JP2005337110A - Internal combustion engine - Google Patents

Abstract

To improve startability of an internal combustion engine.
An internal combustion engine is an internal combustion engine that takes out power from a crankshaft by burning an air-fuel mixture formed in a cylinder. The internal combustion engine 10 includes an intake valve 30 and an exhaust valve 40 provided for each cylinder, and a variable valve timing mechanism (VVT) 46 capable of adjusting the opening / closing timing of the exhaust valve 40. The ECU 100 that controls the internal combustion engine 10 controls the exhaust side VVT 46 to retard the opening timing of the first exhaust valve that is changed after the first combustion in the first explosion cylinder when the internal combustion engine 10 is automatically started. As a result, the combustion pressure of the first explosion can be efficiently extracted as power and the startability of the internal combustion engine 10 can be improved.
[Selection] Figure 4

Description

  The present invention relates to an internal combustion engine, and more particularly to improving the startability of an internal combustion engine.

  In order to reduce fuel consumption and air pollutant emissions, control for stopping and starting an internal combustion engine has been put into practical use regardless of the driver's intention. For example, when the vehicle temporarily stops during driving, the internal combustion engine is automatically stopped, and the internal combustion engine is automatically started before starting running (so-called idling stop). Further, in a hybrid vehicle including both a motor and an internal combustion engine as power, control for stopping and starting the internal combustion engine is performed even during traveling according to the traveling mode.

  In this way, in a vehicle that automatically stops and starts the internal combustion engine regardless of the driver's intention, the driver is likely to feel uncomfortable due to vibration and noise at the time of automatic start, and the technology to start the internal combustion engine quickly and smoothly Is more important than conventional vehicles.

  As a valve timing control technique at the start of the internal combustion engine, in order to realize stable ignition and combustion, a technique for optimally controlling the closing timing of the intake valve (for example, Patent Document 1) or an air pollutant (for example, unresolved) A technique (for example, Patent Document 2) that optimally controls the closing timing of the exhaust valve for reducing the fuel HC) is known.

JP 2001-140663 A JP 2003-120348 A JP 2001-289086 A JP 2001-342876 A JP 2003-328789 A

  However, in the above technique, the opening timing of the exhaust valve at the start of the internal combustion engine is not considered, and the startability of the internal combustion engine may not be sufficient.

  The present invention has been made to solve the above-described problems, and an object thereof is to improve the startability of an internal combustion engine.

  In order to solve at least a part of the above problems, a first aspect of the present invention provides an internal combustion engine that burns an air-fuel mixture formed in a cylinder and extracts power from a crankshaft. An internal combustion engine according to a first aspect of the present invention includes an intake valve and an exhaust valve provided for each cylinder, a variable valve timing mechanism capable of adjusting a timing at which the exhaust valve opens and closes, and the variable valve timing mechanism. Control means for controlling, in a first-explosion cylinder in which the air-fuel mixture is first burned when the internal combustion engine is started, control means for retarding the opening timing of the first exhaust valve that shifts after the first combustion. Features.

  According to the internal combustion engine of the first aspect of the present invention, in the first explosion cylinder that controls the variable valve timing mechanism of the exhaust valve to burn the air-fuel mixture first when the internal combustion engine is started, the first after the first combustion is performed. The opening timing of the exhaust valve is retarded. As a result, the combustion pressure can be prevented from being released from the exhaust valve early in the expansion stroke, and the combustion pressure of the first explosion cylinder can be efficiently extracted to the crankshaft as power. Therefore, the internal combustion engine can be started quickly.

  In the internal combustion engine according to the first aspect of the present invention, when the valve opening timing of the exhaust valve that has been retarded by the variable valve timing mechanism is before the bottom dead center in the expansion stroke, the control means May delay the opening timing of the first exhaust valve the most. In such a case, in an internal combustion engine having a variable valve timing mechanism in which the opening timing of the exhaust valve at the most retarded angle is before the bottom dead center of the expansion stroke, the timing at which the combustion pressure of the first explosion cylinder is released from the exhaust valve Can be delayed most. As a result, the combustion pressure of the first explosion cylinder can be efficiently taken out to the crankshaft as power.

  In the internal combustion engine according to the first aspect of the present invention, when the variable valve timing mechanism can retard the opening timing of the exhaust valve until after the bottom dead center in the expansion stroke, the control means includes: The opening timing of the first exhaust valve may be retarded to the bottom dead center. In such a case, by setting the opening timing of the exhaust valve of the first explosion cylinder to the bottom dead center of the expansion stroke, the combustion pressure of the first explosion cylinder can be extracted to the crankshaft most efficiently.

