WO2014057825A1

WO2014057825A1 - Engine control device, and engine control method

Info

Publication number: WO2014057825A1
Application number: PCT/JP2013/076464
Authority: WO
Inventors: 健一郎緒方; 岡本　多加志; 西田　茂; 儀信有原; 木原　裕介; 助川　義寛
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2012-10-12
Filing date: 2013-09-30
Publication date: 2014-04-17
Also published as: JP2014077421A

Abstract

Deterioration in fuel economy, combustion performance, and the like due to excessive split injection is suppressed while the amount of attached fuel is decreased by split injection. A split injection start timing (IT1_A) in the intake stroke is determined in accordance with the amount of intake air and the engine rotation speed (S103). Meanwhile, a completion timing (IT1_B) is advanced (S104) when the coolant temperature (TW) is not less than a predetermined water temperature (K_TW) compared with when the coolant temperature (TW) is less than the predetermined water temperature (K_TW), and a total injection period (IT1) is calculated from the start timing (IT1_A) and the completion timing (IT1_B)(S105). On the basis of a required injection period (IT_REQ)(S106) and the number of times of split injection (I_TIMES)(S107), a split injection pulse period (IT1_SP(n)) is calculated (S108) and further a split injection rest period (IT1_RES(n)) is calculated (S109). When the split injection rest period (IT1_RES(n)) is shorter than a required rest period (RES_K), the number of times of split injection (I_TIMES) is decreased (S111→S113).

Description

ENGINE CONTROL DEVICE AND ENGINE CONTROL METHOD

The present invention relates to an engine control device and an engine control method for performing fuel injection by a fuel injection device in a plurality of times in an intake stroke.

Patent Document 1 discloses that in a cylinder direct injection engine, in a situation where the cylinder bore inner wall temperature is below a threshold value, the fuel injection timing is advanced as the cylinder bore temperature increases.
Further, in Patent Document 2, in a cylinder direct injection type engine, when the engine temperature is lower than a predetermined temperature, the fuel is divided into multiple injections in the intake stroke, and the fuel is divided into multiple injections. Is set according to the engine temperature.
Further, in Patent Document 3, in a direct injection type cylinder engine, fuel injection is performed a plurality of times during one cycle during homogeneous operation, and the time interval of each injection is determined according to the engine speed and the engine load. It is disclosed that the injection amount ratio is variable.

JP 2009-102997 A Japanese Patent Laid-Open No. 11-62680 JP 2002-161790 A

By the way, split injection that injects fuel in multiple times weakens the fuel spray penetration (shortens the reach of the spray), and is used in engines and intake ports equipped with injectors that inject fuel directly into the cylinder. In an engine that injects from the installed injector to the opening of the intake valve, the amount of fuel adhering to the inner wall of the cylinder bore and the crown of the piston is reduced, the number of particles PN of particulate matter (PM) PM, and engine oil The amount of oil dilution in which the fuel dissolves can be suppressed.

However, after the engine is warmed up, the fuel temperature also rises and vaporization is promoted. The fuel vapor penetration is weakened by improving the vaporization performance of the fuel itself (spray reach is short). That need is less than when cold.
Here, if split injection is performed after the warm-up as in the cool-down, the power consumption increases due to the increase in the drive current of the injector, the resulting deterioration in fuel consumption, the increase in the drive sound of the injector, the injection of the injector It may cause deterioration. Furthermore, excessive split injection may deteriorate the mixing state of fuel and intake air in the combustion chamber, and may deteriorate the combustion performance.

The present invention has been made in view of the above problems, and provides an engine control apparatus and control method capable of suppressing deterioration in fuel consumption, combustion performance, and the like due to excessive divided injection while reducing the amount of adhered fuel by divided injection. The purpose is to provide.

Therefore, the engine control device of the present invention determines the total injection period from the start of the first injection to the completion of the final injection in the intake stroke divided injection in which the fuel injection by the fuel injection device is performed in a plurality of times in the intake stroke. The engine was shortened as the engine temperature increased.
In the engine control method of the present invention, the engine temperature is detected in an engine equipped with a fuel injection device that directly injects fuel into the combustion chamber, and fuel injection is performed multiple times in the intake stroke. The total injection period from the start of the first injection to the completion of the final injection is shortened as the engine temperature rises, and the fuel injection by the fuel injection device is performed in a plurality of times during the total injection period of the intake stroke I made it.

According to the present invention, by shortening the total injection period in accordance with the increase in engine temperature, it is possible to weaken the penetration by split injection at the time of cold, and to reduce the PN and oil dilution amount by reducing the amount of attached fuel, After the warm-up, it is possible to suppress a decrease in fuel consumption and combustion performance by reducing the number of injections and shortening the pause period.

