JP4583354B2 - Internal EGR control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal EGR control device for an internal combustion engine that controls internal EGR in which burnt gas remains in a cylinder.

  As a conventional internal EGR control device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. The internal combustion engine is provided with a hydraulic intake valve timing variable mechanism and an exhaust valve timing variable mechanism for independently changing the intake cam phase and the exhaust cam phase with respect to the crankshaft. An intake lift mechanism and an exhaust lift mechanism are provided for changing the lifts of the intake valve and the exhaust valve, respectively.

  In this internal EGR control device, the internal EGR amount is controlled by controlling the variable valve timing mechanism and the lift mechanism and changing the valve overlap amount between the intake valve and the exhaust valve. Specifically, the intake valve is calculated so that the target valve overlap amount, the target intake cam phase, and the target intake lift are calculated according to the rotational speed and load of the internal combustion engine, and the target intake cam phase and the target intake lift are obtained. The timing variable mechanism and the intake lift mechanism are controlled. Further, the target exhaust cam phase is calculated according to the target valve overlap amount and the actual intake cam phase, and the target exhaust lift is calculated based on the target valve overlap amount and the actual intake lift. Then, the exhaust valve timing variable mechanism and the exhaust lift mechanism are controlled so that these target exhaust cam phase and target exhaust lift are obtained.

  However, since the variable exhaust valve timing mechanism is hydraulic and has low responsiveness, it takes time for the actual exhaust cam phase to converge to the target exhaust cam phase when the target exhaust cam phase changes. . On the other hand, since the exhaust lift mechanism is generally an electric type and has a higher response than the hydraulic type, the actual exhaust lift can be achieved in a relatively short time when the target exhaust lift changes. Converge to the exhaust lift. In this conventional internal EGR control device, both the target exhaust cam phase and the target exhaust lift are calculated according to the target valve overlap amount. For this reason, even if the actual exhaust lift has converged to the target exhaust lift, the actual valve overlap amount with respect to the target valve overlap amount until the actual exhaust cam phase converges to the target exhaust cam phase. As a result, the accuracy of control of the internal EGR amount is lowered.

  In particular, when control of the internal EGR amount is performed by increasing the closing timing of the exhaust valve so that the burned gas remains in the cylinder without depending on the valve overlap, the high-temperature internal EGR is in the cylinder. Therefore, if the accuracy of the control is low, the combustion state changes, which may cause instability.

  The present invention has been made to solve such a problem, and when the internal EGR is controlled by changing both the exhaust cam phase and the exhaust lift, the internal EGR amount is accurately controlled. An object of the present invention is to provide an internal EGR control device for an internal combustion engine.

JP 2005-127180 A

In order to achieve the above object, according to the first aspect of the present invention, the exhaust cam phase that is the phase of the exhaust cam 9 that drives the exhaust valve 7 relative to the crankshaft 3d is changed by the exhaust cam phase variable mechanism 50, and the exhaust valve 7 is an internal EGR control device 1 of the internal combustion engine 3 that controls internal EGR that causes burnt gas to remain in the cylinder 3a by changing the lift of the exhaust gas by the variable exhaust lift mechanism 70, and is a target of the internal EGR amount. The target internal EGR amount setting means (the ECU 2 in the embodiment (hereinafter the same in this section), step 1) for setting the target internal EGR amount INEGRCMD, and the target of the exhaust cam phase according to the set target internal EGR amount INEGRCMD. Target cam phase setting means (ECU2, step 3) for setting the target cam phase CAEXCMD to be A phase control means (ECU2, step 5) for controlling the exhaust cam phase variable mechanism 50 so that the system phase becomes the target cam phase CAEXCMD, and an actual exhaust cam phase detected as an actual cam phase (exhaust cam phase CAEX). Valve closing timing calculating means (ECU2, step 6) for calculating the valve closing timing (valve closing crank angle CAEXVC) of the exhaust valve 7 according to the cam phase detecting means (cam angle sensor 22, ECU2) and the target internal EGR amount INEGRCMD. ), The target lift setting means (ECU2, step 7) for setting the target lift (target rotation angle SAAEXCMD) of the exhaust valve in accordance with the detected actual cam phase and the calculated valve closing timing, and the exhaust valve 7 Lift control means (ECU2, step) for controlling the exhaust lift variable mechanism 70 so that the lift of the engine becomes the target lift. 10), and exhaust gas temperature obtaining means for obtaining a temperature of the exhaust gas discharged from an internal combustion engine 3 (exhaust gas temperature TEX) (exhaust gas temperature sensor 24), in accordance with the temperature of the obtained exhaust gas, the target internal EGR amount INEGRCMD Target internal EGR amount correcting means (ECU2, step 2) for correcting, and the target cam phase setting means, according to the corrected target internal EGR amount CINEGR corrected by the target internal EGR amount correcting means, the target cam phase CAEXCMD. Is set, and the valve closing timing calculating means calculates the valve closing timing of the exhaust valve 7 in accordance with the corrected target internal EGR amount CINEGR .

