JP4304463B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  In recent years, lean burn (lean combustion) in which the gasoline mixture ratio is reduced by in-cylinder direct fuel injection, which has improved fuel efficiency over intake port injection, has been proposed. Further, like the engine described in Patent Document 1, both an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into an intake port are provided. An internal combustion engine has been proposed.

This direct in-cylinder fuel injection is effective in improving the fuel efficiency as described above, but on the other hand, in-cylinder injection can improve the maximum output performance of the engine rather than intake port injection. . In port injection, the gas sucked into the cylinder is a mixture of air and fuel, but in cylinder injection, all the gas sucked into the cylinder is air, and fuel is added separately. The amount of oxygen can be increased. Further, in the cylinder injection, since the fuel is vaporized entirely in the cylinder, the temperature of the mixture in the cylinder can be lowered as compared with the intake port injection. When the temperature of the air-fuel mixture decreases, the density in the cylinder increases, so that it is possible to increase the amount of oxygen that can be filled in a cylinder having a constant volume. Therefore, in-cylinder injection can secure more oxygen when the throttle valve is fully opened and more fuel can be burned, so that the maximum output performance can be increased compared to intake port injection. . Therefore, since it is efficient to inject fuel by in-cylinder injection at the time of high load where output performance is required, an internal combustion engine combined with intake port injection has also been proposed.
JP-A-2001-20837 (Claim 1, FIG. 1)

However, in the latter case, if in-cylinder injection continues to be performed at a high load, there is a risk that the exhaust system parts will overheat.
That is, during high load operation in which a large amount of fuel is injected, the amount of fuel injection is large, the amount of air introduced into the cylinder is large, and the pressure is also high in the cylinder during the compression stroke, so the fuel is difficult to vaporize. . In addition, since the vaporization time until ignition is short, it is difficult to vaporize all the injected fuel. In addition, fuel and air are likely to be insufficiently mixed, resulting in slow combustion. For this reason, combustion continues until the exhaust stroke or combustion in the exhaust system is facilitated, so that the exhaust gas temperature rises. As the exhaust gas temperature rises, the exhaust purification catalyst or the like may be deteriorated or melted.

  At that time, a technique for increasing the fuel injection amount (so-called OT increase) to lower the exhaust gas temperature is known. However, the increased fuel deteriorates the fuel consumption rate (fuel consumption) or pollutes the exhaust gas. There was a problem.

  The present invention has been made in view of such circumstances, and an object thereof is an internal combustion engine capable of reducing the temperature of exhaust gas without deteriorating fuel consumption when it is necessary to prevent overheating of exhaust system components. An object of the present invention is to provide an engine fuel injection control device.

In order to achieve the above object, a fuel injection control device for an internal combustion engine according to claim 1 is at least one of an in-cylinder injector that directly injects fuel into a cylinder and an intake passage injector that injects fuel into an intake passage. A fuel injection control device applied to an internal combustion engine in which a fuel injection mode is set, and when it is determined that the temperature of the exhaust system component is equal to or higher than a predetermined temperature, Injection mode changing means for changing the setting state of the injection mode so as to increase the ratio of the fuel injection amount from the intake passage injector to the injection amount of fuel from the in-cylinder injector; and the setting state of the injection mode ; Temperature estimating means for estimating the temperature of the exhaust system component based on the engine operating status; and based on the temperature of the exhaust system component estimated by the temperature estimating means. And determining whether or not the exhaust system part is overheated and when it is determined that the exhaust system part is overheated after the injection form changing means changes the injection form. And a fuel increase execution means for increasing the fuel injection amount, and the fuel injection by the fuel increase execution means is performed from the in-cylinder injector .

In the above configuration, when it is determined that the temperature of the exhaust system component is equal to or higher than the predetermined temperature, the injection mode is changed so as to increase the ratio of the fuel injection amount from the intake port injector to the injection amount from the in-cylinder injector. . Therefore, combustion is less likely to be slow in the intake port injection, so that an increase in exhaust gas temperature can be suppressed as compared with in-cylinder injection. Further, in order to suppress the temperature rise of the exhaust system parts, the fuel efficiency can be improved as compared with the OT increase that supplies more fuel than that used for combustion.
Further, the fuel injection amount is increased only when it is determined that the estimated temperature of the exhaust system component is overheated. Therefore, the deterioration of the fuel consumption due to the fuel increase can be minimized.
Further, the fuel injection for the increased amount is performed by the in-cylinder injector. Because the increased amount of fuel is hardly used for combustion, the fuel injection for the increased amount does not slow down the combustion, and only the cooling effect by the latent heat of vaporization of the fuel directly injected into the cylinder can be enjoyed. . Therefore, the exhaust gas temperature can be reduced more effectively than the fuel increase by the intake port injection.

