JP2010007538A - Engine controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine controller capable of reducing the fuel consumption in good performance by raising the excess air factor in the condition that the mechanical compression ratio is high. <P>SOLUTION: An engine 1 is constructed so that the mechanical compression ratio defined from the gap capacity and piston stroke capacity, the lift characteristics of a suction valve, and the excess air factor of a fuel mixture gas in a combustion chamber are variable. The engine controller 3 is equipped with a lift characteristics control means 300. In the high compression ratio condition in which the mechanical compression ratio takes a certain value on the higher side than the central value of the variation range, the lift characteristics control means 300 controls the lift characteristics of the suction valve 123 so that the actual compression ratio in case the excess air factor is the first value, is lower than in case the factor is a second value which lies below the first. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine control device that controls the operation of an engine.

  Conventionally, an engine having a so-called variable compression ratio mechanism and a variable valve mechanism is known (for example, Japanese Patent Application Laid-Open Nos. 2003-193872, 2004-218522, 2007-239550, (See JP 2007-303423, etc.).

  The variable compression ratio mechanism changes the gap volume (for example, see Japanese Patent Application Laid-Open No. 2004-218522 etc.) or changes the piston stroke volume (for example, see Japanese Patent Application Laid-Open No. 2007-239550 etc.). And the mechanical compression ratio (expansion ratio) defined as a value obtained by dividing the sum of the piston stroke volume and the clearance volume by a gap volume.

  In the low load operation region, since the intake air amount is small, the temperature and pressure of the gas in the combustion chamber at the compression top dead center are low, and the combustion stability is poor. Therefore, the compression ratio is controlled to be high. This stabilizes combustion. Moreover, since the expansion ratio becomes high, the thermal efficiency can be improved and the fuel consumption can be reduced. On the other hand, in the high load operation region, the intake air amount increases and the gas temperature in the combustion chamber rises, so that abnormal combustion (knocking) is likely to occur. Therefore, the compression ratio is controlled to be low. Thereby, the output is improved while knocking is suppressed. As described above, the high compression ratio is controlled in the low load operation region, and the low compression ratio is controlled in the high load operation region.

  The variable valve mechanism is configured to be able to change the lift characteristics (timing and lift amount) of the intake valve. Regarding the valve timing, as is well known, intake efficiency is highest when the closing timing of the intake valve is set slightly behind the intake bottom dead center due to the inertia of the intake air, etc. ( The amount of retardation at which such maximum efficiency is obtained varies depending on the engine speed and the like. Therefore, the actual compression ratio can be lowered by shifting the valve closing timing from the timing at which the intake efficiency is maximized (for example, by delaying the valve closing timing more greatly). Here, the actual compression ratio is an effective compression ratio with respect to intake air. Typically, the volume of the combustion chamber at the start of compression of intake air is divided by the volume of the combustion chamber at the end of compression. Value.

Conventionally, a lean burn technique for performing combustion on the lean side (the excess air ratio is greater than 1) from the stoichiometric air-fuel ratio is known (see, for example, JP-A-2007-239550). This lean burn is normally performed in a low load operation region, and has effects such as improvement of fuel consumption performance.
JP 2003-193872 A JP 2004-218522 A JP 2007-239550 A JP 2007-303423 A JP 2006-328969 A

  For example, in a configuration including the variable compression ratio mechanism and capable of lean burn operation (for example, see Japanese Patent Application Laid-Open No. 2007-239550), the high compression ratio operation and lean burn operation are performed in the low load operation region as described above. Can be done. For this reason, when the lean burn operation is performed in a high compression ratio state, the NOx concentration in the gas discharged from the combustion chamber increases due to an increase in the compression end temperature accompanying the increase in the compression ratio.