  According to the internal EGR control apparatus for an internal combustion engine, the exhaust cam phase is changed by the exhaust cam phase variable mechanism, and the burnt gas remains in the cylinder by changing the lift of the exhaust valve by the exhaust lift variable mechanism. Internal EGR is controlled. The target internal EGR amount is set by the target internal EGR amount setting means, the target cam phase is set according to the target internal EGR amount, and the exhaust cam phase variable mechanism is set so that the exhaust cam phase becomes this target cam phase. Be controlled. Further, a target lift of the exhaust lift is set according to the detected actual cam phase of the exhaust cam phase and the valve closing timing calculated according to the target internal EGR amount, and the lift of the exhaust valve becomes the target lift. Thus, the variable exhaust lift mechanism is controlled.

  As described above, according to the present invention, the target cam phase is set according to the target internal EGR amount, and the target lift is set according to the actual cam phase and the exhaust valve closing timing. For this reason, the responsiveness of the exhaust cam phase variable mechanism and the exhaust lift variable mechanism are different from each other. For example, when the responsiveness of the exhaust cam phase variable mechanism is lower, the response of the exhaust cam phase to the target cam phase is delayed due to the response delay. Even if the convergence is delayed, the internal EGR amount can be accurately controlled by setting the target lift using the actual cam phase that is the actual exhaust cam phase at that time as a parameter.

The target internal EGR amount correcting means corrects the target internal EGR amount according to the exhaust gas temperature, sets the target cam phase according to the corrected target internal EGR amount, and closes the exhaust valve. Valve timing is calculated. The higher the exhaust gas temperature, the larger the volume of burned gas. By correcting the target internal EGR amount according to the exhaust gas temperature, the internal EGR amount is more appropriate while compensating for the effects of temperature changes. Can be controlled.

The invention according to claim 2 further comprises exhaust gas pressure acquisition means (exhaust pressure sensor 25) for acquiring the pressure of exhaust gas (exhaust pressure PEX) in the internal EGR control device 1 of the internal combustion engine 3 according to claim 1 , The target internal EGR amount correction means corrects the target internal EGR amount INEGRCMD further according to the acquired exhaust gas pressure.

  According to this configuration, since the correction of the target internal EGR amount is performed according to the pressure of the exhaust gas in addition to the temperature of the exhaust gas, the internal EGR amount can be more appropriately controlled.

According to a third aspect of the present invention, in the internal EGR control device 1 of the internal combustion engine 3 according to the first or second aspect, the upper limit value setting means (ECU2, ECU2) sets the upper limit value SAAEXLMT of the target lift based on the actual cam phase. Step 21) and target lift limiting means (ECU2, steps 22, 23) for limiting the target lift to a set upper limit value SAAEXLMT or less are further provided.

