JP5040902B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that performs injection control on an injector.

  Conventionally, a vehicle driven by an internal combustion engine has an exhaust purification catalyst and an air-fuel ratio sensor in the exhaust passage of the internal combustion engine, and the detection result detected by the air-fuel ratio sensor is improved so that the exhaust purification performance of the exhaust purification catalyst is enhanced. On the basis of this, a control device for controlling the injection of fuel to the internal combustion engine to bring the air-fuel ratio of the internal combustion engine closer to the target air-fuel ratio is mounted.

  As this type of control device, an air-fuel ratio sensor is provided upstream of the exhaust purification catalyst, and an air-fuel ratio feedback control is performed according to the oxygen concentration of the exhaust gas detected by the air-fuel ratio sensor ( For example, see Patent Document 1).

  The conventional control device described in Patent Document 1 executes feedback control for correcting the injection amount of fuel injected into the cylinder of the internal combustion engine in accordance with the oxygen concentration of the exhaust gas detected by the air-fuel ratio sensor. Thus, the actual air-fuel ratio is controlled to approach the target air-fuel ratio.

  Further, the conventional control device described in Patent Document 1 includes an in-cylinder injector that injects fuel into a cylinder of an internal combustion engine, and an in-port injection that injects fuel into an intake port connected to the cylinder. And an injection amount in the in-port injector and the in-cylinder injector based on the engine load factor and the engine speed of the internal combustion engine. It was.

In this conventional control device, when the fuel injection amount calculated for the in-port injector and the in-cylinder injector is less than the minimum injection amount that can be injected by these injectors, the calculated fuel Instead of the injection amount, the minimum injection amount of fuel is injected.
JP 2007-32328 A

  However, the conventional control device for an internal combustion engine as described above does not take into consideration that the minimum injection amount of the in-cylinder injector changes due to an external factor. Therefore, in the state where the minimum injection amount set for the in-cylinder injector is higher than the actual minimum injection amount, even when the injection amount smaller than the set minimum injection amount should be injected, the set minimum amount Since the in-cylinder injection amount injector is controlled so that the injection amount is injected, the air-fuel ratio in the internal combustion engine may shift to the rich side. Conversely, when the minimum injection amount set for the in-cylinder injector is lower than the actual minimum injection amount, the in-cylinder injection is performed so that the set minimum injection amount or a fuel amount in the vicinity thereof is injected. When the injector for injection is controlled, the fuel is not injected because it is below the actual minimum injection amount, and the air-fuel ratio in the internal combustion engine may shift to the lean side.

  For this reason, in any case, the actual air-fuel ratio deviates from the target air-fuel ratio due to a decrease in fuel injection accuracy, and as a result, exhaust purification performance may deteriorate or drivability may deteriorate.

  The present invention has been made to solve such a problem, and at least an internal combustion engine in which fuel is injected into a cylinder has higher fuel injection accuracy than conventional ones and can improve exhaust purification performance and drivability. An object of the present invention is to provide an engine control device.

In order to achieve the above object, an internal combustion engine control apparatus according to an aspect of the present invention includes (1) in-cylinder injection means for injecting fuel into a cylinder of the internal combustion engine, engine speed of the internal combustion engine, and in-cylinder The fuel amount calculating means for calculating the fuel amount injected into the cylinder by the in-cylinder injection means based on the air amount sucked into the cylinder, and the fuel amount calculated by the fuel amount calculating means are injected A control means for controlling the in-cylinder injection means, comprising: a fuel pressure detection means for detecting a fuel pressure of fuel supplied to the in- cylinder injection means; and the in-cylinder injection means. A temperature difference detecting means for detecting a temperature difference between the constituting injection valve and a main body that accommodates the injection valve so as to be movable in the axial direction, a fuel pressure of the fuel detected by the fuel pressure detecting means, and a temperature difference detecting means and said detected temperature difference, And a minimum value setting means for setting a minimum value of the amount of fuel injected from the in-cylinder injection means. The control means has the fuel amount calculated by the fuel amount calculation means as the minimum value setting means. If it is smaller than the minimum value set by the above, the in-cylinder injection means is controlled so that the minimum amount of fuel is injected.

With this configuration, it is possible to set the minimum value of the amount of fuel injected from the in-cylinder injection unit based on the controllable range of the fuel injection amount that changes depending on the fuel pressure, so the amount of fuel to be injected into the cylinder is small Even in this case, it is possible to control the in-cylinder injection unit so that the fuel amount actually injected into the cylinder approaches the fuel amount calculated by the fuel amount calculation unit. As a result, exhaust purification performance can be improved and drivability can be improved. Further, when the temperature difference between the injection valve and the main body that houses the injection valve increases, only the main body expands, so that the minute injection becomes unstable and the injection accuracy decreases, but in the control device for an internal combustion engine according to the present invention, Since the minimum value of the fuel amount is set according to the temperature difference between the injection valve and the main body, fuel injection that becomes unstable in the fuel injection control can be prevented.

In order to achieve the above object, a control apparatus for an internal combustion engine according to another aspect of the present invention includes (2) in-cylinder injection means for injecting fuel into a cylinder of the internal combustion engine, and an intake passage connected to the cylinder. Port injection means for injecting fuel into the cylinder, and the total amount of fuel injected from the in-cylinder injection means and the port injection means based on the engine speed of the internal combustion engine and the amount of air sucked into the cylinder Control of an internal combustion engine comprising: a fuel amount calculation means for calculating; and a control means for controlling the in-cylinder injection means and the port injection means so that the total fuel amount calculated by the fuel amount calculation means is injected A distribution calculating means for calculating a ratio of distributing the total fuel amount to the in-cylinder injection means and the port injection means based on an engine load factor and an engine speed required for the internal combustion engine. When And fuel pressure detecting means for detecting a fuel pressure of the fuel supplied to the cylinder injection means, detecting a temperature difference between the body for movably housing the injection valve and the injection valve which constitutes the cylinder injection means axially A minimum fuel amount injected from the in-cylinder injection unit according to the temperature difference detection unit, the fuel pressure detected by the fuel pressure detection unit, and the temperature difference detected by the temperature difference detection unit A minimum value setting means for setting a value, and a fuel amount corresponding to the proportion distributed to the in-cylinder injection means calculated by the distribution calculation means is smaller than the minimum value set by the minimum value setting means. The fuel amount corresponding to the ratio to be distributed to the in-cylinder injection means is set to the minimum value, and the fuel amount of the minimum value and the ratio to be distributed to the in-cylinder injection means calculated by the distribution calculation means. fuel The fuel amount correction means for correcting the fuel amount injected by the in-cylinder injection means and the port injection means by taking the difference between the fuel amount and the fuel amount corresponding to the ratio of distribution to the port injection means The control means controls the in-cylinder injection means and the port injection means so that the fuel amount corrected by the fuel amount correction means is injected.