1 is a system configuration diagram of an automobile engine system in an embodiment of the present invention. It is a system block diagram which shows the structure of ECU in embodiment of this invention. It is a characteristic view which shows an example of the injection command value of multiple times in embodiment of this invention. It is a figure which shows the control map which calculates the command value of injection start time IT1_A in embodiment of this invention. It is a figure which shows the control map which calculates the frequency | count of injection I_TIMES in embodiment of this invention. It is a figure which shows the control map which calculates the request | requirement injection period IT_REQ in embodiment of this invention. It is a figure which shows the control map which calculates injection completion time IT1_B in embodiment of this invention. It is a functional block diagram which shows the structure of the division | segmentation injection permission determination part in embodiment of this invention. It is a time chart which shows operation | movement of the division | segmentation injection permission determination part in embodiment of this invention. It is a figure for demonstrating the determination process of the rotation fluctuation | variation in embodiment of this invention. It is a figure which shows the correction | amendment operation | movement of the division | segmentation injection permission determination based on the rotation fluctuation | variation in embodiment of this invention. It is a functional block diagram which shows the process which calculates the injection start of the total injection period of an intake stroke, completion time, etc. in embodiment of this invention. It is a time chart which shows calculation operations, such as injection start of the total injection period of an intake stroke, and completion time in an embodiment of the present invention. It is a functional block diagram which shows the structure of the division | segmentation injection control calculating part in embodiment of this invention. It is a time chart which shows operation | movement of the division | segmentation injection control calculating part in embodiment of this invention. It is a functional block diagram which shows the structure of the division | segmentation injection determination part in embodiment of this invention. It is a time chart which shows operation | movement in case the division | segmentation injection determination part in embodiment of this invention outputs a division | segmentation injection control command value. It is a time chart which shows operation | movement when the division | segmentation injection determination part in embodiment of this invention outputs division | segmentation injection frequency correction command value. It is a time chart which shows operation | movement in case the division | segmentation injection determination part in embodiment of this invention outputs a fuel pressure control command value. It is a flowchart which shows the flow of control by ECU in embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an engine (internal combustion engine) to which a control device according to the present invention is applied.
In FIG. 1, an engine 100 is an automobile engine that performs spark ignition combustion, and an intake pipe 9 of the engine 100 includes an airflow sensor 3 that measures an intake air amount and an intake pipe pressure (intake air amount). An electronically controlled throttle 5 for adjustment and an intake air temperature sensor 4 for measuring the temperature of intake air are provided.
Instead of the airflow sensor 3, an intake air pressure sensor (boost sensor) for detecting the intake pipe internal pressure can be provided.

The engine 100 also includes an injector (fuel injection valve) 6 that is a fuel injection device that directly injects fuel into the combustion chamber 14, and an ignition plug 16 that performs spark ignition in the combustion chamber 14. A variable intake / exhaust valve 10 for adjusting the inflow of intake air into the chamber 14 and the exhaust from the combustion chamber 14 is provided.
Further, a common rail 8 for supplying fuel to the injector 6 by being connected to the injector 6 and a fuel pump 7 for pumping fuel to the common rail 8 are provided. The common rail 8 detects the temperature of the fuel. A fuel temperature sensor 21 is provided.

Further, the exhaust pipe 17 of the engine 100 includes a three-way catalyst 18 that is an exhaust gas purification device that purifies the exhaust, an exhaust gas temperature sensor 19 that measures the temperature of the exhaust gas upstream of the three-way catalyst 18, and a three-way battery. An air-fuel ratio sensor 20 for detecting the air-fuel ratio of the exhaust is provided upstream of the catalyst 18.
Instead of the air-fuel ratio sensor 20, an oxygen concentration sensor that detects rich and lean of the exhaust air-fuel ratio with respect to the stoichiometric air-fuel ratio can be provided.

The crankshaft 12 of the engine 100 is provided with a crank angle sensor 13 that detects the angular position of the crankshaft 12.
A cooling water temperature sensor 15 that detects the cooling water temperature of the engine 100 is also provided.
The cooling water temperature is a temperature representative of the temperature of the engine 100, but the temperature representative of the engine temperature is not limited to the cooling water temperature, and the temperature of the engine 100 such as lubricating oil, cylinder block, intake air temperature, in-cylinder gas temperature, etc. The temperature that changes in correlation with can be set to a temperature representative of the temperature of engine 100.

The exhaust temperature sensor 19, air-fuel ratio sensor 20, cooling water temperature sensor 15, crank angle sensor 13, intake air temperature sensor 4, airflow sensor 3 signal, and accelerator pedal depression amount, that is, an accelerator position for detecting an accelerator opening degree. A signal from the opening sensor 2 is sent to an engine control unit (hereinafter referred to as ECU) 1 having a microcomputer.
The ECU 1 calculates the required torque based on the output signal of the accelerator opening sensor 2, that is, the accelerator opening, and determines the position of the piston 11 and the engine speed based on the output signal of the crank angle sensor 13. Calculate.

The ECU 1 then opens the throttle 5, the injection pulse period of the injector 6, the ignition timing of the spark plug 16, the valve of the variable intake / exhaust valve 10 based on the operating state of the engine 100 detected from the outputs of the various sensors. An operation amount of the engine 100 such as an opening / closing timing is calculated.
The ECU 1 converts the calculated injection pulse period into a valve opening pulse signal of the injector 6 and sends it to the injector 6, and sends the spark plug drive signal to the spark plug 16 (energization to the ignition coil) so that ignition is performed at the calculated ignition timing. The calculated throttle opening is sent to the throttle 5 as a throttle drive signal, and a drive signal corresponding to the calculated valve opening / closing timing is sent to the variable intake / exhaust valve 10.

Then, fuel is injected from the injector 6 to the air flowing into the combustion chamber 14 from the intake pipe 9 through the variable intake / exhaust valve 10 to form an air-fuel mixture, and the air-fuel mixture is ignited at a predetermined ignition timing. Explosion is caused by a spark generated from the engine 16, and the piston 11 is pushed down by the combustion pressure to become a driving force of the engine 100.
The exhaust after the explosion is sent from the combustion chamber 14 to the three-way catalyst 18 through the variable intake exhaust valve 10 and the exhaust pipe 17, and the exhaust components are purified in the three-way catalyst 18 and then discharged.

FIG. 2 is a block diagram illustrating an example of the configuration of the ECU 1.
The output signals of the accelerator opening sensor 2, the airflow sensor 3, the intake air temperature sensor 4, the crank angle sensor 13, the cooling water temperature sensor 15, the exhaust gas temperature sensor 19, the air-fuel ratio sensor 20, and the fuel temperature sensor 21 are sent to the input circuit 30a of the ECU 1. Entered. However, the input signal to the input circuit 30a is not limited to the output signal from the sensor.

