JP4269909B2 - Control device and control method for variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine capable of changing an engine compression ratio.

In a variable compression ratio internal combustion engine in which the engine compression ratio can be changed, the higher the compression ratio, the more the fuel consumption rate is improved. Therefore, Patent Document 1 discloses an attempt to improve the fuel consumption rate without causing knocking by using a high compression ratio during low load operation and a low compression ratio during high load operation.
JP 7-229431 A

  Referring to FIG. 25, during engine deceleration due to a decrease in the accelerator opening corresponding to the required load, the throttle opening is decreased and the intake air amount (intake air amount) is decreased as the accelerator opening decreases. Since the knock limit compression ratio increases as the intake air amount decreases, it is preferable to increase the engine compression ratio in order to improve fuel consumption. However, due to the dynamic delay of air caused by the collector volume etc. downstream of the throttle, a change in the actual intake amount with respect to a decrease in the throttle opening is inevitably accompanied by a response delay. Also, the change in the compression ratio depends on a mechanism for changing the compression ratio, its actuator, and the like, but involves a certain amount of response delay. Due to the difference between the responsiveness of the throttle opening (that is, the intake air amount) and the responsiveness of the compression ratio, the intake air amount and the compression ratio deviate from the intended values transiently and temporarily during engine deceleration. May adversely affect engine operability. For example, when the response of the throttle opening is slow with respect to the response of the compression ratio, during the deceleration, the intake amount becomes transiently and temporarily high and the compression ratio becomes high, causing knocking (also simply called knocking). There is a fear. Such a problem is particularly likely to appear in an engine equipped with a supercharger having a large intake response delay or an engine excellent in responsiveness of the compression ratio. The present invention has been made in view of such problems.

  A target compression ratio and a target throttle opening are set according to at least the accelerator opening. During engine deceleration in which the accelerator opening is reduced, at least one of the target compression ratio and the target throttle opening is temporarily corrected to the lower side. The engine compression ratio and the throttle opening degree are respectively controlled toward the corrected target compression ratio and target throttle opening degree.

  According to the present invention, at least one of the target compression ratio and the target throttle opening is temporarily corrected to the lower side during engine deceleration in anticipation of a response delay of the accelerator opening and the compression ratio. In addition, it is possible to prevent the occurrence of knocking due to a temporary increase in both the intake air amount and the compression ratio.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an example of a variable compression ratio internal combustion engine 1 according to the present invention. The crankshaft 31 includes a plurality of journal portions 32, a crankpin 33, and a counterweight portion 31a. The journal portion 32 is rotatably supported by a main bearing of a cylinder block (not shown) serving as an engine body. The crank pin 33 is eccentric from the journal portion 32 by a predetermined amount. A piston 38 that receives combustion pressure is fitted to the cylinder 39 of the cylinder block so as to be movable up and down. An intake valve 43 that opens and closes the intake port 44 in synchronism with the rotation of the crankshaft 31 and an exhaust valve 45 that opens and closes the exhaust port 46 in synchronism with the rotation of the crankshaft 31 are disposed on the cylinder 39. Has been.

  The internal combustion engine 1 includes a variable compression ratio mechanism using a multi-link type piston-crank mechanism. The variable compression ratio mechanism includes a lower link 34 that is rotatably fitted to the crank pin 33, an upper link 35 that links the lower link 34 and the piston 38, and a control link 40 that has one end connected to the lower link 34. The engine compression ratio is made variable by changing the motion constraint condition of the lower link 34 via the control link 40.

  The lower link 34 has a substantially T-shape, and the crank pin 33 is fitted in a substantially central connecting hole configured to be split from a main body 34a and a cap 34b. The upper link 35 is rotatably connected to the lower link 34 by a connecting pin 36 at the lower end side, and is rotatably connected to the piston 38 by a piston pin 37 at the upper end side. The control link 40 has an upper end side rotatably connected to the lower link 34 by a connecting pin 41 and a lower end side rotatably connected to an appropriate position of, for example, a cylinder block as an engine body via a control shaft 42. Specifically, the control shaft 42 is supported by the engine body so as to rotate about the small diameter portion 42b, and the lower end portion of the control link 40 is rotatable on the large diameter portion 42a that is eccentric to the small diameter portion 42b. Is fitted.

  The rotation position of the control shaft 42 is controlled by a compression ratio control actuator described later. The compression ratio control actuator can hold the control shaft 42 at an arbitrary rotational position against a reaction force applied from the control link 40. When the control shaft 42 is rotated by the compression ratio control actuator, the axial center position of the large-diameter portion 42a that is eccentric with respect to the small-diameter portion 42b, particularly the relative position with respect to the engine body changes. As a result, the swing support position at the lower end of the control link 40 changes, the motion restraint condition of the lower link 34 changes, the stroke characteristics of the piston 38 change, and the engine compression ratio changes.

