JP2014020211A - Fuel injection control device of direct-injection gasoline engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device of a direct-injection gasoline engine which can preset such optimal number of times of split injections that penetration is not excessively elongated, can suppress the increasing of PM discharge amount and oil dilution amount and, on the other hand, can improve fuel consumption, exhaust performance or the like.SOLUTION: When an engine temperature is a predetermined temperature or less, as the net injection quantity to be injected during one combustion cycle, or as the net injection pulse width to be required during one combustion cycle is enlarged, the number of times of split injections during one combustion cycle is increased.

Description

  The present invention relates to a control device for an in-cylinder injection engine that directly injects fuel into a combustion chamber of each cylinder, and in particular, performs multiple fuel injections (split injection) during one combustion cycle based on the operating state of the engine. The present invention relates to a fuel injection control device for an in-cylinder injection engine.

  In recent years, from the viewpoint of environmental conservation, reduction of exhaust gas substances such as carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx), fuel consumption, and engine output contained in automobile exhaust gas An in-cylinder in-cylinder injection engine has been put to practical use mainly for the purpose of improving the above. This in-cylinder injection engine directly injects fuel into a combustion chamber of each cylinder by a fuel injection valve (also called an injector) in the form of an electromagnetic valve provided for each cylinder.

  In an in-cylinder injection engine, depending on the fuel injection method, fuel spray that moves in the combustion chamber adheres to the crown surface of the piston and the cylinder bore wall surface.

  If there is a large amount of fuel adhering to and remaining on the cylinder bore wall surface, it may not be able to completely evaporate until ignition occurs, and torque fluctuations may occur in each cycle, and unburned gas tends to increase. Therefore, for example, Patent Document 1 discloses a technique for changing the fuel injection timing from the fuel injection valve in the intake stroke so that the fuel spreads on the piston crown surface and is easily vaporized when the cylinder bore wall surface temperature is low. ing.

  Further, for example, Patent Document 2 uses the property that the spraying distance, i.e., the penetration, of the spray with a small fuel injection amount (hereinafter sometimes abbreviated as the injection amount) is shorter than the spray with a large injection amount. And by executing multiple fuel injections during one combustion cycle and reducing the fuel injection amount per time, fuel adhesion to the cylinder bore wall surface is reduced, and for changes in engine operating conditions, Disclosed is a technique for dispersing the spray by keeping the interval between the pre-injection and the post-injection (injection interval) at a substantially constant crank angle, i.e., increasing the injection interval as the engine speed decreases and decreasing the injection interval as the engine speed increases. ing.

  On the other hand, for example, in Patent Document 3, in order to suppress deterioration in the linearity of the injection amount, when performing fuel injection divided into a plurality of times per combustion cycle, the injection amount correction amount in one combustion cycle is divided into a plurality of times. A technique for performing partial correction on a part of the fuel injection is disclosed.

  Also, if there is a large amount of fuel remaining on the piston crown or cylinder bore wall, the amount of particulate matter, so-called particulate matter (hereinafter referred to as PM) discharged particles (PN) and the amount of fuel dissolved in engine oil (oil dilution) ) Increases. In particular, when the amount of fuel adhering to the piston crown surface is large, the number of PM exhaust particles tends to increase.

JP 2009-102997 A JP 2002-161790 A JP 2009-191768

  When split injection is performed in an in-cylinder injection engine as described above, by reducing the penetration of the fuel spray injected from the fuel injection valve, the amount of fuel adhering to the piston crown decreases, and the PM emission amount And the increase in the amount of oil dilution can be suppressed. The penetration becomes longer as the injection amount increases. For this reason, under the condition that the fuel injection amount increases as in acceleration, the piston crown surface adhesion amount may increase if the number of divisions is small even if divided injection is performed.

