JP5104421B2 - Control device and control method for internal combustion engine - Google Patents

Description

  The present invention relates to a control device and a control method for an internal combustion engine having a compression ratio variable mechanism that makes a compression ratio variable, and more particularly to a technique for controlling ignition timing in accordance with the compression ratio.

As an internal combustion engine provided with a variable compression ratio mechanism for changing the compression ratio of the engine, for example, there is one disclosed in Patent Document 1. In the internal combustion engine described in Patent Document 1, while knocking is avoided by cooperative control of the mechanical compression ratio and the intake valve closing timing, when knocking is detected, the ignition timing is retarded.
JP 2002-258876 A

By the way, the compression ratio is controlled according to the operating state of the engine, and even in the same operating state, the demand for the ignition timing differs depending on the compression ratio.
Here, when the operating state changes, the target compression ratio and the target ignition timing are respectively set. However, the mechanically configured compression ratio variable mechanism is more responsive than the electric ignition timing control. Since it is low, ignition is performed transiently at a time that does not match the actual compression ratio, and knocking may occur particularly when the compression ratio is reduced during acceleration.

  In this case, in the internal combustion engine described in Patent Document 1, when the knocking is detected, the ignition timing is urgently retarded. Therefore, the ignition timing is excessively retarded, resulting in reduced acceleration performance and operational stability. There is a problem of causing deterioration.

The present invention addresses such problems, and in an internal combustion engine equipped with a variable compression ratio mechanism and a valve mechanism that varies the operating characteristics of the intake valve, knocking during transient operation during compression ratio change is achieved. It aims at suppressing generation | occurrence | production and effectively preventing the fall of acceleration performance and the deterioration of drivability.

The present invention provides a compression ratio variable mechanism that varies the compression ratio of an internal combustion engine and a valve mechanism that varies the operating characteristics of an intake valve, and the compression ratio of the compression ratio variable mechanism in the first half of the compression stroke for each cycle. After the intake valve is closed, the effective compression ratio at the compression top dead center in the same cycle is estimated based on the closing timing of the intake valve and the detected change speed of the compression ratio. The ignition timing in the same cycle is set based on the compression ratio.

  According to the present invention, it is possible to set an ignition timing (on the advance side) capable of obtaining a larger torque while avoiding knocking even during a transient operation while changing the compression ratio. Thereby, in an internal combustion engine equipped with a variable compression ratio mechanism, it is possible to suppress a decrease in acceleration performance and a deterioration in drivability.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of an internal combustion engine (engine) 1 according to an embodiment of the present invention.
In FIG. 1, an electronically controlled throttle valve 102, a fuel injection valve 103, and an intake valve 104 are disposed in the intake passage 101 of the engine 1 from the intake upstream side.

  The throttle valve 102 can control the intake air amount in accordance with the opening (throttle opening). However, in this embodiment, the intake air amount is controlled mainly by making the operation characteristic of the intake valve 104 variable, and the throttle valve 102 is used as an auxiliary.

  The fuel injection valve 103 is driven to open by an input injection signal, and injects a predetermined amount of fuel toward the vicinity of the umbrella portion of the intake valve 104. When the intake valve 104 is driven to open, a mixture of intake air and fuel is introduced into the combustion chamber 106 defined by the piston 105.

The intake valve 104 is driven to open and close by a valve mechanism 107 provided thereabove.
As shown in FIG. 2, the valve operating mechanism 107 includes a VEL mechanism 107a that can continuously change the operating angle and lift amount of the intake valve 104, and a VTC mechanism that can continuously change the center phase of the operating angle of the intake valve 104. 107b. However, such a configuration is merely an example and is not limited thereto.

  2 and 3, the VEL mechanism 107a extends in the cylinder row direction and rotates in conjunction with the rotation of the crankshaft. The VEL mechanism 107a is attached to the outer periphery of the drive shaft 151 so as to be rotatable relative to the valve lifter. A swing cam 152 that opens and closes the intake valve 104 via 141, an eccentric cam 153 fixed to the outer periphery of the drive shaft 151, and a ring-shaped link 154 externally fitted to the eccentric cam 153 so as to be relatively rotatable, A control shaft 155 provided substantially parallel to the drive shaft 151, a control cam 156 that is eccentrically fixed to the outer periphery of the control shaft 155, and is fitted on the control cam 156 so as to be relatively rotatable, and one end thereof is a ring-shaped link It includes a rocker arm 157 linked (coupled) to 154, and a rod-shaped link 158 that links (couples) the other end of the rocker arm 157 and the swing cam 152. Then, when the control shaft 155 is rotated by the actuator 161 via the gear train 162, the operating angle of the swing cam 152 is changed, and the operating angle θ (and the lift amount) of the intake valve 104 is continuously changed.

