JP2010084715A - Device for controlling fuel injection volume of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine a fuel injection volume in consideration of filling efficiency. <P>SOLUTION: There is provided an internal combustion engine equipped with a variable valve timing mechanism capable of varying a lift amount of an intake valve. A controller for controlling the fuel injection volume detects an actual lift amount of the intake valve and then based on the actual lift amount detected and estimates an intake air volume to calculate an estimated value of the intake air volume. The duration of non-combustive state is counted where no combustion is performed in the internal combustion engine. When the internal combustion engine has made the transition from the non-combustive state to a combustive state where combustion is performed, the controller compares the duration and a given time. Then, if the duration is equal to or more than the given time, the controller corrects the estimated value of the intake air volume. Further, the controller calculates the fuel injection volume based on the estimate value of the intake air volume corrected. As a result, though the filling efficiency varies depending on temperature, the intake air volume can be estimated so as to reflect a change in the filling efficiency. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for controlling a fuel injection amount of an internal combustion engine.

In recent internal combustion engines, it has been proposed that a variable valve mechanism capable of changing the lift amount of the intake valve is mounted and the intake air amount to the internal combustion engine is controlled using the mechanism. Patent Document 1 below discloses a technique for estimating an intake air amount from a lift amount of the mechanism and setting a fuel injection amount according to the intake air amount in an internal combustion engine equipped with such a mechanism.
International Publication No. 97/13063 Pamphlet

  According to the above technique, since the intake air amount is estimated according to the lift amount of the intake valve, a sensor for measuring the intake air amount such as an air flow meter is not required. Further, since the intake air amount corresponding to the operation of the variable valve mechanism is estimated, the intake air amount in accordance with the actual state of the internal combustion engine can be estimated.

  However, even if the volume flow rate of the gas is the same, the density of the gas changes with temperature, so the mass flow rate of the gas changes with temperature. That is, the amount (mass) of intake air that flows into the cylinder and contributes to combustion varies depending on the temperature of the intake air even if the operation characteristics of the intake valve are the same. In general, when the pressure is constant, the density of the gas increases as the temperature decreases. Therefore, as the temperature decreases, the amount of intake air that contributes to combustion increases and the charging efficiency of intake air increases. The above technique does not take into account any change in charging efficiency due to temperature, and there is a risk that the estimation accuracy of the intake air amount will be reduced.

  Accordingly, one object of the present invention is to improve the estimation accuracy of the intake air amount in consideration of the change in the intake charging efficiency due to the temperature.

  According to one aspect of the present invention, in an internal combustion engine having a variable valve mechanism that can change the lift amount of the intake valve, the control device for controlling the fuel injection amount is a means for detecting the actual lift amount of the intake valve. And an intake air amount estimating means for estimating an intake air amount supplied to the internal combustion engine based on the detected actual lift amount and calculating an estimated intake air amount, and a non-combustion state in which combustion is not performed in the internal combustion engine When the counting means for counting the duration and the internal combustion engine shifts from the non-combustion state to a combustion state in which combustion is performed, the duration is compared with a predetermined time, and the duration is equal to or longer than the predetermined time Includes a correcting means for correcting the estimated intake air amount and a means for calculating the fuel injection amount based on the corrected estimated intake air amount.

  Depending on the duration of the non-combustion state, the temperature when the internal combustion engine transitions from the non-combustion state to the combustion state changes, so that the intake charging efficiency also changes. According to the present invention, the intake air amount estimated value is corrected in accordance with the duration when the vehicle is in the non-combustion state, so the intake air amount reflecting the change in charging efficiency can be estimated. Since the estimation accuracy of the intake air amount can be improved, the fuel injection amount can be calculated more accurately.

  According to one embodiment of the present invention, it further comprises means for counting an elapsed time from when the internal combustion engine has shifted to the combustion state, and the correction means is configured to estimate the intake air amount as the elapsed time increases. Correction is performed so that becomes smaller.

  According to one embodiment of the present invention, means for feedback-controlling the detected actual lift amount at a predetermined control period so as to converge the detected actual lift amount to the target lift amount with a predetermined time constant, the target lift amount and the actual lift amount Is a predicted value calculation means for calculating a predicted value of the lift amount in the next control cycle by adding a value obtained by multiplying the difference between the two by a predetermined gain to the actual lift amount. And a predicted value calculation means that is calculated based on the length and the time constant.

  Other features and advantages of the present invention will be apparent from the detailed description that follows.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as an engine) and its control device according to an embodiment of the present invention.

  An electronic control unit (hereinafter referred to as “ECU”) 1 is a computer including a central processing unit (CPU) and a memory. The memory can store a computer program for realizing various controls of the vehicle and data (including a map) necessary for executing the program. The ECU 1 receives a signal from each part of the vehicle and performs an operation according to data and a program stored in the memory to generate a control signal for controlling each part of the vehicle.

  The engine 2 is an engine having, for example, four cylinders. An intake pipe 3 and an exhaust pipe 4 are connected to the engine 2. The intake pipe 4 is provided with a throttle valve 5. The opening degree of the throttle valve 5 is controlled in accordance with a control signal from the ECU 1. By controlling the opening degree of the throttle valve 5, the amount of air taken into the engine 2 can be controlled. A throttle valve opening (θTH) sensor 6 for detecting the opening of the throttle valve is connected to the throttle valve 5, and this detected value is sent to the ECU 1.