With this configuration, it is possible to set the minimum value of the amount of fuel injected from the in-cylinder injection unit based on the controllable range of the fuel injection amount that changes depending on the fuel pressure, so the amount of fuel to be injected into the cylinder is small Even in this case, it is possible to control the in-cylinder injection unit so that the fuel amount actually injected into the cylinder approaches the fuel amount calculated by the fuel amount calculation unit. Further, when the amount of fuel injected by the in-cylinder injection unit calculated by the distribution calculation unit is below the minimum value, the amount of fuel injected by the in-cylinder injection unit is maintained at the minimum value, and the calculated fuel Since the difference between the amount and the minimum value is subtracted from the amount of fuel injected by the port injection means, the total amount of fuel injected can be matched with the calculated value. As a result, exhaust purification performance can be improved and drivability can be improved. Further, when the temperature difference between the injection valve and the main body that houses the injection valve increases, only the main body expands, so that the minute injection becomes unstable and the injection accuracy decreases, but in the control device for an internal combustion engine according to the present invention, Since the minimum value of the fuel amount is set according to the temperature difference between the injection valve and the main body, fuel injection that becomes unstable in the fuel injection control can be prevented.

  Further, in the control device for an internal combustion engine according to the above (1) or (2), (3) the minimum value setting means is higher when the fuel pressure detected by the fuel pressure detection means is higher than when the fuel pressure is lower. The minimum value is increased.

  With this configuration, when the fuel pressure of the fuel supplied to the in-cylinder injection unit is high, the minimum injection amount that can be controlled by the in-cylinder injection unit is larger than when the fuel pressure is low. Only the area that can be controlled by the in-cylinder injection means can be used. Further, when the fuel pressure of the fuel is low, the in-cylinder injection means can be controlled to a range where the fuel injection amount is small compared to the case where the fuel pressure is high, so the fuel amount and the fuel amount actually injected by reducing the minimum value The fuel amount calculated by the calculating means can be made closer to that of the prior art.

Further, in the control device for an internal combustion engine according to the above (1) or (2) , (4) the minimum value setting means is compared with a small case when the temperature difference detected by the temperature difference detection means is large. Then, the minimum value is increased.

  With this configuration, when the temperature difference between the injection valve constituting the in-cylinder injection means and the main body is large, the injection accuracy at the time of the minute injection is lower than when the temperature is small. Only an area with good injection accuracy in the injection means can be used. In addition, when the temperature difference between the injection valve and the main body is small, the in-cylinder injection means can be controlled to a range where the fuel injection amount is small compared to the case where it is large, so that the actual injection is performed by reducing the minimum value. The fuel amount and the fuel amount calculated by the fuel amount calculating means can be made closer than before.

  It is possible to provide a control apparatus for an internal combustion engine that can improve the fuel injection accuracy and improve exhaust purification performance and drivability in an internal combustion engine in which fuel is injected into at least a cylinder.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
A control apparatus for an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. 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 four-cylinder engine.

FIG. 1 is a schematic configuration diagram illustrating a control device for an internal combustion engine according to a first 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. A three-way catalytic converter 17 and an air-fuel ratio sensor 42 are installed in the exhaust pipe 16.

  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 that are 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. The signal output from the output port 36 is transmitted to an actuator (not shown) or the like via the A / D converter 47.

  As will be described later, the engine ECU 8 according to the present embodiment includes a control device for an internal combustion engine, fuel amount calculation means, distribution calculation means, fuel pressure detection means, temperature difference detection means, fuel amount correction means, The minimum value setting means and the control means are configured.

  The engine ECU 8 is connected to an air flow meter 11, a water temperature sensor 38, a fuel pressure sensor 40, an air-fuel ratio sensor 42, an accelerator opening sensor 44, a rotation speed sensor 46, and a fuel temperature sensor 48, and outputs from these sensors. The received signal is 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 via the device 37.

  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 output from the A / D converter 41. 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 43.

  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 is an A / D converter 39 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 45. .

  The rotational speed sensor 46 generates a pulse as an output signal at every predetermined rotational angle of a timing rotor (not shown) installed on the crankshaft of the engine 2 and inputs the pulse to the input port 35 as a signal representing the engine rotational speed. It has become.

  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 an A / D converter. 49 to the input port 35.

  The ROM 32 of the engine ECU 8 stores a fuel injection amount map in which the intake air amount and the engine speed are associated with the total fuel injection amount injected from the in-cylinder injector 19 and the port injector 20. ing. When the engine ECU 8 obtains a signal representing the intake air amount from the air flow meter 11 and a signal representing the engine speed 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 port The total fuel injection amount injected from the injector 20 for injection 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 injection amount Qall at the next fuel injection 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 total fuel amount Qall is calculated.

  Therefore, the engine ECU 8, the air flow meter 11, and the rotational speed sensor 46 according to the present embodiment are based on the engine rotational speed of the engine 2 and the amount of air sucked into the cylinder 6 according to the present invention. 19 and a fuel amount calculating means for calculating the total fuel amount Qall injected from the port injector 20.