  According to this configuration, the upper limit value of the target lift is set on the basis of the actual cam phase, and the target lift is limited to be equal to or lower than the set upper limit value by the target lift limiting means. For this reason, when the variable exhaust lift mechanism is of a type in which the opening timing of the exhaust valve is advanced as the target lift increases, the exhaust valve starts to open considerably before the end of the expansion stroke. Can be avoided. As a result, a large loss of pressure in the cylinder during the expansion stroke can be prevented, and the output of the internal combustion engine can be secured.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an internal EGR control device 1 according to an embodiment of the present invention and an internal combustion engine (hereinafter referred to as “engine”) 3 to which the internal EGR control device 1 is applied. The engine 3 is an in-line four-cylinder gasoline engine having four cylinders 3a (only one is shown), and is mounted on a vehicle (not shown). A combustion chamber 3e is formed between the piston 3b and the cylinder head 3c of each cylinder 3a.

  The engine 3 is integrated with a pair of intake valves 4 and 4 and a pair of exhaust valves 7 and 7 (only one is shown), an intake camshaft 5 on the intake side, and the intake camshaft 5 provided for each cylinder 3a. , An exhaust camshaft 8 on the exhaust side, an exhaust cam 9 provided integrally with the exhaust camshaft 8, a fuel injection valve 10 (see FIG. 2), and an ignition plug 11 (FIG. 2). And an exhaust side valve mechanism 40 and the like.

  A crank angle sensor 21 is provided on the crankshaft 3 d of the engine 3. The crank angle sensor 21 outputs a CRK signal, which is a pulse signal, to the ECU 2 at every predetermined crank angle (for example, 1 °) as the crankshaft 3d rotates. The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 3 based on the CRK signal.

  Each of the intake camshaft 5 and the exhaust camshaft 8 is rotatably supported by the cylinder head 3c via a holder (not shown), and extends along the arrangement direction of the cylinders 3a. The intake camshaft 5 is connected to the crankshaft 3d via a timing chain (not shown). With this configuration, the intake camshaft 5 rotates once every two rotations of the crankshaft 3d, and the intake valve 4 is driven to open and close by the accompanying rotation of the intake cam 6.

  Similarly, the exhaust camshaft 8 is connected to the crankshaft 3d via a timing chain (not shown). The exhaust camshaft 8 is rotated once every two rotations of the crankshaft 3d, and the exhaust cam 9 is rotated accordingly. The exhaust valve 7 is driven to open and close.

  On the other hand, the fuel injection valve 10 is provided for each cylinder 3a, and is attached to the cylinder head 3c so as to inject fuel directly into the cylinder 3a. The valve opening time and the valve opening timing of the fuel injection valve 10 are controlled by a drive signal from the ECU 2, thereby controlling the fuel injection amount and the injection timing.

  A spark plug 11 is also provided for each cylinder 3a and attached to the cylinder head 3c. The discharge state of the spark plug 11 is controlled by the ECU 2 so that the air-fuel mixture in the combustion chamber 3e is combusted at a timing corresponding to the ignition timing.

  Further, the exhaust side valve operating mechanism 40 includes an exhaust cam phase variable mechanism 50 and an exhaust lift variable mechanism 70.

  The exhaust cam phase variable mechanism 50 changes the relative phase of the exhaust camshaft 8 with respect to the crankshaft 3d (hereinafter referred to as “exhaust cam phase”) steplessly within a predetermined range. It is provided at the end on the exhaust sprocket side. As shown in FIG. 3, the exhaust cam phase varying mechanism 50 includes a housing 51, a three-blade vane 52, a hydraulic pump 53, an electromagnetic valve 54, and the like.

  The housing 51 is configured integrally with the exhaust sprocket of the exhaust camshaft 8 and includes three partition walls 51a formed at equal intervals in the circumferential direction. The vane 52 is coaxially attached to the end of the exhaust camshaft 8 on the exhaust sprocket side, extends radially outward from the exhaust camshaft 8, and is rotatably accommodated in the housing 51. In the housing 51, three advance chambers 55 and three retard chambers 56 are formed between the partition wall 51 a and the vane 52.

