JP2012193635A - Device for controlling variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid interference between an intake/exhaust valve and a piston due to elongation of a timing chain, and to suppress decrease in operation performance without generating knocking.SOLUTION: A control device includes a variable compression ratio mechanism changing an engine compression ratio in accordance with an engine operating condition by changing a top dead center position of a piston. An elongation amount (dL) of a timing chain is estimated on the basis of a rotation phase difference between a crankshaft and camshaft. A target compression ratio (tCR) is corrected in accordance with the elongation amount (dL) of the timing chain. In contrast to a case when the elongation amount of the chain is small (A), when the elongation amount of the chain is large (B), the target compression ratio is corrected to the increase side so that decrease in torque is compensated in a region A at a low rotation high torque side. In a region C at a high rotation side and a low load side, the target compression ratio is corrected to a lower side to avoid interference between the intake/exhaust valve and the piston, and the generation of knocking is suppressed.

Description

  The present invention relates to a variable compression ratio internal combustion engine in which an engine compression ratio can be changed according to an engine operating state, and more particularly to correction control of an engine compression ratio according to an extension amount of a timing chain.

  As is well known, in an internal combustion engine, crankshaft crank sprockets and camshaft cam sprockets are used to transmit crankshaft rotational power to intake valves and exhaust valves (camshafts that drive intake and exhaust valves). The timing chain is wound around.If the timing chain is extended due to aging, wear, etc., the camshaft phase with respect to the crankshaft is shifted in the direction of delaying, so that the valve timing of the intake and exhaust valves is delayed. However, there is a possibility that the drivability is lowered and the intake / exhaust valve and the piston interfere with each other.

  As a countermeasure, Patent Document 1 detects a phase shift of the camshaft with respect to the crankshaft, and determines that the timing chain is extended when this phase shift is equal to or greater than a predetermined threshold value. Warning lights and buzzers warn the user, prompt parts replacement and maintenance, and forcibly stop the internal combustion engine. In addition, when a variable valve timing mechanism for changing the valve timing is provided, the valve timing is corrected by correcting the valve timing in the direction in which the phase shift is eliminated, that is, in the advance direction when the phase shift is detected. Is approximated to a normal phase state.

JP 2002-309994 A

  However, if a warning is issued or the internal combustion engine is forcibly stopped when an extension of the timing chain is detected, parts replacement becomes necessary, or the internal combustion engine cannot be operated, and the desired engine operating state is It cannot be continued. Further, when the advance angle correction is performed by the valve timing mechanism, it cannot be applied to an internal combustion engine that does not include the valve timing mechanism, and the valve timing cannot be converted to a normal phase state due to restrictions on the control range of the valve timing mechanism. In some cases, the desired operating state cannot be continued, and there is room for improvement.

  The present invention has been made in view of such circumstances. That is, in the control device for a variable compression ratio engine according to the present invention, the variable compression ratio means for changing the engine compression ratio according to the engine operating state by changing the top dead center position of the piston, and the rotational power of the crankshaft. A timing chain is provided between the crank sprocket of the crankshaft and the cam sprocket of the camshaft so as to transmit to the camshaft that drives the intake and exhaust valves. A phase difference detecting means for detecting a rotational phase difference between the crankshaft and the camshaft; and a chain extension amount for estimating an extension amount of the timing chain based on the rotational phase difference detected by the phase difference detecting means. It has an estimation means and a compression ratio correction means for correcting the engine compression ratio based on the estimated value of the amount of elongation of the timing chain.

  According to the present invention, by correcting the engine compression ratio in accordance with the amount of extension of the timing chain, it is possible to avoid the interference between the valve and the piston due to the extension of the timing chain, and to suppress a decrease in the operating state. The intended engine operation can be continued without replacing parts or forcibly stopping the engine.

