JP2012007515A - Control device of internal combustion engine including variable compression ratio mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give a feeling of sufficiently deceleration when an engine decelerates during a high temperature of a catalyst device, even if fuel cut is inhibited and the combustion with less consumed fuel is performed, in a control device of an internal combustion engine including a variable compression ratio mechanism that varies a mechanical compression ratio.SOLUTION: When a temperature of the catalyst device is equal to or higher than a first setting temperature during deceleration of the engine (step 104), the fuel cut is inhibited to control a sintering of a catalyst; and the mechanical compression ratio is increased by the variable compression ratio mechanism (E1), a valve closing timing of an intake valve is retarded (IVC1), a valve opening timing of an exhaust valve is retarded (EVO1), in comparison with during an idle operation, and thereby the consumption is performed (step 106).

Description

  The present invention relates to a control device for an internal combustion engine including a variable compression ratio mechanism that makes a mechanical compression ratio variable.

  The mechanical compression ratio ((top dead center cylinder volume + stroke volume) / top dead center cylinder volume) is variable by changing the distance between the cylinder block and the crankshaft by relatively moving the cylinder block and the crankcase. An internal combustion engine including a variable compression ratio mechanism has been proposed (see Patent Document 1).

  By the way, the catalyst device arranged in the engine exhaust system generally carries a noble metal catalyst. However, when this noble metal catalyst is at a high temperature, if a large amount of oxygen is present, it deteriorates due to sintering. As a result, when the catalyst device is hot, fuel cut is prohibited and combustion is performed even when the engine is decelerated.

  It is desirable to reduce fuel consumption as much as possible during such engine deceleration. Thus, for example, if the mechanical compression ratio is increased by a variable compression ratio mechanism, an actual compression ratio that can be combusted even if the intake valve closing timing is retarded to reduce the intake amount can be realized. Can be reduced.

JP 2009-250163 A JP-A-2005-147105

  As described above, combustion with less fuel consumption can be carried out by increasing the mechanical compression ratio during engine deceleration when the catalyst device is hot. However, if the intake air amount is reduced in this way, the engine braking force becomes smaller, and thus a sufficient feeling of deceleration may not be obtained.

  Accordingly, an object of the present invention is a control device for an internal combustion engine provided with a compression ratio variable mechanism that makes a mechanical compression ratio variable, and fuel cut is prohibited during engine deceleration when the catalyst device is at a high temperature. It is to be able to obtain a sufficient feeling of deceleration even if combustion with a small amount of is performed.

  According to a first aspect of the present invention, there is provided a control device for an internal combustion engine having a variable compression ratio mechanism, wherein when the temperature of the catalyst device is equal to or higher than a first set temperature during engine deceleration, the fuel is suppressed in order to suppress catalyst sintering. In addition to prohibiting cutting, the mechanical compression ratio is increased by a variable compression ratio mechanism compared to during idle operation, the intake valve closing timing is retarded, and the exhaust valve opening timing is retarded for combustion It is characterized by doing.

  According to a second aspect of the present invention, there is provided a control device for an internal combustion engine comprising the variable compression ratio mechanism according to the first aspect. Therefore, only when the required deceleration torque is greater than or equal to the set deceleration torque, the mechanical compression ratio is increased by the variable compression ratio mechanism, the intake valve closing timing is retarded, and the exhaust valve It is characterized in that combustion is carried out by retarding the valve opening timing.

  According to a third aspect of the present invention, there is provided a control device for an internal combustion engine comprising the variable compression ratio mechanism according to the second aspect, wherein the temperature of the catalyst device is equal to or higher than a first set temperature during engine deceleration. If the required deceleration torque is less than the set deceleration torque, the same mechanical compression ratio as during idle operation is used, the same intake valve closing timing as during idle operation, and the same exhaust valve opening timing as during idle operation. Combustion is performed.

  A control apparatus for an internal combustion engine having a variable compression ratio mechanism according to a fourth aspect of the present invention is the control apparatus for an internal combustion engine having a variable compression ratio mechanism according to any one of the first to third aspects. At that time, when the temperature of the catalyst device is equal to or lower than the second set temperature, the fuel cut is prohibited in order to raise the temperature of the catalyst device, and the mechanical compression ratio is increased by the compression ratio variable mechanism as compared with the idling operation, Combustion is performed by advancing the valve opening timing of the exhaust valve.

