JP2011179357A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, which executes learning of a reference value of a lift amount sensor output detecting an intake valve lift amount at relatively high frequency to maintain a high lift amount control accuracy. <P>SOLUTION: By an output value of a MOT angle sensor while operation of a control shaft 56 (and a motor 43) is restricted by a fully-closed stopper or a fully-opened stopper, learning of a reference MOT angle θZERO is executed. The learning is executed during fuel cut operation stopping fuel supply to an engine 1. As a motor drive direction in execution of learning, a direction, in which the difference between a lift amount lower limit command value ALCMDMIN as a lift amount set just after completion of fuel cut operation and a maximum lift amount LFTMAX or a minimum lift amount LFTMIN which is a lift amount when the learning is completed becomes small, is selected. The motor 43 is driven in the selected direction, when the learning of the reference MOT angle θZERO is executed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine including a valve operation characteristic variable mechanism that continuously changes a lift amount of an intake valve, and particularly learns a reference value of a lift amount sensor output that detects a lift amount, and learns a reference value It is related with what performs lift amount control using.

  Patent Document 1 discloses an internal combustion engine control device including a valve operating mechanism that continuously changes a lift amount. According to this device, the control shaft used to change the lift amount is driven to a position corresponding to the fully closed state of the intake valve by controlling the rotational speed to the target value, and the lift amount sensor at that time Are learned as reference values.

JP 2009-36034 A

  Although the reference value learned by the method disclosed in Patent Document 1 is stored in the memory, the stored reference value is lost when the power for holding the stored contents of the memory is temporarily turned off. Is called. Therefore, it is necessary to quickly perform the learning of the reference value again. However, since the method disclosed in Patent Document 1 can be performed only while the engine is stopped, the learning may not be performed immediately as necessary. is there. Therefore, the control error of the intake valve lift amount increases, which may adversely affect engine operability.

  The present invention has been made paying attention to this point, and makes it possible to execute the learning of the reference value of the lift amount sensor output for detecting the intake valve lift amount at a relatively high frequency and maintain the lift amount control accuracy. An object of the present invention is to provide a control device for an internal combustion engine.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a variable valve operating characteristic mechanism (41) for continuously changing a lift amount of an intake valve of an internal combustion engine, and driving the variable valve operating characteristic mechanism (41). In the control device for an internal combustion engine comprising the actuator (43) for performing the above operation, the lift amount sensor (72) for detecting the lift amount of the intake valve and the actuator based on the lift amount detected by the lift amount sensor (72) (43) control means, regulation means for regulating the operation of the actuator at a regulation position corresponding to at least one of the maximum value (LFTMMAX) and the minimum value (LFTMIN) of the lift amount, and the regulation means According to the output values (θMOTFO, θMOTS) of the lift amount sensor in a state where the operation of the actuator is restricted, the lift amount sensor is set. Learning means for learning a sensor output reference value (θZERO), wherein the learning means performs the learning during a fuel cut operation for stopping fuel supply to the engine.

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the restricting means restricts the operation of the actuator at a lower limit restricting position corresponding to a minimum value (LFTMIN) of the lift amount. Lower limit restricting means, and upper limit restricting means for restricting the operation of the actuator at an upper limit restricting position corresponding to the maximum value (LFTMAX) of the lift amount, and the control means includes the lower limit restricting position and the upper limit restricting position. Of these, there is provided a restriction position selection means for selecting a restriction position with a smaller difference between the lift amount (ALCMDMIN) set immediately after the end of the fuel cut operation and the lift amount (LFTMMIN, LFTMAX) at the end of learning. When learning is performed by the learning means, the actuator (43) is moved in the direction of the restriction position selected by the restriction position selection means. And drives the.

According to a third aspect of the present invention, in the control device for an internal combustion engine according to the second aspect, the lift amount (ALCMDMIN) set immediately after the end of the fuel cut operation is a lower limit control value of the lift amount, The lower limit control value is set to a lift amount capable of suppressing self-ignition of the air-fuel mixture combusted in the engine.
Here, “self-ignition” means that the air-fuel mixture in the combustion chamber ignites at a time other than the ignition timing by the spark plug.

