JP5703341B2 - In-cylinder injection internal combustion engine control device - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle or the like, and more particularly to a control device for a direct injection internal combustion engine.

  Current vehicles (automobiles) reduce exhaust gas substances such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) contained in automobile exhaust gas from the viewpoint of environmental conservation, and fuel consumption There is a need to reduce the amount. In order to reduce these, in-cylinder injection engines have been developed.

  An in-cylinder injection type engine performs fuel injection by a fuel injection valve directly into a combustion chamber of a cylinder to reduce exhaust gas substances, reduce fuel consumption, improve engine output, and the like.

  However, in a cylinder injection engine, fuel spray that moves in the combustion chamber by injection tends to adhere to the crown surface of the piston and the wall surface of the cylinder bore. The amount of adhesion depends on the timing at which the fuel injection valve performs fuel injection.

  When the fuel injection valve performs the fuel injection timing as the intake stroke, if the fuel injection timing is relatively advanced, a period during which the fuel vaporizes from the fuel injection to the ignition is secured, and the combustibility can be improved. On the other hand, since fuel injection occurs when the piston crown surface is closer to the injector, fuel adhesion to the crown surface of the piston increases. In particular, the fuel adhering to the piston crown surface is gradually atomized at the time of subsequent engine combustion, incompletely combusted, and discharged from the cylinder (Patent Document 1).

  Also, if there is a large amount of fuel remaining on the crown surface of the piston or the cylinder bore and remaining in the combustion chamber, graphite is generated, and the number of discharged particles of particulate matter, so-called particulate matter (hereinafter referred to as PM) tends to increase. There is. Here, the number of PM discharged particles is the total number of PM particles discharged when the vehicle is driven in a predetermined driving pattern. In particular, when the amount of fuel adhering to the crown surface of the piston is large, the number of PM exhaust particles tends to increase. In recent years, there has been an increasing need for reducing the number of PM emission particles for vehicle engines, particularly in-cylinder injection engines.

JP 2007-32326 A

  In a cylinder injection engine, when the fuel injection timing is the intake stroke, if the fuel injection timing is relatively advanced, the amount of fuel adhering to the crown surface of the piston increases, and the number of PM exhaust particles tends to increase. It becomes. On the other hand, if the injection timing is retarded to reduce the amount of fuel adhering to and remaining on the piston crown so as to suppress the increase in the number of PM exhaust particles, the amount of fuel adhering to and remaining on the cylinder bore wall surface increases. The unburned gas tends to increase.

  This problem is the same in the case of split multi-stage injection in which fuel injection is performed a plurality of times in one cycle. In split multi-stage injection, an interval between injection and injection is required. Compared with the case where fuel is injected only once, the end timing of the injection is retarded. If the end timing of the final divided injection is retarded from the predetermined crank angle, it may not be sufficiently vaporized until ignition, and the homogeneity of the mixture in the cylinder tends to decrease. Become.

  An object of the present invention is to increase the number of PM exhaust particles while advancing the first injection as much as possible when performing multiple fuel injections in one cycle in a cylinder injection engine. An object of the present invention is to provide a control device for an in-cylinder injection engine that reduces the amount of fuel adhering to and remaining on the piston crown so as to suppress it.

  In order to achieve this object, the present invention provides a control device for an internal combustion engine including a fuel injection valve that injects fuel into a combustion chamber by controlling a drive current based on an injection pulse width, and at least the first injection is taken into the intake air. When the multi-stage injection control is performed to perform multiple fuel injections during the stroke and the injection pulse width of the initial injection is short, the injection timing of the initial injection is longer than when the injection pulse width of the initial injection is long. There is provided a control device characterized by setting an injection timing of an initial injection based on an injection pulse width of the initial injection so as to advance.

  According to the present invention, it is possible to execute divided multi-stage injection at an injection timing that can reduce the amount of fuel adhering to and remaining on the piston crown, and to suppress an increase in the number of PM exhaust particles.

  In particular, when the internal combustion engine is cold-started, the temperature of the piston crown surface is lower than that during warm-up, so that a greater effect can be obtained.

1 is a schematic configuration diagram of an overall control system for a direct injection engine according to an embodiment of the present invention. 1 is an overall schematic diagram of a fuel system of a direct injection engine according to an embodiment of the present invention. It is a block diagram which shows the input / output signal relationship of the engine control unit used with the system configuration | structure which shows one Embodiment of the control apparatus of the direct injection type engine by one Embodiment of this invention. It is a figure which shows the relationship of the elapsed time after the energization start of the injector by the fuel system of the direct injection type engine by one Embodiment of this invention, and the arrival distance (penetration) of the injected fuel. It is a figure which shows the relationship between the injection pulse width of an injector, and the maximum value of the penetration of the injected fuel by the fuel system of the direct injection type engine by one Embodiment of this invention. When an injector is used in which the fuel to be injected is injected in one direction, while the piston moves from top dead center to bottom dead center, fuel is injected from the injector into the combustion chamber. It is a figure which shows the relationship of the shortest distance. Injector injection when using a multi-hole injector that injects fuel in multiple directions and injecting fuel from the injector into the combustion chamber while the piston moves from top dead center to bottom dead center It is a figure which shows the relationship of the shortest distance from a mouth. It is a flowchart which shows the control content of the division | segmentation multistage injection control of the direct injection type engine by one Embodiment of this invention. It is a flowchart which shows the processing content of the division | segmentation injection setting shown in FIG. It is a figure which shows the map function for calculating the penetration (maximum value of fuel reach distance) of each injection shown in FIG. It is a flowchart which shows the processing content of the injection timing setting shown in FIG. It is a figure which shows the map function for calculating the temperature allowable injection angle PCAt shown in FIG. It is a time chart which shows the 1st control example of the division | segmentation multistage injection control of the cylinder injection type engine by one Embodiment of this invention. It is a time chart which shows the 2nd control example of the division | segmentation multistage injection control of the cylinder injection type engine by one Embodiment of this invention. It is a time chart which shows the 3rd control example of the division | segmentation multistage injection control of the cylinder injection type engine by one Embodiment of this invention. It is a time chart which shows the 4th control example of the division | segmentation multistage injection control of the direct injection type engine by one Embodiment of this invention. It is a time chart which shows the 5th control example of the division | segmentation multistage injection control of the cylinder injection type engine by one Embodiment of this invention. It is a flowchart which shows another processing content of the division | segmentation injection setting shown in FIG. It is a flowchart which shows the processing content of the process at the time of non-dividing shown in FIG. It is a flowchart which shows the processing content of the 1st injection process shown in FIG. It is a flowchart which shows the processing content of the division | segmentation injection process shown in FIG. It is a flowchart which shows the processing content of the last injection process shown in FIG. It is a time chart which shows the 6th control example of the division | segmentation multistage injection control of the cylinder injection type engine by one Embodiment of this invention. It is a time chart which shows the 7th control example of the division | segmentation multistage injection control of the cylinder injection type engine by one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

