JP4841382B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to control of the intake air amount of an engine, and more particularly to control for maintaining the rotational speed during idle operation.

  A variable valve mechanism is known as a means for realizing valve timing suitable for each operation region.

  By controlling this variable valve mechanism so that the valve overlap period is almost zero during low-load operation, such as during idle operation, and the valve overlap period is provided during high-load operation, such as during acceleration. Various requirements such as low fuel consumption, low emission, and high output can be satisfied in the region.

  In an engine having such a variable valve mechanism, the valve timing may deviate from a target value suitable for the operating state of the engine. For example, when the valve timing for high load operation is reached during low load operation due to a malfunction of the variable valve mechanism or the like, engine stall may occur.

Japanese Patent Application Laid-Open No. H10-228561 discloses control for correcting the air amount according to the valve overlap amount as means for preventing engine stall due to mismatch between the engine operating state and the valve timing as described above.
Japanese Patent Laid-Open No. 10-61465

  By the way, as a case where the valve timing deviates from a target value suitable for the operating state of the engine, it may be considered that operation diagnosis, control value learning, etc. of a variable valve mechanism or a throttle valve are performed. For example, when performing an operation diagnosis of the variable valve mechanism, the variable valve mechanism is set to the most retarded state in a no-load operation state such as idle operation. At this time, if the intake valve opening timing at the most retarded position is significantly retarded from the piston top dead center position, the generated torque of the engine is reduced due to a decrease in the actual compression ratio while the intake amount remains constant, Engine stall is likely to occur.

  Therefore, air amount correction is required to increase the generated torque, but the valve overlap amount is usually zero when the intake valve opening timing at the most retarded position is significantly retarded from the top dead center. It is as follows. Therefore, in the control for determining the correction amount according to the valve overlap amount as disclosed in Patent Document 1, it is not possible to perform an appropriate air amount correction.

  Therefore, an object of the present invention is to prevent the occurrence of an engine stall accompanying a decrease in the actual compression ratio even when there is no valve overlap.

An internal combustion engine of the present invention includes an intake valve that opens and closes in synchronization with the rotational speed of the internal combustion engine, a variable valve mechanism that can variably control the opening and closing timing of the intake valve, and control of the intake air amount of the internal combustion engine. An intake air amount control means for performing the intake air amount control means according to the closing timing of the intake valve only when the internal combustion engine is idling and the valve overlap period is zero or negative. Then, idle air amount control for controlling the intake air amount is performed.

  According to the present invention, since the intake air amount during idle operation is controlled according to the closing timing of the intake valve, for example, the variable valve mechanism is operated during idle operation, and the thermal efficiency increases with the change in the actual compression ratio. Even in the case of a change, it is possible to prevent the idle speed from rising or falling.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a system to which the first embodiment is applied. 1 is an engine, 2 is an intake passage, 3 is an exhaust passage, 4 is an intake valve, 5 is an exhaust valve, 6 is an intake camshaft that drives the intake valve 4, and 16 is a variable motion that can change the opening and closing timing of the intake valve 4 A valve mechanism, 19 is an intake side cam angle sensor (intake valve operation timing detection means) that detects the rotation angle of the intake camshaft 6, 7 is an exhaust camshaft that drives the exhaust valve 5, and 20 is a rotation angle of the exhaust camshaft 7. The exhaust cam angle sensor 9 detects a piston, 9 is a piston that slides in the cylinder of the engine 1, 10 is a crankshaft connected to the piston 9 via a connecting rod 27, and 21 is a rotation angle of the crankshaft 10. A crank angle sensor 11 is a combustion chamber defined by a cylinder wall surface and a crown surface of the piston 9, and 8 is an ignition plug disposed so as to face the combustion chamber 11.