The input signal of each sensor input to the input circuit 30a is sent to the input port of the input / output port 30b, and the input signal sent to the input port of the input / output port 30b is stored in the RAM 30c for arithmetic processing by the CPU 30e. Provided.
A control program describing the arithmetic processing contents in the CPU 30e is written in advance in the ROM 30d.
A value indicating the operation amount of each actuator calculated according to the control program is stored in the RAM 30c, then sent to the output port of the input / output port 30b, and sent to each actuator via each drive circuit.

In this embodiment, the drive circuit includes a throttle drive circuit 30f, an injector drive circuit 30g, an ignition output circuit 30h, and a variable valve drive circuit 30i. These drive circuits include the throttle 5, the injector 6, and the ignition plug. 16. The variable intake / exhaust valve 10 is driven.
Although the ECU 1 of the present embodiment includes a drive circuit, the present invention is not limited to such a configuration, and the drive circuit can be provided separately from the ECU 1. For example, the drive circuit is provided integrally with the throttle 5 or the like. be able to.

FIG. 3 shows an example of the injection pulse signal in the divided injection in which the fuel injection per cycle by the injector 6 is performed in a plurality of times as the injection pulse signal (valve opening pulse signal) sent to the injector 6.
In FIG. 3, the vertical axis represents the injection pulse voltage IT (valve opening drive voltage), and the horizontal axis represents the elapsed time. Further, BDC indicates the bottom dead center of the piston 11, TDC indicates the top dead center of the piston 11, and the strokes of the engine 100 (exhaust stroke, intake stroke, compression stroke, expansion stroke) corresponding to the elapsed time are illustrated below. It is shown in

As shown in FIG. 3, the ECU 1 can cause the fuel injection by the injector 6 to be performed in a plurality of times from the intake stroke to the compression stroke of the engine 100. In the example shown in FIG. In each stroke, three injection pulses are shown.
Further, the ECU 1 performs from the first injection start to the completion of the final injection in the divided injection in the intake stroke (the divided injection performed from the intake TDC to the intake BDC, hereinafter referred to as the intake stroke divided injection). A process of shortening the total injection period (intake stroke total injection period) IT1 in accordance with the increase in engine temperature is performed, and the control of the divided injection will be described in detail below.
Note that the length of the total injection period IT1 depending on the engine temperature indicates a difference in the total injection period IT1 under the same engine load and engine speed.

Here, the rising timing of the initial pulse of the multiple injection pulses in the intake stroke divided injection is the injection start timing IT1_A, and the ON period from the rising timing to the falling timing that follows is the initial injection pulse period IT1_SP (1) And the off period from the falling time to the rising time of the next pulse that follows is the injection suspension period IT1_RES (1). Further, the falling timing of the final pulse in the intake stroke divided injection is set as the injection completion timing IT1_B, and the ON period between the injection completion timing IT1_B and the rising timing of the final pulse is set as the final injection pulse period IT1_SP (n In addition, a period between the first injection start timing IT1_A and the final injection completion timing IT1_B is defined as a total injection period IT1 of the intake stroke divided injection.

Similarly, in the compression stroke division injection performed in the compression stroke (between intake BDC and compression TDC), the first injection start timing (rise timing of the first pulse) and the final injection among the plurality of injection pulses. A period between the completion timings (falling timing of the last pulse) is defined as a total injection period IT2 of the compression stroke division injection.
As described above, if the fuel is injected in a plurality of times, the penetration of the fuel spray becomes weak (the spray reach distance is short), the amount of fuel adhering to the inner wall of the cylinder bore and the crown of the piston 11 is reduced, and the particulate form The number of discharged particles PN of the substance (particulate matter) PM and the amount of oil dilution in which the fuel dissolves in the engine oil can be suppressed.

Below, control of intake stroke division injection by ECU1 is explained in detail.
The ECU 1 refers to the control maps shown in FIGS. 4 and 5, and command values for the injection start timing IT1_A of the total injection period IT1 of the intake stroke divided injection and the number of injections I_TIMES (number of divisions) in the intake stroke divided injection. Is calculated.
FIG. 4 shows a control map for storing the injection start timing IT1_A of the total injection period IT1 of the intake stroke, using the intake air amount QA (engine load) and the engine speed NE as variables.
The injection start timing IT1_A is expressed as a crank angle (deg) from the intake TDC, for example.

Here, the injection start timing IT1_A has a characteristic that the injection start timing IT1_A is later, that is, the crank angle position is more retarded and close to the intake BDC at the time of low rotation and low load with respect to high rotation and high load. This control map is set, and the injection start timing IT1_A is advanced more as the engine load becomes higher and the engine rotation speed becomes higher.
The advance angle of the injection start timing IT1_A starts fuel injection in a state where the piston 11 is closer to the top dead center TDC, and increases the amount of fuel adhering to the crown surface of the piston 11. On the other hand, at the time of high rotation and high load, the demand for the total injection time becomes long and the time for the total injection period IT1 becomes short, so that it is necessary to start fuel injection early.

Therefore, the injection start timing IT1_A is changed according to the intake air amount QA (engine load) and the engine speed NE so that the fuel injection can be started at a position as close as possible to the bottom dead center BDC.
FIG. 5 also stores the number of injection pulses, that is, the number of injections I_TIMES, during the total injection period IT1 of the intake stroke divided injection, using the intake air amount QA (engine load) and the engine speed NE as variables. A control map is shown.

Here, in FIG. 5, as a representative example, the number of injections of 1 to 5 is assigned to each operation region divided by the engine load and the engine rotational speed NE, but for example, the number of injections I_TIMES in all regions. The number of injections I_TIMES can be increased as the engine load increases and the engine speed increases.
The number of injections I_TIMES can inject the required fuel in consideration of the requirement of the fuel injection amount, the condition of the intake flow velocity, etc., and can weaken the penetration under the condition that the fuel spray easily adheres to the piston crown surface. As previously adapted.