A fuel injection control device for an internal combustion engine according to claim 2 is a fuel injection form using at least one of an in-cylinder injector that directly injects fuel into a cylinder and an intake passage injector that injects fuel into an intake passage. Is a fuel injection control device applied to an internal combustion engine, and when it is determined that the temperature of the exhaust system component is equal to or higher than a predetermined temperature in a state where fuel injection is performed only from the in-cylinder injector, Based on injection form changing means for changing the injection form so that the fuel injection from the in-cylinder injector is injected from the intake passage injector, and the exhaust system based on the setting state of the injection form and the engine operating condition Temperature estimation means for estimating the temperature of the component, and the exhaust system component is overheated based on the temperature of the exhaust system component estimated by the temperature estimation means. Fuel increase execution is performed to increase the fuel injection amount when it is determined that the exhaust system component will be overheated after the injection form change by the injection form changing means Means for performing fuel injection by the fuel increase execution means from the in-cylinder injector .

In the above configuration, when performing in-cylinder injection with excellent output performance during high-load operation or the like, when it is determined that the temperature of the exhaust system parts rises and exceeds the predetermined temperature, the in-cylinder injection is not performed for the first time. Switch to intake port injection, where the temperature of the exhaust system parts does not rise easily. Therefore, the output performance during operation can be utilized to the maximum and the temperature rise of the exhaust system parts can be suppressed.
Further, the fuel injection amount is increased only when it is determined that the estimated temperature of the exhaust system component is overheated. Therefore, the deterioration of the fuel consumption due to the fuel increase can be minimized.
Further, the fuel injection for the increased amount is performed by the in-cylinder injector. Because the increased amount of fuel is hardly used for combustion, the fuel injection for the increased amount does not slow down the combustion, and only the cooling effect by the latent heat of vaporization of the fuel directly injected into the cylinder can be enjoyed. . Therefore, the exhaust gas temperature can be reduced more effectively than the fuel increase by the intake port injection.

The fuel injection control device for an internal combustion engine according to 請 Motomeko 3 is the fuel injection control apparatus for an internal combustion engine according to claim 1 or 2, wherein the temperature estimating means, the injection mode before change by said injection mode changing means Correspondingly, a first temperature estimating means for estimating the temperature of the exhaust system component based on the engine operating status, and an exhaust system component based on the engine operating status corresponding to the changed injection mode by the injection mode changing means. Second temperature estimating means for estimating the temperature, and switching from the first temperature estimating means to the second temperature estimating means by the injection mode changing means to estimate the temperature of the exhaust system component. Is the gist.

  According to the above configuration, the temperature estimation of the exhaust system parts based on the injection mode and the engine operation status before the change by the injection mode change unit is performed by the first temperature estimation unit, and is based on the changed injection mode and the engine operation status. The temperature of the exhaust system component can be estimated by the second temperature estimating means.

The fuel injection control device for an internal combustion engine according to claim 4 is the fuel injection control apparatus for an internal combustion engine according to any one of claims 1 to 3, the fuel injection by the previous SL fuel increase execution means is executed a plurality of times In this case, the gist is to reduce the current increase amount as compared with the previous fuel increase amount .

The injection form by jetting form changing means is changed, the temperature of the exhaust system parts to some extent lowered, when the fuel injection by the fuel increase execution means is executed multiple times, the fuel injection increase amount of the previous A small amount is sufficient compared to the amount of fuel increase . Therefore, the fuel consumption can be improved.

  According to the present invention, when it is necessary to prevent overheating of exhaust system parts, the temperature of exhaust gas can be lowered without deteriorating fuel consumption.

(First embodiment)
Hereinafter, a first embodiment of a fuel injection control device for an internal combustion engine according to the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing a schematic configuration of a fuel injection control device 1 according to the present embodiment. As shown in FIG. 1, the internal combustion engine to which the fuel injection control device 1 is applied is configured around a four-cycle in-cylinder injection internal combustion engine 11 (hereinafter also simply referred to as “internal combustion engine”). . The internal combustion engine 11 includes a piston 13 in a cylinder 12, and the piston 13 is connected to a crankshaft 15 that is an output shaft of the internal combustion engine 11 via a connecting rod 14. The connecting rod 14 replaces the reciprocating motion of the piston 13 with the rotation of the crankshaft 15.