  In the internal combustion engine according to the first aspect of the present invention, after the opening of the first exhaust valve, the control means advances the valve opening timing of each cylinder from the valve opening timing of the first exhaust valve. You may let them. As a result of effectively taking out the combustion pressure as power by retarding the opening timing of the exhaust valve, a phenomenon in which the crank angular speed (the number of revolutions) rapidly increases (so-called blow-up) may occur. After the opening of the exhaust valve of the first explosion cylinder, the opening timing of the exhaust valve is advanced, so that the subsequent removal of the combustion pressure can be suppressed and so-called blow-up can be prevented.

  In the internal combustion engine according to the first aspect of the present invention, the advance amount by the control means may be determined so that an overlap period in which the intake valve and the exhaust valve are simultaneously opened does not occur. When the internal combustion engine is started, if there is an overlap period, the exhaust gas may flow back into the cylinder and the combustion may become unstable. By advancing so that the overlap period does not occur during the advance angle control, in addition to preventing the blow-up, in-cylinder backflow of exhaust gas can be prevented and combustion can be stabilized.

  The internal combustion engine according to the first aspect of the present invention further includes detection means for detecting a crank angular speed that is an angular speed of the crankshaft, and an advance amount by the control means is in accordance with the detected crank angular speed. It may be determined. In such a case, since an appropriate advance amount is determined in accordance with the so-called blow-up degree, the blow-up can be effectively prevented.

  The internal combustion engine according to the first aspect of the present invention further includes prediction means for predicting a stop-time compression stroke cylinder in a compression stroke at the time of stop before the stop of the internal combustion engine, and the prediction at the time of stop of the internal combustion engine. A fuel filling means for bringing the stopped compression stroke cylinder into a state of being filled with fuel, and an electric motor for rotationally driving the crankshaft, and the crankshaft is rotated to a compression top dead center in the stop compression stroke cylinder. Then, the stop-time compression stroke cylinder may be started as the initial explosion cylinder. A fuel injection valve that directly injects fuel into the cylinder; a detecting means that detects a compression stroke cylinder at a stop in a compression stroke when the internal combustion engine is stopped; and the fuel injection valve that controls the detection. An injection valve control means for filling the stop-time compression stroke cylinder with fuel, and an electric motor for rotationally driving the crankshaft, after rotating the crankshaft to the compression top dead center in the stop-time compression stroke cylinder The compression stroke cylinder at the time of stop may be started as the initial explosion cylinder.

  In such a case, since the cylinder in the compression stroke is made to be filled with fuel while the internal combustion engine is stopped, at the start of the internal combustion engine, only by rotating the crankshaft to the compression top dead center of this cylinder, The first combustion can start. As a result, the internal combustion engine can be started more quickly.

  The internal combustion engine according to the first aspect of the present invention further includes prediction means for predicting a stop-time expansion stroke cylinder in an expansion stroke at the time of stop before the stop of the internal combustion engine, and the prediction at the time of stop of the internal combustion engine. And a fuel filling means for bringing the stopped expansion stroke cylinder into a state filled with fuel, and the stop expansion stroke cylinder may be started as the initial explosion cylinder. A fuel injection valve for directly injecting fuel into the cylinder; a detecting means for detecting a stop expansion stroke cylinder in an expansion stroke when the internal combustion engine is stopped; and the fuel injection valve for controlling the detection. The stop-time expansion stroke cylinder may be provided with an injection valve control means for filling the fuel, and the stop-time expansion stroke cylinder may be started as the initial explosion cylinder.

  In such a case, the cylinder in the expansion stroke is brought into a state filled with fuel while the internal combustion engine is stopped, so that the air-fuel mixture in the cylinder can be burned immediately when the internal combustion engine is started. As a result, the internal combustion engine can be started more quickly. Further, at the time of starting, power (such as an electric motor) that rotationally drives the crankshaft other than the combustion pressure can be made unnecessary.

  According to a second aspect of the present invention, an exhaust valve control for an internal combustion engine having a variable valve timing mechanism capable of adjusting a timing at which the exhaust valve opens and closes, and combusting an air-fuel mixture formed in the cylinder to extract power from a crankshaft. Provide a method. The exhaust valve control method according to the second aspect of the present invention retards the opening timing of the first exhaust valve to be changed after the first combustion in the first explosion cylinder in which the air-fuel mixture burns first when the internal combustion engine is started. It is characterized by that.