  The hydraulic pump 53 is a mechanical type connected to the crankshaft 3d, and sucks lubricating oil stored in the oil pan 3f of the engine 3 through the oil passage 57c as the crankshaft 3d rotates. At the same time, the pressure is raised and then supplied to the electromagnetic valve 54 via the oil passage 57c.

  The electromagnetic valve 54 is a combination of a spool valve mechanism 54a and a solenoid 54b, and is connected to the advance chamber 55 and the retard chamber 56 via the advance oil passage 57a and the retard oil passage 57b, respectively. The oil pressure Poil supplied from the hydraulic pump 53 is controlled and supplied to the advance chamber 55 and the retard chamber 56 as the advance oil pressure Pad and the retard oil pressure Prt, respectively. The solenoid 54b of the electromagnetic valve 54 changes the advance hydraulic pressure Pad and the retard hydraulic pressure Prt by moving the spool valve body of the spool valve mechanism 54a within a predetermined range by a phase control input U_CAEX described later from the ECU 2. .

  In the exhaust cam phase varying mechanism 50 configured as described above, the electromagnetic valve 54 operates in accordance with the phase control input U_CAEX during the operation of the hydraulic pump 53, whereby the advance hydraulic pressure Pad is transferred to the advance chamber 55 and the retard hydraulic pressure Prt. Are respectively supplied to the retarding angle chamber 56, whereby the relative phase between the vane 52 and the housing 51 is changed to the advance side or the retard side. As a result, the exhaust cam phase described above continuously changes between a predetermined maximum retardation value and a predetermined maximum advance value, whereby the valve timing of the exhaust valve 7 is indicated by a solid line in FIG. It is changed steplessly between the most retarded angle timing and the most advanced angle timing indicated by a two-dot chain line.

  On the other hand, a cam angle sensor 22 (see FIG. 2) is provided at the end of the exhaust camshaft 8 opposite to the exhaust cam phase varying mechanism 50. The cam angle sensor 22 (actual cam phase detecting means) outputs an EXCAM signal, which is a pulse signal, to the ECU 2 at every predetermined cam angle (for example, 1 °) as the exhaust camshaft 8 rotates. The ECU 2 calculates an exhaust cam phase CAEX (actual cam phase) based on the EXCAM signal and the above-described CRK signal.

  The variable exhaust lift mechanism 70 is for steplessly changing the lift of the exhaust valve 7 (hereinafter referred to as “exhaust lift”) between a value 0 and a predetermined maximum value. As shown in FIGS. 5 and 6, the variable exhaust lift mechanism 70 includes a control shaft 71, a rocker arm shaft 72, upper and lower rocker arms 74, 75 provided on the shafts 71, 72 for each cylinder 3a, and An actuator 80 for driving the upper and lower rocker arms 74 and 75 is provided. In the present embodiment, the exhaust lift represents the maximum lift (lift amount) of the exhaust valve 7.

  The control shaft 71 is an assembly of a rotating shaft portion 71a, a holder portion 71b, and an eccentric shaft portion 71c. The control shaft 71 extends in parallel with the exhaust camshaft 8 and is rotatably supported by the cylinder head 3c. One end thereof is connected to the actuator 80.

  The upper rocker arm 74 includes a pair of links 74a and 74a, a roller shaft 74b, a roller 74c, and a pair of coil springs 74d and 74d. The roller shaft 74b is rotatably supported at one end of each of the links 74a and 74a at both ends thereof. The roller 74c is rotatably provided on the roller shaft 74b.

  The other end of each link 74a is rotatably supported by the eccentric shaft portion 71c of the control shaft 71, and is connected to the holder portion 71b via a coil spring 74d. In the link 74a, when the roller 74c is in contact with the cam surface of the exhaust cam 9 and the roller 74c is in contact with the base circle portion of the cam surface of the exhaust cam 9 by the biasing force of the coil spring 74d, the roller shaft 74b is held at the origin position (position shown in FIG. 5) coaxial with the rotation shaft portion 71a.

