JP5026499B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to an apparatus for controlling the engine speed to be constant in an idle state of the internal combustion engine.

  Patent Document 1 discloses a control method in which, in an idling state of an internal combustion engine, the feed mixture amount is feedback-controlled so that the engine speed matches the target speed, and the ignition timing is similarly feedback-controlled. . In this control method, when the feedback control of the ignition timing is not performed, the ignition timing is set to a basic advance value calculated according to the engine speed and the intake air amount, and the feedback control is performed using the engine speed and the target speed. Is performed by adding a correction amount set to a positive or negative value to the basic advance value.

Japanese Patent Publication No. 3-16500

  It is well known that when the ignition timing is changed, the engine output torque changes and becomes maximum at the optimum ignition timing (MBT: Minimum Advance for Best Torque). Therefore, when the ignition timing is in the vicinity of the optimum ignition timing, the amount of change in the engine output torque with respect to the change in the ignition timing is small. However, Patent Document 1 only describes that the basic advance value is calculated according to the engine rotational speed and the intake air amount, and this point is not taken into consideration. Therefore, when the setting of the center ignition timing of the feedback control is inappropriate, since the amount of change in the engine output torque with respect to the change in the ignition timing is small, the control responsiveness of the engine speed may be reduced.

  The present invention has been made paying attention to this point, and provides a control device for an internal combustion engine that can appropriately set the control center value of the ignition timing in an idle state of the engine and further stabilize the engine speed. The purpose is to do.

In order to achieve the above object, according to a first aspect of the present invention, there is provided an internal combustion engine control device comprising an ignition timing control means for controlling an ignition timing of an internal combustion engine, and an intake pressure detection for detecting an intake pressure (PBA) of the engine. Means, a rotational speed detecting means for detecting the rotational speed (NE) of the engine, a margin amount calculating means for calculating an ignition timing margin (DIGCNT) according to the intake pressure (PBA), and the rotational speed (NE). ) And intake pressure (PBA), and an optimal ignition timing calculating means for calculating an optimal ignition timing (MBT) that maximizes the output torque of the engine, and an ignition timing margin (from the optimal ignition timing (MBT)) DIGCNT) is calculated as an optimum central ignition timing (IGCMBT), and the control center ignition timing (IGCNT) is set to the optimal central ignition timing (IGCMBT). A central ignition timing setting means, and the feedback correction amount calculating means for calculating the rotational speed (NE) and the target idle speed feedback correction amount of the ignition timing to match the (NEOBJ) (IGFB), knocking in said engine limit ignition timing is ignition timing can occur is high (IGKNOCK), and a limit ignition timing calculation means for calculating in accordance with the rotational speed (NE) and the intake pressure (PBA), the margin amount calculating means Includes control width definition amount calculation means for calculating a control width definition amount (DIGCTL) indicating a variable range of the feedback correction amount (IGFB), and the control center ignition timing setting means includes the limit ignition timing (IGKNOCK). To the ignition timing on the retard side by the control width definition amount (DIGCTL) from the knock limit dependent ignition timing (IGCKNK) When the knock limit dependent ignition timing (IGCKNK) is retarded from the optimum center ignition timing (IGCMBT), the control center ignition timing (IGCNT) is calculated as the knock limit dependent ignition timing (IGCKNK). The ignition timing control means controls the ignition timing using the control center ignition timing (IGCNT) and the feedback correction amount (IGFB) in the engine idle state.

According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect, an intake air flow rate control means for controlling an intake air flow rate of the engine and a target intake pressure (PBACMD) of the engine are set. Target intake pressure setting means, and the intake air flow rate control means controls the intake air flow rate so that the detected intake pressure (PBA) matches the target intake pressure (PBACMD), and the target intake pressure flow control means. The atmospheric pressure setting means includes temporary target intake air flow rate calculation means for calculating a temporary target intake air flow rate (GACTMP) in accordance with a target torque (TRQIDL) in an idle state of the engine, and the temporary target intake air flow rate (GACTMP) The first step of calculating the temporary target intake pressure (PBCTMP) according to the temporary target intake pressure (DBTMMP) according to the temporary target intake pressure (PBCTMP) ), A third step of calculating a reduction rate (KTRQDN) of the output torque of the engine in accordance with the temporary ignition timing margin (DIGTMP), and the temporary target intake air flow rate (GACTMP) The fourth step of updating the temporary target intake air flow rate (GACTMP) by dividing by the decrease rate (KTRQDN) is repeatedly executed, and the target intake pressure (PBACMD) is set to the current value of the decrease rate (KTRQDN) and the previous time. The provisional target intake pressure (PBCTMP) when the difference from the value becomes equal to or less than a predetermined threshold value (DTRTH) is set.