  The control apparatus for an internal combustion engine having the compression ratio variable mechanism according to claim 5 according to the present invention is the control apparatus for an internal combustion engine having the compression ratio variable mechanism according to claim 4, wherein the deceleration request torque is large when the deceleration request torque is large. Is characterized in that the opening timing of the intake valve is retarded as compared to when the value is small.

  A control device for an internal combustion engine having a variable compression ratio mechanism according to a sixth aspect of the present invention is the control device for an internal combustion engine having a variable compression ratio mechanism according to any one of the first to third aspects. When the temperature of the catalyst device is lower than the first set temperature and higher than the second set temperature at the time, in order to suppress the temperature drop of the catalyst device, the compression ratio is compared with the idle operation when performing the fuel cut. The mechanical compression ratio is increased by a variable mechanism, and the closing timing of the intake valve is retarded.

  According to the control apparatus for an internal combustion engine having the compression ratio variable mechanism according to the first aspect of the present invention, when the temperature of the catalyst device is equal to or higher than the first set temperature during engine deceleration, the sintering of the catalyst is suppressed. In addition to prohibiting fuel cut, the compression ratio variable mechanism increases the mechanical compression ratio and retards the closing timing of the intake valve compared to during idle operation, thereby reducing the amount of intake air and enabling combustible actual compression. Ratio can be realized, and combustion with less fuel consumption becomes possible. However, since the engine braking force is reduced in this state, the exhaust valve opening timing is retarded as compared with the idling operation, the overexpansion is intentionally caused, and the deceleration torque is generated. Make sense. In addition, the delay of the opening timing of the exhaust valve lowers the exhaust gas temperature, which is advantageous for lowering the temperature of the catalyst device.

  According to the control apparatus for an internal combustion engine comprising the compression ratio variable mechanism according to claim 2 of the present invention, in the control apparatus for the internal combustion engine according to claim 1, the temperature of the catalyst device during the engine deceleration is the first set temperature. As described above, only when the required deceleration torque is equal to or greater than the set deceleration torque, the mechanical compression ratio is increased by the compression ratio variable mechanism and the closing timing of the intake valve is retarded as compared with the idling operation. The actual compression ratio that can be combusted with a small amount of intake air can be realized, and combustion with less fuel consumption can be realized. On the other hand, if this is the case, the engine braking force will be reduced and the required deceleration torque above the set deceleration torque Therefore, the exhaust valve opening timing is retarded compared to that during idle operation, causing excessive expansion and generating deceleration torque. Do deceleration feeling to be obtained.

  According to the control device for an internal combustion engine comprising the compression ratio variable mechanism according to claim 3 according to the present invention, in the control device for the internal combustion engine according to claim 2, the temperature of the catalyst device during the engine deceleration is the first set temperature. Even when the required deceleration torque is less than the set deceleration torque, the same mechanical compression ratio as during idle operation is set, the intake valve closing timing is the same as during idle operation, and the exhaust valve is opened as during idle operation. Combustion is performed as time, thereby making it unnecessary to change the mechanical compression ratio and reducing the opportunity for operating the variable compression ratio mechanism.

  According to the control apparatus for an internal combustion engine provided with the variable compression ratio mechanism according to claim 4 of the present invention, the control apparatus for the internal combustion engine provided with the compression ratio variable mechanism according to any one of claims 1 to 3. When the engine is decelerated, when the temperature of the catalyst device is equal to or lower than the second set temperature, fuel cut is prohibited in order to raise the temperature of the catalyst device, and the mechanical compression ratio is changed by the compression ratio variable mechanism as compared with the idling operation. The combustion is carried out by increasing the valve opening time and advancing the opening timing of the exhaust valve. As a result, the combustion speed is increased by increasing the mechanical compression ratio, and even if the opening timing of the exhaust valve is advanced, almost no unburned fuel is discharged, and the advancement timing of the exhaust valve opens. Since the exhaust gas temperature can be increased, it is advantageous for raising the temperature of the catalyst device.

