JP2007016710A - Valve control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce exhaust emission at starting an engine without increasing the size of a structure. <P>SOLUTION: During a time from beginning the start of the engine 2 to finishing the discrimination of a cylinder, an exhaust valve 23 whose opening is stopped is held in a closed condition. When the exhaust valve 23 is in the closed condition and a crank angle is in a predetermined range including a compression top dead center or an exhaust top dead center, an intake valve 22 is opened to introduce compressed air from the cylinder into an intake port 24. The internal of the intake port 24 is heated for temperature rise with the compressed air introduced before fuel is injected into the intake port 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a valve operating control system for an internal combustion engine with improved exhaust emission at the start of the internal combustion engine.

Conventionally, as this type of technology, for example, those described in the following documents are known (see Patent Document 1). In the technique described in this document, a method of supplying assist air to an injector for supplying and supplying fuel is employed. The structure for supplying the assist air is provided with a cold-time assist air introduction path that opens to the atmosphere inside the collection body provided so as to cover the periphery of the exhaust passage of the internal combustion engine, and through the cold-time assist air introduction path. The atmosphere heated by the exhaust heat around the exhaust passage is supplied to the injector as assist air when cold. Thereby, since the fuel is atomized and heated at the same time, vaporization of the fuel is promoted and generation of HC and CO is suppressed.
Japanese Patent Laid-Open No. 10-77933

  In the above-described starting method of the internal combustion engine when cold, a supply path for supplying heated atmospheric assist air to the injector is required. For this reason, the layout design of the engine is constrained or the configuration becomes large.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a valve operating control system for an internal combustion engine that reduces exhaust emission at the time of engine start without causing an increase in size of the configuration. There is to do.

  In order to achieve the above object, the invention according to claim 1 is an opening / closing timing of an intake valve that controls the introduction of the fuel injected into the intake port into the cylinder and an exhaust valve that controls the exhaust of the combustion gas in the cylinder. In the valve control system for an internal combustion engine that arbitrarily controls the engine independently, for a predetermined period after the start of the internal combustion engine, the exhaust valve is stopped and the exhaust valve is closed. Exhaust valve opening / closing control means to be held, and for a predetermined period after the start of the internal combustion engine, the exhaust valve is in a closed state and a crank angle includes a compression top dead center or an exhaust top dead center And an intake valve opening / closing control means for opening the intake valve and introducing the compressed air in the cylinder into the intake port.

  According to the first aspect of the present invention, the intake port can be heated and heated before the fuel is injected, the vaporization of the sprayed fuel is promoted, and the exhaust emission at the start of the engine is reduced. Can do.

  According to a second aspect of the present invention, in the first aspect of the present invention, the predetermined period is a period until the cylinder discrimination process ends after the internal combustion engine is started.

  According to the second aspect of the present invention, fuel can be injected while the intake port is heated and heated.

  According to a third aspect of the present invention, in the first aspect of the present invention, when the exhaust valve is in a closed state and the intake valve is opened, the intake port is initially connected to the intake port after the start of the internal combustion engine. Fuel injection is performed.

  According to the third aspect of the present invention, the first atomized fuel can be collided with the compressed air returned from the inside of the cylinder, and atomization of the atomized fuel can be promoted.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a valve operating control system for an internal combustion engine according to Embodiment 1 of the present invention. The system according to the first embodiment shown in FIG. 1 includes an engine ECU (electronic control unit) 1, and the operation of the engine 2 is controlled by the engine ECU 1.

  In the engine 2, each cylinder 20 is provided with an ignition plug 21, an intake valve 22 and an exhaust valve 23, and both valves are configured by electromagnetically driven valves that are controlled to open and close by an electromagnetic force obtained by a linear solenoid or the like. The intake valve 22 controls opening and closing between the intake port 24 and the combustion chamber of the cylinder 20, and the intake port 24 is provided with an injector 25 in the vicinity of the intake valve 22 for injecting fuel toward the combustion chamber. The intake port 24 is provided with a port temperature sensor 26 that detects the temperature in the intake port 24 in the vicinity of the intake valve 22. The engine 2 is provided with a crank angle sensor 27 that detects the angle of the crankshaft on the crankshaft.

