JP5306156B2 - Intake control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intake control device which enhances the responsiveness of intake valve lift amount control in a high rotation operation state without using an expensive actuator. <P>SOLUTION: A maximum torque generation lift amount LFTMT is calculated in accordance with an engine speed NE, and a basic lift amount lower limit value ALTHAREAFX is calculated in accordance with the maximum torque generation lift amount LFTMT. The basic lift amount lower limit value ALTHAREAFX is set to be increased with the increase of the maximum torque generation lift amount LFTMT. A lift amount lower limit value ALTHAREA is calculated so as to follow with a change speed restricted with respect to the change of the basic lift amount lower limit value ALTHAREAFX. Thus, even when the maximum torque generation lift amount LFTMT is in the large high rotation operation state, the response time required to reach a target lift amount can be reduced. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an intake control device for an internal combustion engine, and more particularly to an intake control device for an internal combustion engine including a variable valve operation characteristic mechanism capable of continuously changing the lift amount of the intake valve.

  Patent Document 1 discloses an intake control device for an internal combustion engine that includes a variable valve operation characteristic mechanism and a throttle valve that can continuously change the lift amount of the intake valve. According to this intake control device, in a medium load operation state where the target intake air amount of the engine is larger than a predetermined amount (an air amount slightly larger than the intake air amount in the idle operation state), a constant target gauge pressure (intake pressure and atmospheric pressure) The intake air amount control (hereinafter simply referred to as “intake valve lift amount control”) is performed by changing the lift amount of the intake valve while controlling the opening degree of the throttle valve so that the pressure difference is maintained. This is because the intake valve lift amount control can perform control with higher responsiveness than the intake air amount control (hereinafter simply referred to as “throttle valve opening control”) by changing the opening of the throttle valve.

JP 2009-250029 A

  However, since the responsiveness of the throttle valve opening control becomes high when the engine is operating at a high speed, the throttle valve opening control must be performed unless an expensive actuator with good responsiveness is used in the mechanism for changing the lift amount of the intake valve. The same responsiveness as that cannot be realized. That is, in a mechanism for changing the lift amount of the intake valve, when a low-cost normal actuator is used, the response of the intake valve lift amount control may be inferior to the throttle valve opening control.

  The present invention has been made paying attention to this point, and it is an object of the present invention to provide an intake control device capable of enhancing the responsiveness of intake valve lift amount control in a high rotation operation state without using an expensive actuator. And

  In order to achieve the above object, a first aspect of the present invention provides a valve operating characteristic variable mechanism (41) capable of continuously changing the lift amount (LFT) of an intake valve of an internal combustion engine, and an intake passage (2 of the engine). In the intake control device for an internal combustion engine provided with a throttle valve (3) provided in the engine), a rotation speed detection means for detecting the rotation speed (NE) of the engine and a target intake air amount (GAIRCMD) of the engine are calculated. Target intake air amount calculating means, target lift amount calculating means for calculating a target lift amount (LFTCMD) which is a target value of the lift amount (LFT) according to the target intake air amount (GAIRCMD), and the target lift A lift amount control means for controlling a lift amount (LFT) of the intake valve in accordance with an amount (LFTCMD), and the target lift amount calculation means is configured to control the lift amount in accordance with the engine speed (NE). Lower limit value setting means for setting a lower limit value (ALTHAREA) of the target lift amount (LFTCMD) is provided, and the target lift amount (LFTCMD) is set so that the target lift amount (LFTCMD) is equal to or greater than the lower limit value (ALTHAARE). The lower limit value setting means calculates the predetermined engine in which the intake air amount control by changing the opening degree of the throttle valve is more responsive than the intake air amount control by changing the lift amount of the intake valve. In the engine speed range, the lower limit (ALTAREA) is set to be larger than a value in a range other than the predetermined engine speed range.

According to a second aspect of the invention, the intake control device according to claim 1, wherein the lower limit setting means comprises a change rate setting means for setting a change speed of the lower limit (ALTHAREA) (DGALTH), The lift amount control means changes the lower limit value (ALTAREA) at a set change speed (DGALTH), and the change speed setting means changes the intake air amount (GAIR) of the engine with respect to a change in the lift amount (LFT). ), The rate of change (DGALTH) is increased as the rate of change (LGSLOP) decreases.

The invention according to claim 3, in the intake control device according to claim 2, wherein the change rate setting means, said change in response to the torque transmission state of the transmission (CLER) connected to the output side of said engine It is characterized by setting a speed (DGALTH).