According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the second aspect , the engine includes a variable valve operation characteristic mechanism (41) for continuously changing a lift amount (LFT) of the intake valve, A lift amount control means for controlling a lift amount (LFT) of the intake valve via the valve operating characteristic variable mechanism is further provided, and the lift amount control means sets the lift amount (LFT) to a predetermined value in an idle state of the engine. It is characterized by maintaining a low lift amount (LFTIDL).

According to the first aspect of the present invention, the ignition timing margin is calculated according to the intake pressure, the ignition timing retarded by the ignition timing margin from the optimal ignition timing is calculated as the optimal center ignition timing, and the control center The ignition timing is set to the optimum center ignition timing. Then, in the engine idle state, feedback control for making the engine speed coincide with the target idle speed is performed using the feedback correction amount with the control center ignition timing as the center. Therefore, since the ignition timing is changed around the retarded ignition timing by the ignition timing margin from the optimal ignition timing, sufficient control response of the engine output torque is ensured and the engine speed is stabilized at the target speed. Can be maintained. In addition, the control width definition amount indicating the variable range of the feedback correction amount is calculated, and the ignition timing that is retarded by the control width definition amount from the limit ignition timing that is the ignition timing at which the possibility of knocking increases is dependent on the knock limit. While calculated as the ignition timing and when the knock limit dependent ignition timing is retarded from the optimum center ignition timing, the control center ignition timing is set to the knock limit dependent ignition timing. Even when the engine is in an idle state, the intake pressure may be controlled to be relatively high. In such a state, the knock limit dependent ignition timing is retarded from the optimum center ignition timing. Therefore, by setting the control center ignition timing to the knock limit dependent ignition timing, knocking can be reliably prevented while ensuring the control response of the engine output torque.

According to the second aspect of the present invention, the intake air flow rate is controlled so that the detected intake pressure matches the target intake pressure, and the temporary target intake air flow rate is calculated according to the target torque in the engine idle state. The Further, a first step for calculating a temporary target intake pressure according to the temporary target intake air flow, a second step for calculating a temporary ignition timing margin according to the temporary target intake pressure, and an engine output according to the temporary ignition timing margin. The third step of calculating the torque reduction rate and the fourth step of updating the temporary target intake air flow rate by dividing the temporary target intake air flow rate by the reduction rate are repeatedly executed. The temporary target intake pressure at the time when the difference between the value and the previous value becomes equal to or less than a predetermined threshold is set. When calculating the target intake pressure according to the target intake air flow rate and controlling the intake air flow rate so that the detected intake pressure matches the target intake pressure, the intake pressure changes due to the change in the intake air flow rate, The ignition timing margin also changes. As a result, when the control center ignition timing is set to an ignition timing that is retarded from the optimal ignition timing, the output torque reduction rate changes and it is necessary to change the target intake air flow rate. The rate of decrease converges to a constant value. Therefore, by adopting the temporary target intake pressure at the time when the rate of decrease converges as the target intake pressure, control instability due to mutual interference between intake air flow control and ignition timing control is prevented, and the engine speed in the idle state Can be further stabilized.

According to the third aspect of the invention, since the lift amount of the intake valve is maintained at a predetermined low lift amount in the engine idle state, control of the lift amount of the intake valve and the intake air flow rate by the intake air flow rate control means Mutual interference with the control is eliminated, and the engine speed in the idle state can be stabilized.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of an internal combustion engine and its control device according to an embodiment of the present invention, and FIG. 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 lift amount and an opening angle (open valve) of the intake valve. The first valve operating characteristic variable mechanism 41 that continuously changes the period) and the second cam phase variable mechanism that continuously changes the operating phase of the cam that drives the intake valve with reference to the crankshaft rotation angle. A variable valve operation characteristic device 40 having a variable valve operation characteristic mechanism 42 is provided. 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.

  The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). At the same time, it is electrically connected to the ECU 5 and the valve opening time of the fuel injection valve 6 is controlled by a 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 air temperature sensor 9 for detecting the intake air 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”) every predetermined crank angle period (for example, 30 degree period) and a pulse for specifying a predetermined angle 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 lift amount and opening angle (hereinafter simply referred to as “lift amount”) of the intake valve, and the intake valve. The second valve operating characteristic variable mechanism 42 for continuously changing the operation phase of the engine, the motor 43 for continuously changing the lift amount LFT of the intake valve, and the operation phase of the intake valve for changing continuously. And an electromagnetic valve 44 whose opening degree can be continuously changed. 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 valve 44 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.

