JP2010180774A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of stabilizing combustion, and capable of improving exhaust emission, by suitably restraining the direct inflow of blow-by gas in a combustion chamber via a piston clearance. <P>SOLUTION: In starting control of an engine 10 when opening of a throttle valve 45 becomes small (negative pressure in the combustion chamber 31 becomes large), whether or not a vaporized fuel quantity in the blow-by gas falls within an allowable range is determined from an injection quantity correction quantity (the fuel dilution ratio), the present oil temperature and a soak time in idle operation just before stopping the engine last time. When a determination is made that the vaporized fuel quantity in the blow-by gas exceeds the allowable range, control is performed for adjusting the suction air volume by blowing back intake air by changing the valve closing timing of an intake valve 35 to the ignition timing delay side in response to its control together with the control for fully opening the opening of the throttle valve 45. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that suitably suppresses disturbance of an air-fuel ratio caused by blow-by gas.

  As an internal combustion engine provided with a blow-by gas reduction device, for example, the one described in Patent Document 1 is known. The blow-by gas reduction device connects the downstream side of the throttle valve in the intake passage and the crank chamber to a first ventilation passage for supplying blow-by gas in the crank chamber to the intake passage, the upstream side of the throttle valve in the intake passage and the crank The second ventilation passage is connected to the room and supplies intake air into the crankcase, and the ventilation valve is provided in the first ventilation passage and changes the passage area. During operation of the internal combustion engine, the required flow rate of blow-by gas is set based on the engine operating state, and the opening degree of the ventilation valve is controlled so that the actual flow rate of blow-by gas becomes the required value. .

JP 2006-52664 A

  By the way, the throttle valve is close to the fully closed state at the time of starting control of the internal combustion engine, idling operation, and the like, so that the combustion chamber becomes greatly negative pressure as the piston descends during the intake stroke of the internal combustion engine. Then, in addition to the normal reduction of the blow-by gas in the crank chamber through the ventilation passage described above, an event occurs in which a part of the blow-by gas flows directly from the crank chamber into the combustion chamber through the piston clearance. This direct flow of blow-by gas through the piston clearance into the combustion chamber causes air-fuel ratio disturbance and causes fluctuations in combustion and deterioration of exhaust emissions, especially at high engine oil fuel dilution rates. At the time of restart, the fuel vaporization amount is large and the fuel component is contained in the blow-by gas, so that the air-fuel ratio becomes too rich and combustion fluctuations and exhaust emission are liable to occur. Therefore, it is desired to solve this problem. It was.

  The present invention has been made to solve the above-described problems, and its object is to suitably suppress direct inflow of blow-by gas into the combustion chamber via the piston clearance, thereby stabilizing combustion and exhaust emission. It is an object of the present invention to provide a control device for an internal combustion engine that can improve the efficiency.

  In order to solve the above problem, the invention according to claim 1 is configured such that the intake air amount is adjusted according to the opening of the throttle valve, and the mixture of the adjusted intake air and the fuel injected from the injector is burned. Control of an internal combustion engine that is an internal combustion engine that obtains power by burning indoors, and includes a blow-by gas reduction means that reduces blow-by gas to an intake passage, and a valve characteristic changing means that can change a valve characteristic of the intake valve When the operating state of the internal combustion engine in which the throttle valve is small and the negative pressure in the combustion chamber is large is determined, it is determined whether or not the amount of vaporized fuel in the blow-by gas is within an allowable range. If it is determined that the amount of vaporized fuel in the blow-by gas exceeds an allowable range, the throttle valve opening is controlled, and the intake valve is closed accordingly. As its gist to carry out control for timing the perform blow-back of intake air is changed to the retard side.

  In the present invention, when the internal combustion engine is in an operating state (for example, during start-up control, idle operation, engine low load, etc.) in which the throttle valve opening is small and the negative pressure in the combustion chamber is large, the piston clearance is interposed. Since direct inflow of blow-by gas into the combustion chamber occurs, it is determined whether or not the amount of vaporized fuel in the blow-by gas is within an allowable range. If it is determined that the amount of vaporized fuel in the blow-by gas exceeds the allowable range, the air-fuel ratio becomes too rich and a combustion failure may occur, so the throttle valve opening is increased and the combustion chamber is at or near atmospheric pressure. The negative pressure state is eliminated as a state, and the direct inflow of the blow-by gas with a large amount of vaporized fuel into the combustion chamber at this time is suppressed, and the air-fuel ratio is prevented from becoming too rich. Correspondingly, the closing timing of the intake valve is changed to the retard side, and the intake air is blown back to adjust the intake air amount. As a result, the air-fuel ratio changes favorably even in operating conditions where the negative pressure in the combustion chamber is large and the amount of vaporized fuel in the blow-by gas increases (such as when restarting at a high temperature when the fuel dilution rate of engine oil is high). Stabilization of combustion and improvement of exhaust emission are achieved.