  As described above, when the NOx concentration increases due to the high compression ratio operation, the NOx occlusion performance of the exhaust gas purifying catalyst device reaches its limit early. Therefore, it is necessary to perform a so-called rich spike process (a process for temporarily setting the air-fuel ratio of the fuel mixture to be richer than the stoichiometric air-fuel ratio) for regenerating the catalyst performance at a relatively high frequency. Then, the fuel consumption reduction effect due to the high compression ratio (and lean burn) operation is offset by the rich spike processing.

  The present invention has been made to address such problems. That is, an object of the present invention is to satisfactorily reduce fuel consumption by increasing the excess air ratio while the mechanical compression ratio is high.

Means for Solving the Problems and Effects of the Invention

  The engine control device of the present invention includes a mechanical compression ratio (defined from the gap volume and the piston stroke volume as described above), lift characteristics of the intake valve (for example, the closing timing of the intake valve), and fuel in the combustion chamber. It is configured to control the operation of an engine configured to be able to change the excess air ratio (air-fuel ratio) of the air-fuel mixture.

  The mechanical compression ratio is changed, for example, by relatively moving a crankcase in which a crankshaft is rotatably supported and a cylinder block having a cylinder head fixed to an upper end portion along the center axis of the cylinder. obtain. Alternatively, the mechanical compression ratio can be changed by changing the bending state of the connecting rod when the connecting rod (member connecting the piston and the crankshaft) is configured to be bent.

  A feature of the present invention resides in that the engine control device includes a lift characteristic control means for controlling the lift characteristic as follows.

  That is, in the present invention, the lift characteristic control means is configured such that the excess air ratio is the first in a high compression ratio state in which the mechanical compression ratio is a predetermined value on a higher compression ratio side than a median value in the variable range. The lift characteristic is controlled so that the actual compression ratio is lower when the value is one than when the excess air ratio is a second value lower than the first value.

  For example, in the high compression ratio state, the stoichiometric combustion in which the excess air ratio is 1 when the excess air ratio is greater than 1 (for example, 1.1 or more) and the first value is lean combustion. The lift characteristic is controlled so that the actual compression ratio becomes lower than the time.

  According to such a configuration, even when the mechanical compression ratio is set to the high compression ratio state, an increase in the compression end temperature is suppressed by reducing the actual compression ratio. For this reason, the fuel consumption can be reduced satisfactorily by increasing the excess air ratio in the high compression ratio state. That is, for example, lean burn operation can be performed without reducing the fuel consumption reduction effect in a state where the mechanical compression ratio is high.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings.

  In addition, the description about the following embodiment is specific to the extent possible, merely an example of the embodiment of the present invention in order to satisfy the description requirement (description requirement / practicability requirement) of the specification required by law. It is only what is described in. Therefore, as will be described later, it is quite natural that the present invention is not limited to the specific configurations of the embodiments described below. Modifications to the embodiments are listed together at the end, as insertions during the description of the embodiment impede understanding of the description of the consistent embodiment.

<Overall system configuration>
FIG. 1 is a schematic diagram showing an overall configuration of a system S (vehicle or the like) to which an embodiment of the present invention is applied. This system S is equipped with an in-line multiple cylinder engine 1 (note that FIG. 1 is a side sectional view of the engine 1 taken along a plane orthogonal to the cylinder arrangement direction). An intake / exhaust passage 2 is connected to the engine 1. The engine control device 3 of the present embodiment is configured to control the operation of the engine 1.

<Engine>
The engine 1 includes a cylinder block 11, a cylinder head 12, a crankcase 13, and a variable compression ratio mechanism 14.

  The cylinder block 11 is formed with a cylinder bore 111 that is a substantially cylindrical through hole. A piston 112 is accommodated inside the cylinder bore 111 so as to be capable of reciprocating along a cylinder center axis CCA that is a center axis of the cylinder bore 111.

  A cylinder head 12 is joined to the upper end of the cylinder block 11 (the end of the cylinder block 11 on the top dead center side of the piston 112). The cylinder head 12 is fixed to the upper end portion of the cylinder block 11 with a bolt or the like (not shown) so as not to move relative to the cylinder block 11.