  A fuel injection valve 7 is provided for each cylinder between the engine 2 and the throttle valve 5 and slightly upstream of the intake valve (not shown) of the engine 2. The fuel injection valve 7 is connected to a fuel pump (not shown). The fuel injection timing and the fuel injection amount of the fuel injection valve 7 are changed according to a control signal from the ECU 1. Alternatively, the fuel injection valve may be attached so as to face the cylinder of the engine 2.

  An intake pipe absolute pressure (PBA) sensor 10 is provided downstream of the throttle valve 5 to detect the pressure in the intake pipe. An intake air temperature (TA) sensor 11 is provided downstream of the intake pipe absolute pressure sensor 10 to detect the temperature in the intake pipe. These detected values are sent to the ECU 1. The engine 2 is provided with an engine water temperature sensor 12 for detecting the engine water temperature TW, and the detected value of the sensor is sent to the ECU 1.

  The engine 2 includes a first mechanism 21 (described later with reference to FIG. 2) capable of continuously changing the lift amount and opening angle (opening period) of the intake valve and the exhaust valve, and an intake valve. And a second mechanism 22 (described later with reference to FIG. 2) that continuously changes the phase with respect to the crankshaft of the cam that drives the valve. The phase of the cam that drives the intake valve is changed by the second mechanism 22, and thus the phase of the intake valve is changed.

  The ECU 1 is connected with a crank angle sensor 13 that detects the rotation angle of the crankshaft of the engine 1 and a cam angle sensor 14 that detects the rotation angle of the camshaft to which the cam that drives the intake valve of the engine 1 is coupled. The detection values of these sensors are supplied to the ECU 1. The crank angle sensor 13 generates one pulse (CRK signal) every predetermined crank angle (for example, 30 degrees), and can specify the rotational angle position of the crankshaft by the pulse. The cam angle sensor 14 generates a pulse (CYL signal) at a predetermined crank angle position of a specific cylinder of the engine 2 and a pulse (TDC signal) at the top dead center (TDC) at the start of the intake stroke of each cylinder. . These pulses are used for detection of various control timings such as fuel injection timing and ignition timing, and engine speed NE. The actual phase of the cam shaft of the intake valve is detected from the relative relationship between the TDC signal output from the cam angle sensor 14 and the CRK signal output from the crank angle sensor 13.

  The valve operating characteristic variable device 20 is provided with a control shaft rotation angle sensor (CSA) sensor 15 for detecting the rotation angle position of the control shaft for controlling the lift amount of the intake valve.

  The ECU 1 detects the operating state of the engine 2 in accordance with programs and data (including a map) stored in the memory in accordance with input signals from the various sensors, and controls the throttle valve 5, the fuel injection valve 7, and the valve operation. A control signal for controlling the characteristic variable device 20 is generated.

  FIG. 2 shows a more specific configuration diagram of the valve operation characteristic variable device 20. As shown in the figure, the variable valve operating characteristic device 20 includes a first mechanism 21 that can continuously change the lift amount and opening angle (hereinafter simply referred to as lift amount) of the intake valve, A second mechanism 22 capable of continuously changing the phase, an actuator 24 including a motor 23 for continuously changing the lift amount of the intake valve via the first mechanism 21, and the second In order to continuously change the phase of the intake valve via the mechanism 22, an actuator 26 having an electromagnetic valve 25 whose opening degree can be changed continuously is provided.

  As a parameter indicating the phase of the intake valve, the cam axis phase CAIN of the intake valve is used. Lubricating oil in the oil pan 28 is pressurized and supplied to the solenoid valve 25 by the oil pump 27. The motor 23 and the electromagnetic valve 25 operate according to a control signal from the ECU 1. A more specific configuration of the second mechanism 22 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-227013.

  The first mechanism 21 will be described with reference to FIG. As shown to (a), the cam shaft 31 provided with the cam 32, the control arm 35 supported by the cylinder head so that rocking is possible centering on the shaft 35a, and the control cam 37 which rocks the control arm 35 are provided. The control shaft 36 provided and the control arm 35 are supported so as to be swingable via a support shaft 33b. The sub cam 33 swings when the cam 32 is driven. The sub cam 33 is driven and the intake valve 40 is moved. And a rocker arm 34 to be driven. The rocker arm 34 is swingably supported in the control arm 35.

  The sub cam 33 has a roller 33 a that contacts the cam 32, and swings about the shaft 33 b as the cam shaft 31 rotates. The rocker arm 34 has a roller 34a that contacts the sub cam 33, and the movement of the sub cam 33 is transmitted to the rocker arm 34 via the roller 34a.

  The control arm 35 includes a roller 35b that contacts the control cam 37, and swings about the shaft 35a by the rotation of the control shaft 36. In the state shown in (a), since the movement of the sub cam 33 is hardly transmitted to the rocker arm 34, the intake valve 40 is maintained in a substantially fully closed state. In the state shown in (b), the movement of the sub cam 33 is transmitted to the intake valve 40 via the rocker arm 34, and the intake valve 40 opens to the maximum lift amount LFTMAX (for example, 12 mm).

  Therefore, the control shaft 36 is connected to the output shaft of the motor 23 (FIG. 2) of the actuator 24 through a gear, and the control shaft 36 is rotated by the motor 23, thereby continuously increasing the lift amount of the intake valve 40. Can be changed. In this embodiment, the first mechanism 21 is provided with a CSA sensor 15 (FIG. 1) for detecting the rotation angle position of the control shaft 36, and the detected rotation angle position CSA is a parameter indicating the lift amount. Used as. A more detailed configuration of the first mechanism 21 is shown in a patent application (Japanese Patent Application No. 2006-197254) filed by the present applicant.

