JP7256682B2 - Internal combustion engine control method and internal combustion engine control device - Google Patents

Description

The present invention relates to an internal combustion engine control method and an internal combustion engine control apparatus.

For example, Patent Document 1 discloses an internal combustion engine that closes the exhaust valve before the piston reaches exhaust top dead center by advancing the opening timing and closing timing of the exhaust valve during inertial rotation of the engine after fuel cut. disclosed.

That is, Patent Document 1 discloses an internal combustion engine in which the exhaust valve is closed early to trap the internal EGR in the cylinder, and the internal EGR is blown back to the intake stroke to blow off the condensed water on the upstream side of the combustion chamber. ing.

Therefore, in Patent Document 1, when the intake valve opens, the compressed residual gas in the cylinder blows back to the intake port, blowing off the condensed water adhering to the inner walls of the intake manifold and the intake port. This suppresses the inflow of condensed water into the combustion chamber from the intake manifold and the intake port, thereby preventing corrosion of the injectors in the combustion chamber.

The internal combustion engine of Patent Document 1 introduces a part of exhaust gas after combustion into an intake passage as exhaust gas recirculation gas (EGR gas).

JP 2014-47756 A

However, in the internal combustion engine disclosed in Patent Document 1, the generated condensed water becomes a working fluid together with the combustion gas in the cylinder. As a result, the combustion stability deteriorates.

The internal combustion engine of the present invention has a valve timing changing mechanism capable of changing the valve timing of the intake valve, and when it is detected that condensed water is generated on the upstream side of the combustion chamber, the valve timing of the intake valve is changed to change the valve timing of the intake valve. The valve closing timing of the intake valve is retarded so that the valve opening period of the intake valve straddles the bottom dead center .

As a result, in the internal combustion engine, the amount of blowback gas to the intake port increases, so the temperature of the gas in the cylinder rises and the vaporization of the condensed water is accelerated.

According to the present invention, the combustion stability of the internal combustion engine is ensured by promoting the vaporization of condensed water, and damage to parts due to incomplete combustion such as misfire can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically showing the schematic configuration of an internal combustion engine according to the present invention; 4 is a timing chart showing the correlation between valve timing of an internal combustion engine and cylinder internal gas temperature; Flowchart showing an example of the control flow of an internal combustion engine

An embodiment of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram schematically showing the schematic configuration of an internal combustion engine 1 according to the present invention.

The internal combustion engine 1 is a 4-stroke cycle spark ignition type engine equipped with a variable compression ratio mechanism 2 utilizing a multi-link piston crank mechanism, and is mounted on a vehicle such as an automobile as a drive source or the like. . The internal combustion engine 1 is, for example, a gasoline engine or a diesel engine.

The variable compression ratio mechanism 2 utilizes a known multi-link type piston crank mechanism described, for example, in Japanese Unexamined Patent Application Publication No. 2004-116434.

The internal combustion engine 1 is mounted on a vehicle such as an automobile as a drive source, and has an intake passage 3 and an exhaust passage 4 . The intake passage 3 is connected to a combustion chamber 6 of the internal combustion engine 1 via an intake valve 5 . The exhaust passage 4 is connected to the combustion chamber 6 of the internal combustion engine 1 via an exhaust valve 7 .

The internal combustion engine 1 is of, for example, an in-cylinder direct injection type, and a fuel injection valve (not shown) for injecting fuel into the cylinder and a spark plug 8 are provided for each cylinder. The injection timing and injection amount of the fuel injection valve and the ignition timing of the ignition plug 8 are controlled by control signals from the control unit 9 .

The intake passage 3 includes an air cleaner 11 that collects foreign matter in the intake air, an air flow meter 12 that detects the amount of intake air, an electric first throttle valve 13 , and an electric throttle valve 13 located upstream of the first throttle valve 13 . and a second throttle valve 14 are provided.

The airflow meter 12 is arranged upstream of the second throttle valve 14 . The airflow meter 12 incorporates a temperature sensor and can detect the intake air temperature of the intake inlet.

The air cleaner 11 is arranged upstream of the air flow meter 12 .

The first throttle valve 13 controls the intake air amount of the internal combustion engine 1 according to the load. The second throttle valve 14 controls intake pressure on the upstream side of a compressor 22, which will be described later.

