JP4915535B2 - Control device for variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine (variable compression ratio internal combustion engine) including a mechanical compression ratio changing mechanism capable of changing a mechanical compression ratio.

Conventionally, a variable compression ratio internal combustion engine capable of changing the mechanical compression ratio according to the operating state has been proposed. Such a variable compression ratio internal combustion engine changes the mechanical compression ratio based on, for example, one of the following methods.
(1) The movement amount of the piston (movement distance when the piston moves from the bottom dead center position to the top dead center position) is changed using the link mechanism (see, for example, Patent Document 1).
(2) The inclination angle of the cylinder block with respect to the crankcase is changed.
(3) The cylinder block is moved in the axial direction of the cylinder with respect to the crankcase (see, for example, Patent Document 2 and Patent Document 3).
(4) The distance between the piston and the crankshaft is changed (see, for example, Patent Document 4).

Further, an in-cylinder pressure sensor for detecting the in-cylinder pressure (pressure in the combustion chamber) of the variable compression ratio internal combustion engine is provided, and an actual mechanical compression ratio (actual machine compression ratio) εact is calculated based on the detected in-cylinder pressure. An apparatus that uses a mechanical compression ratio εact for engine control is known (see, for example, Patent Document 5).
JP 2004-239147 A JP 2003-206871 A JP 2007-303423 A JP-A-2-163429 JP 2005-48621 A

  However, if the detected in-cylinder pressure is significantly different from the true in-cylinder pressure due to a change in the output characteristics of the in-cylinder pressure sensor, the calculated actual mechanical compression ratio εact is significantly different from the true mechanical compression ratio. In some cases, the engine is not properly controlled.

  The control device of the present invention is made to cope with the above problem, and is applied to a variable compression ratio internal combustion engine having a mechanical compression ratio changing mechanism. The mechanical compression ratio changing mechanism changes the mechanical compression ratio according to the instruction signal. The mechanical compression ratio is a ratio of “the volume of the combustion chamber when the piston is at the bottom dead center position” to “the volume of the combustion chamber when the piston is at the top dead center position”.

  The control device further includes an instruction unit, an in-cylinder pressure sensor, an actual mechanical compression ratio acquisition unit, an expected mechanical compression ratio acquisition unit, a control mechanical compression ratio acquisition unit, and a control unit.

The instruction means determines a target mechanical compression ratio according to the operating state of the engine, and instructs the mechanical compression ratio changing mechanism to make the mechanical compression ratio of the engine coincide with the determined target mechanical compression ratio. Is sent out.
The in-cylinder pressure sensor is configured to detect an in-cylinder pressure that is a pressure in the combustion chamber.
The actual mechanical compression ratio acquisition means acquires the mechanical compression ratio of the engine as an actual mechanical compression ratio based on the in-cylinder pressure detected by the in-cylinder pressure sensor.
The expected mechanical compression ratio acquisition means is configured to control the engine based on one of an instruction signal sent to the mechanical compression ratio changing mechanism and an amount related to an operation amount of the mechanical compression ratio changing mechanism based on the instruction signal. The mechanical compression ratio is acquired as the expected mechanical compression ratio.
The control mechanical compression ratio acquisition means acquires a predetermined mechanical compression ratio as a control mechanical compression ratio.
The control means controls the engine based on the control mechanical compression ratio.

  According to this, the instruction signal is sent to the mechanical compression ratio changing mechanism so that the mechanical compression ratio of the engine matches the “target mechanical compression ratio that changes according to the operating state of the engine”. On the other hand, the mechanical compression ratio of the engine is acquired as the “actual mechanical compression ratio” based on the in-cylinder pressure detected by the in-cylinder pressure sensor. On the other hand, at least one of “the instruction signal sent to the mechanical compression ratio changing mechanism” and “the amount related to the operation amount of the mechanical compression ratio changing mechanism based on the instruction signal sent to the mechanical compression ratio changing mechanism” Is obtained as the “expected mechanical compression ratio”. “The amount related to the operation amount of the mechanical compression ratio changing mechanism based on the instruction signal sent to the mechanical compression ratio changing mechanism” is, for example, when the actuator of the mechanical compression ratio changing mechanism is an electric motor, The amount of rotation. In the following, “the instruction signal sent to the mechanical compression ratio changing mechanism” and “the amount related to the operation amount of the mechanical compression ratio changing mechanism based on the instruction signal sent to the mechanical compression ratio changing mechanism” are: Also collectively referred to as “mechanical compression ratio change instruction amount”.

  By the way, if the in-cylinder pressure sensor is normal, the actual mechanical compression ratio and the expected mechanical compression ratio are substantially equal. Therefore, the control mechanical compression ratio acquisition means sets the “actual machine compression ratio” to “control machine” when “the magnitude of the difference between the actual machine compression ratio and the expected mechanical compression ratio” is smaller than a predetermined threshold. Acquired as “compression ratio”.

  In contrast, if the detected in-cylinder pressure is significantly different from the true in-cylinder pressure due to changes in the characteristics of the in-cylinder pressure sensor, the difference between the calculated actual mechanical compression ratio and the true mechanical compression ratio. Becomes larger. As a result, the difference between the actual mechanical compression ratio and the expected mechanical compression ratio is also increased. Therefore, when the magnitude of the difference between the actual mechanical compression ratio and the predicted mechanical compression ratio is greater than the predetermined threshold, the control mechanical compression ratio acquisition unit is configured to display “the actual mechanical compression ratio and the predicted mechanical compression ratio. The “predetermined mechanical compression ratio” is used as the “control mechanical compression ratio”. The “predetermined mechanical compression ratio between the actual machine compression ratio and the expected mechanical compression ratio” may be, for example, an average value of the actual machine compression ratio and the expected mechanical compression ratio, It may be a load average value with the predicted mechanical compression ratio, and, as will be described later, a value obtained by adding a first predetermined value (positive value) to the predicted mechanical compression ratio or a second predetermined value from the predicted mechanical compression ratio. It may be a value obtained by subtracting the value (positive value).

  The control mechanical compression ratio obtained in this way is “the actual mechanical compression ratio obtained when the magnitude of the difference between the actual mechanical compression ratio and the expected mechanical compression ratio is larger than the predetermined threshold”. It is considered to be closer to the “true mechanical compression ratio”. And the said control means performs control of an engine based on the mechanical compression ratio for control acquired in this way. Therefore, the engine control can be brought close to appropriate control (control desired for a true mechanical compression ratio). As a result, for example, the occurrence of misfire due to excessive ignition timing retardation due to the control mechanical compression ratio being excessive with respect to the true mechanical compression ratio, and the control mechanical compression ratio being the true mechanical compression ratio. Therefore, it is possible to avoid the occurrence of knocking due to the excessive advance of the ignition timing due to being too small.

In this case, the control mechanical compression ratio acquisition means is
If the magnitude of the difference between the actual machine compression ratio and the expected machine compression ratio is greater than the predetermined threshold, and the actual machine compression ratio is greater than the expected machine compression ratio, the expected machine compression ratio is A value obtained by adding a predetermined value is obtained as the control mechanical compression ratio;
When the magnitude of the difference between the actual machine compression ratio and the expected machine compression ratio is larger than the predetermined threshold value, and the actual machine compression ratio is smaller than the expected machine compression ratio, A value obtained by subtracting two predetermined values may be obtained as the control mechanical compression ratio.

  The first predetermined value and the second predetermined value may be the same or different from each other. Further, the first predetermined value and the second predetermined value may be the same as or different from the predetermined threshold value.

in addition,
The instruction means sets a target compression ratio for abnormality determination that temporarily changes the target compression ratio by a minute amount when the magnitude of the difference between the actual mechanical compression ratio and the expected mechanical compression ratio is larger than the predetermined threshold. Including means,
Furthermore, the control device comprises:
When the target compression ratio is temporarily changed by the abnormality determination target compression ratio setting means, the presence / absence of abnormality of the mechanical compression ratio changing mechanism is determined based on the actual mechanical compression ratio and the expected mechanical compression ratio. It is preferable to include a compression ratio change mechanism abnormality determination means for performing the above.

  According to this, when the magnitude of the difference between the actual mechanical compression ratio and the expected mechanical compression ratio is larger than the predetermined threshold, the target compression ratio is temporarily changed, and accordingly, the mechanical compression ratio change is performed. An instruction signal for changing the mechanical compression ratio is sent to the mechanism.

  At this time, if the mechanical compression ratio changing mechanism does not operate due to a failure, the mechanical compression ratio is not actually changed. Therefore, the actual in-cylinder pressure does not change. As a result, the in-cylinder pressure detected by the in-cylinder pressure sensor does not change, and the actual mechanical compression ratio acquired based on the detected in-cylinder pressure does not change. On the other hand, since the mechanical compression ratio change instruction amount changes, the expected mechanical compression ratio acquired based on the mechanical compression ratio change instruction amount changes. Therefore, when the actual mechanical compression ratio does not substantially change and the predicted mechanical compression ratio changes, there is a high possibility that the mechanical compression ratio changing mechanism is in a failure state in which the mechanical compression ratio cannot be changed.

  On the other hand, when the mechanical compression ratio changing mechanism is normal and the mechanical compression ratio is actually changed, the actual mechanical compression ratio acquired based on the in-cylinder pressure detected by the in-cylinder pressure sensor is “change in instruction signal”. Indicates a change in the direction opposite to the direction of the expected mechanical compression ratio (for example, the increasing direction) (for example, the decreasing direction) expected (for example, the decreasing direction), it is highly likely that the in-cylinder pressure sensor has failed.

  Accordingly, as in the above configuration, if an instruction signal for changing the mechanical compression ratio is temporarily sent to the mechanical compression ratio changing mechanism, and the state of change between the actual mechanical compression ratio and the expected mechanical compression ratio at that time is evaluated. It is possible to determine whether the mechanical compression ratio changing mechanism is malfunctioning or the in-cylinder pressure sensor is malfunctioning.

  Embodiments of a control apparatus for a variable compression ratio internal combustion engine according to the present invention will be described below with reference to the drawings.

(Constitution)
FIG. 1 is a schematic cross-sectional view of a variable compression ratio internal combustion engine 10 to which a control device according to an embodiment of the present invention (hereinafter, also simply referred to as “control device”) is applied.