The system block diagram which shows the control apparatus of the variable compression ratio internal combustion engine which concerns on 1st Example of this invention. The block diagram which shows the vicinity of the timing chain of the said variable compression ratio internal combustion engine. The control block diagram of the said 1st Example. The flowchart which shows the flow of the compression ratio control which concerns on the said 1st Example. The setting map of the target compression ratio which concerns on the said 1st Example is shown, (A) is explanatory drawing when the amount of elongation of a timing chain is small, (B) is the case where the amount of elongation of a timing chain is large. Explanatory drawing by the correction | amendment of the target compression ratio by the low rotation high load side in the said 1st Example. The system block diagram which shows the control apparatus of the variable compression ratio internal combustion engine which concerns on 2nd Example of this invention. The control block diagram of the said 2nd Example. The flowchart which shows the flow of control concerning the said 2nd Example. Explanatory drawing which shows typically the correction | amendment operation conditions of the variable intake valve timing mechanism of the said 2nd Example, and a variable compression ratio mechanism.

  Hereinafter, the present invention will be described with reference to illustrated embodiments. FIG. 1 shows a system configuration diagram of a control apparatus for a variable compression ratio internal combustion engine according to a first embodiment of the present invention. In this internal combustion engine, variable compression using a multi-link type piston-crank mechanism as variable compression ratio means for changing the engine compression ratio according to the engine operating state by changing the top dead center position of the piston 12. A ratio mechanism 20 is provided. Since this variable compression ratio mechanism 20 is known as described in Japanese Patent Application Laid-Open No. 2005-30223 and the like, it will be briefly described. That is, two links connecting the crankshaft 13 and the piston 12, that is, the crankshaft 13. The lower link 22 is rotatably attached to the crankpin 14, and the upper link 21 is connected to the piston 12 and the lower link 22. One end of the control link 23 is attached to the lower link 22. Then, by changing the rotational position of the control shaft 24 by the variable compression ratio actuator 4, the position of the other end serving as the oscillating fulcrum of the control link 23 changes, and the motion constraint condition of the lower link 22 changes, and the piston The engine compression ratio changes with a change in the top dead center position.

  Further, in this internal combustion engine, as sensors for detecting the engine operating state, the crank angle sensor 1 for detecting the rotation angle of the crankshaft 13 and the intake air for detecting the rotation angle of the intake camshaft 16 for driving the intake valve 15 to open and close. The cam angle sensor 2, the exhaust cam angle sensor 3 that detects the rotation angle of the exhaust cam shaft 18 that drives the exhaust valve 17 to open and close, and the compression ratio sensor that detects the engine compression ratio (actual compression ratio) are provided. The variable compression ratio actuator 4 and the accelerator pedal sensor 7 for detecting the accelerator opening of the accelerator pedal operated by the driver are connected to an engine control unit 11 having a function of storing and executing various control processes. . Based on the signal from the engine control unit 11, the variable compression ratio actuator 4 outputs a drive signal to the spark plug 19 for spark ignition of the air-fuel mixture in the combustion chamber in addition to the variable compression ratio mechanism 21 described above. Control the behavior.

  Referring to FIG. 2, crank sprocket 13 </ b> A of crankshaft 13, cam sprocket 16 </ b> A of intake camshaft 16, and exhaust camshaft 18 are transmitted so that the rotational power of crankshaft 13 is transmitted to intake camshaft 16 and exhaust camshaft 18. The timing chain 8 is spanned across the cam sprocket 18A. A chain tensioner 9 for adjusting the tension of the timing chain 8 is provided.

