JP2011012616A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of improving startability by appropriately controlling an intake valve lift amount and a fuel injection timing at a low-temperature start and promoting atomization of fuel.SOLUTION: At a low-temperature start in which a fuel pressure PF is lower than a prescribed pressure PFIVC and an engine cooling water temperature TW is lower than a prescribed water temperature TWIVC, an intake valve closing timing command value IVCCMD is set to a prescribed valve closing timing IVCL, and a fuel injection timing θinj is set to a prescribed injection timing θinjL during a period when the intake valve is opened. An intake valve lift amount LFTL corresponding to the prescribed valve closing timing IVCL is set to a value larger than at a normal temperature start in which the engine cooling water temperature TW is the prescribed water temperature TWIVC or higher.

Description

  The present invention relates to a control device for an internal combustion engine including a valve operating mechanism that continuously changes a lift amount of an intake valve and a fuel injection valve that injects fuel into a cylinder.

  Patent Document 1 discloses a control device for an internal combustion engine that includes a valve operating mechanism that continuously changes the lift amount of an intake valve and a fuel injection valve that injects fuel into a cylinder. According to this control device, when the engine is started at a low temperature, in order to promote the vaporization of the injected fuel, the valve opening period of the intake valve is shortened, and the intake valve is closed during the intake stroke. The fuel injection is performed in a plurality of times.

JP 2007-278112 A

  When the intake valve is closed during the intake stroke, the in-cylinder temperature decreases because the air in the cylinder adiabatically expands. For this reason, when the conventional control device is used at the time of low temperature start, the in-cylinder temperature is remarkably lowered, the acceleration of fuel atomization is hindered, and the startability may be deteriorated.

  The present invention has been made paying attention to this point, and appropriately controls the intake valve lift amount and the fuel injection timing in the idle state at the low temperature start and immediately after the start, thereby promoting the atomization of the fuel and improving the startability. An object of the present invention is to provide a control device for an internal combustion engine that can be improved.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a valve lift amount varying means (41) for continuously changing a lift amount (LFT) of an intake valve of an internal combustion engine, and fuel in a cylinder of the engine. In a control apparatus for an internal combustion engine comprising a fuel injection valve (6) for injecting fuel, fuel pressure detection means for detecting the pressure (PF) of fuel supplied to the fuel injection valve (6), and the temperature (TW) of the engine ) For detecting engine temperature, valve lift amount control means for controlling the valve lift amount varying means (41) in accordance with the operating state of the engine, and the fuel injection valve (in accordance with the operating state of the engine). And a fuel injection control means for controlling the fuel injection timing (θinj) according to 6), and the engine temperature (TW) is predetermined when the fuel pressure (PF) is lower than the predetermined fuel pressure (PFIVC). Temperature (TWIV ) Is lower than the lift amount when the engine temperature (TW) is equal to or higher than the predetermined temperature (TWIVC), the valve lift amount control means determines the lift amount of the intake valve (LFTL). ), And the fuel injection timing control means sets the fuel injection timing (θinj) to a period during which the intake valve is opened in the intake stroke of the cylinder that performs fuel injection. .

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the low temperature lift amount (LFTL) is an overlap period in which valve opening periods of the intake valve and the exhaust valve of the cylinder overlap. (CAOL) is set to a lift amount that becomes a predetermined period (CAOLS) in the vicinity of “0”.
Here, the predetermined period in the vicinity of “0” means “0” or a period that is short enough to ignore the influence of the opening of the exhaust valve.

  According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the first or second aspect of the present invention, an in-cylinder pressure estimating unit that estimates a pressure in the cylinder is provided, and the fuel injection control unit includes the fuel pressure ( The valve opening period (TOUT) of the fuel injection valve is corrected based on the difference between PF) and the estimated in-cylinder pressure (PCYLE).

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to the third aspect, the in-cylinder pressure estimating means is a control amount (ALIFT) of the valve lift amount varying means calculated by the valve lift amount control means. , IVC), the estimated in-cylinder pressure (PCYLE) is calculated.