  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 maximum 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 lift amount LFT (and opening angle) of the intake valve is changed by the first valve operating characteristic variable mechanism 41 as shown in FIG. In addition, the second valve operating characteristic variable mechanism 42 causes the intake valve to move forward as indicated by broken lines L1 and L2 as the cam operating phase CAIN changes, centering on the characteristics indicated by solid lines L3 and L4 in FIG. It is driven at a phase between the angular phase and the most retarded phase indicated by the alternate long and short dash lines L5 and L6.

  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 for storing a calculation program executed by the CPU, a calculation result, and the like, the actuator 7, the fuel injection valve 6, the ignition plug 15, the motor 43, an output circuit for supplying a drive signal to the electromagnetic valve 44, etc. Is done.

  The CPU of the ECU 5 controls the opening degree of the throttle valve 3, the amount of fuel supplied to the engine 1 (the valve opening time of the fuel injection valve 6), the ignition timing control, the motor 43, Control of valve operating characteristics (intake air flow rate) by the electromagnetic valve 44 is performed.

Next, the outline of the ignition timing control in this embodiment will be described with reference to FIG.
FIG. 5A is a diagram showing the relationship between the ignition timing IG and the engine output torque when the engine is in an idle state. The ignition timing IG has an optimum ignition timing MBT (Minimum Spark Advance for Best Torque) of “0”. The advance direction is shown as plus. The engine output torque is indicated by a torque ratio η based on the output torque at the optimal ignition timing. The relationship between the ignition timing IG and the torque ratio η hardly changes even if the lift amount LFT of the intake valve, the intake air flow rate GAIR, or the engine speed NE changes, and the characteristics shown in FIG. It has been experimentally confirmed that Therefore, in consideration of the characteristics shown in FIG. 5A, in the present embodiment, the ignition timing that is retarded by the margin amount DIGCNT from the optimal ignition timing MBT is centered (in other words, a non-linear region near the optimal ignition timing is avoided). ) By performing the ignition timing control in the idle state, good controllability of the engine output torque by changing the ignition timing IG is ensured, and the idling speed is stabilized.

  FIG. 5B is a diagram showing the relationship between the intake pressure PBA and the ignition timing IG, where the solid line L11 indicates the optimum ignition timing MBT, and the broken line L12 indicates the minimum advance amount at which knocking is likely to occur. IGKNOCK (hereinafter referred to as “knock limit ignition timing”) IGKNOCK, and a solid line L13 indicates a central ignition timing IGCNT that is the center of ignition timing control. The intake pressures PB1 to PB3 shown in FIG. 5B are, for example, about 48 kPa, 61 kPa, and 75 kPa, respectively.

  In the present embodiment, in the idling state, the engine speed NE is made equal to the target idle speed NEOBJ by changing the ignition timing in the range (IGCNT ± DIGCTL) indicated by the broken line with the center ignition timing IGCNT as the center. Feedback control is performed. DIGCTL is a parameter corresponding to ½ of the control range width of the ignition timing, and is hereinafter referred to as “control width definition amount”. DIGNL shown in FIG. 5B is a parameter indicating the width of the nonlinear region on the retard side of the optimal ignition timing (region where the change in output torque with respect to the change in ignition timing is nonlinear). Called).

  The center ignition timing IGCNT is basically set to the retard side by a margin amount DIGCNT (= DIGCTL + DIGNL) from the optimum ignition timing MBT, but the ignition timing retarded by the control width definition amount DIGCTL from the knock limit ignition timing IGKNOCK. When IGCKNK (hereinafter referred to as “knock limit dependent ignition timing”) is retarded from (MBT-DIGCNT), the center ignition timing IGCNT is set to the knock limit dependent ignition timing IGCKNK. As a result, knocking can be reliably prevented while ensuring controllability of the engine output torque.

  FIG. 6 is a block diagram showing the configuration of a module that performs the ignition timing control in the idle state described above. The function of the module shown in FIG. 6 is realized by arithmetic processing in the CPU of the ECU 5.

  The module shown in FIG. 6 includes an optimum ignition timing calculation unit 71, a control width definition amount calculation unit 72, a knock limit ignition timing calculation unit 73, addition units 74 and 79, subtraction units 75 and 76, and a selection unit 77. And a feedback control unit 78.

