defined by an injection pulse signal (instruction signal) output from the ECU 40, and inject an amount of fuel proportional to the injection period. To do.

  Here, the ECU 40 injects fuel in each combustion cycle when the first fuel injection valve 28 injects fuel (including an injection start time and an injection end time; the same applies hereinafter) and the second fuel injection valve 30 injects fuel. The injection pulse signal is set so as to provide a phase difference between two injection timings with respect to the injection timing. In each combustion cycle, the previous injection is referred to as primary injection, and the subsequent injection is referred to as secondary injection.

  In the primary injection, the ECU 40 starts the fuel injection in the exhaust stroke by one fuel injection valve (for example, the first fuel injection valve 28) in order to promote the vaporization of the injected fuel, and the injection in the exhaust stroke. The injection pulse signal of one fuel control valve is set so that the period is longer than the injection period during the intake stroke or so that fuel is injected only during the exhaust stroke.

  In addition, in the secondary injection, the ECU 40 promotes the mixing of air and fuel for the purpose of reducing unburned hydrocarbons and improving fuel efficiency by increasing the combustion speed. The fuel injection valve 30) starts injection after one fuel injection valve so that the injection period of the other fuel injection valve during the intake stroke is longer than the injection period of one fuel injection valve during the intake stroke. In addition, the injection pulse signal of the other fuel control valve is set. For example, in the secondary injection, fuel is injected in synchronization with the air intake period in the intake stroke.

When the ECU 40 sets the injection pulse signal in this way, as shown in FIG. 2A, in the first intake port 14 where the primary injection is performed, the fuel injected by the first fuel injection valve 28 in the exhaust stroke is shown. A part of the fuel adheres to the umbrella portion 20a of the intake valve 20 without being vaporized. However, by absorbing the residual heat of combustion in the immediately preceding expansion stroke, vaporization of the attached fuel is promoted.
Further, in the exhaust stroke, the residual heat of combustion is larger than that in the intake stroke, and since the intake flow is not generated, the temperature of the inner wall of the first intake port 14 is not easily lowered. Fuel is also easier to vaporize than the intake stroke.

  On the other hand, as shown in FIG. 2 (b), in the second intake port 16 where the secondary injection is performed, a part of the fuel injected by the second fuel injection valve 30 in the intake stroke is not vaporized, and the intake flow The inertia of the second intake port 16 tends to adhere to the inner wall of the curved portion 16a of the second intake port 16, but the inner wall of the port is cooled by the intake air flow, and the residual heat of combustion is smaller than that of the exhaust stroke. Is less likely to vaporize than the exhaust stroke.

Therefore, the amount of fuel adhering to each intake port 14, 16 in one combustion cycle is such that the injection period in the intake stroke is the same if the fuel injection amounts of the first fuel injection valve 28 and the second fuel injection valve 30 are the same. The second fuel injection valve 30 for performing the secondary injection having a relatively long injection period in the intake stroke is disposed rather than the first intake port 14 in which the first fuel injection valve 28 for performing the relatively short primary injection is disposed. The second intake port 16 is larger.
When the fuel injection valve that performs the primary injection is fixed to the first fuel injection valve 28 and the fuel injection valve that performs the secondary injection is fixed to the second fuel injection valve 30, the curved portion of the second intake port 16 In 16a, new adhering fuel is generated one after another in each combustion cycle, and the amount of equilibrium adhering increases. If the equilibrium adhesion amount increases, the air-fuel ratio fluctuation during transient operation increases, which may adversely affect exhaust emission and fuel efficiency.

Therefore, as shown in FIG. 3, in the ECU 40, the injection timing (start timing t _1s and end timing t _1e ) at which the first fuel injection valve 28 injects fuel in each combustion cycle and the second fuel injection valve 30 are the fuel. The operating state of the internal combustion engine 10 while providing a phase difference (t _2s -t _1s and t _2e -t _1e ) between two injection timings of the injection timing (start timing t _2s and end timing t _2e ) Accordingly, the injection pulse signal is set so that the two injection timings are alternately switched every predetermined number of combustion cycles (for example, every cycle). In other words, the ECU 40 causes the first fuel injection valve 28 and the second fuel injection valve 30 to perform injections in different injection modes (primary injection or secondary injection) in each combustion cycle, thereby operating the internal combustion engine 10. Depending on the state, the injection pulse signal is set so that the injection mode of the first fuel injection valve 28 and the injection mode of the second fuel injection valve 30 are alternately switched every predetermined number of combustion cycles.