  First, the overall configuration of the control system for the direct injection engine 1 according to one embodiment of the present invention will be described with reference to FIG.

  The in-cylinder injection engine 1 has four cylinders. FIG. 1 shows only one cylinder for simplification. Each cylinder has a cylinder 207b, and the air introduced into the cylinder 207b is taken from the inlet of the air cleaner 202, passes through an air flow meter (air flow sensor 203), and accommodates an electric throttle valve 205a that controls the intake flow rate. Enters the collector 206 through the throttle body 205. The air drawn into the collector 206 is distributed to the intake pipes 201 connected to the cylinders 207b of the direct injection engine 1, and then guided to the combustion chamber 207c formed by the piston 207a, the cylinder 207b, and the like. In addition, a signal representing the intake flow rate is output from the airflow sensor 203 to the engine control unit 101 having the high-pressure fuel pump control device of the present embodiment. Further, a throttle sensor 204 for detecting the opening degree of the electric throttle valve 205 a is attached to the throttle body 205, and its signal is also output to the engine control unit 101.

  On the other hand, 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 moreover by the high-pressure fuel pump 209 described later. Secondary pressure is applied to a high pressure (for example, 5 MPa or 10 MPa), and the fuel is injected into the combustion chamber 207 c from a fuel injection valve (hereinafter referred to as an injector 254) provided in the cylinder 207 b via the fuel rail 253. The fuel injected into the combustion chamber 207 c is ignited by the spark plug 208 by the ignition signal that has been increased in voltage by the ignition coil 222. In the present embodiment, the injector 254 is a side injection method in which injection is performed from the cylinder 207b side of the in-cylinder injection engine 1, but a center injection method in which injection is performed directly above the combustion chamber 207c may be employed.

  A crank angle sensor 216 attached to the crankshaft 207d of the direct injection engine 1 outputs a signal indicating the rotational position of the crankshaft 207d to the engine control unit 101, and makes the opening / closing timing of the intake valve 225 variable. And a cam angle sensor 211 attached to a camshaft (not shown) having a mechanism for changing the opening / closing timing of the exhaust valve 226 and having a mechanism for changing the opening / closing timing of the exhaust valve 226. An angle signal representing the position is output to the engine control unit 101, and an angle signal representing the rotational position of the pump drive cam 200 of the high-pressure fuel pump 209 that rotates with the rotation of the cam shaft of the exhaust valve 226 is also output to the engine control unit 101. Output to.

  In the present embodiment, the in-cylinder injection engine 1 is described as having four cylinders, but it may be an engine having another number of cylinders such as three or six cylinders.

  In this embodiment, both the intake valve 225 and the exhaust valve 226 are provided with a variable opening / closing timing mechanism. However, the variable valve mechanism may be configured such that only the opening / closing timing of the intake valve 225 is variable. In addition, a mechanism that makes the valve lift variable can be used.

  FIG. 2 is a schematic diagram showing the overall configuration of a fuel system provided with the high-pressure fuel pump 209.

  The high pressure fuel pump 209 pressurizes the fuel from the fuel tank 250 and pumps the high pressure fuel to the fuel rail 253.

  The fuel is led from the tank 250 to the fuel inlet of the high-pressure fuel pump 209 by the low-pressure fuel pump 251 after being regulated to a constant pressure by the fuel pressure regulator 252. A pump solenoid 209a, which is an electromagnetic control valve for controlling the fuel intake amount, is provided on the fuel inlet side. The pump solenoid 209a is a normally closed solenoid that closes when not energized and opens when energized. The fuel supplied by the low-pressure fuel pump 251 is adjusted in suction amount by controlling the pump solenoid 209a by the engine control unit 101, pressurized by the pump drive cam 200 and the pressurizing chamber 209b, and supplied from the fuel discharge port. The fuel rail 53 is pumped. A discharge 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 fuel rail 253 is provided with a pressure sensor 256 for measuring the fuel pressure (hereinafter referred to as fuel pressure) in the injector 254 and the fuel 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. The key switch 401 signal indicating an accessory, ignition ON, starter ON, accelerator opening sensor 402, brake switch 403, vehicle speed. Signals from various sensors including the sensor 404, the airflow sensor 203, the throttle sensor 204, the cam angle sensor 211, the crank angle sensor 216, the water temperature sensor 217, the air-fuel ratio sensor 218, the pressure sensor 256, and the oil temperature sensor 219 are input as inputs. , Execute predetermined calculation processing, output various control signals calculated as calculation results, and apply predetermined control signals to the electric throttle valve 205a, pump solenoid 209a, ignition coil 222, low-pressure fuel pump 251, and injector 254, which are actuators. It supplies a control signal, the fuel pressure control in the fuel rail 253, and executes the fuel injection amount control and the ignition timing control and the like. The I / O LSI 101a is provided with a drive circuit for driving the injector 254. The voltage supplied from the battery is boosted and supplied using a booster circuit (not shown), and the current is controlled by the IC (not shown). Thus, the injector 254 is driven.