  In the lower end portion of the cylinder head 12, a plurality of concave portions are provided at positions corresponding to the upper end portions of the cylinder bores 111. That is, in the state where the cylinder head 12 is joined and fixed to the cylinder block 11, the space inside the cylinder bore 111 above the top surface of the piston 112 (on the cylinder head 12 side) and the inside (lower side) of the above-described recess. ), A combustion chamber CC is formed. An intake port 121 and an exhaust port 122 are formed in the cylinder head 12 so as to communicate with the combustion chamber CC.

  The cylinder head 12 is also provided with an intake valve 123, an exhaust valve 124, a variable intake valve timing device 125, a variable exhaust valve timing device 126, and an injector 127.

  The intake valve 123 is a valve for controlling the communication state between the intake port 121 and the combustion chamber CC. The exhaust valve 124 is a valve for controlling the communication state between the exhaust port 122 and the combustion chamber CC.

  The variable intake valve timing device 125 and the variable exhaust valve timing device 126 are configured to change the actual compression ratio by changing the opening / closing timing of the intake valve 123 and the exhaust valve 124. Since the specific configurations of the variable intake valve timing device 125 and the variable exhaust valve timing device 126 are well known, description thereof will be omitted.

  The injector 127 is configured to inject fuel to be supplied into the combustion chamber CC into the intake port 121.

  A crankshaft 131 is rotatably supported in the crankcase 13. The crankshaft 131 is disposed in parallel with the cylinder arrangement direction. The crankshaft 131 is connected to the piston 112 via a connecting rod 132 so as to be rotationally driven based on reciprocal movement along the cylinder central axis CCA of the piston 112.

  The variable compression ratio mechanism 14 of the present embodiment changes the clearance volume by moving the joined body of the cylinder block 11 and the cylinder head 12 relative to each other along the cylinder center axis CCA with respect to the crankcase 13. Thus, the mechanical compression ratio can be changed.

  The variable compression ratio mechanism 14 has the same configuration as that described in Japanese Patent Application Laid-Open Nos. 2003-206871 and 2007-85300. Therefore, in this specification, detailed explanation of this mechanism is omitted, and only an outline is explained.

  The variable compression ratio mechanism 14 includes a connection mechanism 141 and a drive mechanism 142. The coupling mechanism 141 is configured to couple the cylinder block 11 and the crankcase 13 so as to be movable relative to each other along the cylinder center axis CCA. The drive mechanism 142 includes a motor, a gear mechanism, and the like, and is configured to move the cylinder block 11 and the crankcase 13 relative to each other along the cylinder center axis CCA (that is, along the vertical direction in the drawing). ing.

<Intake and exhaust passage>
The intake / exhaust passage 2 includes an intake passage 201 including an intake manifold and a surge tank, and an exhaust passage 202 including an exhaust manifold. The intake passage 201 is connected to an intake port 121, and the exhaust passage 202 is connected to an exhaust port. 122 is connected.

  A throttle valve 203 is interposed in the intake passage 201. The throttle valve 203 is configured to be rotationally driven by a throttle valve actuator 204 composed of a DC motor.

  An intake flow control valve (SCV) 205 is provided in the intake passage 201 between the throttle valve 203 and the injector 127. The intake flow control valve 205 is configured to be rotationally driven by an SCV actuator 206 composed of a DC motor. The intake flow control valve 205 has a function of a swirl control valve and / or a tumble control valve, and an SCV actuator 206 can be ignited well in the combustion chamber CC even with an extremely lean fuel mixture. Is configured to stratify the fuel mixture in the combustion chamber CC by controlling the flow state of the intake air (fuel mixture) flowing into the intake port 121 and the combustion chamber CC.