  Such a variable compression ratio mechanism has the following effects in addition to being able to continuously change and control the engine compression ratio according to the engine operating state. Since it is a multi-link type piston-crank mechanism in which the piston 38 and the crank pin 33 are linked by a plurality of link parts (upper link and lower link), the single link type of the piston and the crank pin linked by a single connecting rod. Compared to the piston-crank mechanism, the stroke characteristic of the piston itself can be brought close to an appropriate characteristic such as a simple vibration characteristic. Since the control link 40 is disposed so as to extend substantially downward from the lower link 34, the control shaft 42 can be disposed in a crankcase obliquely below the crankshaft 31 having a relatively large space. Therefore, the control shaft 42 and its actuator and the control link 40 can be easily accommodated and arranged in the crankcase, and the engine mountability is excellent.

  Further, the internal combustion engine 1 includes a turbocharger 51 as a supercharger. The turbocharger 51 has a configuration in which a turbine 52 located in an exhaust passage 54 and a compressor 53 located in an intake passage 55 are coaxially arranged. In order to control the supercharging pressure in accordance with operating conditions, An exhaust bypass valve 56 for bypassing a part of the exhaust from the upstream side of the turbine 52 is provided.

  FIG. 1 is an explanatory diagram showing a system configuration of a control device for the internal combustion engine 1. An air flow meter 2 for detecting an intake air amount (intake air amount) is disposed upstream of the compressor 53 in the intake passage 55, an intercooler 3 is disposed downstream of the compressor 53, and an actual supercharging pressure is further provided downstream thereof. An intake pressure sensor 4 to be detected is arranged. Further, the crank angle sensor 5 for detecting the crank angle of the engine, the oxygen sensor 6 for responding to the exhaust composition, the water temperature sensor 7 for detecting the cooling water temperature, the knocking sensor 8 for detecting knocking, and the intake passage are opened and closed. A throttle opening sensor 10 that detects the opening of the throttle valve 9 that adjusts the intake air amount, an accelerator opening sensor 21 that detects an operation amount of the accelerator pedal, that is, an accelerator opening, and the like are provided. Detection signals from these sensors are input to an engine control module (ECM) 11.

  As main actuators, an electromagnetic supercharging pressure control valve 12 for controlling the negative pressure supply to the diaphragm portion 56A of the exhaust bypass valve 56, and a compression ratio control for controlling the compression ratio by moving the control shaft 42 described above. An actuator 13 and an AAC valve 15 that controls the amount of auxiliary air introduced through the intake bypass passage 14 are provided. The throttle valve 9 is an electric throttle that can control the opening degree independently of the accelerator opening degree, and is driven and controlled by an actuator (not shown). These actuators are controlled by the output signal of the engine control module 11. The compression ratio control actuator 13 is composed of, for example, a step motor. The AAC valve 15 is mainly used for feedback control of the idling speed and canceling of auxiliary machine driving torque. In addition, the engine control module 11 controls the injection amount and injection timing of the fuel injection valve 16 and the ignition timing by the spark plug 17. In FIG. 1, 18 indicates an air cleaner, 19 indicates a catalytic converter, and 20 indicates an exhaust silencer.

  In the above configuration, the steady reached boost pressure as the target value of the boost pressure is obtained according to the engine operating conditions, and the boost pressure control signal (duty signal) according to the steady reach boost pressure is used as the engine control. Output from the module 11 to the supercharging pressure control valve 12 to control the supercharging pressure. This supercharging pressure is controlled to a higher supercharging pressure in the high speed and high load range.

  On the other hand, the compression ratio is controlled toward the target compression ratio via the compression ratio control actuator 13 so as to be optimized according to the engine operating conditions. Basically, the compression ratio control is controlled so that the higher the supercharging pressure, the lower the compression ratio, and the lower the supercharging pressure, the higher the compression ratio. That is, during high supercharging operation, the compression ratio is lowered to avoid knocking, and during low supercharging operation, the compression ratio is kept high to improve thermal efficiency (improve fuel efficiency).

  3 and 4 are a control block diagram and a flowchart showing a control routine according to the first embodiment of the present invention. Such a control routine is repeatedly executed in the engine control module 11 every predetermined period (for example, every 10 ms or every predetermined crank angle). Note that the maps and tables shown in FIGS. 7 and 8 are set in advance and stored / stored in the memory of the engine control module 11. The same applies to second and third embodiments described later.

  In step (abbreviated as S in the figure) 1, the target compression ratio is calculated by searching (lookup) the target compression ratio setting map shown in FIG. 7 based on the accelerator opening corresponding to the required load and the engine speed. • Set (target compression ratio setting means). The accelerator opening is detected by the accelerator opening sensor 21 described above. The engine speed is calculated using the detection signal of the crank angle sensor 5.