  On the other hand, the VTC mechanism 107b advances the opening / closing timing of the intake valve 105 by changing the rotational phase of the drive shaft 151 relative to the crankshaft so that the swing cam 152 is displaced in the rotational direction and the cam center angle changes. The angle is retarded (that is, the central phase (center angle) φ of the operating angle of the intake valve 104 is changed), and a known valve timing control mechanism can be used.

  Returning to FIG. 1, the cylinder head H is provided with an ignition plug 108 facing the upper center of the combustion chamber 106, and the ignition plug 108 ignites the air-fuel mixture introduced into the combustion chamber 106. Done.

  The combustion exhaust is discharged from the combustion chamber 106 through the exhaust valve 109 to the exhaust passage 110, purified by an exhaust purification catalyst (not shown) or the like, and then released into the atmosphere. The exhaust valve 109 is driven to open and close while the operating angle (lift amount) and the center phase of the operating angle are constant by a drive cam 111 provided on the exhaust side camshaft.

  Further, the engine 1 includes a variable compression ratio mechanism 200 configured as shown in FIG. In FIG. 4, the crankshaft 201 of the engine 1 includes a journal portion 202, a crankpin portion 203, and a counterweight 201a, and the journal portion 202 is rotatably supported by a main bearing (not shown) of the cylinder block. Has been.

  The crankpin portion 203 is provided at a position shifted by a predetermined amount from the rotation center of the journal portion 202, and a lower link 204 is rotatably connected thereto. The upper link 205 has a lower end side rotatably connected to one end of the lower link 204 by a connecting pin 206, and an upper end side rotatably connected to the piston 105 by a piston pin 207.

  An upper end side of the control link 208 is rotatably connected to the other end of the lower link 204 by a connecting pin 209, and a lower end side of the control link 208 is rotatably connected to the control shaft 210. Specifically, the control shaft 210 has a mounting portion provided intermittently in the axial direction, and the lower end side of the control link 208 is rotatably connected to the mounting portion by a connecting pin 211. The connecting pin 211 is provided at a position shifted from the rotation center P of the control shaft 210.

  Then, when the control shaft 210 is rotated by the actuator 214 via the gears 212 and 213, the connecting pin 211, that is, the swing fulcrum position on the lower end side of the control link 208 is changed. When the swing fulcrum position on the lower end side of the control link 208 changes, the stroke of the piston 105 changes, and the position of the piston 105 at the top dead center (TDC) becomes higher or lower. When the position of the piston 104 at the top dead center (TDC) is increased, the volume of the combustion chamber 106 is reduced and a high compression ratio state is established. Conversely, when the position of the piston 105 at the top dead center (TDC) is decreased, The volume of 106 is increased to a low compression ratio state.

That is, the compression ratio variable mechanism 200 changes the mechanical compression ratio of the engine 1 (hereinafter simply referred to as “compression ratio”) by changing the position of the piston 105 at the top dead center (TDC).
An engine controller (ECU) 300 incorporating a microcomputer includes an accelerator sensor 301 for detecting an accelerator opening APO, a crank angle sensor 302 for detecting a rotation angle of a crankshaft, and a throttle sensor for detecting an opening TVO of a throttle valve 102. 303, a temperature sensor 304 for detecting the engine coolant temperature Tw, a knocking sensor (knock detecting means) 305 for detecting the knocking intensity KI, a cylinder determining sensor 306 for determining the cylinder, and a rotation angle of the control shaft 155 of the VEL mechanism 107a ( That is, the first rotation angle sensor (operation characteristic detection means) 307 for detecting the operation angle θ of the intake valve 104 and the rotation angle of the drive shaft 151 of the VEL mechanism 107a (that is, the central angle φ of the operation angle of the intake valve 104). A rotation angle of the control shaft 210 of the variable compression ratio mechanism 200 (that is, the compression ratio of the engine 1). Detection signals are input from various sensors such as the third rotation angle sensor 309 to be detected. The engine speed Ne is calculated based on the detection result of the crank angle sensor 302. Then, ECU 300 executes engine control such as intake air amount control, fuel injection control, compression ratio control, ignition timing control, etc., based on the detection signals of the various sensors input.