  According to the control apparatus for an internal combustion engine having the compression ratio variable mechanism according to the fifth aspect of the present invention, in the control apparatus for the internal combustion engine having the compression ratio variable mechanism according to the fourth aspect, the deceleration is performed when the deceleration request torque is large. The opening timing of the intake valve is delayed more than when the required torque is small, thereby increasing the difference between the actual expansion ratio and the actual compression ratio and increasing the deceleration torque generated by overexpansion. Can do.

  According to the control device for an internal combustion engine provided with the variable compression ratio mechanism according to claim 6 of the present invention, the control device for the internal combustion engine provided with the compression ratio variable mechanism according to any one of claims 1 to 3. When the engine is decelerating, when the temperature of the catalyst device is lower than the first set temperature and higher than the second set temperature, in order to suppress the temperature drop of the catalyst device, when performing fuel cut, compared to during idle operation The mechanical compression ratio is increased by the compression ratio variable mechanism to increase the compression work so that a sufficient feeling of deceleration can be obtained, and the intake valve is discharged from the cylinder by retarding the closing timing. The amount of air can be reduced, which is advantageous for suppressing the temperature drop of the catalyst device.

It is a figure for demonstrating the compression ratio variable mechanism of an internal combustion engine. It is a flowchart which shows control of the internal combustion engine by the control apparatus of this invention.

  FIG. 1 is a diagram for explaining a compression ratio variable mechanism that moves a cylinder block relative to a crankcase in order to make the compression ratio of an internal combustion engine variable. In the figure, 10 is a cylinder block, 20 is a crankcase, and 30 is a piston at a compression top dead center position. The internal combustion engine is an in-line cylinder arrangement type.

  In the front view shown in FIG. 1, the first support 11 is provided on one side of the lower part of the cylinder block 10, the second support 12 is provided on the other side of the lower part of the cylinder block 10, and the upper part of the crankcase 20 is A third support 21 is provided on one side, and a fourth support 22 is provided on the other side of the upper part of the crankcase 20. In the lowest position of the cylinder block 10 shown in FIG. 1A, concentric first holes and third holes are formed in the first support 11 and the third support 21, and the second support 12 and the fourth support 22 are formed in the second support 12 and the fourth support 22. Are formed with concentric second and fourth holes. The first hole, the second hole, the third hole, and the fourth hole have the same diameter, and the first hole and the second hole are symmetrical with respect to a vertical plane passing through the center of each cylinder, and the third hole And the fourth hole is symmetrical.

  A first boss 13, a second boss 14, a third boss, and a fourth boss are disposed in the first hole, the second hole, the third hole, and the fourth hole, respectively, so as to be rotatable. The first boss 13, the second boss 14, the third boss, and the fourth boss are formed with eccentric holes having the same diameter at the same position, and the eccentric hole of the first boss 13 and the eccentric hole of the third boss are rotated. The first shaft 15 is inserted as possible, and the second shaft 16 is rotatably inserted into the eccentric hole of the second boss 14 and the eccentric hole of the fourth boss.

  With the variable compression ratio mechanism configured as described above, at the lowest position (A) of the cylinder block 10, the first boss 13 (counterclockwise) and the second boss 14 (clockwise) are rotated 90 degrees in opposite directions. When moved, the cylinder block 10 moves up to the intermediate position (B) with respect to the crankcase 20. As a result, the top dead center cylinder volume is increased and the mechanical compression ratio ((top dead center cylinder volume + stroke volume) / top dead center cylinder volume) is reduced as compared with the lowest position (A) of the cylinder block 10. be able to.

  Further, when the first boss 13 is rotated 90 degrees counterclockwise in FIG. 1 at the intermediate position (B) of the cylinder block 10, the second boss 14 is rotated 90 degrees clockwise in FIG. The cylinder block 10 moves up to the uppermost position (C) with respect to the crankcase 20. As a result, the top dead center cylinder volume is further increased, and the mechanical compression ratio ((top dead center cylinder volume + stroke volume) / top dead center cylinder volume) is reduced as compared with the intermediate position (B) of the cylinder block 100. be able to. Thus, the desired mechanical compression ratio can be realized by rotating the first boss 13 and the second boss 14 by an arbitrary angle in opposite directions.