  FIG. 3 is a control block diagram schematically showing the control contents of the present embodiment stored and executed by the engine control unit 11 described above. The load calculation unit B1 calculates a required load (tT) from the output of the accelerator pedal sensor 7, and outputs it to the target compression ratio calculation unit B7. The rotation speed calculation unit B2 calculates the rotation speed (NE) and the rotation speed change rate (dNE) from the output of the crank angle sensor 1, and calculates the rotation speed (NE) from the target compression ratio calculation unit B7 and the intake / exhaust valve timing. While outputting to part B3, B4, a rotational speed change rate (dNE) is output to timing chain elongation amount calculating part B6. The intake valve timing calculation unit B3 calculates the intake valve timing (rVTI) from the output of the intake cam angle sensor 2 and the rotational speed (NE), and outputs it to the target compression ratio calculation unit B7 and the timing chain elongation amount calculation unit B6. . The exhaust valve timing calculation unit B4 calculates the exhaust valve timing (rVTE) from the output of the exhaust cam angle sensor 3 and the rotational speed (NE), and outputs it to the target compression ratio calculation unit B7. The compression ratio calculation unit B5 calculates the actual compression ratio (rCR) from the output of the compression ratio sensor 4 and outputs it to the target compression ratio calculation unit B7. The timing chain elongation amount calculation unit B6 as chain elongation amount estimation means calculates the timing chain elongation amount (dL) from the rotational speed change rate (dNE) and the intake valve timing (rVTI), and outputs it to the target compression ratio calculation unit B7. To do. Note that the exhaust timing (rVTE) may be used in place of the intake valve timing (rVTI) in the timing chain elongation amount calculation unit B6. The target compression ratio calculation unit B7 calculates a target compression ratio (tCR) from the above-described tT, NE, dL, rVTI, rVTE, and rCR, and outputs the target compression ratio (tCR) to the variable compression ratio actuator 4. As a result, the variable compression ratio actuator 20 drives and controls the variable compression ratio mechanism 20 toward the target compression ratio (tCR).

  FIG. 4 is a flowchart showing the flow of the compression ratio control of this embodiment. In step S1, the outputs of the accelerator pedal sensor 7, the crank angle sensor 1, the intake cam angle sensor 2, the exhaust cam angle sensor 3, the compression ratio sensor 4 and the like are read, and the process proceeds to step S2. In step S2, the output from the accelerator pedal sensor 7 is the target load (tT), the output from the crank angle sensor 1 is the rotational speed (NE), the rotational speed change rate (dNE) that is the rotational speed change per unit time, and the intake cam angle. The intake valve timing (rVTI) is calculated from the output of the sensor 2, the exhaust valve timing (rVTE) is calculated from the output of the exhaust cam angle sensor 3, and the actual compression ratio (rCR) is calculated from the output of the compression ratio sensor 4, and the process proceeds to step S3. In step S3, the rotational speed change rate (dNE) is compared with a predetermined value (determination threshold). When the rotational speed change rate (dNE) is smaller than the predetermined value, the process proceeds to step S4. When the rotational speed change rate (dNE) is equal to or larger than the predetermined value, the rotational speed variation is large and the amount of timing chain elongation (dL ) Is difficult to estimate, step S4 is skipped and step S5 follows. In step S4, a timing chain elongation amount (dL) is calculated from the intake valve timing (rVTI), and the process proceeds to step S5. The timing chain elongation (dL) may be calculated by using the exhaust valve timing (rVTE) instead of the intake valve timing (rVTI). In step S5, the target compression ratio tCR is calculated from the above tT, NE, dL, rVTI, rVTE, and rCR, and the process proceeds to step S6. In step S6, a drive signal corresponding to the target compression ratio tCR is output to the variable compression ratio actuator 4, and this routine ends.

  FIG. 5 shows setting maps used for setting the target compression ratio (tCR) in the target compression ratio calculation unit B7. These maps are set and adapted in advance and stored in the engine control unit 11. Has been. The target compression ratio (tCR) is set by looking up the setting map from the rotation speed (NE) and the target load (tT). Here, in this embodiment, a plurality of setting maps are switched according to the chain elongation amount (dL), thereby correcting the target compression ratio (tCR) according to the chain elongation amount (dL). Yes.

  FIG. 5A shows a setting map when the timing chain elongation amount (dL) is small, that is, when the target compression ratio (tCR) is not substantially corrected by the amount of elongation of the timing chain. FIG. 5B shows a setting map when the chain elongation amount (dL) is large and the target compression ratio (tCR) is actually corrected according to the chain elongation amount (dL). It should be noted that the setting of the area and the specific numerical values of the target compression ratio (tCR) shown in the drawing are merely examples, and the present invention is not limited to this.