  According to the first aspect of the invention, the reference value of the lift amount sensor output is learned in accordance with the output value of the lift amount sensor in a state where the operation of the actuator is restricted by the restricting means, and the learning is sent to the engine. This is performed during the fuel cut operation in which the fuel supply is stopped. Since fuel cut operation is performed at a relatively high frequency during engine operation, when the stored value of the reference value is lost, learning of the reference value of the lift sensor output is executed early, and the lift control accuracy is improved. Can be maintained.

  According to the second aspect of the present invention, the lower limit restricting position and the upper limit restricting position have the restricting position where the difference between the lift amount set immediately after the end of the fuel cut operation and the lift amount being learned is small. When selected and learning the lift amount sensor output reference value, the actuator is driven in the direction of the selected restriction position. Therefore, the amount of change in the lift amount after learning is performed during the fuel cut operation becomes small, and the lift amount can be changed quickly and smoothly.

  According to the third aspect of the present invention, the intake valve lift amount is controlled to the lower limit control value that is a lift amount capable of suppressing self-ignition immediately after the end of the fuel cut operation. Self-ignition can be reliably prevented.

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 which shows the structure of the connection part of a 1st valve action characteristic variable mechanism and a drive motor. It is a flowchart of the process which learns the reference value of a lift amount sensor (MOT angle sensor). It is a figure which shows the map and table which are referred by the process of FIG. It is a flowchart of the reference value loss determination process performed by the process of FIG. It is a flowchart of the full-close / full-open determination process performed by the process of FIG. It is a figure which shows the table referred by the process of FIG. It is a time chart for demonstrating fully closed position learning. It is a flowchart of the process which performs fully closed position learning. It is a flowchart of the process which performs a full open position learning.

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 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.

  An intake air flow rate sensor 13 for detecting the intake air flow rate GAIR is provided upstream of the throttle valve. 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”) 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 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 (minimum lift amount LFTMIN (eg, 0.6 mm)). 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, 13.3 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.
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. Hereinafter, “CAIN” is referred to as an intake valve operation phase.

  The driving force of the motor 43 is transmitted from the motor output shaft 43a to the control shaft 56 via the transmission mechanism 71, as shown in FIG. The motor output shaft 43 a is provided with a motor output shaft rotation angle sensor (hereinafter referred to as “MOT angle sensor”) 72 for detecting the rotation angle (hereinafter referred to as “MOT angle”) θMOT of the shaft 43 a. The signal is supplied to the ECU 5. For example, a resolver is used as the MOT angle sensor 72.

The relationship between the MOT angle θMOT and the rotation angle (hereinafter referred to as “CS angle”) θCS of the control shaft 56 is expressed by the following equation (1). RD in Expression (1) is a reduction ratio of the transmission mechanism 71, and θZERO is a reference MOT angle corresponding to a state where the lift amount LFT is the minimum lift amount LFTMIN. A method for calculating the reference MOT angle θZERO will be described later.
θCS = (θMOT + θZERO) / RD (1)

  In the present embodiment, the CS angle θCS calculated by Expression (1) is used as a parameter indicating the lift amount LFT. Therefore, the MOT angle sensor 72 comes to the lift amount sensor.

  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, a drive signal is supplied to the actuator 7, the fuel injection valve 6, the motor 43, the electromagnetic valve 44, and a spark plug (not shown). It consists of an output circuit and the like.

  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.

  In intake valve lift amount control, the intake valve lift amount command value LFTCMD is calculated according to the engine operating state, the CS angle command value θCSCMD is calculated according to the lift amount command value LFTCMD, and the detected MOT angle θMOT is detected. The feedback control of the drive current IMD of the motor 43 is performed such that the CS angle θCS obtained from (1) matches the CS angle command value θCSCMD.

FIG. 6 is a flowchart of the learning process of the reference MOT angle θZERO. This process is executed every predetermined time by the CPU of the ECU 5.
In step S11, an estimated lift amount LIFTHAT is calculated according to the engine operating state. Specifically, one or two lift amount maps (an example shown in FIG. 7A) set in accordance with the engine speed NE and the intake valve operating phase CAIN are selected, and the gauge pressure PBGA is selected. This lift amount map is searched according to (= PBA−PA) and the cylinder intake air amount GAIRCYL, and the estimated lift amount LIFTHAT is calculated by performing an interpolation operation as appropriate.