  Further, when the engine ECU 8 calculates the total fuel amount Qall injected from the in-cylinder injector 19 and the port injector 20, the in-cylinder injector is in accordance with an injection distribution ratio obtained by an injection amount calculation process 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 control means for controlling the in-cylinder injector 19 and the port injector 20 so that the total fuel amount according to the present invention is injected. 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 constituting the control device of the engine 2 calculates the total fuel amount Qall injected from the in-cylinder injector 19 and the port injector 20 as described above, the engine load factor required for the engine 2 is calculated. Based on the engine speed, the ratio of distributing the total fuel amount Qall to the in-cylinder injector 19 and the port injector 20 is calculated.

  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 with the fuel correction amount dQ calculated by the above equation (1), and calculates the required injection amount Qall. The calculated required injection amount Qall is distributed to the in-cylinder injector 19 and the port injection injector 20 at a predetermined injection ratio, and the injection amount to be allocated to the in-cylinder injector 19 is Qdb, port injection. The injection amount assigned to the injector 20 is Qpb.

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

FIG. 2 is a diagram showing a basic injection ratio map according to the first embodiment of the present invention.
In the basic injection ratio map, the region where the engine speed is higher than NE1 and the region where the engine load factor is higher than KL2 are determined as direct injection regions. In this region, fuel is injected only from the in-cylinder injector 19. It has come to be. Further, the region where the engine load factor is lower than KL1 and the engine speed is lower than NE1 is defined as a port injection region where fuel is injected only by the port injector 20.

  An engine load factor in a range from KL1 to KL2 and an engine speed of NE1 or less is defined as a direct injection and port injection region, and a basic value corresponding to the engine load factor and the engine speed is shown. 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

Next, the minimum value setting process executed by the engine ECU 8 will be described.
The engine ECU 8 calculates the minimum injection amount Qmin in the in-cylinder injector 19 based on the fuel pressure of the fuel supplied to the in-cylinder injector 19 and the temperature characteristics of the in-cylinder injector 19. .

  First, the relationship between the fuel pressure of the fuel supplied to the in-cylinder injector 19 and the basic minimum injection amount Qminb will be described.

  FIG. 3 is a diagram showing a minimum injection amount map according to the first embodiment of the present invention.

  FIG. 3 (a) is a diagram showing the correspondence between the injection time and the injection amount in the in-cylinder injector 19 according to the embodiment of the present invention, and FIG. 3 (b) is a diagram illustrating the implementation of the present invention. It is a figure which shows the minimum injection amount map 55 which concerns on a form.

  As shown in FIG. 3A, when the in-cylinder injector 19 is energized by the engine ECU 8, fuel is injected into the cylinder 6 at an injection amount Q proportional to the energization time. Therefore, the engine ECU 8 can accurately adjust the injection amount Q of the fuel injected into the cylinder 6 by controlling the energization time for the in-cylinder injector 19.

  However, if the energization time of the in-cylinder injector 19 becomes too short, the energization time and the injection amount Q are not proportional to each other due to friction during lift of a needle (not shown), and fuel injection by the engine ECU 8 is performed. The accuracy of the quantity Q is reduced. That is, the in-cylinder injector 19 has a basic minimum injection amount Qminb that can execute accurate fuel injection with respect to the energization time.

  Further, the basic minimum injection amount Qminb at which the energization time and the injection amount Q are not proportional to each other varies depending on the fuel pressure of the fuel supplied to the in-cylinder injector 19. Specifically, as shown in FIG. 3, the basic minimum injection amount Qminb at the high fuel pressure is larger than the basic minimum injection amount Qminb at the low fuel pressure.

  Therefore, as shown in FIG. 3B, the engine ECU 8 stores in the ROM 32 a minimum injection amount map 55 that associates the fuel pressure of the fuel supplied to the in-cylinder injector 19 with the basic minimum injection amount Qminb. ing. The minimum injection amount map 55 is determined such that the basic minimum injection amount Qminb at high fuel pressure is larger than the basic minimum injection amount Qminb at low fuel pressure.

  Therefore, the engine ECU 8 according to the present embodiment constitutes a minimum value setting means for setting the minimum value of the amount of fuel injected from the in-cylinder injection means in accordance with the fuel pressure detected by the fuel pressure detection means.

  Next, the relationship between the temperature characteristic of the in-cylinder injector 19 and the minimum injection amount Qmin will be described.

  The engine ECU 8 calculates the correction coefficient K in accordance with the temperature characteristics of the in-cylinder injector 19, corrects the basic minimum injection amount Qminb calculated from the minimum injection amount map 55 with the correction coefficient K, and finally The minimum injection amount Qmin set to is calculated.

  Specifically, the engine ECU 8 inputs the result of detecting the temperature of the fuel supplied from the fuel temperature sensor 48 to the in-cylinder injector 19, thereby adjusting the temperature of the needles constituting the in-cylinder injector 19. get. Further, the engine ECU 8 inputs the result of detecting the coolant temperature of the engine 2 from the water temperature sensor 38, thereby estimating the temperature of the nozzle body that accommodates the needle of the in-cylinder injector 19 so as to be axially displaceable. Here, the case where the temperature of the fuel supplied to the in-cylinder injector 19 is estimated as it is as the temperature of the needle will be described, but it is estimated according to the temperature of the fuel supplied to the in-cylinder injector 19. The temperature of the needle is stored in advance in the ROM 32 as a map, and when the engine ECU 8 detects the temperature of the fuel supplied from the fuel temperature sensor 48 to the in-cylinder injector 19, the temperature of the needle is referred to with reference to this map. May be estimated. Alternatively, the engine ECU 8 stores in advance in the ROM 32 a map for estimating the temperature of the needle based on the cooling water temperature or the outside air temperature of the engine 2 and the integrated fuel flow rate, and acquires signals representing these pieces of information. The temperature of the needle may be estimated by referring to the map. In this case, the engine ECU 8 acquires a signal indicating the cooling water temperature from the water temperature sensor 38 and acquires the outside air temperature from an outside air temperature sensor (not shown). Further, the engine ECU 8 calculates the integrated fuel flow rate from the energization time for the in-cylinder injector 19.