  It should be noted that the present invention is not limited to the first mechanism 21 as shown in the figure, and a mechanism capable of variably controlling the lift amount of the intake valve can be realized by any appropriate means. I want. In the above example, the first mechanism 21 changes not only the lift amount but also the opening angle. However, the present invention can be applied to a mechanism configured to change only the lift amount.

  FIG. 4 is a functional block diagram of an apparatus for controlling the fuel injection amount according to one embodiment of the present invention. The function by each functional block can be realized in the ECU 1.

  The lift amount prediction unit 101 calculates a predicted lift amount HALIFT based on the actual lift amount of the intake valve detected by the CSA sensor 15. More specifically, the lift amount in the next control cycle is predicted as the predicted lift amount HALIFT. A specific method of this prediction will be described later. The intake air amount estimation unit 103 estimates the intake air amount based on the predicted lift amount HALIFT, and calculates an intake air amount estimated value GCYL. Thus, the amount of air taken into the engine is estimated in accordance with the predicted lift amount HALIFT.

  Referring now to FIG. 5, a three-dimensional map representing the relationship between engine speed, intake air amount, and lift amount is shown. The intake air amount (mass) increases as the engine speed increases and the lift amount increases. The map can be stored in advance in the memory of the ECU 1. The intake air amount estimation unit 103 refers to the map based on the detected engine speed and the predicted lift amount HALIFT, and obtains a corresponding intake air amount as an intake air amount estimated value GCYL.

  The correcting unit 105 corrects the intake air amount estimated value GCYL. A specific method of this correction will be described. FIG. 6 shows a time scale. At time t1, the engine shifts from the combustion state to the non-combustion state, and at time t2, the non-combustion state ends. The engine combustion is resumed. Here, the “non-combustion state” means a state in which combustion is not performed because the engine is not operated, and an operation of the engine is performed, but a combustion cycle (in this embodiment, intake air, This includes a state in which combustion does not occur during compression, expansion, and exhaust stroke.

  The duration of the non-combustion state is represented by Toff, and the elapsed time from the transition from the non-combustion state to the combustion state is represented by Ton.

  As an example of the combustion state and the non-combustion state, there are a state where the ignition of the engine is turned on and a state where it is turned off. When the ignition is turned off, the engine is stopped and no combustion takes place. In this case, as shown in FIG. 6A, at time t1, the ignition is turned off to end the previous operation cycle, and at time t2, the ignition is turned on to start the current operation cycle.

  Other examples of the combustion state and the non-combustion state include a state where the fuel cut is released (that is, fuel is supplied) and a state where the fuel cut is being executed. In the combustion cycle in which the fuel cut is being performed, no fuel is supplied into the cylinder, and thus combustion is not performed. In this case, as shown in FIG. 6B, fuel cut is started at time t1, and fuel is not supplied to the engine during time t1 to t2. At time t2, the fuel cut is canceled and fuel supply is resumed.

  The longer the non-burning state duration Toff, the lower the temperature of the intake air. On the other hand, since the mass flow rate of gas is determined based on the density and volume flow rate of the gas, even if the lift amount is the same, as the temperature of the air flowing into the cylinder decreases, the density of the air increases. The amount (mass) of intake air that contributes to combustion increases, and the charging efficiency increases. Since the map (FIG. 5) used for estimating the intake air amount described above is created on the assumption that the non-burning state as described above has not continued for a predetermined time or longer, the non-burning for the predetermined time or longer is not created. If the intake air amount is estimated using this map when the temperature of the intake air is lowered due to the occurrence of a state, the estimated intake air amount may include an error with respect to the actually sucked air amount. Therefore, the correction unit 105 performs correction so as to compensate for this error.

  Specifically, the correction unit 105 measures the non-burning state duration Toff using, for example, a timer. If the duration time Toff is equal to or longer than the predetermined time, it indicates that the charging efficiency of the intake air changes due to the temperature drop of the intake air, and thus correction is performed. The “predetermined time” here is the above-mentioned “predetermined time” on which the above-described map for estimating the intake air amount (FIG. 5) is created, and is set in advance. For example, the duration of the non-combustion state and the change in the actual intake air amount accompanying the non-combustion state can be checked by simulation or the like, and an appropriate “predetermined time” can be determined in advance to perform correction to compensate for the change in charging efficiency it can.

  The correction unit 105 corrects the estimated intake air amount GCYL according to the elapsed time Ton from when the engine shifts from the non-combustion state to the combustion state. The elapsed time Ton is also measured using, for example, a timer. In this embodiment, a map as shown in FIG. 7 is referred to based on the elapsed time Ton, and the corresponding correction coefficient KGCYLMOTST is obtained. The map can be stored in advance in the memory of the ECU 1.

  Since the correction is performed so that the estimated intake air amount is higher in the state where the charging efficiency is higher than the map of FIG. 5, the correction coefficient KGCYLMOTST is set to have a value of 1 or more. Further, the lower the intake air temperature, the higher the intake charging efficiency. Therefore, as the elapsed time Ton is smaller, the correction coefficient KGCYLMOTST is increased, and thus the correction is performed so that the estimated intake air amount GCYL is further increased. The correcting unit 105 multiplies the estimated intake air amount GCYL by the correction coefficient KGCYLMOTST obtained from the map to calculate a corrected estimated intake air amount GCYLF. By this correction, it is possible to calculate an estimated intake air amount that better reflects the charging efficiency of the intake air.