Next, engine control executed by the ECU 300 will be described.
In the intake air amount control in the present embodiment, a torque to be generated by the engine 1 (hereinafter referred to as “target torque tTe”) is calculated based on the accelerator opening APO, and the valve mechanism 107 and the throttle are controlled based on the target torque tTe. The valve 102 is operated. Specifically, a target intake air amount (cylinder intake air amount corresponding to the target torque tTe) is calculated based on the target torque tTe and the engine rotational speed Ne, and a target operating characteristic (target target) of the intake valve 104 is calculated based on this target intake air amount. The operating angle θ and the target center angle φ are set to operate the valve mechanism 107, and the actual cylinder intake air amount (actual intake air amount) is calculated based on the operation characteristics of the intake valve 104 to obtain the target intake air. The throttle valve 102 is operated based on the deviation between the amount and the calculated actual intake air amount (adjusting the intake pressure).

  Further, the fuel injection control in the present embodiment calculates the amount of fuel necessary to achieve a predetermined equivalence ratio under the intake air amount controlled by the intake air amount control, and corresponds to this fuel amount. A drive signal is output to the fuel injection valve 103 at a predetermined timing.

  Further, in the compression ratio control in the present embodiment, a target compression ratio is set with reference to a target compression ratio setting map set in advance based on the engine rotational speed Ne and the engine load, and the compression ratio is determined based on the target compression ratio. The variable mechanism 200 is operated.

  Furthermore, the ignition timing control estimates the effective compression ratio at the compression top dead center (TDC) for each cycle, and controls the ignition timing based on the predicted effective compression ratio. Specifically, in the first half of the compression stroke from the intake valve closing time (IVC) to the ignition timing in each cycle, the compression top dead center is calculated from the speed of change of the compression ratio by the variable compression ratio mechanism 200 and the closing timing IVC of the intake valve 104. The effective compression ratio at (TDC) is predicted, the actual engine torque (actual intake air amount) and the engine rotational speed Ne are detected, the ignition timing is set based on these, and the ignition plug is set to the set ignition timing. Operate 108.

FIG. 5 is a flowchart of engine control according to the embodiment.
In step S1, the accelerator opening APO and the engine speed Ne are detected.
In step S2, the target torque tTe is calculated based on the accelerator opening APO.

  In step S3, the target compression ratio tε, the target operating angle tθ of the intake valve 104, and the target center angle φ are set with reference to maps (FIGS. 6 to 8) set in advance based on the target torque tTe and the engine rotational speed Ne. .

  Here, the target compression ratio tε is set to a high compression ratio in order to improve fuel efficiency at low rotation and low load, and is set to a low compression ratio to avoid occurrence of knocking at high load (FIG. 6). Further, the target operating angle θ and the target center angle φ of the intake valve 104 are set so as to secure a cylinder intake air amount necessary to achieve the target torque tTe. Basically, the target operating angle θ of the intake valve 104 is set to be small at low rotation and low load, and is set to be larger as it is on the high load and high rotation side (FIG. 7). The target center angle tφ of the intake valve 104 is set to the advanced angle side at low rotation and low load, and is set to the retard angle side as it is on the high rotation high load side (FIG. 8). Then, the variable compression ratio mechanism 200 is operated based on the target compression ratio ε set here, and the valve mechanism 107 is operated based on the target operating angle tθ and the target central angle φ.

In step S4, a cycle start signal is detected. This is because the cylinder for setting the ignition timing is specified. Here, the detection signal of the cylinder discrimination sensor 304 is used instead.
In step S5, the engine speed Ne and the throttle opening TVO are detected.