  According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect, the internal combustion engine is an engine compatible with alcohol fuel, and at the time of the determination, a comparison result between the oil temperature of the engine oil and the boiling point of the alcohol is obtained. The gist is that the determination is made.

  In the present invention, the above-described determination and control are performed for an alcohol fuel compatible internal combustion engine, and at the time of the determination, the determination is made including the comparison result between the oil temperature of the engine oil and the boiling point of the alcohol. In an internal combustion engine compatible with alcohol fuel, for example, when the fuel used is E100 (100% ethanol), the amount of fuel injection is increased compared to a gasoline engine, so that dilution into engine oil is easy to proceed, and a single diluted fuel is used. Since it is a component (only ethanol), when the oil temperature of the engine oil exceeds the boiling point of ethanol, the diluted fuel starts to vaporize rapidly, and the amount of vaporized fuel in the blow-by gas increases rapidly. Significance of applying the present invention Is big.

It is a schematic block diagram which shows the internal combustion engine of this embodiment. It is explanatory drawing explaining the flow of blow-by gas in the internal combustion engine, and an intake air, (a) is a figure which shows the case where a throttle opening is set to a normal opening, (b) is a throttle opening set to full open. FIG. It is explanatory drawing for demonstrating the valve characteristic of the internal combustion engine. It is a correlation diagram showing the correlation between the injection amount correction amount and the fuel dilution rate of the internal combustion engine. It is a flowchart which shows the negative pressure control process in the internal combustion engine. It is explanatory drawing for demonstrating transition of an engine speed (NE) and an air fuel ratio at the time of starting control of the internal combustion engine.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, an in-cylinder injection type engine 10 according to this embodiment includes an engine body 20 for generating power through combustion of a mixture of air and fuel (gasoline), and external air. 20, an electronically controlled blow-by gas reduction device 50 for supplying blow-by gas in the engine body 20 to the intake device 40, and an electronic control device 60 for comprehensively controlling these devices. It is configured with.

  The engine body 20 accommodates a mixture of fuel directly injected into the combustion chamber 31 through the injector 27 and air supplied into the combustion chamber 31 through the intake device 40 while the piston 26 is accommodated in a reciprocating manner. A cylinder block 21 for burning, a crankcase 22 for supporting the crankshaft 28 in cooperation with the cylinder block 21, an oil pan 23 for storing engine oil, and valve system components are arranged. And a head cover 25 for suppressing scattering of engine oil to the outside. A crank chamber 32 formed by the cylinder block 21 and the crankcase 22 and a valve operating chamber 33 formed by the cylinder head 24 and the head cover 25 are connected by a communication chamber 34 formed in the cylinder block 21. .

  The engine body 20 includes a variable valve timing device (VVT) 37 that changes the valve characteristics of the intake valve 35 of the intake and exhaust valves 35, 36 that are provided (adjusts the amount of advance or retard during the valve opening period). Is provided. The variable valve timing device 37 on the intake side continuously changes the valve timing of the intake valve 35 with respect to the crank angle within a predetermined range by changing the relative rotational phase of the intake cam (camshaft) 38 with respect to the crankshaft 28. It is a mechanism for adjusting automatically. Then, the valve timing of the intake valve 35 is maintained by the operation of the valve timing varying device 37 with the valve opening period (period from the valve opening timing to the valve closing timing) being kept constant as shown in FIG. It can be advanced or retarded.