  In this embodiment, as shown in FIG. 7, when the elapsed time Ton exceeds a predetermined time (2 seconds in this embodiment), the correction coefficient KGCYLMOTST is maintained at a predetermined value (for example, 1.0). The The predetermined time is preset by simulation or the like as the time required for the engine to reach a temperature suitable for using the map for estimating the intake air amount (FIG. 5) after starting combustion. Can do.

  As described above, the non-combustion state and the combustion state correspond to the state where the ignition is turned off and the state where the ignition is turned on in one embodiment, and in the other embodiments, the state where the fuel cut is performed and Corresponds to the released state. Specific control flows of these embodiments will be described later.

  The fuel injection amount calculation unit 107 calculates the fuel injection amount based on the corrected estimated intake air amount GCYLF (mass). More specifically, a corresponding fuel injection amount (represented by fuel injection time (ms)) is obtained on the basis of the corrected estimated intake air amount GCYLF with reference to a map as shown in FIG. As the intake air amount increases, the fuel injection amount increases. The map is created so as to realize a desired air-fuel ratio, and can be stored in advance in the memory of the ECU 1. The fuel injection amount thus determined is passed to a fuel controller (not shown) realized by the ECU 1, and the fuel injection valve is driven by the fuel controller so that the fuel injection amount is injected in the next control cycle. The

  Thus, even when a non-combustion state occurs, the estimated intake air amount is calculated in consideration of the charging efficiency of the intake air, so that an amount of fuel more suitable for the actual intake air amount can be supplied.

  If an engine water temperature sensor, an intake air temperature sensor, or the like is used, there may be a time delay, and variations in detection values may increase depending on the location of the sensor. According to the present invention, it is possible to compensate for the change in the intake air amount based on the temperature drop caused by the occurrence of the non-combustion state without using such a temperature sensor. Can be calculated.

  Next, calculation of the predicted lift amount according to an embodiment of the present invention will be described. Here, before describing a specific calculation method by the lift amount prediction unit 101 of FIG. 4, with reference to FIGS. 9 to 13, a controller for controlling the lift amount and a principle of calculation of a predicted value of the lift amount will be described. explain.

  FIG. 9A is a block diagram of a control device for controlling the lift amount of the intake valve according to one embodiment of the present invention. The lift controller 51 is realized in the ECU 1. The plant 52 here includes the first mechanism 21 and the actuator 24 of FIG. The lift controller 51 calculates an operation amount for converging the actual lift amount of the intake valve to the target lift amount according to a control method described later. The motor 23 of the actuator 24 operates the first mechanism 21 according to the operation amount, and changes the lift amount of the intake valve. The changed lift amount is detected by the CSA sensor 15 (FIG. 1) as an actual lift amount and fed back to the lift controller 51.

  FIG. 9B is a diagram for explaining the principle of predictive value calculation according to the present invention. The control of the lift amount and the fuel injection amount is executed according to a predetermined control cycle, and in each control cycle, the target lift amount is determined according to the operating state of the engine (for example, the degree of opening of the accelerator pedal). The figure shows the target lift amount over three control cycles n to (n + 2), the actual lift amount (detected by the CSA sensor 15), and the predicted lift amount calculated according to the method of the present invention for a certain cylinder. Behavior is shown. The length of one control cycle is represented by Stime. In the following embodiments, the control period is realized at fixed time intervals, and thus the length Stime of the control period is constant (for example, 10 milliseconds).

Alternatively, the control cycle may be synchronized with the TDC signal, and control may be executed according to the TDC signal. In this case, the control cycle length Stime can be calculated based on the engine speed. For example, when the TDC signal is output at the top dead center of the intake stroke and the engine speed detected in the current control cycle n is NE (rpm), the length of the control cycle n is calculated as follows: Can be done.

  In each control cycle, the lift controller 51 controls the intake valve with the actual lift amount set to the target lift amount. Referring to the control cycle n, the target lift amount is X (mm), and the actual lift amount is Z (mm). The predicted lift amount calculated based on the target lift amount and the actual lift amount is Y (mm). In the control cycle n, the fuel injection amount to be injected in the next control cycle (n + 1) is determined based on the predicted lift amount. In the control cycle (n + 1), the actual lift amount almost reaches the value Y of the predicted lift amount calculated in the control cycle n. Therefore, an amount of fuel injection suitable for the actual lift amount realized in the cycle (n + 1). A quantity will be injected.

  Thus, since the fuel injection amount is calculated one control cycle before the injection timing, when the fuel injection amount is calculated with the actual lift amount detected in the control cycle n, the control cycle (in which actual injection is performed) There is a possibility that an amount of fuel suitable for the actual lift amount of n + 1) may not be injected. This may cause a deviation of the air-fuel ratio. According to the present invention, since the lift amount after one control cycle is predicted and the fuel injection amount is calculated based on the predicted lift amount, the amount of fuel suitable for the actual lift amount when actual injection is performed is determined. Can be supplied.