According to a fourth aspect of the present invention, in the intake air control apparatus according to the second or third aspect , the change speed setting means sets the change speed (DGALTH) during a fuel cut operation in which fuel supply to the engine is stopped. The maximum value (DGALMAX) is set.

  According to the first aspect of the present invention, the predetermined engine speed at which the responsiveness is better in the intake air amount control by changing the opening degree of the throttle valve than in the intake air amount control by changing the lift amount of the intake valve. In the numerical range, the lower limit value of the target lift amount is set to be larger than the value in the range other than the predetermined engine speed range. Therefore, when the target intake air amount suddenly changes in the predetermined engine speed range, the required change amount of the intake valve lift amount becomes small, and the response time until the target lift amount is reached can be shortened. . As a result, the responsiveness of intake valve lift amount control can be enhanced within a predetermined engine speed range.

According to the second aspect of the invention, the lower limit value of the lift amount is changed at the set change speed, and the change rate of the lower limit value of the lift amount decreases as the rate of change of the intake air amount with respect to the change of the intake valve lift amount decreases. Control to increase the value is performed. If the lower limit of the lift amount is rapidly changed, there is a problem that the difference between the actual intake air amount and the target intake air amount becomes large, and it is necessary to suppress the change rate of the lift amount. When the change rate of the intake air amount with respect to the change of the intake valve lift amount is large, this deviation becomes larger. Therefore, the lower limit of the lift amount can be changed at an appropriate change speed while suppressing the deviation of the actual intake air quantity from the target intake air quantity by increasing the change speed as the intake air quantity change rate decreases. it can.

According to the third aspect of the present invention, the changing speed of the lift amount lower limit value is set according to the torque transmission state of the transmission. For example, when the clutch is disengaged or when the clutch engagement rate is low, even if the actual intake air amount deviates from the target intake air amount, the influence on the drivability of the vehicle is small. Therefore, the change rate of the lower limit of the lift amount is set according to the torque transmission state of the transmission, and more specifically, the change rate is increased as the torque transmission rate decreases, thereby suppressing the influence on the vehicle drivability. In addition, the changing speed of the lift amount lower limit value can be set appropriately.

According to the invention described in claim 4 , during the fuel cut operation, the changing speed of the lower limit of the lift amount is set to the maximum value. During the fuel cut operation, combustion in the engine is not performed, so there is almost no influence of the difference in intake air amount. Therefore, the lift amount lower limit value can be quickly changed by setting the change speed to the maximum value.

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 operating characteristic of an intake valve and an exhaust valve. It is a figure for demonstrating the outline | summary of intake control. It is a figure for demonstrating the response characteristic of intake air amount control. It is a time chart which shows the change of the target gauge pressure (PBGASTD) and the actual gauge pressure (PBGA) corresponding to the change of the intake valve lift amount (LFT). It is a time chart for demonstrating the change aspect of a lift amount lower limit (ALTAREA). It is a figure which shows the relationship between intake valve lift amount (LFT) and intake air amount (GAIR). It is a flowchart of the process which calculates target lift amount (LFTCMD). It is a flowchart of a process which calculates a lift amount lower limit value (ALTAREA). It is a figure which shows the table referred by the process of FIG. It is a figure which shows the table referred by the process of FIG. It is a flowchart of the process which calculates a target gauge pressure (PBGACMD). It is a figure which shows the table referred by the process of FIG. It is a figure for demonstrating the setting of the target lift amount according to target intake air amount (GAIRCMD) and engine speed (NE).

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 1 is a diagram showing a configuration of an internal combustion engine and its control device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of a valve operating characteristic variable device. In FIG. 1, for example, an internal combustion engine (hereinafter simply referred to as “engine”) 1 having four cylinders includes an intake valve and an exhaust valve, a cam for driving them, and a valve operating characteristic variable device 40. The valve operating characteristic variable device 40 includes a first valve operating characteristic variable mechanism 41 that continuously changes the lift amount (maximum lift amount) and the opening angle (valve opening period) of the intake valve, and a cam that drives the intake valve. The second valve operating characteristic variable mechanism 42 as a cam phase variable mechanism that continuously changes the operating phase based on the crankshaft rotation angle, and the exhaust valve lift amount and opening angle (opening engine) are switched in two stages. And a third valve operating characteristic variable mechanism 47. 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 intake passage 2 of the engine 1. A throttle valve opening (TH) sensor 4 is connected to the throttle valve 3, and an electric signal corresponding to the opening of the throttle valve 3 is output to an electronic control unit (hereinafter referred to as “ECU”) 5. Supply. An actuator 7 that drives the throttle valve 3 is connected to the throttle valve 3, and the operation of the actuator 7 is controlled by the ECU 5. An intake air amount sensor 13 for detecting an intake air amount GAIR [g / sec] is provided on the upstream side of the throttle valve 3 in the intake passage 2, and the detection signal is supplied to the ECU 5.