  In step S6, the closing timing IVC of the intake valve 104 is detected. Here, the operating angle θ and the central angle φ of the intake valve 104 are obtained from the detection results of the crank angle sensor 302, the first rotation angle sensor 307, and the second rotation angle sensor 308, and the obtained operation angle θ of the intake valve 104 is obtained. And the closing timing IVC of the intake valve 104 is detected from the central angle φ. Note that the time (actual IVC) when the intake valve 104 is actually closed may be detected.

  In step S7, an actual intake air amount (cycle air amount) is calculated (estimated). Here, the actual intake air amount is calculated from the throttle opening TVO detected in step S5 and the operating angle θ and the central angle φ of the intake valve 104 obtained in step S6. As described above, by calculating the actual intake air amount after detecting the throttle opening TVO and the operation characteristics (operation angle and center angle) of the intake valve 104, the operation characteristics of the intake valve 104 are changing. In addition, the actual intake air amount in the current cycle can be accurately calculated.

In step S8, the actual piston compression ratio rε is detected in the first half of the compression stroke after the intake valve 104 is closed, and the change rate of the compression ratio by the variable compression ratio mechanism 200 is calculated.
Here, the actual compression ratio rε means a compression ratio (piston position at the top dead center) realized in the operating state of the variable compression ratio mechanism 200 at that time, and the detection of the actual compression ratio rε is performed by the compression stroke. This is done by referring to a map (FIG. 9) set in advance based on the detection result of the third rotation angle sensor 309 (the rotation angle of the control shaft 210) in the first half. The change rate of the compression ratio is, for example, the detected actual compression ratio rε, the actual compression ratio rε ₀ before the operation of the variable compression ratio mechanism 200, and the elapsed time t from the start of the operation of the compression ratio variable mechanism 200. Calculate based on [(rε−rε ₀ ) / t].

  When the compression ratio is variable by changing the piston position at the top dead center (TDC) as in the variable compression ratio mechanism 200 in the present embodiment, the compression ratio is changed by the pressure (combustion pressure) applied to the piston 105. The speed (that is, the speed of change of the compression ratio) changes. That is, since the change rate of the compression ratio varies from cycle to cycle due to the influence of the combustion fluctuation and Pmax position in the previous cycle, the actual compression ratio rε is detected in the first half of the compression stroke for each cycle, and the compression by the compression ratio variable mechanism 200 The rate of change of the ratio is calculated.

  Here, when the third rotation angle sensor 309 can detect not only the rotation angle of the control shaft 210 of the variable compression ratio mechanism 200 but also the rotation speed (angular velocity) of the control shaft 210, the actual compression ratio rε is set. Of course, the rotation speed of the control shaft 210 (that is, the change speed of the compression ratio) may be directly detected together with the actual compression ratio rε.

In step S9, the effective compression ratio ε ′ _TDC at the compression top dead center (TDC) is estimated based on the closing timing (IVC) of the intake valve 104 detected in step S6 and the change rate of the compression ratio calculated in step S8. To do.

In step S10, as shown in FIG. 10, based on the engine speed Ne detected in step S5, the intake air amount (engine torque) calculated in step S7, and the effective compression ratio ε ′ _TDC estimated in step S9. Set ignition timing with reference to the map. Then, ignition is performed at the set ignition timing.

  As shown in FIG. 10, in common with each effective compression ratio ε ′, the advance limit of the ignition timing is determined by knocking, and the retard limit is determined by the torque fluctuation (surge torque limit) of the engine 1. In order to achieve stable driving performance, it is necessary to set the ignition timing between the two. In general, the higher the compression ratio (effective compression ratio ε ′), the higher the knocking strength. Therefore, the advance limit of the ignition timing is retarded as the compression ratio increases, and from the knock limit ignition timing to the surge limit ignition timing. The margin of becomes smaller. In addition, as the compression ratio (effective compression ratio ε ′) increases, the influence of the ignition timing setting on the engine efficiency (torque) increases, and a slight delay in the ignition timing greatly reduces engine performance.

Therefore, the effective compression ratio ε ′ _TDC at the compression top dead center (TDC) is estimated, and the ignition timing is set based on the estimated effective compression ratio ε ′ _TDC. Set the ignition timing (more advanced side) to obtain torque.