  In step 2, the target throttle opening is calculated and set based on the accelerator opening (target throttle opening setting means). For example, as shown in Expression (1), the accelerator opening rAPO may be simply set as the target throttle opening tTVO.

tTVO = rAPO (1)
tTVO: target throttle opening degree rAPO: accelerator opening degree In step 3, the required torque reduction amount is calculated by the subroutine shown in FIG. 5 (required torque reduction amount calculation means). Referring to FIG. 5, in step 301, the required torque is calculated by searching the required torque calculation map shown in FIG. 8 from the accelerator opening. In step 302, it is determined whether the amount of decrease in the accelerator opening relative to the previous value is greater than a predetermined value. In step 303 and step 308, it is determined whether a flag fGENSOKU indicating a deceleration state is set. If this flag is set, it means that the vehicle is decelerating. At the start of deceleration, step 302 is positive, step 303 is negative, and steps 304 to 306 are executed. In step 304, the previous value of the required torque is stored as the required torque before deceleration. In step 305, the value of the request torque reduction amount calculated last time is held as the request torque reduction amount. In step 306, the flag fGENSOKU is set. If the vehicle is decelerating (deceleration continues except when deceleration starts), both step 302 and step 303 are affirmed and the process proceeds to step 307, where the value obtained by subtracting the current value of the required torque from the required torque before deceleration is obtained. Set and store as the amount of decrease. At the end of deceleration, Step 302 is negative, Step 308 is positive, and Step 309 and Step 310 are executed. In step 309, a value obtained by subtracting the current value of the required torque from the required torque before deceleration is set as the required torque reduction amount. In step 310, fGENSOKU indicating that the vehicle is decelerating is reset. For example, in an operating state other than deceleration, such as during engine acceleration or constant speed running, both step 302 and step 308 are denied, and the routine proceeds to step 311 where the required torque reduction amount is set to 0 (zero).

  In step 4 (FIGS. 3 and 4), at least one of the target compression ratio and the target throttle opening is corrected by the subroutine shown in FIG. 6 according to the required torque reduction amount (correction means). Specifically, in step 401, it is determined whether the required torque reduction amount ΔTe_demand exceeds a predetermined correction target switching determination threshold Th_ΔTe. The correction target switching determination threshold Th_ΔTe is, for example, a preset constant. In step 402, it is determined whether the required torque reduction amount ΔTe_demand exceeds 0 (zero).

  When the required torque decrease amount ΔTe_demand exceeds the correction target switching determination threshold value Th_ΔTe, that is, when the deceleration degree is relatively large, step 401 is affirmed and the process proceeds to step 403, and only the target compression ratio is decreased. to correct. Specifically, a final target compression ratio tε_lst after correction is calculated by subtracting a predetermined target compression ratio correction amount hε from the target compression ratio tε before correction. The target compression ratio correction amount hε is a constant set in advance for the purpose of simplifying the control, for example. Further, the target throttle opening tTVO before correction is set as it is as the final target throttle opening tTVO_lst.

  When the required torque reduction amount ΔTe_demand exceeds 0 and is equal to or smaller than the correction target switching determination threshold Th_ΔTe, that is, when the deceleration degree is relatively small, step 401 is negative, step 402 is affirmed, Proceeding to step 404, only the target throttle opening is corrected to the lower side. Specifically, the target throttle opening tTVO_lst after final correction is calculated by subtracting a predetermined target throttle opening correction amount hTVO from the target throttle opening tTVO before correction. The target throttle opening correction amount hTVO is a constant set in advance for simplification, for example. Further, the target compression ratio tε before correction is set as the final target compression ratio tε_lst as it is.

  When the required torque reduction amount ΔTe_demand is 0 or less, that is, when the vehicle is not decelerating, both step 401 and step 402 are negated and the process proceeds to step 405, and neither the target compression ratio nor the target throttle opening is corrected. . Specifically, the target compression ratio tε is set as the final target compression ratio tε_lst, and the target throttle opening tTVO is set as the final target throttle opening tTVO_lst.

  Referring to FIGS. 3 and 4 again, in step 5, a command signal corresponding to the final target compression ratio tε_lst is output to the compression ratio control actuator 13 to operate the engine compression ratio toward the target compression ratio tε_lst. Control (compression ratio control means).

  In step 6, a command signal corresponding to the final target throttle opening tTVO_lst is output to the actuator of the electrically controlled throttle valve 9, and the throttle opening is operated and controlled toward the target throttle opening tTVO_lst (throttle control means). .

  9 and 10 are a control block diagram and a flowchart showing a control routine according to the second embodiment of the present invention. This second embodiment is suitable for an engine in which the response of the intake air amount control by the throttle opening is higher than the response of the engine compression ratio control. Note that the processing contents from Step 1 to Step 3 are the same as those in the first embodiment, and redundant description is omitted.