The exhaust passage 4 is provided with an upstream side exhaust purification device 17, a downstream side exhaust purification device 18, an underfloor catalyst 19, and a muffler 20 for reducing exhaust noise. The upstream side exhaust purification device 17 is composed of, for example, a three-way catalyst or the like. The downstream side exhaust purification device 18 is composed of, for example, a three-way catalyst or the like, and is arranged at a position downstream of the upstream side exhaust purification device 17 and upstream of the underfloor catalyst 19 . The underfloor catalyst 19 is composed of, for example, a three-way catalyst or the like, and is arranged downstream of the downstream side exhaust purification device 18 . The muffler 20 is arranged downstream of the underfloor catalyst 19 .

The internal combustion engine 1 also has a turbocharger 21 .

The turbocharger 21 has a compressor 22 provided in the intake passage 3 and a turbine 23 provided in the exhaust passage 4 . Compressor 22 and turbine 23 are coaxially arranged and rotate together. The compressor 22 is located upstream of the first throttle valve 13 and downstream of the second throttle valve 14 . The turbine 23 is arranged upstream of the upstream exhaust purification device 17 .

An intake bypass passage 24 is connected to the intake passage 3 .

The intake bypass passage 24 is formed to bypass the compressor 22 and communicate between the upstream side and the downstream side of the compressor 22 .

An electric recirculation valve 25 is provided in the intake bypass passage 24 . The recirculation valve 25 is normally closed, but is opened when the first throttle valve 13 is closed and the downstream side of the compressor 22 becomes high pressure. By opening the recirculation valve 25 , the high-pressure intake air downstream of the compressor 22 can be returned to the upstream side of the compressor 22 via the intake bypass passage 24 . The recirculation valve 25 is controlled to open and close by a control signal from the control unit 9 . The recirculation valve 25 may be a so-called check valve that opens only when the pressure on the downstream side of the compressor 22 reaches a predetermined pressure or more, instead of being controlled by the control unit 9. It is possible.

Further, the intake passage 3 is provided with an intercooler 26 downstream of the first throttle valve 13 for cooling the intake air compressed (pressurized) by the compressor 22 to improve charging efficiency.

An exhaust bypass passage 31 that bypasses the turbine 23 and connects the upstream side and the downstream side of the turbine 23 is connected to the exhaust passage 4 . A downstream end of the exhaust bypass passage 31 is connected to the exhaust passage 4 at a position upstream of the upstream exhaust purification device 17 . An electric wastegate valve 32 is arranged in the exhaust bypass passage 31 to control the flow rate of the exhaust gas in the exhaust bypass passage 31 .

Further, the internal combustion engine 1 is capable of performing exhaust gas recirculation (EGR) in which part of the exhaust gas is introduced (recirculated) from the exhaust passage 4 into the intake passage 3 as EGR gas. It has an EGR passage 33 as an exhaust gas recirculation passage connected to the intake passage 3 . One end of the EGR passage 33 is connected to the exhaust passage 4 at a position between the downstream side exhaust purification device 18 and the underfloor catalyst 19 , and the other end is downstream of the second throttle valve 14 and upstream of the compressor 22 . It is connected to the intake passage 3 at the position. The EGR passage 33 is provided with an electric EGR valve 34 that adjusts (controls) the EGR gas flow rate in the EGR passage 33 and an EGR cooler 35 that can cool the EGR gas.

The internal combustion engine 1 has an intake side variable valve mechanism 41 as a valve timing change mechanism capable of changing the valve timing (opening/closing timing) of the intake valve 5 as a valve mechanism for the intake valve 5 .

The intake side variable valve mechanism 41 is a phase variable mechanism that continuously advances or retards the phase of the center angle of the lift of the intake valve 5 (the phase with respect to the crankshaft 43). The variable phase mechanism is already known from, for example, Japanese Unexamined Patent Application Publication No. 2002-89303, and the phase of the intake side camshaft 42 that drives the opening and closing of the intake valve 5 is changed with respect to the crankshaft (not shown). to slow down.

The exhaust valve-side valve mechanism is a general direct-acting valve mechanism, and the phases of the lift operation angle and the lift central angle of the exhaust valve 7 are always constant.

The intake side variable valve mechanism 41 is hydraulically driven, for example, and is controlled by a control signal from the control unit 9 . In other words, the valve timing of the intake valve 5 can be variably controlled by the control unit 9 .