  This engine 10 is a multi-cylinder (in-line 4 cylinder), piston reciprocating type, spark ignition type, gasoline internal combustion engine. The engine 10 also includes a mechanical compression ratio changing mechanism 15 for changing the mechanical compression ratio. Although FIG. 1 shows a cross section of a specific cylinder (first cylinder), other cylinders have the same configuration.

  The engine 10 includes a crankcase 11, an oil pan 12, a cylinder block 13 and a cylinder head portion 14.

  The crankcase 11 rotatably supports the crankshaft 11a. The oil pan 12 is fixed to the crankcase 11 below (lower) the crankcase 11. The oil pan 12, together with the crankcase 11, forms a space for accommodating the crankshaft 11a, lubricating oil, and the like.

  The cylinder block 13 is disposed above the crankcase 11. The cylinder block 13 includes a plurality (four cylinders) of hollow cylindrical cylinders (cylinder bores) 13a. The piston 13b has a substantially cylindrical shape and is accommodated in the cylinder 13a. The piston 13b is connected to the crankshaft 11a by a connecting rod 13c. As will be described later, the cylinder block 13 moves in the direction of the axis CC of the cylinder 13a with respect to the crankcase 11 (hereinafter also referred to as “vertical direction”), thereby changing the mechanical compression ratio of the engine 10. It has become. The mechanical compression ratio is “the combustion chamber volume when the piston 13b is at the bottom dead center (intake bottom dead center) position relative to the combustion chamber volume when the piston 13b is at the top dead center (compression top dead center) position”. Defined as ratio.

  The cylinder head portion 14 is disposed above the cylinder block 13 and is fixed to the cylinder block 13. The cylinder head portion 14 is formed with a cylinder head lower surface 14a that forms the upper surface of the combustion chamber, an intake port 14b that communicates with the combustion chamber, and an exhaust port 14c that communicates with the combustion chamber.

  Further, the cylinder head portion 14 includes an intake valve 14d for opening and closing the intake port 14b, an intake camshaft 14e having an intake cam for driving the intake valve 14d, a variable intake timing device 14f, an exhaust valve 14g for opening and closing the exhaust port 14c, and an exhaust valve. An exhaust cam shaft 14h having an exhaust cam for driving 14g, an ignition plug 14i, an igniter 14j including an ignition coil, and the like are accommodated. The igniter 14j generates an ignition spark in the spark generating part of the spark plug 14i exposed in the combustion chamber in response to an ignition instruction signal from an electric control device described later. A head cover 14k is fixed to the upper portion of the cylinder head portion 14.

  The variable intake timing device 14f is a well-known device as described in, for example, Japanese Patent Application Laid-Open No. 2007-303423 (Patent Document 3). The variable intake timing device 14f includes a hydraulic oil supply control valve (not shown) and a hydraulic pump (not shown). By supplying and discharging the hydraulic oil by these, the phase of the intake cam relative to the intake cam shaft 14e is advanced by a desired amount. And can be retarded. In this example, the period during which the intake valve 14d is open (the valve opening crank angle width) is constant. Accordingly, when the intake valve opening timing is advanced or retarded by a predetermined angle by the variable intake timing device 14f, the closing timing of the intake valve 14d is also advanced or retarded by the same predetermined angle.

  In the following, the case where the intake valve opening timing is at the most retarded angle by the variable intake timing device 14f is used as a reference, and the crank angle from the reference to the intake valve opening timing actually controlled is determined as the intake valve advance angle. This is referred to as VVT. Therefore, the intake valve advance angle VVT is a value corresponding to the start timing of the compression action, which is the intake valve closing timing.

  The engine 10 includes a mechanical compression ratio changing mechanism 15 for changing the mechanical compression ratio. This mechanical compression ratio changing mechanism 15 is, for example, disclosed in Japanese Patent Application Laid-Open No. 2003-206871 (Patent Document 2), Japanese Patent Application Laid-Open No. 2007-303423 (Patent Document 3), Japanese Patent Application Laid-Open No. 2007-321589, and Japanese Patent Application Laid-Open No. 2004. This is a well-known mechanism similar to the mechanism disclosed in Japanese Patent No. 218522. A brief description will be given below with reference to FIGS.

  The mechanical compression ratio changing mechanism 15 includes a case side bearing forming portion 15a, a block side bearing forming portion 15b, and a shaft-like driving portion 15c.

  As shown in FIG. 2, the case-side bearing forming portion 15a includes a plurality of first bearing forming portions 15a1 and a plurality of second bearing forming portions 15a2.

  Each of the first bearing forming portions 15 a 1 is formed on the left and right vertical wall portions of the crankcase 11. Each of the first bearing forming portions 15a1 forms a semicircular recess. A vertically long hole 15a3 penetrating the vertical wall portion is formed between the first bearing forming portions 15a1 adjacent to each other.

  Each of the second bearing forming portions 15a2 includes a semicircular concave portion having the same diameter as the semicircular concave portion formed by the first bearing forming portion 15a1. Each of the second bearing forming portions 15a2 is formed on each of the first bearing forming portions 15a1 so that the semicircular concave portion of the first bearing forming portion 15a1 and the semicircular concave portion of the second bearing forming portion 15a2 face each other. It is a cap fixed by a bolt.

  The plurality of first bearing forming portions 15a1 and the plurality of second bearing forming portions 15a2 form a plurality of cylindrical bearing holes (cam housing holes) H1 shown in FIG. The central axes of the plurality of bearing holes H1 are arranged on one straight line. The axis of the bearing hole H <b> 1 extends in a direction parallel to the arrangement direction of the plurality of cylinders 13 a in a state where the cylinder block 13 is disposed on the crankcase 11.

  Each of the block-side bearing forming portions 15b is a member having a substantially rectangular parallelepiped shape and having a cylindrical bearing hole H2 as shown in FIGS. The block-side bearing forming portion 15 b is accommodated in a vertically elongated hole 15 a 3 formed in the vertical wall portion of the crankcase 11 in a state where the cylinder block 13 is disposed on the crankcase 11. The block side bearing forming portion 15 b is bolted to the left and right side wall portions of the cylinder block 13. With such a configuration, the bearing holes H1 and the bearing holes H2 are alternately arranged along the arrangement direction of the cylinders 13a.

  The length of the vertically long hole 15a3 in the cylinder axis CC direction is set longer than the length of the block-side bearing forming portion 15b in the cylinder axis CC direction. As a result, the block-side bearing forming portion 15b is integrated with the cylinder block 13 and is movable in the cylinder axis CC direction with respect to the crankcase 11.

  When all the block side bearing forming portions 15b are fixed to the cylinder block 13, the central axes of the bearing holes H2 provided in each of the block side bearing forming portions 15b are arranged on one straight line. The axis of the bearing hole H2 extends in a direction parallel to the arrangement direction of the plurality of cylinders 13a. The distance between the axis of the bearing hole H2 formed in the left side wall portion of the cylinder block 13 and the axis of the bearing hole H2 formed in the right side wall portion of the cylinder block 13 is the bearing formed on the left side of the crankcase 11. The distance between the axis of the hole H1 and the axis of the bearing hole H1 formed on the right side of the crankcase 11 is the same.

  On the other hand, the shaft-like drive part 15c is inserted through the bearing hole H1 and the bearing hole H2. As shown in FIG. 2 and FIG. 4 which is a cross-sectional view of the shaft-like drive unit 15c, the shaft-like drive unit 15c includes a small-diameter shaft portion 15c1, a fixed cylindrical portion 15c2, and a rotating cylindrical portion 15c3. Yes.

  The fixed cylindrical portion 15c2 is fixed to the shaft portion 15c1 while being eccentric with respect to the central axis of the shaft portion 15c1. The fixed cylindrical portion 15c2 is a cylindrical member having a regular circular cam profile having a larger diameter than the shaft portion 15c1 and the same diameter as the bearing hole H1. The fixed cylindrical portion 15c2 is accommodated in a bearing hole H1 provided in the case side bearing forming portion 15a of the crankcase 11. The fixed cylindrical portion 15c2 rotates while contacting the wall surface of the bearing hole H1 around its central axis.

  The rotating cylindrical portion 15c3 is rotatably attached to the shaft portion 15c1 while being eccentric with respect to the central axis of the shaft portion 15c1. The rotating cylindrical portion 15c3 is a cylindrical member having a regular circular cam profile having a larger diameter than the shaft portion 15c1 and the fixed cylindrical portion 15c2 and the same diameter as the bearing hole H2. The rotating cylindrical portion 15c3 is accommodated in a bearing hole H2 provided in the block side bearing forming portion 15b fixed to the cylinder block 13. The rotating cylindrical portion 15c3 rotates while contacting the wall surface of the bearing hole H2. The pair of left and right shaft drive portions 15c, the left and right bearing holes H1, and the left and right bearing holes H2 have a mirror image relationship with each other with respect to a plane passing through the plurality of cylinder axes CC.

  Furthermore, as shown in FIG. 2, each of the shaft-like drive portions 15c includes a gear 15c4 in the vicinity of the center position in the axial direction. The gear 15c4 is fixed to the shaft portion 15c1 so as to be eccentric with respect to the central axis of the shaft portion 15c1 and to be coaxial with the fixed cylindrical portion 15c2 (accordingly, the bearing hole H1). That is, the rotation center axis of the gear 15c4 coincides with the center axis of the fixed cylindrical portion 15c2. A pair of worm gears (not shown) are engaged with the pair of gears 15c4. The worm gear is attached to the output shaft of a single motor (not shown) (see motor 15M shown in FIG. 5) fixed to the crankcase 11. The pair of worm gears have spiral grooves that rotate in opposite directions. Accordingly, when the motor is rotated, the pair of shaft-like drive portions 15c rotate in directions opposite to each other around the central axis of each fixed cylindrical portion 15c2.

  FIG. 4 is a diagram conceptually illustrating the movement of the shaft-like drive unit 15 c located on the right side when viewed from the front surface Pf side of the crankcase 11 and the cylinder block 13. For example, as shown in FIG. 4A, when the center c2 of the fixed cylindrical portion 15c2, the center c1 of the shaft portion 15c1 and the center c3 of the rotating cylindrical portion 15c3 are located on the same straight line in this order, A distance D between the crankcase 11 (center of the bearing hole H1) and the cylinder block 13 (center of the bearing hole H2) is a distance D1, which is the maximum distance. Therefore, the volume of the combustion chamber when the piston 13b is at the top dead center position is increased. As a result, the mechanical compression ratio of the internal combustion engine 10 becomes low (small).