  The fuel injection valve 6 is provided for each cylinder slightly upstream of the intake valve, and each injection valve is connected to a fuel pump (not shown) and electrically connected to the ECU 5, and the fuel from the ECU 5 The valve opening time of the injection valve 6 is controlled. The ignition plug 15 of each cylinder of the engine 1 is connected to the ECU 5, and the ECU 5 supplies an ignition signal to the ignition plug 15 to perform ignition timing control.

  An intake pressure sensor 8 for detecting the intake pressure PBA and an intake air temperature sensor 9 for detecting the intake air temperature TA are attached downstream of the throttle valve 3. An engine cooling water temperature sensor 10 that detects the engine cooling water temperature TW is attached to the main body of the engine 1. Detection signals from these sensors are supplied to the ECU 5.

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

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

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

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

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

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

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

  The first valve operating characteristic variable mechanism 41 changes the lift amount LFT (and opening angle) of the intake valve as shown by the solid line in FIG. Further, the lift amount (and opening angle) of the exhaust valve is changed in two stages by the third valve operating characteristic variable mechanism 47 as shown by the broken line in FIG.

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

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

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

  FIG. 5 is a diagram for explaining the outline of intake air amount control in this embodiment. FIG. 5A shows the relationship between the target intake air amount GAIRCMD and the target gauge pressure PBGACMD, and FIG. Indicates the relationship between the target intake air amount GAIRCMD and the target lift amount LFTCMD of the intake valve.

  In an operating state where the target intake air amount GAIRCMD is equal to or less than the boundary intake air amount GAPBPPARX, the target lift amount LFTCMD of the intake valve is maintained at the lift amount lower limit value ALTHAREA, and the gauge pressure PBGA (= PBA-PA) is equal to the target gauge pressure PBGCMD. The opening TH of the throttle valve 3 is controlled so as to match. Hereinafter, a region where this control is performed is referred to as a “gauge pressure control region RPG”.

  In an operation state where the target intake air amount GAIRCMD exceeds the boundary intake air amount GAPBPPARX, the target gauge pressure PBGACMD is normally maintained at the reference gauge pressure PBGASTD (for example, −13.3 kPa (−100 mmHg)), and the lift amount of the intake valve By changing the LFT, the intake air amount is controlled. Hereinafter, a region where this control is performed is referred to as a “lift amount control region RLFT”. A region on the higher load side than the lift amount control region RLFT (corresponding to an operating state where the accelerator pedal operation amount AP is in the vicinity of the maximum value APMAX) is referred to as a high load control region RWOT. In the high load control region RWOT, the throttle valve opening TH and the intake valve lift amount LFT are both controlled to increase as the target intake air amount GAIRCMD increases.

In the gauge pressure control region RPG, the relationship between the target intake air amount GAIRCMD and the target gauge pressure PBGACMD is expressed by the following formula (1). CR in the following equation (1) is an inclination parameter indicating an inclination, and PBGA0 is an intercept parameter indicating a target gauge pressure corresponding to a state where the target intake air amount GAIRCMD is “0” as shown in FIG. It is.
PBGACMD = CR × GAIRCMD + PBGA0 (1)

  FIG. 6 shows the response time of intake air amount control (hereinafter referred to as “throttle control”) by changing the throttle valve opening TH and intake air amount control (hereinafter referred to as “lift amount control”) by changing the intake valve lift amount LFT. It is a figure for demonstrating. When the target intake air amount GAIRCMD increases to the target value GAIRTGT in a stepwise manner at time t0, the time required for the actual intake air amount GAIR to reach the response time determination value GAIRRES (= 0.63 × GAIRGTGT) TRLFT and TRTH are the lift amount control response time and the throttle control response time, respectively.