  On the other hand, when the engine is hot, the fuel is more easily vaporized and the spray penetration is shorter than when the engine is cold.Therefore, even if the split injection is not performed forcibly (with only one injection), the piston crown An increase in the amount of adhesion can be suppressed. When the divided injection is performed excessively, there is a possibility that the fuel efficiency deteriorates due to an increase in the fuel injection valve drive current, the fuel injection valve drive noise increases, the exhaust performance deteriorates due to the deterioration of the durability of the fuel injection valve, etc. . Also, if the penetration is shortened excessively, the homogeneity of the mixture of fuel and intake air in the cylinder is deteriorated, and the combustibility may be deteriorated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to set an optimal number of divided injections so that the penetration does not become excessively long according to the operating state of the engine. An object of the present invention is to provide a fuel injection control device for an in-cylinder injection engine that can suppress an increase in the discharge amount and the oil dilution amount and can improve fuel consumption, exhaust performance, and the like.

  In order to achieve such an object, the fuel injection control device for a direct injection engine according to the present invention basically performs an arbitrary number of divided injections in one combustion cycle based on the operating state of the engine. When the engine temperature is equal to or lower than a predetermined temperature, as the total injection amount to be injected during one combustion cycle increases or as the total injection pulse width required during one combustion cycle increases, It is characterized by increasing the number of injections.

According to the present invention, when the engine temperature is equal to or lower than the predetermined temperature, the number of divided injections is increased as the total injection amount or total injection pulse width in one combustion cycle increases, so that the penetration does not increase. As a result, the amount of fuel adhering to the piston crown surface can be reduced, the increase in the PM discharge amount and the oil dilution amount can be suppressed, and the deterioration of fuel consumption and exhaust performance can be suppressed. As a result, combustion is stabilized, and exhaust performance and fuel consumption performance are improved.
Problems, configurations, and effects other than those described above will be clarified by the following embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows one Embodiment of the fuel-injection control apparatus which concerns on this invention with the vehicle-mounted in-cylinder injection engine to which it is applied. Schematic which shows the structure around the high pressure fuel pump in one Embodiment of this invention. The block diagram which shows the input-output relationship of the engine control unit in one Embodiment of this invention. The figure which shows the relationship between the elapsed time after the energization start with respect to a fuel injection valve, and the penetration of the injected fuel spray. The figure which shows the relationship between an injection pulse width and the maximum value of penetration. (A) is a diagram for explaining the direction of fuel spray injected from the fuel injection valve, and (B) is the shortest distance from the injection port of the fuel injection valve to the piston crown surface or cylinder bore wall surface during the intake stroke. The figure which shows the relationship between a crank angle. The functional block diagram which shows an example of the control content of the fuel-injection control in one Embodiment of this invention. The time chart with which it uses for description at the time of n times division | segmentation injection in one Embodiment of this invention. The flowchart which shows an example of the process sequence performed by the division | segmentation injection frequency setting means 703 of FIG. 10 is a flowchart showing an example of a detailed processing procedure of step 904 (low temperature time division injection number calculation) in FIG. 9. 10 is a flowchart showing another example of a detailed processing procedure of step 904 (low-temperature time-division injection number calculation) in FIG. 9. 10 is a flowchart showing an example of a detailed processing procedure of step 905 (high temperature time division injection number calculation) in FIG. 9. 10 is a flowchart showing another example of a detailed processing procedure of step 905 (high-temperature time-division injection number calculation) in FIG. 9. The time chart provided in order to demonstrate the operation | movement and effect of one Embodiment of this invention compared with a prior art example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of a fuel injection control device according to the present invention together with an in-cylinder direct injection engine to which the fuel injection control device is applied.

  The in-cylinder injection engine 1 in the illustrated example includes, for example, four cylinders (# 1, # 2, # 3, # 4), and the air supplied into each cylinder 207b is taken from the inlet of the air cleaner 202, It passes through an air flow meter (air flow sensor) 203 and enters a collector 206 through a throttle body 205 in which an electric throttle 205a for controlling the amount of intake air is accommodated. The air sucked into the collector 206 is distributed to each intake pipe 201 (intake manifold and intake port) connected to each cylinder 207b of the engine 1, and then slidably inserted into each cylinder 207b. Guided to the combustion chamber 207c defined above the piston 207a. A signal corresponding to the intake air amount is supplied from the airflow sensor 203 to the engine control unit 101. Further, a throttle sensor 204 for detecting the opening degree of the electric throttle 205a is attached to the throttle body 205, and a signal from the sensor 204 is also output to the engine control unit 101.