  Thus, the injection period in the intake stroke is performed by alternately switching the primary injection and the secondary injection every predetermined number of combustion cycles between the first fuel injection valve 28 and the second fuel injection valve 30. Even if a part of the injected fuel adheres to the inner wall of one intake port by the intake air flow after a predetermined number of combustion cycles, the injection mode is changed to the intake stroke. Is replaced with primary injection with a relatively short injection period to promote vaporization of the adhered fuel. Thus, while taking into account the promotion of mixing of air and fuel, it is possible to suppress an increase in the amount of equilibrium adhesion due to the injecting fuel adhering to the adhering site of one intake port in each combustion cycle.

FIG. 4 is a flowchart showing details of the injection pulse signal setting process executed by the ECU 40 for each combustion cycle.
By executing the following injection pulse signal setting process, an instruction signal setting means for setting the injection pulse signals (instruction signals) for the first fuel injection valve 28 and the second fuel injection valve 30 is realized.

  In step S101 (abbreviated as “S101” in the figure, the same applies hereinafter), based on the operating state of the internal combustion engine 10, the first fuel injection valve 28 and the second fuel injection valve 30 in each combustion cycle (that is, the first fuel injection valve 30). The total fuel injection amount (for the next injection and the second injection) is calculated. Specifically, the pulse width (injection pulse width TI) of the injection pulse signal is calculated as an injection period proportional to the total fuel injection amount.

  The injection pulse width TI is calculated based on the basic injection pulse width (basic fuel injection amount) TP, and the basic injection pulse width TP is calculated from the rotational speed (the rotational speed of the internal combustion engine 10 calculated from the rotation pulse signal POS of the crank angle sensor 42). The engine speed is calculated based on the intake air amount detected from the flow rate detection signal Q of the air flow sensor 44. For example, the basic injection pulse width TP is set by referring to a basic injection pulse width map in which the basic injection pulse width TP is associated with the engine speed and the intake air amount. The basic injection pulse width map is obtained in advance by experiments and simulations, and is stored in a ROM (Read Only Memory) or the like.

In this embodiment, for convenience of explanation, for example, the operating state of the internal combustion engine 10 is divided into a low load / low rotation speed region A, a medium load / medium rotation speed region by a combination of the engine rotation speed and the intake air amount. a region B, is divided into regions C is a high-load, high rotational speed region, the combination of the engine speed and the intake air amount, if applicable to the region a, set the basic injection pulse width TP to TP _a, region if applicable to B sets the basic injection pulse width TP to TP _B, if applicable to the region C has set the basic injection pulse width TP to TP _C. Basic injection pulse width TP _A, TP _B, TP _C has a magnitude relation between _{TP A <TP B <TP C} .

Further, the ECU 40 calculates various correction coefficients COEF based on the coolant temperature detected based on the temperature detection signal TW output from the water temperature sensor 46, and calculates the basic injection pulse width TP, the various correction coefficients COEF, The total fuel injection amount to be injected into each cylinder 18 per combustion cycle as corrected by the correction value Ts for compensating for the operation delay of the first fuel injection valve 28 and the second fuel injection valve 30 as shown in the following equation. An injection pulse width TI corresponding to is calculated.
TI = TP × COEF + Ts

Therefore, the injection pulse width TI _A set in the region A, the injection pulse width TI _B set in the region _B , and the injection pulse width TI _C set in the region C are expressed by the following equations, respectively. _It has a magnitude relationship of _A <TI _B <TI _C.
TI _A = TP _A × COEF + Ts
TI _B = TP _B × COEF + Ts
TI _C = TP _C × COEF + Ts

In step S102, it is determined whether the operating state of the internal combustion engine 10 when the fuel injection amount is calculated in step S101 corresponds to one of the areas A to C. For example, the basic pulse width TP is TP _A set in step S101, TP _B, may be determined by whether either TP _C.
If it is determined that the operating state of the internal combustion engine 10 corresponds to the region C, the process proceeds to step S103 (Yes). On the other hand, if it is determined that the operating state of the internal combustion engine 10 does not correspond to the region C, the process proceeds to step S104 (No).