  Next, the penetration (penetration force) of the fuel injected from the injector 254, that is, the fuel reach distance 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 reach distance (penetration) of the injected fuel when fuel is injected from the injector 254 with a predetermined fuel pressure and a predetermined injection pulse width. Is shown. Immediately after the start of energization, there is a delay in opening the injector 254, so the penetration is zero, 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 the penetration is PNT_max.

FIG. 5 shows the maximum value of the penetration for each injection pulse width when the fuel is injected from the injector 254 at a predetermined fuel pressure under an environment of a predetermined back pressure, that is, PNT_m in FIG.
The penetration relationship corresponding to ax is shown. 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 pulse width, and the penetration at Ti_min is the smallest.

  FIG. 6 shows a case where fuel is injected from the injector 254 into the combustion chamber 207c while the piston 207a moves from top dead center (TDC) to bottom dead center (BDC). The relationship of the shortest distance to a surface or a cylinder bore is shown. In FIG. 6, for the sake of simplicity, the case where the fuel injected from the injector 254 is injected in one direction is described 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 injector 254, the shortest distance is short, and the piston 207a moves from TDC to BDC as the crank angle advances. The shortest distance will gradually increase. When the crank angle is CA_0 or later, the piston 207a moves further away from the injection port of the injector 254, but the cylinder bore wall surface is closer to the injection port of the injector 254, so the shortest distance is constant.

  Here, for example, when the penetration of the fuel injected from the injector 254 (the maximum value of the fuel arrival distance) is large, the fuel reaches the piston crown when it is injected on the advance side (TDC side) with respect to the crank angle CA_0. When the fuel is injected on the retard side (BDC side) with respect to the crank angle CA_0, the fuel reaches the cylinder bore wall surface. However, when the penetration of the fuel injected from the injector 254 (maximum value of the fuel reach distance) is p1, if the injection is started after the crank angle CA_p1, the fuel will not reach the piston crown surface or the bore wall surface. . For example, when the penetration of the fuel injected from the injector 254 is p2, if the injection is started after the crank angle CA_p2, the fuel will not reach the piston crown surface or the bore wall surface. For example, when the injection is performed at the minimum injection pulse width, the penetration is p1, and when the injection is performed at the injection pulse width per time divided by a predetermined division ratio, the injection is performed after the crank angle CA_p1. It is only necessary to start, and if the penetration is p2 when the injection is performed with the injection pulse width per time divided by the predetermined division ratio, the injection may be started after the crank angle CA_p2.

  FIG. 7 shows a so-called multi-hole injector in which fuel injected from the injector 254 is injected in a plurality of directions, and combustion occurs while the piston 207a moves from top dead center (TDC) to bottom dead center (BDC). The relationship of the shortest distance from the injection port of the injector 254 when the fuel is injected from the injector 254 into the chamber 207c is shown. FIG. 7 shows a case where six beams are injected as an example of the multi-hole injector.

  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 injector 254, the shortest distance is short for any beam, and the piston 207a increases as the crank angle advances. Moves from TDC to BDC, so the shortest distance of each beam gradually increases. Here, in the multi-hole, since the fuel is injected in a plurality of directions, the shortest distance differs depending on the beam. For example, the beam No1 is injected in the most upward direction, that is, in the direction close to the plane parallel to the crown surface. As the travel proceeds, the increase in the shortest distance increases, and conversely, the beams No. 5 and 6 are injected in the most downward direction, that is, in the direction close to the vertical plane with respect to the crown surface. The width is smaller. When the crank angle becomes equal to or greater than a predetermined value for each beam, the piston 207a moves further away from the injection port of the injector 254. However, since the cylinder bore wall surface is closer to the injection port of the injector 254, the shortest distance is constant.

  Here, as in FIG. 6, for example, when the penetration of fuel injected from the injector 254 (maximum value of the fuel reach distance) is p1, if the injection is started after the crank angle CA_p1, the fuel of any beam is changed to the piston. Neither the crown surface nor the bore wall surface will be reached. Further, for example, when the penetration of the fuel injected from the injector 254 is p2, if the injection is started after the crank angle CA_p2, neither beam fuel reaches the piston crown surface or the bore wall surface. In the following embodiment, the case where the injector 254 is a multi-hole injector will be described as an example.

  6 and 7 show geometric distances. In actual combustion, the influence of the intake air flow in the combustion chamber 207c is affected, but the fuel to be injected in one cycle is divided into a plurality of times. The fuel injection is performed, and the crank angle to be injected is selected according to the penetration (maximum value of the fuel arrival distance) of each divided injection pulse width, or the penetration is allowed to be long according to the injection crank angle. Thus, by selecting each injection pulse width, the amount of fuel adhering to the piston crown surface and the bore wall surface can be greatly reduced.

  Next, specific control contents of the split multi-stage injection control of the internal combustion engine according to the present embodiment will be described with reference to FIGS.