  According to the first aspect of the present invention, when the engine temperature is lower than the predetermined temperature in the predetermined low load operation state where the fuel pressure is lower than the predetermined fuel pressure, the lift amount of the intake valve is such that the engine temperature is equal to or higher than the predetermined temperature. The lift amount for low temperature is set to be larger than the lift amount at the time, and the fuel injection timing is set to the period during which the intake valve is opened in the intake stroke of the cylinder that performs fuel injection. Thereby, atomization of the injected fuel can be promoted without lowering the in-cylinder temperature, and the injected fuel can be uniformly dispersed in the cylinder by the flow of air from the intake passage. Therefore, the combustion stability when the engine temperature is low in a predetermined low load operation state is improved, and the engine can be started even when poor fuel is used, and the effect of preventing the deterioration of exhaust characteristics can be obtained. In addition, since the low temperature lift amount is set only when the fuel pressure is low, the operation period with a relatively large low temperature lift amount can be minimized, and deterioration of exhaust characteristics and fuel consumption can be prevented. .

  According to the second aspect of the present invention, the low-temperature lift amount is set to a lift amount with which the overlap period is a predetermined period in the vicinity of “0”, so that the exhaust valve is substantially in the open period of the intake valve. It can be surely closed and fuel atomization can be promoted. As a result, it is possible to further improve the combustion stability at the low temperature start and in the idle operation state immediately after that.

  According to the third aspect of the present invention, the in-cylinder pressure is estimated, and the valve opening period of the fuel injection valve is corrected based on the difference between the fuel pressure and the estimated in-cylinder pressure. Therefore, the difference between the fuel pressure and the in-cylinder pressure is Even if it is small, the required fuel amount is accurately injected, and the control accuracy of the air-fuel ratio can be improved.

  According to the fourth aspect of the present invention, the estimated in-cylinder pressure is calculated based on the control amount of the valve lift amount varying means. In a direct injection internal combustion engine having a valve lift amount varying means, when the lift amount of the intake valve changes, the in-cylinder pressure changes even if the fuel pressure is the same. Therefore, accurate estimation can be performed by calculating the estimated in-cylinder pressure based on the control amount of the valve lift amount varying means.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a block diagram which shows the structure of the valve action characteristic variable apparatus shown in FIG. It is a figure for demonstrating schematic structure of the 1st valve action characteristic variable mechanism shown in FIG. It is a figure which shows the operating characteristic of an intake valve and an exhaust valve. It is a figure for demonstrating control of the pressure (PF) of the fuel supplied to a fuel injection valve. It is a flowchart of the process which performs valve operation control and fuel injection timing control. It is a figure which shows the table referred by the process of FIG. It is a flowchart of the process which calculates the fuel pressure correction coefficient which correct | amends the fuel injection time by a fuel injection valve. It is a figure which shows the map and table referred by the process of FIG. It is a figure which shows the map referred by the process of FIG.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and its control device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of a valve operating characteristic variable device. In FIG. 1, for example, an internal combustion engine (hereinafter simply referred to as “engine”) 1 having four cylinders includes an intake valve and an exhaust valve, a cam for driving them, and a valve operating characteristic varying device 40. The variable valve operation characteristic device 40 includes a first valve operation characteristic variable mechanism 41 that continuously changes the valve lift amount (maximum lift amount) and the opening angle (valve opening period) of the intake valve, and a cam that drives the intake valve. The second valve operating characteristic variable mechanism 42 as a cam phase variable mechanism that continuously changes the operating phase based on the crankshaft rotation angle, and the exhaust valve lift amount and opening angle (valve opening engine) in two stages And a third valve operating characteristic variable mechanism 47 for switching. The operating phase of the cam that drives the intake valve is changed by the second valve operating characteristic variable mechanism 42, and the operating phase of the intake valve is changed.