  As a method for estimating the temperature of the nozzle body, for example, the coolant temperature of the engine 2 is detected by the water temperature sensor 38 immediately before or when the engine 2 is started, and the detected value is stored in the RAM 33 as initial water temperature data. When estimating the temperature of the nozzle body, the engine ECU 8 acquires the current cooling water temperature of the engine 2 from the water temperature sensor 38 and calculates the difference from the initial water temperature data stored in the RAM 33. Further, the engine ECU 8 stores in advance in the ROM 32 a map in which the difference between the initial water temperature data and the current water temperature is associated with the estimated temperature of the nozzle body. This map is created in advance based on experimental measurements. Then, the engine ECU 8 calculates the difference between the initial water temperature data and the current water temperature, and estimates the temperature of the nozzle body by referring to the map stored in the ROM 32.

  Therefore, the water temperature sensor 38 and the fuel temperature sensor 48 according to the present embodiment constitute a temperature difference detection means according to the present invention.

  The engine ECU 8 calculates the correction coefficient K based on the difference between the temperature of the needle and the temperature of the nozzle body calculated as described above, and is calculated from the minimum injection amount map 55 as shown in the following equation (4). The basic minimum injection amount Qminb is corrected.

Qmin = Qminb · K (4)
The correction coefficient K is associated with the difference between the needle temperature and the nozzle body temperature and is stored in advance in the ROM 32 as a temperature correction map. The larger the difference between the needle temperature and the nozzle body temperature, the lower the correction coefficient K is. The correction value is determined so that the injection amount Qmin becomes large. This correction coefficient K is determined by the moving performance of the needle of the in-cylinder injector 19 such as the state of friction between the needle and the nozzle body due to temperature and the change in the length in the axial direction. It has been demanded. For example, when the temperature of the needle and the temperature of the nozzle body are equal, the correction coefficient K is set to “1”, and as the difference between the temperature of the needle and the temperature of the nozzle body increases, the correction coefficient K becomes “1”. It is determined to be a larger value. Hereinafter, the reason why the minimum injection amount Qmin is increased as the difference between the temperature of the needle and the temperature of the nozzle body is increased will be specifically described.

  FIG. 4 is a diagram showing temperature characteristics of the in-cylinder injector 19 according to the first embodiment of the present invention.

  FIG. 4A shows temperature characteristics of the in-cylinder injector 19 when the fuel pressure of the fuel supplied to the in-cylinder injector 19 is 4 MPa. FIG. 4B shows temperature characteristics of the in-cylinder injector 19 when the fuel pressure of the fuel supplied to the in-cylinder injector 19 is 12 MPa. In any case, the minimum injection amount corresponding to the injection time indicated by the broken lines A to D in the region in which the injection time and the injection amount are proportional and enables accurate fuel injection is the difference between the needle temperature and the nozzle body. When the temperature difference is 50 ° C. (broken lines B and D), it is higher than when the temperature difference is 0 ° C. (broken lines A and C). That is, the minimum injection amount increases as the temperature difference between the needle temperature and the nozzle body increases.

  Such a phenomenon is because the in-cylinder injector 19 is particularly unstable during micro-injection because only the nozzle body expands when the temperature of the nozzle body becomes higher than the temperature of the needle. As a result, when the temperature difference between the needle and the nozzle main body is large, the injection accuracy at the time of micro injection is lower than when the temperature of the needle and the nozzle main body is equal, and the engine ECU 8 is in-cylinder injector. Even if it is controlled to execute the minute injection at 19, there is a possibility that the fuel is not suitably injected into the cylinder 6.

  Therefore, when the engine ECU 8 in this embodiment acquires the temperature of the needle and the temperature of the nozzle body, the engine ECU 8 calculates the temperature difference between them, and the larger the difference between the temperature of the needle and the temperature of the nozzle body, the smaller the minimum injection amount Qmin. Is set to a large value.

  The correction coefficient K is set as a value that can correspond to any fuel pressure of the fuel supplied to the in-cylinder injector 19. For example, the change amount of the minimum injection amount according to the temperature difference of the in-cylinder injector 19 when the fuel pressure of the fuel supplied to the in-cylinder injector 19 is maximum, and the in-cylinder injector 19 is supplied. A change amount of the minimum injection amount corresponding to the temperature difference of the in-cylinder injector 19 when the fuel pressure of the fuel is minimum is calculated in advance experimentally, and a correction coefficient K corresponding to the temperature difference is an average of these change amounts. Try to get a reasonable value.

  Alternatively, the correction coefficient K may be a two-dimensional map corresponding to the temperature difference generated in the in-cylinder injector 19 and the fuel pressure of the fuel supplied to the in-cylinder injector 19. In this case, the engine ECU 8 stores in the RAM 33 a signal representing the fuel pressure acquired when the basic minimum injection amount Qminb is calculated, and refers to this fuel pressure again when calculating the correction coefficient K.

  FIG. 5 is a flowchart for explaining the minimum injection amount calculation processing according to the first 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. Here, the predetermined time interval means constant rotation of the crankshaft of the engine 2.

  First, the engine ECU 8 inputs a signal from the fuel pressure sensor 40 and detects the fuel pressure of the fuel supplied to the in-cylinder injector 19 (step S11).

  Next, the engine ECU 8 calculates the basic minimum injection amount Qminb by referring to the fuel pressure detected in step S11 and the minimum injection amount map 55 stored in the ROM 32 (step S12).

  Next, the engine ECU 8 estimates the temperature of the in-cylinder injector 19 (step S13). Specifically, the engine ECU 8 determines the temperature of the nozzle body of the in-cylinder injector 19 from the temperature difference between the current cooling water temperature of the engine 2 detected by the water temperature sensor 38 and the cooling water temperature when the engine 2 is started. Is estimated. Further, the engine ECU 8 calculates a signal representing the temperature of the needle of the in-cylinder injector 19 based on the signal representing the fuel temperature acquired from the fuel temperature sensor 48, and the temperature difference between the nozzle body temperature and the needle temperature. Is calculated.

  Next, the engine ECU 8 refers to the temperature correction map stored in the ROM 32, and calculates a correction coefficient K corresponding to the temperature difference calculated in step S13 (step S14).

