JP2012167618A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of setting the sharing ratio of a fuel injection quantity by two kinds of injectors without causing the thermal deterioration of a catalyst.SOLUTION: This engine ECU calculates a cylinder injection quantity qinjd (Step S2). Request fuel pressure Prreq of fuel supplied to the injector for cylinder injection is calculated based on an engine speed Ne and the engine load ratio KI (Step S3). Next, the engine ECU compares a difference dpr between the request fuel pressure Prreq and actual fuel pressure Prreal with a threshold value DPR0 determined in response to the catalyst bed temperature (Step S5), and calculates a guard value to the cylinder injection quantity qinjd based on an injection duration and the fuel pressure when a value dpr of the difference is larger than the threshold value DPR0 (YES in Step S5). The engine ECU substitutes the guard value in the cylinder injection quantity qinjd when determining that the cylinder injection quantity qinjd is larger than the guard value (YES in Step S8).

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus capable of injecting fuel into a cylinder and into an intake passage.

  2. Description of the Related Art Conventionally, a vehicle driven by an internal combustion engine has been known which includes an in-cylinder injector for injecting fuel into a cylinder and a port injector for injecting fuel into an intake port. .

  In a vehicle equipped with these two types of injectors, for example, stratified combustion in a low load operation region and homogeneous combustion in a high load operation region are realized, or predetermined fuel sharing is performed according to the operation state of the internal combustion engine. Fuel injection characteristics and output characteristics are improved by performing fuel injection at a rate.

  In such a control device for an internal combustion engine having two types of injectors, it is known to set a share ratio of the fuel injection amount by each injector in accordance with the fuel pressure of the high-pressure fuel supplied to the in-cylinder injector. (For example, refer to Patent Document 1).

  The control apparatus for an internal combustion engine described in Patent Document 1 includes an in-cylinder injector to which high-pressure fuel is supplied, an in-cylinder injector to which low-pressure fuel is supplied and injects fuel into an intake passage, and startup of the internal combustion engine. There is provided a sharing rate setting means for setting a sharing rate between the fuel injection amount by the in-cylinder injector and the fuel injection amount by the outside-cylinder injector with respect to the required fuel injection amount that is sometimes required.

  The sharing rate setting means sets the sharing rate of the fuel amount allocated to the in-cylinder injector according to the fuel pressure of the high-pressure fuel supplied to the in-cylinder injector. As a result, when the fuel pressure drop of the high-pressure fuel occurs and the atomization of the fuel injected from the in-cylinder injector deteriorates, the amount of fuel allocated to the in-cylinder injector is increased so that the atomization state However, good fuel was supplied to the cylinders to improve the startability of the internal combustion engine.

JP 2001-336439 A

  However, in the conventional control device for an internal combustion engine as described above, for the purpose of improving the startability of the internal combustion engine, the fuel injection amount is shared according to the fuel pressure of the high-pressure fuel supplied to the in-cylinder injector. Although the change of the rate is executed, the change in the end timing of the in-cylinder injection due to the difference between the required fuel pressure for the high-pressure fuel and the actual fuel pressure is not considered.

  Therefore, when the actual fuel pressure is lower than the required fuel pressure of the high-pressure fuel, the fuel amount allocated to the in-cylinder injector cannot be injected during the intake stroke of each cylinder, and continues to the intake stroke. There was a possibility that the fuel would continue to be injected during the compression stroke.

  For example, if the internal combustion engine is stopped immediately after traveling at a high load, vapor is generated in the high-pressure fuel system due to dead soak, and the actual fuel pressure with respect to the required fuel pressure is reduced. In particular, in a hybrid vehicle that uses an internal combustion engine and a rotating electric machine as drive sources, a situation in which the internal combustion engine stops, such as traveling by only the rotating electric machine, frequently occurs, which may cause a decrease in the actual fuel pressure due to vapor. Increased further.

  If the fuel injection continues after the intake stroke due to the decrease in the actual fuel pressure with respect to the required fuel pressure, it is introduced into the catalyst in an unburned state due to the diffusion deterioration of the fuel injected after the intake stroke. Further, afterburning of the unburned fuel occurs in the catalyst, and as a result, the catalyst may be thermally deteriorated due to overheating due to afterburning.

  The present invention has been made to solve such a problem, and provides an internal combustion engine control device capable of setting a share ratio of fuel injection amounts by two types of injectors without causing thermal deterioration of the catalyst. With the goal.