  When the fixed cylindrical portion 15c2 and the shaft portion 15c1 rotate around the central axis of the fixed cylindrical portion 15c2 by driving the motor from the state shown in FIG. 4A, the state shown in FIG. Become. At this time, the distance D becomes the distance D2. Further, when the motor is driven in the same rotational direction from the state shown in FIG. 4B, when the fixed cylindrical portion 15c2 and the shaft portion 15c1 rotate around the central axis of the fixed cylindrical portion 15c2, (C ). At this time, the distance D becomes the distance D3. The distance D3 is smaller than the distance D2, and the distance D2 is smaller than the distance D1. Therefore, the mechanical compression ratio in the state shown in FIG. 4B is higher (larger) than the mechanical compression ratio in the state shown in FIG. The mechanical compression ratio in the state shown in FIG. 4C is higher (larger) than the mechanical compression ratio in the state shown in FIG.

  The mechanical compression ratio changing mechanism 15 having such a structure is in response to an instruction signal (driving signal) Dr from a later-described electric control device to a mechanical compression ratio changing actuator (for example, an electric motor 15M such as a stepper motor). The distance between the cylinder block 13 and the crankcase 11 is changed, and the mechanical compression ratio of the engine 10 is changed.

  The engine 10 includes a fuel injection valve (injector) 16 as shown in FIG. The fuel injection valve 16 is fixed to a branch portion of the intake manifold 21. In response to the fuel injection instruction signal, the fuel injection valve 16 injects the fuel of the instruction injection amount included in the injection instruction signal into the intake port 14b. As shown in FIG. 5, the fuel injection valve 16 is provided for each cylinder.

  As shown in FIG. 5, the engine 10 includes an intake system 20 for supplying gasoline mixture to the combustion chamber, and an exhaust system 30 for releasing exhaust gas from the combustion chamber to the outside. .

  The intake system 20 includes the intake manifold 21, the intake pipe (intake duct) 22, the air filter 23, the throttle valve 24, and the throttle valve actuator 24a.

  The intake manifold 21 includes a plurality of branch portions 21a and a surge tank 21b. One end of each branch portion 21a is connected to each intake port 14b, and the other end of each branch portion 21a is connected to a surge tank 21b. The intake pipe 22 is connected to the surge tank 21b. The intake manifold 21 and the intake pipe 22 form an intake passage together with the intake ports 14b. The air filter 23 is provided at the end of the intake pipe 22. The throttle valve 24 is rotatably provided in the intake pipe 22 so as to change the opening cross-sectional area of the intake passage formed by the intake pipe 22 by rotating. The throttle valve actuator (throttle valve driving means) 24a is formed of a DC motor, and rotates the throttle valve 24 in response to an instruction signal from the electric control device 50.

  The exhaust system 30 includes an exhaust manifold 31, an exhaust pipe (exhaust pipe) 32, and a catalyst (three-way catalyst) 33.

  The exhaust manifold 31 includes a plurality of branch portions 31a connected to each exhaust port 14c, and a collective portion 31b in which the branch portions 31a are gathered. The exhaust pipe 32 is connected to the collective portion 31 b of the exhaust manifold 31. The exhaust manifold 31 and the exhaust pipe 32 constitute an exhaust path together with the exhaust ports 14c. In the present specification, a route through which the exhaust gas formed by the collecting portion 31b of the exhaust manifold 31 and the exhaust pipe 32 passes is also referred to as an “exhaust passage” for convenience.

  Further, as shown in FIG. 5, the control device includes a hot-wire air flow meter 41, a throttle position sensor 42, an engine speed sensor 43, a stroke sensor 44, an in-cylinder pressure sensor 45, an upstream air-fuel ratio sensor 46, a downstream air-conditioner. A fuel ratio sensor 47, an accelerator opening sensor 48, and a neutral switch 49 are provided.

The air flow meter 41 detects the mass flow rate of intake air flowing through the intake pipe 22 and outputs a signal representing the mass flow rate (intake air amount per unit time of the engine 10) Ga.
The throttle position sensor 42 detects the opening of the throttle valve 24 and outputs a signal representing the throttle valve opening TA.

  The engine rotation speed sensor 43 outputs a signal having a narrow pulse every time the intake camshaft rotates 5 ° and a wide pulse every time the intake camshaft rotates 360 °. A signal output from the engine rotation speed sensor 43 is converted into a signal representing the engine rotation speed NE by the electric control device 50. Further, the electric control device 50 acquires the crank angle (absolute crank angle) of the engine 10 based on signals from the engine rotation speed sensor 43 and a cam position sensor (not shown).

The stroke sensor 44 measures the distance between the crankcase 11 (for example, the upper end of the crankcase 11) and the cylinder block 13 (for example, the lower end of the cylinder block 13), and outputs a signal representing the distance ST. Yes. The electric control device 50 can estimate the mechanical compression ratio of the engine 10 based on the distance ST.
The in-cylinder pressure sensor 45 detects the pressure in the combustion chamber (in-cylinder pressure) and outputs a signal representing the pressure P.

The upstream air-fuel ratio sensor 46 is disposed in either the exhaust manifold 31 or the exhaust pipe 32 (that is, the exhaust passage) at a position between the collecting portion 31 b of the exhaust manifold 31 and the catalyst 33.
The downstream air-fuel ratio sensor 47 is disposed in the exhaust pipe 32 (main passage portion) downstream of the catalyst 33.
The upstream air-fuel ratio sensor 46 and the downstream air-fuel ratio sensor 47 are the air-fuel ratio of exhaust gas (detected gas) flowing through the portion in the exhaust passage where the upstream air-fuel ratio sensor 46 and the downstream air-fuel ratio sensor 47 are respectively disposed. Output values corresponding to each are output.

The accelerator opening sensor 48 detects the operation amount of the accelerator pedal Ap operated by the driver, and outputs a signal indicating the operation amount Accp of the accelerator pedal Ap.
The neutral switch 49 generates an ON signal (Hi signal) when the shift position of the transmission of the vehicle on which the engine 10 is mounted is the neutral position, and an OFF signal (Lo signal) when the shift position is other than the neutral position. Is supposed to occur.

  The electric control device 50 includes a CPU, a ROM, a RAM, a backup RAM that stores data while the power is turned on and holds the stored data while the power is shut off, and an interface including an AD converter. This is a known microcomputer.

  The interface of the electric control device 50 is connected to the sensors 41 to 49 and the like, and supplies signals from the sensors 41 to 49 to the CPU. Further, the interface of the electric control device 50 is an actuator of the variable intake timing device 14f, the igniter 14j of each cylinder, the fuel injection valve 16 of each cylinder, the throttle valve actuator 24a, and the mechanical compression ratio changing mechanism 15 according to instructions from the CPU. An instruction signal and / or a drive signal is transmitted to 15M or the like.

(Operation)
Next, the operation of the control device configured as described above will be described. The CPU of the electric control device 50 repeatedly executes the compression ratio control routine shown in FIG. 6 every elapse of a predetermined time. Accordingly, when the predetermined timing comes, the CPU starts the process from step 600 and proceeds to step 610 to determine whether or not the value of the determination execution flag (abnormality determination execution flag) XCK is “0”.

  The determination execution flag XCK indicates that control for abnormality determination described later should be executed when the value is “1”, and control for abnormality determination is performed when the value is “0”. Indicates that there is no need to execute. The value of the determination execution flag XCK is set to “0” in an initial routine that is executed when an ignition key switch (not shown) of the vehicle on which the engine 10 is mounted is changed from OFF to ON. It has become.

  Now, it is assumed that the engine 10 has just been started, and that both the in-cylinder pressure sensor 45 and the mechanical compression ratio changing mechanism 15 (actuator 15M) are operating normally. In this case, the value of the determination execution flag XCK is set to “0” in the initial routine. Therefore, the CPU makes a “Yes” determination at step 610 to proceed to step 620. In step 620, the CPU adds the current load KL and the current load KL to the target mechanical compression ratio table Mapεtgt (KL, NE), in which “the relationship between the load KL and the engine rotational speed NE and the target mechanical compression ratio εtgt” is predetermined. By applying the engine speed NE, the current target mechanical compression ratio εtgt is determined. The CPU adopts the accelerator pedal operation amount Accp as the load KL.

  Next, the CPU proceeds to step 630 to send an instruction signal Dr to the mechanical compression ratio changing actuator 15M so that the actual mechanical compression ratio matches the target mechanical compression ratio εtgt. More specifically, the CPU stores in advance a function g representing the relationship between the target mechanical compression ratio εtgt and the instruction signal Dr. Therefore, the CPU determines the instruction signal Dr (= g (εtgt)) based on the target mechanical compression ratio εtgt and the function g, and sends the instruction signal Dr to the actuator 15M. Thereafter, the CPU proceeds to step 695 to end the present routine tentatively.

  Further, the CPU repeatedly executes the compression ratio calculation routine shown in FIG. 7 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU starts processing from step 700 and proceeds to step 710 to calculate the actual mechanical compression ratio εact based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45. The actual machine compression ratio εact is calculated according to the principle described below.

  As shown in FIG. 8A, when the intake valve 14d is closed (when the crank angle is INC before compression top dead center), the in-cylinder pressure is before Pinc, compression top dead center. Assume that the in-cylinder pressure at a predetermined time after the INC before compression top dead center (when the crank angle is a before compression top dead center) is Pa. Further, as shown in FIG. 8B, the stroke volume of the piston 13b from the time when the intake valve 14d is closed to the compression top dead center (the volume of the space in which the piston 13b moves) is Vinc *, the crank angle. Assume that the stroke volume of the piston 13b from the time when A is before the compression top dead center to the compression top dead center is Va *, and the combustion chamber volume at the compression top dead center TDC is Vc. FIG. 8C is a diagram schematically showing INC before compression top dead center and a before compression top dead center with respect to compression top dead center TDC and intake bottom dead center BDC.

At this time, the combustion chamber volume Vinc when the intake valve 14d is closed and the combustion chamber volume Va when the crank angle is a before compression top dead center a are obtained by the following equations (1) and (2), respectively. It is done.