  Next, the engine ECU 8 calculates the minimum injection amount Qmin using the basic minimum injection amount Qminb calculated in step S12, the correction coefficient K calculated in step S14, and the above equation (4) (step S15). . The engine ECU 8 stores the calculated minimum injection amount Qmin in the RAM 33. Thereby, the engine ECU 8 can refer to the minimum injection amount Qmin in an injection amount calculation process described later.

  Returning to FIG. 1, the engine ECU 8 determines that the basic direct injection amount Qdb for the in-cylinder injector 19 calculated based on a predetermined injection ratio is the minimum injection calculated by the above-described minimum injection amount calculation process. If the amount is less than the amount Qmin, the final direct injection amount Qd for the in-cylinder injector 19 is held at the minimum injection amount Qmin, and the difference between the basic direct injection amount Qdb and the minimum injection amount Qmin is used for port injection. The final port injection amount Qp is reduced from the fuel amount Qpb injected by the injector 20.

  Therefore, the engine ECU 8 according to the present embodiment constitutes a fuel amount correcting means according to the present invention, and the engine ECU 8 is provided with the total required injection amount supplied to the in-cylinder injector 19 and the port injector 20. The injection ratio for the in-cylinder injector 19 and the port injector 20 is corrected without changing Qall.

  On the other hand, in the engine ECU 8, the basic direct injection amount Qdb for the in-cylinder injector 19 calculated based on a predetermined injection ratio is not less than the minimum injection amount Qmin calculated in the above-described minimum injection amount calculation process. If so, the basic direct injection amount Qdb is finally set as the fuel amount Qd injected from the in-cylinder injector 19. Further, the engine ECU 8 sets the fuel amount Qpb for the port injector 20 calculated based on a predetermined injection ratio to be the fuel amount Qp finally injected from the port injector 20.

  FIG. 6 is a flowchart for explaining an injection amount calculation process according to the first 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. Here, the predetermined time interval means constant rotation of the crankshaft of the engine 2.

  The engine ECU 8 first calculates the total required injection amount Qall by adding the total fuel amount calculated by the fuel injection amount map and the fuel correction amount dQ calculated by the above formula (1) (step) S21).

  Next, the engine ECU 8 calculates a basic injection ratio with reference to the basic injection ratio map (step S22). The basic injection ratio is the ratio of the amount of fuel distributed to the in-cylinder injector 19 and the port injector 20 as described above, and is 2 associated with the engine speed and the engine load factor of the engine 2. It is stored in advance in the ROM 32 as a basic dimensional ejection ratio map.

  Next, the engine ECU 8 calculates a basic direct injection amount Qdb (step S23). This basic direct injection amount Qdb is the product of the total required injection amount Qall calculated in step S21 and the ratio of the fuel amount distributed to the in-cylinder injector 19 at the basic injection distribution ratio calculated in step S22. It is calculated by.

  Next, the engine ECU 8 calculates a basic port injection amount Qpb (step S24). The basic direct injection amount Qpb is the product of the total required injection amount Qall calculated in step S21 and the ratio of the fuel amount distributed to the port injector 20 at the basic injection distribution rate calculated in step S22. Desired.

  Next, the engine ECU 8 acquires the minimum injection amount Qmin for the in-cylinder injector 19 (step S25). Specifically, the minimum injection amount Qmin is calculated by the engine ECU 8 and stored in the RAM 33 in the above-described minimum injection amount calculation process. Therefore, the engine ECU 8 obtains the minimum injection amount Qmin stored in the RAM 33 in this step.

  Next, the engine ECU 8 compares the basic direct injection amount Qdb calculated in step S23 with the minimum injection amount Qmin calculated in step S25, and the basic direct injection amount Qdb is equal to or greater than the minimum injection amount Qmin. Whether or not (step S26).

  If the engine ECU 8 determines that the basic direct injection amount Qdb is equal to or greater than the minimum injection amount Qmin as a result of the comparison (Yes in step S26), the basic direct injection amount Qdb is set as the final direct injection amount Qd (step S26). S27) In the next fuel injection, the in-cylinder injector 19 is controlled so that the amount of fuel injected from the in-cylinder injector 19 becomes the final direct injection amount Qd.

  Then, the engine ECU 8 sets the basic port injection amount Qpb calculated in step S24 as the final port injection amount Qp (step S28), and the fuel amount injected from the port injector 20 in the next fuel injection is the final direct injection amount. The port injection injector 20 is controlled so as to achieve the injection amount Qp.

  On the other hand, if the engine ECU 8 determines in step S26 that the basic direct injection amount Qdb is less than the minimum injection amount Qmin (No in step S26), the minimum injection amount Qmin is set as the final direct injection amount Qd (step S26). S29) In the next fuel injection, the in-cylinder injector 19 is controlled so that the amount of fuel injected from the in-cylinder injector 19 becomes the final direct injection amount Qd.

  Then, the engine ECU 8 sets the value obtained by subtracting the difference between the minimum injection amount Qmin and the basic direct injection amount Qdb from the basic port injection amount Qpb calculated in step S24 as the final port injection amount Qp (step S30). In this fuel injection, the port injector 20 is controlled so that the fuel amount injected from the port injector 20 becomes the final port injection amount Qp.

  FIG. 7 is a diagram showing an example of changes in the air-fuel ratio by the control apparatus for an internal combustion engine according to the first embodiment of the present invention.

  In the following example, the idling state in which the accelerator pedal 18 is not depressed is already continued for several minutes, and the change in the air-fuel ratio is illustrated when the accelerator pedal 18 is depressed at time T1.

  FIG. 7A is a diagram showing a change over time in the load of the engine 2 and the fuel pressure of the fuel supplied to the in-cylinder injector 19. FIG. 7B is a diagram showing a change over time in the amount of fuel injected by the in-cylinder injector 19 and the port injector 20. FIG.7 (c) is a figure which shows the time change of the air fuel ratio in the vehicle carrying the control apparatus which concerns on this Embodiment, and the vehicle carrying the conventional control apparatus.