The predicted lift amount can be calculated according to the following equation.
HALIFT (n)
= C (ALCMD (n) -ALIFT (n)) + ALIFT (n)
C = control cycle length Stime / (time constant τp + control cycle length Stime)
(1)

  Here, ALIFT (n) indicates the actual lift amount detected in the control cycle n. ALCMD (n) indicates the target lift amount determined in the control cycle n. C is a gain, which is calculated based on the control cycle length Stime and the time constant τp of lift amount control by the lift controller 51. HALIFT (n) indicates the predicted lift amount calculated in the control cycle n. The predicted lift amount is calculated by adding a value obtained by multiplying the deviation between the target lift amount and the actual lift amount by a gain to the actual lift amount.

  In the present invention, the predicted value HALIFT (n) is calculated in the control cycle n according to the above equation (1), and the fuel injection amount to be supplied in the next control cycle (n + 1) is determined according to the predicted value.

  Hereinafter, the basis of the above formula (1) will be described.

  FIG. 10 is a detailed block diagram of the lift controller 51 shown in FIG. In this embodiment, the lift controller 51 employs PD control for position control of the intake valve, that is, control of the lift amount, and employs PI control for speed control, that is, control of the speed for moving the intake valve, thereby calculating the operation amount. . The PD control block is represented by reference numeral 54 and the PI control block is represented by reference numeral 55. Kpp indicates a proportional gain, and Kpd indicates a differential gain. Kvp represents a proportional gain, and Kvi represents an integral gain. 1 / z indicates a delay element. Stime indicates the length of the control cycle as described above.

  In block 54, a term obtained by multiplying the difference between the target lift amount and the actual lift amount by the proportional gain Kpp, and a term obtained by differentiating the difference and multiplying by the inverse of the control period (1 / Stime) and the differential gain Kpd, Is added. In block 55, the difference between the current value of the actual lift amount and the previous value (indicating the amount of change in the lift amount per control cycle) and the output of block 54 are taken, and a proportional gain Kvp is obtained with respect to the difference. And a term obtained by integrating the difference and multiplying by the control period length Stime and the integral gain Kvi.

On the other hand, according to the knowledge of the inventor of the present application, the plant 52 including the first mechanism 21 and the actuator 24 (FIG. 2) receives the voltage U applied to the motor 23 of the actuator 24 as an input, and the resulting second Assuming that the angle θcs of the control shaft 36 of the first mechanism 21 is an output, the equation of motion of the plant 52 can be expressed by a transfer function as shown in Equation (2) using the Laplace operator s.

  Here, Jall indicates an inertia element of the system from the motor 23 to the control shaft 36, and includes the inertia of the motor 23 and the inertia of the control shaft 36. Ball indicates the viscous resistance of the system from the motor 23 to the control shaft 36, and includes the viscous resistance of the motor 23, the viscous resistance and torque constant of the control shaft 36, the resistance of the motor, the reduction ratio, the gear efficiency, and the like.

  FIG. 11A is a block diagram showing the lift controller 51 (FIG. 9A) and the plant 52 by a transfer function using a Laplace operator s. Block 71 represents a PD control block, and block 72 represents a PI control block. A block 73 represents the plant 52, and the above equation (2) is shown.

Here, each gain of PD and PI control is set using a time constant as follows. The time constant τp is a time constant for position control (PD control), and the time constant τω is a time constant for speed control (PI control).
Kpp = 1 / τp
Kpd = τω / τp
Kvp = Jall / τω
Kvi = Ball / τω

  The time constants τp and τω can be set to desired values. In order to realize position control in which the time constant τp is constant, the gains Kpp to Kvi are set so that the combined transfer function of the blocks 71 to 73 is a first-order lag system of a single time constant τp. Here, the constant time constant τp indicates that the time required for the actual lift amount to reach about 63% of the target lift amount is constant.

  Find the combined transfer function of blocks 71-73. When the definitions of the time constants τp and τω are used, FIG. 11A is expressed as shown in FIG.

Next, when the PI control block 72 of FIG. 11B and the transfer function of the plant 73 are synthesized, the transfer function indicated by the block 75 of FIG. 11C is obtained. When the feedback of the Laplace operator s (represented by block 74) is combined with block 75, the transfer function indicated by block 76 in FIG. 12 (a) is obtained. Further, when the block 71 and the block 76 are combined, the transfer function indicated by the block 77 in FIG. 12B is obtained. When the feedback line of the target lift amount is further synthesized from the actual lift amount, the transfer function indicated by the block 78 in FIG. 12C is obtained. Thus, the combined transfer function H of the lift controller 51 and the plant 52 is expressed as the following equation (3). This combined transfer function represents a first-order lag system of time constant τp. Thus, by determining the gains Kpp to Kvi as described above, the time constant τω for speed control is eliminated from the combined transfer function H, and only the time constant τp for position control remains. Thus, as described above, the time constant τp is set to a desired value, and the gains Kpp and Kpd are set based on the τp, so that the lift amount can be controlled so that the time constant τp is constant. .
Composite transfer function H = 1 / (τp · s + 1) (3)

  Next, with reference to FIG. 13, the reason why the above equation (1) is derived from the combined transfer function H of the equation (3) will be described.

A block 78 in FIG. 13A represents the transfer function H of Equation (3). If the block 78 is decomposed for discretization, the blocks 81 and 82 shown in (b) are obtained. Assuming that the length of the control cycle in which the transfer function is executed is Stime, the discrete expression of the integral (1 / s) is 1 / (1-z ⁻¹ ). Can be used. Stime in block 84 represents integration time. Combining blocks 81, 83, and 84 is represented by block 85 shown in (d). Taking Stime / τp as k, a loop transfer function H ′ (z) is obtained (represented by z expression).