  The exhaust passage 202 is a passage for exhaust gas discharged from the combustion chamber CC via the exhaust port 122. An upstream catalyst 207 and a downstream catalyst 208 are interposed in the exhaust passage 202. The upstream side catalyst 207 and the downstream side catalyst 208 include a three-way catalyst having an oxygen storage function therein, and are configured to purify HC, CO, and NOx in the exhaust gas. The upstream catalyst 207 is provided upstream of the downstream catalyst 208 in the exhaust gas flow direction.

<Engine control device>
The engine control device 3 includes an engine electronic control unit (hereinafter referred to as “ECU 300”) 300 that constitutes the lift characteristic control means of the present invention.

  The ECU 300 includes a CPU 301, a ROM 302, a RAM 303, a backup RAM 304, an interface 305, and a bus 306. The CPU 301, ROM 302, RAM 303, backup RAM 304, and interface 305 are connected to each other via a bus 306.

  The ROM 302 stores in advance a routine (program) executed by the CPU 301, tables (look-up tables, maps), parameters, and the like that are referred to when the routine is executed. The RAM 303 is configured to temporarily store data as necessary when the CPU 301 executes a routine. The backup RAM 304 is configured so that data is stored when the CPU 301 executes a routine with the power turned on, and the stored data can be retained even after the power is shut off.

  The interface 305 is electrically connected to various sensors and output units described later, and is configured to transmit signals from these to the CPU 301. The interface 305 is electrically connected to operation parts such as the variable intake valve timing device 125, the variable exhaust valve timing device 126, the injector 127, the drive mechanism 142, and the like for operating these operation units. An operation signal can be transmitted from the CPU 301 to these operation units. That is, the engine control device 3 receives a signal from the above-described sensor or the like via the interface 305, and sends the above-described operation signal to each operation unit based on the calculation result of the CPU 301 corresponding to the signal. It is configured.

<< Various sensors >>
The cooling water temperature sensor 311 is attached to the cylinder block 11. The cooling water temperature sensor 311 is configured to output a signal corresponding to the cooling water temperature Tw in the cylinder block 11.

  The crank position sensor 312 is attached to the crankcase 13. The crank position sensor 312 is configured to output a waveform signal having a pulse corresponding to the rotation angle of the crankshaft 131. Specifically, the crank position sensor 312 outputs a signal having a narrow pulse every time the crankshaft 131 rotates 10 ° and a signal having a wide pulse every time the crankshaft 131 rotates 360 °. It is configured. That is, the crank position sensor 312 is configured to output a signal corresponding to the engine speed Ne.

  The intake cam position sensor 313 and the exhaust cam position sensor 314 are attached to the cylinder head 12. The intake cam position sensor 313 outputs a signal having a waveform having a pulse corresponding to a rotation angle of an intake camshaft (not shown) for reciprocating the intake valve 123 (included in the variable intake valve timing device 125). It is configured. Similarly, the exhaust cam position sensor 314 is configured to output a waveform signal having a pulse corresponding to a rotation angle of an exhaust camshaft (not shown).

  The air flow meter 315, the intake air temperature sensor 316, and the throttle position sensor 317 are attached to the intake passage 201. The air flow meter 315 is configured to output a signal corresponding to an intake air flow rate Ga that is a mass flow rate of intake air flowing through the intake passage 201. The intake air temperature sensor 316 is configured to output a signal corresponding to the temperature of the intake air. The throttle position sensor 317 is configured to output a signal corresponding to the rotational phase of the throttle valve 203 (throttle valve opening TA).

  The upstream air-fuel ratio sensor 318a and the downstream air-fuel ratio sensor 318b are interposed in the exhaust passage 202. The upstream air-fuel ratio sensor 318a is disposed upstream of the upstream catalyst 207 in the exhaust gas flow direction. The downstream air-fuel ratio sensor 318b is disposed downstream of the upstream catalyst 207 in the flow direction of the exhaust gas and upstream of the downstream catalyst 208 in the same direction.

  The upstream air-fuel ratio sensor 318a is an all-region type air-fuel ratio sensor having a relatively linear output characteristic in a wide air-fuel ratio range. Specifically, the upstream air-fuel ratio sensor 318a is composed of a limiting current type oxygen concentration sensor.