  A combustion chamber 16 is defined in the cylinder 12 above the piston 13. An in-cylinder injector (hereinafter also simply referred to as “in-cylinder injector”) 17 is attached to the combustion chamber 16. The in-cylinder injector 17 is supplied with a predetermined high-pressure fuel through a well-known fuel supply mechanism (not shown). The fuel is injected into the combustion chamber 16 by opening the in-cylinder injector 17.

  The combustion chamber 16 is provided with a spark plug 18 that ignites an air-fuel mixture composed of fuel and air. The ignition timing of the air-fuel mixture by the spark plug 18 is adjusted by an igniter 19 provided above the spark plug 18.

  Further, an intake passage 20 and an exhaust passage 21 are communicated with the combustion chamber 16, a surge tank 23 is provided near the intake side of the intake passage 20, and a catalyst 24 is provided near the exhaust side of the exhaust passage 21. It has been. The intake port 20a, which is a communication portion between the combustion chamber 16 and the intake passage 20, has an intake port injection injector (hereinafter also simply referred to as "intake port injector") 22 for injecting fuel into the intake port 20a. It is attached. The intake port injector 22 is supplied with a predetermined high-pressure fuel through a well-known fuel supply mechanism (not shown). The fuel is injected and supplied into the intake port 20a by opening the intake port injector 22.

  On the other hand, the fuel injection control device 1 includes a crank sensor 31 and an accelerator pedal (not shown) for detecting the rotational phase (crank angle) and the engine rotational speed of the crankshaft 15 as sensors for detecting the engine operating condition. ) Is provided with an accelerator sensor 32 for detecting the depression amount. Further, an exhaust temperature sensor 33 for detecting the exhaust gas temperature, an air flow meter 34 for detecting the intake air amount GA, and the like are provided.

  Further, this apparatus is provided with an electronic control unit (ECU) 30. The electronic control unit 30 is composed of a digital computer, and includes a CPU (central processing unit) 36, a ROM 37, a RAM 38, an input port 39, and an output port 40 connected to each other by a bidirectional bus 35. Therefore, the electronic control unit 30 calculates the engine operating state at that time based on the output signals taken from the respective sensors, and the in-cylinder injector 17, the intake port injector 22, and the spark plug 18 based on the calculation results. The drive of (igniter 19) etc. is controlled.

  Further, the electronic control unit 30 performs fuel injection by the in-cylinder injector 17 (hereinafter also simply referred to as “in-cylinder injection”) and fuel injection by the intake port injector 22 (hereinafter simply referred to as “in-cylinder injection”) in accordance with the calculated engine operating conditions. Change the sharing ratio of "Intake port injection". For example, during low-load operation, the electronic control unit 30 basically opens the intake port injector 22 to inject fuel into the intake port 20a during the intake stroke of the internal combustion engine 11. On the other hand, at the time of high load operation where high output is required, the electronic control unit 30 opens the in-cylinder injector 17 to inject fuel into the combustion chamber 16 during the compression stroke of the internal combustion engine 11. Furthermore, in this embodiment, both the in-cylinder injector 17 and the intake port injector 22 are opened so that the injection into the combustion chamber and the injection into the intake port are performed together.

  Further, the CPU 36 described above includes an injection mode changing means for changing the ratio of in-cylinder injection and intake port injection according to each step to be described later, a temperature estimating means for estimating the temperature of exhaust system components, and an increase in the fuel injection amount. It also serves as a fuel increase execution means to be performed.

FIG. 2 is a diagram showing a processing procedure for control of the fuel injection control device 1 in the present embodiment.
As shown in FIG. 2, in this series of processing, first, it is determined whether or not the internal combustion engine 11 is operated at a high load (step 101; hereinafter, “step” is abbreviated as “S”). If it is determined that the engine is operating at a high load (S101: YES), the drive of the in-cylinder injector 17 is controlled to perform the injection into the combustion chamber 16, and the intake port injector 22 The drive is controlled and the injection to the intake port 20a is prohibited (S102). Next, the injection form is determined (S103). Specifically, the sharing ratio of the fuel injection amounts of the in-cylinder injector 17 and the intake port injector 22 is determined. When the engine is operated at a high load and in-cylinder injection is being performed, the sharing ratio determined here is in-cylinder injection: intake port injection = 10: 0. When it is determined that the vehicle is not operated at a high load in the first stage (S101: NO), the injection mode is similarly determined (S103). Next, a map corresponding to the determined predetermined share is read to estimate the temperature of the exhaust system parts (S104).