Further, the ECU 1 calculates the command value of the required injection period IT_REQ and the injection completion timing IT1_B of the total injection period IT1 in the intake stroke divided injection with reference to the control maps shown in FIGS.
FIG. 6 shows a control map for storing the required injection period IT_REQ (ms) in the intake stroke with the intake air amount QA (engine load), fuel pressure FP, and air-fuel ratio AF as variables.

Here, the required injection period IT_REQ is an injection time (a valve opening time of the injector 6) required to form an air-fuel ratio AF mixture by one injection without performing split injection, and the intake air amount The required injection period IT_REQ is set longer as the QA (cylinder intake air amount) increases.
Further, when the fuel pressure FP is low, the injection amount per unit valve opening time of the injector 6 decreases, so that the time for injecting the same amount of fuel becomes longer than when the fuel pressure FP is high. Therefore, even if the intake air amount QA is the same, the required injection period IT_REQ is made longer when the fuel pressure FP is low.

Also, if the air-fuel ratio AF setting is richer, more fuel is injected even if the intake air amount QA is the same.Therefore, as the air-fuel ratio AF setting becomes richer, the required injection period IT_REQ is reduced. Make it longer.
By setting the required injection period IT_REQ as described above, it is possible to set the required injection period IT_REQ corresponding to the amount of fuel necessary to form the target air-fuel ratio mixture.

FIG. 7 shows a control map (conversion table) for storing the injection completion timing IT1_B according to the coolant temperature TW representing the engine temperature.
The injection completion timing IT1_B is expressed as a crank angle (deg) from the intake TDC, for example.

Here, compared with the injection completion timing IT1_B when the cooling water temperature TW is lower than the predetermined water temperature K_TW, the predetermined water temperature K_TW is set so that the injection completion timing IT1_B when the cooling water temperature TW is equal to or higher than the predetermined water temperature K_TW is advanced to the intake TDC side. As a boundary, the injection completion timing IT1_B is set to a different value.
In other words, compared with the case where the cooling water temperature TW is lower than the predetermined water temperature K_TW, the injection completion timing IT1_B when the cooling water temperature TW is equal to or higher than the predetermined water temperature K_TW is advanced to thereby make the total injection period IT1 of the intake stroke divided injection the cooling water temperature. It shortens with respect to the rise of TW (engine temperature).

The predetermined water temperature K_TW is a threshold value for determining whether or not the fuel vaporization is sufficiently accelerated, and is a state after warm-up in which the fuel vaporization is sufficiently promoted, Whether or not the fuel vaporization is insufficient is determined based on a comparison between the cooling water temperature TW and the predetermined water temperature K_TW. The predetermined water temperature K_TW can be set based on the distillation temperature of the fuel, and can be set to about 70 ° C. (50% distillation temperature T50), for example.

Note that the injection completion timing IT1_B can be set based on the estimated value of the coolant temperature TW instead of the detected value of the coolant temperature TW. Further, as a representative temperature of the engine, the injection completion timing IT1_B can be set based on the detected value or estimated value of the lubricating oil temperature, the intake air temperature, and the fuel temperature instead of the cooling water temperature TW. Set to advance (accelerate) the injection completion timing IT1_B at high temperatures compared to low temperatures.
Further, in the characteristic that the injection completion timing IT1_B at the high temperature is advanced as compared with the low temperature, the injection completion timing IT1_B can be changed in multiple stages with respect to the temperature change.

The injection start timing IT1_A is determined according to the intake air amount QA (engine load) and the engine speed NE as described above, whereas the injection completion timing IT1_B is changed according to the engine temperature as described above. Therefore, even when the intake air amount QA (engine load) and the engine rotational speed NE are the same, the total injection period IT1 of the intake stroke divided injection is shorter when the engine temperature is high than when the engine temperature is low.
As the engine temperature rises, the fuel temperature also rises. As the fuel temperature rises, it becomes easier to vaporize, the fuel spray penetration becomes weaker (the spray reach distance is shorter), and the split injection to weaken the penetration relatively. Therefore, the total injection period IT1 is shortened with respect to the increase in the engine temperature, so that the pause period during the divided injection is shortened and the number of injections is reduced.

As a result, when the fuel temperature rises as the engine temperature rises, the fuel can be prevented from adhering to the piston crown surface, etc., and excessive split injection can be suppressed, improving the mixed state of fuel and intake air In addition, the fuel consumption can be improved by reducing the power consumption in the injector 6.
That is, if the total injection period IT1 is shortened without reducing the number of injections, the pause period in the divided injection is shortened, and the mixed state of fuel and intake air is improved. Also, if the number of injections is reduced as the total injection period IT1 is shortened, power consumption is reduced due to a decrease in injector drive current, fuel efficiency is improved accordingly, and further, drive noise of the injector is reduced, and deterioration of the injector is suppressed. Can be achieved.

Further, if the total injection period IT1 is shortened by the advance angle of the injection completion timing IT1_B, the completion of the divided injection is accelerated, and in the subsequent intake stroke, fuel and intake air can be mixed, and the mixing state is improved. The If the mixed state is improved, the combustibility is improved and the exhaust properties are improved.
In other words, in response to the increase in engine temperature (fuel temperature), the total injection period IT1 is shortened, so that at least one of the shortened divided injection suspension period and the reduced number of injections is performed and adhered by divided injection. While reducing the amount of fuel, the deterioration of fuel consumption and combustion performance due to excessive split injection is suppressed.