  On the other hand, the fuel supply system for supplying fuel to the fuel injection valve 254 has the following configuration (see also FIG. 2). That is, fuel such as gasoline is primarily pressurized from the fuel tank 250 by the low pressure fuel pump 251 and regulated to a constant pressure (for example, 0.3 MPa) by the fuel pressure regulator 252 and higher by the high pressure fuel pump 209 described later. Secondary pressure is applied to a pressure (for example, 5 MPa or 10 MPa), and the fuel is injected into the combustion chamber 207c from the fuel injection valve 254 provided in each cylinder 207b via the common rail 253.

  The fuel injected into the combustion chamber 207c is ignited by a spark emitted from a spark plug 208 to which a high voltage is applied from the ignition coil 222. In this embodiment, the fuel injection valve 254 is a side injection method in which the fuel injection valve 254 is injected from the side of the combustion chamber 207c, but may be a center injection method in which the fuel injection valve 254 is injected directly above the combustion chamber 207c.

  A crank angle sensor 216 attached to the crankshaft 207d of the engine 1 outputs an angle signal indicating the rotational position of the crankshaft 207d to the engine control unit 101. The engine 1 also includes a variable valve mechanism that can change the opening and closing timing of the intake valve 225 and the exhaust valve 226, and the cam angle sensor 211 attached to the exhaust camshaft is a rotational position of the camshaft. Is output to the engine control unit 101, and an angle signal indicating the rotational position of the high-pressure fuel pump drive cam 200 that rotates as the exhaust camshaft rotates is also output to the engine control unit 101.

  In this embodiment, the four-cylinder in-cylinder injection engine 1 has been described as an example. However, an engine having another number of cylinders such as three or six cylinders may be used.

  FIG. 2 shows a configuration around the high-pressure fuel pump 209. The fuel in the fuel tank 250 is sucked and discharged by the low-pressure pump 251 as described above, and is guided to the fuel inlet of the high-pressure fuel pump 209 while being regulated to a constant pressure by the pressure regulator 252. A high-pressure pump solenoid valve 209a for adjusting the fuel introduction amount is provided on the fuel introduction port side. The high-pressure pump solenoid valve 209a is a normally closed type and closes when not energized and opens when energized. The amount of fuel supplied by the low pressure pump 251 is adjusted by the engine control unit 101 by controlling the high pressure pump solenoid valve 209a, and is added in the pressurizing chamber 209b having a piston driven by the pump drive cam 200. And is fed from the fuel discharge port to the common rail 253. A discharge valve (check valve) 209c is provided at the fuel discharge port in order to prevent the downstream high-pressure fuel from flowing back into the pressurizing chamber.

  The common rail 253 is provided with a fuel pressure sensor 256 and a fuel temperature sensor 257 for detecting the fuel temperature (fuel temperature) in the common rail 253.

  FIG. 3 shows the input / output relationship of the engine control unit 101. The engine control unit 101 includes an I / O LSI 101a including an A / D converter, a CPU 101b, and the like, and includes an accessory, an ignition ON signal, a key switch 401 signal indicating starter ON, an accelerator opening sensor 402, a brake switch 403, a vehicle speed sensor 404, airflow sensor 203, throttle sensor 204, cam angle sensor 211, crank angle sensor 216, water temperature sensor 217, air-fuel ratio sensor 218, fuel pressure sensor 256, fuel temperature sensor 257, oil temperature sensor 219, intake air temperature sensor 258 Captures signals from sensors, etc. as input, executes predetermined calculation processing, outputs various control signals calculated as calculation results, and controls the electric throttle 205a, high-pressure pump solenoid 209a, ignition coil 222, A predetermined control signal is supplied to the fuel pump 251, the fuel injection valve 254 of each cylinder (# 1, # 2, # 3, # 4), common rail internal combustion pressure control, fuel injection control ( Injection amount, number of injections in one combustion cycle, control of injection timing), ignition timing control, and the like.