  The optimal ignition timing calculation unit 71 calculates the optimal ignition timing MBT according to the engine speed NE, the intake pressure PBA, the intake air temperature TA, and the cooling water temperature TW. Specifically, an MBT map set according to the engine speed NE and the intake pressure PBA is searched to calculate a map value MBTM, and the map value MBTM is corrected according to the intake air temperature TA and the coolant temperature TW. The optimal ignition timing MBT is calculated. A representative map value MBTM (for example, corresponding to NE = 800 rpm) is set so as to decrease as the intake pressure PBA increases, as indicated by a solid line L21 in FIG. Although only the solid line L21 is shown in FIG. 7, in the MBT map, for example, in the range of 550 rpm to 2000 rpm, a map value corresponding to the solid line 21 is set corresponding to a predetermined rotation value set at intervals of 100 to 250 rpm. The vertical axis in FIG. 7 indicates the amount of advance from the top dead center.

  The control width definition amount calculation unit 72 searches the DIGCTL table shown in FIG. 8 according to the intake pressure PBA, and calculates the control width definition amount DIGCTL. The DIGCTL table is set so that the control width definition amount DIGCTL decreases as the intake pressure PBA increases. The ignition timing change amount necessary to obtain the same engine output torque change amount corresponds to a decrease as the intake pressure PBA increases.

  Knock limit ignition timing calculation unit 73 calculates knock limit ignition timing IGKNOCK according to engine speed NE, intake pressure PBA, intake air temperature TA, and cooling water temperature TW. Specifically, a map value IGKNOCKM is calculated by searching an IGKNOCK map set according to the engine speed NE and the intake pressure PBA, and the map value IGKNOCKM is corrected according to the intake air temperature TA and the cooling water temperature TW. The knock limit ignition timing IGKNOCK is calculated. A representative map value IGKNOCKM (for example, corresponding to NE = 800 rpm) is set so as to decrease as the intake pressure PBA increases, as indicated by a broken line L22 in FIG. Although only the broken line L22 is shown in FIG. 7, in the IGKNOCK map, for example, a map value corresponding to the broken line 22 is set corresponding to a predetermined rotation value set at intervals of 100 to 250 rpm in the range of 550 rpm to 2000 rpm. The subtracting unit 76 calculates the knock limit dependent ignition timing IGCKNK by subtracting the control width definition amount DIGCTL from the knock limit ignition timing IGKNOCK.

  The adding unit 74 adds a non-linear region width DIGNL (see FIG. 5B) to the control width definition amount DIGCTL to calculate a margin amount DIGCNT. The subtracting unit 75 calculates the optimum center ignition timing IGCMBT by subtracting the margin amount DIGCNT from the optimum ignition timing MBT. The selection unit 77 compares the optimum center ignition timing IGCMBT with the knock limit dependent ignition timing IGCKNK, selects the smaller one (the retard side), and outputs it as the center ignition timing IGCNT.

  The feedback control unit 78 calculates the feedback correction amount IGFB by, for example, proportional control so that the engine speed NE matches the target idle speed NEOBJ. The adding unit 79 calculates the ignition timing IGLOG by adding the feedback correction amount IGFB to the center ignition timing IGCNT. The ignition timing IGLOG is indicated by an advance amount from the compression top dead center.

  According to the ignition timing control module shown in FIG. 6, when the engine speed NE is feedback-controlled to the target idle speed NEOBJ, the center ignition timing IGCNT can secure a necessary output torque change amount, and the change in the ignition timing. Therefore, a sufficient control response of the engine output torque is ensured, and the engine speed NE is stably maintained at the target idle speed NEOBJ. be able to. Further, since the center ignition timing IGCNT is set so that a portion close to the optimal ignition timing MBT is used in a range in which the linearity of the engine output torque change can be ensured, deterioration of fuel consumption can be suppressed.

  Further, the intake pressure PBA may be controlled to be relatively high even in the idling state. In such a state, the knock limit dependent ignition timing IGCKNK may be retarded from the optimum center ignition timing IGCMBT. In such a case, by setting the central ignition timing IGCNT to the knock limit dependent ignition timing IGCKNK, knocking can be reliably prevented while ensuring controllability of the engine output torque.

  Next, intake valve lift amount control and throttle valve opening control in this embodiment will be described.