When C = k / (1 + k) is set, Expression (4) is expressed as follows.

Expression (5) is expressed as a block 86 in FIG. 13 (e). When this is converted into a difference equation with U as input and Y as output, it is expanded as follows. n represents a control cycle.

  If Y (n) in equation (6) is the predicted lift amount HALIFT (n), Y (n-1) is the actual lift amount ALIFT (n), and U (n) is the target lift amount ALCMD (n). The above equation (1) is derived.

  In this embodiment, the position control is realized by PD control and the speed control is realized by PI control. However, the present invention is not limited to such a control form, and the speed control is not necessarily required. In the present invention, the lift amount control may be any control method that can be expressed by a transfer function. For example, PI control, PD control, PID control, and H∞ control can be used. Moreover, you may include the control by the disturbance observer which controls a plant so that the disturbance to a plant may be estimated and the influence of a disturbance may be removed. Since these control can determine the frequency characteristics (gain characteristics and phase characteristics) of the control according to the control parameters, it can be said that the control is a control technique capable of performing frequency shaping. For example, in PI control, gain characteristics and phase characteristics of the PI control can be determined by control parameters such as proportional gain and integral gain. As described above, in the present invention, the control parameter used for the lift amount control is set using the time constant, so that the combined transfer function of the control system including the plant is expressed by the first-order lag system of the time constant. The present invention can be applied to a control form in which the lift amount can be controlled so that the time constant is constant.

  Next, a detailed method of calculating a predicted value by the lift amount prediction unit 101 in FIG. 4 will be described. FIG. 14 is a more detailed functional block diagram of the lift amount prediction unit 101 of FIG. Preferably, a target lift decimation unit 91 is provided, which obtains the value p by dividing the intake valve ineffective time by the control cycle length Stime. The past value of the target lift amount (target lift amount calculated in the previous control cycle) is stored in the memory of the ECU 1. The control cycle Stime is constant in this embodiment, and the value is stored in the memory of the ECU 1. The decimation unit 91 outputs the target lift amount calculated in the control cycle (np) before p times.

  In the variable lift mechanism (first mechanism 21), an invalid time is generated for the intake valve to transition from the stationary state to the operating state. That is, the lift controller 51 outputs an operation amount for controlling the lift amount of the intake valve in accordance with the target lift amount to the actuator 24 in FIG. 2, but until the intake valve actually starts moving according to the operation amount, There is a delay for the invalid time. Therefore, the decimation process as described above is performed in order to more accurately associate the actual lift amount with the target lift amount.

  For example, if the invalid time is 30 ms and the control cycle is 10 ms, the decimation unit 91 outputs the target lift amount determined in the previous three control cycles (n-3). In this case, the operation start of the current control cycle of the intake valve is based on the target lift amount determined in the previous three control cycles. The invalid time can be calculated in advance by simulation or the like and stored in the memory of the ECU 1 depending on the variable lift mechanism.

  The operation determination unit 92 determines whether or not the intake valve has transitioned from the stationary state to the operating state in the current control cycle n. More specifically, the operation determination unit 92 determines the difference between the actual lift amount detected in the current control cycle n via the CSA sensor 15 and the actual lift amount detected in the previous control cycle (n−1). And the difference is divided by the control period length Stime. The value obtained by the division represents the operating speed of the intake valve. If the operating speed is equal to or higher than a predetermined value, it is determined that the intake valve is in operation, and an operation flag of value 1 is output. If the operating speed is lower than the predetermined value, it is determined that the intake valve is stationary in the previous control cycle, and the intake valve has started operating in the current control cycle, and a zero-valued operation flag is output.

  The switching unit 93 checks the value of the operation flag, and if the value of the operation flag is 1, employs the value of the target lift amount determined in the current control cycle n as the target lift amount ALCMD (n). As described above, the target lift amount can be determined by any known method according to the operating state of the engine. If the value of the operation flag is zero, the value of the target lift amount before p times passed from the decimation unit 91 is adopted as the target lift amount ALCMD (n). Thus, when the intake valve is not in operation but transitions from a stationary state to an operating state, it indicates that an invalid time has occurred, so the target lift amount before p times is used.

  Thus, it can be considered that the invalid time does not substantially occur when the intake valve is in operation. Alternatively, when the intake valve is in operation, there may be a slight dead time in the stricter sense. For example, since the operation amount calculated by the lift controller 51 reaches the actuator 24 via the communication line, such an invalid time may occur. Therefore, the dead time may be taken into account even when the intake valve is in operation. In that case, the invalid time is previously measured through simulation or the like and stored in the memory of the ECU 1, and the decimation unit 91 calculates a value p ′ obtained by dividing the invalid time by the length of the control period, The target lift amount determined in the control cycle before p ′ times is output. The switching unit 93 selects, as the target lift amount ALCMD (n) of the current control cycle, the target lift amount of the control cycle before p ′ times or the target lift amount of the control cycle before p times according to the value of the operation flag. .

  The gain calculation unit 94 calculates the gain C according to the above-described equation (1) based on the control cycle length Stime and the time constant τp. As described above, the time constant τp can be set to a desired value, and can be stored in advance in the memory of the ECU 1.

  The predicted lift calculation unit 95 selects the gain C, the actual lift amount ALIFT (n) detected by the CSA sensor 15 in the current control cycle n, and the switching unit 93 in the current control cycle n in the above equation (1). The calculated target lift amount ALCMD (n) is substituted to calculate the predicted lift amount HALIFT (n).