  In order to achieve the above object, the control apparatus for an internal combustion engine according to the present invention (1) injects fuel into a cylinder injection means for injecting fuel into a cylinder of the internal combustion engine and an intake passage for introducing outside air into the cylinder. A control device for an internal combustion engine, comprising: a port injection unit, wherein a total amount of fuel injected by the in-cylinder injection unit and the port injection unit is calculated, and is injected by the in-cylinder injection unit. A distribution setting means for setting the total fuel amount to be distributed at a predetermined distribution ratio, and the in-cylinder injection means. A fuel pressure determining means for determining whether or not a difference between a required fuel pressure required for the fuel to be supplied and an actual fuel pressure of the fuel supplied to the in-cylinder injection means is greater than or equal to a threshold value, and the fuel pressure determining means Required fuel pressure and above When it is determined that the difference from the fuel pressure is greater than or equal to a threshold value, the first fuel amount is restricted so as not to exceed a predetermined upper limit value, and the first fuel amount set by the distribution setting means Control means for adding the reduced fuel amount to the second fuel amount when the fuel amount is reduced to the predetermined upper limit value.

  With this configuration, in the case where the actual fuel pressure is lower than the required fuel pressure and there is a possibility that the fuel allocated to the in-cylinder injection unit may continue to be injected beyond the intake stroke, the second number allocated to the in-cylinder injection unit Therefore, the fuel injection by the in-cylinder injection means can be prevented from continuing until the compression stroke. Therefore, it is possible to suppress post-combustion caused by fuel injected beyond the intake stroke, and to prevent the catalyst installed in the exhaust passage of the internal combustion engine from being thermally deteriorated.

  Further, in the control device for an internal combustion engine according to (1) above, (2) further comprising catalyst temperature detection means for detecting a temperature of a catalyst for purifying exhaust gas exhausted from the internal combustion engine, wherein the fuel pressure determination means includes: The threshold value is lowered when the catalyst temperature detected by the catalyst temperature detecting means is high compared to when the catalyst temperature is low.

  With this configuration, the threshold value can be lowered when the catalyst temperature is high compared to when the catalyst temperature is low. Therefore, it is possible to reliably prevent the occurrence of afterburning as the catalyst temperature is higher, and to prevent the catalyst temperature from further rising and the catalyst from being thermally deteriorated.

  In the control device for an internal combustion engine according to the above (1) or (2), (3) the control means sets the fuel injection end timing by the in-cylinder injection means in accordance with the combustion state of the cylinder. The predetermined upper limit value is set based on the time from the fuel injection start timing to the fuel injection end timing by the in-cylinder injection unit and the fuel pressure of the fuel supplied to the in-cylinder injection unit. To do.

  With this configuration, fuel injection beyond the fuel injection timing can be prevented, so that afterburn caused by fuel injected after the intake stroke is suppressed, and the catalyst installed in the exhaust passage of the internal combustion engine is prevented from thermal deterioration. it can.

  The control apparatus for an internal combustion engine according to (3), further comprising: (4) a torque fluctuation detection unit that detects a torque fluctuation of the internal combustion engine, wherein the control unit detects the torque detected by the torque fluctuation detection unit. The fuel injection end timing is set to the advance side as the fluctuation increases.

  With this configuration, the fuel injection end timing is set so as to suppress the deterioration of the combustion state in each cylinder, so that it is possible to protect the catalyst from thermal deterioration while maintaining the combustion state in the cylinder in a good state. Become.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which can set the share ratio of the fuel injection amount by two types of injectors without generating the thermal deterioration of a catalyst can be provided.

It is a schematic block diagram which shows the control apparatus of the internal combustion engine which concerns on embodiment of this invention. It is a figure which shows the basic injection division ratio map which concerns on embodiment of this invention. It is a figure which shows the fuel-injection period which concerns on embodiment of this invention. It is a figure which shows the injection characteristic of the injector for cylinder injection which concerns on embodiment of this invention. It is a figure which shows the guard value map which concerns on embodiment of this invention. It is a flowchart for demonstrating the in-cylinder injection amount restriction | limiting process which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, a case will be described in which the control device for an internal combustion engine is applied to a vehicle equipped with a 4-cylinder gasoline engine.

  FIG. 1 is a schematic configuration diagram showing a control device for an internal combustion engine according to an embodiment of the present invention. As shown in FIG. 1, an engine 2 constituting the internal combustion engine of the present invention is mounted on a vehicle and includes four cylinders 6. These cylinders 6 are respectively connected to an intake manifold 4, and the intake manifold 4 is connected to a common surge tank 5.

  The surge tank 5 is connected to an intake pipe 10, and an air cleaner 12, an air flow meter 11, and a throttle valve 14 are disposed in the intake pipe 10.

  The throttle valve 14 is driven by an electric motor 13 and its opening degree is controlled in accordance with a signal output from an engine ECU (Electronic Control Unit) 8 described later.

  Further, each cylinder 6 is connected to an exhaust manifold 15, and this exhaust manifold 15 is connected to an exhaust pipe 16. The exhaust pipe 16 is provided with a catalyst device 17 having a three-way catalytic converter and an air-fuel ratio sensor 42.

  Each cylinder 6 is provided with an in-cylinder injector 19 for injecting fuel into the cylinder. Further, the intake manifold 4 constituting a part of the intake passage is provided with a port injection injector 20 for injecting fuel into the intake passage. Here, the in-cylinder injector 19 constitutes an in-cylinder injection unit according to the present invention, and the port injection injector 20 constitutes a port injection unit according to the present invention.