  The downstream air-fuel ratio sensor 318b is an air-fuel ratio sensor that has an output characteristic that is substantially constant on the rich side and lean side of the stoichiometric air-fuel ratio, but rapidly changes before and after the stoichiometric air-fuel ratio. Specifically, the downstream air-fuel ratio sensor 318b is composed of a solid electrolyte type zirconia oxygen sensor.

  The accelerator opening sensor 319 is configured to output a signal corresponding to the operation amount Accp of the accelerator pedal 320 operated by the driver.

  The vehicle speed output unit 321 generates a vehicle speed signal by processing a rectangular wave pulse signal from a wheel speed sensor (not shown), and outputs the signal to the ECU 300.

  The shift information output unit 322 outputs shift information corresponding to an operation state (shift state) of a transmission mechanism (not shown) to the ECU 300.

<Overview of operation>
In the system S of the present embodiment, the engine control device 3 performs the following processing.

<< Air-fuel ratio control >>
A target air-fuel ratio is set based on operating conditions such as vehicle speed, shift state, engine load, cooling water temperature, throttle valve opening, and the like. Subsequently, a basic value (basic fuel injection amount) of the fuel amount injected from the injector 127 is acquired based on the set target air-fuel ratio, the intake air flow rate, and the like.

  If the predetermined feedback control condition is not satisfied, such as when the upstream air-fuel ratio sensor 318a and the downstream air-fuel ratio sensor 318b are not sufficiently warmed up immediately after the engine 1 is started, the engine is opened based on the basic fuel injection amount. Loop control is performed (in this open loop control, learning control based on a learning correction coefficient can be performed).

  When the feedback control condition is satisfied after the activation of these sensors, the basic fuel injection amount is feedback-corrected based on the outputs from the upstream air-fuel ratio sensor 318a and the downstream air-fuel ratio sensor 318b, so that the injector 127 The actual fuel injection amount (command fuel injection amount) from is acquired. Further, based on the outputs from the upstream air-fuel ratio sensor 318a and the downstream air-fuel ratio sensor 318b, air-fuel ratio learning for obtaining the learning correction coefficient in the above-described open loop control is performed.

  The target air-fuel ratio described above is normally set to the stoichiometric air-fuel ratio. On the other hand, if necessary, the target air-fuel ratio can be set to a value shifted from the stoichiometric air-fuel ratio to the rich side or the lean side.

  For example, after the warm-up is completed, the lean burn operation is performed when the vehicle is in the low to medium load operation region within a predetermined vehicle speed and rotation speed range (which differ depending on the shift state described above). During the lean burn operation, the target air-fuel ratio is set to about 16 (the excess air ratio is 1.1) or more. On the other hand, at the time of rapid acceleration or the like, the target air-fuel ratio is set richer than the stoichiometric air-fuel ratio (the excess air ratio is less than 1). In other cases, the target air-fuel ratio is set to the stoichiometric air-fuel ratio (the excess air ratio is 1) (stoichiometric operation).

<< Compression ratio control >>
A mechanical compression ratio is set by the variable compression ratio mechanism 14 based on the operating state. In other words, as described above, in the low load operation region, the mechanical compression ratio is set high, so that combustion stability and fuel efficiency can be improved. On the other hand, in the high-load operation region, the mechanical compression ratio is set low, so that the output is improved while knocking is suppressed.

  Here, in this embodiment, when the lean burn operation is performed in a state where the mechanical compression ratio is set higher (than the median value in the variable range), the stoichiometric operation in the same mechanical compression ratio setting state is performed. The valve closing timing of the intake valve 123 is set by the variable intake valve timing device 125 (actual compression ratio control by intake VVT) so that the actual compression ratio becomes lower than the time and NOx generation is suppressed.

<Details of operation>
Next, a specific example of the operation of the engine control device 3 of the present embodiment shown in FIG. 1 will be described using a flowchart. In the following description and drawings, “step” is abbreviated as “S”.