  In addition, it supplements about the case where the length Stime of a control period is not constant like the case where control is performed according to a TDC signal. First, regarding the calculation of the value of p, in this case, the past value of the time length of the control cycle is stored in the memory of the ECU 1. The decimation unit 91 determines how many control cycles the invalid time corresponds to. For example, when the invalid time is 30 ms, the length of the control cycle (n−1) is 9 ms, the length of (n−2) is 11 ms, and the length of (n−3) is 12 ms, it is invalid. Since the location 30 ms back corresponds to the control period (n-3) (30-9-11-12 becomes zero or less), p = 3 can be obtained. Instead of storing the past value of the control cycle length, the past value of the engine speed may be stored. As described above, the length of the control cycle n can be obtained from the engine speed detected in the control cycle n.

  Further, since the previous actual lift amount is detected according to the previous TDC signal, and the current actual lift amount is detected according to the current TDC signal, the operation determination unit 92 calculates the operation speed. It is preferable to use the length of the previous control cycle (n-1). The gain C is a value for predicting how much the actual lift amount detected according to the current TDC signal changes until the lift amount detection according to the next TDC signal is detected. The unit 94 preferably calculates the gain C using the length Stime of the current control cycle n.

  FIG. 15 is a flowchart of a process for calculating the fuel injection amount according to an embodiment of the present invention. The process is executed by the ECU 1 in accordance with the control cycle described above, and more specifically, is realized by a functional block shown in FIG.

  In step S11, as described above with reference to FIG. 14, the target lift amount p times before is obtained based on the invalid time. If it is determined in step S12 that the intake valve has transitioned from the stationary state to the operating state in the current control cycle by calculating the operating speed of the intake valve, the operation flag is set to zero and the current control cycle is set over the current control cycle. If it is determined that the intake valve is operating, the operating flag is set to 1.

  In step S13, if the operation flag is a value 1 indicating that the intake valve is operating, the target lift amount determined in the current control cycle is set to the target lift amount ALCMD (n) (S14). If the operation flag is zero, which indicates that the intake valve has transitioned from the stationary state to the operating state, the target lift amount determined in the previous control cycle is set to the target lift amount ALCMD (n) ( S15).

  In step S16, the gain C is calculated according to the above-described equation (1) based on the control cycle length Stime and the time constant τp. In step S17, using the gain C, the actual lift amount ALIFT (n) and the target lift amount ALCMD (n) detected by the CSA sensor 15, the predicted lift amount HALIFT (n) is calculated according to the above equation (1). .

  In step S18, based on the engine speed detected in the current control cycle and the predicted lift amount HALIFT (n) value obtained in step S17, a map as shown in FIG. 5 is referred to and the corresponding intake air amount is determined. The intake air amount estimated value GCYL is obtained.

  In step S19, the intake air amount estimated value GCYL obtained in step S18 is corrected to calculate a corrected intake air amount estimated value GCYLF. A detailed flowchart of the correction process will be described later.

  In step S20, based on the intake air amount estimated value GCYLF corrected in step S19, a map as shown in FIG. 8 is referred to find the corresponding fuel injection amount.

  FIG. 16 is a flowchart according to one embodiment of the correction process performed in step S19 of FIG. This flowchart shows a case where the non-combustion state and the combustion state described with reference to FIG. 6A correspond to the state where the ignition is turned off and the state where the ignition is turned on.

  In step S31, it is determined whether or not the duration Toff from when the ignition was turned off last time to when the ignition is turned on this time is equal to or longer than a predetermined time (for example, 30 seconds). If this determination is Yes, the temperature of the engine when the ignition is turned on this time has decreased, indicating that the intake charging efficiency is high. Proceeding to step S32, a corresponding correction coefficient KGCYLMOTST is obtained by referring to a map as shown in FIG. 7 based on the elapsed time Ton from when the ignition is turned on this time. In step S33, the estimated intake air amount GCYL is multiplied by the correction coefficient KGCYLMOTST to calculate a corrected intake air amount estimated value GCYLF. Thus, even when the intake charging efficiency changes due to the non-combustion state in which the ignition is turned off, the intake air amount can be estimated to better reflect the current charging efficiency.

  If the determination in step S31 is No, it can be considered that the engine is in a state where the map as shown in FIG. 5 can be used (that is, the temperature is high). Therefore, in step S34, the estimated intake air amount GCYL is set to GCYLF without correction.

  FIG. 17 is a flowchart according to another embodiment of the correction process performed in step S19 of FIG. In this flowchart, the non-combustion state and the combustion state described with reference to FIG. 6B are in the state where the fuel cut is performed and the state where the fuel cut is released (fuel is supplied). The corresponding case is shown.

  In step S41, it is determined whether the duration Toff from when the fuel cut is started to when it is released is equal to or longer than a predetermined time (for example, 2 seconds). If this determination is Yes, it indicates that the temperature of the engine when the fuel cut is canceled is low, and the intake charging efficiency is high. In step S42, a corresponding correction coefficient KGCYLMOTST is obtained by referring to a map as shown in FIG. 7 based on the elapsed time Ton from when the fuel cut is canceled. In step S43, the corrected intake air amount estimated value GCYLF is calculated by multiplying the estimated intake air amount GCYL by the correction coefficient KGCYLMOTST. Thus, the intake air amount can be estimated to better reflect the current charging efficiency even when the charging efficiency of the intake air changes due to the non-combustion state in which the fuel cut is performed.