  As shown in FIG. 5A, the target compression ratio (tCR) is basically set as much as possible within a range that does not cause knocking or excessive increase in exhaust temperature so as to increase thermal efficiency. It is set to a high value, and is set to a value on the high compression ratio side as the target load decreases and the rotational speed increases. Specifically, in the region A on the low rotation high load side where knocking is likely to occur, the minimum compression ratio (tCR = 10), the region C on the high rotation low load side where knocking is unlikely to occur (the region on the high rotation side and the region on the low load side). The upper limit compression ratio (tCR = 14) is set in the area combined with the area), and the intermediate value (tCR = 12) is set in the area B of the intermediate load / rotation speed between the two.

  On the other hand, when the elongation amount (dL) of the timing chain becomes large, the target compression ratio (tCR) is set as shown in FIG. That is, tCR = 11 is set in the region A on the low rotation high load side, and tCR = 12 is set in the intermediate region B. Further, the region C on the high rotation / low load side which is normally set to the upper limit compression ratio (tCR = 14) is divided into the region C′2 on the high rotation side and the remaining region C ′ on the low / medium rotation and low load side. In the region C′1, the upper limit compression ratio is decreased tCR = 13, and in the region C′2, the compression ratio is further decreased tCR = 12.

  The details of correction of the compression ratio in each region will be described in detail. In the region A on the low rotation and high load side, the closing timing of the intake valve 15 is retarded by the expansion of the timing chain, and the effective compression ratio is reduced. Thermal efficiency is reduced, and as a result, the torque output by the engine is reduced. On the other hand, since the effective compression ratio is lowered, it is difficult for knocking to occur, and the limit compression ratio at which knocking occurs is high. Therefore, in the region A on the low rotation high load side, when the elongation (dL) of the timing chain increases, the target compression ratio is corrected to the high compression ratio side (tCR10 → 11), thereby causing knocking. Without reducing the timing efficiency, it can compensate for the decrease in torque due to the timing chain elongation, close to the normal engine output torque with little (or no) elongation of the timing chain, A decrease in drivability due to elongation can be suppressed.

  With reference to FIG. 6, further description will be given of the effect of suppressing the torque reduction due to the extension of the timing chain by correcting the target compression ratio to the high compression ratio side in the region A on the low rotation high load side. . FIG. 6 shows changes in ignition timing and torque in the region A on the low rotation high load side. A characteristic L0 indicates a characteristic when the chain elongation amount is small (compression ratio = 10), and characteristics L1 and L2 indicate a characteristic when the chain elongation amount is large. Here, L1 indicates the characteristics of this embodiment (compression ratio = 11) in which the target compression ratio is corrected to the high compression ratio side, and L2 indicates the characteristics of a comparative example (compression ratio = 10) in which the target compression ratio is not corrected. Compared to L1 and L2 when the chain stretch is large and L0 when the chain stretch is small, the torque is reduced due to the lowering of the charging efficiency and the lowering of the thermal efficiency, but knocking occurs as the effective compression ratio decreases. The ignition timing is advanced. Here, in the present embodiment L1, although the charging efficiency is not improved so much, the target compression ratio is increased, so the thermal efficiency is improved, and the torque at the ignition timing at which knocking does not occur is improved, compared with the comparative example L2. Thus, it is possible to approach the normal characteristic L0 with a small chain elongation.

  Referring again to FIG. 5, when the chain elongation amount (dL) is large, the high rotation low load side region C set to the upper limit compression ratio as described above is referred to as the high rotation side region C′2. The point of correcting the target compression ratio in two parts, that is, the remaining low / medium rotation / low load side region C′1 will be described.

  In the region C′1 on the low / medium rotation / low load side, the upper limit of the target compression ratio is lowered (tCR = 14 → 13) to maintain the distance between the piston crown and the valve when the valve overlaps. This prevents the piston and valve from interfering with each other.

  On the other hand, in the high rotation region shown in region C′2, the pressure in the exhaust pipe is relatively high and the exhaust temperature is also high, so that the timing chain is extended and the closing timing of the exhaust valve 17 is retarded. In particular, high temperature residual gas increases and knocking is likely to occur. For this reason, the operation is performed with the target compression ratio further lower than that in the region C′1, thereby preventing performance degradation due to occurrence of knocking or ignition timing retardation.