FIG. 8 is a functional block diagram showing split injection permission determination processing (split injection permission flag setting processing) in the ECU 1.
In FIG. 8, the split injection permission determination unit 41 is equipped with an accelerator opening signal APO obtained from the accelerator opening sensor 2, an engine rotational speed NE based on a signal obtained from the crank angle sensor 13, and the engine 100. The vehicle speed VX, which is the travel information of the automobile, the exhaust temperature TC obtained from the exhaust temperature sensor 19, the required exhaust temperature TC_K written in the ROM 30d of the ECU 1, and the like are input. Then, based on these signals, the split injection permission determination unit 41 determines whether or not it is in an operation state in which the split injection is permitted, and sets a split injection permission flag when the operation state in which the split injection is permitted.

FIG. 9 is a time chart showing an example of the operation of the split injection permission determination unit 41. The accelerator opening signal APO with respect to the elapsed time when the crankshaft 12 starts to rotate, that is, when the time when the engine 100 starts is 0. Changes in engine speed NE, vehicle speed VX, catalyst temperature TC, and split injection permission flag are shown.
In the example shown in FIG. 9, the engine speed NE rises with the startup of the engine 100 and then enters a stable period. During the stable period, the catalyst temperature TC rises, and the catalyst temperature TC becomes the required temperature TC_K at time t1. In other words, when the catalyst warm-up is completed, the split injection permission flag is raised at the time t2 when an arbitrary delay time has elapsed from the time t1, and the split injection is permitted. Then, if the catalyst temperature TC maintains a state equal to or higher than the required temperature TC_K, the split injection permission state is maintained, and when the catalyst temperature TC falls below the required temperature TC_K, the split injection permission flag is dropped and the split injection permission flag is set. Prohibit implementation.

In the configuration in which the split injection permission flag is set by determining completion of catalyst warm-up, the exhaust temperature detected by the exhaust temperature sensor 19 and other values such as the accelerator opening signal APO, the engine rotational speed NE, the vehicle speed VX, etc. In consideration of the conditions, it can be determined whether or not the catalyst warm-up is completed.
Further, instead of the exhaust temperature detected by the exhaust temperature sensor 19, the coolant temperature TW can be used for determining whether the catalyst is warmed up.

FIGS. 10 and 11 are diagrams for explaining the correction operation of the split injection permission determination (catalyst warm-up completion determination).
The horizontal axis in FIG. 10 indicates the time during which the injection command is executed during the total injection period of the compression stroke, and further indicates the time when the injection command is completed during the total injection period of the compression stroke as the end time.
In the present embodiment, during the catalyst warm-up operation immediately after the engine is started, injection is performed in the compression stroke, and the time during which the injection command is executed during the total injection period of the compression stroke is as follows. This corresponds to the catalyst warm-up operation control time, and the end time indicates the timing at which the catalyst warm-up completion is determined based on the required temperature TC_K.

In addition, the vertical axis of FIG. 10 indicates the variation (hereinafter referred to as the rotation change amount) σNE of the engine rotation speed NE. The rotation change amount σNE is, for example, a change amount during the detection period of the engine rotation speed NE. Further, SIGMA_K which is a threshold value for the rotation change amount σNE is a value written in the ROM 30d in the ECU 1.
When the rotation change amount σNE becomes a value equal to or greater than the threshold value SIGMA_K during the time when the injection command is executed during the total injection period of the compression stroke (during the catalyst warm-up operation), as shown in FIG. The temperature TC_K (or the threshold value of the coolant temperature in the catalyst warm-up completion determination) is shifted to a higher temperature side to obtain a correction required temperature TC_K, and the permission determination for split injection is performed based on the correction request temperature TC_K.

That is, even if the catalyst warm-up completion is determined based on the required temperature TC_K, if the rotational change amount σNE during the previous catalyst warm-up operation is larger than the threshold value SIGMA_K, the required temperature TC_K is shifted to a higher temperature side. This delays the start of split injection and extends the catalyst warm-up operation time.
In the catalyst warm-up operation immediately after the start of the engine 100, if the combustion of the engine 100 is unstable and the rotational fluctuation is larger than the setting, there is a possibility that a larger rotational fluctuation may occur if the split injection is permitted. Therefore, the required temperature TC_K (or the threshold value of the cooling water temperature in the catalyst warm-up completion determination) is shifted to a higher temperature side so that the catalyst warm-up completion is determined at a higher temperature so that the catalyst warm-up operation is longer. The intake stroke split injection is started relatively on the higher temperature side.

As a result, the catalyst can be sufficiently warmed up, and the emission characteristics can be improved by permitting the split injection as early as possible while suppressing the occurrence of large rotational fluctuations.
Note that the amount of shift of the required temperature TC_K to the higher temperature side can be increased as the rotational change amount σNE during the catalyst warm-up operation increases.

FIG. 12 is a functional block diagram showing calculation processing of the injection start timing IT1_A, the number of injections I_TIMES, the required injection period IT_REQ, and the injection completion timing IT1_B in the ECU 1.
In FIG. 12, the ECU 1 includes an injection start timing calculation unit 51, a divided injection number calculation unit 52, a required injection period calculation unit 53, and an injection completion timing calculation unit 54 as calculation logic units, and inputs to these calculation logic units. The intake air amount QA, engine speed NE, fuel pressure FP, air-fuel ratio AF, required air-fuel ratio AF_K, cooling water temperature TW, and predetermined water temperature TW_K are set.
The required air-fuel ratio AF_K and the predetermined water temperature TW_K are values written in advance in the ROM 30d.

Then, the injection start timing calculation unit 51 calculates and outputs the injection start timing IT1_A of the total injection period IT1 of the intake stroke based on the intake air amount QA and the engine speed NE according to the control map shown in FIG.
The divided injection number calculation unit 52 calculates and outputs the divided injection number I_TIMES based on the intake air amount QA and the engine speed NE according to the control map shown in FIG.