  The lift amount map is a map in which the relationship between the actual lift amount LFT, the gauge pressure PBGA, and the cylinder intake air amount GAIRCYL is set, and each curve shown in FIG. 7A corresponds to the predetermined gauge pressures PBGA1 to PBGA5. The predetermined gauge pressures PBGA1 to PBGA5 satisfy the relationship PBGA1 <PBGA2 <PBGA3 <PBGA4 <PBGA5. The cylinder intake air amount GAIRCYL is calculated by converting the detected intake air flow rate GAIR into an intake air amount per TDC pulse generation period in accordance with the engine speed NE.

  In step S12, the θCS-LFT table shown in FIG. 7B is searched according to the estimated lift amount LIFTHAT, and the estimated CS angle θCSHAT is calculated. As shown in FIG. 7B, the lift amount LFT increases substantially linearly as the CS angle θCS increases.

In step S13, the estimated CS angle θCSHAT is applied to the following equation (2) to calculate the estimated MOT angle θMOTHAT. In equation (2), RD is the reduction ratio, and θZERO is the current stored value of the reference MOT angle.
θMOTHAT = θCSHAT × RD−θZERO (2)

In step S14, the reference value disappearance determination process shown in FIG. 8 is executed.
In step S31 of FIG. 8, the detected MOT angle θMOT is read. In step S32, it is determined whether or not the absolute value of the difference between the estimated MOT angle θMOTHAT and the MOT angle θMOT is greater than or equal to a determination threshold value DθTH (for example, 1 deg). To do.

  If the answer to step S32 is affirmative (YES), it is determined that the stored value of the reference MOT angle θZERO has disappeared, and the disappearance flag FLST is set to “1” (step S33). If the answer to step S32 is negative (NO), it is determined that the stored value of the reference MOT angle θZERO is normally held, and the disappearance flag FLST is set to “0” (step S34).

  Returning to FIG. 6, in step S15, it is determined whether or not the disappearance flag FLST is “1”. If this answer is negative (NO), learning of the reference MOT angle θZERO is unnecessary, and the processing is immediately terminated.

  If the answer to step S15 is affirmative (YES), it is determined whether or not a fuel cut flag FFC is “1” (step S16). The fuel cut flag FFC is set to “1” when the fuel cut operation for stopping the fuel supply to the engine 1 is being performed. If the answer to step S16 is negative (NO), the process immediately ends. If the answer is affirmative (YES), that is, if the fuel cut operation is being performed, steps S17 to S20 are executed, and the reference MOT angle θZERO To learn.

  In step S17, the fully closed / fully opened determination process shown in FIG. 9 is executed to determine whether to perform fully closed position learning or fully open position learning. In the process of FIG. 9, when the fully closed position learning is performed, the fully closed position learning flag FLCLS is set to “1”.

  In step S18, it is determined whether or not the fully closed position learning flag FLCLS is “1”. If the answer is affirmative (YES), the fully closed position learning process shown in FIG. 12 is executed (step S19). When the result is negative (NO), the fully open position learning process shown in FIG. 13 is executed (step S20).

FIG. 9 is a flowchart of the fully closed / fully opened determination process executed in step S17 of FIG.
In step S41, it is determined whether or not the rapid warm-up flag FFIR is “1”. The rapid warm-up flag FFIR is set to “1” immediately after the cold start of the engine 1 and is returned to “0” when the warm-up is completed. If the answer to step S41 is affirmative (YES), an idle lower limit value ALIDLLMT, which is a lower limit value of the intake valve lift amount during idle operation, is set to a predetermined value ALCMDFIR (for example, 3 mm) for rapid warm-up (step S42). ). If the answer to step S41 is negative (NO), and the rapid warm-up operation is not being performed, the idle lower limit value ALIDLLMT is set to the minimum lift amount LFTMIN (step S43).

  In step S44, the ALNELMT table shown in FIG. 10A is searched according to the engine speed NE, and the engine speed dependent lower limit value ALNELMT is calculated. The ALNELMT table is set such that the engine speed dependent lower limit value ALNELMT increases as the engine speed NE increases.