  When the accelerator pedal 18 (see FIG. 1) is depressed at time T1, the vehicle starts to start, and the load on the engine 2 (see FIG. 1) increases (see the broken line 61).

  Further, until the time T2 is reached, the engine load factor of the engine 2 is smaller than KL1 (see FIG. 2), and therefore the total fuel amount represented by the solid line 63 is solely due to the port injector 20 (see FIG. 1). It will be a thing.

  At this time, the temperature of the fuel in the fuel distribution pipe 21 (see FIG. 1) rises with the temperature of the engine 2 in a state where the fuel is not injected from the in-cylinder injector 19 (see FIG. 1). Therefore, the volume of the fuel in the fuel distribution pipe 21 increases, and the fuel pressure increases (see the solid line 62).

  When the engine load factor reaches KL1 at time T2 and enters the direct injection and port injection region (see FIG. 2), the engine ECU 8 (see FIG. 1) refers to the basic injection ratio map to refer to the engine load factor. A basic injection ratio according to KL and the engine speed NE is calculated to calculate a basic direct injection amount Qdb (see solid line 64). Therefore, the total amount of fuel after T2 (see the solid line 63) represents the total amount of fuel injected from the in-cylinder injector 19 and the port injector 20.

  At T2, since the basic direct injection amount Qdb is lower than the minimum injection amount Qmin, fuel injection is performed from the in-cylinder injector 19 with the minimum injection amount Qmin, and the port injection injector 20 Fuel injection is performed with the fuel amount obtained by subtracting the difference between the minimum injection amount Qmin and the basic direct injection amount Qdb from the port injection amount Qpb, that is, the final port injection amount Qp.

In this case, since the required injection amount Qall is maintained, the fluctuation of the air-fuel ratio falls within the combustible range (see the solid line 65). In contrast, in a control device for a conventional internal combustion engine,
Since the minimum injection amount Qmin is a fixed value regardless of the fuel pressure, when the fuel pressure is high, the set minimum injection amount Qmin may be lower than the actual minimum injection amount of the in-cylinder injector 19. Under such circumstances, the fuel is injected from the in-cylinder injector 19 even though the engine ECU 8 controls the in-cylinder injector 19 to perform the fuel injection of the minimum injection amount Qmin. As a result, the air-fuel ratio fluctuates to the lean side and falls out of the combustible range (see broken line 66).

  As described above, in the control apparatus for an internal combustion engine according to the embodiment of the present invention, the minimum amount of fuel injected from the in-cylinder injector 19 based on the controllable range of the fuel injection amount that varies depending on the fuel pressure. Since the value can be set, even when the amount of fuel to be injected into the cylinder 6 is small, the calculated amount of fuel actually injected into the cylinder 6 by controlling the in-cylinder injector 19 is calculated. It becomes possible to approach the amount. When the amount of fuel injected by the in-cylinder injector 19 is below the minimum value Qmin, the amount of fuel injected by the in-cylinder injector 19 is maintained at the minimum value Qmin and the calculated fuel amount Since the difference between Qdb and the minimum value Qmin is subtracted from the fuel amount Qpb injected by the port injector 20, the total fuel amount Qall to be injected can be made to coincide with the calculated value. As a result, exhaust purification performance can be improved and drivability can be improved.

  In addition, when the temperature difference between the needle constituting the in-cylinder injector 19 and the nozzle body is large, the injection accuracy at the time of micro-injection is lower than when the temperature is small, so by increasing the minimum value, Only the region where the injection accuracy in the injection injector 19 is good can be used. In addition, when the temperature difference between the needle and the nozzle body is small, the in-cylinder injector 19 can be controlled to a range where the fuel injection amount is small compared to the case where the needle is large, so that the actual injection is achieved by reducing the minimum value. The fuel amount to be calculated and the calculated fuel amount can be made closer than before.

  Further, by appropriately setting the minimum injection amount Qmin for the in-cylinder injector 19, the change in the injection ratio for the in-cylinder injector 19 and the port injector 20 can be minimized. Therefore, it is possible to reduce fluctuations in the actual air-fuel ratio due to the change in the injection ratio.

  In the above description, the case where the control device according to the present invention is applied to an internal combustion engine including the in-cylinder injector 19 and the port injector 20 is described. As in the second embodiment, the control device according to the present invention may be applied to an internal combustion engine including an in-cylinder injector 19.

(Second Embodiment)
A control apparatus for an internal combustion engine according to a second embodiment of the present invention will be described with reference to FIGS. 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 four-cylinder engine.

  The configuration of the control device for the internal combustion engine according to the second embodiment is substantially the same as the configuration of the control device for the internal combustion engine according to the first embodiment described above. The same reference numerals as those of the first embodiment shown in FIG. 1 are used for explanation, and only differences are particularly described in detail.

  FIG. 8 is a schematic configuration diagram showing a control device for an internal combustion engine according to the second embodiment of the present invention.

  Each cylinder 6 is provided with an in-cylinder injector 19 for injecting fuel into the cylinder 6.

  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 high pressure fuel pump 23 is connected to a low pressure fuel pump 27 via a fuel pressure regulator 26.

  The ROM 32 of the engine ECU 8 stores a fuel injection amount map in which the intake air amount and the engine speed are associated with the fuel amount injected from the in-cylinder injector 19. When the engine ECU 8 obtains a signal representing the intake air amount from the air flow meter 11 and a signal representing the engine speed from the rotational speed sensor 46, the engine ECU 8 refers to the fuel injection amount map to inject from the in-cylinder injector 19 The basic direct injection amount Qdb injected from the in-cylinder injector 19 is calculated by calculating the fuel amount to be performed and adding the fuel correction amount dQ calculated by the PI feedback control described above. .

  Further, when the basic direct injection amount Qdb is smaller than the minimum injection amount Qmin calculated by the minimum injection amount calculation process, the engine ECU 8 determines that the fuel amount injected from the in-cylinder injector 19 is the minimum injection amount Qmin. The in-cylinder injector 19 is controlled so that

  FIG. 9 is a flowchart for explaining an injection amount calculation process according to the second embodiment of the present invention.