The required injection period calculation unit 53 calculates and outputs the required injection period IT_REQ based on the intake air amount QA, the fuel pressure FP, the air-fuel ratio AF, and the required air-fuel ratio AF_K according to the control map shown in FIG.
The injection completion timing calculation unit 54 calculates and outputs the injection completion timing IT1_B of the total injection period IT1 of the intake stroke based on the cooling water temperature TW and the predetermined water temperature TW_K according to the control map shown in FIG.

FIG. 13 is a time chart for explaining the operation of the logic for calculating the injection start timing IT1_A, the number of injections I_TIMES, the required injection period IT_REQ, and the injection completion timing IT1_B.
In FIG. 13, the intake air amount QA decreases from time t1 to time t2, and the engine rotational speed NE decreases as the intake air amount QA decreases, and the intake air amount QA and the engine rotational speed NE decrease. The injection start timing IT1_A of the total injection period IT1 of the intake stroke is retarded, the number of injections I_TIMES is decreased, and the required injection period IT_REQ is shortened.

Further, when the cooling water temperature TW rises and exceeds the predetermined water temperature TW_K at time t3, the injection completion timing IT1_B is advanced as compared to the case where the cooling water temperature TW is below the predetermined water temperature TW_K.
In FIG. 13, the air-fuel ratio AF becomes lean between time t1 and time t2 due to the execution of the deceleration fuel cut.

FIG. 14 is a functional block diagram showing calculation processing of the divided injection pulse period IT1_SP (n), the divided injection suspension period IT1_RES (n), and the total injection period IT1 in the total injection period IT1 of the intake stroke in the ECU 1.
In FIG. 14, the divided injection control calculation unit 61 for calculating the divided injection pulse period IT1_SP (n), the divided injection suspension period IT1_RES (n), and the total injection period IT1 includes an injection start timing IT1_A, an injection completion timing IT1_B, and a required injection. The period IT_REQ, the divided injection number I_TIMES, and the engine speed NE are input.

The divided injection control calculation unit 61 then performs the divided injection pulse period IT1_SP (n), the divided injection pause based on the following formula based on the injection start timing IT1_A, the injection completion timing IT1_B, the required injection period IT_REQ, and the divided injection number I_TIMES. The period IT1_RES (n) and the total injection period IT1 are calculated and output.
In the following formula, n indicates the divided injection number I_TIMES.

IT1_SP (n) = (IT_REQ / I_TIMES) Expression (1)
IT1_RES (n) = (IT1−Σ (IT1_SP (n))) / (n−1) (2)
IT1 = (IT1_B-IT1_A) / (NE / 60 / 1e-3 * 360) (3)

In the equation (1), by dividing the required injection period IT_REQ (ms) by the divided injection number I_TIMES, the valve opening time (ms) of the injector 6 per divided injection is set as the divided injection pulse period IT1_SP (n). calculate.
Further, in Expression (2), the total injection time (ms) of the injector 6 for each injection of the divided injection is subtracted from the total injection period IT1 (ms) calculated in Expression (3) to obtain the total injection. Calculate the total pause time (ms) in period IT1, and divide this by one less than the number of split injections I_TIMES to start the next split injection after finishing one split injection The divided injection suspension period IT1_RES (n), which is the time (ms) until the start, that is, the time during which the injector 6 is closed during the divided injection, is obtained.
Further, the expression (3) converts the crank angle between the injection start timing IT1_A and the injection completion timing IT1_B into the total injection period IT1 (ms) based on the engine rotational speed NE (rpm) at that time.

FIG. 15 is a time chart for explaining an example of the operation of the divided injection calculation unit 61. Between time t0 and time t1, the number of divided injections I_TIMES = 4 and the required injection period IT_REQ = 2.0 (ms). Therefore, the first divided injection pulse period IT1_SP (1) to the fourth divided injection pulse period IT1_SP (4) have a value of about 0.5 ms, from the divided injection suspension period IT1_RES (1) to the divided injection suspension period IT1_RES (3). Is a constant value.
If the number of divided injections I_TIMES is reduced to 3 at time t1 from the state where the number of divided injections I_TIMES = 4, the divided injection pulse period IT1_SP (4) is made zero and the fuel injected in the fourth injection is reduced. By dividing from the first to the third time, the divided injection pulse period IT1_SP (1) to the divided injection pulse period IT1_SP (3) is increased.

Further, when the required injection period IT_REQ (ms) decreases between time t1 and time t2, the divided injection pulse period IT1_SP (n) decreases.
Furthermore, when the cooling water temperature TW becomes equal to or higher than the predetermined water temperature TW_K at time t3 and the injection completion timing IT1_B of the total injection period of the intake stroke is advanced to the intake TDC side, the total injection period IT1 of the intake stroke is shortened, so that the division is performed. The divided injection suspension period IT1_RES (1) between the injection pulse periods IT1_SP (1) and IT1_SP (2) is shortened.

FIG. 16 is a functional block diagram showing calculation processing of the divided injection command value, the divided injection number correction command value, and the fuel pressure control command value in the ECU 1.
The divided injection determination unit 71 shown in FIG. 16 receives the divided injection number I_TIMES, the divided injection suspension period IT1_RES (n), the requested suspension period RES_K written in the ROM 30d, and the total injection period IT1 of the intake stroke, and the divided injection command value The divided injection number correction command value and the fuel pressure control command value are calculated and output.

Here, if the number of divided injections I_TIMES is one, the required fuel amount is injected by opening the injector 6 only once in the total injection period IT1, that is, in order to inject the required fuel amount. The injection amount per unit valve opening time is set such that the pulse period of time is not longer than the total injection period IT1, and the command value of the fuel pressure that obtains the injection amount per unit valve opening time is calculated and output.
Also, when the divided injection suspension period IT1_RES (n) is below the lower limit required suspension period RES_K, the divided injection frequency I_TIMES is decreased to set the divided injection suspension period IT1_RES (n) that exceeds the requested suspension period RES_K. To be.