  The I / OLSI 101a is provided with a drive circuit for driving each fuel injection valve 254. The drive circuit boosts the voltage supplied from the battery using a booster circuit (not shown) and supplies the IC (not shown). Each fuel injection valve 254 is driven by controlling the current by.

  Next, the penetration (reach distance) of the fuel spray injected from the fuel injection valve 254 will be described with reference to FIGS.

  FIG. 4 shows the relationship between the elapsed time after the start of injection, that is, after the start of energization, and the penetration of the injected fuel spray when fuel is injected from the fuel injection valve 254 at a predetermined fuel pressure and a predetermined injection pulse width. Are shown when the fuel temperature is low and when the fuel temperature is high. Immediately after the start of energization, there is a delay in opening the fuel injection valve 254, so the penetration is 0, and the penetration gradually increases after a predetermined time has elapsed. After a certain period of time, the injected fuel is vaporized and the penetration converges (broken line in the figure). In this case, the maximum value of penetration is PNT_max.

  In addition, when the fuel temperature is high, the fuel vaporization rate is increased and the penetration is shortened.

  When split injection is performed, the amount of injection per injection is reduced, so that the penetration is shortened as will be described later with reference to FIG.

When the penetration is longer than the allowable upper limit value Ga, the fuel adhesion amount in the combustion chamber increases to an unacceptable level. On the other hand, when it is shorter than the allowable lower limit value Gb, the mixture (homogeneity) of the fuel and the air-fuel mixture deteriorates to an unacceptable level, and the combustion becomes unstable, which may lead to deterioration of fuel consumption and exhaust performance.
The allowable upper limit value Ga and the allowable lower limit value Gb are determined by the bore, stroke, etc. of the combustion chamber.

  FIG. 5 shows the injection pulse width and the maximum value of the penetration (corresponding to PNT_max in FIG. 4) when fuel is injected from the fuel injection valve 254 at a predetermined fuel pressure in an environment of a predetermined back pressure. Showing the relationship. When the injection pulse width is short, that is, when the injection amount is small, the maximum value of penetration is small, and when the injection pulse width is long, the maximum value of penetration is large. Here, Ti_min is the minimum usable injection pulse width in which the linearity of the injection amount is maintained, and the penetration when the injection pulse width is Ti_min is the smallest.

  6A shows the direction of fuel spray injected from the fuel injection valve 254 into the combustion chamber 207c, and FIG. 6B shows the piston 207a from the top dead center (TDC) to the bottom dead center (BDC). ) (Intake stroke), and when the fuel is injected from the fuel injection valve 254 into the combustion chamber 207c, the shortest distance from the injection port of the fuel injection valve 254 to the piston crown surface or cylinder bore wall surface and the intake stroke The relationship with the crank angle [° CA] is shown. In FIG. 6, for the sake of simplicity, the case where fuel is injected from the fuel injection valve 254 in one direction is illustrated as an example. When the crank angle is 0 (piston 207a is TDC), since the crown surface of the piston 207a is closest to the injection port of the fuel injection valve 254, the shortest distance is short, and as the crank angle advances, the piston 207a moves from the TDC. As it moves to BDC, the shortest distance gradually increases. When the crank angle is CA_0 or later, the piston 207a moves further away from the injection port of the fuel injection valve 254, but the cylinder bore wall surface is closer to the injection port of the fuel injection valve 254, so the shortest distance is constant.

  Here, for example, when the penetration of the fuel spray injected from the fuel injection valve 254 is large, the fuel reaches the piston crown surface when injected on the advance side (TDC side) from the crank angle CA_0, and from the crank angle CA_0 However, when the fuel is injected on the retard side (BDC side), the fuel reaches the cylinder bore wall surface. However, if the penetration of the fuel spray injected from the fuel injection valve 254 is p1, the fuel spray will not reach the piston crown surface or the bore wall surface if the injection is started after the crank angle CA_p1. Further, for example, when the fuel spray penetration is p2, if the injection is started after the crank angle CA_p2, the fuel spray does not reach the piston crown surface or the bore wall surface.