  The engine ECU 1 functions as a control center for controlling the operation of the engine 2, and is equipped with resources such as a CPU, a storage device, and an input / output device necessary for a computer that controls various operation processes based on a program, for example, a microcomputer or the like It is realized by. The engine ECU 1 starts operation control of the engine 2 based on the start signal of the engine 2 given from the ignition switch 3, the sensor signal output from the port temperature sensor 26, the crank angle sensor 27, and the rotation speed of the engine 2. A signal from each sensor (not shown) required for operation of the engine 2 including a sensor for detecting the throttle valve and a sensor for detecting the opening of the throttle valve is read, and the read signal and control logic (internally stored in advance) Based on the program), commands are sent to the spark plug 21 of the engine 2, the intake valve 22, the exhaust valve 23, the injector 25, and each component necessary for the operation of the engine 2, and in the first to fourth embodiments described below Supervises all the operations necessary for the operation of the engine 2, including the operations at the time of engine start Management to control.

  The engine ECU 1 gives an intake valve drive control signal to the electromagnetically driven valve of the intake valve 22, and controls the opening / closing timing of the intake valve 22 by this intake valve drive control signal. The engine ECU 1 gives an exhaust valve drive control signal to the electromagnetically driven valve of the exhaust valve 23, and controls the opening / closing timing of the exhaust valve 23 by this exhaust valve drive control signal. That is, in the engine 2, the opening / closing timing of the exhaust valve 23 is controlled by the valve timing variable mechanism provided in the engine ECU 1 and the engine 2. The engine ECU 1 gives an ignition control signal to the ignition plug 21 and controls ignition of the ignition plug 21 by this ignition control signal. The engine ECU 1 gives a fuel injection control signal to the injector 25, and controls the fuel injection timing of the injector 25 by this fuel injection control signal.

  The engine ECU 1 inputs the port temperature signal obtained by the port temperature sensor 26 and detects the temperature of the intake port 24 based on the port temperature signal. The engine ECU 1 inputs the crank angle signal obtained by the crank angle sensor 27, and performs cylinder discrimination processing for each cylinder 20 based on the crank angle signal.

  In such an engine ECU 1, the starting operation of the engine 2 is controlled according to the procedure shown in the flowchart of FIG. In FIG. 2, first, when a start signal is given from the ignition switch 3 to the engine ECU 1, the engine 2 starts cranking (step S21). At the same time, the opening of the exhaust valve 23 is prohibited and stopped by the exhaust valve drive control signal, and the exhaust valve 23 is held closed (step S22).

  On the other hand, when the crank angle detected based on the crank angle signal obtained by the crank angle sensor 27 is within a predetermined range including the compression top dead center or the exhaust top dead center while the exhaust valve 23 is in the closed state. The intake valve 22 is controlled to open and close based on the intake valve drive control signal.

  Subsequently, based on the crank angle obtained by the crank angle sensor 27, cylinder discrimination processing for each cylinder 20 is performed (step S23). When this cylinder discrimination processing is completed, the prohibition of opening of the exhaust valve 23 is released, and the exhaust valve 23 is returned to normal opening / closing drive control (step S24). Thereafter, fuel is injected by the injector 25 at a predetermined timing, and then the ignition plug 21 is ignited to start combustion (step S25).