That is, when the divided injection suspension period IT1_RES (n) becomes less than the requested suspension period RES_K, the next injection command is output within the valve closing operation period of the injector 6, and the fuel measurement accuracy is lowered. To do. Therefore, when the divided injection suspension period IT1_RES (n) is less than the requested suspension period RES_K, the divided injection suspension period IT1_RES (n) is extended to exceed the requested suspension period RES_K by reducing the number of divided injections I_TIMES. . As a result, the amount of fuel injected from the injector 6 is set to an amount proportional to the divided injection pulse period IT1_SP (n), and a decrease in control accuracy of the air-fuel ratio can be suppressed.
When the divided injection frequency I_TIMES and the divided injection suspension period IT1_RES (n) are determined, a divided injection control command value corresponding to the determination is output.

FIG. 17 is a time chart illustrating an operation example when the divided injection determination unit 71 outputs a divided injection control command value.
In the example shown in FIG. 17, the divided injection suspension period IT1_RES (1), the divided injection suspension period IT1_RES (1), the divided injection suspension period IT1_RES (1), IT1_RES (2), IT1_RES (3), and the requested suspension period RES_K are input. Both IT1_RES (2) and IT1_RES (3) are longer than the requested suspension period RES_K. Therefore, both the division number determination flag and the pause period error flag are turned off (OFF), and the divided injection pulse periods IT1_SP (1), IT1_SP (2), IT1_SP (3), IT1_SP (4), and the divided injection pause The periods IT1_RES (1), IT1_RES (2), and IT1_RES (3) are output as they are as the divided injection control command values without change.

On the other hand, FIG. 18 is a time chart showing an operation example when the divided injection determination unit 71 outputs the divided injection number correction command value (changes the divided injection number), and the solid line does not perform the divided injection number correction. In this case, the dotted line indicates the case where the division injection number correction is performed.
In FIG. 18, when the divided injection number I_TIMES, the divided injection suspension period IT1_RES (1), IT1_RES (2), IT1_RES (3), and the requested suspension period RES_K are set to twice. The divided injection suspension period IT1_RES (1), which is a suspension period between the first injection and the second injection, is less than the required suspension period RES_K.

In this case, if the divided injection control command value is output in the divided injection suspension period IT1_RES (1) that is less than the requested suspension period RES_K without performing the division injection frequency correction, the injector 6 lacks the divided injection suspension period IT1_RES (1). As a result, the responsiveness to the divided injection pulse periods IT1_SP (1) and IT1_SP (2) cannot be compensated, and the exhaust becomes worse due to variations in the actual injection amount.
Therefore, when the divided injection suspension period IT1_RES (1) becomes less than the required suspension period RES_K, the suspension period error flag is raised, and the divided injection count I_TIMES is set so that the divided injection suspension period IT1_RES (1) is equal to or greater than the requested suspension period RES_K. Reduce from 2 times to 1 time. Then, the divided injection pulse period IT1_SP (1) is recalculated using the reduced divided injection frequency I_TIMES, and a divided injection control command value is output based on the value of the divided injection pulse period IT1_SP (1).

Thereby, the variation (error) of the actual injection amount due to the shortage of the divided injection suspension period IT1_RES (n) in the injector 6 can be suppressed.
The requested suspension period RES_K is set in advance as a minimum suspension period in which the actual injection amount variation can be within an allowable level.

The example shown in FIG. 18 shows an example in which the divided injection number I_TIMES is reduced to one under the condition of two times, but the same correction is performed even if the divided injection number I_TIMES is three times or more. Further, since the example shown in FIG. 18 shows a case where the divided injection number I_TIMES is corrected to one, the divided number determination flag is ON, and the required fuel amount is obtained by one injection without performing the divided injection. Indicates that this is to be injected.

FIG. 19 is a time chart illustrating an operation example in the case where the split injection determination unit 71 outputs the fuel pressure control command value.
If the split count determination flag is ON and the pause period error flag is ON, the split injection count I_TIMES is 1, and if the total injection period IT1 and the split injection pulse period IT1_SP (1) in the intake stroke are different, the split injection pulse A command value for correcting the fuel pressure is output so that the period IT1_SP (1) is within the total injection period IT1 of the intake stroke.
As a result, fuel injection is not performed in an injection pulse period longer than the total injection period IT1, and one fuel injection is performed within the total injection period IT1, thereby suppressing the amount of adhesion, fuel mixing, etc. The fuel injection can be carried out in an optimum period, and the increase in PM, PN emission amount and oil dilution amount can be suppressed, and the deterioration of fuel consumption and exhaust performance can be suppressed.

The flow of the split injection control by the ECU 1 described above will be described according to the flowchart of FIG.
The routine shown in the flowchart of FIG. 20 is repeatedly executed by the ECU 1 at a predetermined cycle.
First, in step S101, state quantities indicating the operating state of the engine 100 such as the engine rotation speed NE, the intake air amount QA, and the cooling water temperature TW are read, and further, the threshold value SIGMA_K, the required temperature TC_K, and the predetermined water temperature written in the ROM 30d. Read a constant such as TW_K.

In step S102, it is determined whether or not a condition for permitting split injection is satisfied. If a permit condition such as the catalyst temperature TC is equal to or higher than the required temperature TC_K is satisfied, the split injection permission flag is set. And go to step S103 and subsequent steps. Here, if the rotational fluctuation of the engine 100 is large during the catalyst warm-up operation, the temperature condition for permitting the split injection is set higher than the standard to delay the start of the split injection.
On the other hand, when the split injection permission condition is not satisfied (during the catalyst warm-up operation), the process returns to step S101 and the state quantity is read again.