  FIG. 9 is a block diagram showing a configuration of a module that calculates a CS angle command value CSACMD corresponding to the lift amount command value LFTCMD of the intake valve and a target throttle valve opening THCMD that is a command value of the throttle valve opening TH. . The function of the module shown in FIG. 9 is realized by arithmetic processing in the CPU of the ECU 5. The motor 43 is controlled so that the detected CS angle CSA matches the CS angle command value CSACMD, and the actuator 7 is controlled so that the detected throttle valve opening TH matches the target throttle valve opening THCMD. The

  The module shown in FIG. 9 includes a target torque calculator 81, a target intake air flow rate calculator 82, a target lift amount calculator 83, an angle command value calculator 84, a target intake pressure calculator 85, and a target throttle valve. And an opening degree calculation unit 86.

  The target torque calculation unit 81 calculates a target torque TRQ of the engine 1 according to the accelerator pedal operation amount AP and the engine speed NE. Target torque TRQ is set to increase as accelerator pedal operation amount AP increases. The target intake air flow rate calculation unit 82 calculates a target intake air flow rate GAIRCMD according to the target torque TRQ.

  The target lift amount calculation unit 83 calculates a target lift amount LFTCMD according to the target intake air flow rate GAIRCMD and the engine speed NE. The angle command value calculation unit 84 calculates the CS angle command value CSACMD according to the target lift amount LFTCMD.

  The target intake pressure calculation unit 85 calculates a target intake pressure PBA according to the target torque TRQ. The target throttle valve opening degree calculation unit 86 calculates the target throttle valve opening degree THCMD so that the detected intake pressure PBA matches the target intake pressure PBACMD.

  FIG. 10 is a flowchart of a process for realizing the functions of the target torque calculation unit 81 and the target intake pressure calculation unit 85 when the engine 1 is in the idling operation state. This process is executed by the CPU of the ECU 5 every predetermined time. In the present embodiment, the target lift amount LFTCMD is set to the predetermined idle lift amount LFTIDL in the idle state.

In step S11, a required torque in idle operation (hereinafter referred to as “idle required torque”) TRQIDL is calculated. Specifically, it is calculated by the following formula (1).
TRQIDL = TRQLOAD + TRQENGFRQ (1)
When the idle request torque TRQIDL calculated by the equation (1) is different from the previous value (including the case where it is calculated first immediately after the engine is started), the initialization flag FINI is set to “0”.

  TRQLOAD is an auxiliary load torque TRQLOAD corresponding to auxiliary loads such as an air conditioner, a generator, a power steering, and an automatic transmission. TRQENGFRQ is a sum of friction loss due to engine rotation and pumping loss torque due to intake and exhaust. This is the mechanical loss torque. The auxiliary machine load torque TRQLOAD is calculated according to the on / off state of the corresponding auxiliary machine, the engine speed NE, and the like, and the mechanical loss torque TRQENGFRQ is calculated according to the engine speed NE, the coolant temperature TW, the intake pressure PBA, and the like. .

In step S12, it is determined whether or not the initialization flag FINI is “1”. When the initialization flag FINI is “0”, the process proceeds to step S13, and the temporary target intake air flow rate GACTMP is calculated according to the idle request torque TRQIDL. The temporary target intake air flow rate GACTMP is calculated by a table search or the following equation (2) so as to be proportional to the idle request torque TRQIDL. “KTAC” in Expression (2) is a conversion coefficient set to a predetermined value, and is set to a value corresponding to a state where the ignition timing is set to the optimal ignition timing. Note that the conversion coefficient KTAC may be changed according to the engine speed NE.
GACTMP = KTAC × TRQIDL (2)

  In step S14, the torque reduction rate KTRQDN is set to “1.0”. In step S15, the initialization flag FINI is set to “1”, and the value of the operation counter CRP is set to “0”. When the initialization flag FINI is set to “1”, the process immediately proceeds from step S12 to step S16.

In step S16, the torque reduction rate KTRQDN is applied to the following equation (3) to update the temporary target intake air flow rate GACTMP.
GACTMP = GACTMP / KTRQDN (3)

In step S17, the temporary target intake air flow rate GACTMP is applied to the following equation (4) to calculate the temporary target intake pressure PBCTMP. In the present embodiment, in the idle state, the lift amount LFT of the intake valve is fixed to a predetermined idle lift amount LFTIDL (for example, 1 mm), so the intake pressure PBA is substantially proportional to the intake air flow rate. Therefore, the temporary target intake pressure PBCTMP as the intake pressure corresponding to the temporary target intake air flow rate GACTMP is calculated from the equation (4). KGP in Equation (4) is a conversion coefficient set to a predetermined value. However, when the temporary target intake pressure PBCTMP calculated by the equation (4) exceeds the upper limit value PBLH (for example, a pressure lower by about 13.3 kPa than the atmospheric pressure PA), the upper limit value PBLH is set.
PBCTMP = KGP × GACTMP (4)

  In step S18, a temporary margin amount DIGTMP is calculated according to the temporary target intake pressure PBCTMP. Specifically, the control width definition amount DIGCTL is calculated by searching the table shown in FIG. 8 according to the temporary target intake pressure PBCTMP, and the provisional margin amount is obtained by adding the non-linear region DIGNL to the control width definition amount DIGCTL. DIGTMP is calculated.