  FIG. 6B shows the geometric distance, and in actual combustion, it is affected by the intake air flow in the combustion chamber 207c, but the amount of fuel to be injected during one combustion cycle (required injection amount). The amount of fuel adhering to the piston crown and bore walls by setting the crank angle (injection timing) to be injected according to the penetration of each divided injection pulse width. Can be reduced.

  The fuel injection valve 254 of the present embodiment has a characteristic that the fuel injection amount increases as the fuel pressure increases under the same injection pulse width, and the characteristic of the injection amount with respect to the injection pulse width is as follows: Linearity is maintained in the region where the injection pulse width is equal to or greater than the predetermined value, and the injection amount is not stable when the injection pulse width is less than the predetermined value. Therefore, in general, what can be used as the injection pulse width is limited to the predetermined value (the minimum usable injection pulse width) that maintains the linearity of the injection amount. Similarly, the amount of fuel injection that can be used is limited to a predetermined amount (minimum usable injection amount) that maintains linearity.

  Next, specific contents of the fuel injection control (control of the injection amount, the number of injections in one combustion cycle, and the injection timing) in the present embodiment will be described.

  FIG. 7 is a functional block diagram showing an example of a configuration for executing the fuel injection control. In this example, total injection pulse width calculation means 702, divided injection number setting means 703, each injection pulse width calculation means 704, each injection timing calculation means 705, upper limit injection number calculation means 706, and fuel injection valve drive Means 707 are provided.

  The total injection pulse width calculation means 702 calculates the total injection pulse width BASEPULS required in the combustion cycle (one combustion cycle). The total injection pulse width BASEPULS is obtained from the total injection amount required in the combustion cycle calculated based on the engine speed, intake air amount, cooling water temperature, intake air temperature, air-fuel ratio, etc. and the fuel pressure in the common rail. It is done.

  The divided injection number setting means 703 sets the number of injections DIV in one combustion cycle for each cylinder based on the operating state of the engine and the engine temperature. Here, based on the operating state of the engine, when the divided injection is not performed (the number of divisions is once: injection only once) and when the fuel injection is not performed (the number of divisions is 0: when the fuel is cut, etc.) When split injection is performed (the number of splits is 2 or more). When split injection is performed, the engine operating state (rotation speed, load, etc.), engine temperature, and minimum usable pulse width as described above are used. Alternatively, based on the minimum available injection amount, the number of possible divided injections in one combustion cycle (hereinafter referred to as the possible number of injections): DIVTIME_1cyl to DIVTIME_mcyl (m is the cylinder number of the engine) is set.

  More specifically, the possible injection number DIVTIME is obtained, for example, by dividing the total injection pulse width BASEPULS by the minimum usable injection pulse width (described in detail later), and the engine temperature is equal to or lower than a predetermined temperature. Sometimes (at low temperature), the possible number of injections DIVTIME is increased as the total injection amount to be injected during one combustion cycle increases or as the total injection pulse width required during one combustion cycle increases. .

  In addition, by calculating the possible number of injections DIVTIME for each cylinder as described above, it becomes possible to absorb variations in the length of fuel injection valve deployment for each cylinder, and excessive penetration of specific cylinders is excessive. It is possible to prevent shortening and lengthening.

  The engine temperature specifically refers to the temperature of the fuel and the temperature in the combustion chamber, and at least one of the fuel temperature, the water temperature, the oil temperature, the intake air temperature, and the like, which are temperatures related to these temperatures, is used. The engine temperature is required.

  The number of injections when the engine temperature is higher than the predetermined temperature (high temperature) will be described later with reference to FIGS. 9, 12, and 13.

  Each injection pulse width calculation means 704 calculates each injection pulse width: PULS_1 to PULS_n (n is the number of divided injections) according to the injection number DIV (described later) finally set by the divided injection number setting means 703. .