As is well known, since the compression stroke after the intake valve 14d is closed and the gas in the combustion chamber starts to be compressed can be considered as an adiabatic compression process, P · V ^κ (P is the in-cylinder pressure, V Is the combustion chamber volume and κ is the specific heat ratio of the gas) is constant during the compression stroke. Therefore, the following equation (3) is established.

The following equation (4) is obtained from the equations (1) to (3).

If this equation (4) is modified, equation (5) is obtained, and if equation (5) is modified, equation (6) is obtained. The CPU acquires the combustion chamber volume Vc at the compression top dead center based on the in-cylinder pressure (Pa, Pinc) and the combustion chamber volume (Va *, Vinc *) according to the equation (6). The in-cylinder pressure Pa and Pinc are acquired based on the output of the in-cylinder pressure sensor 45. The combustion chamber volumes Va * and Vinc * are known.

On the other hand, the following expression (7) is a definition expression of the mechanical compression ratio. In the equation (7), Vd * is a stroke volume of the piston 13b from the intake bottom dead center BDC to the compression top dead center TDC. This Vd * is also known.

  Therefore, the CPU calculates the actual machine compression ratio εact by substituting the combustion chamber volume Vc obtained by the equation (6) and the known stroke volume Vd * into the equation (7).

  Next, the CPU proceeds to step 720 in FIG. 7 to acquire the “expected mechanical compression ratio εest” based on the instruction signal (command value) Dr and the function f sent to the actuator 15M for changing the mechanical compression ratio ( εest = f (Dr)). The function f is an inverse function of the function g. That is, the expected mechanical compression ratio εest is a mechanical compression ratio estimated from the instruction signal Dr that is a mechanical compression ratio change instruction amount. Thereafter, the CPU proceeds to step 795 to end the present routine tentatively.

  Further, the CPU repeatedly executes the compression ratio guard processing routine shown in FIG. 9 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU starts the process from step 900 and proceeds to step 905. From the “actual machine compression ratio εact acquired in step 710 of FIG. 7” to “step 720 of FIG. It is determined whether or not a value obtained by subtracting the acquired expected mechanical compression ratio εest is greater than a predetermined threshold value Ath. The threshold value Ath is a positive value.

  According to the above assumption, both the in-cylinder pressure sensor 45 and the mechanical compression ratio changing mechanism 15 (actuator 15M) are operating normally. In this case, the actual mechanical compression ratio εact and the expected mechanical compression ratio εest are substantially the same. That is, the value obtained by subtracting the expected mechanical compression ratio εest from the actual mechanical compression ratio εact is equal to or less than the threshold value Ath. Accordingly, the CPU makes a “No” determination at step 905 to proceed to step 910 to determine whether or not the value obtained by subtracting the actual mechanical compression ratio εact from the predicted mechanical compression ratio εest is greater than the threshold value Ath.

  According to the above assumption, the value obtained by subtracting the actual mechanical compression ratio εact from the expected mechanical compression ratio εest is also equal to or less than the threshold value Ath. Therefore, the CPU makes a “No” determination at step 910 to proceed to step 915 to store the actual machine compression ratio εact in the control machine compression ratio εcont. That is, the CPU employs the actual machine compression ratio εact as the control mechanical compression ratio εcont.

  Next, the CPU proceeds to step 920 and sets the value of the temporary abnormality flag Xkari to “0”. When the value of the temporary abnormality flag Xkari is “1”, it indicates that an abnormality has occurred in “any one of the in-cylinder pressure sensor 45 and the actuator 15M of the mechanical compression ratio changing mechanism 15”. When the value of the temporary abnormality flag Xkari is “0”, it indicates that no abnormality has occurred in any of them. Note that the value of the temporary abnormality flag Xkari is set to “0” in the above-described initial routine. Thereafter, the CPU proceeds to step 995 to end the present routine tentatively.

  In addition, the CPU repeatedly executes the abnormality determination start routine shown in FIG. 10 every elapse of a predetermined time. Accordingly, when the predetermined timing comes, the CPU starts the process from step 1000 and proceeds to step 1010 to determine whether or not the value of the temporary abnormality flag Xkari is “1”. At this time, the value of the temporary abnormality flag Xkari is set to “0” in the previous step 920. Therefore, the CPU makes a “No” determination at step 1010 to proceed to step 1095 to end the present routine tentatively.

  Further, the CPU repeatedly executes the abnormality determination execution routine shown in FIG. 11 every elapse of a predetermined time. Therefore, when the predetermined timing comes, the CPU starts the processing from step 1100 and proceeds to step 1110, where the predetermined time has elapsed since the current time “the value of the determination execution flag XCK has changed from“ 0 ”to“ 1 ”. It is determined whether it is “timing”. This predetermined time is set to a time longer than the time necessary for the actual mechanical compression ratio to coincide with the increased target mechanical compression ratio εtgt after the target mechanical compression ratio εtgt is increased by a minute amount Δε. . At this time, since the process of step 1060 in FIG. 10 is not executed, the value of the determination execution flag XCK is maintained at “0”. Therefore, the CPU makes a “No” determination at step 1110 to directly proceed to step 1195 to end the present routine tentatively.

  Further, the CPU repeatedly executes the engine control routine shown in FIG. 12 every elapse of a predetermined time. Therefore, when the predetermined timing comes, the CPU starts processing from step 1200 and proceeds to step 1210 to estimate the exhaust gas temperature Tgas. More specifically, the CPU stores the actual load KL and the control mechanical compression ratio at the present time in a table that defines the relationship between the load KL (accelerator pedal operation amount Accp), the control mechanical compression ratio εcont, and the exhaust gas temperature Tgas. By applying εcont, the current exhaust gas temperature Tgas is estimated. According to this table, the exhaust gas temperature Tgas is required to increase as the load KL increases. Further, according to this table, the exhaust gas temperature Tgas is required to decrease as the control mechanical compression ratio εcont increases.

Next, the CPU proceeds to step 1220 to update / determine the temperature (catalyst temperature, catalyst bed temperature) TempCCRO of the catalyst 33 according to the following equation (8). In the equation (8), γ is a predetermined constant larger than 0 and smaller than 1, TempCCRO (k) is the catalyst temperature TempCCRO before being updated, and TempCCRO (k + 1) is the catalyst temperature TempCCRO after being updated.

  Next, the CPU proceeds to step 1230 to determine the catalyst overheat prevention increase value KOTP. More specifically, the CPU applies the catalyst temperature TempCCRO estimated in step 1220 to a table that defines the relationship between the catalyst temperature TempCCRO and the catalyst overheat prevention increase value KOTP, thereby preventing the current catalyst overheat prevention. Determine the increase value KOTP. According to this table, in the region where the estimated catalyst temperature TempCCRO is equal to or lower than the threshold temperature (high temperature limit temperature) Tth, the catalyst overheat prevention increase value KOTP is set to 1.0. Further, according to this table, in the region where the estimated catalyst temperature TempCCRO is larger than the threshold temperature Tth, the catalyst overheat prevention increase value KOTP increases while taking a value larger than 1.0 as the estimated catalyst temperature TempCCRO is higher. Is set as follows.

Next, the CPU proceeds to step 1240 to determine the fuel injection amount Fi according to the following equation (9). In the equation (9), Mc is an intake air amount (in-cylinder intake air amount) sucked into a cylinder (fuel injection cylinder) that reaches an intake stroke. The in-cylinder intake air amount Mc is based on the intake air amount Ga measured by the air flow meter 41, the engine rotational speed NE obtained from the output signal from the engine rotational speed sensor 43, and the table MapMc (Ga, NE). Is calculated. stoich is the stoichiometric air-fuel ratio (for example, 14.6).

  As a result, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is matched with the stoichiometric air-fuel ratio in the region where the estimated catalyst temperature TempCCRO is equal to or lower than the threshold temperature Tth. Further, the amount of fuel supplied to the engine 10 increases as the catalyst temperature TempCCRO increases in a region where the estimated catalyst temperature TempCCRO is higher than the threshold temperature Tth. In other words, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is controlled to a richer air-fuel ratio as the catalyst temperature TempCCRO is higher in a region where the estimated catalyst temperature TempCCRO is higher than the threshold temperature Tth. Is done.

  Next, the CPU proceeds to step 1250 to determine the ignition timing Aig. Specifically, the CPU stores an ignition timing table MapAig (Mc, NE, εcont) that defines the relationship between the cylinder intake air amount Mc, the engine rotational speed NE, the control mechanical compression ratio εcont, and the ignition timing Aig. The ignition timing Aig is determined by applying the actual in-cylinder intake air amount Mc, the actual engine speed NE, and the current control mechanical compression ratio εcont. Thereafter, the CPU proceeds to step 1295 to end the present routine tentatively.

  Then, in a crank angle synchronization routine (not shown), when the crank angle of the fuel injection cylinder reaches a predetermined crank angle, the CPU supplies fuel of the fuel injection amount Fi from the fuel injection valve 16 provided for the fuel injection cylinder. Spray. Further, when the crank angle of the fuel injection cylinder coincides with the ignition timing Aig, the CPU generates a spark from the spark plug 14i of the fuel injection cylinder. Thus, the CPU uses the control mechanical compression ratio εcont for engine control such as fuel injection amount control and ignition timing control.

  Thereafter, a value obtained by subtracting “the expected mechanical compression ratio εest acquired based on the instruction signal Dr” from “the actual mechanical compression ratio εact acquired based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45” for some reason. It is assumed that (εact−εest) is larger than a predetermined threshold Ath.

  Also in this case, the CPU executes the routine shown in FIG. 7 to obtain the actual mechanical compression ratio εact based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45, and the mechanical compression ratio change instruction amount The expected mechanical compression ratio εest is acquired based on the instruction signal Dr.

  Further, in this case, when the CPU proceeds to step 905 following step 900 in FIG. 9, the CPU makes a “Yes” determination at step 905 to proceed to step 925, where the control mechanical compression ratio εcont is set to “expected mechanical compression ratio εest. Is stored as a value obtained by adding the value Ath as the first predetermined value (εest + Ath) ”. That is, the CPU adopts the value (εest + Ath) as the control mechanical compression ratio εcont. As a result, by executing the routine shown in FIG. 12, the fuel injection amount and the ignition timing are changed based on the value (εest + Ath) which is the control mechanical compression ratio εcont.