Note that the intake side variable valve mechanism 41 may be of a type capable of individually and independently changing the opening timing and closing timing of the intake valve 5 . The intake side variable valve mechanism 41 is not limited to being hydraulically driven, and may be electrically driven by a motor or the like.

Also, the intake-side variable valve mechanism 41 may be a variable lift operation angle mechanism capable of changing the lift amount and the operation angle of the intake valve 5 . The variable lift operating angle mechanism is already known from, for example, Japanese Patent Application Laid-Open No. 2002-89303, and it simultaneously and continuously increases and decreases the lift amount and operating angle of the intake valve 5 .

The intake-side variable valve mechanism 41 includes a variable phase mechanism that continuously advances or retards the phase of the center angle of the lift of the intake valve 5, and a lift that can change the lift amount and operating angle of the intake valve 5. and a variable operating angle mechanism.

The valve timing of the intake valve 5 is detected by an intake side camshaft position sensor 45 . The intake camshaft position sensor 45 detects the phase of the intake camshaft 42 with respect to the crankshaft 43 .

Here, the control unit 9 is a well-known digital computer equipped with a CPU, ROM, RAM and an input/output interface.

The control unit 9 includes the airflow meter 12 and the detection signal (detected value) of the intake side camshaft position sensor 45, as well as the crank angle sensor 46 capable of detecting the crank angle of the crankshaft 43 and the engine speed, and the internal combustion engine. 1, an accelerator opening sensor 47 that detects the amount of accelerator pedal depression (accelerator opening APO) representing the required load state, an intake air temperature sensor 48 that detects the intake air temperature at a position downstream of the intercooler 26, Detection signals (detection values) of various sensors such as the humidity sensor 49 for detecting the humidity of the intake air at the position of are inputted.

The intake air temperature sensor 48 detects the intake air temperature at a position downstream of the intercooler 26 and upstream of the combustion chamber 6, and is arranged near the outlet of the intercooler 26, for example.

The humidity sensor 49 detects the humidity of the intake air at a position downstream of the intercooler 26 and upstream of the combustion chamber 6, and is arranged near the outlet of the intercooler 26, for example.

The intake air temperature sensor 48 and the humidity sensor 49 are desirably arranged near the combustion chamber 6 .

The control unit 9 uses the detected value of the accelerator opening sensor 47 to calculate the required load (engine load) of the internal combustion engine 1 .

The control unit 9 controls the fuel injection amount and fuel injection timing by the fuel injection valve, the ignition timing by the ignition plug 8, the valve timing of the intake valve 5, and the first throttle valve 13, based on detection signals from various sensors. opening degree, opening degree of the second throttle valve 14, opening degree of the wastegate valve 32, opening degree of the recirculation valve 25, opening degree of the EGR valve 34, mechanical compression ratio of the internal combustion engine 1 by the variable compression ratio mechanism 2 etc. are optimally controlled.

Also, the control unit 9 uses the detected values of the humidity sensor 49 and the intake air temperature sensor 48 to estimate whether or not condensed water is generated in the combustion chamber 6 . In other words, the control unit 9 corresponds to a condensed water detector capable of detecting condensed water generated on the upstream side of the combustion chamber 6 .

The closing timing of the intake valve 5 of the internal combustion engine 1 is basically set near the bottom dead center (near the bottom dead center) so that knocking does not occur.

In the internal combustion engine 1, by setting the closing timing of the intake valve 5 before the bottom dead center, there is no blow-back from the combustion chamber 6, and the temperature in the combustion chamber 6 (inside the cylinder) can be lowered. is lowered and knocking is suppressed.

When the control unit 9 detects the generation of condensed water, the control unit 9 changes the valve timing of the intake valve 5 so that the closing timing of the intake valve 5 is retarded as shown in FIG. In other words, the control unit 9 corresponds to a valve timing control section that retards the closing timing of the intake valve 5 when condensed water is detected.

FIG. 2 is a timing chart showing the correlation between the valve timing of the internal combustion engine 1 and the gas temperature in the combustion chamber 6 (in-cylinder gas temperature).

Time t1 is the timing of the top dead center in the expansion stroke (compression stroke). Time t2 is the timing of the bottom dead center in the expansion stroke (exhaust stroke). Time t3 is the opening timing (IVO) of the intake valve 5 during normal operation (when no condensed water is generated). Time t4 is the timing of the top dead center in the exhaust stroke (intake stroke). Time t5 is the closing timing (IVC) of the intake valve 5 during normal operation (when no condensed water is generated). Time t6 is the timing of the bottom dead center in the intake stroke (compression stroke). Time t7 is the closing timing (IVC) of the intake valve 5 when condensed water is generated.