  Each injection timing calculation means 705 inputs the injection pulse width: PULS_1 to PULS_n (n is the number of divided injections) and the operation state, and calculates the injection timing: IT_1 to IT_n (n is the number of divided injections). By setting the injection timing: IT_1 to the intake stroke, it is advantageous for securing the mixing time and avoiding the adhesion of fuel to the piston.

  The upper limit injection number calculation means 706 calculates an upper limit injection number DIVMAX that is an allowable maximum value of the divided injection number. The calculation of the upper limit number of injections DIVMAX is made so that the injection pulse width, the injection timing, the rotation speed, etc. are input, and the injection end timing at the time of divided injection is not delayed more than a specified value in order to ensure the fuel mixing time. More specifically, the divided injection end timing is set before a certain period from the compression top dead center.

  Further, the setting of the upper limit injection number DIVMAX has a role of preventing the penetration from being excessively shortened due to the divided injection in consideration that the penetration is shortened when the engine temperature rises.

  Here, the final injection number DIV in one combustion cycle finally set by the divided injection number setting means 703 is such that the possible injection number DIVTIME is the upper limit when the engine temperature is equal to or lower than a predetermined temperature (low temperature). When the number of injections is less than DIVMAX, the number of possible injections is set to DIVTIME, and when the number of possible injections DIVTIME exceeds the upper limit number of injections DIVMAX, the upper limit number of injections is set to DIVMAX Will be discussed in more detail later).

  Further, when the engine temperature is higher than a predetermined temperature (high temperature), from step 1204 in FIG. 12 described later, the engine speed is taken on the horizontal axis and the total injection pulse width is taken on the vertical axis. The possible injection number DIVTIME is set, and the possible injection number DIVTIME is used as the final injection number (details will be described later).

  In the fuel injection valve driving means 707, the fuel injection valve 254 provided in each cylinder is calculated by each injection pulse width calculation means 704 at each injection timing IT_1-n set by each injection timing calculation means 705. A drive pulse signal having each ejection pulse width: PULS_1 to n is supplied.

  By doing in this way, the penetration of the fuel spray injected from the fuel injection valve falls within a preset upper and lower limit range (Ga-Gb in FIG. 4).

  FIG. 8 shows a time chart at the time of n-time divided injection. The first injection of the divided injections is performed when the crank angle sensor determines that IT_1 [deg] has elapsed from the reference point determined on the crank angle (in this example, the top dead center of the intake stroke). us] (injection pulse width). Similarly, when it is determined that IT_n [deg] has elapsed from the reference point, the n-th injection is performed during PULS_n [us].

  FIG. 9 is a flowchart showing an example of a processing procedure performed by the divided injection number setting means 703 of FIG. The routine shown in the flowchart of FIG. 9 is an interrupt process, and is repeatedly executed, for example, at a 10 ms period or an angular period. In step 902, it is determined whether or not the conditions permit split injection. If split injection is permitted in step 902, it is determined in step 903 whether the engine temperature is equal to or lower than a predetermined temperature.

  If the temperature is equal to or lower than the predetermined temperature, the process proceeds to step 904, where the number of divided injections when the engine is low is calculated.

  If the temperature is equal to or higher than the predetermined temperature, the process proceeds to step 905, where the number of divided injections is calculated when the engine is hot.

  FIG. 10 is a flowchart showing an example of a detailed processing procedure of step 904 (low-temperature time-division injection number calculation) in FIG. The routine shown in the flowchart of FIG. 10 is an interrupt process, and is repeatedly executed at, for example, a 10 ms period or an angular period. In step 1002, the total injection pulse width BASEPULS that satisfies the total injection amount required in the combustion cycle is read. In step 1003, the minimum injection pulse width MINPULS, which is the minimum drive pulse width that allows the fuel injection valve to inject a stable amount (a linearity is maintained in the injection amount), is read.