In step S11, knocking strength KI is detected.
In step S12, the detected knock intensity KI (corresponding to the "first threshold value" of the present invention) preset predetermined reference value in step S11 is determined whether it exceeds the KI _TH. If KI> KI _TH , it is determined that knocking greater than the allowable strength has occurred, and the process proceeds to step S13. If KI ≦ KI _TH , the process proceeds to step S14.

  In step S13, the ignition timing is retarded. Then, returning to step S3, control for lowering the compression ratio of the next cycle, control for limiting the intake air amount of the next cycle, and / or control for increasing the operating speed of the compression ratio variable mechanism 200 are performed. These controls are performed by updating (correcting) the target value in step S3. Specifically, the target compression ratio tε is decreased to lower the compression ratio, and the amount of power supplied to the actuator 214 of the variable compression ratio mechanism 200 is increased. The ratio change rate) is increased and / or the target operating angle tθ of the intake valve 104 is decreased or the target central angle φ is advanced to limit the intake air amount. This suppresses the occurrence of knocking in the next cycle.

In step S14, it is determined whether or not the knocking strength KI detected in step S11 has a margin with respect to the predetermined reference value (that is, knocking). Here, it is determined whether or not the detected knocking intensity KI is less than 90% of the predetermined reference value KI _TH , that is, 0.9 × KI _TH (corresponding to the “second threshold value” of the present invention). To do. If KI <0.9 × KI _TH , the process proceeds to step S15.

  In step S15, the ignition timing advance correction is performed, and the process returns to step S3. Here, when the ignition timing is already MBT, the advance timing correction of the ignition timing is not performed, the target compression ratio tε of the next cycle is increased to increase the compression ratio, and / or the compression ratio variable mechanism The operating speed of the compression ratio variable mechanism 200 is decreased by decreasing the amount of power supplied to the actuator 214 of 200 (reducing the compression ratio changing (decreasing) speed). Thereby, the thermal efficiency and fuel consumption performance of the engine 1 are improved.

  Further, in the case of full-open acceleration that requires particularly high torque response, the operation of the VEL mechanism 107a is performed by increasing the target operating angle tθ or increasing the amount of power supplied to the actuator 161 of the VEL mechanism 107a. Increase torque response performance by increasing speed. In this case, knocking is likely to occur, but in this embodiment, the ignition timing is set for each cycle, and the ignition timing can be set near the knocking limit while avoiding knocking. If knocking exceeding the allowable level occurs, the ignition timing is corrected in step S13, and the target value is reviewed in the next step S3.

On the other hand, the process proceeds in step S14, KI ≧ 0.9 × _{KI TH,} i.e., if the knock intensity KI slightly below a threshold value _{KI TH,} it is judged as being controlled in the vicinity of approximately allowable knock intensity to step S16.

  In step S16, it is determined whether or not the compression ratio ε, the operating angle θ of the intake valve 104, and the central angle φ of the operating angle have reached the target value. If the target value has been reached, this flow is terminated. If not, the process returns to step S3 to process the next cycle.

FIG. 11 is a time chart of the engine control.
When the acceleration is considered, since the target torque tTe is determined based on the accelerator opening APO and the engine load is increased, control for reducing the compression ratio is performed. The change of the compression ratio ε is started by the operation of the variable compression ratio mechanism 200 (time t0), but there is a delay until the actual compression ratio reaches the target compression ratio tε. Here, the intake air amount does not change after the intake valve 104 is closed, whereas the compression ratio continues to change during the subsequent compression stroke. There is a risk that knocking may occur due to a deviation from the compression ratio at the ignition timing.

Accordingly, the closing timing (IVC) of the intake valve 104 is detected (time t1), and at the predetermined timing in the first half of the compression stroke after the closing of the intake valve 104 (time t2), the actual compression ratio rε is detected and the compression ratio is determined. And the effective compression ratio ε ′ _TDC at the compression top dead center (TDC) is estimated based on the closing timing (IVC) of the intake valve 104 and the change speed of the compression ratio. In other words, the compression ratio (mechanical compression ratio) ε _TDC at the compression top dead center (TDC) by the variable compression ratio mechanism 200, that is, the piston position at the compression top dead center TDC is obtained, and the closing timing IVC of the intake valve 104 is obtained. The effective compression ratio ε ′ _TDC at the compression top dead center (TDC) is estimated based on the change (amount) of the piston position from the compression top dead center (TDC). Then, based on the estimated effective compression ratio ε ′ _TDC , an ignition timing that can obtain a maximum torque (more advanced side) while avoiding knocking is set.