  Subsequently, it is determined whether or not the estimated temperature of the exhaust system component is overheated (S105). If it is determined that the excessive temperature rise will not occur (S105: NO), the process proceeds to a determination (S106) as to whether or not the temperature exceeds a predetermined temperature set lower than the excessive temperature increase. The predetermined temperature is set in advance as a threshold value for determining whether or not there is a possibility of overheating even though the temperature of the exhaust system component gradually rises but does not go up to an excessive temperature. Subsequently, when it is determined that the estimated temperature of the exhaust system component is equal to or higher than a predetermined temperature (S106: YES), the injection mode is changed (S107). Specifically, the ratio of the fuel injection amount between the in-cylinder injector 17 and the intake port injector 22 increases the ratio of the fuel injection amount from the intake port injector 22 to the fuel injection amount from the in-cylinder injector 17. The injection mode is changed. Next, an injection mode that is a share ratio of the changed fuel injection amount is determined (S103). Then, as before, a map corresponding to the changed sharing ratio (injection mode determined in S103) is read, and the temperature of the exhaust system parts is estimated again (S104). Thereafter, it is determined whether or not the temperature rises excessively (S105). If it is determined that the temperature does not increase excessively (S105: NO), the process flow is the same as described above, and the fuel injection amount is changed as needed. The sharing ratio is changed (S107), and the temperature of the exhaust system component based on the changed sharing ratio is estimated each time (S104). If it is determined that the temperature does not exceed the predetermined temperature (S106: NO), this process is temporarily terminated.

  As described above, the processing from the injection mode determination (fuel injection amount sharing ratio determination) (S103) to the injection mode change (S107) is repeatedly performed until it is determined that the estimated temperature is excessive. Specifically, the initial ratio of in-cylinder injection: intake port injection = 9: 1 is changed to, for example, the ratio of in-cylinder injection: intake port injection = 5: 5 (S107). If the share ratio still exceeds the predetermined temperature (S106: YES), the share ratio of the intake port injection is further increased, for example, changed to the ratio of in-cylinder injection: intake port injection = 7: 3. (S107). In this way, control is performed to increase the share ratio of intake port injection by a predetermined amount.

On the other hand, when it is determined that the estimated temperature of the exhaust system component is overheated (S105: YES), fuel increase for preventing overheating of the exhaust system component is executed (S108).
In other words, first, the in-cylinder injection is gradually switched to the intake port injection, and the fuel increase (OT increase) is executed for the first time if the temperature rises and the temperature rises excessively. Further, when the fuel increase execution (S108) is executed a plurality of times while this series of processes is repeatedly performed, the executed fuel increase amount is decreased as compared with the previous fuel increase amount. This is what is controlled.

  2, the CPU 36 that executes the procedure of S107 corresponds to the injection form changing means, and the CPU 36 that executes the procedure of S108 corresponds to the fuel increase executing means.

  Next, the exhaust system temperature estimation (S104) will be described in detail. The engine speed NE is calculated by the CPU 36 from the output signal of the crank sensor 31. Further, the load GN (g / rev) of the internal combustion engine 11 is obtained by dividing the intake air amount GA detected by the air flow meter 34 by the engine rotational speed NE (GN = GA / NE). During operation of the internal combustion engine 11, the electronic control unit 30 calculates the engine rotational speed NE and the load GN, and estimates the temperature of the exhaust system parts with reference to a map stored in advance together with the determined sharing ratio. . In the present embodiment, the estimated temperature T is obtained by weighted average processing, so-called annealing processing. That is, the estimated temperature T [° C.] is obtained by the following equation.

Estimated temperature T [° C.] = (1− [Time constant (map value)]) × [Previous value] + [Time constant] × ([Stationary temperature (map value)] − [Previous estimated value])
Or estimated temperature T [° C.] = [Previous value] + [time constant (map value)] × [steady temperature (map value)]
If the operation is continued while maintaining certain operating conditions (engine rotational speed NE, load GN, injection mode (sharing ratio of in-cylinder injection and intake port injection in fuel injection)), the estimated temperature T settles to a certain temperature. . The convergence value of the temperature during the steady operation is the steady temperature.