  In step S45, the KNE table shown in FIG. 10B is searched according to the engine speed NE, and the rotational speed correction coefficient KNE is calculated. The rotation speed correction coefficient KNE is applied to the calculation of the cooling water temperature dependent lower limit value ALTWLMT and the intake air temperature dependent lower limit value ALTALMT, which will be described below. The KNE table is set so that the rotational speed correction coefficient KNE increases as the engine rotational speed NE decreases, considering that the self-ignition tends to occur as the engine rotational speed NE decreases.

  In step S46, the ALTWLMTB table shown in FIG. 10C is retrieved according to the engine coolant temperature TW, and the basic coolant temperature dependent lower limit value ALTWLMTB is calculated. The ALTWLMTB table is set such that the basic cooling water temperature dependent lower limit value ALTWLMTB increases as the engine cooling water temperature TW increases in a range where the engine cooling water temperature TW is higher than 25 ° C.

  In step S47, the ALTALMTB table shown in FIG. 10 (d) is searched according to the intake air temperature TA to calculate the basic intake air temperature dependent lower limit value ALTALMTB. The ALTALMTB table is set so that the basic intake air temperature dependent lower limit value ALTALMTB increases as the intake air temperature TA increases in a range where the intake air temperature TA is higher than 25 ° C.

In step S48, the basic cooling water temperature dependent lower limit value ALTWLMTB and the rotational speed correction coefficient KNE are applied to the following equation (3) to calculate the cooling water temperature dependent lower limit value ALTWLMT, and the basic intake air temperature dependent lower limit value ALTALMTB and the rotational speed correction. The coefficient KNE is applied to the following equation (4) to calculate the intake air temperature dependent lower limit value ALTALMT.
ALTWLMT = ALTWLMTB × KNE (3)
ALTALMT = ALTALMTB × KNE (4)

  In step S49, the lift amount lower limit command value ALCMDMIN is set to the maximum value among the idle lower limit value ALIDLLMT, the rotational speed dependent lower limit value ALNELMT, the coolant temperature dependent lower limit value ALTWLMT, and the intake air temperature dependent lower limit value ALTALMT. The lift amount lower limit command value ALCMDMIN is set to a lift amount that can suppress self-ignition of the air-fuel mixture in the combustion chamber immediately after the end of the fuel cut operation, and the lift amount command value LFTCMD is set to the lift amount lower limit command immediately after the end of the fuel cut operation. Set to the value ALCMDMIN.

  In step S50, it is determined whether or not the lift amount lower limit command value ALCMDMIN is larger than a predetermined intermediate lift amount LFTID. The predetermined intermediate lift amount LFTID is an average value of the maximum lift amount LFTMAX and the minimum lift amount LFTMIN.

  If the answer to step S50 is negative (NO), the fully closed position learning flag FLCLS is set to “1” (step S51). If ALDDMMIN> LFTMID, the fully closed position learning flag FLCLS is set to “0”. "(Step S52).

  According to the processing shown in FIG. 9, the lift amount (maximum lift amount LFTMAX and the minimum lift amount LFTMIN having a smaller difference from the lift amount lower limit command value ALCMDMIN, which is the lift amount command value immediately after the end of the fuel cut operation, is obtained. The fully closed position learning flag FLCLS is performed so that the MOT angle sensor output reference value is learned in the amount LFTMAX or the minimum lift amount LFTMIN).

  Next, an outline of the fully closed position learning process and the fully open position learning process will be described. In this embodiment, a fully closed stopper and a fully opened stopper are attached to the control shaft 56, and when the control shaft 56 rotates in the valve closing direction and reaches the fully closed angle position, the control shaft 56 stops by the fully closed stopper, When 56 is rotated in the rotational direction and reaches the fully open angle position, it is configured to stop by the fully open stopper.

  Then, the fully closed position learning is performed by updating the reference MOT angle θZERO with a value obtained by adding a negative sign to the sensor output θMOTS of the MOT angle sensor 72 in a state where the control shaft 56 is stopped by the fully closed stopper. Further, the reference MOT angle θZERO is updated with a value obtained by subtracting the change width DRANGE of the MOT angle sensor output from the sensor output θMOTFO of the MOT angle sensor 72 in a state in which the control shaft 56 is stopped by the fully open stopper. Thus, fully open position learning is performed.