  The following processing is executed by the CPU 34 constituting the engine ECU 8 and realizes a program that can be processed by the CPU 34. 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. Here, the predetermined time interval means constant rotation of the crankshaft of the engine 2.

  The engine ECU 8 first calculates the basic direct injection amount Qdb using the fuel amount calculated from the fuel injection amount map and the fuel correction amount dQ calculated from the above equation (1) (step S31).

  Next, the engine ECU 8 calculates a minimum injection amount Qmin for the in-cylinder injector 19 (step S32). Specifically, the engine ECU 8 calculates the minimum injection amount Qmin for the in-cylinder injector 19 according to the same process as the minimum injection amount calculation process in the first embodiment described above.

  Next, the engine ECU 8 compares the basic direct injection amount Qdb calculated in step S31 with the minimum injection amount Qmin calculated in step S32, and the basic direct injection amount Qdb is equal to or greater than the minimum injection amount Qmin. Whether or not (step S33).

  If the engine ECU 8 determines that the basic direct injection amount Qdb is equal to or greater than the minimum injection amount Qmin (Yes in step S33), the basic direct injection amount Qdb is set as the final direct injection amount Qd (step S34), and the next time. In this fuel injection, the in-cylinder injector 19 is controlled so that the amount of fuel injected from the in-cylinder injector 19 becomes the final direct injection amount Qd.

  On the other hand, if the engine ECU 8 determines in step S33 that the basic direct injection amount Qdb is less than the minimum injection amount Qmin (No in step S33), the minimum injection amount Qmin is set as the final direct injection amount Qd (step S33). S35) In the next fuel injection, the in-cylinder injector 19 is controlled so that the amount of fuel injected from the in-cylinder injector 19 becomes the final direct injection amount Qd.

  FIG. 10 is a diagram showing an example of changes in the air-fuel ratio by the control apparatus for an internal combustion engine according to the second embodiment of the present invention.

  In the following example, the change in the air-fuel ratio is shown when the running state of the vehicle has suddenly changed from a high engine load factor and a high engine speed to a low state.

  FIG. 10A is a diagram showing the change over time in the engine load factor of the engine 2 and the fuel pressure of the fuel supplied to the in-cylinder injector 19. FIG. 10B is a diagram showing a change over time in the amount of fuel injected by the in-cylinder injector 19. FIG.10 (c) is a figure which shows the time change of the air fuel ratio in the vehicle carrying the control apparatus which concerns on this Embodiment, and the vehicle carrying the conventional control apparatus.

  When the engine load factor and the engine speed of the engine 2 (see FIG. 8) rapidly decrease (see the broken line 71) when the fuel pressure in the fuel distribution pipe 21 (see FIG. 8) is high, the in-cylinder injector 19 (see FIG. 8) decreases the amount of fuel injected, so that the fuel pressure in the fuel distribution pipe 21 does not decrease and remains high (see the solid line 72).

  At this time, as the engine speed of the engine 2 decreases and the intake air amount decreases, the required value of the fuel injection amount for the in-cylinder injector 19 also decreases (see the solid line 73).

  Here, in the present embodiment, since the engine ECU 8 sets the minimum injection amount Qmin according to the fuel pressure, the engine ECU 8 controls to inject the minimum injection amount Qmin into the in-cylinder injector 19 (see the solid line 74). ). In this case, although the air-fuel ratio fluctuates according to the difference between the required value and the minimum injection amount Qmin that is actually injected (see the solid line 76), it is well within the combustible range.

  In contrast, in the conventional control device, since the minimum injection amount Qmin is a fixed value, when the fuel pressure is high, the actual minimum injection amount of the in-cylinder injector 19 is set to a preset minimum injection amount. It becomes higher than Qmin.

  For this reason, the engine ECU 8 does not inject the fuel from the in-cylinder injector 19 (see the broken line 75) even though it controls the in-cylinder injector 19 to inject the fuel of the minimum injection amount Qmin. As a result, the air-fuel ratio fluctuates to the lean side and falls out of the combustible range (see broken line 77).

  As described above, in the control apparatus for an internal combustion engine according to the embodiment of the present invention, the minimum amount of fuel injected from the in-cylinder injector 19 based on the controllable range of the fuel injection amount that varies depending on the fuel pressure. Since the value can be set, even when the amount of fuel to be injected into the cylinder 6 is small, the amount of fuel calculated by controlling the in-cylinder injector 19 to calculate the amount of fuel actually injected into the cylinder 6 It becomes possible to approach. As a result, exhaust purification performance can be improved and drivability can be improved.

  In the above description, the ROM 32 of the engine ECU 8 stores the minimum injection amount map 55 and the temperature correction map, calculates the basic minimum injection amount Qminb from the minimum injection amount map 55, and then based on the temperature correction map. In the above description, the basic minimum injection amount Qminb is corrected with the correction coefficient K to calculate the minimum injection amount Qmin. However, the ROM 32 of the engine ECU 8 displays a two-dimensional minimum injection amount map in which the fuel pressure of the fuel supplied to the in-cylinder injector 19, the temperature difference between the needle and the nozzle body, and the minimum injection amount Qmin are associated with each other. You may make it memorize | store.

  In this case, when the engine ECU 8 acquires the fuel pressure of the fuel supplied to the in-cylinder injector 19 and the temperature characteristics of the in-cylinder injector 19, the engine ECU 8 refers to the two-dimensional minimum injection amount map stored in the ROM 32. Thus, the minimum injection amount Qmin is calculated.

  In the above description, the case where the engine ECU 8 detects the temperature of the needle of the in-cylinder injector 19 with the fuel temperature sensor 48 installed in the fuel distribution pipe 21 has been described. However, the fuel temperature sensor 48 may be installed on the upstream side of the fuel supply path such as the fuel tank 29, and the engine ECU 8 may estimate the needle temperature based on the fuel temperature acquired from the fuel temperature sensor 48. In this case, the engine ECU 8 stores a map in which the fuel temperature detected by the fuel temperature sensor 48 is associated with the estimated needle temperature in the ROM 32. The estimated needle temperature acquired from the map may be further corrected by the engine speed and the engine load factor.