  A throttle valve 3 is arranged in the middle of the intake pipe 2 of the engine 1. A throttle valve opening (TH) sensor 4 is connected to the throttle valve 3, and an electric signal corresponding to the opening of the throttle valve 3 is output to an electronic control unit (hereinafter referred to as “ECU”) 5. Supply. An actuator 7 that drives the throttle valve 3 is connected to the throttle valve 3, and the operation of the actuator 7 is controlled by the ECU 5. An intake air flow rate sensor 13 for detecting the intake air flow rate GAIR is provided on the upstream side of the throttle valve 3 in the intake pipe 2, and the detection signal is supplied to the ECU 5.

  Each cylinder of the engine 1 is provided with a fuel injection valve 6 for injecting fuel into the combustion chamber. The fuel injection valve 6 is connected to a delivery pipe 21 via a fuel supply pipe 17, and the delivery pipe 21 is connected to a fuel pump unit 18 in the fuel tank 19 via a fuel pipe 20. The fuel pump unit 18 is configured integrally with a fuel pump 18a, a fuel strainer 18b, and a pressure regulator 18c having a reference pressure as a fuel tank internal pressure. A high pressure pump 23 is provided in the middle of the fuel pipe 20, and the high pressure pump 23 raises the fuel pressure in the delivery pipe 21 to a pressure at which fuel can be injected into the combustion chamber.

The delivery pipe 21 is provided with a fuel pressure sensor 22 that detects the fuel pressure PF. A detection signal of the fuel pressure sensor 22 is supplied to the ECU 5.
The fuel injection valve 6 is electrically connected to the ECU 5, and the valve opening timing (fuel injection timing) and the valve opening time (fuel injection time) are controlled by a drive signal from the ECU 5.

The ignition plug 15 of each cylinder of the engine 1 is connected to the ECU 5, and the ECU 5 supplies an ignition signal to the ignition plug 15 to perform ignition timing control.
An intake pressure sensor 8 for detecting the intake pressure PBA and an intake temperature sensor 9 for detecting the intake temperature TA are attached downstream of the throttle valve 3. An engine cooling water temperature sensor 10 that detects the engine cooling water temperature TW is attached to the main body of the engine 1. Detection signals from these sensors are supplied to the ECU 5.

  The ECU 5 includes a crank angle position sensor 11 that detects a rotation angle of a crankshaft (not shown) of the engine 1 and a cam angle that detects a rotation angle of a camshaft to which a cam that drives an intake valve of the engine 1 is fixed. A position sensor 12 is connected, and signals corresponding to the rotation angle of the crankshaft and the rotation angle of the camshaft are supplied to the ECU 5. The crank angle position sensor 11 generates one pulse (hereinafter referred to as “CRK pulse”) for every predetermined crank angle cycle (for example, a cycle of 6 degrees) and a pulse for specifying a predetermined angular position of the crankshaft. The cam angle position sensor 12 has a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1 and a pulse (hereinafter referred to as “TDC”) at the start of the intake stroke of each cylinder. "TDC pulse"). These pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE. The actual operating phase CAIN of the camshaft is detected from the relative relationship between the TDC pulse output from the cam angle position sensor 12 and the CRK pulse output from the crank angle position sensor 11.

  The ECU 5 includes an accelerator sensor 31 for detecting an accelerator pedal depression amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine 1 and a vehicle speed sensor 32 for detecting a traveling speed (vehicle speed) VP of the vehicle. , And an atmospheric pressure sensor 33 for detecting the atmospheric pressure PA is connected. Detection signals from these sensors are supplied to the ECU 5.

  As shown in FIG. 2, the valve operating characteristic variable device 40 includes a first valve operating characteristic variable mechanism 41 that continuously changes the maximum lift amount and opening angle (hereinafter simply referred to as “lift amount”) of the intake valve, Second valve operating characteristic variable mechanism 42 for continuously changing the valve operating phase, motor 43 for continuously changing the lift amount of the intake valve, and for continuously changing the operating phase of the intake valve The solenoid valve 44 whose opening degree can be continuously changed, the third valve operating characteristic variable mechanism 47 for switching the lift amount and opening angle (opening period) of the exhaust valve in two stages, the lift amount of the exhaust valve, and And an electromagnetic valve 48 for switching the opening angle in two stages. The camshaft operating phase CAIN is used as a parameter indicating the operating phase of the intake valve. Lubricating oil in the oil pan 46 is pressurized and supplied to the electromagnetic valves 44 and 48 by the oil pump 45. A specific configuration of the second valve operating characteristic variable mechanism 42 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-227013. Further, the third valve operating characteristic variable mechanism 47 is employed in commercial vehicles, and its configuration is well known.