  However, if the motor output torque when rotating the control shaft 56 to the fully-closed stopper or fully-opened stopper is too large, the fully-closed stopper or fully-opened stopper may be damaged. There is a risk of stopping before reaching. In order to prevent such a problem, in the present embodiment, feedback control is performed to match the rotation angular velocity (hereinafter referred to as “motor angular velocity”) ωMOT of the motor 43 with the command value ωMOTCMD when the control shaft 56 is rotated. When the deviation Dω between the detected motor angular velocity ωMOT and the command value ωMOTCMD becomes equal to or greater than a predetermined value DωTH, it is determined that the control shaft 56 has reached the fully closed stopper or the fully opened stopper. Thereby, the control shaft 56 can be accurately stopped at the fully closed angle position or the fully opened angle position, and the fully closed position learning and the fully opened position learning can be accurately performed.

  FIG. 11 is a time chart for explaining the fully closed position learning process, and the solid line and the broken line in FIG. 11 (a) show the transition of the motor angular velocity ωMOT and the command value ωMOTCMD, respectively. FIGS. 5B and 5C show transitions of the MOT angle θMOT and the output torque TMOT of the motor 43, respectively. When the learning process is started at time t1, the command value ωMOTCMD is set to the predetermined speed ωLRN, and the motor angular speed ωMOT follows the command value ωMOTCMD. When the control shaft 56 reaches the fully closed stopper at time t2, the motor angular velocity ωMOT rapidly decreases and the deviation Dω exceeds the predetermined value DωTH. Therefore, it is determined that the fully closed position has been reached, and the drive of the motor 43 is stopped. The

  The fully open position learning process is performed in the same manner as the fully closed position learning process, except that the rotation direction of the control shaft 56 (the rotation direction of the motor 43) is opposite to the fully closed position learning process.

FIG. 12 is a flowchart of the fully closed position learning process.
In step S61, the motor 43 is driven so that the control shaft 56 rotates in the direction of the fully closed stopper, and feedback control of the motor drive current is performed so that the motor angular velocity ωMOT coincides with the command value ωMOTCMD. The motor angular velocity ωMOT is calculated as a change amount per fixed time of the MOT angle θMOT. For example, when the discretization time k discretized at the execution cycle T of the process of FIG. 12 is used, ωMOT is calculated by the following equation (5).
ωMOT = θMOT (k) −θMOT (k-1) (5)

In step S62, the speed deviation Dω is calculated by the following equation (6).
Dω = | ωMOT−ωMOTCMD | (6)
In step S63, it is determined whether or not the speed deviation Dω is equal to or greater than a predetermined value DωTH. While this answer is negative (NO), it indicates that the control shaft 56 is rotating, so the processing is immediately terminated. When the speed deviation Dω is equal to or greater than the predetermined value DωTH in step S63, it is determined that the control shaft 56 has reached the fully closed stopper, and the reference MOT angle θZERO is set to the fully closed angle position θMOTS that is the MOT angle at that time. A value with a negative sign is set (step S64).

FIG. 13 is a flowchart of the fully open position learning process.
In step S71, the motor 43 is driven so that the control shaft 56 rotates in the direction of the fully open stopper, and feedback control of the motor drive current is performed so that the motor angular velocity ωMOT coincides with the command value ωMOTCMD. At this time, the driving direction of the motor 43 is opposite to the fully opened position learning process. In step S72, the speed deviation Dω is calculated, and then it is determined whether or not the speed deviation Dω is equal to or greater than a predetermined value DωTH (step S73). If the answer is affirmative (YES), that is, if the speed deviation Dω is equal to or greater than the predetermined value DωTH, it is determined that the control shaft 56 has reached the fully open stopper, and the reference MOT angle θZERO is set to the fully open MOT angle. A value obtained by subtracting the change width DRANGE from the angular position θMOTFO is set to a value obtained by adding a negative sign (step S74). As the change width DRANGE, a value set in advance as a difference between the fully closed angle position and the fully opened angle position is applied.