  In step 14, the target compression ratio is corrected by a subroutine shown in FIG. 11 (target compression ratio correction means / correction means). Specifically, in step 41, a boost pressure equilibrium value estimation map shown in FIG. 13 is searched based on the accelerator opening, and a boost pressure equilibrium value corresponding to the target value is obtained. In step 42, the actual supercharging pressure is estimated by the following equation (2) (supercharging pressure estimating means).

Pc_d: actual supercharging pressure Pc_s: supercharging pressure equilibrium value Δt: sampling time τ: supercharging response delay time constant Δt is a constant and corresponds to a calculation interval. τ may be a constant or may be changed according to the operating state. z−1 is an operator representing a delay of one operation.

  In step 43, the engine torque equilibrium value estimation map of FIG. 14 is searched based on the target throttle opening before the restriction in step 19 described later, and the engine torque equilibrium value corresponding to a value at which the engine torque is steadily stabilized. Is calculated and set (equilibrium torque calculation means).

In step 44, based on the engine torque balance value, the actual boost pressure, and the boost pressure balance value, an estimated engine torque value corresponding to the actual engine torque is calculated by the following equation (3) (torque estimation means). .
yTe_d = Te_s × (Pc_s / Pc_d) (3)
yTe_d: engine torque estimated value Te_s: engine torque equilibrium value Pc_s: supercharging pressure equilibrium value Pc_d: actual supercharging pressure In step 45, based on the engine torque estimated value (actual torque estimated value), knock limit compression shown in FIG. The ratio estimation map is searched to obtain the knock limit compression ratio (upper limit compression ratio) (knock limit compression ratio calculation means).

  In step 46, the target compression ratio correction coefficient setting table shown in FIG. 16 is searched from the required torque reduction amount, and the target compression ratio correction coefficient is set (compression ratio correction coefficient setting means). As shown in FIG. 16, when the required torque reduction amount is larger than a predetermined threshold value Th1, the correction coefficient is held at 1 which is the maximum value. When the required torque reduction amount is equal to or less than the threshold value Th1, the correction coefficient decreases proportionally as the required torque reduction amount decreases.

In step 47, the target compression ratio is corrected by the following equation (4) using the target compression ratio correction coefficient.
tε_lst = tε− (tε−tε_lim) × Kε (4)
tε: target compression ratio before correction tε_lst: target compression ratio after correction tε_lim: knock limit compression ratio Kε: target compression ratio correction coefficient Referring again to FIG. 9 and FIG. A command signal corresponding to the target compression ratio tε_lst is output to the compression ratio control actuator 13 to control the engine compression ratio toward the target compression ratio tε_lst (compression ratio control means).

  In step 16, the actual compression ratio is detected. As an example, an angle sensor for detecting the angle of the control shaft 42 is provided, and an actual compression ratio is obtained based on a signal from the angle sensor.

  In step 17, the knock limit intake air amount estimation map of FIG. 17 is searched based on the actual compression ratio, and the knock limit intake air amount is calculated (knock limit intake air amount calculating means).

In step 18, the knock limit throttle opening estimation map shown in FIG. 12 is searched based on the knock limit intake air amount and the engine speed to estimate the knock limit throttle opening (knock limit throttle opening estimating means). However, in the engine provided with the turbocharger 51 as in the present embodiment, the pretreatment according to the equation (5) is preferably performed.
Qa_na_lim = Qa_c_lim × (Pa / Pc_d) (5)
Qa_na_lim: knock limit throttle opening degree estimation map search intake amount Qa_c_lim: knock limit intake amount Pa: atmospheric pressure Pc_d: actual boost pressure Pa may be a constant corresponding to atmospheric pressure.

  In step 19, the target throttle opening is limited by the knock limit throttle opening (target throttle opening limiting means). In other words, the target throttle opening is set with the knock limit throttle opening as the upper limit value. For example, the knock limit throttle opening may be simply set as the final target throttle opening, or the knock target throttle opening is corrected to a lower side according to the engine operating state, and the final target throttle opening is set. It may be calculated.

  In step 20, a command signal corresponding to the final target throttle opening is output to the actuator of the electric throttle valve 9 to control the throttle opening toward the target throttle opening (throttle control means).

  18 and 19 are a control block diagram and a flowchart showing a control routine according to the third embodiment of the present invention. This control routine is suitable for an engine in which the response of the engine compression ratio control is faster than the response of the intake air amount control based on the throttle opening. Note that the processing contents of steps 1 to 3 are the same as those in the first embodiment, and redundant description is omitted.