  The intake device 40 includes an air intake 41 for taking outside air into the device, an air cleaner 42 for catching foreign matter in the air taken in through the air intake 41, and intake air through opening and closing of a throttle valve 45. A throttle body 44 for adjusting the amount, an intake hose 43 connecting the intake downstream side of the air cleaner 42 and the intake upstream side of the throttle body 44, an intake downstream side of the throttle body 44, and an intake upstream side of the cylinder head 24 And an intake manifold 46 for connecting the two. The intake manifold 46 is provided with a surge tank 47 for retaining the intake air that has passed through the throttle body 44 and a plurality of sub-pipes 48 for sending the intake air in the surge tank 47 to the intake ports of the cylinder head 24. ing. That is, in the intake device 40, the intake air is supplied to the engine by the passage in the air intake 41, the passage in the air cleaner 42, the passage in the intake hose 43, the passage in the throttle body 44, and the passage in the intake manifold 46. An intake passage 49 for feeding into the main body 20 is formed.

  The blow-by gas reduction device 50 has a function of supplying blow-by gas flowing out from the combustion chamber 31 into the crank chamber 32 to the intake downstream side of the throttle valve 45 in the intake device 40, and the intake air purified by the air cleaner 42. 40 is configured as a device having a function of supplying the crank chamber 32 from the intake upstream side of the throttle valve 45 in the engine 40 and a function of adjusting the flow rate of blow-by gas supplied from the engine body 20 to the intake device 40. .

  Specifically, the first ventilation passage 51 formed in a manner of connecting the head cover 25 and the surge tank 47 as a passage for sending blow-by gas in the crank chamber 32 into the surge tank 47 from the valve operating chamber 33. Is provided. Further, the head cover 25 and the intake hose 43 are connected as a passage for sending intake air in the intake hose 43 into the valve operating chamber 33 or as a passage for sending blow-by gas into the intake hose 43 from the valve operating chamber 33. A second ventilation passage 52 formed in such a manner is provided. In addition, as a valve for adjusting the flow rate of blow-by gas flowing from the valve operating chamber 33 toward the surge tank 47, a PCV valve 53 provided on the head cover 25 and changing the passage area of the first ventilation passage 51 is provided. It has been. Under the same engine operating conditions, the flow rate of blow-by gas supplied from the valve operating chamber 33 to the surge tank 47 is increased by changing the opening of the PCV valve 53 to the valve opening side. It becomes like this.

  In the electronic control unit 60, as various sensors for assisting engine control, an accelerator position sensor 61 that outputs a signal corresponding to the depression amount of the accelerator pedal of the vehicle, and the rotational speed (engine rotational speed) of the crankshaft 28 are used. A crank position sensor 62 that outputs a corresponding signal, an air flow meter 63 that outputs a signal corresponding to the amount of intake air flowing through the intake passage 49, and a signal that corresponds to the opening of the throttle valve 45 (throttle opening). The throttle position sensor 64, the coolant temperature sensor 65 that outputs a signal corresponding to the temperature of the engine coolant that cools the engine body 20, and the oil that outputs a signal corresponding to the temperature of the engine oil circulating in the engine body 20 A signal corresponding to the air-fuel ratio of the mixture based on the temperature sensor 66 and the oxygen concentration in the exhaust gas. Such an air-fuel ratio sensor 67 to force is provided.

  The electronic control unit 60 grasps the driver's request and the engine operating state based on the detection results of the respective sensors, and then performs throttle control for adjusting the intake air amount and injection control for adjusting the fuel injection amount by the injector 27. , And air-fuel ratio control for bringing the air-fuel ratio of the air-fuel mixture close to the target value, valve timing control for adjusting the advance / retard amount during the valve opening period of the intake valve 35, and supply from the engine body 20 into the intake device 40 Perform various controls such as ventilation control to adjust the flow rate of blow-by gas.

  Incidentally, at the time of starting control of the engine 10 or at the time of idling operation, as shown in FIG. 2A, the throttle valve 45 is normally set close to a fully closed state and the throttle opening is set small. As the piston 26 descends during the intake stroke, the inside of the combustion chamber 31 becomes a large negative pressure. Therefore, blow-by gas flows into the intake passage 49 from the crank chamber 32 through the communication chamber 34, the valve operating chamber 33, and the first ventilation passage 51. At this time, fresh air flows into the valve operating chamber 33 through the second ventilation passage 52. Further, since the inside of the combustion chamber 31 has a large negative pressure, a part of the blow-by gas in the crank chamber 32 directly enters the combustion chamber 31 via the piston clearance (clearance between the piston 26 and the cylinder block 21). Inflows can also occur.