  According to the exhaust valve control method according to the second aspect of the present invention, it is possible to obtain the same effects as those of the internal combustion engine according to the first aspect of the present invention. The exhaust valve control method according to the second aspect of the present invention can be realized in various aspects in the same manner as the four-cycle internal combustion engine according to the first aspect of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an internal combustion engine according to the present invention will be described based on examples with reference to the drawings.

A. Example and configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration around an internal combustion engine according to an embodiment of the present invention. The internal combustion engine 10 according to the present embodiment is a so-called four-cylinder gasoline engine.

  The internal combustion engine 10 according to the present embodiment includes a cylinder block 20 having four cylinders # 1 to # 4 inside, a cylinder head 22 disposed on the upper surface of the cylinder block 20, and a sliding motion in each cylinder up and down. A piston (not shown) that is inscribed so as to move, and a control device (ECU) 100 that controls the entire engine 10 are provided. Further, around the internal combustion engine 10, an electric motor 200, an inverter 300, and a battery 400 are provided.

  The piston is connected to the crankshaft 60 via a connecting rod (not shown). A crank angle sensor 102 is attached in the vicinity of the crankshaft 60, whereby the engine rotational speed Ne, the crank angle θcr, and the crank angular speed Vθ can be detected.

  The cylinder head 22 has an intake port and an exhaust port (not shown) for each cylinder. A branch end of an intake pipe 12 is connected to each intake port, and air is supplied to each cylinder via the intake pipe 12. In the intake pipe 12, a throttle valve 70, an air cleaner 64, and an intake pressure sensor 110 are arranged. The amount of air supplied to each cylinder can be adjusted by adjusting the opening of the throttle valve 70 by the electric actuator 72, and the intake pressure Pin 110 can be detected by the intake pressure sensor 110. A branch end of the exhaust pipe 16 is connected to each exhaust port, and combustion gas is discharged from each cylinder through the exhaust pipe 16. A catalyst device 80 is disposed in the exhaust pipe 16.

  In the cylinder head 22, for each cylinder, an intake valve 30 for opening and closing an intake port, an exhaust valve 40 for opening and closing an exhaust port, an intake side camshaft 34 for driving the intake valve 30, and an exhaust valve 40 are driven. An exhaust side camshaft 44, a fuel injection valve 50 for injecting fuel into the intake port, and a spark plug 25 for spark ignition are disposed.

  Here, the valve mechanism of the exhaust valve 40 will be described. The exhaust-side camshaft 44 is configured to be rotationally driven when the rotation of the crankshaft 60 is transmitted through a chain or the like. The exhaust side camshaft 44 is formed at a position where the exhaust side cam 42 comes into contact with each exhaust valve 40. When the exhaust side camshaft 44 rotates together with the exhaust side cam 42, the exhaust valve 40 opens and closes. Driven. Therefore, the exhaust valve 40 can be driven to open and close at an appropriate timing in accordance with the rotation of the crankshaft 60 by assembling the crankshaft 60 and the exhaust camshaft 44 so that the phases are appropriate.

  The phases of the exhaust camshaft 44 and the crankshaft 60 can be continuously changed within a predetermined changeable range by an exhaust side variable valve timing mechanism (hereinafter referred to as exhaust side VVT) 46. In the present embodiment, the changeable range of the exhaust side VVT 46 is the bottom dead center (the most retarded angle) of the expansion stroke from 60 degrees (at the most advanced angle) before the bottom dead center of the expansion stroke, as viewed at the opening timing of the exhaust valve 40. Time). The exhaust side VVT 46 uses a known VVT configuration. As the VVT, for example, a mechanism for changing the phase between the camshaft and the crankshaft by a hydraulic mechanism or an electric mechanism such as a step motor or an electromagnetic solenoid is known, but detailed description thereof is omitted.

  Similar to the valve mechanism of the exhaust valve 40, the valve mechanism of the intake valve 30 is composed of an intake side camshaft 34 having an intake side cam 32 and an intake side VVT 36. The exhaust valve 40 is a crankshaft. The rotation of 60 is transmitted to the intake side camshaft 34 to be driven to open and close. In the present embodiment, the changeable range of the intake side VVT 36 is from 35 degrees before intake top dead center (at the most advanced angle) to 5 degrees before intake top dead center (at the most retarded angle) when the intake valve 30 is opened. ).