In step S103, the fuel sharing ratio P (= TI ₁ / TI ₂ ), which is the ratio of the injection pulse width TI ₁ of the primary injection to the injection pulse width TI ₂ of the secondary injection, is set to 1, and the first The injection period of the next injection and the injection period of the second injection are made the same. The sum (TI ₁ + TI ₂ ) of the injection pulse width TI ₁ of the primary injection and the injection pulse width TI ₂ of the secondary injection becomes the injection pulse width TI _C set in the region C.

Injection pulse width TI ₁ of the first primary injection substitutes P = 1 in the following equation, TI ₁ = TI _C / 2 and it can be determined by solving for TI _1, thereby, the injection of the secondary injection The pulse width TI ₂ can be obtained as TI ₂ = TI _C / 2, and TI ₁ = TI ₂ .
TI _C = TI ₁ + TI ₂
P = TI ₁ / TI ₂

  The reason why the fuel sharing ratio P is set to 1 in the region C is that in the region C, the required fuel injection amount increases according to the operating state of the internal combustion engine 10 and the injection period in the primary injection and the secondary injection This is because it is necessary to maximize the value. Therefore, the injection pulse width becomes longer as it becomes difficult to switch the injection timing, for example, the period from the beginning of the exhaust stroke to the middle of the intake stroke, so the injection timing of the first fuel injection valve 28 and the second fuel injection The injection timing of the valve 30 is synchronized without providing a phase difference, and the replacement of the injection timing is stopped. Thereby, the setting process of the injection pulse signal for the first fuel injection valve 28 and the second fuel injection valve 30 when the operating state of the internal combustion engine 10 corresponds to the region C is completed.

In step S104, the fuel sharing rate P when the operating state of the internal combustion engine 10 corresponds to the region A or the region B is set, thereby calculating the injection pulse widths in the primary injection and the secondary injection.
The fuel sharing ratio P is set so as to change according to the operating state of the internal combustion engine 10, that is, depending on how much the intake air amount and the engine rotational speed are in the region A and the region B. The fuel sharing rate P is set, for example, by referring to a fuel sharing rate map in which the fuel sharing rate P is associated with the engine speed and the intake air amount.

Specifically, the fuel injection ratio P is, than the injection pulse width TI ₂ of the secondary injection as towards the injection pulse width TI ₁ of the primary injection increases (TI _1> TI _2), each combustion In the cycle, it is set to be larger than 1 in order to reduce the amount of injected fuel adhering to the inner wall of the intake port.

Further, the fuel sharing ratio P is set so as to decrease as the intake air amount or the engine speed increases, and in each combustion cycle, the fuel injection amount injected in the secondary injection is injected in the primary injection. The fuel / air mixture sucked into the combustion chamber 36 from the first intake port 14 and the fuel and air sucked into the combustion chamber 36 from the second intake port 16 are brought close to the fuel injection amount. The deviation of the fuel concentration in the two air-fuel mixtures is reduced.
In the following description, for convenience, the operation state of the internal combustion engine 10 when the intake air amount or the engine rotational speed is relatively low fuel injection ratio P and P _A as being in the area A, the intake air amount or the engine speed If a relatively high fuel injection ratio P as the operation state of the internal combustion engine 10 is in the region B as a P _B, the fuel injection ratio P is assumed to be set to one of the P _a and P _B.

Figure 5 (a), the in the case the intake air amount or the engine speed is relatively low (in the case of region A), that the fuel injection ratio P is set to greater than 1 P _A in this step Based on the value of TI _A calculated as the injection pulse width TI in step S101, TI _A1 that is the injection pulse width TI ₁ of the primary injection and the injection pulse width TI ₂ of the secondary injection are expressed by the following equation: A certain TI _A2 is calculated.
TI ₁ = TI _A1 = P _A × TI _A / (P _A +1)
TI ₂ = TI _A2 = TI _A / (P _A +1)