  Thus, during the predetermined period when the engine is started, that is, during the cranking period until the cylinder discrimination is finished, the opening of the exhaust valve 23 is stopped and the exhaust valve 23 is held in the closed state. By controlling the opening of the intake valve 22 when air is compressed in the cylinder in conjunction with the air, the air compressed in the cylinder during the cranking period is not exhausted via the exhaust valve 23, and the valve is opened. The intake port 24 is introduced through the intake valve 22. As a result, the inside of the intake port 24 is heated by the high-temperature air heated by the compression, and as shown in the timing chart of FIG. 3, the intake air at the time of cylinder discrimination is compared with the conventional case where the opening of the exhaust valve 23 is not prohibited. The temperature in the port 24 can be increased. As a result, fuel can be injected while the temperature in the intake port 24 is high, and vaporization of the injected fuel can be promoted. Further, since the temperature of the wall surface of the intake port is also increased, the wall flow of fuel flowing through the intake port wall surface can be reduced. As a result, it is possible to reduce the amount of HC discharged when starting the engine, particularly when starting at a low temperature.

  In addition, since the atomized fuel can be sufficiently vaporized, the startability of the engine 2, particularly the startability at a low temperature can be improved.

  Next, a second embodiment of the present invention will be described. In the first embodiment, the exhaust valve 23 is returned to the normal operation opening / closing control at the time of the first fuel injection after the cylinder discrimination. The feature of the second embodiment is shown in the timing chart of FIG. Thus, at the time of the first fuel injection after cylinder discrimination, the exhaust valve 23 is held in the closed state in the same manner as in the cranking period before cylinder discrimination, and the others are the same as in the first embodiment. It is.

  By adopting such a control method, since the exhaust valve 23 is closed at the first fuel injection, the compressed air during the cranking period is not exhausted but is taken in through the intake valve 22 opened. Introduced into port 24. As a result, the first injected fuel collides with the compressed air that has returned to the intake port 24, and atomization of the sprayed fuel can be promoted.

  As described above, in the second embodiment, vaporization of the sprayed fuel is further promoted as compared with the first embodiment, and the same effect as in the first embodiment can be obtained.

  Next, Embodiment 3 of the present invention will be described with reference to the flowchart of FIG. 5 showing the control procedure of the starting operation of the engine 2. The feature of the third embodiment is that the first embodiment is based on the voltage (charge amount) of a battery (not shown) as a power source when starting the engine 2 and the temperature in the intake port 24. The other control procedure is the same as in the first embodiment.

  In FIG. 5, first, when a start signal is given from the ignition switch 3 to the engine ECU 1, the engine 2 starts cranking (step S51). At the same time, the opening of the exhaust valve 23 is prohibited by the exhaust valve drive control signal, and the exhaust valve 23 is kept closed (step S52).

  On the other hand, when the crank angle detected based on the crank angle signal obtained by the crank angle sensor 27 is within a predetermined range including the compression top dead center or the exhaust top dead center while the exhaust valve 23 is in the closed state. The intake valve 22 is controlled to open and close based on the intake valve drive control signal.

  Thereafter, cylinder discrimination processing for each cylinder 20 is performed based on the crank angle obtained by the crank angle sensor 27 (step S53). When this cylinder discrimination processing is completed, it is judged by the engine ECU 1 whether or not the battery voltage is equal to or higher than a predetermined voltage X (v) set in advance (step S54). Here, the predetermined voltage X (v) is set to a voltage of, for example, about 90% of the normal battery voltage. As a result of the determination, if the battery voltage is not equal to or higher than the predetermined voltage X, a process of step S56 described later is executed. If the battery voltage is equal to or higher than the predetermined voltage X, the port temperature obtained by the port temperature sensor 26 is subsequently obtained. It is determined whether or not the port temperature in the intake port 24 detected based on the signal is equal to or higher than a predetermined temperature Y (° C.) set in advance (step S55). Here, the predetermined temperature Y (° C.) is set to, for example, about 35 ° C. to 40 ° C. at which fuel vaporization starts.

  As a result of the determination, if the port temperature is not equal to or higher than the predetermined temperature Y, it is determined that the vaporization of the sprayed fuel is not promoted even if the fuel is injected, and the process returns to the previous step S52. The release prohibition of the exhaust valve 23 is released, and the exhaust valve 23 is returned to the normal opening / closing drive control (step S56). Thereafter, fuel is injected by the injector 25 at a predetermined timing, and then the ignition plug 21 is ignited to start combustion (step S57).