  On the other hand, the lower rocker arm 75 is rotatably supported by the rocker arm shaft 72 at one end thereof, and adjustment bolts 75a and 75a are attached to the other end thereof. A predetermined tappet clearance is provided between the adjusting bolt 75a and the exhaust valve 7.

  The lower rocker arm 75 includes a pair of guide portions 75b and 75b protruding upward. The upper surface of each guide portion 75b serves as a guide surface 75c for guiding the roller shaft 74b of the upper rocker arm 74, and is in contact with the roller shaft 74b via the guide surface 75c. The guide surface 75c is formed in a predetermined arc shape that protrudes downward so that the link 74a is concentric with the eccentric shaft portion 71c when the link 74a is in the valve closing position indicated by the solid line in FIG. Further, in a state where the guide portion 75b and the roller shaft 74b are in contact with each other, the roller 74c is positioned between the guide portions 75b and 75b and contacts only the exhaust cam 9 without contacting the lower rocker arm 75.

  On the other hand, the actuator 80 is a combination of a motor, a reduction gear mechanism (both not shown) and the like, and is driven by the ECU 2 to rotate the control shaft 71 around the rotation shaft portion 71a. . As the control shaft 71 rotates, the link 74a also rotates about the roller shaft 74b.

  Next, the operation of the variable exhaust lift mechanism 70 configured as described above will be described. In the exhaust lift variable mechanism 70, when the actuator 80 is driven by a lift control input U_SAAEX described later from the ECU 2, the control shaft 71 rotates. At that time, the rotation angle SAAEX of the control shaft 71 is restricted within a predetermined range, and accordingly, the rotation range of the link 74a is also zero lift shown by a solid line in FIG. 5 when the roller shaft 74b is at the above-described origin position. It is regulated between the position and the maximum lift position indicated by a two-dot chain line.

  In this way, when the link 74a is in the zero lift position, the exhaust cam 9 rotates, and when the roller nose 74c is pushed toward the rocker arm shaft 72 by the cam nose, the link 74a rotates clockwise in FIG. 5 about the eccentric shaft portion 71c. To turn. At this time, as described above, since the guide surface 75c of the lower rocker arm 75 has a shape that coincides with the arc centered on the eccentric shaft portion 71c, the lower rocker arm 75 is in the closed position shown in FIG. Retained. As a result, the exhaust lift is maintained at the value 0, and the exhaust valve 7 is maintained in the closed state.

  On the other hand, in the state where the link 74a is rotated from the zero lift position to the maximum lift position, the link 74a is rotated about the eccentric shaft portion 71c in the clockwise direction by the rotation of the exhaust cam 9, and accordingly, The rocker arm 75 rotates downward from the valve closing position shown in FIG. 5 to open the exhaust valve 7. At that time, the rotation amount of the lower rocker arm 75, that is, the exhaust lift becomes larger as the link 74a is closer to the maximum lift position.

  As described above, the exhaust valve 7 opens with a larger lift as the link 74a is closer to the maximum lift position. Specifically, during the rotation of the exhaust cam 9, the exhaust valve 7 opens according to the valve lift curve shown by the solid line in FIG. 7 when the link 74a is at the maximum lift position, and the exhaust lift becomes the maximum value LEXMAX. . Therefore, in this variable exhaust lift mechanism 70, the link 74a is rotated between the zero lift position and the maximum lift position via the actuator 80, whereby the exhaust lift is set between the value 0 and the predetermined maximum value LEXMAX. It can be changed steplessly. When the exhaust cam phase CAEX is the same, the larger the exhaust lift, the earlier the opening timing of the exhaust valve 7 and the later the closing timing.

  The variable exhaust lift mechanism 70 is provided with a lift sensor 23 for detecting the exhaust lift (see FIG. 2). The lift sensor 23 detects the rotation angle SAAEX of the control shaft 71 and outputs a detection signal representing it to the ECU 2. As described above, since the exhaust lift is uniquely determined from the rotation angle SAAEX of the control shaft 71, the detected rotation angle SAAEX represents an actual exhaust lift.