  The time constant is a numerical value representing the degree of change in estimated temperature until convergence. The value takes a value from 0 to 1, and is set to a value close to 1 under an operating condition where the temperature change proceeds rapidly, and is set to a value close to 0 under an operating condition where the temperature change is slow. The

  FIG. 3 shows a map for obtaining the above steady temperature. (A) shows the case where the share ratio of the injected fuel is in-cylinder injection: intake port = 10: 0, and (b) shows the case where in-cylinder injection: intake port = 0: 10. The ROM 37 of the electronic control device 30 stores in advance a steady temperature and time constant for each combination of operating conditions obtained by experiments or the like as a map. In calculating the estimated temperature, the steady temperature map (FIG. 3) and the time constant map are read and calculated.

  In general, the estimated temperature increases as the load increases and the rotation speed increases as the amount of heat generated by combustion per unit time increases. Further, in the high-load operation region, as shown in FIGS. 3A and 3B, even if the engine speed NE and the load GN are the same, the in-cylinder injection has a higher estimated temperature than the intake port injection. . That is, when it is necessary to suppress the temperature rise of the exhaust system parts, it can be said that the intake port injection is more effective than the in-cylinder injection as the temperature is less likely to rise.

Although the illustration of the time constant is omitted, the time constant is obtained using a map similar to the steady temperature shown in FIG.
According to the embodiment described above, the following effects can be obtained.

  (1) In this embodiment, after determining the injection mode, when it is determined that the temperature is equal to or higher than the predetermined temperature, first, the intake port injector for the injection amount from the in-cylinder injector 17 is first determined by the CPU 36 (S107) as the injection mode changing means. The injection mode is changed so that the ratio of the fuel injection amount from 22 is increased. As described above, in the cylinder injection, the amount of air introduced into the cylinder is large, the pressure is high in the cylinder during the compression stroke, so the fuel is difficult to vaporize, and the vaporization time until ignition is short. It becomes difficult to vaporize all the injected fuel. Therefore, mixing of air and fuel tends to be insufficient, combustion deteriorates and becomes slow, and the exhaust gas temperature tends to rise.

  In this regard, according to the intake port injection, fuel and air are mixed while moving from the intake port into the cylinder, so that combustion is less likely to be slow and the rise in exhaust gas temperature is suppressed compared to in-cylinder injection. be able to. Usually, in order to prevent the exhaust gas temperature from rising and to prevent the catalyst bed temperature from being excessively heated, the mainstream is to increase the amount of fuel (so-called OT increase) that supplies more fuel than is used for combustion. Compared with this, in this embodiment, the fuel increase is not suddenly performed, but first, the in-cylinder injection is gradually switched to the intake port injection in which the exhaust gas temperature hardly increases. For this reason, if a certain level of temperature rise can be prevented at this stage, it is not necessary to increase the amount of fuel, leading to improved fuel consumption and prevention of black exhaust gas.

  (2) Furthermore, according to the present embodiment, during high load operation, in-cylinder injection with excellent output performance is actively performed, and when it is necessary to suppress the temperature rise of the exhaust system parts, the intake port is less likely to rise in temperature. Control to gradually increase the injection ratio. Therefore, the output performance during engine operation can be utilized as efficiently as possible, and the temperature rise of the exhaust system parts can be suppressed.

(3) Further, by gradually increasing the share ratio of the intake port injection, the mixed state of intake air and fuel becomes good, the combustion speed is fast, and the conversion efficiency of combustion energy into work (output torque) increases. . Therefore, it is possible to reduce the temperature of the exhaust gas without fuel increase, reducing thereby preventing the deterioration of the catalyst, CO and HC contained in the exhaust gas, the occurrence of generation or black smoke of harmful substances such as NO _X can do.

(Second Embodiment)
Next, a second embodiment that embodies the present invention will be described with a focus on differences from the first embodiment with reference to FIGS. 4 and 5. The mechanical configuration of the fuel injection control device in the present embodiment is the same as that in the first embodiment, and only the control method is different. Therefore, only the control method is illustrated, and the mechanical configuration is illustrated and Description is omitted.