  FIG. 8 is a flowchart showing the control content of the divided multi-stage injection control according to the embodiment of the present invention.

  The contents of FIG. 8 are programmed in the CPU 101b of the engine control unit 101 and repeatedly executed at a predetermined cycle. That is, the processing of the following steps 501 to 506 is repeatedly executed at a predetermined cycle by the engine control unit 101. The engine control unit 101 supplies a predetermined control signal to each injector 254 based on the injection pulse width and the injection timing calculated in the processing content of FIG. 8, and executes a plurality of fuel injections in one cycle.

  In step 801, a total injection pulse width Ti_all, which is the total amount of fuel injected from each injector during one cycle, is set. The total injection pulse width Ti_all is set according to the amount of intake air measured by the airflow sensor 203, the air-fuel ratio set according to the operating state, the fuel pressure calculated using the pressure sensor 256 signal, and the like.

  In step 802, the minimum injection pulse width Ti_min is calculated. As shown in FIG. 8B, the minimum injection pulse width Ti_min is calculated with reference to a function Fmin with the fuel pressure Pf calculated using the pressure sensor 256 signal as an input. Here, since the minimum injection pulse width depends on the electrical characteristics, mechanical characteristics, and drive current waveform of the injector 254, it is desirable to set the function Fmin in consideration of various characteristics.

  In step 803 (divided injection setting), each injection pulse width and injection timing of divided multi-stage injection are set. Details of step 803 are shown in FIG.

  Next, details of step 803 (division injection setting) in FIG. 8 will be described with reference to FIG. FIG. 9 is a control flowchart of a control method in which the number of divided injections in one cycle is first set, and each injection pulse width and each injection timing are set. When the division number is N, each injection pulse width and each injection timing of n = 1 to N are set.

  In step 901, the counter is initialized.

  In step 902, the division number N is set. Using the total injection pulse width Ti_all and the minimum injection pulse width Ti_min set in steps 801 and 802 in FIG. 8, division of Ti_all ÷ Ti_min is executed, and the quotient is set as the division number N. For example, when Ti_all is 1.0 ms and Ti_min is 0.3 ms, Ti_all ÷ Ti_min = 3.33... And the quotient is 3, so N = 3.

  In step 903, it is determined whether or not the counter n is larger than the division number N. If it is larger (when setting from n = 1 to N is completed), the process is terminated. When the counter n is equal to or less than the division number N, the processing from step 904 is performed.

  In step 904, the injection pulse width Ti_n (n = 1 to N) of each injection is calculated. In step 904, the injection pulse width Ti_n is calculated as Ti_all ÷ N. In detail, for example, when Ti_all is 1.0 ms and the division number N = 3, Ti_1 = 0.33, It is desirable to perform a carry-off hat process such as Ti_2 = 0.33, Ti_3 = 0.34. Alternatively, the division ratio may be set, and the calculation may be performed by incorporating the digit loss prevention into the division ratio calculation in advance.

  In step 905, the penetration is estimated. Based on each divided injection pulse width Ti_n and the fuel pressure Pf, the penetration (maximum value of fuel reach distance) pnt_n of each divided injection is calculated using a map structure as shown in FIG. In FIG. 10, a map structure of each injection pulse width Ti_n and fuel pressure Pf is used. However, a four-dimensional map structure of each injection pulse width Ti_n, fuel pressure Pf, and air temperature by detecting or estimating the intake air temperature, It is desirable to do. Further, when a turbocharging system such as a turbocharger or a supercharger is mounted on the in-cylinder injection engine 1, the intake pipe pressure, the supercharging pressure, or the like is used in order to take into account changes in penetration due to pressure changes in the combustion chamber. It is desirable to correct the estimated penetration. Furthermore, since the penetration changes depending on the fuel properties such as heavy and light, multiple maps are prepared according to the fuel properties, heavy and light are determined, and the map is searched based on the determination results. It is desirable to switch or complement values.

  In step 906, an injection interval CAINTn which is an injection interval of each divided injection is calculated. It is desirable to set the injection interval as the maximum value of a plurality of conditions. One is a condition regarding penetration. If the interval between the divided injection pulse widths Ti_n is shortened, the penetration increases. Therefore, the injection interval by the penetration is calculated by a function using the fuel pressure Pf as an input. The second condition is related to a drive circuit provided in the engine control unit 101 for driving each injector 254. When the injector 254 is driven, the voltage boosted by the booster circuit provided in the engine control unit 101 decreases, and it takes time to return to the original level again. This is a so-called boosting recovery time. When the boosting recovery time is Tbst, in order to inject the next injection Ti_ (n + 1), it is necessary to wait for a predetermined time after the end of the current injection Ti_n. That is, the injection interval needs to be Tbst-Ti_n or more. Therefore, the maximum value of the injection interval due to the penetration and the injection interval due to the boost recovery time is set as the required injection interval TINTn, and the injection interval CAINTn is calculated by converting the required injection interval TINTn to the crank angle using the engine speed Ne ( Interval [ms] × engine speed [r / min] × 6 ÷ 1000 = crank angle [° CA]). If an injection interval is necessary to improve the homogeneity of the air-fuel mixture, the crank angle may be converted by adding the third condition and selecting the maximum value. Since the homogeneity of the air-fuel mixture greatly depends on the intake flow, the injection interval related to the homogeneity may be calculated using the engine speed Ne and the opening / closing timing of the intake valve 225 and the exhaust valve 226.

  In step 907 (injection timing setting), the injection timing of each injection of the divided multi-stage injection is set. Details of step 907 are shown in FIG.