  In the present embodiment, the ECU 300 and the third rotation angle sensor 309 (especially the process of step S8 in FIG. 5) correspond to the “change speed detecting means” of the present invention, and the ECU 300 (particularly the process of step S7 in FIG. 5). Corresponds to the “intake air amount calculation means” of the present invention, and ECU 300 (particularly the processing of step S9 in FIG. 5) corresponds to the “effective compression ratio estimation means” of the present invention, and ECU 300 (particularly the step of FIG. 5). Steps S10 and S12 to S15) correspond to “ignition timing setting means” and “control means” of the present invention.

  According to this embodiment, the compression ratio change rate is detected in the first half of the compression stroke for each cycle, and the compression top deadline in the cycle is determined based on the detected compression ratio change rate and the intake valve closing timing (IVC). The effective compression ratio at the point is estimated, and the ignition timing is set based on the estimated effective compression ratio at the top dead center of the compression point. Since the ignition timing can be set, the thermal efficiency can be improved particularly during transient operation.

  Also, if the detected knocking intensity exceeds the reference value, the ignition timing is retarded to avoid knocking, the target compression ratio of the next cycle is reduced, the intake air amount is limited, and Since the operating speed of the variable compression ratio mechanism is increased, the ignition timing can be set at a timing with high efficiency on the advance side while avoiding knocking more accurately in the next cycle.

  Further, when the detected knocking intensity has a margin with respect to the reference value, the ignition timing is corrected to advance, the compression ratio of the next cycle is increased, and / or the operating speed of the compression ratio variable mechanism is decreased. Therefore, it is possible to effectively improve the thermal efficiency and fuel consumption performance especially during transient operation.

  In the above embodiment, the closing timing (IVC) of the intake valve 104 is detected in step S6 of FIG. 5, but when the closing timing (IVC) of the intake valve 104 is fixed or controlled to be constant. Needless to say, this step can be omitted. In this case, in step S7 in FIG. 5, the cycle air amount may be calculated based on the intake air amount detected by an air flow meter (not shown) or the like.

  Although the basic embodiment of the present invention has been described above, the application example of the present invention is not limited to this, and can be applied in various modifications. Therefore, some modifications of the above embodiment will be described.

  First, in the above embodiment, the actual compression ratio rε is detected only once in the first half of the compression stroke, but the actual compression ratio rε may be detected a plurality of times in the first half of the compression stroke for each cycle. About other points, it is the same as that of the said embodiment.

Since the in-cylinder pressure rises during the compression stroke, there is a high possibility that the rate of change of the compression ratio also fluctuates (increases). Further, the in-cylinder pressure may be changed due to the influence of the change in the intake air amount and the combustion change in the previous cycle. Therefore, the effective compression ratio ε at the compression top dead center is detected by detecting the actual compression ratio rε a plurality of times during the compression stroke and detecting (calculating) the change rate of the compression ratio based on the detected plurality of actual compression ratios rε. ′ Increase the estimation accuracy of _TDC .

Specifically, as shown by a solid line in FIG. 12, an approximate curve (corresponding to a change rate of the compression ratio) is created by a plurality (preferably three or more) of the actual compression ratios rε detected during the compression stroke, Based on this approximate curve and the closing timing (IVC) of the intake valve 104, in other words, the actual compression ratio ε _TDC at the compression top dead center in the same cycle from the approximate curve (ie, the piston at the top dead center). (Position) is obtained (predicted), and the effective compression ratio ε ′ _TDC at the compression top dead center is estimated based on the actual compression ratio ε _TDC and the closing timing (IVC) of the intake valve 104. As a result, the actual compression ratio change is deviated from the compression ratio change curve (broken line) calculated in advance from the rotational position of the control shaft 210 of the variable compression ratio mechanism 200 and the response speed of the actuator 214. Even in such a case, the effective compression ratio ε ′ _TDC at the compression top dead center can be accurately estimated. As a result, the ignition timing can be advanced to the knock allowable limit with high accuracy for each cycle, and in particular, the acceleration performance can be improved.