  FIG. 4 is a diagram showing a processing procedure for control of fuel injection in the present embodiment. In executing this process, it is assumed that fuel injection is basically performed by the intake port injector 22. As shown in FIG. 4, in this series of processing, first, it is determined whether or not the internal combustion engine 11 is operated at a high load (S201). If it is determined that the engine is operating at a high load (S201: YES), the drive of the in-cylinder injector 17 is controlled to perform injection into the combustion chamber 16, and the intake port injector 22 The drive is controlled and the injection to the intake port 20a is prohibited (S202). This is because, when the load is high, in-cylinder injection is executed instead of intake port injection to provide stronger output performance. Next, the map corresponding to the fuel injection amount sharing ratio: in-cylinder injection: intake port injection = 10: 0 (FIG. 3A for the steady temperature) is read to estimate the temperature of the exhaust system parts (S203). . Subsequently, it is determined whether or not the estimated temperature of the exhaust system component is equal to or higher than a predetermined temperature (S204). When it is determined that the temperature does not exceed the predetermined temperature (S204: NO), this process is temporarily terminated.

  When it is determined that the estimated temperature is equal to or higher than the predetermined temperature (S204: YES), the mode change control for completely switching from the in-cylinder injection to the intake port injection is performed, and the drive of the in-cylinder injector 17 is controlled to control the combustion chamber The injection into the intake port 16 is prohibited, and the drive of the intake port injector 22 is controlled to execute the injection into the intake port 20a (S205). That is, the share ratio of the fuel injection is in-cylinder injection: intake port injection = 0: 10. Next, the routine proceeds to routine A shown in FIG. 5, and a map (FIG. 3 (b)) corresponding to the ratio of in-cylinder injection: intake port injection = 0: 10 is read, and the temperature of the exhaust system parts is estimated again. (S206). Thereafter, it is determined whether or not the temperature of the exhaust system component is overheated (S207), and when it is determined that the temperature is not overheated (S207: NO), this process is temporarily terminated. If it is determined that the temperature will rise excessively (S207: YES), the driving of the in-cylinder injector 17 is controlled to increase the amount of fuel ((S208). Here, this process is temporarily terminated. In the initial stage, when it is determined that the engine is not operating at a high load in the determination of whether or not the engine is operating at a high load (S201: NO), the routine proceeds to routine A, and in-cylinder injection: intake air A map corresponding to the sharing ratio of port injection = 0: 10 (FIG. 3B) is read to estimate the temperature of the exhaust system parts (S206), and thereafter the same processing as described above is performed.

  In each step, the CPU 36 that executes the procedure of S205 in FIG. 4 corresponds to the injection form changing means, and the CPU 36 that executes the procedure of S203 corresponds to the first temperature estimating means. Further, the CPU 36 that executes the procedure of S206 in FIG. 5 corresponds to the second temperature estimating means, and the CPU 36 that executes the procedure of S208 corresponds to the fuel increase executing means.

  According to this embodiment described above, the same effects as those of the first embodiment can be obtained. Further, in the present embodiment, the fuel increase when it is determined that the temperature rises excessively is performed by in-cylinder injection (S208). Here, the fuel supplied for combustion is provided by intake port injection, and the increased amount of fuel is hardly used for combustion, so even if the increased amount of injection is performed by in-cylinder injection. Only the cooling effect by the latent heat of vaporization of the fuel directly injected into the cylinder 12 can be enjoyed without slowing the combustion. Therefore, by executing the fuel increase by in-cylinder injection, the exhaust gas temperature can be reduced more efficiently than when performing the intake port injection.

  Note that the flowcharts (FIGS. 2, 4, and 5) shown in the embodiments only show examples as specific examples of the present invention, and do not limit the order or configuration of the steps. Therefore, another step can be newly added or a part of steps can be deleted.

The above embodiment may be changed to another embodiment (another example) as follows.
In the present embodiment, the intake air injection is performed by the intake port injector 22 provided in the intake port 20a which is a communication portion between the combustion chamber 16 and the intake passage 20, but instead of this, the surge tank 23 shown in FIG. You may comprise as injection by the injector provided in. Alternatively, a cold start injector may be used.

  -In the temperature estimation of the exhaust system parts in this embodiment, the temperature of the exhaust system parts is estimated by reading out the steady temperature and the time constant from the map stored in advance, but instead, a function that does not use the map It is good also as an actual value by the estimation from the exhaust temperature sensor 33 which does not estimate by the type | formula and also estimates.