  In step 908, the counter n is incremented, and the process returns to step 903. In this way, the process is repeated from n = 1 to N, and each injection pulse width and each injection timing are set.

  Next, details of step 907 (injection timing setting) in FIG. 9 will be described with reference to FIG.

  In step 1101, the most advanced injection timing (crank angle) allowable in the case of the penetration estimated in step 905 in FIG. 9 is calculated. The temperature allowable injection angle PCAt is calculated by referring to a map Mcat as shown in FIG. 12A with the estimated penetration pnt_n of the n-th injection and the piston crown surface temperature Tp as inputs. The map Mcat is set based on the arrangement of the injector 254 (arrangement with respect to the combustion chamber 207c), the direction of each beam injected from the injector 254, the bore of the combustion chamber 207c, and the stroke. It is more preferable to set the crown surface shape of the piston 207a taking into consideration. Further, the map Mcat is set such that when the piston crown surface temperature Tp is low, the vaporization of the fuel adhering to the piston crown surface is deteriorated. Therefore, as shown by the broken line in FIG. When the piston crown surface temperature Tp is set to the retarded angle side, vaporization of fuel adhering to the crown surface is promoted, so that the allowable injection angle for a predetermined penetration increases as shown by the solid line in FIG. Set to the corner side. On the other hand, when the piston crown surface temperature Tp becomes even higher, if fuel adheres to the crown surface, a layer of evaporated fuel (gas) is generated under the fuel (liquid) and the heat is impeded so that the liquid instantaneously Therefore, the so-called Leidenfrost phenomenon is prevented, so that it is desirable to set the allowable injection angle for a predetermined penetration to the retarded angle side as shown by the one-dot broken line in FIG.

  The crown surface temperature Tp estimates the combustion temperature using the air amount, air-fuel ratio, ignition timing, etc., and further forms a thermal model using the water temperature and oil temperature detected by the water temperature sensor 217 and oil temperature sensor 219. However, from the viewpoint of simplification of control, a lower value of the water temperature and the oil temperature detected by the water temperature sensor 217 and the oil temperature sensor 219 is used as an input value (substitute for the crown surface temperature Tp). It is good also as a structure which searches Mcat. Alternatively, the map Mcat may be searched using the water temperature detected by the water temperature sensor 217 as an input value.

  Further, the map Mcat is configured with the estimated penetration pnt_n and the piston crown surface temperature Tp as inputs, but is configured as a four-dimensional map with the estimated penetration pnt_n, the piston crown surface temperature Tp, and the cylinder bore wall surface temperature as inputs. May be. It is desirable to estimate the cylinder bore wall surface temperature by estimating the combustion temperature using the air amount, air-fuel ratio, ignition timing, etc., and further by constructing a thermal model using the water temperature detected by the water temperature sensor 217. From this point of view, the estimated penetration pnt_n, the oil temperature, and the water temperature may be input as a four-dimensional map.

  In step 1102, a time delay until the injected fuel arrives is corrected. As shown in FIG. 4, since there is a valve opening delay of the injector 254 immediately after the start of energization, the penetration is 0, and the penetration gradually increases after a predetermined time has elapsed. Since the change in penetration with respect to the speed of fuel spray, that is, the elapsed time after the start of injection, depends on the fuel pressure, for example, a time delay is set by a table function using the fuel pressure Pf as an input, and the time delay is determined using the engine speed Ne The time correction value PCAc is calculated by converting the crank angle (time [ms] × engine speed [r / min] × 6 ÷ 1000 = crank angle [° CA]).

  In step 1103, the time correction value PCAc is subtracted from the temperature allowable injection angle PCAt to calculate the allowable injection angle PCA. While considering the arrival time delay in step 1103, the most advanced injection timing (crank angle) allowable in the case of the penetration estimated in step 905 of FIG. 9 can be calculated.

  In step 1104, it is determined whether or not the first injection timing is set in the divided injection in one cycle. If n = 1, the process proceeds to step 1107, and ends with the first injection start timing SOI1 = allowable injection angle PCA. When n ≠ 1 (after the second time), the process proceeds to step 1105, and the nth injection start possible angle PCAn is calculated. The injection interval CAINTn calculated in step 906 in FIG. 9 is added to the previous (n−1) th injection end timing EOI (n−1) to calculate the nth injection start possible angle PCAn. The previous (n-1) th injection end timing EOI (n-1) is the same as the previous (n-1th) injection start timing SOI (n-1), and the previous (n-1th) injection pulse width Ti_. Calculation is performed by adding the crank angle conversion value of (n-1). Next, step 1106 is executed to calculate the present (n-th) injection start timing SOIn. The nth injection start timing SOIn is a large value of the allowable injection angle PCA calculated in step 1103 and the nth injection start possible angle PCAn calculated in step 1105, that is, a value on the advance side. Accordingly, it is possible to set an injection timing that is allowable in the case of the penetration of each injection estimated in step 905 of FIG. 9 while ensuring the injection interval of the divided injection.

  Next, a specific control example of the split multi-stage injection control of the internal combustion engine when configured as shown in FIGS. 8 to 12 will be described using FIGS. 13 to 16.

  FIG. 13 is a time chart when the piston crown surface temperature Tp is an appropriate temperature, for example, when engine warm-up is completed and normal operation is performed, and when five divided injections are executed in one cycle.

  13A is a crank angle, FIG. 13B is a drive pulse of the injector 254, FIG. 13C is a drive current of the injector 254, and FIG. 13D is a current from the injection port of the injector 254. The relationship of the shortest distance of each beam is shown. The crank angle in FIG. 13 (A) increases from 0 to 180, and the shortest distance of each beam in FIG. 13 (D) gradually increases. In step 1101 of FIG. 11, when the piston crown surface temperature is an appropriate temperature, the drive pulse of the injector 254 is generated five times at a timing that allows the penetration of each divided injection, and five divided injections are performed in the middle of the intake stroke. Is running.