On the other hand, as shown in FIG. 5 (b), if a relatively high amount of intake air or the engine rotational speed (for region B), the fuel injection ratio P is greater than 1 less than the value of P _A in this step By setting the value of P _B , the injection pulse width TI _B1 of the primary injection and the injection pulse width TI of the secondary injection are expressed by the following equation based on the injection pulse width TI _B calculated in step S101. _B2 is calculated.
TI ₁ = TI _B1 = P _B × TI _B / (P _B +1)
TI ₂ = TI _B2 = TI _B / (P _B +1)

When the intake air amount or the engine rotational speed is relatively high (in the case of region B), instead of changing the fuel sharing rate P from P _A to P _B as described above, the fuel sharing rate P is set to P _{A. Alternatively} , a predetermined amount may be added directly to the injection pulse width TI _A1 of the primary injection and the injection pulse width TI _A2 of the secondary injection that are calculated by setting.
For example, when the intake air amount or the engine speed is relatively high (in the case of region B), the injection pulse width TI ₁ of the primary injection increases from TI _A1 to TI _X1 , and the injection pulse width of the secondary injection When TI ₂ is to have increased from TI _A2 to TI _X2, increase .DELTA.TI ₁ of injection pulse width of the primary jet (= TI _X1 -TI _A1) and the increase in injection pulse width of the second-order injection .DELTA.TI ₂ ( = TI _X2 -TI _A2 ) is ΔTI ₁ <ΔTI ₂ , and ΔTI ₁ and ΔTI _{2 in} which the sum of TI _X1 and TI _X2 coincides with the injection pulse width TI _B are calculated, and this ΔTI ₁ And ΔTI ₂ can be set as predetermined amounts to be added to the injection pulse width TI _A1 of the primary injection and the injection pulse width TI _A2 of the secondary injection, respectively.

In step S105, it is determined whether the operating state of the internal combustion engine 10 corresponds to the region A or the region B when the fuel injection amount is calculated in step S101.
If it is determined that the operating state of the internal combustion engine 10 corresponds to the region B, the process proceeds to step S106 (Yes). On the other hand, when it is determined that the operating state of the internal combustion engine 10 corresponds to the region A, the process proceeds to step S107 (No).

In step S106, the injection end timing t _1eB of the primary injection when the operating state of the internal combustion engine 10 corresponds to the region B is set.
The injection end timing t _1eB in the primary injection is set according to the operating state of the internal combustion engine 10, that is, according to the intake air amount and the engine speed in the region B. Specifically, in region B, the injection end timing t _1eB is set later as the intake air amount or the engine speed increases. As a result, in the region B which is a medium load / medium rotational speed region, a period overlapping with the air intake period in the intake stroke in the injection period of the primary injection as the intake air amount or the engine rotational speed increases. By increasing the length, mixing of air and fuel is promoted.

For example, as shown in FIG. _6A , in region B, the injection end timing t _1eB of the primary injection when the intake air amount or the engine speed is relatively low (that is, on the region A side) is t _While the value of _1eα is set, as shown in FIG. 6B, in the region B, the injection of the primary injection when the intake air amount or the engine rotational speed is relatively high (that is, on the region C side). set the end time t _1Eb a value greater t _1Ibeta than the value of _t 1eα, the injection end timing t _1Eb in the region B may be set in two in accordance with the operating state of the internal combustion engine 10.

In step S106, by setting the injection end timing t _1eB of the primary injection when the operating state of the internal combustion engine 10 corresponds to the region B, the injection end timing t _1eB and the first time calculated in step S104 are calculated. Based on the injection pulse width TI ₁ (for example, TI _B1 ) in the primary injection, the injection start timing t _1sB (= t _{1eB −TI 1} ) of the primary injection can be calculated.

In step S107, the injection start timing t _1sA of the primary injection when the operating state of the internal combustion engine 10 corresponds to the region A is set.
The injection start timing t _1sA of the primary injection is set so as to change according to the operating state of the internal combustion engine 10, that is, depending on how much the intake air amount and the engine speed in the region A are. Specifically, in region A, the injection start timing t _1sA of the primary injection is set earlier as the intake air amount or the engine speed increases. As a result, in the low load / low rotational speed region A, the period in the exhaust stroke of the injection period of the primary injection is increased as the intake air amount or the engine rotational speed increases, or the primary By making the injection be performed during the exhaust stroke, the injected fuel is easily vaporized, and the amount of the injected fuel attached to the inner wall of the intake port is reduced.