  If the mechanical compression ratio is increased, the actual expansion ratio ((top dead center cylinder volume + stroke volume until exhaust valve opening) / top dead center cylinder volume) can be increased to increase thermal efficiency. In addition to such a variable compression ratio mechanism, if a variable valve timing mechanism that can change the closing timing of the intake valve and the opening timing of the exhaust valve is provided, the actual expansion for each mechanical compression ratio is provided. The ratio can be optimally controlled, and the actual compression ratio ((top dead center cylinder volume + stroke volume since intake valve closing) / top dead center cylinder volume) can also be optimally controlled. The variable valve timing mechanism may change the phase angle between the intake valve camshaft (or exhaust valve camshaft) and the intake valve cam (or exhaust valve cam), for example. As the variable valve timing mechanism, when the intake valve (or exhaust valve) is opened and closed by a hydraulic or electromagnetic actuator, the intake valve (or exhaust valve) can be opened and closed at any time, and the actuator itself Is a variable valve timing mechanism.

Generally, a catalyst device for purifying exhaust gas is disposed in an exhaust system of an internal combustion engine. The catalytic device is a three-way catalyst device, an oxidation catalyst device (including a particulate filter added with an oxidation function), an occlusion reduction NO _x catalyst device, etc. depending on the internal combustion engine. A noble metal catalyst (for example, Pt) is supported. When the noble metal catalyst is at a high temperature (for example, 900 ° C. or more) and a large amount of oxygen is present, the noble metal particles adhere to each other and become large particles, resulting in sintering and deterioration of the surface area.

  Thus, generally, in order to suppress sintering, fuel cut during engine deceleration is prohibited when the catalyst device is at a high temperature. However, if normal idle operation is performed when the engine decelerates, fuel consumption will deteriorate. Therefore, it is preferable to perform combustion with less fuel consumption, but simply to perform combustion with less fuel consumption. The engine braking force will decrease and a sufficient deceleration will not be obtained.

  The control device of the present embodiment controls the mechanical compression ratio, the intake valve closing timing, and the exhaust valve opening timing in an internal combustion engine that includes a variable valve timing mechanism in addition to the compression ratio variable mechanism as described above. When the engine is decelerating at a high temperature, even if the fuel cut is prohibited and combustion with less fuel consumption is performed in order to suppress sintering, a sufficient feeling of deceleration can be obtained.

  The control device of the present embodiment controls the internal combustion engine according to the flowchart shown in FIG. First, in step 101, it is determined whether or not the accelerator pedal depression amount L is zero. When the accelerator pedal is depressed, the determination at step 101 is negative, and since the engine is not decelerating, the process ends as it is. When the accelerator pedal is not depressed, that is, when the accelerator pedal is released, the determination at step 101 is affirmed and the routine proceeds to step 102.

  In step 102, it is determined whether or not the engine speed N is equal to or higher than a set speed N '(for example, 1500 rpm). When this determination is negative, it is during idling, and in step 103, the mechanical compression ratio E is set to E0 suitable for idling by the variable compression ratio mechanism, and the intake valve closing timing IVC is set by the variable valve timing mechanism. The exhaust valve opening timing EVO is set to EVO0 before the normal expansion bottom dead center suitable for idle operation, and is set to IVC0 after the normal intake bottom dead center suitable for idle operation.

  On the other hand, when the determination in step 102 is affirmative, it is during engine deceleration when the accelerator pedal is released and the engine speed is high, and in step 104 the temperature T of the catalyst device (may be measured or estimated). Is determined to be equal to or higher than a first set temperature T1 (eg, 900 ° C.). When this determination is affirmed, if fuel cut is performed to save fuel, a large amount of oxygen is supplied to the high-temperature catalyst device, which causes deterioration of the catalyst due to sintering. As a result, fuel cut cannot be performed. Next, at step 105, it is determined whether or not the required deceleration torque RT is equal to or greater than the set deceleration torque RT '. For example, when the vehicle speed is high, the required deceleration torque RT is relatively large, and the determination in step 105 is affirmed.