  Next, the CPU proceeds to step 930 in FIG. 9 to set the value of the temporary abnormality flag Xkari to “1”, proceeds to step 995, and once ends this routine.

  In this state, when the CPU starts the processing of the routine shown in FIG. 10 from step 1000, the CPU determines “Yes” in step 1010, and in step 1020, whether the driving state of the vehicle is “neutral state” or not. (Whether or not the signal from the neutral switch 49 is an ON signal). That is, in step 1020, the CPU determines whether or not the current driving state of the vehicle is a driving state in which a change in the driving state of the engine 10 does not affect the traveling of the vehicle.

  At this time, if the driving state of the vehicle is not in the neutral state, the CPU makes a “No” determination at step 1020 to proceed to step 1095 to end the present routine tentatively. On the other hand, if the driving state of the vehicle is in the neutral state, the CPU makes a “Yes” determination at step 1020 to proceed to step 1030 to determine whether or not the value of the determination execution flag XCK is “0”. To do.

  Since the value of the determination execution flag XCK remains “0” immediately after the engine 10 is started, the CPU makes a “Yes” determination at step 1030 to perform the processing of step 1040 to step 1060 described below in order. Proceed to 1095 to end the present routine tentatively. If “No” is determined in step 1030, the CPU proceeds directly from step 1030 to step 1095 to end the present routine tentatively.

Step 1040: The CPU stores the current actual machine compression ratio εact as the pre-change actual machine compression ratio εactold.
Step 1050: The CPU stores the current expected mechanical compression ratio εest as the pre-change expected mechanical compression ratio εestold.
Step 1060: The CPU sets the value of the determination execution flag XCK to “1”.

  As described above, when the actual mechanical compression ratio εact acquired based on the in-cylinder pressure P becomes larger than “the value obtained by adding the threshold Ath to the predicted mechanical compression ratio εest”, the control mechanical compression ratio εcont is determined as “the expected mechanical compression ratio. A value obtained by adding a first predetermined value Ath to εest ”(see step 925 in FIG. 9). Further, in this state, if the driving state of the vehicle is a neutral state, the value of the determination execution flag XCK is set to “1” (see step 1060 in FIG. 10).

  In this state, when the CPU starts the process from step 600 in FIG. 6 and proceeds to step 610, the CPU makes a “No” determination at step 610. Then, the CPU proceeds to step 640 and sets a value obtained by adding a minute amount Δε to the target mechanical compression ratio εtgt immediately before the value of the determination execution flag XCK is changed from “0” to “1” to a new target mechanical compression ratio εtgt. Store as. Thereafter, the CPU proceeds to step 630 to send an instruction signal Dr to the mechanical compression ratio changing actuator 15M so that the actual mechanical compression ratio matches the target mechanical compression ratio εtgt.

  The current time is immediately after the time when the value of the determination execution flag XCK is changed from “0” to “1”. Therefore, when the CPU proceeds to step 1110 in FIG. 11, the CPU makes a “No” determination at step 1110 to immediately proceed to step 1195 to end the present routine tentatively.

  After that, when a predetermined time has elapsed after the value of the determination execution flag XCK is changed from “0” to “1”, when the CPU starts processing from step 1100 in FIG. In step 1110, “Yes” is determined, and abnormality determination processing after step 1120 described later is performed.

  By the way, when the instruction signal Dr is changed so as to increase the actual mechanical compression ratio by a minute amount Δε, “currently expected mechanical compression ratio εest” obtained in step 720 of FIG. 7 and step 1050 of FIG. The difference (εest−εestold) from the stored “predicted mechanical compression ratio immediately before change of instruction signal Dr (predicted mechanical compression ratio before change) εestold” is larger than a predetermined threshold Cth (Cth> 0). However, if the mechanical compression ratio changing actuator 15M does not operate due to a failure, the trajectory of change of the actual in-cylinder pressure with respect to the crank angle does not change. Accordingly, the “current actual machine compression ratio εact” obtained in step 710 in FIG. 7 and the “actual machine compression ratio immediately before the change of the instruction signal Dr stored in step 1040 in FIG. 10 (actual machine compression ratio before change)” are stored. The absolute value | εact−εactold | of the difference from “εactold” is substantially 0 and is smaller than the predetermined threshold value Dth (Dth> 0).

  Therefore, in step 1120, the CPU determines whether or not the difference (εest−εestold) is larger than the threshold value Cth and whether the difference (εact−εactold) is between the threshold value −Dth and the threshold value Dth. When the condition in step 1120 is satisfied, the CPU makes a “Yes” determination in step 1120 to perform the processing in steps 1130 to 1150 described below. Thereafter, the CPU proceeds to step 1195 to end the present routine tentatively.

Step 1130: The CPU sets the value of the actuator abnormality flag XACTFail to “1”.
Step 1140: The CPU sets the value of the in-cylinder pressure sensor abnormality flag XCPSFFail to “0”.
Step 1150: The CPU sets the value of the determination execution flag XCK to “0”.
The CPU sets all the values of these flags to “0” in an initial routine (not shown).

  As described above, when the value obtained by subtracting the expected mechanical compression ratio εest from the actual mechanical compression ratio εact becomes larger than the threshold value Ath, the CPU sets the value of the temporary abnormality flag Xkari to “1”. Then, when the value of the temporary abnormality flag Xkari is set to “1” and the driving state of the vehicle becomes a neutral state, the CPU temporarily changes the target mechanical compression ratio εtgt and the instruction signal Dr (small amount). Increase by the amount Δε). When the actual mechanical compression ratio εact does not change as a result, the CPU determines that the mechanical compression ratio changing actuator 15M is out of order (the in-cylinder pressure sensor 45 is not abnormal), and an actuator abnormality flag is shown to indicate that. The value of XACTFail is set to “1”.

  On the other hand, when the CPU executes the process of step 1120, if the condition in step 1120 is not satisfied, the CPU makes a “No” determination in step 1120 to proceed to step 1160, where the difference (εest−εestold) is a threshold value. It is determined whether or not the difference is larger than Cth and the difference (εact−εactold) is equal to or smaller than a threshold −Dth.

  As described above, the present time is immediately after a predetermined time has elapsed since the instruction signal Dr was changed to increase the actual mechanical compression ratio by a minute amount Δε. Therefore, the difference (εest−εestold) is larger than the predetermined threshold Cth. At this time, if the in-cylinder pressure sensor 45 is normal, the difference (εact−εactold) should be a positive value. In other words, if the difference (εact−εactold) is equal to or less than the threshold −Dth, it can be considered that an abnormality has occurred in the in-cylinder pressure sensor 45.

  Therefore, if the condition of step 1160 is satisfied, the CPU makes a “Yes” determination at step 1160 to perform the processing of step 1170, step 1180, and step 1150 described below, and then proceeds to step 1195 to execute this routine. Exit once.

Step 1170: The CPU sets the value of the actuator abnormality flag XACTFail to “0”.
Step 1180: The CPU sets the value of the in-cylinder pressure sensor abnormality flag XCPSFFail to “1”.
Step 1150: The CPU sets the value of the determination execution flag XCK to “0”.

  As described above, when the value obtained by subtracting the expected mechanical compression ratio εest from the actual mechanical compression ratio εact becomes larger than the threshold value Ath, the CPU sets the value of the temporary abnormality flag Xkari to “1”. Then, when the value of the temporary abnormality flag Xkari is set to “1” and the driving state of the vehicle becomes a neutral state, the CPU temporarily changes the target mechanical compression ratio εtgt and the instruction signal Dr (small amount). Increase by the amount Δε). As a result, if the actual machine compression ratio εact shows a change in the opposite direction (in this case, an increase direction) and a change in this direction (in this case, a decrease direction), the cylinder It is determined that the internal pressure sensor 45 is abnormal (the mechanical compression ratio changing actuator 15M has not failed), and the value of the in-cylinder pressure sensor abnormal flag XCPSFFail is set to “1” to indicate that.

  If the condition of step 1160 is not satisfied, the CPU makes a “No” determination at step 1160 to proceed to step 1190 to set the value of the temporary abnormality flag Xkari to “0”. Thereafter, the CPU sets the value of the determination execution flag XCK to “0” in step 1150, and then proceeds to step 1195 to end the present routine tentatively.

  Next, for some reason, “the actual mechanical compression ratio εact acquired based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45” is subtracted from the “expected mechanical compression ratio εest acquired based on the instruction signal Dr”. A case where the value (εest−εact) becomes larger than the predetermined threshold Ath will be described.

  Also in this case, the CPU executes the routine shown in FIG. 7 to obtain the actual mechanical compression ratio εact based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45, and the mechanical compression ratio change instruction amount The expected mechanical compression ratio εest is acquired based on the instruction signal Dr.

  Further, in this case, when the CPU proceeds to step 905 following step 900 in FIG. 9, it determines “No” in step 905, determines “Yes” in subsequent step 910, and proceeds to step 935. In step 935, the CPU stores “the value obtained by subtracting the value Ath as the second predetermined value from the expected mechanical compression ratio εest (εest−Ath)” in the control mechanical compression ratio εcont. That is, the CPU adopts the value (εest−Ath) as the control mechanical compression ratio εcont. Thereafter, the CPU proceeds to step 930 to set the value of the temporary abnormality flag Xkari to “1”, proceeds to step 995, and once ends this routine.

  As a result, by executing the routine shown in FIG. 12, the fuel injection amount and the ignition timing are changed based on the value (εest−Ath) which is the control mechanical compression ratio εcont. Further, when the driving state of the vehicle becomes a neutral state, the value of the determination execution flag XCK is set to “1” in step 1060 of FIG. 10, and the instruction signal Dr is changed by the processing of step 640 and step 630 of FIG. It is done. Then, when the actual mechanical compression ratio εact does not change when the instruction signal Dr is temporarily changed, the CPU determines that the mechanical compression ratio changing actuator 15M has failed (the in-cylinder pressure sensor 45 is not abnormal). Then, the value of the actuator abnormality flag XACTFail is set to “1” so as to indicate that (see step 1120 to step 1140 in FIG. 11).