  As shown in FIG. 3A, the first valve operating characteristic variable mechanism 41 includes a cam shaft 51 provided with a cam 52, and a control arm 55 supported by a cylinder head so as to be swingable about a shaft 55a. A control shaft 56 provided with a control cam 57 for swinging the control arm 55, and a sub cam 53 swingably supported by the control arm 55 via a support shaft 53b and swinging following the cam 52. And a rocker arm 54 that is driven by the sub cam 53 and drives the intake valve 60. The rocker arm 54 is swingably supported in the control arm 55.

  The sub cam 53 has a roller 53 a that contacts the cam 52, and swings about the shaft 53 b as the cam shaft 51 rotates. The rocker arm 54 has a roller 54a that contacts the sub cam 53, and the movement of the sub cam 53 is transmitted to the rocker arm 54 through the roller 54a.

  The control arm 55 has a roller 55b that abuts on the control cam 57, and swings about the shaft 55a as the control shaft 56 rotates. In the state shown in FIG. 3A, since the movement of the sub cam 53 is hardly transmitted to the rocker arm 54, the intake valve 60 is maintained in a substantially fully closed state. On the other hand, in the state shown in FIG. 5B, the movement of the sub cam 53 is transmitted to the intake valve 60 via the rocker arm 54, and the intake valve 60 opens to the upper limit lift amount LFTMAX (for example, 12 mm).

Therefore, the lift amount LFT of the intake valve 60 can be continuously changed by rotating the control shaft 56 by the motor 43. In the present embodiment, the first valve actuation characteristic variable mechanism 41 is provided with a control shaft rotation angle sensor (hereinafter referred to as “CS angle sensor”) 14 that detects a rotation angle (hereinafter referred to as “CS angle”) CSA of the control shaft 56. The detected CS angle CSA is used as a parameter indicating the lift amount LFT.
The detailed configuration of the first valve operating characteristic variable mechanism 41 is disclosed in Japanese Patent Application Laid-Open No. 2008-25418.

  The first valve operating characteristic variable mechanism 41 changes the lift amount LFT (and opening angle) of the intake valve as shown by the solid line in FIG. Further, the lift amount (and opening angle) of the exhaust valve is changed in two stages by the third valve operating characteristic variable mechanism 47 as shown by the broken line in FIG. In an operating state in which the engine speed NE is relatively low (including when the engine is started and in an idle operating state (hereinafter referred to as “predetermined low load operating state”)), a low lift characteristic (broken line L1) is selected. When the engine temperature is low in the predetermined low-load operation state of the engine, a characteristic indicated by a solid line L2 (hereinafter referred to as “predetermined lift characteristic”) is selected as the operating characteristic of the intake valve. In the predetermined lift characteristic, the opening timing of the intake valve coincides with the closing timing of the exhaust valve (see IVOL in FIG. 4A), and the overlap period of the exhaust valve opening period and the intake valve opening period Is an operation characteristic in which becomes "0". In other words, the predetermined lift characteristic is a characteristic that maximizes the lift amount LFT of the intake valve under the condition that the overlap period is “0”.

  Due to the second valve operating characteristic variable mechanism 42, the intake valve is centered on the characteristics indicated by the solid lines L13 and L14 in FIG. 5B, and the most advanced angle indicated by the broken lines L11 and L12 with the change of the cam operating phase CAIN. It is driven at a phase between the phase and the most retarded angle phase indicated by alternate long and short dash lines L15 and L16.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, etc., and a central processing unit (hereinafter referred to as “CPU”). ) In addition to a storage circuit that stores a calculation program executed by the CPU, a calculation result, and the like, an output circuit that supplies a drive signal to the actuator 7, the fuel injection valve 6, the motor 43, and the electromagnetic valves 44 and 48 .