  Reference numeral 17 denotes a fuel injection valve that injects fuel into the intake passage 12, reference numeral 12 denotes a collector part that distributes intake air to each cylinder, and reference numeral 13 denotes a throttle valve that adjusts the intake air amount on the upstream side of the collector part 12 ( (Intake air amount control means), 24 is a throttle position sensor for detecting the opening of the throttle valve 13, and 14 is an air flow meter for detecting the amount of intake air. The throttle valve 13 is a so-called electronically controlled throttle, and is controlled to an opening degree according to the operating state by a control unit 15 described later. Reference numerals 25 and 26 denote NOx catalysts which are disposed in the exhaust passage 3 to purify the exhaust, and three-way catalysts. Reference numeral 22 denotes an air-fuel ratio sensor which detects the air-fuel ratio of the exhaust flowing into the NOx catalyst 25. Reference numeral 23 denotes an accelerator opening sensor that detects a driver's accelerator pedal depression amount, and reference numeral 18 denotes a water temperature sensor that detects the temperature of cooling water circulating in the engine 1.

  An engine control unit (ECU) 15 determines the opening degree of the throttle valve 13, the fuel injection amount, the fuel injection timing, the ignition timing, the opening / closing timing of the intake valve 4, and the like based on the detection values of the sensors. The valve overlap period is calculated as valve overlap calculation means.

  The intake passage 2 has an opening on the ceiling surface of the combustion chamber 11, and an intake valve 4 is provided to open and close the opening. Similarly, the exhaust passage 3 has an opening on the ceiling surface of the combustion chamber 11, and an exhaust valve 5 is provided to open and close the opening.

  The intake camshaft 6, the exhaust camshaft 7 and the crankshaft 10 are wound with a timing chain (not shown), and the intake valve 4 and the exhaust valve 5 open and close in synchronization with the vertical movement of the piston 9.

  The variable valve mechanism 16 variably controls the opening / closing timing of the intake valve 4 by shifting the phases of the crankshaft 10 and the intake camshaft 6 toward the advance side or the retard side. Since this mechanism is already a well-known technique (for example, 2004-225600), description thereof is omitted. The phase difference between the crankshaft 10 and the intake camshaft 6 is obtained from the detection values of the crank angle sensor 21 and the intake side cam angle sensor 19.

  FIGS. 2A to 2C are valve timing diagrams showing examples of valve timings that can be realized by the variable valve mechanism 16, and FIG. 2A is the most retarded opening / closing timing of the intake valve 4 (valve overlap is In the case of (negative), (b) represents a case where the valve overlap is zero, and (c) represents a case where the opening / closing timing of the intake valve 4 is advanced until the valve overlap becomes positive.

  When the opening / closing timing of the intake valve 4 is the most retarded, as shown in FIG. 2A, the closing timing of the intake valve 4 is 90 degrees after bottom dead center, which is a so-called delayed closing valve timing. The opening timing of the intake valve 4 is after a predetermined period from the closing timing of the exhaust valve 5, and a period during which both the intake valve 4 and the exhaust valve 5 are closed (minus valve overlap period) occurs. Thus, when the intake valve 4 is closed late, the actual compression ratio is reduced and the output is reduced, but the pumping loss is reduced, so that the fuel efficiency is improved.

  When the valve overlap is zero, as shown in FIG. 2B, the closing timing of the intake valve 4 is about 60 degrees after bottom dead center, and the opening timing of the intake valve 4 and the closing timing of the exhaust valve 5 are All are just after passing through top dead center. When the valve overlap is positive, the intake valve 4 is opened before top dead center, as shown in FIG. When the valve overlap is made positive, the intake air in the intake valve passage 2 is drawn into the cylinder by the gas flow generated by the combustion gas in the cylinder flowing into the exhaust passage 3. Therefore, when the gas flow becomes strong, such as during high rotation, more intake air is filled in the cylinder, and the output is improved.

  The control unit 15 sets the control target value of the valve timing according to the operation state such as the engine speed and load, and other requests such as operation diagnosis of the variable valve mechanism 16 and the throttle valve 13 and control value learning. The variable valve mechanism 16 is controlled.

  In the present embodiment, for example, the valve overlap is zero as shown in FIG. 2B during idle operation, and the valve overlap is positive as shown in FIG. 2C during high load and high rotation. During low load operation, control is performed so that the valve overlap is negative as shown in FIG.