Here, in the case of detecting a plurality of actual compression ratio Aruipushiron is preferably one of them with the actual compression ratio Aruipushiron _IVC of closing timing of the intake valve 104 (IVC). This is because the effective compression ratio ε ′ _TDC at the compression top dead center can be estimated based on the actual compression ratio rε _IVC (piston position) at the start of the compression stroke, and the estimation accuracy can be improved.

When it is difficult to detect all of the plurality of actual compression ratios rε during the compression stroke, the actual compression ratios detected in the compression stroke of the previous cycle may be included as shown in FIG. In this case, an approximate curve is obtained from at least one actual compression ratio (one in the figure) detected in the compression stroke of the current cycle and at least one actual compression ratio (two in the figure) detected in the compression stroke of the previous cycle. The effective compression ratio ε ′ _TDC at the compression top dead center of the current cycle is estimated based on this approximate curve and the closing timing (IVC) of the intake valve 104.

Next, in the case of an in-cylinder direct injection engine, additional fuel injection may be performed in addition to the ignition timing retardation correction in step 13 of FIG.
FIG. 14 shows an in-cylinder direct injection engine. 14, only the point that the fuel injection valve 103 is arranged so as to inject fuel directly into the cylinder is different from the above embodiment (FIG. 1), and the other configurations are the same. In this configuration, the engine control (FIG. 5) is performed, and if it is determined in step S12 that knocking exceeding the allowable strength has occurred, the ignition timing is retarded and additional fuel injection is performed in step S13. .

This is because knocking is suppressed by increasing the fuel concentration and lowering the specific heat ratio to lower the in-cylinder temperature and supplying turbulence in the cylinder to increase the flame propagation speed. As a result, the retard correction of the ignition timing becomes unnecessary or the retard amount of the ignition timing can be reduced, so that a torque decrease (ignition timing retard) accompanying the occurrence of knocking can be suppressed. Here, since knocking is more likely to occur as the compression ratio is higher, it is preferable to increase the amount of additional injection as the effective compression ratio ε ′ _TDC estimated in step S9 is higher. When knocking cannot be sufficiently suppressed only by additional fuel injection, the target value is updated (corrected) in step S3 as in the above embodiment.

Further, an in-cylinder pressure sensor for detecting the in-cylinder pressure is provided, and the in-cylinder pressure is detected in the first half of the compression stroke. You may make it utilize for estimation of (epsilon) ' _TDC (step S9 of FIG. 5).

Thereby, the calculation accuracy of the cycle air amount and the estimation accuracy of the effective compression ratio ε ′ _TDC at the compression top dead center are greatly improved. In addition, since the knocking detection accuracy is increased, the ignition timing retardation correction (step S13 in FIG. 5) can be minimized. Further, by detecting the maximum pressure value and its position for each cylinder during a predetermined steady operation, and correcting the ignition timing for each cylinder based on the detection result, the compression ratio changes over time due to, for example, deposit Even in such a case, it is possible to perform stable operation with little torque fluctuation while avoiding knocking.

It is a figure showing a schematic structure of an engine concerning an embodiment of the present invention. It is a figure which shows the structure of the valve operating mechanism (VEL mechanism + VTC mechanism) of an intake valve. It is a figure which shows the structure of a VEL mechanism. It is a figure which shows the structure of a compression ratio variable mechanism. It is a flowchart of the engine control which concerns on embodiment. It is a figure which shows an example of a target compression ratio setting map. It is a figure which shows an example of the target operating angle setting map of an intake valve. It is a figure which shows an example of the target center angle setting map of the operating angle of an intake valve. It is a figure which shows the relationship between the rotation angle of a control shaft, and an actual compression ratio. It is a figure which shows the relationship between ignition timing, an engine torque, and an effective compression ratio. It is a time chart of engine control concerning an embodiment. It is a figure for demonstrating the modification of embodiment. It is a figure for demonstrating the modification of embodiment similarly. It is a figure for demonstrating the modification of embodiment similarly.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 101 ... Intake passage, 102 ... Throttle valve, 103 ... Fuel injection valve, 104 ... Intake valve, 107 ... Valve mechanism, 107a ... VEL mechanism, 107b ... VTC mechanism, 108 ... Spark plug, 151 ... Drive shaft 155 ... control shaft, 200 ... compression ratio variable mechanism, 210 ... control shaft, 300 ... engine controller, 301 ... accelerator sensor, 302 ... crank angle sensor (engine speed detection means), 304 ... throttle sensor, 305 ... knocking sensor 307: First rotation angle sensor (operation characteristic detection means) 308: Second rotation angle sensor (operation characteristic detection means) 309: Third rotation angle sensor