  The CPU of the ECU 5 controls the opening degree of the throttle valve 3, the fuel injection control (control of the fuel injection timing and the fuel injection time by the fuel injection valve 6), the motor 43, the electromagnetic valves 44, 48 according to the detection signal of the sensor. The control of the valve operating characteristics by the control and the control of the fuel pressure PF by the high-pressure pump 13 are performed.

  FIG. 5 is a diagram for explaining the control of the fuel pressure PF. The fuel pressure PF is basically controlled to increase as the engine load EL increases. The load range R1 shown in FIG. 5 corresponds to the engine start, the load range R2 corresponds to the idle operation state, the load range R3 corresponds to the normal operation state, and the load range R4 has the maximum intake valve lift amount LFT. Corresponding to the high-load operation condition. In a predetermined low load operation state (when the engine is started and in an idle operation state), the fuel pressure PF is set to a value smaller than a predetermined pressure PFIVC (for example, 4 MPa).

FIG. 6 is a flowchart of processing for performing valve operation control and fuel injection timing control, and this processing is executed by the CPU of the ECU 5 every predetermined time.
In step S11, it is determined whether or not the fuel pressure PF is equal to or higher than a predetermined pressure PFIVC. If the answer is negative (NO), is the engine cooling water temperature TW equal to or higher than a predetermined water temperature TWIVC (for example, 0 ° C.)? It is determined whether or not (step S12).
If the answer to step S11 or S12 is affirmative (YES), a CAINCMD map (not shown) according to the engine speed NE and the target intake air amount GAIRCMD (calculated according to the accelerator pedal operation amount AP). And cam operation phase command value CAINCMD is calculated (step S17). In step S18, an ALIFTCMD map (not shown) is searched according to the engine speed NE and the target intake air amount GAIRCMD to calculate an intake valve lift amount command value ALIFT. Then, according to the calculated cam operation phase command value CAINCMD and lift amount command value ALIFT, and other control parameters calculated according to the engine operating state, normal valve operation control (control of the motor 43, the electromagnetic valves 44, 48). (Step S19) and normal fuel injection timing control according to the engine operating state is performed (step S20).

  If the answer to step S12 is negative (NO), that is, if the fuel pressure PF is lower than the predetermined pressure PFIVC and the engine cooling water temperature TW is lower than the predetermined water temperature TWIVC, the intake valve closing timing command value IVCCMD is predetermined closed. The valve timing IVCL (see FIG. 4) is set (step S13), and the cam operation phase command value CAICMD is set to “0” (a value corresponding to the most retarded phase) (step S14).

  In step S15, the ALIFT table shown in FIG. 7 is searched according to the valve closing timing command value IVCCMD, and the lift amount command value ALIFT is calculated. The ALIFT table in FIG. 7 corresponds to a state where the cam operation phase CAIN is 0 deg. In step S16, the fuel injection timing θinj is set to a predetermined injection timing θinjL. The predetermined injection timing θinjL is set to, for example, 100 deg (with the start timing of the intake stroke being 0 deg) within the period during which the intake valve during the intake stroke is open. As described above, the valve operating characteristic of the exhaust valve at this time is set to the characteristic indicated by the broken line L1 in FIG.

  When the engine cooling water temperature TW is lower than the predetermined water temperature TWIVC in the predetermined low load operation state, the cam operation phase CAIN indicating the operation phase of the intake valve is fixed at 0 deg. Therefore, the valve closing timing command value IVCCMD is set to the predetermined valve closing timing IVCL. As a result, the valve operating characteristic of the intake valve becomes a predetermined lift characteristic indicated by a solid line L2 in FIG. 4A, and the lift amount LFT becomes a value LFTL corresponding to the solid line L2. The predetermined valve closing timing IVCL corresponds to a predetermined lift amount LFTL, and this predetermined lift amount LFTL is larger than the lift amount LFTSH applied when the engine cooling water temperature TW is higher than the predetermined water temperature TWIVC in the predetermined low load operation state.