  In addition, when the instruction signal Dr is temporarily changed, the CPU determines that the in-cylinder pressure sensor 45 when the actual mechanical compression ratio εact indicates “change in the direction opposite to the direction expected by the change in the instruction signal Dr”. Is abnormal (the mechanical compression ratio changing actuator 15M has not failed), and the value of the in-cylinder pressure sensor abnormality flag XCPSFFail is set to “1” (steps 1160 to FIG. 11 in FIG. 11). (See step 1180).

  The CPU executes an in-cylinder pressure sensor disconnection determination routine (not shown) every predetermined time. In this disconnection determination routine, the CPU sets the value of the in-cylinder pressure sensor abnormality flag XCPSFFail to “1” when the “in-cylinder pressure P detected by the in-cylinder pressure sensor 45” does not change over a predetermined time. ing. Then, when the value of the cylinder pressure sensor abnormality flag XCPSFFail is “1”, the CPU stops the execution of the routine shown in FIG.

As described above, this control device
The target mechanical compression ratio εtgt is determined according to the operating state of the engine 10 and the mechanical compression ratio changing mechanism 15 (actuator 15M) is set so that the mechanical compression ratio of the engine 10 matches the “determined target mechanical compression ratio εtgt”. Instruction means for sending the instruction signal Dr (see steps 620 and 630 in FIG. 6);
An in-cylinder pressure sensor 45;
Actual mechanical compression ratio acquisition means (see step 710 in FIG. 7) for acquiring the mechanical compression ratio of the engine 10 as the actual mechanical compression ratio εact based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45;
Expected mechanical compression ratio acquisition means (see step 720 in FIG. 7) for acquiring the mechanical compression ratio of the engine 10 as the expected mechanical compression ratio εest based on the instruction signal Dr;
When the magnitude of the difference between the actual mechanical compression ratio εact and the expected mechanical compression ratio εest is smaller than a predetermined threshold Ath, the actual mechanical compression ratio εact is acquired as a control mechanical compression ratio εcont (steps 905 to 905 in FIG. 9). Step 915)), when the magnitude of the difference between the actual mechanical compression ratio εact and the predicted mechanical compression ratio εest is larger than the predetermined threshold Ath, “the actual mechanical compression ratio εact and the predicted mechanical compression ratio εest Control machine that obtains “εest + Ath (in the case of εact−εest> Ath) or εest−Ath (in the case of εest−εact> Ath)”, which is a “predetermined mechanical compression ratio between”, as a control mechanical compression ratio εcont Compression ratio acquisition means (see step 925 and step 935 in FIG. 9);
Control means for controlling the engine 10 based on the control mechanical compression ratio εcont (see the routine of FIG. 12);
It has.

  Therefore, even when the actual mechanical compression ratio εact deviates from the true mechanical compression ratio due to an abnormality of the in-cylinder pressure sensor 45, the engine 10 is “control mechanical compression ratio close to the true mechanical compression ratio”. Controlled based on As a result, the engine 10 can be properly controlled.

  The predicted mechanical compression ratio acquisition means (step 720 in FIG. 7) may be configured to acquire the predicted mechanical compression ratio εest based on the rotation amount of the electric motor 15M of the mechanical compression ratio changing mechanism 15, for example. Good. That is, the predicted mechanical compression ratio acquisition means (step 720 in FIG. 7) predicts based on “a quantity related to the operation amount of the mechanical compression ratio changing mechanism based on the instruction signal Dr (for example, the rotation amount of the electric motor)”. It may be configured to obtain the mechanical compression ratio εest.

Furthermore, in the control device,
When the magnitude of the difference between the actual mechanical compression ratio εact and the predicted mechanical compression ratio εest is larger than the predetermined threshold Ath, the instruction means indicates “the operating state of the engine 10 which is a factor for determining the target mechanical compression ratio εtgt” In a state in which the target mechanical compression ratio εtgt is temporarily changed by a minute amount Δε, the abnormality determination target compression ratio setting means (step 930 in FIG. 9, the routine in FIG. 10, the step 610 in FIG. See step 640),
Furthermore,
When the target compression ratio is temporarily changed by the abnormality determination target compression ratio setting means (see step 640 in FIG. 6 and the value of the determination execution flag XCK), the actual machine compression ratio εact and the prediction A compression ratio change mechanism abnormality determination unit (see step 1120 in FIG. 11) is provided for determining whether or not the mechanical compression ratio change mechanism 15 is abnormal based on the mechanical compression ratio εest.

  According to this, it is possible to detect an abnormality of the mechanical compression ratio changing mechanism 15 (actuator 15M) using the in-cylinder pressure P detected by the in-cylinder pressure sensor 45.

Next, a modified example of the control device will be described.
(First modification)
The first modification is based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45, and the actuators other than the actuator 15M of the mechanical compression ratio changing mechanism 15 (for example, the variable intake timing device 14f and the throttle valve actuator 24a) are abnormal. Means for detecting. Hereinafter, description will be given with reference to the routine shown in FIG.

  The CPU of the first modified example repeatedly executes the “other actuator abnormality determination routine” shown in FIG. 13 every elapse of a predetermined time in addition to the routine executed by the CPU of the above embodiment. Therefore, at a predetermined timing, the CPU starts the process from step 1300 and proceeds to step 1305 to determine whether or not the value of the temporary abnormality flag Xkari is “0”. If the value of the temporary abnormality flag Xkari is “0”, the CPU proceeds to step 1310, and if not “0”, the CPU proceeds directly to step 1395 to end the present routine tentatively.

  In step 1310, the CPU determines whether or not the value of the determination execution flag XCK is “0”. If the value of the determination execution flag XCK is “0”, the CPU proceeds to step 1315, and if not “0”, the CPU proceeds directly to step 1395 to end the present routine tentatively.

  In step 1315, the CPU determines whether or not the value of the actuator abnormality flag XACTFail is “0”. If the value of the actuator abnormality flag XACTFail is “0”, the CPU proceeds to step 1320, and if not “0”, the CPU proceeds directly to step 1395 to end the present routine tentatively.

  In step 1320, the CPU determines whether or not the value of the cylinder pressure sensor abnormality flag XCPSFFail is “0”. The CPU proceeds to step 1325 if the value of the in-cylinder pressure sensor abnormality flag XCPSFFail is “0”, otherwise proceeds directly to step 1395 to end the present routine tentatively.

  In step 1325, the CPU determines whether the driving state of the vehicle is “neutral state (whether the signal from the neutral switch 49 is an on signal)”. If the driving state of the vehicle is in the neutral state, the CPU proceeds to step 1330, and if not in the neutral state, the CPU proceeds directly to step 1395 to end the present routine tentatively.

  As described above, the CPU indicates that the temporary abnormality flag Xkari, the determination execution flag XCK, the actuator abnormality flag XACTFail, and the in-cylinder pressure sensor abnormality flag XCPSFail are all “0”, and the driving state of the vehicle is neutral. When it is in the state, the process proceeds to step 1330 and subsequent steps to perform “an abnormality determination of other actuators”. That is, in the CPU, both the in-cylinder pressure sensor 45 and the mechanical compression ratio changing actuator 15M are normal, and the driving state of the vehicle is “the driving state in which the change in the driving state of the engine 10 does not affect the running of the vehicle”. In this case, the abnormality determination control of the actuator N described below is performed.

  Now assume that the CPU proceeds to step 1330. In this case, the CPU selects “actuator N to be subjected to abnormality determination” in step 1330. This “N” is assigned a unique value for each actuator.

  In this example, the actuators that should perform abnormality determination are the variable intake timing device 14f and the throttle valve actuator 24a. Therefore, every time this routine is executed, the CPU alternately selects one of the variable intake timing device 14f and the throttle valve actuator 24a as “actuator N to be subjected to abnormality determination”.

  Now, it is assumed that “variable intake timing device 14f” is selected as “actuator N to perform abnormality determination”. In this case, the CPU finely operates “the variable intake timing device 14 f that is the selected actuator N” in step 1335. That is, the CPU sends an “instruction signal for advancing (or retarding) the intake valve advance angle VVT by a minute angle ΔVVT from the current intake valve advance angle VVT0” to the variable intake timing device 14f.

  Next, the CPU proceeds to step 1340 and monitors whether or not a predetermined time has elapsed since the processing of step 1335 (at the time of starting fine operation of the selected actuator N). This predetermined time is the time (or the time required until the selected actuator N actually completes the “operation according to the instruction signal” after the instruction signal for performing the fine operation of the selected actuator N is transmitted. (A time obtained by adding a small amount of time to that time).

  When a predetermined time has elapsed from the processing of step 1335, the CPU makes a “Yes” determination at step 1340 to proceed to step 1345, where the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 is “scheduled change (in-cylinder pressure P It is determined whether or not it agrees with the “scheduled change”. The “scheduled change” is a “change in the in-cylinder pressure P” that occurs as “a result of finely operating the selected actuator N” in step 1335.

  More specifically, at present, an “instruction signal for matching the intake valve advance angle VVT to the intake valve advance angle VVT0 + ΔVVT” is sent to the “variable intake timing device 14f as the selected actuator N”. ing. Therefore, if the variable intake timing device 14f is operating normally, the intake valve 14d is opened at the intake valve opening timing determined by "the intake valve advance angle VVT0 + ΔVVT". Therefore, the in-cylinder pressure P should substantially coincide with the intake pipe pressure at that timing. Further, if the variable intake timing device 14f is operating normally, the intake valve 14d is closed at the intake valve closing timing determined by "the intake valve advance angle VVT0 + ΔVVT", and the air in the cylinder starts to be compressed. . Therefore, the in-cylinder pressure P should start to increase rapidly from that timing. These “coincidence of the in-cylinder pressure P at the intake valve opening timing with the intake pipe pressure” and “abrupt increase in the in-cylinder pressure P after the intake valve closing timing” are the “in-cylinder pressure P scheduled in this case” Change ".

  Therefore, in step 1345, the CPU determines that the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 substantially matches the intake pipe pressure at the intake valve opening timing determined by the intake valve advance angle VVT0 + ΔVVT. It is determined whether or not the in-cylinder pressure P has started to increase rapidly immediately after the intake valve closing timing determined by the angular angle VVT0 + ΔVVT.