  In step 24, the target throttle opening is corrected by the subroutine shown in FIG. 20 (target throttle opening correction means / correction means). Specifically, as in steps 41 and 42 of the second embodiment, in step 51, the boost pressure equilibrium value estimation map shown in FIG. 13 is searched based on the accelerator opening to obtain the boost pressure equilibrium value. Then, the actual supercharging pressure is estimated by the above equation (2) (supercharging pressure estimating means).

  In step 53, the knock limit intake air amount estimation map of FIG. 22 is searched based on the target compression ratio before the restriction in step 28 described later, and the knock limit intake air amount is calculated / estimated (knock limit intake air amount calculating means). .

  In step 54, the knock limit intake air amount is corrected by the actual boost pressure by the following equation (6), and the knock limit throttle opening estimation map in FIG. 23 is searched based on the corrected intake air amount and engine speed. Thus, the knock limit throttle opening is obtained (knock limit throttle opening calculating means).

Qa_na_lim = Qa_c_lim × (Pa / Pc_d) (6)
Qa_na_lim: knock limit throttle opening degree estimation map search intake air amount Qa_c_lim: knock limit intake air amount Pa: atmospheric pressure Pc_d: supercharging pressure Pa may be a constant equivalent to atmospheric pressure.

  In step 55, the target throttle opening correction coefficient setting table shown in FIG. 24 is searched based on the required torque reduction amount, and the target throttle opening correction coefficient is set (throttle opening correction coefficient setting means). As shown in FIG. 24, when the required torque reduction amount is larger than a predetermined threshold value Th2, the correction coefficient is held at 1 which is the maximum value. When the required torque reduction amount is lower than the threshold value Th2, the correction coefficient decreases proportionally as the required torque reduction amount decreases.

In step 56, the target throttle opening degree is corrected by the equation (7) using the target throttle opening degree correction coefficient.
tTVO_lst = tTVO− (tTVO−tTVO_lim) × Ktvo (7)
tTVO: target throttle opening before correction tTVO_lst: target throttle opening after correction tTVO_lim: knock limit throttle opening Ktvo: target throttle opening correction coefficient Referring again to FIG. 18 and FIG. A command signal corresponding to the final target throttle opening tTVO_lst is output to the actuator of the throttle valve 9 to control the throttle opening toward the target throttle opening tε_lst (throttle control means).

  In step 26, the actual intake air amount is detected by the air flow meter 2, for example.

  In step 27, the knock limit compression ratio estimation map of FIG. 21 is searched based on the actual intake air amount, and the knock limit compression ratio is calculated (knock limit compression ratio calculating means).

  In step 28, the target compression ratio is limited by the knock limit compression ratio (target compression ratio limiting means). In other words, the target compression ratio is set with the knock limit compression ratio as the upper limit value. For example, the knock limit compression ratio may be set as it is as the final target compression ratio. Alternatively, the target compression ratio may be calculated by correcting the knock limit compression ratio to the lower side in accordance with the engine speed, the engine load, etc. in consideration of the durability of the variable compression ratio mechanism.

  In step 29, a command signal corresponding to the final target compression ratio is output to the compression ratio control actuator 13, and the engine compression ratio is operated / controlled toward the target compression ratio (compression ratio control means).

  The invention which can be grasped | ascertained from the above Example is listed with the effect. Corresponding examples are appended.

(1) 1st invention (corresponding to the first to third embodiments)
Target compression ratio setting means for setting the target compression ratio according to the accelerator opening, compression ratio control means for controlling the engine compression ratio according to the target compression ratio, and target throttle opening according to the accelerator opening Target throttle opening setting means for controlling, throttle control means for controlling the throttle opening according to the target throttle opening, and at least the target compression ratio or the target throttle opening during engine deceleration when the accelerator opening decreases. Correction means for temporarily correcting one of them to the lower side.

  According to the first aspect of the present invention, during engine deceleration, at least one of the target compression ratio and the throttle opening is temporarily lowered to suppress at least one of charging efficiency or intake air amount, thereby transiently during engine deceleration. In addition, it is possible to prevent both the engine compression ratio and the intake air amount from inadvertently increasing, and to reliably avoid the occurrence of knocking.

(2) Second invention (corresponding to the first embodiment)
In the first aspect of the invention, there is further required torque reduction amount calculating means for calculating the required torque reduction amount. The correction means temporarily corrects only the target compression ratio when the required torque reduction amount is larger than a predetermined value, and when the required torque reduction amount is smaller than the predetermined value, the target throttle opening is corrected. Only the degree is temporarily corrected to the lower side.