  In step S19, a torque reduction rate KTRQDN is calculated according to the provisional margin amount DIGTMP. Specifically, the torque reduction rate KTRQDN corresponds to the torque ratio η shown on the vertical axis of FIG. 5A, and therefore, using the characteristics shown in FIG. 5, the temporary margin amount DIGTMP is retarded from the optimal ignition timing MBT. A torque ratio η with respect to the ignition timing is calculated as a torque reduction rate KTRQDN.

  In step S20, it is determined whether or not the value of the operation counter CRP is equal to a predetermined value CRPH (for example, 10). At first, this answer is negative (NO), so that the difference between the previous value KTRQDN (n-1) and the current value KTRQDN (n) of the torque reduction rate is less than or equal to a predetermined threshold value DTRTH (a predetermined value close to “0”). It is determined whether or not there is (step S21). Since this answer is negative (NO) at first, the process proceeds to step S22, the value of the operation counter CRP is incremented by “1”, and this process is terminated.

  Thereafter, unless the idle request torque TRQIDL is changed, steps S16 to S21 are repeatedly executed. As a result, the torque reduction rate KTRQDN gradually decreases and converges to a value, and the temporary target intake pressure PBCTMP also converges to a value. Accordingly, the answer to step S21 is affirmative (YES), and the target intake pressure PBACMD is set to the temporary target intake pressure PBCTMP at that time (step S23). Similarly, step S23 is executed when the answer to step S20 becomes affirmative (YES) before the answer to step S21 becomes affirmative (YES).

  FIG. 11 is a diagram for explaining the processing of FIG. 10, and a broken line L31 shows the relationship between the output torque and the intake pressure PBA when the ignition timing is set to the optimal ignition timing MBT. The initially calculated temporary target intake pressure PBCTMP corresponds to the point P01, and the point P1 corresponds to a state in which the center value of the ignition timing is retarded by the temporary margin amount DIGTMP from the optimal ignition timing MBT. By applying the torque reduction rate KTQDN corresponding to this state to the equation (3), the temporary target intake air flow rate GACTMP is updated to a value corresponding to the point P02. In this state, the temporary target intake pressure PBCTMP1 and the temporary margin amount DIGTMP are calculated again, and the torque reduction rate KTQDN (a value corresponding to the point P2) is calculated by retarding the temporary ignition amount MBGTMP from the optimal ignition timing MBT. By applying the calculated torque reduction rate KTQDN to the equation (3), the temporary target intake air flow rate GACTMP corresponding to the point P03 is obtained. Thereafter, the same process is repeated. In FIG. 11, when the value of the calculation counter CRP is “4”, the answer to step S21 is affirmative (YES), and the temporary target intake pressure PBCTMP (intake pressure corresponding to the point P4) at that time is the target intake pressure. Adopted as atmospheric pressure PBACMD.

  As described above in detail, in the present embodiment, the ignition timing margin amount DIGCNT is calculated according to the detected intake pressure PBA, and the ignition timing that is retarded by the margin amount DIGCNT from the optimal ignition timing MBT is the optimal central ignition timing. Calculated as IGCMBT, the control center ignition timing IGCNT is set to the optimum center ignition timing IGCMBT. Then, in the idling state of the engine 1, the feedback correction amount IGFB is calculated so that the engine speed NE matches the target idle speed NEOBJ, and feedback using the feedback correction amount IGFB is performed around the control center ignition timing IGCNT. Is called. Accordingly, since the ignition timing is changed around the retarded ignition timing by the margin amount DIGCNT from the optimal ignition timing MBT, sufficient control response of the engine output torque is ensured, and the engine speed NE is set to the target speed. NEOBJ can be stably maintained.