  Normally, as shown in FIG. 6A, the lift amount control response time TRLFT is shorter than the throttle control response time TRTH (responsiveness is good), but in an operating state where the engine speed NE is high (for example, 3000 rpm), In the example shown in FIG. 6B (an example using a relatively low-cost motor 43), the difference between the two decreases as the load factor EL [%] increases, and the throttle control response time TRTH is higher in the high load region. Becomes shorter.

  Therefore, in the present embodiment, the engine high-speed operation state (hereinafter referred to as “specific high-speed operation state”) in which the throttle control response time TRTH is shorter than the lift amount control response time TRLFT is the maximum torque at which the engine output torque becomes maximum. Focusing on the fact that there is a correlation with the operation state in which the generated lift amount LFTMT increases, control is performed to increase the lift amount lower limit value ALTAREA as the maximum torque generating lift amount LFTMT increases. Thereby, the responsiveness of the lift amount control in the specific high rotation operation state can be enhanced.

  When the lift amount lower limit value ALTHAREA is changed, it may be necessary to change the throttle valve opening TH in order to control the gauge pressure PBGA to the target gauge pressure PBGACMD. FIG. 7 is a time chart for explaining a problem in such a case, that is, in a case where the throttle valve opening TH is changed in accordance with the change of the lift amount lower limit value ALTAREA. FIGS. 7A to 7D correspond to the control operation during engine acceleration, and FIGS. 7E to 7H correspond to the control operation during engine deceleration.

  When the engine is accelerated, the lift amount LFT is increased when the lift amount lower limit value ALTHAREA increases as the engine speed NE increases while the target intake air amount GAIRCMD is kept constant (FIG. 7B). Increases ((c) in the figure). Accordingly, although the target gauge pressure PBGACMD is decreased, the actual change in the gauge pressure PBGA is delayed ((d) in the figure), so that the actual intake air quantity GAIR becomes larger than the target intake air quantity GAIRCMD ((b) in the figure). , May accelerate beyond the driver's intentions.

  On the other hand, when the engine decelerates, the lift amount decreases when the lift amount lower limit value ALTHAREA decreases as the engine speed NE decreases while the target intake air amount GAIRCMD is kept constant (FIG. 7 (f)). LFT decreases ((g) in the figure). Therefore, although the target gauge pressure PBGACMD is increased, the actual change in the gauge pressure PBGA is delayed (FIG. (H)), so the actual intake air amount GAIR is smaller than the target intake air amount GAIRCMD (FIG. (F)). There is a risk of engine stall during sudden deceleration.

  Therefore, in this embodiment, in order to solve the above-described problem, a process of limiting the change rate of the lift amount lower limit value ALTAREA so that the change of the actual gauge pressure PBGA can follow the change of the lift amount lower limit value ALTAREA (FIG. 11). See).

  FIG. 8 is a time chart for explaining the change speed limiting process, and the basic lift amount lower limit value ALTAREAFX (broken line) set in accordance with the engine speed NE (maximum torque generating lift amount) has changed in a stepped manner. Sometimes, the lift amount lower limit value ALTAREA is controlled to gradually change so that the change amount per TDC period (TDC pulse generation time interval) does not exceed the change amount parameter DGALTH.

  FIG. 9 is a diagram showing the relationship between the intake valve lift amount LFT and the intake air amount GAIR, and the slope of the curve shown in this figure decreases as the lift amount LFT increases. Therefore, the amount of change in the intake air amount GAIR when the lift amount LFT changes by a unit amount is larger when the lift amount LFT is increased than when the lift amount LFT is decreased. Get smaller.

  In addition, the allowable range of the influence of the deviation of the intake air amount GAIR from the target intake air amount GAIRCMD is such that the higher the vehicle speed VP and the lower the engagement rate CLER of the clutch of the transmission connected to the engine output shaft. , Is thought to grow. That is, as the vehicle speed VP increases and the clutch engagement rate CLER decreases, it is considered that the driver is less likely to perceive the influence of the difference in intake air amount.