  Cam angle sensors 106 and 108 are mounted in the vicinity of the intake side camshaft 34 and the exhaust side camshaft 44, respectively, whereby the intake side cam angle θincam and the exhaust side cam angle θexcam can be detected. .

  The electric motor 200 is configured to be able to transmit power to the crankshaft 60 via the V-ribbed belt 204. That is, a motor pulley 202 is attached to the power output shaft of the electric motor 200, and a crank pulley 62 is attached to the crankshaft 60. A V-ribbed belt 204 is mounted on the motor pulley 202 and the crank pulley 62. The electric motor 200 functions as a power source that drives the crankshaft 60 when the internal combustion engine 10 is started, and functions as a generator that is driven by the crankshaft 60 and generates electric power when the internal combustion engine 10 is operated. The electric motor 200 is electrically connected to the inverter 300 and is driven and controlled by the inverter 300 based on a command from the ECU 100.

  Inverter 300 is also electrically connected to battery 400. The battery 400 functions as a power source for driving the electric motor 200 when the internal combustion engine 10 is started, and stores the electric power generated by the electric motor 200 when the internal combustion engine 10 is operated.

  The ECU 100 is composed of a known microcomputer. The ECU 100 acquires electrical signals from the sensors (the crank angle sensor 102, the accelerator opening sensor 104, the cam angle sensors 106 and 108, and the intake pressure sensor 110) to obtain various information (engine rotational speed Ne, crank angle θcr, Crank angular velocity Vθ, accelerator opening θac, intake side and exhaust side cam angles θincam, θexcam, and intake pressure Pin) are detected.

  The ECU 100 controls the intake side and exhaust side VVTs 36, 46, the fuel injection valve 50, the throttle valve 70, the spark plug 25, the inverter 300, and the like based on the detected information, thereby controlling the ignition timing and the fuel injection amount. Control, fuel injection timing control, intake air amount control, opening / closing timing control (valve timing control) of the intake valve 30 and the exhaust valve 40 are executed, and the internal combustion engine 10 is operated. In the following description, the valve timing control, which is a characteristic part of the present embodiment, will be mainly described, and control that is not a characteristic part will be appropriately omitted.

Operation:
The operation (control) of the internal combustion engine 10 according to the first embodiment will be described with reference to FIGS. FIG. 2 is a map showing an example of a correspondence relationship between the operating conditions of the internal combustion engine 10 according to the present embodiment and the opening / closing timings of the intake and exhaust valves (hereinafter also referred to as valve timings). In FIG. 2, TDC indicates the timing at which the piston is at the top dead center position, and BDC indicates the timing at which the piston is at the bottom dead center position. Further, IN indicates a valve opening period of the intake valve 30, and EX indicates a valve opening period of the exhaust valve 40. Here, four valve timings A to D are illustrated according to the engine speed Ne and the required load. A is the valve timing at low temperature, light load, and idling. B is a high load low and medium rotation region, C is a medium load region, and D is a valve timing in a high load and high rotation region.

  The internal combustion engine 10 is operated based on the map shown in FIG. 2 (hereinafter referred to as normal operation) during idling and while the vehicle is traveling. That is, ECU 100 stores a map as shown in FIG. 2, and based on detected engine rotation speed Ne and accelerator opening θac (required load), ECU 100 refers to the map to determine intake side VVT 36 and exhaust side VVT 46. Control (hereinafter referred to as normal operation control). As a result, the opening / closing timing of the intake valve 30 and the exhaust valve 40 is advanced or retarded, and the internal combustion engine 10 is operated at an appropriate valve timing according to the running state. Here, the advance angle refers to advancing the opening / closing timing of the intake valve 30 or the exhaust valve 40, and the retard angle refers to delaying the opening / closing timing of the intake valve 30 or the exhaust valve 40. Further, the amount of change in advance and retard expressed in terms of crank angle is referred to as advance amount and retard amount, respectively.

  On the other hand, the internal combustion engine 10 is subjected to automatic stop / start control for realizing so-called idling stop. The ECU 100 controls the internal combustion engine 10 while switching between normal operation control and automatic stop / start control in accordance with the state of the vehicle.