  That is, in the region C on the high rotation low load side set to the upper limit compression ratio, when the amount of extension (dL) of the timing chain is large, the upper limit value of the target compression ratio is avoided in order to avoid interference between the piston and the valve. (TCR = 14 → 13), the target compression ratio is further reduced in the high-rotation region C2 ′ in order to suppress the deterioration in performance due to the occurrence of knocking or the ignition timing delay ( tCR = 14 → 12).

  Next, a second embodiment of the present invention will be described with reference to FIGS. Since the second embodiment basically has the same configuration and operational effects as the first embodiment, the same reference numerals are given to the same components and the description thereof will be omitted as appropriate, and the first embodiment will mainly be described. Differences from the embodiment will be described. FIG. 7 shows a system configuration diagram of the second embodiment. A variable intake valve timing mechanism 5 capable of changing the valve timing (opening / closing timing) of the intake valve 15 and a variable exhaust valve capable of changing the valve timing (opening / closing timing) of the exhaust valve 17 with respect to the system configuration of the first embodiment. A timing mechanism 6 is added. Since these variable valve timing mechanisms 5 and 6 are known as described in Japanese Patent Application Laid-Open No. 2008-95610 and the like, description thereof is omitted here. The engine control unit 11 outputs drive signals to the actuators of these variable valve timing mechanisms 5 and 6 (hereinafter referred to as the variable intake valve timing actuator 5 and the variable exhaust valve timing actuator 6), and controls their operations.

  FIG. 8 shows a control block diagram of the present embodiment. The load calculation unit B1 calculates a required load (tT) from the output of the accelerator pedal sensor 7, and outputs it to the target compression ratio calculation unit B7 and the target valve timing calculation unit B8. The rotation speed calculation unit B2 calculates the rotation speed (NE) and the rotation speed change rate (dNE) from the output of the crank angle sensor 1, and calculates the rotation speed (NE) as a target compression ratio calculation unit B7 and a target valve timing calculation unit B8. Are output to the intake / exhaust valve timing calculation units B3 and B4, and the rotational speed change rate (dNE) is output to the timing chain elongation amount calculation unit B6. The intake valve timing calculation unit B3 calculates the intake valve timing (rVTI) from the output of the intake cam angle sensor 2 and the rotational speed (NE), and outputs it to the target valve timing calculation unit B8 and the timing chain extension amount calculation unit B6. The exhaust valve timing calculation unit B4 calculates the exhaust valve timing (rVTE) from the output of the exhaust cam angle sensor 3 and the rotational speed (NE), and outputs it to the target valve timing calculation unit B8. The compression ratio calculation unit B5 calculates an actual compression ratio (rCR) from the output of the compression ratio sensor 4, and outputs it to the target valve timing calculation unit B8 and the target compression ratio calculation unit B7. The timing chain extension amount calculation unit B6 calculates the timing chain extension amount (dL) from the rotation speed change rate (dNE) and the intake valve timing (rVTI), and outputs the calculated timing chain extension amount (dL) to the target valve timing calculation unit B8 and the target compression ratio calculation unit B7. To do. The target valve timing calculation unit B8 calculates the target intake valve timing (tVTI) and the target exhaust valve timing (tVTE) from the above-described tT, NE, dL, rVTI, rVTE, rCR, the variable intake valve timing actuator 5, the variable exhaust It outputs to the valve timing actuator 6 and the target compression ratio calculation unit B7. As a result, the variable intake valve timing mechanism 5 is driven and controlled toward the target intake valve timing (tVTI), and the variable exhaust valve timing mechanism 6 is driven and controlled toward the target exhaust valve timing (tVTE). The target compression ratio calculation unit B7 calculates a target compression ratio (tCR) from the above-described tT, NE, dL, tVTI, tVTE, and rCR, and outputs the target compression ratio (tCR) to the variable compression ratio actuator 4. As a result, the variable compression ratio actuator 20 drives and controls the variable compression ratio mechanism 20 toward the target compression ratio (tCR).