  FIG. 14 is a time chart when the piston crown surface temperature Tp is an appropriate temperature, for example, when the engine warm-up is completed and the engine is operating normally, and when four divided injections are executed in one cycle. (A), (B), (C), and (D) in FIG. 14 are the same as (A), (B), (C), and (D) in FIG. Compared to the case of FIG. 13, the drive pulse (injection pulse width Ti_n) of the injector 254 is longer (the penetration is longer), and therefore the injection start timing SOIn is slightly later than that of FIG. 13 by the processing shown in FIG. 11. It is set on the corner side (BDC side) and four divided injections are executed.

  Here, for example, when the engine load is increased in a state where the piston crown surface temperature Tp is an appropriate temperature, for example, the engine warm-up is completed and the engine is operating normally, the total injection pulse width Ti_all calculated in step 801 of FIG. Will also increase. When the fuel pressure Pf remains constant, the minimum injection pulse width Ti_min calculated in step 802 in FIG. 8 is constant. Therefore, when the engine load is increased from low load to medium load or high load, for example, when the division number N calculated in step 902 of FIG. 9 is 4 at low load, as the engine load increases. When the injection pulse width Ti_n (n = 1 to 4) of each injection calculated in step 904 in FIG. 9 gradually increases and the load increase amount becomes equal to or greater than a predetermined value, the number of divisions N calculated in step 902 in FIG. Increases by 1 to 5. When the engine load further increases, the injection pulse width Ti_n (n = 1 to 5) of each injection calculated in step 904 in FIG. 9 gradually increases. As a result, the estimated penetration pnt_n calculated in step 905 in FIG. 9 gradually increases as the engine load gradually increases from a low load, decreases once when the number of divisions increases by 1, and further increases the engine load. As it gradually increases, it gradually increases. Each injection start timing SOIn finally set in FIG. 11 is the injection timing shown in FIG. 14 at low load, and gradually the injection timing in FIG. 14 as the engine load gradually increases from low load. When the number of divisions increases by one, the injection timing shown in FIG. 15 is obtained, and as the engine load gradually increases, the injection timing of FIG. 15 becomes more retarded. go.

  FIG. 15 shows a case where the piston crown surface temperature Tp is low, for example, when the engine is started at a low temperature, the warm-up is not completed, and the oil temperature and the water temperature are not yet sufficiently increased. It is a time chart at the time of performing divided injection. (A), (B), (C), and (D) in FIG. 15 are the same as (A), (B), (C), and (D) in FIG. Since the piston crown surface temperature is lower than in the case of FIG. 13, the injection start timing is set so that the penetration of each divided injection can be permitted by the process shown in FIG. 11 when the piston crown surface temperature is low. After the SOIn is set slightly on the retard side (BDC side) than FIG. 13, the divided injection is executed five times.

  FIG. 16 is a time chart in the case where the piston crown surface temperature Tp is continuously operated at a high temperature, for example, a high load, and five divided injections are executed in one cycle. (A), (B), (C), and (D) in FIG. 16 are the same as (A), (B), (C), and (D) in FIG. Since the piston crown surface temperature is higher than in the case of FIG. 13, the injection start timing SOIn is set so that the penetration of each divided injection when the piston crown surface temperature is high by the processing shown in FIG. Is set to a slightly retarded angle side (BDC side) than FIG. 13, and five divided injections are executed.

  By configuring as shown in FIGS. 8 to 12, the piston crown surface temperature is maintained while maintaining the injection interval for preventing the increase in penetration in various operation states as shown in FIGS. 13 to 16. In consideration of this, the multi-stage injection control is performed by setting the injection timing according to the penetration of each divided injection, so that the in-cylinder fuel adhesion can be reduced, the number of PM exhaust particles increased, and the unburned An increase in fuel can be suppressed.

  In addition, when performing an intermittent operation control in which the in-cylinder injection engine 1 automatically stops temporarily while a predetermined condition is satisfied, so-called idle stop, combustion does not occur during idle stop, so the wall surface temperature in the combustion chamber decreases. However, in the setting of the injection timing shown in FIG. 11, in order to calculate the temperature allowable injection angle PCAt in step 1101, by applying this control to an in-cylinder injection engine having an idle stop function, In the operation after the in-cylinder injection engine 1 is restarted from the idle stop, the injection timing is set in accordance with the penetration of each divided injection in consideration of the crown surface temperature and the divided multi-stage injection control is executed. In-cylinder fuel adhesion can be reduced, and the increase in the number of PM emission particles and the increase in unburned fuel can be suppressed. That.

  FIG. 17 shows a so-called catalyst warm-up control in which a weak stratified mixture is formed by the intake stroke injection and the compression stroke injection after the cold start, and the ignition timing is retarded. FIG. 13 is a time chart when the divided multi-stage injection control shown in FIGS. 8 to 12 is applied. FIG. (A), (B), (C), and (D) in FIG. 17 are the same as (A), (B), (C), and (D) in FIG. FIG. 17 shows from the intake stroke to the compression stroke, and the crank angle in FIG. 17 (A) increases from 0 to 360. Therefore, the shortest distance of each beam in FIG. 13D is gradually increased and gradually decreased. In the period in which the crank angle in FIG. 17A is from 0 to 180, that is, the intake stroke, three divided injections are executed. Further, one injection is performed in a period where the crank angle in FIG. 17A is 180 to 360, that is, in the compression stroke. By configuring in this way, while forming a combustible mixture around the spark plug, in the intake stroke injection, in order to execute divided multistage injection by setting the injection timing according to the penetration of each divided injection, In-cylinder fuel adhesion can be reduced, and an increase in the number of PM exhaust particles and an increase in unburned fuel can be suppressed.