  In the third embodiment, as shown in the timing chart of FIG. 6, after determining that the charge amount of the battery is sufficient and the temperature in the intake port 24 has reached the temperature at which fuel vaporization is promoted, As a result, the vaporization of the sprayed fuel is surely promoted in the intake port 24 without causing the problem that the charge amount of the battery becomes insufficient by performing the operation of heating and heating the intake port 24. Therefore, the exhaust emission can be further reduced and the startability can be improved as compared with the first embodiment.

  Although the temperature in the intake port 24 is detected by the port temperature sensor 26 installed in the intake port 24, the temperature of the cooling water of the engine 2 or the temperature of the engine oil is detected and based on the detected temperature. The temperature in the intake port 24 may be estimated.

  Next, a fourth embodiment of the present invention will be described. The feature of the fourth embodiment is that the second embodiment is combined with the third embodiment, and the others are the same as the first embodiment. That is, as shown in the timing chart of FIG. 7, when the temperature in the intake port 24 becomes equal to or higher than a predetermined temperature Y (° C.), the first fuel injection is performed with the exhaust valve 23 closed. Yes.

  In the fourth embodiment, the effects obtained in the second and third embodiments can be obtained.

Further, technical ideas other than the claims that can be grasped from the above-described embodiments will be described below together with effects.
(A) In the valve operating control system for an internal combustion engine according to claim 1 or 3,
Temperature detecting means for detecting or estimating the temperature in the intake port;
A valve operating control system for an internal combustion engine, wherein fuel is injected into the intake port after the temperature in the intake port detected or estimated by the temperature determination means becomes equal to or higher than a predetermined temperature.

  According to the configuration described in the above item (A), it is possible to inject fuel in a state where vaporized fuel can be sufficiently vaporized, and in addition to reducing exhaust emission, it is possible to improve engine startability.

1 is a diagram showing a configuration of a valve operating control system for an internal combustion engine according to Embodiment 1 of the present invention. It is a flowchart which shows the procedure of the processing operation which concerns on Example 1 of this invention. It is a timing chart which concerns on Example 1 of this invention. It is a timing chart which concerns on Example 2 of this invention. It is a flowchart which shows the procedure of the processing operation which concerns on Example 3 of this invention. It is a timing chart which concerns on Example 3 of this invention. It is a timing chart which concerns on Example 4 of this invention.

Explanation of symbols

1 ... Engine ECU
DESCRIPTION OF SYMBOLS 2 ... Engine 3 ... Ignition switch 20 ... Cylinder 21 ... Spark plug 22 ... Intake valve 23 ... Exhaust valve 24 ... Intake port 25 ... Injector 26 ... Port temperature sensor 27 ... Crank angle sensor

Claims (3)

In a valve operating control system for an internal combustion engine that arbitrarily controls the opening and closing timing of an intake valve that controls the introduction of fuel injected into an intake port into a cylinder and an exhaust valve that controls exhaust gas from the cylinder. ,
Exhaust valve opening / closing control means for stopping opening of the exhaust valve and holding the exhaust valve in a closed state for a predetermined period after the start of the internal combustion engine;
When the exhaust valve is closed and the crank angle is in a predetermined range including a compression top dead center or an exhaust top dead center for a predetermined period after the start of the internal combustion engine is started, the intake air And an intake valve opening / closing control means for opening the valve and introducing the compressed air in the cylinder into the intake port. 2. The valve operating control system for an internal combustion engine according to claim 1, wherein the predetermined period is a period until the cylinder discrimination process is finished after the internal combustion engine is started. 2. The internal combustion engine according to claim 1, wherein when the exhaust valve is in a closed state and the intake valve is opened, the first fuel injection after the start of the internal combustion engine is performed to the intake port. Valve control system.

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