  If the torque reduction required by the driver is small, that is, if the degree of deceleration is relatively small, the throttle opening is reduced while maintaining the fuel efficiency without correcting the compression ratio. Correct to avoid knocking. The effect on drivability by reducing the throttle opening is not a problem in practice because the required torque reduction amount is small. Conversely, when the amount of torque reduction required by the driver is large, that is, when the degree of deceleration is relatively large, it is considered that the influence on the drivability by reducing the throttle opening is large. Without the correction, the compression ratio is corrected to the lower side to avoid the occurrence of knocking. Accordingly, it is possible to reliably avoid the occurrence of knocking while effectively suppressing a decrease in fuel consumption performance during engine deceleration while having a simple control configuration of switching between correction of the compression ratio and correction of the throttle opening. it can.

(3) Third invention (corresponding to the second embodiment)
In the first invention, a required torque reduction amount calculating means for calculating a required torque reduction amount, a target compression ratio correction means for correcting the target compression ratio to the lower side according to the required torque reduction amount, and an actual compression ratio An actual compression ratio detecting means for detecting a knock limit intake air amount calculating means for calculating a knock limit intake air amount corresponding to a knock limit based on the actual compression ratio, and a target throttle opening based on the knock limit intake air amount. And target throttle opening restriction means for restricting.

  If the correction target is switched by the required torque reduction amount as in the second aspect of the invention, the torque response waveform may change abruptly at the predetermined required torque reduction amount, which may cause a sense of incongruity. On the other hand, in the third invention, both the correction amount of the compression ratio and the correction amount of the throttle opening can be changed (continuously) according to the required torque reduction amount. Therefore, it is possible to avoid the uncomfortable feeling associated with the switching of the correction object as in the second aspect of the invention, and the operability is improved.

  In addition, the third aspect of the invention is suitable for a device having a quick throttle opening response rather than a compression ratio response. The reason will be described. The target compression ratio is corrected in accordance with the required torque reduction amount, the final target compression ratio is set, and the engine compression ratio is controlled toward this target compression ratio. However, the actual engine compression ratio inevitably has a response delay with respect to the target compression ratio. Therefore, an actual compression ratio corresponding to the actual engine compression ratio is detected, and a knock limit intake air amount corresponding to a limit for preventing knocking is obtained according to the actual compression ratio, and based on this knock limit intake air amount. The target throttle opening is limited. By avoiding the final knock by restricting the throttle opening (intake amount) that responds quickly, the occurrence of knock can be avoided more accurately than when the final knock avoidance is performed by limiting the compression ratio. It has excellent control accuracy.

(4) Fourth invention (corresponding to the second embodiment)
The target compression ratio correcting means of the third invention is based on the actual boost pressure estimating means for estimating the actual boost pressure based on the accelerator opening, and the target throttle opening before the restriction by the target throttle opening restricting means. , An equilibrium torque calculation means for calculating an engine torque equilibrium value at which the engine torque is stably stabilized, a torque estimation means for estimating an engine torque estimated value based on the engine torque balance value and the actual supercharging pressure, Knock limit compression ratio calculation means for calculating a knock limit compression ratio corresponding to the knock limit based on the estimated engine torque value, and based on the required torque reduction amount and the knock limit compression ratio, the target compression ratio Correct.

  The fourth aspect of the invention limits the target compression ratio correction method of the third aspect of the invention. In the fourth aspect of the invention, a limit compression ratio for preventing knocking is obtained, and this value is used when correcting the target compression ratio. Typically, the target compression ratio is corrected with the knock limit compression ratio as the lower limit value. As a result, the target compression ratio is not lowered more than necessary to reduce the fuel efficiency, and the fuel efficiency can be sufficiently obtained while knocking is avoided.

  This fourth invention is suitable for an engine equipped with a supercharger and estimates the supercharging pressure. However, in the case of a naturally aspirated engine, it is necessary to estimate the actual supercharging pressure. Instead, it can be handled by substituting a value corresponding to atmospheric pressure.

(5) Fifth invention (corresponding to the third embodiment)
In the first aspect of the invention, further, a required torque reduction amount calculating means for calculating the required torque reduction amount, a target throttle opening correction means for correcting the target throttle opening to the lower side according to the required torque reduction amount, and actual intake air An actual intake amount detecting means for detecting the amount, a knock limit compression ratio calculating means for calculating a knock limit compression ratio corresponding to the knock limit based on the actual intake amount, and a target compression ratio based on the knock limit compression ratio. And target compression ratio limiting means for limiting.

  As in the third invention, the fifth invention eliminates sudden switching of the correction target and does not give a sense of incongruity. In contrast to the third invention, the fifth invention is suitable when the response of the compression ratio control is faster than the response of the intake air amount control based on the throttle opening. The reason for this is that even if the target throttle opening is corrected according to the required torque reduction amount, the final target throttle opening is set, and the throttle opening is controlled toward this target throttle opening. The actual actual intake amount is inevitably accompanied by a response delay with respect to the target throttle opening. Therefore, the actual intake air amount is detected, and based on this actual intake air amount, a limit compression ratio for preventing knocking is obtained, and the target compression ratio is limited. By performing the final knock avoidance by limiting the compression ratio with excellent responsiveness, it is possible to avoid the occurrence of knock more effectively and accurately than when performing the final knock avoidance by limiting the throttle opening. It has excellent control accuracy.