In step S103, the injection start time IT1_A obtained by referring to the control map of FIG. 4 is read. In step S104, the injection completion time IT1_B obtained by referring to the control map of FIG. 7 is read.
In step S105, the total injection period IT1 (ms) obtained by converting the crank angle between the injection start timing IT1_A and the injection completion timing IT1_B into time is read according to the above equation (3).

Further, in step S106, a required injection period IT_REQ (ms) for injecting the required fuel amount at the standard fuel pressure is read. In step S107, the divided injection number I_TIMES obtained by referring to the control map of FIG. 5 is read. .
In step S108, based on the required injection period IT_REQ (ms) and the divided injection frequency I_TIMES, the divided injection pulse period IT1_SP (n) calculated according to the above-described equation (1) is read.

In step S109, based on the total injection period IT1, the divided injection pulse period IT1_SP (n), and the number of divided injections I_TIMES, the divided injection suspension period IT1_RES (n) calculated according to the above equation (2) is read.
In step S110, it is determined whether or not the divided injection number I_TIMES is 2 or more. If the divided injection number I_TIMES is 2 or more, the process proceeds to step S111, and the divided injection suspension period IT1_RES (n) is the required suspension period. Judge whether it is longer than RES_K.

When the divided injection suspension period IT1_RES (n) is longer than the requested suspension period RES_K, it is not necessary to change the divided injection number I_TIMES. Therefore, the process proceeds to step S112 as it is from the injection start timing IT1_A to the injection completion timing IT1_B. In the meantime, the divided injection of the divided injection frequency I_TIMES is performed.
On the other hand, when the divided injection suspension period IT1_RES (n) is shorter than the requested suspension period RES_K, if the divided injection is performed with the setting as it is, the variation in the injection amount is large, the air-fuel ratio control accuracy decreases, and the exhaust property Therefore, in order to make the divided injection suspension period IT1_RES (n) longer than the requested suspension period RES_K, the process proceeds to step S113 and correction is performed to reduce the number of divided injections I_TIMES by one.

When the correction for reducing the divided injection number I_TIMES by one is performed, in order to calculate the divided injection pulse period IT1_SP (n) and the divided injection suspension period IT1_RES (n) based on the divided injection number I_TIMES after the subtraction, step S107. Return to.
If the number of divided injections I_TIMES after the reduction is two or more and the divided injection number of times I_TIMES is reduced, the divided injection suspension period IT1_RES (n) becomes longer than the requested suspension period RES_K, step S115. Proceed to, and split injection is performed.

On the other hand, when the number of divided injections I_TIMES after the reduction is 1 and when the number of divided injections I_TIMES obtained with reference to the control map of FIG. 5 is 1, the process proceeds from step S110 to step S114.
In step S114, the fuel pressure is increased when the divided injection pulse period IT1_SP (1) is not within the total injection period IT1, so that the required fuel amount can be injected by one injection within the total injection period IT1. Implement fuel pressure control to increase the amount of fuel per hit.
In step S115, the required fuel amount is injected by one injection within the total injection period IT1 under the fuel pressure controlled in step S114.

Although the contents of the present invention have been specifically described with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.
In the present embodiment, an in-cylinder direct injection type engine in which the injector 6 as the fuel injection device directly injects fuel into the combustion chamber is exemplified. However, for example, in the intake stroke, the fuel is directed into the combustion chamber through the opening of the intake valve. In a port injection type engine equipped with a fuel injection device (injector) for injecting fuel in the intake port (intake passage), the intake stroke split injection is performed, and the first injection is performed in the same manner as in the above embodiment. The total injection period from the start to the completion of the final injection can be shortened as the engine temperature increases, and the total injection period can be shortened to increase the final injection completion time. In this case, similar effects can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Engine control unit (ECU), 2 ... Accelerator opening sensor, 3 ... Air flow sensor, 4 ... Intake temperature sensor, 5 ... Throttle, 6 ... Injector, 7 ... Fuel pump, 8 ... Common rail, 9 ... Intake pipe, 10 ... Variable intake / exhaust valve, 11 ... piston, 12 ... crankshaft, 13 ... crank angle sensor, 14 ... combustion chamber, 15 ... cooling water temperature sensor, 16 ... ignition plug, 17 ... exhaust pipe, 18 ... three-way catalyst

Claims

The total injection period from the start of the first injection to the completion of the final injection in the intake stroke split injection in which the fuel injection by the fuel injection device is divided into a plurality of times in the intake stroke is shortened according to the increase in engine temperature. Engine control device.
The engine control device according to claim 1, wherein the final injection completion timing is advanced with respect to an increase in engine temperature.
The engine control device according to claim 2, wherein the first injection start timing and the plurality of injection times are changed according to an engine load and an engine speed.
2. The engine control device according to claim 1, wherein the number of injections is reduced when an injection suspension period in the middle of the intake stroke divided injection is less than a set period.
The engine control device according to claim 4, wherein when the number of injections is reduced to one, the fuel pressure is changed so that fuel injection is completed within the total injection period.
The engine control device according to claim 1, wherein the start of the intake stroke divided injection is delayed with respect to an increase in fluctuations in engine rotation speed during warm-up operation.
The engine control device according to claim 1, wherein the fuel injection device is a device that directly injects fuel into a combustion chamber of the engine.
In an engine equipped with a fuel injection device that directly injects fuel into a combustion chamber,
Detect engine temperature
In the intake stroke, the total injection period from the start of the first injection to the completion of the final injection when performing fuel injection divided into a plurality of times is shortened as the engine temperature increases,
An engine control method in which fuel injection by the fuel injection device is performed in a plurality of times during the total injection period of an intake stroke.