  FIG. 9 is a flowchart showing the flow of the compression ratio control of this embodiment. Steps S1 to S4 are the same as those in the first embodiment shown in FIG. In step S5A, the target intake valve timing (tVTI) and the target exhaust valve timing (tVTE) are calculated from the above tT, NE, dL, rVTI, rVTE, and rCR, and the process proceeds to step S5. In step S5, a target compression ratio tCR is calculated from the above tT, NE, dL, tVTI, tVTE, and rCR, and the process proceeds to step S6A. In step S6A, a variable intake valve timing actuator drive signal is calculated from tVTI, a variable exhaust valve timing actuator drive signal is calculated from tVTE, and a variable compression ratio actuator drive signal is calculated from tCR, and is output to each actuator.

  Referring to FIG. 10, when the timing chain is extended in this embodiment, the variable intake valve timing mechanism 5 changes and corrects the intake valve timing, and the variable intake valve timing mechanism 5 can be adjusted in accordance with the correction. The conditions for correcting the target compression ratio by the compression ratio mechanism 20 will be described.

  The range in which IVC can be set as the amount of extension of the timing chain 8 increases with respect to the range A1 of the intake valve closing timing (IVC) that can be set by the variable intake valve timing mechanism 5 in a state where the timing chain 8 is not extended. The angle is retarded as a whole. Therefore, by correcting the operation amount of the variable intake valve timing mechanism from the most retarded side of the IVC range that can be set by the variable intake valve timing mechanism 5 in a state where the timing chain 8 is not extended, to a certain range A3. It is possible to set the IVC to be originally set. However, in the range A4 that is retarded by the extension of the timing chain from the most advanced side of the normal range A3, the variable intake valve timing mechanism 5 alone cannot set the IVC that is originally set. In this embodiment, therefore, only the operation amount of the variable intake valve timing mechanism 5 is corrected in accordance with the extension amount of the timing chain 8 in the range A3 in which the valve timing to be originally set by the intake valve timing mechanism 5 can be set. In the case where the desired IVC, that is, the valve timing is realized, and the amount of expansion of the timing chain 8 and the operating state (required IVC) in which the advance to the IVC to be originally set is impossible, A4 is effective compression. By correcting the target compression ratio to the high compression ratio side by the amount that the ratio has decreased, the reduction in thermal efficiency due to the decrease in the effective compression ratio is compensated by correction to the high compression ratio side.

  The exhaust valve side is basically the same as the intake valve side described above, but since the timing chain stretches in the direction in which the valve overlap expands, the residual gas increases with the timing chain stretch and knocking occurs. The conditions for avoiding the occurrence of this will become severe. Therefore, when the valve timing on the exhaust valve side is corrected as the chain elongation amount increases, the target compression ratio is mainly corrected to the lower side as the timing chain elongation amount increases.

  The characteristic configurations and operational effects of the present invention that can be understood from the above description are listed below.

  [1] The variable compression ratio mechanism 20 that changes the engine compression ratio according to the engine operating state by changing the top dead center position of the piston 12, and the rotational power of the crankshaft 13, the intake / exhaust valves 15, 17 A timing chain 8 is provided between the crank sprocket 13A of the crankshaft 13 and the cam sprockets 16A and 18A of the camshafts 16 and 18 so as to transmit to the camshafts 16 and 18 to be driven. The first invention is a phase difference detecting means for detecting a rotational phase difference between the crankshaft 13 and the camshafts 16 and 18 (rotational speed calculation unit B2, intake valve timing calculation unit B3, exhaust valve timing calculation unit B4, etc. ), Chain extension amount estimation means (timing chain extension amount calculation unit B6) for estimating the extension amount of the timing chain 8 based on the rotational phase difference detected by the phase difference detection means, and extension of the timing chain Compression ratio correction means (target compression ratio calculation unit B7) for correcting the engine compression ratio (target compression ratio tCR) based on the estimated value (dL) of the quantity.

  In this way, by correcting the engine compression ratio (target compression ratio tCR) in accordance with the estimated value (dL) of the amount of expansion of the timing chain, the intake / exhaust valve due to the expansion of the timing chain without causing knocking. While avoiding the interference between the pistons 15 and 17 and the piston 12, it is possible to suppress a decrease in the operating state, and it is possible to continue the operation without necessarily replacing parts or forcibly stopping the engine.