  The value of the predetermined time in step S31 in FIG. 16 and the value of the predetermined time in step S41 are different in this embodiment, and the former is set to be longer than the latter. The reason for this will be described. The main difference between when the ignition is turned off and when the fuel cut is performed is whether or not fresh air is always introduced into the cylinder. That is, when the ignition is turned off, fresh air is not introduced into the cylinder, so the temperature in the cylinder is unlikely to decrease. On the other hand, when the fuel is cut, the intake / exhaust valve of the cylinder is in motion, so that heat exchange is promoted by introducing fresh air, and the temperature in the cylinder tends to decrease. Therefore, preferably, the value of the predetermined time when the ignition is turned off is set longer than the value of the predetermined time when the fuel cut is performed.

  If the determination in step S41 is No, it can be considered that the map as shown in FIG. 5 can be used (that is, the temperature is high). Therefore, in step S44, the estimated intake air amount GCYL is set to GCYLF without correction.

  In the above embodiment, the predicted value of the lift amount is used to estimate the intake air amount, but the present invention is applicable to the intake air amount estimated by any other method. For example, even when the current intake air amount is estimated from the current value of the lift amount, the correction method based on the duration of the non-combustion state according to the present invention can be applied. Further, the method for predicting the lift amount is not limited to the above embodiment, and the correction method according to the present invention can be applied to the intake air amount estimated using the lift amount predicted by an arbitrary method.

  In the above-described embodiment, the non-combustion state has been described as an example in which the engine ignition is off and the fuel cut is performed. As still another example, a case where the cylinder of the engine is inactive (for example, an idle stop in which all cylinders are deactivated) may be included in the non-combustion state. In this case, it is only necessary to count the duration during which the cylinder is inactive and perform correction according to the elapsed time since the start of combustion by releasing the cylinder inactive.

  Furthermore, when some cylinders are deactivated or when fuel cut is performed only for some cylinders, the above-described correction in consideration of the charging efficiency is performed for the calculation of the fuel injection amount for the cylinders that do not perform combustion. A technique may be applied.

  The present invention is not limited to the above embodiment, and various modifications can be made. In addition, the above embodiment can be applied to a general-purpose internal combustion engine (for example, an outboard motor).

1 schematically shows an internal combustion engine and a control device therefor according to one embodiment of the present invention. FIG. The figure which shows schematically the structure of the valve action characteristic variable apparatus according to one Example of this invention. The figure which shows schematically the structure of the 1st mechanism according to one Example of this invention. The block diagram of the control apparatus which controls the fuel injection quantity according to one Example of this invention. The map for calculating | requiring the intake air amount estimated value according to one Example of this invention. The figure for demonstrating correction | amendment of the intake amount estimated value according to one Example of this invention. The map for calculating | requiring the correction coefficient for correct | amending the intake amount estimated value according to one Example of this invention. The map for calculating | requiring the fuel injection quantity according to one Example of this invention. The figure for demonstrating the principle of the structure of the apparatus which controls the lift amount, and the predicted value calculation of a lift amount according to one Example of this invention. The functional block diagram of the lift controller according to one Example of this invention. The figure for demonstrating the method of calculating | requiring the synthetic transfer function of a lift controller and a plant according to one Example of this invention. The figure for demonstrating the method of calculating | requiring the synthetic transfer function of a lift controller and a plant according to one Example of this invention. The figure for demonstrating the method of calculating | requiring the formula which calculates a predicted value based on the synthetic | combination transfer function according to one Example of this invention. The functional block diagram of the predicted value calculation part according to one Example of this invention. The flowchart of the process which calculates the fuel injection quantity according to one Example of this invention. The flowchart of the correction process according to one Example of this invention. The flowchart of the correction | amendment process according to the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ECU 2 Engine 3 Intake pipe 15 CSA sensor 20 Valve operating characteristic variable device 23 Motor 36 Control shaft 40 Intake valve

Claims (3)

In an internal combustion engine having a variable valve mechanism that can change the lift amount of an intake valve, a control device for controlling the fuel injection amount,
Means for detecting an actual lift amount of the intake valve;
An intake air amount estimating means for estimating an intake air amount supplied to the internal combustion engine based on the detected actual lift amount and calculating an intake air amount estimated value;
Counting means for counting a duration of a non-combustion state in which combustion is not performed in the internal combustion engine;
When the internal combustion engine transitions from the non-combustion state to a combustion state where combustion is performed, the duration is compared with a predetermined time, and if the duration is equal to or longer than the predetermined time, the estimated intake air amount Correction means for correcting
Means for calculating a fuel injection amount based on the corrected intake amount estimation value;
A control device comprising: Furthermore, it comprises means for counting the elapsed time from when the internal combustion engine has shifted to the combustion state,
The correction means performs the correction so that the estimated intake air amount decreases as the elapsed time increases.
The apparatus of claim 1. Means for performing feedback control at a predetermined control period so that the detected actual lift amount converges to a target lift amount with a predetermined time constant;
A predicted value calculation means for calculating a predicted value of a lift amount in the next control cycle by adding a value obtained by multiplying a difference between the target lift amount and the actual lift amount by a predetermined gain to the actual lift amount. The gain is calculated based on the length of the control cycle and the time constant;
The control device according to claim 1, comprising:

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