Therefore, in the present embodiment, the allowable fluctuation amount of the intake air amount is represented by DGAIRMAX [g / TDC] (air mass per 1 TDC period), and the air amount change rate indicating the slope of the curve shown in FIG. / Mm] (air mass per 1 mm lift amount), and the change parameter DGALTH [mm / TDC] shown in FIG. 8 is calculated by the following equation (2). That is, the change amount parameter DGALTH is set to be proportional to the allowable change amount DGARIMAX and inversely proportional to the air amount change rate LGSLOP.
DGALTH = DGAIRMAX / LGSLOP (2)

  The allowable fluctuation amount DGAIRMAX is set to increase as the vehicle speed VP increases and the clutch engagement rate CLER decreases, and the air amount change rate LGSLOP is set according to the lift amount LFT, and the lift While the amount LFT is increasing, it is set to a smaller value than when it is decreasing. Thereby, the optimal change amount parameter DGALTH can be set according to the allowable change amount DGAIRMAX and the air amount change rate LGSLOP. As a result, it is possible to appropriately suppress the adverse effects of changing the lift amount lower limit value ALTAREA within a range that does not affect vehicle drivability.

FIG. 10 is a flowchart of a process for calculating the target lift amount LFTCMD of the intake valve. This process is executed every predetermined time by the CPU of the ECU 5.
In step S11, the basic target intake air amount GAIRCMDB is calculated in accordance with the accelerator pedal operation amount AP and the engine speed NE. The basic target intake air amount GAIRCMDB is set to be substantially proportional to the accelerator pedal operation amount AP. In step S12, the target intake air amount GAIRCMD is calculated by correcting the air density by correcting the basic target intake air amount GAIRCMDB by the atmospheric pressure PA and the intake air temperature TA, and further performing a predetermined limit process.

  In step S13, the basic target lift amount LFTCMDM is calculated according to the target intake air amount GAIRCMD. In the present embodiment, the target intake air amount corresponds to a plurality of predetermined engine speeds, a plurality of predetermined operation phases of the intake valve, a plurality of predetermined gauge pressures, and an operation characteristic of the exhaust valve (see FIG. 4A). A plurality of LFTCMD tables for calculating the basic target lift amount LFTCMDM from GAIRCMD are stored in the storage circuit of the ECU 5 in advance. Therefore, in step S13, the engine speed NE, the intake valve operating phase CAIN, the gauge pressure PBGA, and the LFTCMD table corresponding to the selected exhaust valve operating characteristic are selected, and the selected table is set as the target intake air amount GAIRCMD. A search is made accordingly, and a basic target lift amount LFTCMDM is calculated. At this time, an interpolation operation is appropriately performed.

  In step S14, it is determined whether or not the basic target lift amount LFTCMDM is smaller than the lift amount lower limit value ALTAREA calculated in the process of FIG. 11. If the answer is affirmative (YES), the target lift amount LFTCMD is lifted. An amount lower limit value ALTHAREA is set (step S15). On the other hand, when the basic target lift amount LFTCMDM is equal to or greater than the lift amount lower limit value ALTHAREA, the target lift amount LFTCMD is set to the basic target lift amount LFTCMDM (step S16).

  The calculated target lift amount LFTCMD is converted into a target CS angle CSACMD that is a target value of the CS angle CSA, and the drive control of the motor 43 is performed so that the detected CS angle CSA matches the target CS angle CSACMD. . As a result, the lift amount LFT of the intake valve is controlled to the target lift amount LFTCMD.

  FIG. 11 is a flowchart of a process for calculating the lift amount lower limit value ALTAREA. This process is executed by the CPU of the ECU 5 in synchronization with the generation of the TDC pulse.

  In step S20, the LFTMT table shown in FIG. 12A is searched according to the engine speed NE, and the maximum torque generating lift amount LFTMT is calculated. The maximum torque generation lift amount LFTMT is an intake valve lift amount that maximizes the engine output torque, and increases as the engine speed NE increases.

  In step S21, the ALTAREAFX table shown in FIG. 12B is searched according to the maximum torque generation lift amount LFTMT, and the basic lift amount lower limit value ALTAREAFX is calculated. The ALTAREAFX table is set such that the basic lift amount lower limit value ALTAREAFX increases as the maximum torque generating lift amount LFTMT increases.

  In step S22, the LGSLOP table shown in FIG. 13A is searched according to the intake valve lift amount LFT, and the air amount change rate LGSLOP is calculated. When the intake valve lift amount LFT is greater than or equal to the previous value, a table indicated by a broken line is searched, and when the intake valve lift amount LFT is smaller than the previous value, a table indicated by a solid line is searched.