  By the way, in order to perform operation diagnosis, control value learning, and the like of the variable valve mechanism 16 and the throttle valve 13, the variable valve mechanism 16 may be driven during idle operation. When the variable valve mechanism 16 is driven to change the valve timing, the generated torque changes due to the change in thermal efficiency. For example, at the most retarded position, the closing timing of the intake valve 4 is 90 degrees after bottom dead center, so that the normal retarded operation (FIG. 2B) where the valve overlap is zero (FIG. 2B) is the most retarded position (FIG. If it is changed to 2 (c), the actual compression ratio is lowered, and accordingly, the generated torque is also lowered due to the decrease in thermal efficiency. In particular, when the valve overlap is zero or negative, the influence of the change in the closing timing of the intake valve 4 on the fluctuation of the generated torque is large. When the valve overlap is positive, the influence of the amount of internal recirculation of exhaust becomes large.

  Therefore, when the valve overlap is zero or negative, the following control (idle air amount control) is executed in order to maintain the idling speed. FIG. 3 is a flowchart showing a control routine of idle air amount control.

  In step S1, a base idle air amount ISC0, which is an intake air amount necessary to maintain the idle speed, is calculated based on the water temperature, the engine speed, and the like. Note that the base idle air amount ISC0 is an intake air amount necessary to maintain the idling speed while the valve overlap is zero.

  In step S2, it is determined whether or not the variable valve mechanism 16 can be controlled and whether or not the valve timing can be detected. Specifically, it is possible to detect signals from a solenoid valve (not shown) for controlling the hydraulic pressure for driving the variable valve mechanism 16, the intake side cam angle sensor 19, the exhaust side cam angle sensor 20, and the like. Judge. If the signal can be detected, it is determined that the variable valve mechanism 16 can be controlled and the valve timing can be detected, and the process proceeds to step S3. If the signal cannot be detected, it is determined that each is impossible and the process proceeds to step S4.

  In step S3, the idle air amount correction value ISCVTC is calculated based on the operating angle of the variable valve mechanism 16 for the target valve timing (hereinafter referred to as the target VTC angle VTCTRG). The target VTC angle VTCTRG is a value determined according to the purpose of operation diagnosis and control value learning.

  The idle air amount correction value is calculated using the table shown in FIG. FIG. 4 shows the case where the intake air amount is adapted with reference to a state in which the valve overlap is zero during idle operation, and the vertical axis represents the idle air amount correction value ISCVTC and the horizontal axis represents the target VTC angle VTCTRG. The target VTC angle VTCTRG is set to the minimum value when the valve timing is the most retarded angle.

  As shown in FIG. 4, the idle air amount correction value ISCVTC has a maximum value when the target VTC angle VTCTRG is minimum, decreases as the target VTC angle VTCTRG advances, and becomes ISCVTC = 1 when the valve overlap is zero. Note that ISCVTC = 1 means “no correction”.

  In step S4, a value when the target VTC angle VTCTRG is minimum is set as the idle air amount correction value ISCVTC. That is, when the valve timing cannot be detected, the control is performed assuming that the state is the most retarded. As a result, the intake air amount will not be insufficient, and engine stall can be avoided reliably.

  In step S5, the product of the idle air amount correction value ISCVTC set in step S3 or step S4 and the base idle air amount ISC0 is calculated, and this is used as the idle air amount ISC.

  In step S6, the opening degree of the throttle valve 13 is controlled so that the idle air amount ISC calculated in step S5 is obtained. That is, when the idle air amount is increased from the base idle air amount ISC0 by the correction, the opening of the throttle valve 13 is increased by the increased amount.

  Here, the opening degree control of the throttle valve 13 will be described. In order to realize the corrected idle air amount ISC, control is performed by setting a target value of the opening of the throttle valve 13 (hereinafter referred to as target opening). The following methods can be used.

  As a first method, there is a method of calculating the closing timing of the intake valve 4 based on detection values of the intake cam angle sensor 19 and the crank angle sensor 21 and setting a target opening based on the calculated values. According to this, since the actual closing timing of the intake valve 4 is used, a necessary correction amount is set regardless of the operating state of the variable valve mechanism 16 such as the oil temperature and hydraulic pressure of the operating oil, for example. The effect of being able to be obtained.

  As a second method, there is a method of calculating the closing timing of the intake valve 4 based on the control target value of the variable valve mechanism 16 and setting the target opening based on this calculated value. According to this, since the throttle opening corresponding to the state after the operation of the variable valve 16 can be made at an early stage, the amount of air flowing into the combustion chamber 11 changes after the throttle opening is changed. The effect of the time delay is reduced, and the effect that stable idle air amount correction can be performed is obtained.