  The CPU 301 executes the VVT control routine 200 shown in FIG. 2 at every predetermined timing. When this routine 200 is started, first, in S210, operating conditions such as vehicle speed, shift state, engine load, cooling water temperature, throttle valve opening, and the like are acquired.

  Next, in S220, based on these operating conditions, the mechanical compression ratio set by another routine based on the operating conditions, and a predetermined map stored in the ROM 302, the intake valve 123 is set. The valve closing timing θc is set. As described above, the valve closing timing θc set by this map is set to a timing slightly delayed from the intake bottom dead center. That is, the map for setting the valve closing timing θc is obtained in advance by experiment or computer simulation so that the intake efficiency becomes the highest in accordance with the above-described operation state or the like.

  Subsequently, in S230, it is determined whether or not the mechanical compression ratio ε is equal to or less than the median value εc in the variable range.

  When the mechanical compression ratio ε is equal to or less than the median value εc (S230 = Yes), the routine is temporarily terminated with the closing timing θc of the intake valve 123 set as described above. That is, the intake valve 123 is opened and closed at the valve closing timing θc set in S220 described above.

  When the mechanical compression ratio ε is higher than the median value εc (S230 = No), the process proceeds to S240, and it is determined whether or not a predetermined lean burn operation condition is satisfied. When the lean burn operation condition is not satisfied (S240 = No), the process does not proceed to S250, and this routine is temporarily ended.

  On the other hand, when the lean burn operation condition is satisfied (S240 = Yes), the process proceeds to S250, and then this routine is temporarily ended. In S250, the valve closing timing θc is further retarded from the timing set in S220. That is, the valve closing timing θc is further away from the intake bottom dead center than the timing set in S220. As a result, in the high mechanical compression ratio lean burn operation, the valve closing timing θc is controlled so that the actual compression ratio becomes lower than in the stoichiometric operation in the same mechanical compression ratio setting state, and the compression end temperature rises. Suppression and NOx generation amount suppression are realized.

<Effects of Configuration of Embodiment>
As described in the above description of the operation, in the present embodiment, the lean burn operation in which the excess air ratio exceeds 1 (for example, 1.1 or more) at a predetermined mechanical compression ratio on the high compression ratio side. However, the lift characteristic of the intake valve 123 is controlled so that the actual compression ratio becomes lower than during the stoichiometric operation where the excess air ratio is 1.

  As a result, even when the mechanical compression ratio is set high during the lean burn operation, the actual compression ratio is lowered, so that the increase in the compression end temperature is suppressed and the generation of NOx is suppressed. Therefore, the lean burn operation can be performed in a state where the mechanical compression ratio is set high without reducing the fuel consumption reduction effect (without interposing an excessive rich spike process). That is, fuel consumption can be reduced satisfactorily by increasing the excess air ratio while the mechanical compression ratio is set high.

<List of examples of modification>
Note that, as described above, the above-described embodiment is merely an example of a specific configuration of the present invention considered to be the best by the applicant at the time of filing of the present application. It should not be limited at all by the embodiment. Therefore, it goes without saying that various modifications can be made to the specific configurations shown in the above-described embodiments within a range that does not change the essential part of the present invention.

  Hereinafter, some modifications will be exemplified. Here, in the following description of the modified example, components having the same configurations and functions as the components in the above-described embodiment are given the same name and the same reference numerals in the modified example. And And about description of the said component, description in the above-mentioned embodiment shall be used suitably in the range which is not inconsistent.

  However, it goes without saying that the modified examples are not limited to the following. The limited interpretation of the present invention based on the description of the above-described embodiment and the following modifications unfairly harms the interests of the applicant (especially rushing the application under the principle of prior application), but improperly imitates the imitator. It is beneficial and not allowed.

  Further, it goes without saying that the configuration of the above-described embodiment and the configuration described in each of the following modifications can be applied in an appropriate combination within a technically consistent range.