  Next, details of the case where Step 803 (divided injection setting) in FIG. 8 is configured using a method different from the control method shown in FIGS. 9 to 12 will be described with reference to FIGS. 18 to 24.

  FIG. 18 is a control flowchart of a control method in which the number of divided injections in one cycle is not initially set, but a pulse width that allows penetration is calculated and N divided injections are performed. When the division number is N, each injection pulse width and each injection timing of n = 1 to N are set.

  In step 1801, the counter is initialized.

  In step 1802, it is determined whether or not the divided injection can be executed using the total injection pulse width Ti_all and the minimum injection pulse width Ti_min set in steps 801 and 802 in FIG. If Ti_all <Ti_min × 2, step 1805 (non-division processing) is executed. Details of step 1805 are shown in FIG.

  In step 1803, it is determined whether or not the injection pulse width of the first injection and the injection timing are set in the divided injection in one cycle. When n = 1, the process proceeds to Step 1806 (first injection process), and after executing Step 1806, the process proceeds to Step 1807. If n ≠ 1 (the second and subsequent times), the process proceeds to step 1807. Details of step 1806 are shown in FIG.

  In step 1807, it is determined whether or not the remaining injection time obtained by subtracting the divided injection pulse widths from the total injection pulse width Ti_all can be further divided. If Ti_min × 2> Ti_all−ΣTi_x (x = 1 to n), step 1808 (final injection process) is executed. Details of step 1808 are shown in FIG. If Ti_min × 2 ≦ Ti_all−ΣTi_x (x = 1 to n), step 1807 (divided injection processing) is executed, and the process returns to step 1804 again. Details of step 1807 are shown in FIG.

  Next, details of step 1805 (non-division processing) in FIG. 18 will be described with reference to FIG.

  In step 1901, the injection pulse width Ti_n is set. In the process of FIG. 19, since there is no division, that is, the number of divisions N = 1, n-th injection pulse width Ti_n = total injection pulse width Ti_all.

  In step 1902, the same processing as in step 905 in FIG. 9 is performed to calculate penetration (maximum value of fuel reach distance) pnt_n.

  In step 1903, the processing from step 1101 to step 1103 in FIG. 11 is performed to calculate the allowable injection angle PCA.

  In step 1904, the injection start timing SOI1 ends with the allowable injection angle PCA.

  Next, details of step 1806 (first injection process) in FIG. 18 will be described with reference to FIG.

  In step 2001, n = 1 is set for the first injection pulse width Ti_n. n = first injection pulse width Ti_n = minimum injection pulse width Ti_min.

  In step 2002, the same processing as in step 905 of FIG. 9 is performed to calculate penetration (maximum value of fuel reach distance) pnt_n.

  In step 2003, the processing from step 1101 to step 1103 in FIG. 11 is performed to calculate the allowable injection angle PCA.

  In step 2004, the process is terminated as n = 1st injection start timing SOI1 = allowable injection angle PCA.

  In this embodiment, the first injection pulse width is set to the minimum injection pulse width Ti_min. However, instead of steps 1901 to 1902, the allowable penetration of the first injection is set in advance to the piston crown surface temperature. Or the cylinder bore wall surface temperature, or a simplified setting based on the oil temperature or water temperature, and the first injection pulse width is set based on the allowable penetration of the first injection and the fuel pressure by the same processing as step 2105 in FIG. It is good also as a structure to calculate.

  Next, details of step 1807 (divided injection processing) in FIG. 18 will be described with reference to FIG.

  In step 2101, the counter n is incremented.

  In Step 2102, an injection interval CAINT (n-1) that is an injection interval between the (n-1) th injection and the nth injection is calculated. The processing in step 2102 is the same as the processing in step 906 in FIG.

  In Step 2103, the nth injection start possible angle PCAn is calculated. The injection interval CAINT (n−1) calculated in step 2102 is added to the previous (n−1) th injection end timing EOI (n−1) to calculate the nth injection start possible angle PCAn.

  In step 2104, the allowable penetration PPNTn, which is a penetration that can be allowed as the n-th injection, is obtained by referring to the map Mcat2 with the nth injection start possible angle PCAn calculated in step 2103 and the piston crown surface temperature Tp as inputs. calculate. The map Mcat2 is set as a reverse map of the map Mcat used in step 1101 of FIG. 11 shown in FIG.

  In step 2105, the allowable penetration PPNTn set in step 2104 and the fuel pressure Pf are input, and the injection pulse width Ti_n of the n-th injection is calculated by referring to the map Mpnt2. The map Mpnt2 is set as an inverse map of the map Mpnt used in step 905 of FIG. 9 shown in FIG.

  In step 2106, the nth injection start possible angle PCAn calculated in step 2103 is ended as the nth injection start timing SOIn.

  Next, details of step 1808 (final injection process) in FIG. 18 will be described with reference to FIG.

  In step 2201, the counter n is incremented.

  In step 2202, an injection pulse width Ti_n corresponding to the final n = N-th injection is set. Ti_n is a value obtained by subtracting the total of the first to (n-1) th injection pulse widths from the total injection pulse width Ti_all.

  In step 2203, the same processing as in step 905 in FIG. 9 is performed to calculate penetration (maximum value of fuel reach distance) pnt_n.