  The fuel injection amount and the injection timing by the in-cylinder injector 19 and the port injector 20 are controlled by the engine ECU 8. Further, as will be described later, the engine ECU 8 controls the injection ratio of the fuel injection amount in the injectors 19 and 20.

  The in-cylinder injector 19 is connected to a common fuel distribution pipe 21, and high pressure fuel is pumped to the fuel distribution pipe 21 from a high pressure fuel pump 23 driven by the power of the engine 2. ing. A check valve 22 is installed between the fuel distribution pipe 21 and the high-pressure fuel pump 23 to prevent back flow of fuel from the fuel distribution pipe 21 side to the high-pressure fuel pump 23 side.

  An electromagnetic spill valve 24 is installed in parallel with the high-pressure fuel pump 23, and the discharge side of the high-pressure fuel pump 23 is connected to the suction side via the electromagnetic spill valve 24. The opening degree of the electromagnetic spill valve 24 is controlled by the engine ECU 8. The smaller the opening degree, the larger the amount of fuel supplied from the high-pressure fuel pump 23 to the fuel distribution pipe 21. When fully opened, the fuel supply from the high-pressure fuel pump 23 to the fuel distribution pipe 21 is stopped.

  The port injection injector 20 is connected to a fuel distribution pipe 25 for low pressure. Both the fuel distribution pipe 25 and the high-pressure fuel pump 23 are connected to a low-pressure fuel pump 27 via a fuel pressure regulator 26.

  The low-pressure fuel pump 27 sucks fuel stored in the fuel tank 29 via the fuel filter 28 and pumps it to the fuel pressure regulator 26. The fuel pressure regulator 26 returns a part of the fuel discharged from the low pressure fuel pump 27 to the fuel tank 29 when the pressure of the fuel discharged from the low pressure fuel pump 27, that is, the fuel pressure becomes higher than a predetermined set value. Thus, the fuel pressure supplied to the port injector 20 is controlled to be equal to or lower than this set value.

  The engine ECU 8 includes a CPU (Central Processing Unit) 34, a RAM (Random Access Memory) 33, a ROM (Read Only Memory) 32, an input port 35, an output port 36, and the like connected to each other via a bidirectional bus 31. It is comprised by the microcomputer provided with. The CPU 34 performs output control of the engine 2 by performing signal processing according to a program stored in the ROM 32 in advance while using the temporary storage function of the RAM 33. A signal output from the output port 36 is transmitted to an actuator (not shown) or the like via an A / D converter.

  As will be described later, the engine ECU 8 according to the present embodiment constitutes an internal combustion engine control device, distribution setting means, fuel pressure determination means, torque fluctuation detection means, catalyst temperature detection means, and control means according to the present invention. To do.

  The engine ECU 8 is connected to the air flow meter 11, the water temperature sensor 38, the fuel pressure sensor 40, the air-fuel ratio sensor 42, the accelerator opening sensor 44, the rotation speed sensor 46, the fuel temperature sensor 48, and the catalyst temperature sensor 50. Signals output from these sensors are input via the input port 35.

  The air flow meter 11 measures the amount of air sucked into the intake pipe 10 and outputs a voltage corresponding to the amount of intake air as an output signal. The output signal of the air flow meter 11 is A / D converted. It is input to the input port 35 through the device.

  The fuel pressure sensor 40 is installed in the fuel distribution pipe 21 and outputs a voltage corresponding to the fuel pressure in the fuel distribution pipe 21 as an output signal. This output signal is sent via an A / D converter. Input to the input port 35. Therefore, the fuel pressure sensor 40 and the engine ECU 8 constitute fuel pressure detection means according to the present invention.

  The air-fuel ratio sensor 42 is constituted by a linear air-fuel ratio sensor that outputs, as an output signal, a voltage corresponding to the oxygen concentration of the exhaust gas and the concentration of the unburned component of the fuel in the exhaust pipe 16. The signal representing the fuel ratio is input to the input port 35 via the A / D converter.

  The water temperature sensor 38 is installed in the engine 2 and outputs a voltage corresponding to the cooling water temperature of the engine 2 as an output signal. This output signal outputs an A / D converter as a signal indicating the engine cooling water temperature. To the input port 35.

  The accelerator opening sensor 44 outputs a voltage corresponding to the amount of depression of the accelerator pedal 18 as an output signal, and this output signal is input to the input port 35 via the A / D converter.

  The rotation speed sensor 46 generates a pulse as an output signal for each predetermined rotation angle of the timing rotor installed on the crankshaft of the engine 2 and inputs the pulse to the input port 35 as a signal representing the engine rotation speed Ne. ing.

  The fuel temperature sensor 48 is installed in the fuel distribution pipe 21 and outputs a voltage corresponding to the fuel temperature in the fuel distribution pipe 21 as an output signal. This output signal is sent via an A / D converter. To the input port 35.