  When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 indicates such a “scheduled change in the in-cylinder pressure P”, the CPU makes a “Yes” determination at step 1345 and proceeds to step 1350. Then, the value of the flag XACTfail (N) indicating the presence / absence of abnormality of the “selected actuator N” is set to “0”. Thus, the flag XACTfail (N) indicates “actuator N is normal” when the value is “0”. Thereafter, the CPU proceeds to step 1395 to end the present routine tentatively.

  On the other hand, when the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 does not indicate “scheduled change in the in-cylinder pressure P”, the CPU makes a “No” determination at step 1345 to proceed to step 1355 to flag XACTfail. The value of (N) is set to “1”. Thus, the flag XACTfail (N) indicates that “the actuator N is abnormal” when the value is “1”. Thereafter, the CPU proceeds to step 1395 to end the present routine tentatively.

  Next, when the CPU restarts the process of this routine and proceeds to step 1330, the CPU selects “throttle valve actuator 24a” as “actuator N to be subjected to abnormality determination”.

  In step 1335, the CPU finely operates “the throttle valve actuator 24a which is the selected actuator N”. That is, the CPU sends to the throttle valve actuator 24a “an instruction signal for increasing the throttle valve opening TA by a minute opening ΔTA from the current throttle valve opening TA0”.

  Thereafter, when a predetermined time has elapsed from the processing of step 1335, the CPU makes a “Yes” determination at step 1340 to proceed to step 1345, where the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 is “scheduled change”. It is determined whether or not they match. The “scheduled change” in this case is that the amount of intake air increases as the opening of the throttle valve 24 is increased by a minute opening ΔTA, and as a result, from the start of the compression stroke (intake valve closing timing). That is, the in-cylinder pressure P at a predetermined (arbitrary) crank angle until the ignition timing is higher than “the in-cylinder pressure P at the predetermined crank angle” immediately before the processing of step 1335 is executed.

  When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 indicates “scheduled change in the in-cylinder pressure P”, the CPU makes a “Yes” determination at step 1345 to proceed to step 1350, The value of the flag XACTfail (N) indicating the presence / absence of abnormality of the throttle valve actuator 24a "that is the actuator N is set to" 0 ". When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 does not indicate “scheduled change in the in-cylinder pressure P”, the CPU determines that the throttle valve actuator 24a is abnormal (“No” in step 1345). ”And proceeds to step 1355 to set the value of the flag XACTfail (N) to“ 1 ”. Thereafter, the CPU proceeds to step 1395 to end the present routine tentatively.

  As described above, according to the control device according to the first modification, based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45, an actuator other than the “actuator 15M of the mechanical compression ratio changing mechanism 15”, that is, The abnormality of the variable intake timing device 14f and the throttle valve actuator 24a can be easily detected.

(Second modification)
The internal combustion engine to which the second modification is applied has the same configuration as the engine 10 and further includes a variable exhaust timing device, a valved HC adsorption device, and a valved exhaust heat recovery device. The second modification includes means for detecting an abnormality of these “variable exhaust timing device, valved HC adsorption device and valved exhaust heat recovery device” based on “cylinder pressure P detected by the cylinder pressure sensor 45”. .

  The variable exhaust timing device has the same structure as the variable intake timing device 14f. That is, the variable exhaust timing device includes a hydraulic oil supply control valve (not shown) and a hydraulic pump (not shown), and the hydraulic oil is supplied and discharged by these to advance the phase of the exhaust cam relative to the exhaust cam shaft 14h by a desired amount. The angle can be retarded. In this example, the period during which the exhaust valve 14g is open (the valve opening crank angle width) is constant. Accordingly, when the exhaust valve opening timing is advanced or retarded by a predetermined angle by the variable exhaust timing device, the closing timing of the exhaust valve 14g is also advanced or retarded by the same predetermined angle.

  The valve-equipped HC adsorption device includes, for example, an adsorbent capable of adsorbing hydrocarbons (HC adsorbent) and an electric on-off valve as described in Japanese Patent Application Laid-Open No. 2007-327383. The HC adsorbent is disposed in the exhaust passage.

  When the electric on-off valve is closed in response to the instruction signal, substantially all of the exhaust gas flowing through the exhaust passage flows into the adsorbent. When the electric on-off valve is opened in response to the instruction signal, substantially all of the exhaust gas flowing through the exhaust passage is prevented from flowing into the adsorbent.

  Therefore, when the electric on-off valve is closed, the gas pressure (back pressure) in the exhaust passage of the internal combustion engine increases. As a result, “in-cylinder pressure at the opening timing of the exhaust valve when the electric on-off valve is closed” is larger than “in-cylinder pressure at the opening timing of the exhaust valve when the electric on-off valve is open”. growing. In addition, the HC adsorption device with a valve is not particularly limited as long as the back pressure is changed by opening and closing of the valve. For example, a structure as described in JP 2000-54829 A, JP 10-331625 A, or the like. May be provided.

  The exhaust heat recovery device with a valve is connected in parallel to a first exhaust passage that allows exhaust gas of an engine to pass therethrough as described in, for example, JP-A-2006-299858 and JP-A-2006-291906. An exhaust heat recovery device disposed in the second exhaust passage, and an electric switching valve. The branch positions of the first exhaust passage and the second exhaust passage are downstream of the valved HC adsorption device. The heat recovered by the valved exhaust heat recovery device is used, for example, to heat the engine coolant temperature when the engine is cold.

  In response to the instruction signal, the electric switching valve switches the exhaust passage so that “the exhaust gas flows through one of the first exhaust passage and the second exhaust passage”. Therefore, the back pressure when exhaust gas is allowed to pass through the second exhaust passage is larger than the back pressure when exhaust gas is allowed to pass through the first exhaust passage.

  As a result, “in-cylinder pressure P at the exhaust valve opening timing when exhaust gas is allowed to pass through the second exhaust passage and the exhaust heat recovery device” is “when exhaust gas is allowed to pass through the first exhaust passage” Is greater than the in-cylinder pressure P at the exhaust valve opening timing.

  Similar to the CPU of the first modification, the CPU of the second modification repeats the “other actuator abnormality determination routine” shown in FIG. 13 every elapse of a predetermined time in addition to the routine executed by the CPU of the above embodiment. Running. Each time the CPU of the second modified example executes the routine shown in FIG. 13, one of the variable exhaust timing device, the valved HC adsorption device, and the valved exhaust heat recovery device is set to “actuator to perform abnormality determination”. N ”is selected according to a predetermined order.

  Now, it is assumed that “variable exhaust timing device” is selected as “actuator N to perform abnormality determination”. In this case, the CPU finely operates “the variable exhaust timing device which is the selected actuator N” in step 1335. That is, the CPU sends an “instruction signal for advancing (or retarding) the exhaust valve advance angle by a minute angle ΔVET from the current exhaust valve advance angle” to the variable exhaust timing device. The exhaust valve advance angle is based on the case where the exhaust valve opening timing is the most retarded by the variable exhaust timing device, and the crank angle from the reference to the exhaust valve opening timing that is actually controlled I mean.

  Thereafter, when a predetermined time has elapsed from the processing of step 1335, the CPU makes a “Yes” determination at step 1340 to proceed to step 1345, where the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 is “scheduled change”. It is determined whether or not they match. The “scheduled change” in this case is that the in-cylinder pressure P rapidly decreases immediately after the exhaust valve opening timing determined based on the instruction signal sent in step 1335.

  When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 indicates “scheduled change in the in-cylinder pressure P”, the CPU makes a “Yes” determination at step 1345 to proceed to step 1350, The value of the flag XACTfail (N) indicating the presence / absence of abnormality of the “variable exhaust timing device that is the actuator N” is set to “0”. When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 does not indicate “scheduled change in the in-cylinder pressure P”, the CPU determines that the variable exhaust timing device is abnormal (“No” in step 1345). ”And proceeds to step 1355 to set the value of the flag XACTfail (N) to“ 1 ”. Thereafter, the CPU proceeds to step 1395 to end the present routine tentatively.

  Next, when the CPU restarts the processing of this routine and proceeds to step 1330, the CPU determines that “the actuator N to perform abnormality determination” is “the valve-equipped HC adsorption device (electrical on-off valve of the valve-equipped HC adsorption device)”. ”Is selected.

  In step 1335, the CPU finely operates the “electrical on-off valve of the valved HC adsorption device, which is the selected actuator N”. That is, the CPU determines that the electric on / off valve of the valved HC adsorption device “opens if the electric on / off valve is currently closed, and closes if the electric on / off valve is currently open. An instruction signal to be valved is sent out.

  Thereafter, when a predetermined time has elapsed from the processing of step 1335, the CPU makes a “Yes” determination at step 1340 to proceed to step 1345, where the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 is “scheduled change”. It is determined whether or not they match. As described above, “the in-cylinder pressure at the exhaust valve opening timing when the electric on-off valve is closed” is “the in-cylinder pressure at the exhaust valve opening timing when the electric on-off valve is open”. Bigger than. Therefore, the “scheduled change” in this case is that the in-cylinder pressure P at the exhaust valve opening timing is the processing of step 1335 when the instruction signal for closing the electric on-off valve is sent in step 1335. This is to be greater than the “in-cylinder pressure P at the exhaust valve opening timing” immediately before execution. Further, in this case, the “scheduled change” indicates that the cylinder pressure P at the exhaust valve opening timing causes the processing in step 1335 to be performed when an instruction signal for opening the electric on-off valve is sent in step 1335. This is to be smaller than “in-cylinder pressure P at the exhaust valve opening timing” immediately before execution.

  When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 indicates “scheduled change in the in-cylinder pressure P”, the CPU proceeds to step 1350 and “the selected actuator N of the valved HC adsorbing device is selected. The value of the flag XACTfail (N) indicating the presence / absence of abnormality of the “electric on-off valve” is set to “0”. Further, when the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 does not indicate “scheduled change in the in-cylinder pressure P”, the CPU determines that “the electric on-off valve of the valved HC adsorption device” is abnormal. Then, the process proceeds to step 1355 to set the value of the flag XACTfail (N) to “1”. Thereafter, the CPU proceeds to step 1395 to end the present routine tentatively.

  Next, when the CPU restarts the processing of this routine and proceeds to step 1330, the CPU sets “exhaust heat recovery device with valve (electrical switching of the exhaust heat recovery device with valve) as“ actuator N to perform abnormality determination ”. Valve) ”is selected.