  As a third method, primary processing is performed on the closing timing calculated from the control target value of the variable valve mechanism 16 for the closing timing of the intake valve 4, and the target opening is set based on the closing timing after the primary processing. There is a technique. According to this, it is possible to provide an effect that it is possible to give a throttle opening faithfully corresponding to a time delay from when the throttle opening is changed to when the amount of air flowing into the combustion chamber 11 changes.

  Here, for example, oil temperature is used as the coefficient for the first-order lag processing. Since the oil pressure changes depending on the oil temperature, and the operating speed of the variable valve mechanism 16 also changes, the oil temperature is used as a coefficient, so that more accurate control is performed according to the operating state of the variable valve mechanism 16. be able to.

  When the engine speed, the operating angle of the variable valve mechanism 16, the idle air amount correction value ISCVTC, and the opening of the throttle valve 13 are changed when the above control is executed, only in general engine speed feedback correction And will be described. FIG. 5 is a time chart showing the case where the control of this embodiment is executed, and FIG. 6 is a time chart showing the case of only general engine speed feedback correction. The solid line in the chart represents the target value, and the broken line represents the actual value.

  When executing the control of the present embodiment, as shown in FIG. 5, when the target VTC angle VTCRG is changed to the minimum value at t1 during idling (engine speed Nidle, no valve overlap), In accordance with the control flowchart shown in FIG. 3, an idle air amount correction value ISCVTC larger than 1 is set, and the intake air amount is corrected to increase. As a result, the idling speed Nidle can be maintained even after t1 when the actual compression ratio decreases due to the retarded valve timing.

  On the other hand, when only the generally known idle speed feedback control is executed, as shown in FIG. 6, when the target VTC angle is changed to the retard side during idle operation, the valve The engine speed decreases with the timing delay. At this time, since feedback correction is performed so as to maintain the idling engine speed, the target value of the engine speed increases and the target value of the throttle opening also increases. However, in the case of feedback correction, the amount of intake air actually supplied to the combustion chamber 11 increases after the decrease in engine speed is detected until the throttle opening is actually increased, and after the throttle opening is increased. Since it takes time to do so, an increase in the intake air amount may not catch up with a decrease in the engine speed and may lead to an engine stall.

  As the variable valve mechanism 16, the present embodiment can be applied as long as the valve timing can be variably controlled. For example, as disclosed in Japanese Patent Application Laid-Open No. 2003-206765, etc. In addition, a mechanism capable of variably controlling the valve lift amount is also applicable.

  Further, although the case where the idle air amount is corrected by controlling the opening degree of the throttle valve 13 has been described, the air amount during idle operation is controlled by a valve for idle operation (so-called idle speed control valve) provided separately. It is also applicable to. In this case, the opening degree of the valve for idle operation is controlled according to the corrected idle air amount.