  According to the process of FIG. 6, when the engine cooling water temperature TW is lower than the predetermined water temperature TWIVC in the predetermined low load operation state, the intake valve lift amount LFT is larger than when the engine cooling water temperature TW is equal to or higher than the predetermined water temperature TWIVC. Since the fuel is injected during the period when the intake valve is open, atomization of the injected fuel can be promoted without lowering the in-cylinder temperature (combustion chamber temperature), and The injected fuel can be uniformly dispersed in the cylinder (combustion chamber) by the flow of air from the intake pipe 2. Therefore, combustion stability is improved, and starting is possible even when poor fuel is used. In addition, an effect of preventing deterioration of exhaust characteristics can be obtained. Further, since the low temperature lift amount LFTL is set only when the fuel pressure is low (PF <PFIVC), the operation period in which a relatively large lift amount (LFTL) is applied is minimized, and the exhaust gas is exhausted. Deterioration of characteristics and fuel consumption can be prevented.

  In addition, since the overlap period in which the valve opening period of the exhaust valve and the valve opening period of the intake valve overlap is set to “0”, the exhaust valve is reliably operated during the valve opening period of the intake valve. The valve is closed and fuel atomization can be promoted. As a result, combustion stability can be further improved.

  FIG. 8 is a flowchart of a process for calculating the fuel pressure correction coefficient KPF, and this process is executed by the CPU of the ECU 5 every predetermined time. The fuel pressure correction coefficient KPF is a correction coefficient applied to the calculation of the fuel injection time TOUT by the fuel injection valve 6.

  In step S21, an IVC map shown in FIG. 9A is retrieved according to the intake valve lift amount command value ALIFT and the cam operation phase command value CAINCMD to calculate the intake valve closing timing IVC. In this embodiment, it is defined that an increase in the cam operation phase command value CAINCMD corresponds to an advance angle, and an increase in the intake valve closing timing IVC corresponds to a delay angle, and the IVC map shows the cam operation phase command value. The intake valve closing timing IVC decreases (advance) as CAINCMD increases (advance), and the intake valve closing timing IVC increases (retards) as the lift amount command value ALIFT increases. Has been. That is, the lines L21 to L25 shown in FIG. 9A correspond to the predetermined lift amounts ALIFT1 to ALIFT5, and the predetermined lift amounts ALIFT1 to ALIFT5 satisfy the relationship ALIFT1 <ALIFT2 <ALIFT3 <ALIFT4 <ALIFT5.

  In step S22, the θinj map shown in FIG. 9B is searched according to the engine speed NE and the intake pressure PBA, and the fuel injection timing θinj is calculated. In the present embodiment, the fuel injection timing θinj is set so as to increase in the retarding direction with the start timing of the intake stroke being “0”. The θinj map is set so that the fuel injection timing θinj decreases (advances) as the intake pressure PBA increases, and the fuel injection timing θinj decreases (advances) as the engine speed NE increases. . That is, the lines L31 to L35 shown in FIG. 9B correspond to the predetermined rotational speeds NE1 to NE5, and the predetermined rotational speeds NE1 to NE5 satisfy the relationship NE1 <NE2 <NE3 <NE4 <NE5.

  In step S23, it is determined whether or not the fuel injection timing θinj is greater than a predetermined injection timing θinjdisc (for example, 180 degrees). When this answer is affirmative (YES), that is, when the fuel injection timing θinj is in the compression stroke, the routine proceeds to step S24, and the KPCYL1 table shown in FIG. 9 (c) is searched according to the intake pressure PBA. One coefficient value KPCYL1 is calculated. The KPCYL1 table is set so that the first coefficient value KPCYL1 increases as the intake pressure PBA increases.

  In step S25, the PCYLSTD1 map shown in FIG. 10A is retrieved according to the intake valve closing timing IVC and the fuel injection timing θinj to calculate the first reference in-cylinder pressure PCYLSTD1. The PCYLSTD1 map shows that the first reference in-cylinder pressure PCYLSTD1 decreases as the intake valve closing timing IVC increases (retards), and the first reference in-cylinder pressure PCYLSTD1 increases as the fuel injection timing θinj increases (retards). It is set to be. That is, the lines L41 to L45 shown in FIG. 10A correspond to the predetermined injection timings θinj1 to θinj5, and the predetermined injection timings θinj1 to θinj5 satisfy the relationship of θinj1 <θinj2 <θinj3 <θinj4 <θinj5.