  The catalyst temperature sensor 50 is installed in the case of the catalyst device 17 and outputs a voltage corresponding to the temperature of the catalyst device 17, that is, the catalyst bed temperature, as an output signal. This output signal is A / D converted. It is input to the input port 35 through the device. Therefore, the engine ECU 8 according to the present embodiment constitutes the catalyst temperature detecting means according to the present invention.

  The ROM 32 of the engine ECU 8 stores a fuel injection amount map in which the intake air amount and the engine speed Ne are associated with the total fuel injection amount injected from the in-cylinder injector 19 and the port injector 20. Has been. When the engine ECU 8 acquires a signal representing the intake air amount from the air flow meter 11 and a signal representing the engine rotational speed Ne from the rotational speed sensor 46, the engine ECU 8 refers to the fuel injection amount map, and the in-cylinder injector 19 and The total fuel injection amount injected from the port injector 20 is calculated.

  Further, the engine ECU 8 calculates a deviation between the actual air-fuel ratio input from the air-fuel ratio sensor 42 and the target air-fuel ratio stored in the ROM 32 so that the deviation between the actual air-fuel ratio and the target air-fuel ratio approaches zero. Feedback control is executed. Further, the engine ECU 8 calculates a learning value by integrating the calculated deviation for a predetermined time, and stores it in the RAM 33.

  That is, the engine ECU 8 according to the present embodiment executes PI feedback control that calculates the proportional term and the integral term as the learning value from the actual air-fuel ratio and the target air-fuel ratio and performs feedback control. The engine ECU 8 may further calculate a differential term based on the actual air-fuel ratio and the target air-fuel ratio, and execute PID feedback control using the proportional term, the integral term, and the differential term.

  In this PI feedback control, the engine ECU 8 calculates the fuel correction amount dQ as follows, and corrects the total fuel amount required at the next fuel injection, that is, the required injection amount qinjall by the fuel correction amount dQ.

dQ = Qp + Qi (1)
Here, Qp is a proportional term and Qi is an integral term.

The proportional term Qp is calculated as follows.
Qp = Kp · ΔQ (2)
Here, Kp is a proportional gain. ΔQ is the difference between the amount of fuel for setting the actual air-fuel ratio to the target air-fuel ratio and the current amount of fuel burned in the cylinder 6. The amount of fuel burned in the cylinder 6 is calculated by dividing the detected value of the intake air amount by the detected value of the air-fuel ratio.

The integral term Qi is calculated as follows.
Qi = Qi + Ki.ΔQ (3)
Here, Ki is an integral gain.

  When the engine ECU 8 calculates the proportional term Qp and the integral term Qi based on the above formulas (2) and (3), respectively, these values are substituted into the formula (1) to calculate the fuel correction amount dQ. It has become. Then, the engine ECU 8 corrects the total fuel injection amount calculated by the fuel injection amount map with the fuel correction amount dQ, and injects from the in-cylinder injector 19 and the port injection injector 20 at the next fuel injection. The required injection amount qinjall is calculated.

  Further, when the engine ECU 8 calculates the total required injection amount qinjall that is injected from the in-cylinder injector 19 and the port injector 20, the in-cylinder injector is in accordance with an injection distribution ratio that is obtained by a fuel distribution process that will be described later. 19 and the port injection injector 20 are calculated, and energization is performed to solenoids that displace the needles of the injectors 19 and 20 in the axial direction by a predetermined lift amount. It is like that. The relationship between the energization time for the solenoid and the amount of fuel injected in each of the injectors 19 and 20 is obtained in advance by experimental measurement and is stored in the ROM 32 as a map. Therefore, the engine ECU 8 according to the present embodiment constitutes a control means according to the present invention. The axial direction means the longitudinal direction of the needle.

  Hereinafter, a characteristic configuration of the engine ECU 8 constituting the control device for the internal combustion engine according to the present embodiment will be described with reference to FIGS. 1 to 4.

  When the engine ECU 8 calculates the required injection amount qinjall injected from the in-cylinder injector 19 and the port injector 20 as described above, it is based on the engine load factor Kl and the engine speed Ne required for the engine 2. The ratio of distributing the required fuel amount qinjall to the in-cylinder injection amount qinjd injected by the in-cylinder injector 19 and the port injection amount qinjp injected by the port injector 20 is calculated. That is, the in-cylinder injection amount qinjd according to the present embodiment constitutes the first fuel amount according to the present invention, and the port injection amount qinjp constitutes the second fuel amount according to the present invention.

  Here, the fuel distribution process for the in-cylinder injector 19 and the port injector 20 executed by the engine ECU 8 will be described.

  The engine ECU 8 corrects the total fuel amount calculated by the fuel injection amount map by the fuel correction amount dQ calculated by the above equation (1), and calculates the required injection amount qinjall. Then, the calculated required injection amount qinjall is distributed to the in-cylinder injector 19 and the port injector 20 at a predetermined injection ratio, and the in-cylinder injection amount assigned to the in-cylinder injector 19 is qinjd, The port injection amount assigned to the port injection injector 20 is set to qinjp.