In the next step 1004, the number of possible injections DIVTIME is calculated. The possible number of injections DIVTIME is calculated by the following equation.
DIVTIME = Total injection pulse width BASEPULS / Minimum injection pulse width MINPULS (1)
The calculation according to Equation 1 indicates the maximum number of divided injections possible in each operating state.

  In the subsequent step 1005, the possible number of injections DIVTIME is compared with the upper limit number of injections DIVMAX that is the maximum allowable number of divided injections. When the possible injection number DIVTIME is equal to or less than the upper limit injection number DIVMAX, the possible injection number DIVTIME is set as the final injection number DIV (step 1006).

  When the possible number of injections DIVTIME is larger than the upper limit number of injections DIVMAX, DIVMAX is set as the final number of injections DIV (step 1007).

  FIG. 11 is a flowchart showing another example of the detailed processing procedure of step 904 (low-temperature time-division injection number calculation) in FIG. The routine shown in the flowchart of FIG. 11 is an interrupt process, and is repeatedly executed at, for example, a 10 ms period or an angular period. In step 1102, the total injection amount BASEFUEL required in the combustion cycle is read. In step 1103, the minimum injection amount MINFUEL at which the fuel injection valve can inject a stable amount (a linearity is maintained) is read.

In the next step 1104, the number of possible injections DIVTIME is calculated. The possible number of injections DIVTIME is calculated by the following equation.
DIVTIME = Total injection amount BASEFUEL / Minimum injection amount MINFUEL (2)
The calculation according to Equation 2 shows the maximum number of divided injections possible in each operating state.

  In the following step 1105, the possible number of injections DIVTIME is compared with the upper limit number of injections DIVMAX that is the maximum allowable number of divided injections. When the possible injection number DIVTIME is equal to or less than the upper limit injection number DIVMAX, the possible injection number DIVTIME is set as the final injection number DIV (step 1106).

  When the possible number of injections DIVTIME is larger than the upper limit number of injections DIVMAX, DIVMAX is set as the final number of injections DIV (step 1107).

  FIG. 12 is a flowchart showing an example of a detailed processing procedure of step 905 (high-temperature time-division injection number calculation) in FIG. The routine shown in the flowchart of FIG. 12 is an interrupt process, and is repeatedly executed at, for example, a 10 ms period or an angular period. In step 1202, the total injection pulse width BASEPULS is read. In step 1203, the engine speed is read. The engine speed is an index of the injection-enabled period per combustion cycle and the air flow state in the combustion chamber.

  In step 1204, the number of possible injections DIVTIME is calculated (set) from a map in which the engine speed is taken on the horizontal axis and the total injection pulse width is taken on the vertical axis. Exit. In the map of step 1204, a value is set so that the penetration does not become excessively short. In the operation region where the penetration is not long and the divided injection is not necessary, a value (for example, 0 or 1) that does not perform the divided injection is set. Thereby, for example, when the engine temperature is equal to or higher than the predetermined temperature (at a high temperature) and the total injection amount BASEFUEL is equal to or lower than the predetermined amount, the divided injection is prohibited even if the divided injection is possible.

  FIG. 13 is a flowchart showing another example of the detailed processing procedure of step 905 (high-temperature time-division injection number calculation) in FIG. In this example, the total injection amount BASEFUEL is used instead of the total injection pulse width BASEPULS in FIG. 12, and the processing procedure is substantially the same as the flowchart shown in FIG.

  In addition, the minimum injection pulse width and the minimum injection amount are not used in the divided injection number calculation at the time of high engine temperature shown in FIGS. 12 and 13, but the engine speed is used.

  Next, the function and effect of the embodiment of the present invention will be described with reference to FIG. FIGS. 14A and 14B show (a) a conventional example and (B) a fuel injection amount in the present invention when an injection amount increase request is generated at a time t1 during a period when the engine is below a predetermined temperature and split injection is performed. 4 is a time chart showing an outline of changes in the number of divided injections, (c) penetration, and (d) PM discharge amount & oil dilution amount. In the conventional example, the number of divided injections is not changed. For this reason, the penetration becomes longer due to the increase in the injection amount, and the fuel comes to adhere to the piston crown surface, leading to an increase in the PM discharge amount and the oil dilution amount.