  Further, a control width definition amount DIGCTL indicating the variable range of the feedback correction amount IGFB is calculated, and the ignition timing retarded by the control width definition amount DIGCTL from the limit ignition timing IGKNOCK, which is an ignition timing at which the possibility of occurrence of knocking is increased. When the knock limit dependent ignition timing IGCKNK is calculated and when the knock limit dependent ignition timing IGCKNK is on the retard side of the optimum center ignition timing IGCMBT, the control center ignition timing IGCNT is set to the knock limit dependent ignition timing IGCKNK. Even in an engine idle state, the intake pressure PBA may be controlled to be relatively high. In such a state, the knock limit dependent ignition timing IGCKNK is retarded from the optimum center ignition timing IGCMBT. Therefore, by setting the control center ignition timing IGCNT to the knock limit dependent ignition timing IGCKNK, knocking can be reliably prevented while ensuring control response of the engine output torque.

  Further, the target opening THCMD of the throttle valve is calculated so that the detected intake pressure PBA coincides with the target intake pressure PBACMD, and the temporary target intake air flow rate GACTMP is calculated according to the target torque TRQIDL in the engine idle state. Further, step S17 for calculating the temporary target intake pressure PBCTMP according to the temporary target intake air flow rate GACTMP, step S18 for calculating the temporary margin amount DIGTMP according to the temporary target intake pressure PBCTMP, and the torque reduction rate KTRQDN according to the temporary margin amount DIGTMP. Step S19, and step S16 of updating the temporary target intake air flow rate GACTMP by dividing the temporary target intake air flow rate GACTMP by the torque reduction rate KTRQDN are repeatedly executed, and the target intake pressure PBACMD is the current value of the reduction rate KTRQDN. The temporary target intake pressure PBCTMP at the time when the difference between the value and the previous value becomes equal to or less than the predetermined threshold value DTRTH is set. When calculating the target intake pressure according to the target intake air flow rate and controlling the intake air flow rate so that the detected intake pressure matches the target intake pressure, the intake pressure changes due to the change in the intake air flow rate, The margin amount DIGCNT also changes. As a result, the torque reduction rate KTRQDN when the control center ignition timing IGCNT is set to the ignition timing retarded from the optimal ignition timing MBT changes, and it is necessary to change the target intake air flow rate. When repeated, the torque reduction rate KTRQDN converges to a constant value. Therefore, by adopting the temporary target intake pressure PBCTMP at the time when the torque reduction rate KTRQDN converges as the target intake pressure PBACMD, it is possible to prevent instability of control due to mutual interference between the intake air flow rate control and the ignition timing control, and the idle state The engine speed NE at can be further stabilized.

  Further, since the intake valve lift amount LFT is maintained at the predetermined idle lift amount LFTIDL in the engine idle state, there is no mutual interference between the intake valve lift amount control and the intake air flow rate control by the throttle valve opening control, The engine speed NE in the idle state can be stabilized.

  In the present embodiment, the intake pressure sensor 8 and the crank angle position sensor 11 correspond to intake pressure detection means and rotation speed detection means, respectively, and the throttle valve 3, actuator 7 and ECU 5 constitute intake air flow rate control means, and the first The valve operating characteristic variable mechanism 41, the motor 43, and the ECU 5 constitute a lift amount control means. The ECU 5 includes an ignition timing control means, a margin amount calculation means, an optimal ignition timing calculation means, a control center ignition timing setting means, a feedback correction amount calculation means, a limit ignition timing calculation means, a control width definition amount calculation means, and a target intake pressure. Configure setting means. Specifically, the module shown in FIG. 6 corresponds to the ignition timing control means, the control width definition amount calculation unit 72 in FIG. 6 corresponds to the control width definition amount calculation means, and the control width definition amount calculation unit 72 and the addition unit. 74 corresponds to a margin calculation means, the optimal ignition timing calculation section 71 corresponds to an optimal ignition timing calculation means, the subtraction sections 75 and 76, and the selection section 77 correspond to a control center ignition timing setting means, and a feedback control section. 78 corresponds to feedback correction amount calculation means, and knock limit ignition timing calculation unit 73 corresponds to limit ignition timing calculation means. 10 corresponds to the target intake pressure setting means, and the target intake air flow rate calculation unit 82, the target lift amount calculation unit 83, and the angle command value calculation unit 84 of FIG. 9 correspond to the lift amount control unit, and the target throttle The valve opening calculation unit 86 corresponds to intake air flow rate control means.

  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 engine control device including the first valve operating characteristic variable mechanism that continuously changes the lift amount of the intake valve is shown. However, the present invention is a general fixed cam that opens and closes the intake valve. The present invention can also be applied to a driving engine.