  In step S26, the in-cylinder pressure correction coefficient KPCYL is set to the first coefficient value KPCYL1, and the reference in-cylinder pressure PCYLSTD is set to the first reference in-cylinder pressure PCYLSTD1.

In step S30, the in-cylinder pressure correction coefficient KPCYL and the reference in-cylinder pressure PCYLSTD are applied to the following equation (1) to calculate an estimated in-cylinder pressure PCYLE that is an estimated value of the in-cylinder pressure at the fuel injection timing θinj.
PCYLE = KPCYL × PCYLSTD (1)

In step S31, the fuel pressure correction coefficient KPF is calculated by applying the fuel pressure PF and the estimated in-cylinder pressure PCYLE detected in the following equation (2). PFBASE in equation (2) is a reference fuel pressure, and is set to a predetermined value.

  On the other hand, if θinj ≦ θinjdisc in step S23 and the fuel injection timing θinj is in the intake stroke, the process proceeds to step S27 to search the KPCYL2 table shown in FIG. The numerical value KPCYL2 is calculated. The KPCYL2 table is set such that the second coefficient value KPCYL2 increases as the intake pressure PBA increases, and the second coefficient value KPCYL2 is set to a value smaller than the first coefficient value KPCYL1 at the same intake pressure. .

  In step S28, the PCYLSTD2 map shown in FIG. 10B is searched according to the lift amount command value ALIFT and the fuel injection timing θinj, and the second reference in-cylinder pressure PCYLSTD2 is calculated. The PCYLSTD2 map is set such that the second reference in-cylinder pressure PCYLSTD2 decreases as the lift amount command value ALIFT increases (retards), and the second reference in-cylinder pressure PCYLSTD2 decreases as the fuel injection timing θinj increases. ing. That is, the lines L51 to L55 shown in FIG. 10B correspond to the predetermined injection timings θinj11 to θinj15, and the predetermined injection timings θinj11 to θinj15 satisfy the relationship θinj11 <θinj12 <θinj13 <θinj14 <θinj15.

  In step S29, the cylinder pressure correction coefficient KPCYL is set to the second coefficient value KPCYL2, and the reference cylinder pressure PCYLSTD is set to the second reference cylinder pressure PCYLSTD2. Next, the process proceeds to step S30.

  In the process of FIG. 8, the calculation method of the estimated in-cylinder pressure PCYLE is changed according to whether the fuel injection timing θinj is in the intake stroke or the compression stroke. This is based on the following reasons. In the compression stroke, the gas in the combustion chamber is adiabatically compressed, while in the intake stroke, fresh air is introduced into the combustion chamber, so that the state is close to isothermal expansion. Therefore, in the compression stroke, the basic in-cylinder pressure PCYLSTD is calculated according to the intake valve closing timing IVC, while in the intake stroke, the basic in-cylinder pressure PCYLSTD is calculated according to the lift amount command value ALIFT, so that the gas state in each stroke is calculated. In-cylinder pressure can be accurately estimated according to

The fuel injection time TOUT is calculated by applying the fuel pressure correction coefficient KPF to the following equation (3). TI in equation (3) is a basic fuel injection time calculated so that the air-fuel mixture in the combustion chamber has a predetermined air-fuel ratio according to the intake air flow rate GAIR, and KCR is an engine cooling water temperature TW, intake air temperature TA, etc. It is the product of various correction factors set accordingly.
TOUT = TI × KPF × KCR (3)

  Since the basic fuel injection time TI is corrected by the fuel pressure correction coefficient KPF by the equation (3) and the fuel injection time TOUT is calculated, for example, when the difference between the fuel pressure and the in-cylinder pressure at the fuel injection timing is small. However, the required fuel amount is accurately injected, and the control accuracy of the air-fuel ratio can be improved.