In step S23, a DGAIRMAXB table shown in FIG. 13B is searched according to the vehicle speed VP to calculate an allowable basic amount DGAIRMAXB, and a clutch clutch engagement rate CLER (connected to the output shaft of the engine 1). The KCL table is searched according to the ratio of the input shaft rotation speed and the output shaft rotation speed), and the clutch correction coefficient KCL is calculated. The DGAIRMAXB table is set such that the allowable basic amount DGAIRMAXB increases as the vehicle speed VP increases, and the KCL table is set so that the clutch correction coefficient KCL decreases as the clutch engagement rate CLER increases. Then, the allowable variation DGAIRMAX is calculated by applying the allowable basic amount DGAIRMAXB and the clutch correction coefficient KCL to the following equation (3). The clutch engagement rate CLER is supplied to the ECU 5 from a shift control electronic control unit (not shown).
DGAIRMAX = DGAIRMAXB × KCL (3)

  In step S24, the change amount parameter DGALTH is calculated from the equation (2). In step S25, it is determined whether or not a fuel cut flag FFC is “1”. The fuel cut flag FFC is set to “1” in the operation state in which the fuel supply to the engine is stopped.

  If the answer to step S25 is affirmative (YES), that is, if the fuel cut operation is being performed, the change amount parameter DGALTH is set to a predetermined maximum value DGALMAX (step S26). If the answer to step S25 is negative (NO), the process immediately proceeds to step S27.

In step S27, it is determined whether or not a value obtained by subtracting the previous value ALTHAREA (k−1) of the lift amount lower limit value from the basic lift amount lower limit value ALTAREAFX calculated in step S21 is greater than “0”. If the answer is affirmative (YES), a lift amount lower limit value ALTHAREA is calculated by the following equation (4) (step S28).
ALTAREA = ALTAREA (k-1) + DGALTH (4)

  In step S29, it is determined whether or not the lift amount lower limit value ALTAREA is larger than the basic lift amount lower limit value ALTAREAFX. If the answer is affirmative (YES), the lift amount lower limit value ALTAREA is changed to the basic lift amount lower limit value ALTAREAFX. Set (step S32).

On the other hand, if the answer to step S27 is negative (NO), that is, if the basic lift amount lower limit value ALTAREAFX is less than or equal to the previous value ALTHAREA (k-1) of the lift amount lower limit value, the lift amount lower limit value ALTAREA is calculated by the following equation (5). Is calculated (step S30).
ALTAREA = ALTAREA (k-1) -DGALTH (5)

  In step S31, it is determined whether or not the lift amount lower limit value ALTAREA is smaller than the basic lift amount lower limit value ALTAREAFX. If the answer to step S31 is affirmative (YES), the process proceeds to step S32.

  If the answer to step S29 or S31 is negative (NO), the process immediately ends.

  As described above, the lift amount lower limit value ALTAREA is changed by the process of FIG. 11 at a change speed according to the change amount parameter DGALTH.

  FIG. 14 is a flowchart of processing for calculating the target gauge pressure PBGACMD in the gauge pressure control region RPG and the lift amount control region RLFT, and this processing is executed by the CPU of the ECU 5 at predetermined time intervals.

  In step S41, the LFTCMD table corresponding to the reference gauge pressure PBGASTD is selected according to the engine speed NE, the intake valve operating phase CAIN, and the exhaust valve operating characteristics, and the selected LFTCMD table is selected according to the lift amount lower limit value ALTHAREA. By performing a reverse search, the first intake air amount GAIR1 is calculated. An example of the selected LFTCMD table is indicated by a solid line L21 in FIG.

  In step S42, an LFTCMD table corresponding to a predetermined gauge pressure PBGARL (for example, −80.0 kPa (−600 mmHg)) lower than the reference gauge pressure PBGASTD is selected according to the engine speed NE and the intake valve operating phase CAIN, and the lift amount The second intake air amount GAIR2 is calculated by reversely searching the selected LFTCMD table according to the lower limit value ALTHAREA. An example of the selected LFTCMD table is indicated by a broken line L22 in FIG.

In step S43, the first intake air amount GAIR1, the atmospheric pressure PA, and the intake air temperature TA are applied to the following equation (A), air density correction is performed, and the boundary intake air amount GAPBPARX shown in FIG. 5B is calculated. To do. PA0 and TA0 in the formula (A) are the atmospheric pressure and the intake air temperature in a predetermined reference state, and are set to 101.3 kPa (760 mmHg) and 25 ° C., for example.