Claims (12)

A variable compression ratio mechanism for varying the compression ratio of the internal combustion engine;
A valve mechanism that makes the operating characteristics of the intake valve variable;
A change speed detecting means for detecting a change speed of the compression ratio by the compression ratio variable mechanism in the first half of the compression stroke for each cycle;
Effective compression ratio estimation means for estimating the effective compression ratio at the compression top dead center in the same cycle based on the detected change speed of the compression ratio and the closing timing of the intake valve after the intake valve is closed;
Ignition timing setting means for setting the ignition timing in the same cycle based on the estimated effective compression ratio;
Control means for performing ignition at a set ignition timing;
A control device for an internal combustion engine, comprising: The change speed detecting means detects an actual compression ratio realized by the operating state of the compression ratio variable mechanism at that time in the first half of the compression stroke for each cycle, and changes the compression ratio based on the detected actual compression ratio. the control system of claim 1 Symbol placement of the internal combustion engine, and calculates the velocity. 3. The control apparatus for an internal combustion engine according to claim 2 , wherein the change speed detecting means detects the actual compression ratio a plurality of times. 4. The control apparatus for an internal combustion engine according to claim 3 , wherein the detection of the actual compression ratio performed a plurality of times includes detection of an actual compression ratio at the closing timing of the intake valve. A rotational speed detecting means for detecting the rotational speed of the engine;
An operating characteristic detecting means for detecting an operating characteristic of the intake valve;
An intake air amount calculating means for calculating an intake air amount based on the detected operating characteristic of the intake valve;
Further comprising
Said ignition timing setting means, the estimated effective compression ratio, based on the rotational speed and the intake air amount calculated of the detected engine of claim 1, wherein the setting the ignition timing The control apparatus for an internal combustion engine according to any one of the above. A knock detecting means for detecting knocking strength;
6. The control unit according to claim 1, wherein when the detected knocking intensity exceeds a preset first threshold value, the ignition timing is retarded. 6. The internal combustion engine control device described. A knock detecting means for detecting knocking strength;
When the detected knocking strength exceeds a preset first threshold, the control means controls to reduce the compression ratio of the next cycle, control to limit the intake air amount of the next cycle, and the compression ratio The control device for an internal combustion engine according to any one of claims 1 to 6 , wherein at least one of control for increasing an operation speed of the variable mechanism is performed. 8. The control unit according to claim 6 or 7 , wherein the control means corrects the ignition timing when the detected knocking intensity is below a second threshold value that is smaller than the first threshold value. Control device for internal combustion engine. When the detected knocking strength is less than a second threshold value that is smaller than the first threshold value, the control means increases the compression ratio of the next cycle and decreases the operation speed of the compression ratio variable mechanism. the control system of claim 6 or claim 7, wherein the internal combustion engine which comprises carrying out at least one of the control. Comprising fuel injection means for directly injecting fuel into the cylinder;
The said control means performs additional injection of fuel, when the detected knocking intensity | strength exceeds the preset 1st threshold value, The fuel injection of any one of Claims 6-9 characterized by the above-mentioned. Control device for internal combustion engine. 11. The control apparatus for an internal combustion engine according to claim 10, wherein the amount of fuel to be additionally injected is increased as the effective compression ratio at the compression top dead center is higher. In an internal combustion engine equipped with a variable compression ratio mechanism that makes the compression ratio variable and a valve mechanism that makes the operation characteristics of the intake valve variable,
Detecting the speed of change of the compression ratio by the compression ratio variable mechanism in the first half of the compression stroke for each cycle;
Estimating the effective compression ratio at the compression top dead center in the same cycle based on the detected change rate of the compression ratio and the closing timing of the intake valve after the intake valve is closed; and
Setting the ignition timing within the same cycle based on the estimated effective compression ratio;
Performing ignition at a set ignition timing;
An internal combustion engine control method comprising:

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