  [2] In the second invention, the upper limit value of the engine compression ratio (target compression ratio tCR) is lowered as the estimated value (dL) of the extension amount of the timing chain 8 increases. For example, in the first embodiment, when the chain extension amount dL shown in FIG. 5B is large, the upper limit value of the target compression ratio is set as compared with the case where the chain extension amount dL shown in FIG. It is lowered from 14 in the region C to 13 in the region C′1.

  In this way, as the estimated value of the amount of elongation of the timing chain increases, the upper limit value of the target compression ratio is reduced, so the compression ratio is maintained while maintaining the distance between the intake and exhaust valves and the piston even when the timing chain is extended. Since only the upper limit value is reduced, it is possible to minimize the performance degradation accompanying the reduction of the compression ratio. Further, if the same timing chain elongation amount is allowed, the valve recess on the piston crown surface can be designed shallow, and the piston area is reduced, so that the thermal efficiency can be improved.

  [3] In the third invention, as the estimated value (dL) of the extension amount of the timing chain 8 increases, the engine compression ratio in a predetermined engine operating state is corrected to the high compression ratio side. For example, in the first embodiment shown in FIG. 5, in the region A on the low rotation high load side, when the chain elongation amount is large (B), compared with the case where the chain elongation is small (A), the target compression ratio ( tCR) is increased from 10 to 11.

  Since the closing timing of the intake valve 15 is retarded by the expansion of the timing chain 8, the effective compression ratio decreases according to the expansion of the timing chain 8. For this reason, if the target compression ratio is set so that knocking does not occur when the timing chain 8 is not extended, the compression ratio is excessively lowered when the timing chain 8 is extended and the effective compression ratio is reduced. Therefore, the thermal efficiency cannot be sufficiently improved. According to the third aspect of the invention, as the estimated value (dL) of the extension amount of the timing chain 8 increases, at least a part of the operating state of the engine, specifically, the knocking condition is originally severe, so that the target compression ratio is increased. By correcting the target compression ratio (tCR) to the high compression ratio side in the region A on the low rotation high load side that is suppressed to a low level, it is possible to suppress a decrease in thermal efficiency without causing knocking. .

  [4] In the fourth invention, as the estimated value (dL) of the extension amount of the timing chain 8 increases, the engine compression ratio in a predetermined engine operating state is corrected to the low compression ratio side. For example, in the first embodiment shown in FIG. 5, in the region C on the low load side and the high rotation side, the target compression is larger when the chain elongation amount is large (B) than when the chain elongation is small (A). The ratio (tCR) is reduced from 14 to 13 or 12.

  Since the closing timing of the exhaust valve 17 is retarded by the extension of the timing chain 8, the valve overlap is expanded and the residual gas is increased. When the residual gas increases, the working gas temperature at the start of compression rises, so that knocking is likely to occur. According to the fourth aspect of the invention, as the estimated value (dL) of the extension amount of the timing chain 8 increases, the target compression ratio (tCR) is corrected to be low in at least a part of the operating state of the engine. Knocking due to an increase in the amount can be suppressed. In particular, in an operating state in which the pressure in the exhaust pipe is higher than the pressure in the collector, the residual gas increases due to the back flow during valve overlap. The high rotation region C is a driving state where the effects of the present invention are easily obtained.

  [5] The fifth invention has variable valve timing means such as variable valve timing mechanisms 5 and 6 for changing the valve timing of the intake / exhaust valves according to the engine operating state, and estimates the extension amount of the timing chain 8 Based on the value (dL), both the engine compression ratio (tCR) and the valve timing (rVTI, rVTE) are corrected.