  If the determination in step 105 is affirmative, in step 106, the mechanical compression ratio E is set to E1 larger than E0 during idling by the variable compression ratio mechanism, and the intake valve closing timing IVC is set to idling by the variable valve timing mechanism. The exhaust valve opening timing EVO is set to EVO1 in the vicinity of the expansion bottom dead center or after the expansion bottom dead center on the delay angle side from EVO0 during idling operation.

  Thereby, when fuel cut is prohibited to suppress the sintering of the catalyst, the intake air amount is reduced by the intake valve closing timing IVC1 retarded as compared with the idling operation, and a desired air-fuel ratio (for example, theoretically) The amount of fuel required to achieve an air-fuel ratio or lean air-fuel ratio) can be reduced, and an actual compression ratio that can be combusted even with a small amount of intake air by a mechanical compression ratio E1 that is increased as compared to during idle operation. Can be realized, thereby enabling combustion with less fuel consumption. However, since the engine braking force is reduced as it is, over-expansion is intentionally caused by the exhaust valve opening timing EVO1 retarded compared with the idling operation, and a large deceleration torque is generated to sufficiently reduce the deceleration. A feeling can be obtained. Further, since the exhaust gas temperature is also lowered by the retarded exhaust valve opening timing EVO1, the temperature of the catalyst device can be satisfactorily lowered.

  On the other hand, when the determination in step 105 is negative, that is, when the vehicle speed is not so high and the requested deceleration torque RT is less than the set deceleration torque RT ′, the process proceeds to step 106 as in the case where the set deceleration torque RT ′ or more. In step 107, the mechanical compression ratio E is set to E0 during idle operation by the variable compression ratio mechanism, and the intake valve closing timing IVC is set to IVC0 during idle operation by the variable valve timing mechanism. At the same time, the exhaust valve opening timing EVO is set to EVO1 in the vicinity of the expansion bottom dead center or after the expansion bottom dead center on the retard side with respect to EVO0 during idle operation.

  In the control in step 106, the actual expansion ratio is made very large compared to the actual compression ratio, thereby generating a large deceleration torque. However, in step 107, since a large deceleration torque is not necessary, Compared with the control of 106, the difference between the actual compression ratio and the actual expansion ratio is reduced, and the deceleration torque generated by overexpansion is reduced. Thus, it is not necessary to change the mechanical compression ratio by the variable compression ratio mechanism.

  On the other hand, at the time of engine deceleration, if the temperature T of the catalyst device is lower than the first set temperature T1, the determination in step 104 is negative, and in step 108, the temperature T of the catalyst device is set to the second set temperature T2 (activation of the catalyst). It is determined whether the temperature is sufficiently higher than the temperature, for example, 400 ° C. or less. When this determination is affirmed, if the fuel cut is performed, the temperature of the catalyst device may be lower than the activation temperature of the catalyst, so the fuel cut is prohibited and combustion is performed.

  In step 109, the mechanical compression ratio E is set to E1 that is larger than E0 during idling by the variable compression ratio mechanism, and the intake valve closing timing IVC is retarded by the variable valve timing mechanism as the required deceleration torque RT increases, and the intake air is increased. The exhaust valve opening timing EVO is set to an advance side from EVO0 during idling operation.

  Thus, the combustion speed can be increased by increasing the mechanical compression ratio, and even if the exhaust valve opening timing EVO is advanced, almost no unburned fuel is discharged, and the exhaust valve opening timing advances. Since the exhaust gas temperature can be increased by the angle, the temperature decrease of the catalyst device can be suppressed, or the temperature of the catalyst device can be raised satisfactorily.

  The intake valve closing timing IVC is controlled so as to be retarded as the required deceleration torque RT increases, and the difference between the actual expansion ratio and the actual compression ratio becomes large, so that it occurs due to overexpansion. The deceleration torque to be increased can be increased. Further, the exhaust valve opening timing EVO is preferably advanced to the point immediately after most of the fuel is combusted to increase the temperature of the exhaust gas. Accordingly, an in-cylinder pressure sensor may be arranged to detect when most of the fuel has been combusted based on the measured in-cylinder pressure.