For example, as shown in FIG. 7A, in region A, the injection start timing t _1sA of the primary injection when the intake air amount or the engine speed is relatively low is set to the value of t _1sα . As shown in FIG. 7B, in the region A, the injection start timing t _1sA of the primary injection when the intake air amount or the engine speed is relatively high (that is, on the region B side) is the value of t _1sα . set to a value smaller t _1Esubeta than may be the primary injection, the injection start timing t _1SA in the region a so as to set two types according to the operating state of the internal combustion engine 10.

In step S107, by setting the injection start timing t _1sA of the primary injection when the operating state of the internal combustion engine 10 corresponds to the region A, the injection start timing t _1sA and the first calculation calculated in step S104 are performed. The injection end timing t _1eA (= t _1sA + TI ₁ ) of the primary injection can be calculated based on the injection pulse width TI ₁ (for example, TI _A1 ) in the primary injection.

In step S108, the injection end timing _t2e of the secondary injection when the operating state of the internal combustion engine 10 corresponds to the region A or the region B is set.
The injection end timing t _2e of the secondary injection is fixed at a fixed time during the intake stroke regardless of the region A or the region B in order to reduce the amount of fuel injected on the inner wall of the port due to the intake air flow in each combustion cycle. Is done. For example, the injection end timing t _2e of the secondary injection may be set to a timing at which the lift amount of the intake valve 20 is maximized, that is, the degree of opening of the intake valve 20 is maximized.

As shown in FIG. 8, in step S108, the injection end timing t _2e of the secondary injection when the operating state of the internal combustion engine 10 corresponds to the region A or the region B is set. Based on t _2e and the injection pulse width TI ₂ (for example, TI _A2 or TI _B2 ) in the secondary injection calculated in step S104, the injection start timing t _2s (= t _2e −TI ₂ ) of the secondary injection. Can be calculated.

In step S109, it is determined whether or not the current injection timings of the first fuel injection valve 28 and the second fuel injection valve 30 have continued for a predetermined number of combustion cycles. The injection timings of the first fuel injection valve 28 and the second fuel injection valve 30 are interchanged.
That is, when the injection mode of the first fuel injection valve 28 is set to the primary injection and the injection mode of the second fuel injection valve 30 is set to the secondary injection, the injection by the injection mode is performed in a predetermined combustion cycle. When it is determined that the fuel injection is performed several times continuously, the injection mode of the first fuel injection valve 28 is switched to the secondary injection, and the second fuel injection valve 30 is switched to the primary injection. Conversely, when the injection mode of the first fuel injection valve 28 is set to the secondary injection and the injection mode of the second fuel injection valve 30 is set to the primary injection, the injection in the injection mode is a predetermined combustion. When it is determined that the number of cycles has been continuously performed, the injection mode of the first fuel injection valve 28 is switched to the primary injection, and the injection mode of the second fuel injection valve 30 is switched to the secondary injection.

The predetermined combustion cycle number N is set so as to change according to the operating state of the internal combustion engine 10. Specifically, the predetermined number of combustion cycles N (an integer greater than or equal to 1) is set so as to decrease as the intake air amount or the engine speed increases in the regions A and B.
In areas A and B, as the intake air amount or the engine speed increases, the fuel injection amounts of the first fuel injection valve 28 and the second fuel injection valve 30 increase. The amount of fuel injected on the inner wall increases. In contrast, the primary injection and the secondary injection are frequently switched by reducing the number of consecutive combustion cycles in the same state of the injection modes performed in the first fuel injection valve 28 and the second fuel injection valve 30. In particular, vaporization of the attached fuel generated by the secondary injection is promoted to suppress an increase in the amount of equilibrium adhesion.
If the predetermined number of combustion cycles N is set to 1, the injection timing of the first fuel injection valve 28 and the injection timing of the second fuel injection valve 30 do not continue, that is, the first fuel injection valve 28 and the second fuel injection Since each injection mode performed in the injection valve 30 does not continue in the same state, the equilibrium adhesion amount becomes the smallest.