  (1) The present invention can be applied to gasoline engines, diesel engines, methanol engines, bioethanol engines, and any other types of internal combustion engines. The number of cylinders, cylinder arrangement system (series, V type, horizontally opposed), and fuel injection system (port injection, in-cylinder direct injection) are not particularly limited.

  (2) The present invention is not limited to the specific operation mode described above. For example, in the description of the flowchart described above, when the compression ratio state is high (S230 = Yes) but not during lean burn operation (S240 = No), the valve closing timing θc is retarded by a smaller amount than Δθc in S250. May be. Thereby, generation | occurrence | production of NOx during the stoichiometric operation in a low-medium load can be suppressed effectively.

  Alternatively, instead of the median value εc in S230, a predetermined value εh on the higher compression ratio side than the median value εc, or a predetermined value εl slightly lower than the median value εc may be used.

  (3) The configuration of the engine 1 including the variable compression ratio mechanism 14 is not limited to that of the above-described embodiment. For example, even if the engine 1 is configured such that the connecting rod 132 has a multi-link structure and the mechanical compression ratio is changed by changing the bending state of the connecting rod 132, the present invention is good. Applies to

  Further, the change in the actual compression ratio is not limited to the change in the closing timing of the intake valve 123.

  (4) Generally, when the air-fuel ratio becomes 16 or more (the excess air ratio is 1.1 or more), the amount of NOx generated decreases as the air-fuel ratio becomes leaner (as the excess air ratio increases). Therefore, the lean burn operation is preferably performed so that the air-fuel ratio is 16 or more (the excess air ratio is 1.1 or more).

  Also, the higher the mechanical compression ratio, the higher the lean limit. Therefore, it is preferable that the lean burn operation is performed so that the excess air ratio increases as the mechanical compression ratio increases.

  (5) Other modifications not specifically mentioned are also naturally included in the technical scope of the present invention within the scope not changing the essential part of the present invention.

  Furthermore, in each element constituting the means for solving the problems of the present invention, elements expressed functionally and functionally include the specific structures disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function.

1 is a schematic diagram illustrating an overall configuration of a system (vehicle or the like) to which an embodiment of the present invention is applied. 2 is a flowchart showing a specific example of the operation (VVT control) of the engine control apparatus of the present embodiment shown in FIG. 1.

Explanation of symbols

S ... System 1 ... Engine 11 ... Cylinder block 111 ... Cylinder bore 12 ... Cylinder head 125 ... Variable intake valve timing device 127 ... Injector 13 ... Crankcase 131 ... Crankshaft 132 ... Connecting rod 14 ... Variable compression ratio mechanism 141 ... Connection mechanism 142 ... Drive mechanism 2 ... intake / exhaust passage 205 ... intake flow control valve 3 ... engine control device 300 ... ECU

Claims (4)

In an engine control apparatus for controlling an operation of an engine configured to be able to change a mechanical compression ratio defined from a clearance volume and a piston stroke volume, a lift characteristic of an intake valve, and an excess air ratio of a fuel mixture in a combustion chamber. ,
In the high compression ratio state in which the mechanical compression ratio is a predetermined value on the higher compression ratio side than the median value in the variable range, the excess air ratio is the same when the excess air ratio is the first value. An engine control device comprising: lift characteristic control means for controlling the lift characteristic so that the actual compression ratio is lower than when the second value is lower than the first value. The engine control device according to claim 1,
In the high compression ratio state, the lift characteristic control means is configured to perform the lean combustion, which is the first value in which the excess air ratio is greater than 1, than the stoichiometric combustion in which the excess air ratio is 1. An engine control device that controls the lift characteristics so that the actual compression ratio becomes low. The engine control device according to claim 2,
The engine control device according to claim 1, wherein the first value is 1.1 or more. The engine control device according to any one of claims 1 to 3,
The engine control device, wherein the lift characteristic control means controls a closing timing of the intake valve.

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