  As described above, in this engine 3, the valve timing and lift of the exhaust valve 7 can be changed steplessly by the exhaust side valve mechanism 40, so the amount of burned gas remaining in the combustion chamber 3 e after the combustion stroke (Hereinafter referred to as “internal EGR amount”) can be freely changed. For example, the internal EGR amount becomes 0 when the exhaust cam phase CAEX is at the most retarded position and the exhaust lift is at the maximum value LEXMAX. On the other hand, the closer the exhaust cam phase CAEX is to the advance side, the earlier the valve closing timing of the exhaust valve 7, the greater the internal EGR amount, and the smaller the exhaust lift, the less the amount of burned gas discharged. As a result, the internal EGR amount increases. As is apparent from the above, in the present embodiment, the internal EGR is obtained by causing the burned gas to remain in the combustion chamber 3e by closing the exhaust valve 7 before the intake valve 4 starts to open.

  The exhaust pipe 12 of the engine 3 is provided with an exhaust temperature sensor 24 and an exhaust pressure sensor 25 in order from the upstream side. The exhaust temperature sensor 24 detects the temperature in the exhaust pipe 12 (hereinafter referred to as “exhaust temperature”) TEX, and the exhaust pressure sensor 25 detects the pressure in the exhaust pipe 12 (hereinafter referred to as “exhaust pressure”) PEX. Is output to the ECU 2.

  The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The ECU 2 executes control of the engine 3 including the fuel injection amount in accordance with a control program stored in the ROM in accordance with the detection signals from the various sensors 21 to 25 described above. Further, the ECU 2 controls the internal EGR amount by controlling the exhaust side valve mechanism 40. In the present embodiment, the ECU 2 performs the target internal EGR amount setting means, target cam phase setting means, phase control means, actual cam phase detection means, valve closing timing calculation means, target lift setting means, lift control means, target internal It corresponds to an EGR amount correcting means, an upper limit setting means and a target lift restricting means.

  FIG. 8 is a flowchart showing an internal EGR amount control process executed by the ECU 2. This process is executed every predetermined time. First, in step 1 (illustrated as “S1”, the same applies hereinafter), a target internal EGR amount that is a target of the internal EGR amount is searched by searching a map (not shown) according to the engine speed NE and the required torque PMCMD. INEGRCMD is calculated.

  Next, the corrected target internal EGR amount CINEGR is calculated by correcting the target internal EGR amount INEGRCMD using the gas state equation (PV = nRT) according to the detected exhaust gas temperature TEX and the exhaust gas pressure PEX ( Step 2).

  Next, a target cam phase CAEXCMD that is the target of the exhaust cam phase CAEX is calculated by searching a map (not shown) according to the calculated corrected target internal EGR amount CINEGR and the engine speed NE (step 3). . Next, the phase control input U_CAEX is calculated according to the calculated target cam phase CAEXCMD and the actual exhaust cam phase CAEX (step 4), and the solenoid valve 54 is driven according to the calculated phase control input U_CAEX (step). 5). As described above, the exhaust cam phase CAEX is controlled to become the target cam phase CAEXCMD.

  Next, a valve closing crank angle CAEXVC corresponding to the valve closing timing of the exhaust valve 7 is calculated by searching a table (not shown) according to the corrected target internal EGR amount CINEGR (step 6), and the valve closing operation is performed. A target rotation angle SAAEXCMD that is a target of the rotation angle SAAEX of the control shaft 71 is calculated according to the crank angle CAEXVC and the exhaust cam phase CAEX (step 7). Next, limit processing is performed on the calculated target rotation angle SAAEXCMD (step 8).