For example, as shown in FIG. 9A, when the intake air amount or the engine speed is relatively low in the regions A and B, the predetermined combustion cycle number N is set to N _L (eg, 3), As shown in FIG. 9C, when the intake air amount or the engine speed is relatively high in the regions A and B, the predetermined combustion cycle number N is set to N _H (for example, 1). As shown in (b), when the intake air amount or the engine speed is medium in the regions A and B, the predetermined number of combustion cycles N is set to N _M (for example, 2), and N _L , The magnitude relationship between N _M and N _H can satisfy N _L <N _M <N _H.

  By executing Step S104 to Step S109, the setting of the injection pulse signal for the first fuel injection valve 28 and the second fuel injection valve 30 when the operating state of the internal combustion engine 10 corresponds to the region A or the region B is completed. .

According to such an ECU 40, a phase difference is provided between two injection timings, that is, an injection timing at which the first fuel injection valve 28 injects fuel and an injection timing at which the second fuel injection valve 30 injects fuel in each combustion cycle. However, the injection pulse signal is set so that the two injection timings are alternately switched every predetermined number of combustion cycles in accordance with the operating state of the internal combustion engine 10.
Therefore, in each combustion cycle, even if the fuel is injected by the secondary injection having a relatively long injection period in the intake stroke, even if a part of the injected fuel adheres to the port inner wall of one intake port by the intake air flow, it is predetermined. After the number of combustion cycles has elapsed, the injection mode can be switched to primary injection with a relatively short injection period in the intake stroke to promote vaporization of the attached fuel.
For this reason, it is possible to suppress an increase in the amount of equilibrium adhesion by injecting fuel one after another to the attachment site of one intake port for each combustion cycle while taking into account the promotion of mixing of air and fuel. It is possible to improve the exhaust emission and fuel consumption performance by suppressing the air-fuel ratio fluctuation.

In the above-described embodiment, in the first injection, one fuel injection valve starts fuel injection in the exhaust stroke. However, the present invention is not limited to this. In the first injection, one fuel injection is simply performed. The valve may start injection before the other fuel injection valve. For example, in the primary injection, one fuel injection valve may inject fuel during a period in which the opening degree of the intake valve 20 is relatively small during the intake stroke. In this case, in the secondary injection, for example, the degree of opening of the intake valve 20 is set so that the intake air amount in the injection period of the other fuel injection valve is larger than the intake air amount in the injection period of one fuel injection valve. The other fuel injection valve may inject fuel during a period in which is relatively large.
Even when the primary injection and the secondary injection are performed in this way, if the injection mode of the first fuel injection valve 28 and the second fuel injection valve 30 is fixed, the suction during the injection period is caused by the secondary injection. Since the equilibrium adhesion amount increases at the intake port where the air amount increases, it is effective to alternately switch the injection mode for each predetermined combustion cycle by the setting process of the injection pulse signal according to the above-described embodiment.

  The parameter that defines the operating state of the internal combustion engine 10 is not limited to the combination of the engine rotational speed and the intake air amount described above. For example, the generated torque of the internal combustion engine 10 and the intake pipe 12 Parameters indicating the load (engine load) of the internal combustion engine 10 such as negative pressure and throttle opening can be combined.

In the foregoing embodiment, the region A and the operation state of the internal combustion engine 10, by dividing the regions B and C, and the basic injection pulse width TP corresponding to the respective regions TP _A, TP _B, the three TP _C However, instead of this, the operating state of the internal combustion engine 10 may be divided into two or four or more regions, and the basic injection pulse width TP corresponding to each region may be set.
Fuel share P set by dividing into region A and region B, and injection of primary injection set by dividing region B into a case where the intake air amount or the engine rotational speed is relatively low and a case where it is high The end timing t _1eB , the region A is _{divided into} a case where the intake air amount or the engine rotational speed is relatively low and a case where the region is relatively high, and the injection start timing t _{1sB of the} primary injection is set. Similarly to the basic injection pulse width TP, the predetermined number of combustion cycles N set by dividing the intake air amount or the engine rotational speed into a relatively low case, a high case, and a medium level, if the number is a plurality, It can be set by increasing / decreasing.