  This injection ratio is stored in the ROM 32 as a basic injection ratio map (see FIG. 2) associated with the engine load factor Kl and the engine speed Ne. Further, the engine load factor Kl is calculated based on the accelerator opening degree and the engine speed Ne output by the accelerator opening sensor 44 and the rotation speed sensor 46. Therefore, the engine ECU 8 according to the present embodiment constitutes a distribution setting unit according to the present invention.

  FIG. 2 is a diagram showing a basic injection ratio map according to the embodiment of the present invention. In the basic injection ratio map, the region where the engine speed Ne is higher than Ne1 and the region where the engine load factor Kl is higher than Kl2 are determined as direct injection regions. In this region, fuel from only the in-cylinder injector 19 is used. Is to be injected. Further, the region where the engine load factor Kl is lower than Kl1 and the engine speed Ne is lower than Ne1 is defined as a port injection region in which fuel is injected only by the port injector 20.

  Further, the region where the engine load factor is in the range from Kl1 to Kl2 and the engine speed is Ne1 or less is defined as the direct injection and port injection region, and the basics according to the engine load factor and the engine speed The spraying rate is determined. As is well known, the in-cylinder injector 19 contributes to an increase in output performance, and the port injector 20 contributes to the uniformity of the air-fuel mixture. Therefore, with regard to the basic injection ratio, the two types of injectors 19 and 20 having different characteristics as described above are selectively used according to the engine speed and the engine load ratio, thereby improving fuel efficiency and acceleration. Is set to

  Note that the basic blowing rate map shown in FIG. 2 is merely an example, and for example, all the regions may be defined by direct injection and port injection regions. Further, the direct injection region or the port injection region may be replaced with the direct injection and port injection region.

  Next, in-cylinder injection amount restriction control executed by the engine ECU 8 will be described.

  The engine ECU 8 sets the required fuel pressure Prreq of the high-pressure fuel supplied to the in-cylinder injector 19 based on the engine speed Ne and the engine load factor Kl, and adjusts the opening of the electromagnetic spill valve 24 to Control is performed so that the fuel pressure Prreal follows the required fuel pressure Prreq set. The required fuel pressure Prreq is generally set to a higher value as the engine speed Ne or the engine load factor Kl is larger.

  When the engine ECU 8 obtains a signal representing the actual fuel pressure Prreal from the fuel pressure sensor 40, the engine ECU 8 calculates a value dpr of the difference between the actual fuel pressure Prreal and the set required fuel pressure Prreq, and the difference value dpr is a predetermined threshold value. It is determined whether or not it is equal to or higher than DPR0. That is, the engine ECU 8 according to the present embodiment constitutes a fuel pressure determination unit according to the present invention.

  Here, when the difference value dpr is large, it indicates that the actual fuel pressure Prreal is lower than the required fuel pressure Prreq. Under such circumstances, because the actual fuel pressure Prreal is low, the set in-cylinder injection amount qinjd is all injected as compared with the case where the actual fuel pressure Prreal matches the required fuel pressure Prreq. The time will be longer.

  Therefore, as shown in FIG. 3, after the fuel injection duration time passes the intake stroke and continues until the injection end timing 61, afterburning occurs. Therefore, when the value dpr of the difference between the required fuel pressure Prreq and the actual fuel pressure Prreal exceeds the threshold value DPR0, a preset injection value is set by setting a guard value for the in-cylinder injection amount qinjd as will be described later. At the end time 62, the injection of the in-cylinder injection amount qinjd distributed to the in-cylinder injector 19 is ended.

  The threshold value DPR0 is set based on the catalyst bed temperature detected by the catalyst temperature sensor 50.

  Specifically, when the catalyst bed temperature of the catalyst device 17 is high, the catalyst bed temperature further rises due to the occurrence of afterburning and becomes overheated, and the catalyst device 17 may be thermally deteriorated. For this reason, when the catalyst bed temperature is high, the threshold value DPR0 is set low to reliably prevent afterburning.

  On the other hand, when the catalyst bed temperature is low, even if afterburning occurs, the possibility that the catalyst device 17 is thermally deteriorated is reduced. Therefore, when the catalyst bed temperature is low, the threshold value DPR0 is set high. The engine ECU 8 stores in advance in the ROM 32 a threshold map that is associated with the threshold DPR0 so that the threshold DPR0 decreases as the catalyst bed temperature detected by the catalyst temperature sensor 50 increases, and a signal that indicates the catalyst bed temperature from the catalyst temperature sensor 50. Is obtained, the threshold value DPR0 is set with reference to the threshold value map.

  Further, when the engine ECU 8 determines that the difference value dpr is equal to or greater than the threshold value DPR0, the in-cylinder injection amount qinjd to be injected by the in-cylinder injector 19 is limited by the guard value qinjdguard.