  FIG. 9 is a flowchart showing the limit processing of the target rotation angle SAAEXCMD. In this process, first, in step 21, the upper limit value SAAEXLMT of the target rotation angle SAAEXCMD is calculated by searching the table shown in FIG. 10 based on the exhaust cam phase CAEX. As described above, since the variable exhaust lift mechanism 70 is of a type in which the opening timing of the exhaust valve 7 is advanced as the exhaust lift increases, the upper limit value SAAEXLMT is set when the exhaust valve 7 ends the expansion stroke. It is set so that it doesn't start to open long before. Therefore, in this table, the upper limit value SAAEXLMT is set to a smaller value because the valve opening timing of the exhaust valve 7 is advanced as the exhaust cam phase CAEX is advanced.

  Next, it is determined whether or not the target rotation angle SAAEXCMD is equal to or smaller than the upper limit value SAAEXLMT (step 22). If the determination result is YES, the present process is terminated, while if NO and SAAEXCMD> SAAEXLMT, the target rotation angle SAAEXCMD is set to the upper limit value SAAEXLMT (step 23), and the present process is terminated.

  Returning to FIG. 8, in step 9 following step 8, the lift control input U_SAAEX is calculated according to the rotation angle SAAEX and the target rotation angle SAAEXCMD. Next, the actuator 80 is driven according to the lift control input U_SAAEX (step 10). As described above, the rotation angle SAAEX is controlled to be the target rotation angle SAAEXCMD.

  As described above, according to the present embodiment, the target cam phase CAEXCMD is calculated according to the target internal EGR amount INEGRCMD, and the target rotation angle SAAEXCMD, that is, the target lift of the exhaust valve 7 is closed with the exhaust cam phase CAEX. It is calculated according to the valve crank angle CAEXVC. As described above, since the exhaust cam phase CAEX is used as one of the parameters when setting the target lift of the exhaust valve 7, the response of the hydraulic exhaust cam phase variable mechanism 50 is the electric exhaust lift variable mechanism 70. Therefore, even when the convergence of the exhaust cam phase CAEX to the target cam phase CAEXCMD is delayed due to the response delay of the exhaust cam phase variable mechanism 50, the actual exhaust cam phase CAEX at that time is used as a parameter. The moving angle SAAEXCMD can be calculated, and therefore the internal EGR amount can be controlled with high accuracy.

  Further, since the target internal EGR amount INEGRCMD is corrected according to the exhaust temperature TEX and the exhaust pressure PEX, the internal EGR amount can be more appropriately controlled while compensating for the influence of the exhaust temperature TEX and the exhaust pressure PEX.

  Furthermore, since the upper limit value SAAEXLMT of the target rotation angle SAAEXCMD of the control shaft 71 is calculated based on the exhaust cam phase CAEX, it is possible to avoid that the exhaust valve 7 starts to open considerably before the end of the expansion stroke. it can. As a result, a large loss of pressure in the cylinder 3a during the expansion stroke can be prevented, and the output of the engine 3 can be secured.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the exhaust temperature and the exhaust pressure as parameters for calculating the corrected target internal EGR amount CINEGR are directly detected by the respective sensors, but are estimated according to the operating state of the engine and the like. May be. In the embodiment, the target internal EGR amount is calculated according to the engine speed NE and the required torque PMCMD, but the calculation method is not limited to this. For example, the target internal EGR amount may be calculated in accordance with both such that the temperature in the cylinder becomes the target temperature. Further, in the embodiment, the fuel injection mode is a direct injection type in which the fuel is directly injected into the cylinder, but it may be a port injection type in which the fuel is injected into the intake pipe, or both types are used in combination. You may have done.