  As described above, the control apparatus for an internal combustion engine according to the present invention has the effect of improving the fuel injection accuracy compared to the conventional one and improving the exhaust purification performance and drivability, and at least injects fuel into the cylinder. It is useful for a control device of a possible internal combustion engine.

1 is a schematic configuration diagram illustrating a control device for an internal combustion engine according to a first embodiment of the present invention. It is a figure which shows the basic injection division ratio map which concerns on the 1st Embodiment of this invention. It is a figure which shows the minimum injection amount map which concerns on the 1st Embodiment of this invention. It is a figure which shows the temperature characteristic of the injector for cylinder injection which concerns on the 1st Embodiment of this invention. It is a flowchart for demonstrating the minimum injection amount calculation process which concerns on the 1st Embodiment of this invention. It is a flowchart for demonstrating the injection quantity calculation process which concerns on the 1st Embodiment of this invention. It is a figure which shows the example of a change of the air fuel ratio by the control apparatus of the internal combustion engine which concerns on the 1st Embodiment of this invention. It is a schematic block diagram which shows the control apparatus of the internal combustion engine which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating the injection quantity calculation process which concerns on the 2nd Embodiment of this invention. It is a figure which shows the example of a change of the air fuel ratio by the control apparatus of the internal combustion engine which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

2 Engine (Internal combustion engine)
4 Intake manifold 5 Surge tank 6 Cylinder 8 Engine ECU (Control device, fuel amount calculation means, distribution calculation means, fuel pressure detection means, temperature difference detection means, fuel amount correction means, minimum value setting means, control means)
10 Intake pipe 11 Air flow meter (fuel amount calculation means)
14 Throttle valve 15 Exhaust manifold 16 Exhaust pipe 17 Three-way catalytic converter 18 Accelerator pedal 19 In-cylinder injector (in-cylinder injection means)
20 Port injection injector (port injection means)
21 Fuel distribution pipe 23 High pressure fuel pump 24 Electromagnetic spill valve 25 Fuel distribution pipe 26 Fuel pressure regulator 27 Low pressure fuel pump 29 Fuel tank 32 ROM
33 RAM
34 CPU
38 Water temperature sensor (temperature difference detection means)
40 Fuel pressure sensor (fuel pressure detection means)
42 Air-fuel ratio sensor 44 Accelerator opening sensor (distribution calculation means)
46 Rotational speed sensor (fuel amount calculation means, distribution calculation means)
48 Fuel temperature sensor (temperature difference detection means)

Claims (4)

In-cylinder injection means for injecting fuel into the cylinder of the internal combustion engine;
Fuel amount calculating means for calculating the amount of fuel injected into the cylinder by the in-cylinder injection means based on the engine speed of the internal combustion engine and the amount of air sucked into the cylinder;
A control unit for controlling the in-cylinder injection unit so that the fuel amount calculated by the fuel amount calculation unit is injected,
Fuel pressure detection means for detecting the fuel pressure of the fuel supplied to the in-cylinder injection means;
A temperature difference detecting means for detecting a temperature difference between an injection valve constituting the in-cylinder injection means and a main body for accommodating the injection valve movably in the axial direction ;
Minimum value setting for setting the minimum value of the amount of fuel injected from the in-cylinder injection unit according to the fuel pressure detected by the fuel pressure detection unit and the temperature difference detected by the temperature difference detection unit Means, and
When the fuel amount calculated by the fuel amount calculating unit is smaller than the minimum value set by the minimum value setting unit, the control unit causes the in-cylinder injection so that the minimum amount of fuel is injected. A control device for an internal combustion engine, characterized by controlling the means. In-cylinder injection means for injecting fuel into the cylinder of the internal combustion engine;
Port injection means for injecting fuel into an intake passage connected to the cylinder;
Fuel amount calculation means for calculating a total fuel amount injected from the in-cylinder injection means and the port injection means based on the engine speed of the internal combustion engine and the amount of air sucked into the cylinder;
A control device for an internal combustion engine, comprising: control means for controlling the in-cylinder injection means and the port injection means so that the total fuel amount calculated by the fuel amount calculation means is injected;
A distribution calculating means for calculating a ratio of distributing the total fuel amount to the in-cylinder injection means and the port injection means based on an engine load factor and an engine speed required for the internal combustion engine;
Fuel pressure detection means for detecting the fuel pressure of the fuel supplied to the in-cylinder injection means;
A temperature difference detecting means for detecting a temperature difference between an injection valve constituting the in-cylinder injection means and a main body for accommodating the injection valve movably in the axial direction ;
Minimum value setting for setting the minimum value of the amount of fuel injected from the in-cylinder injection unit according to the fuel pressure detected by the fuel pressure detection unit and the temperature difference detected by the temperature difference detection unit Means,
When the fuel amount corresponding to the ratio distributed to the in-cylinder injection means calculated by the distribution calculation means is smaller than the minimum value set by the minimum value setting means, the ratio to distribute to the in-cylinder injection means And the difference between the fuel amount corresponding to the fuel amount corresponding to the proportion distributed to the in-cylinder injection means calculated by the distribution calculation means is the port injection means. A fuel amount correction unit that corrects the fuel amount injected by the in-cylinder injection unit and the port injection unit by subtracting the amount of fuel from the fuel amount corresponding to the proportion distributed to
The control device for an internal combustion engine, wherein the control means controls the in-cylinder injection means and the port injection means so that the fuel amount corrected by the fuel amount correction means is injected .   3. The internal combustion engine according to claim 1, wherein the minimum value setting means increases the minimum value when the fuel pressure detected by the fuel pressure detection means is high, compared with a case where the fuel pressure is low. Control device. The said minimum value setting means makes the said minimum value large compared with the case where it is small when the temperature difference detected by the said temperature difference detection means is large, The Claim 1 or Claim 2 characterized by the above-mentioned. Control device for internal combustion engine.

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