  The guard value qinjdguard is calculated based on the injection start timing and the injection end timing by the in-cylinder injector 19 and the fuel pressure of the high-pressure fuel supplied to the in-cylinder injector 19 as follows.

  First, the engine ECU 8 sets an injection start time by the in-cylinder injector 19. The injection start timing is set according to the engine speed Ne of the engine 2 and the engine load factor Kl required for the engine 2. The association between the engine speed Ne, the engine load factor Kl, and the injection start time is obtained in advance by experimental measurement, and is stored in the ROM 32 in advance as a two-dimensional injection start time map.

  Therefore, the engine ECU 8 inputs a signal representing the engine speed Ne from the speed sensor 46 and calculates the engine load factor Kl from the intake air amount detected by the air flow meter 11 and the engine speed Ne and stores it in the ROM 32. The injection start timing by the in-cylinder injector 19 is calculated with reference to the injection start timing map.

  The engine ECU 8 stores in advance in the ROM 32 an engine load map that associates the intake air amount with the engine load factor Kl. The correspondence between the intake air amount and the engine load factor Kl is obtained in advance by experimental measurement. The engine load factor Kl may be calculated by a known method such as a method of calculating from the required injection amount qinjall instead of the intake air amount.

  Further, the injection end timing is determined according to the combustion state in the cylinder 6. Specifically, it is determined in advance by experimental measurement so that torque fluctuation does not occur in each cylinder 6. For example, the engine speed Ne is sampled every 10 ° CA, and a 10 ° CA time that is a unit angle rotation time required for the unit angle rotation is calculated. Further, missing tooth correction is performed for the 10 ° CA time. Then, the corrected waveform is converted into instantaneous Ne every 30 ° CA time, and the filtering process is executed to remove the high frequency component and the low frequency component that are out of the rotation variation frequency region, and the instantaneous variation that is the rotation variation component at each time point. The torque value is calculated. Then, as a result of comparing the instantaneous torque values of the respective cylinders 6 or obtaining a change over time, when it is determined that torque fluctuation has occurred, the injection end timing is corrected to the advance side.

  The setting of the injection end timing according to the torque fluctuation is executed by the engine ECU 8 based on the engine speed Ne input from the speed sensor 46 while the engine 2 is driven, instead of being determined in advance by experimental measurement. May be. Further, the engine ECU 8 executes known injection end timing control while the engine 2 is being driven, and the preset injection end timing as described above is retarded or advanced depending on whether knocking has occurred or not. Correction is made to the corner side. Therefore, the engine ECU 8 according to the present embodiment constitutes a torque fluctuation detecting means according to the present invention.

  Further, when the engine ECU 8 calculates the injection continuation time from the injection start timing to the injection end timing, the engine ECU 8 acquires a signal representing the actual fuel pressure Prereal at the injection start timing from the fuel pressure sensor 40, and the actual fuel pressure Prereal and the injection continuation time The guard value qinjdguard is calculated based on the above. That is, the guard value qinjdguard according to the present embodiment constitutes a predetermined upper limit value according to the present invention.

  Here, the relationship between the valve opening time of the in-cylinder injector 19 and the in-cylinder injection amount qinjd at a predetermined reference fuel pressure is associated in advance as an injector characteristic map as shown in FIG. The in-cylinder injection amount qinjd increases as the actual fuel pressure Prreal is higher than the reference fuel pressure, and decreases as the valve opening time is constant. Therefore, when calculating the guard value qinjdguard, the engine ECU 8 first determines the in-cylinder injection amount qinjd at the reference fuel pressure based on the calculated injection duration and the injector characteristic map. Then, this value is corrected by the actual fuel pressure Prereal detected by the fuel pressure sensor 40 and used as the guard value qinjdguard.

  The engine ECU 8 stores a guard value map in which the engine speed Ne and the guard value qinjdguard are associated with each other as shown in FIG. 5 in the ROM 32 in advance, and a signal representing the engine speed Ne is sent from the speed sensor 46. When input, the guard value injdguard may be calculated with reference to the guard value map.

  Further, the engine ECU 8 determines whether or not the in-cylinder injection amount qinjd allocated to the in-cylinder injector 19 is larger than the guard value qinjdguard. When the engine ECU 8 determines that the in-cylinder injection amount qinjd is larger than the guard value qinjdguard, the engine ECU 8 guards the in-cylinder injection amount with the guard value qinjdguard. The difference between the in-cylinder injection amount qinjd and the guard value qinjdguard is added to the port injection amount qinjp assigned to the port injection injector 20.

  On the other hand, when the engine ECU 8 determines that the difference value dpr between the actual fuel pressure Prreal and the required fuel pressure Prreq is equal to or less than the threshold value DPR0, the engine ECU 8 sets the maximum fuel injection amount QDMAX that can be injected from the in-cylinder injector 19 as a guard value. Substitute into qinjdguard.