  In the above-described embodiment, the map value MBTM of the optimal ignition timing MBT and the map value IGKNOCKM of the knock limit ignition timing IGKNOCK are corrected according to the intake air temperature TA and the cooling water temperature TW, and the optimum ignition timing MBT and knock limit ignition timing IGKNOCK are corrected. However, the map values MBTM and IGKNOCKM may be used as they are as the optimum ignition timing MBT and knock limit ignition timing IGKNOCK without correction.

  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.

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 figure 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 valve operation characteristic of an intake valve. It is a figure for demonstrating an ignition timing control method. It is a block diagram of the module which performs ignition timing control. It is a figure which shows the example of a setting of the map applied to calculation of optimal ignition timing (MBT) and knock limit ignition timing (IGKNOCK). It is a figure which shows the table used for the calculation in the control width definition amount calculation part shown in FIG. It is a block diagram of the module which controls intake air flow rate. It is a flowchart of the process which calculates the target intake pressure (PBACMD) in an idle state. It is a figure for demonstrating the process of FIG.

1 Internal combustion engine 3 Throttle valve (intake air flow rate control means)
5 Electronic control unit (ignition timing control means, margin amount calculation means, optimum ignition timing calculation means, control center ignition timing setting means, feedback correction amount calculation means, limit ignition timing calculation means, control width definition amount calculation means, target intake pressure Setting means, intake air flow rate control means, lift amount control means)
7 Actuator (Intake air flow rate control means)
15 spark plug 41 first valve operating characteristic variable mechanism (lift amount control means)
43 Motor (lift amount control means)

Claims (3)

In a control device for an internal combustion engine comprising ignition timing control means for controlling the ignition timing of the internal combustion engine,
An intake pressure detecting means for detecting an intake pressure of the engine;
A rotational speed detecting means for detecting the rotational speed of the engine;
Margin amount calculating means for calculating an ignition timing margin amount according to the intake pressure;
Optimal ignition timing calculating means for calculating an optimal ignition timing that maximizes the output torque of the engine according to the rotational speed and the intake pressure;
Control center ignition timing setting means for calculating an ignition timing that is retarded by the ignition timing margin amount from the optimal ignition timing as an optimal central ignition timing, and setting a control central ignition timing to the optimal central ignition timing;
Feedback correction amount calculation means for calculating a feedback correction amount of the ignition timing so as to make the rotation speed coincide with the idle target rotation speed ;
Limit ignition timing calculating means for calculating a limit ignition timing, which is an ignition timing at which knocking is likely to occur in the engine, according to the rotational speed and the intake pressure ;
The margin amount calculation means includes control width definition amount calculation means for calculating a control width definition amount indicating a variable range of the feedback correction amount,
The control center ignition timing setting means calculates an ignition timing retarded by the control width definition amount from the limit ignition timing as a knock limit dependent ignition timing, and the knock limit dependent ignition timing is later than the optimum center ignition timing. When it is on the corner side, the control center ignition timing is set to the knock limit dependent ignition timing,
The control apparatus for an internal combustion engine, wherein the ignition timing control means controls the ignition timing using the control center ignition timing and a feedback correction amount in an idle state of the engine. Intake air flow rate control means for controlling the intake air flow rate of the engine;
A target intake pressure setting means for setting a target intake pressure of the engine;
The intake air flow rate control means controls the intake air flow rate so that the detected intake pressure coincides with the target intake pressure;
The target intake pressure setting means includes temporary target intake air flow rate calculation means for calculating a temporary target intake air flow rate according to a target torque in an idle state of the engine,
A first step of calculating a temporary target intake pressure according to the temporary target intake air flow rate;
A second step of calculating a provisional ignition timing margin according to the provisional target intake pressure;
A third step of calculating a reduction rate of the engine output torque according to the temporary ignition timing margin; and a step of updating the temporary target intake air flow rate by dividing the temporary target intake air flow rate by the reduction rate. repeatedly perform the four steps, the target intake pressure, to claim 1 in which the difference between the present value and the previous value of the reduction rate and sets the tentative target intake pressure when it becomes less than a predetermined threshold value The internal combustion engine control device described. The engine includes a valve operating characteristic variable mechanism that continuously changes the lift amount of the intake valve,
A lift amount control means for controlling the lift amount of the intake valve via the valve operating characteristic variable mechanism is further provided, and the lift amount control means holds the lift amount at a predetermined low lift amount in an idle state of the engine. The control apparatus for an internal combustion engine according to claim 2 .

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