  -In this embodiment, what provided the air flow meter 34 was demonstrated and it was set as the structure utilized for detection of load, However, It is good also as what measures an intake air amount with the pressure sensor provided in the intake pipe.

  Further, as a method for detecting the load GN, the load GN of the engine can be detected based on the depression amount of the accelerator pedal or the fuel injection amount.

The block diagram which shows schematic structure of the fuel-injection control apparatus of the internal combustion engine which concerns on this embodiment. The flowchart which shows the process sequence of the fuel-injection control apparatus of 1st Embodiment. It is explanatory drawing of the map for calculating | requiring steady temperature, Comprising: (a) is a figure which shows the case where a share ratio is in-cylinder injection: intake port = 10: 0, (b) is in-cylinder injection: intake port = 0: The figure which shows the case of 10. The flowchart which shows the process sequence of the fuel-injection control apparatus of 2nd Embodiment. 5 is a flowchart showing a processing procedure following the flowchart of FIG. 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel-injection control apparatus, 11 ... In-cylinder injection type internal combustion engine (internal combustion engine), 12 ... Cylinder, 16 ... Combustion chamber, 17 ... In-cylinder injector (in-cylinder injector), 20 ... Intake passage, 22 ... Intake Port injection injector (intake port injector), 24 ... catalyst, 30 ... electronic control unit (ECU), 36 ... CPU (injection mode changing means, temperature estimating means (first temperature estimating means, second temperature estimating means) , Fuel increase execution means), 37... ROM, 38.

Claims (4)

A fuel injection control device applied to an internal combustion engine in which a fuel injection mode using at least one of an in-cylinder injector that directly injects fuel into a cylinder and an intake passage injector that injects fuel into an intake passage is set Because
When it is determined that the temperature of the exhaust system component is equal to or higher than a predetermined temperature, the ratio of the fuel injection amount from the intake passage injector to the fuel injection amount from the in-cylinder injector is set as compared with the case where it is not. Injection mode changing means for changing the setting state of the injection mode so as to increase ;
Temperature estimation means for estimating the temperature of the exhaust system parts based on the setting state of the injection form and the engine operation state;
Based on the temperature of the exhaust system part estimated by the temperature estimation means, it is determined whether or not the exhaust system part is overheated, and the exhaust system is changed after the injection form is changed by the injection form changing means. Fuel increase execution means for increasing the fuel injection amount when it is determined that the temperature of the component is excessively high;
The fuel injection control device for an internal combustion engine, wherein the fuel injection by the fuel increase execution means is performed from the in-cylinder injector . A fuel injection control device applied to an internal combustion engine in which a fuel injection mode using at least one of an in-cylinder injector that directly injects fuel into a cylinder and an intake passage injector that injects fuel into an intake passage is set Because
When it is determined that the temperature of the exhaust system components is equal to or higher than a predetermined temperature while fuel is being injected only from the in-cylinder injector, the amount of fuel injected from the in-cylinder injector is determined from the intake passage injector. Injection mode changing means for changing the injection mode so as to inject ;
Temperature estimation means for estimating the temperature of the exhaust system parts based on the setting state of the injection form and the engine operation state;
Based on the temperature of the exhaust system component estimated by the temperature estimating means, it is determined whether or not the exhaust system component is overheated, and the exhaust system is changed after the injection form is changed by the injection form changing means. Fuel increase execution means for increasing the fuel injection amount when it is determined that the temperature of the component is excessively high;
The fuel injection control device for an internal combustion engine, wherein the fuel injection by the fuel increase execution means is performed from the in-cylinder injector . The temperature estimating means includes
  First temperature estimating means for estimating the temperature of the exhaust system component based on the engine operating state corresponding to the injection form before the change by the injection form changing means;
  Second temperature estimating means for estimating a temperature of the exhaust system component based on an engine operation state corresponding to the injection form after the change by the injection form changing means;
With
  By switching from the first temperature estimating means to the second temperature estimating means by the injection form changing means, the temperature of the exhaust system component is estimated.
The fuel injection control device for an internal combustion engine according to claim 1 or 2. The internal combustion engine according to any one of claims 1 to 3, wherein when the fuel injection by the fuel increase execution means is executed a plurality of times, the current increase amount is decreased as compared with the previous fuel increase amount. Fuel injection control device.

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