  Further, the engine ECU 8 causes the in-cylinder injection amount qinjd of fuel calculated as described above to be injected by the in-cylinder injector 19 and causes the port injection amount qinjp of fuel to be injected by the port injection injector 20. Here, the engine ECU 8 sets the valve opening time of the in-cylinder injector 19 based on the above-described injector characteristic map in order to inject the fuel of the calculated in-cylinder injection amount qinjd from the in-cylinder injector 19. At the same time, the valve opening time is corrected according to the actual fuel pressure Prereal detected by the fuel pressure sensor 40. At this time, since the in-cylinder injection amount qinjd is limited by the guard value qinjdguard, even when the actual fuel pressure Prreal is lower than the required fuel pressure Prreq, the in-cylinder injector 19 is closed when the injection end timing is reached. 62 (see FIG. 3) is not exceeded.

  Next, the operation of the in-cylinder injection amount restriction control according to the embodiment of the present invention will be described.

  FIG. 6 is a flowchart for illustrating in-cylinder injection amount restriction control according to the embodiment of the present invention. The following processing is executed at predetermined time intervals by the CPU 34 constituting the engine ECU 8, and a program that can be processed by the CPU 34 is realized.

  First, the engine ECU 8 calculates a required injection amount qinjall (step S1). Specifically, the engine ECU 8 calculates the engine speed Ne and the engine load factor Kl based on signals input from the speed sensor 46 and the air flow meter 11. When the required injection amount qinjall is calculated based on the engine speed Ne and the engine load factor Kl, the required injection amount is corrected by the feedback control described above.

  Next, the engine ECU 8 calculates an in-cylinder injection amount qinjd (step S2). Specifically, the engine ECU 8 calculates the required injection amount qinjall and the in-cylinder injection amount qinjd and the port injection based on the engine speed Ne and the engine load factor Kl calculated in step S1 and the basic injection ratio map shown in FIG. Distribute to quantity qinjp.

  Next, the engine ECU 8 calculates the required fuel pressure Prreq of the fuel supplied to the in-cylinder injector 19 based on the engine speed Ne and the engine load factor Kl calculated in step S1 (step S3).

  Next, when the engine ECU 8 obtains a signal representing the actual fuel pressure Prreal of the fuel supplied to the in-cylinder injector 19 from the fuel pressure sensor 40, the engine ECU 8 sets the difference value dpr from the required fuel pressure Prreq calculated in step S3. Calculate (step S4).

  Next, when the engine ECU 8 acquires a signal representing the catalyst bed temperature of the catalyst device 17 and sets the threshold value DPR0 by referring to the threshold map, the difference value dpr calculated in step S4 and the set threshold value DPR0 are set. Are compared (step S5).

  If the engine ECU 8 determines that the difference value dpr is larger than the threshold value DPR0 (YES in step S5), the process proceeds to step S6. On the other hand, if it is determined that the difference value dpr is less than or equal to the threshold value DPR0, the process proceeds to step S7.

  When the routine proceeds to step S6, the engine ECU 8 calculates the injection start timing based on the engine speed Ne and the engine load factor Kl of the engine 2 as described above, and sets the injection end timing based on the combustion state in the cylinder 6. When calculated, a guard value qinjdguard for the in-cylinder injection amount qinjd is calculated based on the injection duration time and the actual fuel pressure Prereal.

  On the other hand, when the routine proceeds to step S7, the engine ECU 8 sets the maximum fuel amount QDMAX that can be injected by the in-cylinder injector 19 as the guard value qinjdguard.

  Next, the engine ECU 8 compares the in-cylinder injection amount qinjd calculated in step S2 with the guard value qinjdguard set in step S6 or step S7 (step S8).

  If the engine ECU 8 determines that the in-cylinder injection amount qinjd is larger than the guard value qinjdguard (YES in step S8), the engine ECU 8 proceeds to step S9 and substitutes the guard value qinjdguard for the in-cylinder injection amount qinjd. As a result, the in-cylinder injector 19 injects fuel of the in-cylinder injection amount qinjd limited by the guard value qinjdguard.

  On the other hand, when the engine ECU 8 determines that the in-cylinder injection amount qinjd is equal to or less than the guard value qinjdguard (NO in step S8), the engine ECU 8 proceeds to step S10 without limiting the in-cylinder injection amount qinjd by the guard value qinjdguard. .

  Next, the engine ECU 8 calculates a port injection amount qinjp (step S10). Specifically, the engine ECU 8 calculates the port injection amount qinjp by subtracting the in-cylinder injection amount qinjd calculated in step S9 from the required injection amount qinjall calculated in step S1.