  If the determination in step 108 is negative and the temperature T of the catalyst device is lower than the first set temperature T1 and higher than the second set temperature T2 during engine deceleration, fuel cut is performed to save fuel. At this time, in step 110, the mechanical compression ratio E is set to E1 larger than E0 during idling by the variable compression ratio mechanism, and the intake valve closing timing IVC is retarded from IVC0 during idling by the variable valve timing mechanism. The exhaust valve opening timing EVO is controlled based on the required deceleration torque RT.

  Thus, the compression work is increased by increasing the mechanical compression ratio. In addition, the delay of the intake valve closing timing makes it possible to reduce the amount of air that is sucked into the cylinder and discharged, which is advantageous in suppressing the temperature drop of the catalyst device.

  If the exhaust valve opening timing EVO is immediately after the compression top dead center, most of the compression work can be made the deceleration torque, and if the actual compression ratio and the actual expansion ratio are made equal, the compression work Most of this is recovered by the piston, and the deceleration torque can be made almost zero. Further, if it is time to make the actual expansion ratio larger than the actual compression ratio, deceleration torque can be generated by overexpansion.

  In this flowchart, the mechanical compression ratio E1 of steps 106, 109, and 110 does not need to be particularly equal, and may be larger than the mechanical compression ratio E0 during idle operation. Further, the intake valve closing timing IVC1 in steps 106 and 110 is not particularly required to be equal to each other, and may be retarded from the intake valve closing timing IVC0 during idle operation. Further, the exhaust valve opening timing EVO1 in steps 106 and 107 does not need to be particularly equal, and may be set to the retard side from the exhaust valve opening timing EVO0 during idle operation.

10 Cylinder block 20 Crankcase 30 Piston

Claims (6)

  When the temperature of the catalyst device is equal to or higher than the first set temperature during engine deceleration, fuel cut is prohibited in order to suppress catalyst sintering, and the mechanical compression ratio is set by the compression ratio variable mechanism as compared to during idle operation. A control apparatus for an internal combustion engine, comprising a compression ratio variable mechanism, characterized in that combustion is performed by increasing the valve timing, retarding the closing timing of the intake valve, and retarding the opening timing of the exhaust valve.   Only when the temperature of the catalyst device during engine deceleration is equal to or higher than the first set temperature and the required deceleration torque is equal to or higher than the set deceleration torque, the mechanical compression ratio is increased by the variable compression ratio mechanism as compared to during idle operation. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion is carried out by retarding the closing timing of the intake valve and retarding the opening timing of the exhaust valve.   If the required deceleration torque is less than the preset deceleration torque even when the temperature of the catalyst device is equal to or higher than the first preset temperature during engine deceleration, the same mechanical compression ratio as during idle operation is used and the intake valve is closed as during idle operation. The control apparatus for an internal combustion engine according to claim 2, wherein the combustion is performed at the same timing as the exhaust valve opening timing at the time of idle operation.   When the temperature of the catalyst device is lower than the second set temperature during engine deceleration, fuel cut is prohibited in order to raise the temperature of the catalyst device, and the mechanical compression ratio is increased by the variable compression ratio mechanism as compared with the idling operation. 4. A control apparatus for an internal combustion engine comprising a compression ratio variable mechanism according to any one of claims 1 to 3, wherein combustion is carried out by advancing the valve opening timing of the exhaust valve.   5. The control apparatus for an internal combustion engine comprising the variable compression ratio mechanism according to claim 4, wherein when the deceleration request torque is large, the valve opening timing of the intake valve is retarded compared to when the deceleration request torque is small.   When the engine is decelerated, when the temperature of the catalyst device is lower than the first set temperature and higher than the second set temperature, in order to suppress the temperature drop of the catalyst device, when performing fuel cut, compared to during idle operation, The control of the internal combustion engine having the variable compression ratio mechanism according to any one of claims 1 to 3, wherein the mechanical compression ratio is increased by a variable compression ratio mechanism and the closing timing of the intake valve is retarded. apparatus.

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