  Further, the embodiment is an example in which the present invention is applied to a gasoline engine mounted on a vehicle, but the present invention is not limited thereto, and may be applied to various engines such as a diesel engine other than a gasoline engine, Further, the present invention can also be applied to engines other than those for vehicles, for example, marine vessel propulsion engines such as outboard motors having a crankshaft arranged vertically. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

It is a figure which shows schematically the internal EGR control apparatus of this invention with an internal combustion engine. It is a figure which shows a part of internal EGR control apparatus. It is a schematic diagram which shows schematic structure of an exhaust cam phase variable mechanism. It is a figure which shows the valve lift curve of an exhaust valve when an exhaust cam phase is set to the most retarded angle value (solid line) and the most advanced angle value (two-dot chain line) by the exhaust cam phase variable mechanism. It is a schematic diagram which shows schematic structure of an exhaust lift variable mechanism. It is a perspective view which shows schematic structure of an exhaust lift variable mechanism. It is a figure which shows the change state of the exhaust lift by an exhaust lift variable mechanism. It is a flowchart which shows the control processing of the amount of internal EGR. It is a flowchart which shows a limit process. It is an example of the table for calculating the upper limit used by the process of FIG.

Explanation of symbols

1 Internal EGR control device 2 ECU (target internal EGR amount setting means, target cam phase setting means, phase control means, actual
Cam phase detection means, valve closing timing calculation means, target lift setting means,
Control means, target internal EGR amount correction means, upper limit setting means, and target
Lift limiting means)
3 Engine 3a Cylinder 3d Crankshaft 7 Exhaust valve 9 Exhaust cam 22 Cam angle sensor (actual cam phase detection means)
24 Exhaust temperature sensor (exhaust gas temperature acquisition means)
25 Exhaust pressure sensor (exhaust gas pressure acquisition means)
50 Exhaust cam phase variable mechanism 70 Exhaust lift variable mechanism CAEX Exhaust cam phase (actual cam phase)
TEX exhaust temperature (exhaust gas temperature)
PEX Exhaust pressure (exhaust gas pressure)
SAAEXCMD target rotation angle (target lift of exhaust valve)
SAAEXLMT upper limit value INEGRCMD target internal EGR amount CINEGR corrected target internal EGR amount CAEXCMD target cam phase CAEXVC valve closing crank angle (exhaust valve closing timing)

Claims (3)

The exhaust cam phase that is the phase of the exhaust cam that drives the exhaust valve with respect to the crankshaft is changed by the exhaust cam phase variable mechanism, and the lift of the exhaust valve is changed by the exhaust lift variable mechanism, thereby An internal EGR control device for an internal combustion engine for controlling an internal EGR that leaves
Target internal EGR amount setting means for setting a target internal EGR amount that is a target of the internal EGR amount;
Target cam phase setting means for setting a target cam phase as a target of the exhaust cam phase according to the set target internal EGR amount;
Phase control means for controlling the exhaust cam phase variable mechanism so that the exhaust cam phase becomes the target cam phase;
An actual cam phase detecting means for detecting an actual exhaust cam phase as an actual cam phase;
A valve closing timing calculating means for calculating a valve closing timing of the exhaust valve according to the target internal EGR amount;
Target lift setting means for setting a target lift of the exhaust valve in accordance with the detected actual cam phase and the calculated valve closing timing;
Lift control means for controlling the variable exhaust lift mechanism so that the lift of the exhaust valve becomes the target lift;
Exhaust gas temperature acquisition means for acquiring the temperature of the exhaust gas discharged from the internal combustion engine;
A target internal EGR amount correcting means for correcting the target internal EGR amount according to the acquired temperature of the exhaust gas,
The target cam phase setting means sets the target cam phase according to the corrected target internal EGR amount corrected by the target internal EGR amount correction means,
The internal EGR control device for an internal combustion engine, wherein the valve closing timing calculating means calculates a valve closing timing of the exhaust valve according to the correction target internal EGR amount . It further comprises exhaust gas pressure acquisition means for acquiring the pressure of the exhaust gas,
2. The internal EGR control device for an internal combustion engine according to claim 1, wherein the target internal EGR amount correction unit corrects the target internal EGR amount in accordance with the acquired exhaust gas pressure . 3. Upper limit value setting means for setting an upper limit value of the target lift based on the actual cam phase;
The internal EGR control device for an internal combustion engine according to claim 1 or 2, further comprising target lift limiting means for limiting the target lift to be equal to or less than the set upper limit value .

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