  In the process of FIG. 8, the estimated in-cylinder pressure PCYLE is calculated based on the lift amount command value ALIFT or the intake valve closing timing IVC, which is the control amount of the first valve operating characteristic variable mechanism 41. In a direct injection internal combustion engine having a valve operating mechanism that changes the lift amount of the intake valve, if the lift amount of the intake valve changes, the in-cylinder pressure changes even if the fuel pressure is the same, so the lift amount command value ALIFT or the intake valve closing By calculating the estimated in-cylinder pressure PCYLE based on the timing IVC, an accurate estimated in-cylinder pressure can be obtained.

  In the present embodiment, the first valve operating characteristic variable mechanism 41 corresponds to a valve lift amount variable means, and the fuel pressure sensor 22 and the engine coolant temperature sensor 10 correspond to a fuel pressure detection means and an engine temperature detection means, respectively. The ECU 5 constitutes a valve lift amount control means, a fuel injection control means, and an in-cylinder pressure estimation means. Specifically, the processing in FIG. 6 corresponds to the valve lift amount control means and the fuel injection control means, steps S21 to S30 in FIG. 8 correspond to the in-cylinder pressure estimation means, and step S31 corresponds to a part of the fuel injection control means. It corresponds to.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the low temperature lift amount is set to the lift amount LFTL in which the overlap period CAOL in which the intake valve and exhaust valve opening periods overlap is “0”, but the overlap period is relatively short. Since there is almost no influence of the exhaust valve being opened together with the intake valve, the intake valve lift amount is such that the low temperature lift amount is such that the overlap period CAOL is a minute predetermined period CAOLS (for example, 5 degrees) or less. You may make it set to.

  In the above-described embodiment, the engine coolant temperature sensor 10 is used as the engine temperature detecting means. However, for example, an oil temperature sensor for detecting the temperature of the engine oil is provided, and the oil temperature sensor is used as the engine temperature detecting means. Also good.

  The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

1 Internal combustion engine 5 Electronic control unit (valve lift control means, fuel injection control means, in-cylinder pressure estimation means)
6 Fuel injection valve 10 Engine coolant temperature sensor (Engine temperature detection means)
22 Fuel pressure sensor (Fuel pressure detection means)
23 High pressure pump 41 First valve operating characteristic variable mechanism (Valve lift amount variable means)

Claims (4)

In a control apparatus for an internal combustion engine, comprising: a valve lift amount varying means for continuously changing a lift amount of an intake valve of the internal combustion engine; and a fuel injection valve for injecting fuel into a cylinder of the engine.
Fuel pressure detecting means for detecting the pressure of the fuel supplied to the fuel injection valve;
Engine temperature detecting means for detecting the temperature of the engine;
Valve lift amount control means for controlling the valve lift amount variable means in accordance with the operating state of the engine;
Fuel injection control means for controlling the fuel injection timing by the fuel injection valve according to the operating state of the engine,
When the engine temperature is lower than a predetermined temperature in a predetermined low load operation state in which the fuel pressure is lower than a predetermined fuel pressure, the valve lift amount control means determines the lift amount of the intake valve, and the engine temperature is the predetermined temperature. The fuel injection timing control means sets the fuel injection timing to a lift amount for low temperature that is larger than the lift amount at the time of the above, and the intake valve is opened during the intake stroke of the cylinder that performs fuel injection. A control apparatus for an internal combustion engine, characterized in that the period is set.   2. The lift amount for low temperature is set to a lift amount at which an overlap period in which valve opening periods of an intake valve and an exhaust valve of the cylinder overlap is a predetermined period in the vicinity of “0”. The internal combustion engine control device described. In-cylinder pressure estimating means for estimating the pressure in the cylinder,
3. The control device for an internal combustion engine according to claim 1, wherein the fuel injection control unit corrects a valve opening period of the fuel injection valve based on a difference between the fuel pressure and the estimated in-cylinder pressure. .   4. The internal combustion engine according to claim 3, wherein the in-cylinder pressure estimating means calculates the estimated in-cylinder pressure based on a control amount of the valve lift amount varying means calculated by the valve lift amount control means. Control device.

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