  As described above, according to the processing of FIG. 6, according to the output values θMOTS and θMOTFO of the MOT angle sensor in the state where the operation of the control shaft 56 (and the motor 43) is regulated by the fully closed stopper or the fully opened stopper, the reference MOT Learning of the angle θZERO is performed, and the learning is performed during the fuel cut operation in which the fuel supply to the engine 1 is stopped. Since the fuel cut operation is executed at a relatively high frequency during engine operation, when the reference MOT angle θZERO disappears, learning of the reference MOT angle θZERO can be executed early to maintain the lift amount control accuracy. it can.

  Further, whether the fully closed position learning or the fully open position learning is performed, that is, the motor drive direction at the time of learning execution is the lift amount lower limit command value ALCMDMIN that is a lift amount set immediately after the end of the fuel cut operation, and the learning end The direction in which the difference from the maximum lift amount LFTMAX or the minimum lift amount LFTMIN, which is the lift amount at the time, is reduced is selected, and when learning the reference MOT angle θZERO, the motor 43 is driven in the selected direction. Therefore, the amount of change in the lift amount after learning is performed during the fuel cut operation becomes small, and the lift amount can be changed quickly and smoothly.

  Immediately after the end of the fuel cut operation, the intake valve lift amount is controlled to the lift amount lower limit command value ALCMDMIN, which is a lift amount capable of suppressing self ignition, so that self ignition is reliably prevented immediately after the end of the fuel cut operation. be able to.

  In this embodiment, the MOT angle sensor 72 corresponds to a lift amount sensor, the motor 43 corresponds to an actuator, the fully closed stopper and the fully open stopper of the control shaft 54 correspond to a lower limit restricting means and an upper limit restricting means, respectively, and the ECU 5 Constitutes control means, restriction position selection means, and learning means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, steps S14 to S16 in FIG. 6 may be deleted, and the update of the reference MOT angle θZERO may always be performed when the fuel cut operation is performed regardless of whether or not the reference MOT angle θZERO has disappeared.

  In the above-described embodiment, the MOT angle position sensor 72 is used as the lift amount sensor. However, the present invention is not limited to this, and a control shaft rotation angle sensor that detects the rotation angle (CS angle) θCS of the control shaft 56 is provided. The control shaft rotation angle sensor may be used as a lift amount sensor.

1 Internal combustion engine 5 Electronic control unit (control means, restriction position selection means, learning means)
41 First valve operating characteristic variable mechanism 43 Motor (actuator)
72 Motor output shaft rotation angle sensor (lift amount sensor)

Claims (3)

In a control device for an internal combustion engine, comprising: a valve operation characteristic variable mechanism that continuously changes the lift amount of the intake valve of the internal combustion engine; and an actuator that drives the valve operation characteristic variable mechanism.
A lift amount sensor for detecting a lift amount of the intake valve;
Control means for controlling the actuator based on a lift amount detected by the lift amount sensor;
Restriction means for restricting the operation of the actuator at a restriction position corresponding to at least one of the maximum value and the minimum value of the lift amount;
Learning means for learning a reference value of the lift amount sensor output in accordance with an output value of the lift amount sensor in a state where the operation of the actuator is restricted by the restriction means;
The control device for an internal combustion engine, wherein the learning means performs the learning during a fuel cut operation for stopping fuel supply to the engine. The restricting means restricts operation of the actuator at a lower limit restricting position corresponding to the minimum value of the lift amount, and restricts operation of the actuator at an upper limit restricting position corresponding to the maximum value of the lift amount. Upper limit regulation means,
The control means selects a restriction position in which the difference between the lift amount set immediately after the end of the fuel cut operation and the lift amount at the end of the learning becomes smaller, of the lower limit restriction position and the upper limit restriction position. 2. The internal combustion engine according to claim 1, further comprising a restriction position selection unit, wherein when the learning is performed by the learning unit, the actuator is driven in a direction of the restriction position selected by the restriction position selection unit. Control device.   The lift amount set immediately after the end of the fuel cut operation is a lower limit control value of the lift amount, and the lower limit control value is set to a lift amount capable of suppressing self-ignition of the air-fuel mixture combusting in the engine. The control apparatus for an internal combustion engine according to claim 2.

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