  On the other hand, in the embodiment of the present invention, when the fuel injection amount is increased, the number of divided injections is increased, so that the penetration is not excessively long, so that the fuel adhesion on the piston crown surface is suppressed, Increases in PM emissions and oil dilution are suppressed.

  That is, according to the present invention, the optimal number of divided injections is set so that the penetration does not become longer according to the operating state of the engine, so that an increase in PM discharge amount and oil dilution amount is suppressed, and fuel efficiency / Exhaust performance deterioration can be suppressed. As a result, combustion is stabilized, and exhaust performance, fuel consumption performance, and the like are improved.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various changes in design can be made without departing from the spirit of the present invention described in the claims. It can be done.

1 ... In-cylinder injection engine
101 ... Engine control unit
200 ... Pump drive cam
201 ... Each intake pipe
202 ... Air cleaner
203… Air flow sensor
204 ... Throttle sensor
205 ... Throttle body
206 ... Collector
208 ... Spark plug
209 ... High pressure fuel pump
211 ... Cam angle sensor
216 ... Crank angle sensor
217 ... Water temperature sensor
218 ... Air-fuel ratio sensor
219… Oil temperature sensor
222 ... Ignition coil
225 ... Intake valve
226 ... Exhaust valve
250 ... Fuel tank
251 ... Low pressure fuel pump
252 ... Fuel pressure regulator
253 ... Common rail
254 ... Fuel injection valve
256 ... Fuel pressure sensor
257… Fuel temperature sensor
258 ... Intake air temperature sensor

Claims (11)

A fuel injection control device for an in-cylinder injection engine that performs an arbitrary number of divided injections during one combustion cycle based on the operating state of the engine,
When the engine temperature is equal to or lower than a predetermined temperature, as the total injection amount to be injected during one combustion cycle increases or as the total injection pulse width required during one combustion cycle increases, A fuel injection control device for a direct injection engine characterized by increasing the number of injections.   The fuel injection control device for a direct injection engine according to claim 1, wherein the engine temperature is obtained using at least one of an engine coolant temperature, a fuel temperature, an oil temperature, and an intake air temperature. .   2. The number of injections in one combustion cycle is set by using at least one of a minimum injection pulse width, a minimum injection amount, and an engine speed at which the linearity of the injection amount is maintained. Or a fuel injection control device for a cylinder injection engine according to 2;   4. The fuel injection control device for a direct injection engine according to claim 1, wherein an upper limit number of injections in one combustion cycle is set.   The fuel injection control device for a direct injection type engine according to claim 4, wherein the upper limit number of injections in one combustion cycle is set smaller as the engine temperature becomes higher.   The fuel injection control device for a direct injection engine according to any one of claims 1 to 5, wherein the split injection is performed during an intake stroke.   The fuel injection control device for a direct injection engine according to any one of claims 1 to 6, wherein the divided injection end timing is set before a predetermined period from the compression top dead center.   8. The split injection is prohibited when the split injection is possible when the engine temperature is equal to or higher than the predetermined temperature and the total injection amount is equal to or lower than the predetermined amount. A fuel injection control device for an in-cylinder injection engine according to claim 1.   The in-cylinder injection according to claim 3, wherein when the engine temperature is equal to or higher than the predetermined temperature, the number of injections in one combustion cycle is set without using the minimum injection pulse width and the minimum injection amount. -Type engine fuel injection control device.   The fuel injection control device for a cylinder injection engine according to any one of claims 1 to 9, wherein the number of injections in one combustion cycle is set for each cylinder. A fuel injection control device for an in-cylinder injection engine that performs an arbitrary number of divided injections during one combustion cycle based on the operating state of the engine,
A fuel injection control device for a direct injection engine, wherein the number of injections in one combustion cycle is set so that the penetration of fuel spray injected from the fuel injection valve is within a preset upper and lower limit range .

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