  As described above, in the control apparatus for an internal combustion engine according to the embodiment of the present invention, the actual fuel pressure Prreal is lower than the required fuel pressure Prreq, and the fuel allocated to the in-cylinder injector 19 is compressed beyond the intake stroke. If there is a possibility of continuing to the stroke, the in-cylinder injection amount qinjd assigned to the in-cylinder injector 19 can be reduced, so that the fuel injection by the in-cylinder injector 19 is performed as an intake air such as a compression stroke. It is possible to prevent the continuation of the process after the process. Therefore, afterburning caused by fuel injection after the intake stroke can be suppressed, and the catalyst device 17 installed in the exhaust pipe 16 of the engine 2 can be prevented from being thermally deteriorated.

  Further, when the catalyst temperature is high, the threshold value DPR0 can be made lower than when the catalyst temperature is low. Therefore, it is possible to reliably prevent the occurrence of afterburning as the catalyst temperature is higher, and to prevent the catalyst temperature from further rising and the catalyst device 17 from being thermally deteriorated.

  Further, since fuel injection exceeding the fuel injection timing can be prevented, afterburning caused by fuel injected after the intake stroke is suppressed, and the catalytic device 17 installed in the exhaust pipe 16 of the engine 2 is thermally deteriorated. Can be prevented.

  Further, since the fuel injection end timing is set so as to suppress the deterioration of the combustion state in each cylinder 6, it is possible to protect the catalyst device 17 from thermal deterioration while maintaining the combustion state in the cylinder 6 in a good state. It becomes possible.

  In the above description, the case where the control device according to the present embodiment is mounted on a vehicle using engine 2 as a drive source has been described. However, the present invention is not limited to this, and the engine and motor generator are used as drive sources. The control device according to the present embodiment may be mounted on the hybrid vehicle. In this case, since the engine frequently stops, the hybrid vehicle is more likely to reduce the fuel pressure due to the occurrence of vapor due to dead soak, but the injection is performed by executing the in-cylinder injection amount limiting control described above. It is possible to prevent the phenomenon that the end timing is delayed and the afterburning occurs, and the thermal deterioration of the catalyst device can be suppressed.

  In the above description, the case where the control device according to the present embodiment is applied to a vehicle equipped with a gasoline engine has been described. However, the present invention is not limited to this, and a vehicle equipped with another internal combustion engine such as a diesel engine. It may be applied to.

  As described above, the control device according to the present invention has an effect that it is possible to set the share of the fuel injection amount by the two types of injectors without causing thermal degradation of the catalyst. This is useful for a control device for an internal combustion engine capable of injecting fuel.

2 engine 6 cylinder 8 engine ECU
11 Air Flow Meter 14 Throttle Valve 15 Exhaust Manifold 16 Exhaust Pipe 17 Catalytic Device 18 Accelerator Pedal 19 In-Cylinder Injector 20 Port Injector 32 ROM
33 RAM
34 CPU
38 Water temperature sensor 40 Fuel pressure sensor 42 Air-fuel ratio sensor 44 Accelerator opening sensor 46 Revolution sensor 48 Fuel temperature sensor 50 Catalyst temperature sensor

Claims (4)

A control device for an internal combustion engine comprising: an in-cylinder injection unit that injects fuel into a cylinder of the internal combustion engine; and a port injection unit that injects fuel into an intake passage that introduces outside air into the cylinder.
A total amount of fuel injected by the in-cylinder injection unit and the port injection unit is calculated, and a first fuel amount injected by the in-cylinder injection unit and a second fuel amount injected by the port injection unit A distribution setting means for setting the total fuel amount to be distributed at a predetermined distribution rate;
Fuel pressure determination means for determining whether or not a difference between a required fuel pressure required for the fuel supplied to the in-cylinder injection means and an actual fuel pressure of the fuel supplied to the in-cylinder injection means is equal to or greater than a threshold value; ,
When the fuel pressure determination means determines that the difference between the required fuel pressure and the actual fuel pressure is greater than or equal to a threshold, the first fuel amount is limited so as not to exceed a predetermined upper limit value, and the distribution setting is performed. Control means for adding the reduced fuel amount to the second fuel amount when the first fuel amount set by the means is reduced to the predetermined upper limit value. A control device for an internal combustion engine. Further comprising catalyst temperature detection means for detecting the temperature of the catalyst for purifying the exhaust discharged from the internal combustion engine,
2. The control device for an internal combustion engine according to claim 1, wherein the fuel pressure determination unit lowers the threshold value when the catalyst temperature detected by the catalyst temperature detection unit is high compared to a case where the catalyst temperature is low. .   The control means sets the fuel injection end timing by the in-cylinder injection means according to the combustion state of the cylinder, the time from the fuel injection start timing by the in-cylinder injection means to the fuel injection end timing, The control device for an internal combustion engine according to claim 1 or 2, wherein the predetermined upper limit value is set based on a fuel pressure of fuel supplied to the in-cylinder injection means. Torque fluctuation detecting means for detecting torque fluctuation of the internal combustion engine;
4. The control apparatus for an internal combustion engine according to claim 3, wherein the control means sets the fuel injection end timing to an advance side as the torque fluctuation detected by the torque fluctuation detection means increases.

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