  In step 2204, the processing from step 1101 to step 1103 in FIG. 11 is performed to calculate the allowable injection angle PCA.

  In step 2205, an injection interval CAINT (n-1) that is an injection interval between the (n-1) th injection and the nth injection is calculated. The processing in step 2205 is the same as the processing in step 906 in FIG.

  In step 2206, the nth possible injection start angle PCAn is calculated. The injection interval CAINT (n−1) calculated in step 2205 is added to the previous (n−1) th injection end timing EOI (n−1) to calculate the nth injection start possible angle PCAn.

  In step 2207, the final n = N-th injection start timing SOIn is calculated. The nth injection start timing SOIn is a large value of the allowable injection angle PCA calculated in step 2204 and the nth injection start possible angle PCAn calculated in step 2206, that is, a value on the advance side.

  As described above, by executing the processing shown in FIG. 18 to FIG. 22, it is possible to set each injection timing as advanced as possible while suppressing the increase in the number N of divisions and ensuring the injection interval of the divided injections. In addition, it is possible to perform divided injection by calculating each pulse width that allows penetration at the injection timing.

  Next, details of the case where Step 803 (divided injection setting) in FIG. 8 is configured using the control method shown in FIGS. 18 to 22 will be described with reference to FIGS.

  FIG. 23 is a time chart when the piston crown surface temperature Tp is an appropriate temperature, for example, when engine warm-up is completed and the engine is operating normally, and four divided injections are executed in one cycle. (A), (B), (C), and (D) in FIG. 23 are the same as (A), (B), (C), and (D) in FIG.

  While the crank angle in FIG. 23 (A) is increasing from 0 to 180, the drive pulse of the injector 254 is generated four times, and the divided injection is executed four times at the crank angle of 0 to 180, that is, in the middle of the intake stroke. doing. In the first injection, the injection pulse width is set in step 1806 in FIG. 18, and fuel injection is performed at an injection timing that allows penetration of the injection pulse width. In step 1807 of FIG. 18, after the end of the first injection, the injection interval CAINT (n−1) is cleared and the second injection timing is set, and the second injection pulse based on the allowable penetration at the timing. The width is set. Subsequently, after the end of the second injection, the injection interval CAINT (n−1) is cleared and the third injection timing is set, and the third injection pulse width is set based on the allowable penetration at the timing. The Finally, in step 1808 of FIG. 18, the final, that is, the fourth injection pulse width is set, and fuel injection is performed at an injection timing that allows penetration of the injection pulse width.

  FIG. 24 shows a case where the piston crown surface temperature Tp is low, for example, low temperature, the engine has not been warmed up after starting, and the oil temperature and water temperature have not risen sufficiently. It is a time chart at the time of performing divided injection. (A), (B), (C), and (D) in FIG. 24 are the same as (A), (B), (C), and (D) in FIG. Since the piston crown surface temperature is lower than in the case of FIG. 23, the injection start timing SOIn is set to a slightly retarded angle side (BDC side) than FIG. 23 by the process shown in FIG. The split injection is executed.

  With this configuration, in various operating states, while maintaining the injection interval for preventing an increase in penetration, the injection timing is set in accordance with the penetration of each divided injection in consideration of the piston crown surface temperature. Set and execute split multi-stage injection control, thus suppressing an increase in the number of split injections N and reducing in-cylinder fuel adhesion, suppressing an increase in the number of PM exhaust particles and an increase in unburned fuel can do.

1 In-cylinder injection engine 101 Engine control unit 101a I / O LSI
101b CPU
200 Pump drive cam 201 Intake pipe 202 Air cleaner 203 Airflow sensor 204 Throttle sensor 205 Throttle body 205a Electric throttle valve 206 Collector 207a Piston 207b Cylinder 207c Combustion chamber 207d Crankshaft 208 Spark plug 209 High pressure fuel pump 209a Pump solenoid 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 Fuel rail 254 Injector 256 Pressure sensor 401 Key switch 402 Accelerator opening sensor 403 Brake switch 404 Vehicle speed sensor

Claims (3)

A control device for a direct injection internal combustion engine comprising a fuel injection valve for injecting fuel into a combustion chamber by controlling a drive current based on an injection pulse width,
The internal combustion engine includes a fuel rail that stores fuel to be supplied to the fuel injection valve, and pressure detection means that detects fuel pressure in the fuel rail,
The control device performs divided multi-stage injection control for performing a plurality of times of fuel injection that performs at least the first injection during the intake stroke,
After completion of the previous injection among the injections divided into a plurality of times, an allowable penetration is set at the injection timing during the intake stroke with a predetermined interval time, and a plurality of penetrations are set using the set penetration and the fuel pressure. A control apparatus for an in-cylinder injection internal combustion engine, wherein the injection pulse width of the current injection among the injections divided into times is set individually . A control device for a direct injection internal combustion engine comprising a fuel injection valve for injecting fuel into a combustion chamber by controlling a drive current based on an injection pulse width,
The control device performs divided multi-stage injection control for performing a plurality of times of fuel injection that performs at least the first injection during the intake stroke,
According to the injection crank angle of each injection divided into a plurality of times during the intake stroke, the pulse width of each injection divided into a plurality of times is individually varied so that the penetration is allowed. A control device for an in-cylinder injection internal combustion engine. 3. The control apparatus for a direct injection internal combustion engine according to claim 1, wherein a parameter that affects a crown surface temperature of a piston of the internal combustion engine is a high temperature when compared with a low temperature. A control apparatus for a direct injection internal combustion engine, wherein an injection timing of at least a first injection is retarded among the injections divided into a plurality of times.