(6) Sixth invention (corresponding to the third embodiment)
The target throttle opening correction means according to the fifth aspect of the present invention includes a boost pressure estimation means for estimating an actual boost pressure based on the accelerator opening, and a knock based on a target compression ratio before the restriction by the target compression ratio restriction means. Knock limit intake air amount calculating means for calculating the knock limit intake air amount corresponding to the limit, and the knock limit throttle for calculating the knock limit throttle opening corresponding to the knock limit based on the knock limit intake air amount and the actual supercharging pressure. Opening degree calculation means, and correct the target throttle opening degree based on the required torque reduction amount and the knock limit throttle opening degree.

  The sixth aspect of the invention limits the method for correcting the target throttle opening degree of the fifth aspect of the invention. In the sixth aspect of the invention, a limit intake amount for preventing knocking is obtained, and the target throttle opening is corrected based on the knock limit throttle opening which is the throttle opening for realizing this value. Typically, correction is performed with the knock limit throttle opening as the lower limit. As a result, it is possible to reliably avoid the occurrence of knocking without reducing the target throttle opening more than necessary and hindering the torque response.

  The sixth aspect of the invention is suitable for an engine equipped with a supercharger and estimates the supercharging pressure. However, in the case of a naturally aspirated engine, there is no need to estimate the supercharging pressure. It is possible to cope with this by setting a value corresponding to atmospheric pressure.

(7) Seventh invention (corresponding to first to third embodiments)
A lower link that is rotatably fitted to a crankpin of the crankshaft, an upper link that links the lower link and the piston, and a control link that is connected to the lower link at one end. And a variable compression ratio mechanism that makes the engine compression ratio variable by changing the motion restraint condition of the lower link.

  In addition to being able to continuously change the engine compression ratio, this variable compression ratio mechanism is compact and excellent in engine mountability, and can optimize the piston stroke characteristics themselves.

(8) Eighth invention (corresponding to first to third embodiments)
The intake air amount can be adjusted not only by the throttle opening by the throttle valve, but also by a variable valve mechanism that changes the valve timing and valve lift characteristics of the intake valve and the exhaust valve, for example. The above-described invention can be applied. Therefore, “throttle opening” in the above description may be replaced with “valve timing”, “valve lift characteristics”, or “intake amount” in a broad sense as in the following eighth invention.

  Target compression ratio setting means for setting a target compression ratio according to the accelerator opening, compression ratio control means for controlling the engine compression ratio according to the target compression ratio, and a target intake air amount according to the accelerator opening The target intake air amount setting means, the intake air amount control means for controlling the intake air amount according to the target intake air amount, and at least one of the target compression ratio or the target intake air amount during the engine deceleration with the accelerator opening decreased temporarily. And a correction means for correcting to the lower side.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the whole structure of the control apparatus of the variable compression ratio internal combustion engine which concerns on this invention. Structure explanatory drawing which shows the structure of a variable compression ratio mechanism. The block diagram which shows the flow of control which concerns on 1st Example of this invention. The flowchart which shows the flow of control which concerns on the said 1st Example. Required torque reduction amount calculation subroutine. Target compression ratio / target throttle opening correction subroutine. Target compression ratio setting map. Required torque calculation map. The block diagram which shows the flow of control which concerns on 2nd Example of this invention. The flowchart which shows the flow of control concerning the said 2nd Example. Target compression ratio correction subroutine. Knock limit throttle opening estimation map. Supercharging pressure equilibrium value estimation map. Engine torque equilibrium value estimation map. Knock limit compression ratio estimation map. Target compression ratio correction coefficient setting table. Knock limit intake air amount estimation map. The block diagram which shows the flow of control which concerns on 3rd Example of this invention. The flowchart which shows the flow of control which concerns on the said 3rd Example. Target throttle opening correction subroutine. Knock limit compression ratio estimation map. Knock limit intake air amount estimation map. Knock limit throttle opening estimation map. Target throttle opening correction coefficient setting table. Explanatory drawing which shows the change of the intake air amount and compression ratio during engine deceleration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Variable compression ratio internal combustion engine 11 ... Engine control module 13 ... Compression ratio control actuator 51 ... Turbocharger

Claims (10)