As described above, in this embodiment, the following effects can be obtained.
(1) Since the intake air amount during idle operation is controlled according to the closing timing of the intake valve 4, for example, when the variable valve mechanism 16 is driven during idle operation to change the valve timing, the actual compression ratio Even if the thermal efficiency changes with the change, the idling speed can be maintained.
(2) Since the air amount is controlled according to the closing timing of the intake valve 4 only when the valve overlap period is zero or negative, the influence of the change in the closing timing of the intake valve 4 on the generated torque fluctuation is large. However, the idling speed can be maintained reliably.
(3) Since the intake air amount is increased as the closing timing of the intake valve 4 is delayed, the intake air amount increases as the actual compression ratio decreases and the thermal efficiency decreases. As a result, the idling speed can be maintained.
(4) Since the actual detection value is used as the closing timing of the intake valve 4, the necessary intake air amount can be supplied regardless of the operating state of the variable valve mechanism 16 such as the oil temperature and hydraulic pressure.
(5) Since the closing timing calculated from the control target value of the variable valve mechanism 16 is used as the closing timing of the intake valve 4, the throttle opening corresponding to the state after the operation of the variable valve 16 can be made early. Thus, the influence of the time delay from the change of the throttle opening to the change of the amount of air flowing into the combustion chamber 11 is reduced, and stable idle air amount correction can be performed (6) Intake Primary processing is performed on the closing timing calculated from the control target value of the variable valve mechanism 16 for the closing timing of the valve 4, and the target opening is set based on the closing timing after the primary processing, so the throttle opening is changed. Therefore, it is possible to give a throttle opening faithfully corresponding to a time delay until the amount of air flowing into the combustion chamber 11 changes.
(7) Oil temperature is used as a coefficient for the first-order lag treatment. As a result, even when the hydraulic pressure changes depending on the oil temperature, and the operating speed of the variable valve mechanism 16 changes, more accurate control according to the operating state of the variable valve mechanism 16 can be performed. .
(8) When it is impossible to detect or calculate the closing timing of the intake valve 4, the closing timing of the intake valve 4 is the slowest in the mechanism of the variable valve mechanism 16, that is, it is necessary to maintain the idle speed. Since the opening degree of the throttle valve 13 is controlled so as to correspond to the state where the intake air amount is the largest, it is possible to prevent engine stall due to insufficient intake air amount.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is the schematic of the system configuration | structure of this embodiment. (A)-(c) is a figure showing the example of the valve timing used by this embodiment. It is a figure showing the control routine of idle air quantity correction | amendment. It is a table for idle air quantity correction value calculation. It is a time chart at the time of performing idle air amount correction | amendment of this embodiment. Time chart when only idle speed feedback correction is executed

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 3 Exhaust passage 4 Intake valve 5 Exhaust valve 6 Intake camshaft 7 Exhaust camshaft 8 Spark plug 9 Piston 10 Crankshaft 11 Combustion chamber 12 Collector part 13 Throttle valve 14 Air flow meter 15 Control unit (ECU)
DESCRIPTION OF SYMBOLS 16 Variable valve mechanism 17 Fuel injection valve 18 Water temperature sensor 19 Intake side cam angle sensor 20 Exhaust side cam angle sensor 21 Crank angle sensor 22 Air-fuel ratio sensor 23 Accelerator opening sensor 24 Throttle position sensor 25 NOx catalyst 26 Three-way catalyst

Claims (9)

An intake valve that opens and closes in synchronization with the rotation of the internal combustion engine;
A variable valve mechanism capable of variably controlling the opening and closing timing of the intake valve;
Intake air amount control means for controlling the intake air amount of the internal combustion engine;
With
The intake air amount control means controls the intake air amount according to the closing timing of the intake valve only when the internal combustion engine is idling and the valve overlap period is zero or negative. An internal combustion engine characterized by performing control. Internal combustion engine according to claim 1, characterized in that Ru provided with a valve overlap calculation means for calculating the pre fangs lube overlap period. The internal combustion engine according to claim 1 or 2, wherein the idle air amount control increases the intake air amount as the closing timing of the intake valve is delayed. An intake valve operation timing detection means for detecting at least the closing timing of the intake valve;
The said intake air amount control means performs the said idle air amount control using the detected value of the said intake valve action | operation timing detection means as a closing timing of the said intake valve, The one of Claim 1 to 3 characterized by the above-mentioned. Internal combustion engine as described in one. 2. The intake air amount control means executes the idle air amount control using an intake valve closing timing calculated from a control target value of the variable valve mechanism as a closing timing of the intake valve. The internal combustion engine as described in any one of 1-3. The intake air amount control means executes the idle air amount control by using the intake valve closing timing calculated from the control target value of the variable valve mechanism as the closing timing of the intake valve and subjected to first-order lag processing. The internal combustion engine according to any one of claims 1 to 3, wherein Oil temperature means for detecting the oil temperature of the internal combustion engine,
The internal combustion engine according to claim 6, wherein the intake air amount control means performs the first-order lag process using a detection value of the oil temperature detection means as a first-order lag coefficient. If it is impossible to detect or calculate the closing timing of the intake valve, the intake air amount control means controls the intake air amount assuming that it is the latest intake valve closing timing in terms of the variable valve mechanism. The internal combustion engine according to claim 1 or 2, characterized by the above. 9. The internal combustion engine according to claim 1, wherein the intake air amount control means is an electronically controlled throttle valve.