In step S44, the reference gauge pressure PBGASTD, the predetermined gauge pressure PBGARRL, the first and second intake air amounts GAIR1, GAIR2 are applied to the following equation (7), and the slope parameter CR of the equation (1) is calculated. The calculated slope parameter CR, boundary intake air amount GAPBPARX, and reference gauge pressure PBGASTD are applied to the following equation (8) to calculate the intercept parameter PBGA0.
CR = (PBGASTD-PBGARL) / (GAIR1-GAIR2)
(7)
PBGA0 = PBGASTD-CR × GABPBPAX (8)

  In step S45, the calculated slope parameter CR and intercept parameter PBGA0 and the target intake air amount GAIRCMD are applied to the above equation (1) to calculate the target gauge pressure PBGACMD.

  In step S46, it is determined whether or not the target gauge pressure PBGACMD calculated in step S45 is higher than the reference gauge pressure PBGASTD. If the answer is affirmative (YES), the target gauge pressure PBGACMD is set to the reference gauge pressure PBGASTD. Set (step S47). If the answer to step S46 is negative (NO), and the target gauge pressure PBGACMD is equal to or less than the reference gauge pressure PBGASTD, the process ends immediately.

  The ECU 5 controls the opening of the throttle valve 3 (performs drive control of the actuator 7) so that the detected gauge pressure PBGA (= PBA-PA) matches the target cage pressure PBGACMD.

  As a result of changing the target gauge pressure PBGASTD according to the lift amount lower limit value ALTAREA calculated by the process shown in FIG. 11 by the process of FIG. 14, the actual gauge pressure PBGA is changed with the change of the lift amount lower limit value ALTAREA. Is done. Therefore, the gauge pressure PBGA can be appropriately controlled when performing the control to change the lift amount lower limit value ALTAREA described above.

  As described above, in the present embodiment, the maximum torque generation lift amount LFTMT that maximizes the engine output torque is calculated according to the engine speed NE, and the lift amount lower limit value ALTAREA increases as the maximum torque generation lift amount LFTMT increases. To be controlled. When the maximum torque generating lift amount LFTMT increases, the amount of change in the intake valve lift amount LFT when the target intake air amount (≈target torque) GAIRCMD suddenly changes increases. Therefore, by increasing the lift amount lower limit value ALTAREA as the maximum torque generating lift amount LFTMT increases, the required change amount of the intake valve lift amount LFT becomes smaller, and the response time until the target lift amount LFTCMD is reached is reduced. It can be shortened. Since the maximum torque generation lift amount LFTMT tends to increase as the engine speed NE increases, the responsiveness of intake valve lift amount control in a high rotation operation state where high control responsiveness is required can be enhanced.

  When the maximum torque generating lift amount LFTMT changes, the lift amount lower limit value ALTAREA is changed using the change amount parameter DGALTH, and the air amount change rate LGSLOP indicating the change rate of the intake air amount with respect to the change of the intake valve lift amount decreases. The more the amount of change parameter DGALTH is increased, the more control is performed. If the lift amount lower limit value ALTHAREA is changed suddenly, there is a problem that the actual intake air amount GAIR deviates from the target intake air amount GAIRCMD, and this deviation becomes larger when the air amount change rate LGSLOP is large. Accordingly, by increasing the change amount parameter DGALTH as the air amount change rate LGSLOP decreases, the deviation of the actual intake air amount GAIR from the target intake air amount GAIRCMD is suppressed, and the lift amount lower limit value ALTAREA at an appropriate change speed. Can be changed.

  Further, the change amount parameter DGALTH is set according to the clutch engagement rate CLER (torque transmission state) of the transmission. For example, when the clutch is disengaged or when the engagement rate CLER is low, even if the difference of the intake air amount GAIR from the target intake air amount GAIRCMD is relatively large, the influence on the drivability of the vehicle is small. Accordingly, the change amount parameter DGALTH is set in accordance with the clutch engagement rate CLER of the transmission. More specifically, the change amount parameter DGALTH is increased as the clutch engagement rate CLER decreases, thereby affecting the vehicle drivability. The change speed of the lift amount lower limit value ALTAREA can be appropriately set while being suppressed.

  During the fuel cut operation, the change amount parameter DGALTH is set to a predetermined maximum value DGALMAX. During the fuel cut operation, combustion in the engine is not performed, so there is almost no influence of the difference in the intake air amount GAIR. Therefore, the lift amount lower limit value ALTAREA can be quickly changed by setting the change amount parameter DGALTH to the predetermined maximum value DGALMAX.