  In the case of having a variable valve timing means, even if the timing chain 8 is extended and the valve timing is retarded, if it is within the variable range of the valve timing, the desired valve timing should be set only by correcting the valve timing. Can do. However, as shown in FIG. 10, as the timing chain 8 extends, the variable range of the valve timing itself shifts to the retarded side as a whole (A1 → A2). The variable range of the same valve timing cannot be taken. According to the fifth aspect of the invention, the target compression ratio (tCR) and the valve timing (rVTI, rVTE) are corrected / changed according to the estimated value (tCR) of the extension amount of the timing chain 8, so that the timing chain 8 is extended. Therefore, even if the variable range of valve timing has changed, by setting both the target compression ratio and valve timing accordingly, it is possible to suppress a decrease in operating performance due to the expansion of the timing chain. Can do.

  [6] Specifically, as in the sixth aspect of the invention, when the valve timing is retarded due to the expansion of the timing chain 8, the timing chain that can correct the delay amount of the valve timing by the variable valve timing mechanisms 5 and 6 8, in the range A3 in FIG. 10, only the valve timing correction is performed by the variable valve timing mechanisms 5 and 6 in accordance with the extension amount of the timing chain 8. On the other hand, the combination of the amount of extension of the timing chain 8 and the operating state in which the variable valve timing mechanisms 5 and 6 cannot compensate for the delay of the valve timing, specifically, as shown in FIG. In the range A4 corresponding to the amount of delay corresponding to the amount of extension of the timing chain 8 from the valve timing of the most advanced angle when the valve is not extended, both the valve timing and the engine compression ratio are determined according to the amount of extension of the timing chain 8. Correct. As a result, even if the amount of expansion of the timing chain 8 increases and the operation state cannot be converted into the intended valve timing only by correcting the valve timing, the valve timing can be increased by using the correction of the target compression ratio together. The reduction in thermal efficiency due to the retarded angle can be compensated by correction to the high compression ratio side, and a wider range of engine operation is possible than when the amount of extension of the timing chain is corrected using only the variable valve timing mechanisms 5 and 6. In the state, it is possible to suppress the performance degradation accompanying the elongation of the timing chain.

Claims (6)

Variable compression ratio means for changing the engine compression ratio according to the engine operating state by changing the top dead center position of the piston;
A timing chain spanned between the crank sprocket of the crankshaft and the cam sprocket of the camshaft so as to transmit the rotational power of the crankshaft to the camshaft that drives the intake and exhaust valves;
In a control device for a variable compression ratio internal combustion engine having
Phase difference detecting means for detecting a rotational phase difference between the crankshaft and the camshaft;
Based on the rotational phase difference detected by the phase difference detection means, chain extension amount estimation means for estimating the extension amount of the timing chain;
Compression ratio correction means for correcting the engine compression ratio based on the estimated value of the elongation amount of the timing chain;
A control apparatus for a variable compression ratio type internal combustion engine, comprising:   2. The control apparatus for a variable compression ratio internal combustion engine according to claim 1, wherein the compression ratio correction means lowers the upper limit value of the engine compression ratio as the estimated value of the extension amount of the timing chain increases. .   The compression ratio correction means corrects the engine compression ratio in a predetermined engine operating state to a high compression ratio side as the estimated value of the extension amount of the timing chain increases. A variable compression ratio internal combustion engine control apparatus.   The compression ratio correction means corrects the engine compression ratio in a predetermined engine operating state to a low compression ratio side as the estimated value of the extension amount of the timing chain increases. A control apparatus for a variable compression ratio internal combustion engine according to claim 1. Variable valve timing means for changing the valve timing of the intake and exhaust valves according to the engine operating state;
The variable compression according to any one of claims 1 to 4, wherein the compression ratio correcting means corrects both the engine compression ratio and the valve timing based on an estimated value of the extension amount of the timing chain. A control device for a specific internal combustion engine. When the valve timing is retarded due to the extension of the timing chain,
In the combination of the amount of extension of the timing chain and the operating state that can correct the delay amount of the valve timing by the variable valve timing means, only the valve timing is corrected by the variable valve timing means according to the amount of extension of the timing chain. ,
In the combination of the timing chain extension amount and the operating state in which the variable valve timing means cannot compensate for the delay amount of the valve timing, both the valve timing and the engine compression ratio are determined according to the extension amount of the timing chain. The control apparatus for a variable compression ratio internal combustion engine according to claim 5, wherein:

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