Target compression ratio setting means for setting a target compression ratio according to the accelerator opening;
Compression ratio control means for controlling the engine compression ratio according to the target compression ratio;
Target throttle opening setting means for setting the target throttle opening according to the accelerator opening;
Throttle control means for controlling the throttle opening in accordance with the target throttle opening;
A required torque amount calculating means for calculating a required torque decrease amount;
Correction means for temporarily correcting at least one of the target compression ratio or the target throttle opening to a lower side according to the required torque reduction amount during engine deceleration in which the accelerator opening decreases;
A control apparatus for a variable compression ratio internal combustion engine. Upper Symbol correcting means, when the amount of required torque reduction is larger than a predetermined value, corrects only the target compression ratio to temporarily drop side, when the amount of required torque reduction is smaller than a predetermined value, the target throttle The control apparatus for a variable compression ratio internal combustion engine according to claim 1, wherein only the opening degree is temporarily corrected to a lower side. The correction means is
First correction means for temporarily correcting one of the target compression ratio and the target throttle opening to a lower side according to the required torque reduction amount;
Second correction means for correcting the other of the target compression ratio and the target throttle opening based on a knock limit value corresponding to a knock limit;
The control apparatus for a variable compression ratio internal combustion engine according to claim 1, comprising: An actual compression ratio detecting means for detecting an actual compression ratio;
A knock limit intake air amount calculating means for calculating a knock limit intake air amount corresponding to the knock limit based on the actual compression ratio,
The correction means is
Target compression ratio correction means for correcting the target compression ratio to the lower side according to the required torque reduction amount;
4. The control device for a variable compression ratio internal combustion engine according to claim 3 , further comprising target throttle opening restriction means for restricting a target throttle opening based on the knock limit intake air amount. The target compression ratio correcting means is
An actual boost pressure estimating means for estimating the actual boost pressure based on the accelerator opening;
On the basis of the target throttle opening before the restriction by the target throttle opening restriction means, an equilibrium torque calculating means for calculating an engine torque equilibrium value at which the engine torque is stably stabilized;
Torque estimating means for estimating an engine torque estimated value based on the engine torque equilibrium value and the actual boost pressure;
A knock limit compression ratio calculating means for calculating a knock limit compression ratio corresponding to the knock limit based on the estimated engine torque value,
The control apparatus for a variable compression ratio internal combustion engine according to claim 4 , wherein the target compression ratio is corrected based on the required torque reduction amount and the knock limit compression ratio. An actual intake air amount detecting means for detecting the actual intake air amount;
A knock limit compression ratio calculating means for calculating a knock limit compression ratio corresponding to the knock limit based on the actual intake air amount;
The correction means is
A required torque reduction amount calculating means for calculating the required torque reduction amount;
Target throttle opening correction means for correcting the target throttle opening to the lower side according to the required torque reduction amount;
Target compression ratio limiting means for limiting the target compression ratio based on the knock limit compression ratio;
The control apparatus for a variable compression ratio internal combustion engine according to claim 3 , comprising: The target throttle opening correction means is
Supercharging pressure estimating means for estimating the actual supercharging pressure based on the accelerator opening;
A knock limit intake air amount calculating means for calculating a knock limit intake air amount corresponding to the knock limit based on the target compression ratio before the restriction by the target compression ratio restricting means;
Knock limit throttle opening calculating means for calculating a knock limit throttle opening corresponding to the knock limit based on the knock limit intake air amount and the actual boost pressure,
The control apparatus for a variable compression ratio internal combustion engine according to claim 6 , wherein the target throttle opening is corrected based on the required torque reduction amount and the knock limit throttle opening. A lower link that is rotatably fitted to a crankpin of the crankshaft, an upper link that links the lower link and the piston, and a control link that is connected to the lower link at one end. The control apparatus for a variable compression ratio internal combustion engine according to any one of claims 1 to 7 , further comprising a variable compression ratio mechanism that makes the engine compression ratio variable by changing a motion constraint condition of the lower link. Target compression ratio setting means for setting a target compression ratio according to the accelerator opening;
Compression ratio control means for controlling the engine compression ratio according to the target compression ratio;
Target intake air amount setting means for setting a target intake air amount in accordance with the accelerator opening;
An intake air amount control means for controlling the intake air amount according to the target intake air amount;
A required torque amount calculating means for calculating a required torque decrease amount;
Correction means for temporarily correcting at least one of the target compression ratio or the target intake air amount to a lower side according to the required torque decrease amount during engine deceleration in which the accelerator opening decreases;
A control apparatus for a variable compression ratio internal combustion engine. Set the target compression ratio and target throttle opening at least according to the accelerator opening,
Calculate the required torque reduction amount,
During engine deceleration in which the accelerator opening is reduced , according to the required torque reduction amount, at least one of the target compression ratio or the target throttle opening is temporarily corrected to the lower side,
A control method for a variable compression ratio internal combustion engine, which controls an engine compression ratio and a throttle opening toward a corrected target compression ratio and a target throttle opening.

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