  In the present embodiment, the crank angle position sensor 11 corresponds to the rotation speed detection means, and the motor 43 constitutes a part of the lift amount control means. The ECU 5 constitutes a target intake air amount calculation means, a target lift amount calculation means, a part of the lift amount control means, a lower limit value setting means, and a change speed setting means. Specifically, steps S11 and S12 in FIG. 10 correspond to the target intake air amount calculation means, steps S13 to S16 correspond to the target lift amount calculation means, and the processing in FIG. 11 corresponds to the lower limit value setting means. Steps S20 to S24 in FIG. 10 correspond to change speed setting means.

[Second Embodiment]
In the first embodiment, the lift amount lower limit value ALTHAREA is increased in accordance with the maximum torque generation lift amount LFTMT. However, in the present embodiment, the target lift amount obtained as a result of the table search in the specific high rotation operation state. A plurality of corresponding LFTCMD tables are set so that the minimum value of LFTCMD is larger than the value in other operating states. The specific high speed operation state is an engine operation state in which the response of the throttle valve opening is higher than the response of the intake valve lift amount.

  FIG. 16 is a diagram showing the set values of a plurality of LFTCMD tables in the present embodiment as a function of the engine speed NE. In this figure, LFT1 to LFT6 are predetermined lift amounts and satisfy the relationship of LFT1 <LFT2 <LFT3 <LFT4 <LFT5 <LFT6. Here, the lift amount corresponding to the target intake air amount GAIRCMD of “0” (hereinafter referred to as “table setting lower limit value”) corresponds to the lift amount lower limit value.

  In the present embodiment, the table setting lower limit value is large in a region where the engine speed NE is high.

  By using the LFTCMD table set in this way, the lift amount lower limit value is set to a relatively large value in the predetermined high rotation operation state (predetermined rotation speed range) set in advance, and the response of the lift amount control Can increase the sex.

  In the present embodiment, step S13 in FIG. 10 corresponds to target lift amount calculation means including lower limit value setting means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the throttle valve opening TH is controlled so that the detected gauge pressure PBGA coincides with the target gauge pressure PBGCMD. However, the intake pressure PBA is equal to the target intake pressure PBACMD (= PBGACMD + PA). The throttle valve opening TH may be controlled so as to match.

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

1 Internal combustion engine 2 Intake passage 3 Throttle valve 5 Electronic control unit (target intake air amount calculation means, target lift amount calculation means, lift amount control means, lower limit value setting means, change speed setting means)
7 Actuator 11 Crank angle position sensor (Rotation speed detection means)
41 First valve operation characteristic variable mechanism 43 Motor (lift amount control means)

Claims (4)

In an intake control device for an internal combustion engine, comprising: a variable valve operation characteristic mechanism capable of continuously changing the lift amount of the intake valve of the internal combustion engine; and a throttle valve provided in the intake passage of the engine.
A rotational speed detecting means for detecting the rotational speed of the engine;
A target intake air amount calculating means for calculating a target intake air amount of the engine;
Target lift amount calculating means for calculating a target lift amount that is a target value of the lift amount according to the target intake air amount;
A lift amount control means for controlling the lift amount of the intake valve according to the target lift amount;
The target lift amount calculation means includes lower limit value setting means for setting a lower limit value of the target lift amount according to the engine speed, and the target lift amount is set so that the target lift amount is equal to or greater than the lower limit value. To calculate
The lower limit value setting means is a predetermined engine speed range in which the intake air amount control by changing the opening degree of the throttle valve is more responsive than the intake air amount control by changing the lift amount of the intake valve. Then, the intake control device for an internal combustion engine, wherein the lower limit value is set to be larger than a value in a range other than the predetermined engine speed range. The lower limit value setting means has a change speed setting means for setting a change speed of the lower limit value, the lift amount control means changes the lower limit value at a set change speed, and the change speed setting means 2. The intake control device according to claim 1, wherein the rate of change is increased as the rate of change of the intake air amount of the engine with respect to the change of the lift amount decreases. The intake control apparatus according to claim 2 , wherein the change speed setting means sets the change speed according to a torque transmission state of a transmission connected to the output side of the engine. The intake control device according to claim 2 or 3 , wherein the change speed setting means sets the change speed to a maximum value during a fuel cut operation in which fuel supply to the engine is stopped.

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