  Then, in step 1335, the CPU finely operates “the electric switching valve of the exhaust heat recovery apparatus with valve that is the selected actuator N”. That is, the CPU switches to the electric switching valve of the exhaust heat recovery apparatus with a valve “if the exhaust gas is flowing through the first exhaust passage at the present time, the exhaust gas is switched through the second exhaust passage. Sends an “instruction signal”. Further, the CPU switches to the electric switching valve of the exhaust heat recovery device with a valve “if the exhaust gas is flowing through the second exhaust passage at the present time, the exhaust gas is passed through the first exhaust passage. Sends an “instruction signal”.

  Thereafter, when a predetermined time has elapsed from the processing of step 1335, the CPU makes a “Yes” determination at step 1340 to proceed to step 1345, where the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 is “scheduled change”. It is determined whether or not they match.

  As described above, “in-cylinder pressure at the exhaust valve opening timing when exhaust gas flows through the second exhaust passage” is “exhaust valve opening timing when exhaust gas flows through the first exhaust passage”. In-cylinder pressure ". Therefore, the “scheduled change” in this case is “instructed by sending an instruction signal for switching the exhaust gas flow path from the first exhaust passage to the second exhaust passage to the electric switching valve in step 1335. In the case where “the cylinder pressure P is at the exhaust valve opening timing”, the in-cylinder pressure P at the exhaust valve opening timing is larger than the “in-cylinder pressure P at the exhaust valve opening timing” immediately before the processing of step 1335 is executed.

  Further, in this case, the “scheduled change” is made by sending an instruction signal for switching the exhaust gas flow path from the second exhaust passage to the first exhaust passage to the electric switching valve in step 1335. In the case where “the cylinder pressure P at the exhaust valve opening timing” is smaller than “the cylinder pressure P at the exhaust valve opening timing” immediately before the processing of step 1335 is executed.

  When the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 indicates “scheduled change in the in-cylinder pressure P”, the CPU proceeds to step 1350 and “the exhaust heat recovery device with valve that is the selected actuator N”. The value of the flag XACTfail (N) indicating the presence / absence of abnormality of the “electric switching valve” is set to “0”. Further, when the in-cylinder pressure P detected by the in-cylinder pressure sensor 45 does not indicate “scheduled change in the in-cylinder pressure P”, the CPU indicates that the “electric switching valve of the exhaust heat recovery device with valve” is abnormal. The process proceeds to step 1355, where the value of the flag XACTfail (N) is set to “1”. Thereafter, the CPU proceeds to step 1395 to end the present routine tentatively.

  As described above, according to the control device according to the second modification, based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 45, an actuator other than the actuator 15M of the mechanical compression ratio changing mechanism 15, that is, Abnormalities in the “variable exhaust timing device, HC adsorption device with valve, and exhaust heat recovery device with valve” can be easily detected.

  As described above, the control device according to the embodiment and each modification according to the present invention can control the engine 10 based on the mechanical compression ratio close to the true mechanical compression ratio. Furthermore, these control devices can determine whether or not the actuator 15M of the mechanical compression ratio changing mechanism 15 has failed and whether or not the in-cylinder pressure sensor 45 has become abnormal. In addition, based on the in-cylinder pressure output from the in-cylinder pressure sensor 45, it is possible to easily determine whether there is an abnormality other than the actuator 15M.

  In addition, this invention is not limited to the said embodiment and modification, Furthermore, another modification can be employ | adopted within the scope of the present invention. For example, each of the above control devices confirms that the current operation state is “a state in which the operation state of the engine 10 that is a factor for determining the target mechanical compression ratio εtgt has not changed”, and then the state shown in FIG. “Change target mechanical compression ratio εtgt” by step 640 and / or “fine operation of selected actuator N” by step 1335 of FIG. 13 may be executed. In this case, “a state in which the operating state of the engine 10 that is a factor for determining the target mechanical compression ratio εtgt has not changed” means that the change amount per unit time of the accelerator pedal operation amount Accp is greater than the first predetermined threshold value. Confirmed by determining whether the small state continues for the first predetermined time or more and the state where the change amount per unit time of the engine speed NE is smaller than the second predetermined threshold continues for the second predetermined time or more. can do.

  In the embodiment and each modification, one or any two or more of the plurality of devices described as the actuator N to be subjected to abnormality determination is selected as the actuator N to actually perform abnormality determination. May be. Further, the actuator N to be subjected to the abnormality determination may be any one as long as the in-cylinder pressure is changed by operating the actuator. Furthermore, the minute amount Δε in step 640 of FIG. 6 may be a negative value. In this case, the conditions in step 1120 and step 1160 in FIG. 11 are changed as appropriate.

  Further, when the magnitude of the difference between the actual mechanical compression ratio εact and the expected mechanical compression ratio εest is larger than the predetermined threshold Ath, the control mechanical compression ratio εcont employed in step 925 and step 935 of FIG. May be “a predetermined mechanical compression ratio between the actual mechanical compression ratio εact and the expected mechanical compression ratio εest”. That is, the “predetermined mechanical compression ratio between the actual mechanical compression ratio εact and the predicted mechanical compression ratio εest” is, for example, an average value of the actual mechanical compression ratio εact and the predicted mechanical compression ratio εest ((εact + εest ) / 2), or a load average value of the actual mechanical compression ratio εact and the expected mechanical compression ratio εest (β · εact + (1−β) · εest, 0 <β <1), As in the first control device, a value obtained by adding a first predetermined value (positive value) to the predicted mechanical compression ratio εest or a value obtained by subtracting a second predetermined value (positive value) from the predicted mechanical compression ratio εest. There may be.

1 is a schematic cross-sectional view of a variable compression ratio internal combustion engine to which a control device according to an embodiment of the present invention is applied. FIG. 2 is an exploded perspective view of the engine compression ratio changing mechanism of the internal combustion engine shown in FIG. 1. FIG. 2 is a perspective view of a cylinder block of the internal combustion engine shown in FIG. 1. It is a figure for demonstrating the action | operation of the mechanical compression ratio change mechanism shown in FIG. FIG. 2 is a schematic plan view of the internal combustion engine shown in FIG. 1. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 5 performs. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 5 performs. It is a figure for demonstrating the method of acquiring a real machine compression ratio. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 5 performs. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 5 performs. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 5 performs. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 5 performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the modification of embodiment of this invention performs.

Explanation of symbols

10 ... Variable compression ratio internal combustion engine, 13 ... Cylinder block,
14 ... Cylinder head part, 14b ... Intake port, 14c ... Exhaust port, 14d ... Intake valve,
14f ... Variable intake timing device, 14g ... Exhaust valve,
15 ... Mechanical compression ratio changing mechanism, 15M ... Mechanical compression ratio changing actuator (electric motor),
15a ... case side bearing forming part, 15b ... block side bearing forming part,
15c ... shaft-like drive part, 15c1 ... shaft part, 15c2 ... fixed cylindrical part,
15c3 ... rotating cylinder, 15c4 ... gear,
16 ... Fuel injection valve, 20 ... Intake system, 30 ... Exhaust system,
43 ... Engine rotational speed sensor, 44 ... Stroke sensor, 45 ... In-cylinder pressure sensor,
48 ... accelerator opening sensor, 49 ... neutral switch, 50 ... electric control device.

Claims (3)

A mechanical compression ratio changing mechanism for changing a mechanical compression ratio, which is a ratio of the volume of the combustion chamber when the piston is at the bottom dead center position to the volume of the combustion chamber when the piston is at the top dead center position, according to the instruction signal A control device for a variable compression ratio internal combustion engine comprising:
Instruction means for determining a target mechanical compression ratio according to the operating state of the engine and sending an instruction signal to the mechanical compression ratio changing mechanism so that the mechanical compression ratio of the engine matches the determined target mechanical compression ratio When,
An in-cylinder pressure sensor that detects an in-cylinder pressure that is a pressure in the combustion chamber;
Actual mechanical compression ratio acquisition means for acquiring the mechanical compression ratio of the engine as an actual mechanical compression ratio based on the in-cylinder pressure detected by the in-cylinder pressure sensor;
Based on either the instruction signal sent to the mechanical compression ratio changing mechanism or the amount related to the operation amount of the mechanical compression ratio changing mechanism based on the instruction signal, the mechanical compression ratio of the engine is set as the expected mechanical compression ratio. An expected mechanical compression ratio acquisition means to acquire;
When the magnitude of the difference between the actual machine compression ratio and the expected machine compression ratio is smaller than a predetermined threshold, the actual machine compression ratio is acquired as a control machine compression ratio, and the actual machine compression ratio and the expected machine compression ratio are obtained. A control mechanical compression ratio acquisition means for acquiring a predetermined mechanical compression ratio between the actual mechanical compression ratio and the predicted mechanical compression ratio as a control mechanical compression ratio when a difference between the actual mechanical compression ratio and the predicted mechanical compression ratio is greater than the predetermined threshold value; ,
Control means for controlling the engine based on the control mechanical compression ratio;
A control device comprising: The control apparatus for a variable compression ratio internal combustion engine according to claim 1,
The control mechanical compression ratio acquisition means is
If the magnitude of the difference between the actual machine compression ratio and the expected machine compression ratio is greater than the predetermined threshold, and the actual machine compression ratio is greater than the expected machine compression ratio, the expected machine compression ratio is A value obtained by adding a predetermined value is obtained as the control mechanical compression ratio;
When the magnitude of the difference between the actual machine compression ratio and the expected machine compression ratio is larger than the predetermined threshold value, and the actual machine compression ratio is smaller than the expected machine compression ratio, (2) A control device configured to acquire a value obtained by subtracting a predetermined value as the mechanical compression ratio for control. A control device for a variable compression ratio internal combustion engine according to claim 1 or 2,
The instruction means sets a target compression ratio for abnormality determination that temporarily changes the target compression ratio by a minute amount when the magnitude of the difference between the actual mechanical compression ratio and the expected mechanical compression ratio is larger than the predetermined threshold. Including means,
Furthermore,
When the target compression ratio is temporarily changed by the abnormality determination target compression ratio setting means, the presence / absence of abnormality of the mechanical compression ratio changing mechanism is determined based on the actual mechanical compression ratio and the expected mechanical compression ratio. The control apparatus provided with the compression ratio change mechanism abnormality determination means to perform.

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