The valve timing of the intake valve 5 of the internal combustion engine 1 basically opens near the top dead center and closes before the bottom dead center and near the bottom dead center, as indicated by the dashed line in FIG. is set to

When the control unit 9 detects the generation of condensed water on the upstream side of the combustion chamber 6, the control unit 9 retards the valve timing of the intake valve 5 to retard the closing timing of the intake valve 5 from the bottom dead center.

Specifically, when the control unit 9 detects the generation of condensed water on the upstream side of the combustion chamber 6, the control unit 9 adjusts the closing timing of the intake valve 5 so that the opening period of the intake valve 5 straddles the bottom dead center in the intake stroke. retard.

In the internal combustion engine 1, the closing timing of the intake valve 5 is retarded from the bottom dead center of the intake stroke, thereby increasing the amount of gas blown back to the intake port.

Therefore, the in-cylinder gas temperature of the internal combustion engine 1 rises, as indicated by the solid line in FIG. The dashed line in FIG. 2 indicates the in-cylinder gas temperature when the closing timing of the intake valve 5 is normal (when no condensed water is generated).

As a result, the combustion stability of the internal combustion engine 1 is ensured by promoting the vaporization of the condensed water, and damage to parts due to incomplete combustion such as misfiring can be avoided. In addition, the internal combustion engine 1 can suppress the progress of deterioration such as corrosion in the cylinder due to the decrease in the amount of condensed water.

In other words, the internal combustion engine 1 retards the closing timing of the intake valve 5 to increase the amount of gas blown back to the intake port during the intake stroke and raise the temperature in the cylinder, thereby increasing pump loss and internal EGR. The condensed water can be vaporized without deteriorating anti-knock performance due to

In the internal combustion engine 1, the opening degree of the EGR valve 34 is controlled so that the EGR rate corresponds to the operating state. lower than the required EGR rate.

The internal combustion engine 1 can reduce the water content in the gas by reducing the EGR rate. That is, the internal combustion engine 1 reduces the amount of condensed water generated by reducing the EGR rate, thereby improving combustion stability. In addition, the internal combustion engine 1 can suppress the progress of deterioration such as corrosion in the cylinder due to the decrease in the amount of condensed water.

FIG. 3 is a flow chart showing an example of the control flow of the internal combustion engine 1 of the embodiment described above.

In step S1, it is determined whether or not it is time to set the closing timing (IVC) of the intake valve 5 and the EGR rate by starting the internal combustion engine 1 . That is, in step S1, if it is time to set the closing timing of the intake valve 5 and the EGR rate associated with the start of the internal combustion engine 1, the process proceeds to step S2. If it is determined in step S1 that the internal combustion engine 1 is already in operation, the process proceeds to step S4.

In step S2, the closing timing (IVC) of the intake valve 5 is set to the normal closing timing. That is, the valve timing of the intake valve 5 is set to the normal valve timing. In step S3, the EGR rate is set to the normal EGR rate (normal EGR rate).

In step S4, it is determined whether or not condensed water is generated. That is, in step S4, when generation of condensed water is detected, the process proceeds to step S5. If generation of condensed water is not detected in step S4, the process proceeds to step S7.

In step S4, for example, when the condensed water estimated value calculated from the detection signal of the humidity sensor 49 is equal to or greater than a predetermined threshold value W, it is determined that condensed water is generated.

In step S5, for example, the closing timing of the intake valve 5 is retarded so that condensed water does not occur.

Specifically, for example, the closing timing of the intake valve 5 is retarded by a predetermined amount A1 from the closing timing of the intake valve 5 set in the previous routine. The predetermined amount A1 is set, for example, with a certain margin so that condensed water does not occur. Alternatively, the closing timing (first closing timing) of the intake valve 5 at which no condensed water is reliably generated is determined in advance by experiments or the like, and in step S5, the closing timing of the intake valve 5 is set to this first closing timing. The angle may be retarded so that

In step S6, for example, the EGR rate is decreased to ensure that no condensed water is generated.