  Here, when a start command (ignition key is turned on) is input during the start control of the engine 10, the electronic control unit 60 performs the start control and starts from the blow-by gas piston clearance that causes combustion failure. In order to suppress the direct inflow of the negative pressure, a negative pressure control process for eliminating the negative pressure state in the combustion chamber 31 is executed. FIG. 5 is a flowchart of the negative pressure control process.

  In step S10, the correction amount of the fuel injection amount by the injector 27 is read from, for example, the operating condition at the time of idle operation immediately before the previous stop of the engine 10, and the fuel dilution rate of the engine oil is calculated from the read injection amount correction amount. To do. Incidentally, as shown in FIG. 4, the injection amount correction amount and the fuel dilution rate of the engine oil have a correlation that the fuel dilution rate of the engine oil becomes higher when the injection amount correction amount is larger on the decrease side. The fuel dilution rate is calculated from the correlation.

  If the fuel dilution ratio increases, the amount of vaporized fuel contained in the blow-by gas increases, which causes a combustion failure such as combustion fluctuation and exhaust emission deterioration. In the next step S20, the calculated fuel dilution ratio is a determination value. It is determined whether or not Odini is exceeded. If it is determined that the calculated fuel dilution rate is smaller than the determination value Odini and is within an allowable range in which combustion failure does not occur, this negative pressure control process is terminated.

  On the other hand, if it is determined that the calculated fuel dilution rate exceeds the determination value Odini and is a dilution rate that may cause a combustion failure, in the next step S30, the current engine oil temperature and the previous engine stop time are The soak time, which is the elapsed time until the start of, is read, and the vaporization amount of the diluted fuel, that is, the vaporized fuel amount contained in the blow-by gas is calculated from these. If the current oil temperature is high and the soak time is long, the amount of vaporized fuel contained in the blowby gas increases.

  When the amount of vaporized fuel is large, the combustion chamber 31 has a large negative pressure during start-up control with a small throttle opening, so blow-by gas with a large amount of vaporized fuel directly enters the combustion chamber 31 via the piston clearance. Since the above-described combustion failure occurs due to the inflow, in the next step S40, it is determined from the calculated vaporized fuel amount whether there is a possibility of the occurrence of the combustion failure. If it is determined that the calculated amount of vaporized fuel is small and within the allowable range and there is no possibility of combustion failure, this negative pressure control process is terminated.

  On the other hand, when it is determined that the calculated amount of vaporized fuel exceeds the allowable range and there is a possibility of combustion failure, a throttle fully open control command is output in the next step S50, as shown in FIG. In addition, the throttle valve 45 is controlled to be fully opened. Then, in the intake stroke, the interior of the combustion chamber 31 becomes atmospheric pressure or a state close to atmospheric pressure, the negative pressure state is eliminated, and direct inflow of blow-by gas with a large amount of vaporized fuel from the piston clearance is suppressed. Thereby, for example, the air-fuel ratio is not excessively rich even when restarting at a high temperature when the fuel dilution rate of the engine oil is high.

  In the next step S60, a VVT control command for changing the valve opening period of the intake valve 35 to the retard side is output in response to the full opening control of the throttle valve 45. That is, if the throttle valve 45 is fully opened as described above, the intake air introduced into the combustion chamber 31 is excessively increased. Therefore, in order to prevent this, as shown by the solid line in FIG. 3, the intake valve 35 is delayed so that the intake valve 35 opens even when the compression stroke is started, and the intake air is not excessively sucked into the combustion chamber 31. In this way, the intake air is blown back to adjust the intake air amount.

  In the present embodiment, in the next step S70, a PCV valve control command for controlling the PCV valve 53 to be fully closed is output. That is, since the negative pressure state in the combustion chamber 31 is eliminated, the regular reduction amount of the blowby gas passing through the passages 51 and 52 is also reduced. Therefore, the reduction amount of the blowby gas is extremely reduced by fully closing the PCV valve 53. By reducing it, the controllability of the air-fuel ratio can be improved. Then, the negative pressure control process is terminated through step S70.

  Accordingly, in the present embodiment, the electronic control unit 60 performs the negative pressure control process at the time of starting control of the engine 10, so that it is shown in FIG. Thus, the air-fuel ratio changes favorably and combustion is stabilized, so that the engine rotational speed (NE) is stabilized and the exhaust emission is improved.