The flowchart of FIG. 4 shows an example of the setting process of the injection pulse signal. For example, first, the region A to the region C are determined, and the setting process of the injection pulse width signal is executed according to the determined region. May be. Thus, for example if it is judged that the area A, the injection pulse width TI _A calculated as in step S101 in the first step, to set the fuel injection ratio P _A, as in step S104 in the second step Then, the injection pulse width TI _A1 of the primary injection and the injection pulse width TI _A2 of the secondary injection are calculated, and the injection start timing t _1sA of the primary injection is set as in step S107 in the third step. Thus, the injection end timing t _1eA of the primary injection is calculated, the injection end timing t _2e of the secondary injection is set as in step S108 in the fourth step, and the injection start timing t of the secondary injection is set. _2s may be calculated, and the injection timing may be changed in the fifth step as in step S109. Similarly, when the region B is determined, the processes of step S101, step S104, step S106, step S108, and step S109 are performed in this order. When the region C is determined, step S101, You may perform each process of step S103 in this order.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 14 ... 1st intake port, 16 ... 2nd intake port, 18 ... Cylinder, 20 ... Intake valve, 28 ... 1st fuel injection valve, 30 ... 2nd fuel injection valve, 36 ... Combustion chamber, 40 ... ECU, 42 ... Crank angle sensor, 44 ... Air flow sensor

Claims (12)

An internal combustion engine having a first intake passage and a second intake passage for each cylinder, a first fuel injection valve disposed in the first intake passage, and a second fuel injection valve disposed in the second intake passage. A fuel injection control device for causing the first fuel injection valve and the second fuel injection valve to inject fuel,
In each combustion cycle, the two injection timings are set while providing a phase difference between two injection timings of the injection timing at which the first fuel injection valve injects fuel and the injection timing at which the second fuel injection valve injects fuel. A fuel injection control apparatus comprising: instruction signal setting means for setting instruction signals for the first fuel injection valve and the second fuel injection valve so as to be alternately switched every predetermined number of combustion cycles.   2. The fuel injection control device according to claim 1, wherein the instruction signal setting unit sets the instruction signal such that the predetermined number of combustion cycles changes according to an operating state of the internal combustion engine.   3. The fuel injection control device according to claim 2, wherein the instruction signal setting means sets the instruction signal so that the predetermined number of combustion cycles decreases as the engine load or the engine speed increases. .   The instruction signal setting means is configured such that one of the first fuel injection valve and the second fuel injection valve starts an injection in an exhaust stroke before the other fuel injection valve, and in the intake stroke 4. The instruction signal according to claim 1, wherein the instruction signal is set so that an injection period of the other fuel injection valve is longer than an injection period of the one fuel injection valve. A fuel injection control device according to claim 1.   The instruction signal setting means is a first injection in which the one fuel injection valve is injecting fuel with respect to a second injection period in which the other fuel injection valve is injecting fuel. The fuel injection control device according to claim 4, wherein the instruction signal is set so that a ratio of a period changes according to an operating state of the internal combustion engine.   The instruction signal setting means limits the first injection period to be equal to or longer than the second injection period, and sets the instruction signal so that the ratio decreases as the engine load or the engine speed increases. The fuel injection control device according to claim 5, wherein:   The instruction signal setting means sets the instruction signal so that a timing for ending fuel injection by the one fuel injection valve changes according to an operating state of the internal combustion engine. A fuel injection control device according to claim 5 or claim 6.   The instruction signal setting means sets the instruction signal so that the timing for ending the fuel injection by the one fuel injection valve is delayed as the engine load or the engine speed increases. Item 8. The fuel injection control device according to Item 7.   The instruction signal setting means sets the instruction signal so that a timing for starting fuel injection by the one fuel injection valve changes according to an operating state of the internal combustion engine. The fuel injection control device according to claim 5 or 6.   The instruction signal setting means sets the instruction signal so that the timing of starting fuel injection by the one fuel injection valve becomes earlier as the engine load or the engine speed increases. Item 10. The fuel injection control device according to Item 9.   11. The instruction signal setting means according to any one of claims 4 to 10, wherein a timing at which fuel injection by the other fuel injection valve is terminated is fixed at a fixed timing during the intake stroke. The fuel injection control device described.   The fuel injection control according to any one of claims 1 to 11, wherein when the operating state of the internal combustion engine is in a high-load high-rotation region, the replacement of the two injection timings is stopped. apparatus.