Specifically, for example, the EGR rate of the internal combustion engine 1 is decreased by a predetermined amount B1 from the EGR rate set in the immediately preceding routine. The predetermined amount B1 is set, for example, with a certain margin so that condensed water does not occur. Alternatively, an EGR rate (first EGR rate) of the internal combustion engine 1 that does not reliably generate condensed water is obtained in advance by experiments or the like, and in step S6, the EGR rate of the internal combustion engine 1 is reduced to the first EGR rate. You may do so.

In step S7, the closing timing of the intake valve 5 is advanced. Specifically, for example, the closing timing of the intake valve 5 is advanced by a predetermined amount A2 from the closing timing of the intake valve 5 set in the previous routine. The predetermined amount A2 is set to a smaller value than the predetermined amount A1.

If the internal combustion engine 1 advances the closing timing of the intake valve 5 in this way (step S7), it becomes possible to advance the closing timing of the intake valve 5 within a range in which no condensed water is generated, and the fuel efficiency is improved. It can improve performance.

At step S8, the EGR rate of the internal combustion engine 1 is increased. Specifically, for example, the EGR rate of the internal combustion engine 1 is increased by a predetermined amount B2 from the EGR rate set in the previous routine. The predetermined amount B2 is set to a value smaller than the predetermined amount B1.

By increasing the EGR rate of the internal combustion engine 1 in this way (step S8), it becomes possible to increase the EGR rate within a range in which condensed water is not generated, and the fuel efficiency can be improved.

When the generation of condensed water is detected in step S4, the closing timing of the intake valve 5 is retarded by a predetermined amount until no condensed water is generated, or the EGR rate is delayed until no condensed water is generated. It may be decreased by a fixed amount.

In short, the internal combustion engine 1 of the present embodiment can improve the combustion resistance during lean combustion in which EGR gas is introduced by performing combustion control adapted to the generation of condensed water.

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, the control unit 9 may retard only the closing timing of the intake valve 5 without reducing the EGR rate when it detects the generation of condensed water.

Also, detection of condensed water can be estimated without using the humidity sensor 49 . For example, detection of condensed water can also be estimated from detection values (detection signals) of a knock sensor that detects the presence or absence of knocking, the intake air temperature sensor 48, and the like. For example, if the level (degree) of vibration generated in the internal combustion engine 1 is greater than the original level (degree) corresponding to the intake air temperature, it is determined that the combustion is unstable due to the generation of condensed water. , it may be estimated that condensed water is generated.

It should be noted that the above-described embodiments relate to a method of controlling an internal combustion engine and a control system for an internal combustion engine.

Reference Signs List 1 Internal combustion engine 3 Intake passage 4 Exhaust passage 5 Intake valve 6 Combustion chamber 7 Exhaust valve 9 Control unit 41 Intake side variable valve mechanism 42 Intake side camshaft 43 Crankshaft 45 Intake side Camshaft position sensor 46 Crank angle sensor 47 Accelerator opening sensor 48 Intake air temperature sensor 49 Humidity sensor

Claims (6)

a valve timing changing mechanism capable of changing the valve timing of the intake valve;
a condensed water detector capable of detecting condensed water generated upstream of the combustion chamber;
When the condensed water detection unit detects condensed water, the valve timing of the intake valve is changed to delay the closing timing of the intake valve so that the opening period of the intake valve straddles the bottom dead center. A control method for an internal combustion engine. 2. The method of controlling an internal combustion engine according to claim 1 , wherein the closing timing of the intake valve is set near the bottom dead center when no condensed water is detected. having an exhaust gas recirculation passage for recirculating part of the exhaust gas as EGR gas to the intake passage;
3. The control method for an internal combustion engine according to claim 1, wherein the EGR rate is reduced when generation of condensed water is detected on the upstream side of the combustion chamber. The control method for an internal combustion engine according to any one of claims 1 to 3 , characterized in that the closing timing of the intake valve is advanced when generation of condensed water is not detected on the upstream side of the combustion chamber. 5. The method of controlling an internal combustion engine according to claim 1 , wherein the EGR rate is increased when generation of condensed water is not detected on the upstream side of the combustion chamber. a valve timing changing mechanism capable of changing the valve timing of the intake valve;
a condensed water detector that detects condensed water generated upstream of the combustion chamber;
When the condensed water detection unit detects condensed water, valve timing control for retarding the closing timing of the intake valve by changing the valve timing of the intake valve so that the opening period of the intake valve straddles the bottom dead center. and a control device for an internal combustion engine.

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