Next, characteristic effects of the present embodiment will be described.
(1) In the present embodiment, the blow-by gas directly enters the combustion chamber 31 via the piston clearance during start control of the engine 10 where the throttle valve 45 is small and the negative pressure in the combustion chamber 31 is large. Therefore, the amount of vaporized fuel in the blow-by gas is within the allowable range based on the injection amount correction amount (fuel dilution rate), the current oil temperature, and the soak time during idle operation immediately before the last engine stop. It is determined whether or not (steps S10 to S40). If it is determined that the amount of vaporized fuel in the blow-by gas exceeds the allowable range, the opening of the throttle valve 45 is fully opened (step S50), assuming that the air-fuel ratio becomes too rich and a combustion failure may occur (step S50). The negative pressure state is eliminated by setting the inside of the engine 31 to atmospheric pressure or a state close to atmospheric pressure, and the direct inflow of the blow-by gas with much vaporized fuel into the combustion chamber 31 at this time is suppressed, and the air-fuel ratio becomes too rich. Is prevented. Correspondingly, the closing timing of the intake valve 35 is changed to the retard side, and the intake air is blown back (step S60), and the intake of the intake air into the combustion chamber 31 is increased by increasing the opening of the throttle valve 45. Passing is suppressed and the intake air amount is adjusted. As a result, the air-fuel ratio changes favorably even in operating conditions where the negative pressure in the combustion chamber 31 is large and the amount of vaporized fuel in the blow-by gas is large (such as during high-temperature restart when the fuel dilution rate of the engine oil is high). It is possible to stabilize combustion and improve exhaust emission.

In addition, you may change embodiment of this invention as follows.
In the above embodiment, the present invention is applied at the time of starting control of the engine 10 where the opening of the throttle valve 45 is small and the negative pressure in the combustion chamber 31 is large, but may be applied at the time of idling operation or low engine load.

In the above embodiment, the throttle valve 45 is fully opened when the amount of vaporized fuel in the blow-by gas exceeds the allowable range. However, the throttle valve 45 may be increased to the open side rather than normal before full opening.
In the above-described embodiment, the present invention is applied to the in-cylinder injection engine 10, but may be applied to an engine that performs port injection.

  In the above embodiment, the present invention is applied to the engine 10 that uses gasoline fuel, but may be applied to an engine that uses, for example, ethanol fuel as the alcohol fuel. In an engine compatible with alcohol fuel, for example, when the fuel used is E100 (100% ethanol), the fuel injection amount increases compared to a gasoline engine, so that dilution into engine oil is easy to proceed, and the diluted fuel is a single component. (Ethanol only) Therefore, when the oil temperature of the engine oil exceeds the boiling point of ethanol, the diluted fuel starts to vaporize rapidly, and the amount of vaporized fuel in the blowby gas increases rapidly. large.

  In the case of an engine compatible with alcohol fuel, an alcohol sensor may be used to obtain the dilution rate of alcohol fuel into engine oil. Further, in determining whether the amount of vaporized fuel in the blow-by gas is within an allowable range, it is possible to make an easy and accurate determination by referring to the boiling point of the alcohol used for the fuel.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 27 ... Injector, 31 ... Combustion chamber, 35 ... Intake valve, 37 ... Valve timing variable device (valve characteristic changing means), 45 ... Throttle valve, 49 ... Intake passage, 50 ... Blow-by gas reduction Device (blow-by gas reduction means), 60... Electronic control device (control device).

Claims (2)

An internal combustion engine that obtains power by burning an air-fuel mixture of the adjusted intake air and fuel injected from the injector in a combustion chamber in accordance with the opening of the throttle valve. A control device for an internal combustion engine comprising a blow-by gas reduction means for performing reduction to a passage and a valve characteristic changing means capable of changing a valve characteristic of an intake valve,
When the throttle valve opening is small and the negative pressure in the combustion chamber is in an operating state of the internal combustion engine, it is determined whether the amount of vaporized fuel in the blow-by gas is within an allowable range,
If it is determined that the amount of vaporized fuel in the blow-by gas exceeds an allowable range, the opening degree of the throttle valve is increased and the closing timing of the intake valve is changed to the retard side accordingly. A control device for an internal combustion engine, characterized in that control is performed to blow back intake air. The control apparatus for an internal combustion engine according to claim 1,
The internal combustion engine is an alcohol fuel-compatible engine, and at the time of the determination, the determination is made by including a comparison result between the oil temperature of the engine oil and the boiling point of the alcohol.

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