  FIG. 3 is a flowchart showing a control processing routine of the internal combustion engine 10 at the time of idling stop. FIG. 4 is an explanatory diagram schematically showing the opening / closing timing of the intake valve 30 and the exhaust valve 40 with respect to the crank angle when the idling stop is performed. For convenience of explanation, from when the vehicle equipped with the internal combustion engine 10 is temporarily stopped during operation and the internal combustion engine 10 is in an idling state, until the internal combustion engine 10 is automatically stopped and automatically started, and then returned to the idling state again. This will be explained step by step.

  The ECU 100 executes normal operation control processing when the vehicle is temporarily stopped during operation (step S110). That is, ECU 100 idles internal combustion engine 10 at the valve timing shown in FIG. 2A according to the map shown in FIG. FIG. 4A shows the valve timing during idling (same as A in FIG. 2).

  The ECU 100 monitors whether a predetermined engine stop condition is satisfied while maintaining normal operation control (idling state) (step S120). The engine stop condition is, for example, (1) the internal combustion engine 10 is sufficiently warmed up (the coolant temperature is equal to or higher than a reference value). (2) The battery 400 has a certain amount of power storage (the voltage is equal to or higher than a reference value). (3) The accelerator opening degree θac = 0. (4) The brake is depressed. (5) Five conditions that vehicle speed = 0 are used, and it may be determined that the engine stop condition is satisfied when all the five conditions are satisfied. When ECU 100 determines that the engine stop condition is not satisfied (step S120: NO), ECU 100 maintains normal operation control (step S110). When the engine stop condition is satisfied (step S120: YES), ECU 100 shifts from the normal operation control to the automatic stop control, and executes the engine automatic stop process (step S130).

  FIG. 5 is a flowchart showing a processing routine of engine automatic stop processing. When starting the engine automatic stop process, ECU 100 controls exhaust side VVT 46 to retard the opening / closing timing of exhaust valve 40 (step S210). The retard amount is set so that the opening timing of the exhaust valve 40 is retarded until the timing at which the piston is located at the bottom dead center in the expansion stroke (hereinafter also referred to as the bottom dead center of the expansion stroke). The The changeable range of the exhaust side VVT 46 of the internal combustion engine 10 according to the present embodiment is a range from 60 degrees before the bottom dead center of the expansion stroke to the bottom dead center of the expansion stroke when the exhaust valve 40 is opened. The ECU 100 makes the opening / closing timing of the exhaust valve 40 the most retarded. FIG. 4B shows the valve timing retarded by this control.

  Subsequently, the ECU 100 controls the fuel injection valve 50 to stop fuel injection and also controls the spark plug 25 to stop ignition (step S220). Thereby, the combustion of the air-fuel mixture in the internal combustion engine 10 is stopped. Even if the stop of fuel injection and ignition is stopped, any cylinder is in the expansion stroke at that time, and the inertial force also works. Therefore, in actuality, the crankshaft 60 does not stop immediately, but for several strokes. Stop completely after rotating.

  When the fuel injection and ignition are stopped, the ECU 100 immediately executes a process of estimating a crank angle (hereinafter referred to as a stop crank angle) θcr_stop (stop crank angle) when the crankshaft 60 of the internal combustion engine 10 is completely stopped. (Step S230). An example of this estimation process will be described. First, the ECU 100 detects an intake pressure Pin, an engine speed Ne, and a crank angle θcr at the time of fuel injection and ignition stop. The ECU 100 acquires the stop crank angle θcr_stop with reference to the three-dimensional map based on the detected intake pressure Pin, engine speed Ne, and crank angle θcr. The three-dimensional map shows the correspondence relationship between the stop pressure angle θcr_stop and the intake pressure Pin, the engine speed Ne and the crank angle θcr at the time of fuel injection and ignition stop, which are obtained in advance by experiments. It is remembered.

  The ECU 100 fills a cylinder (hereinafter referred to as the first explosion cylinder) that first burns the air-fuel mixture when the internal combustion engine 10 is started next time (step S240), and ends this process. Specifically, the ECU 100 predicts from the acquired stop crank angle θcr_stop a cylinder in which the piston position reaches the compression stroke when the crankshaft 60 is completely stopped (hereinafter referred to as a stop-time compression stroke cylinder). FIG. 6 is a schematic diagram for explaining the relationship between the crank angle θcr and the stroke of each cylinder in the internal combustion engine 10 (not a precise representation of valve timing). As shown in the figure, in the internal combustion engine 10 that is a four-cylinder engine, four strokes are repeated with the crank angle varied by 180 degrees between the cylinders. Therefore, it can be seen that one cylinder is always in the compression stroke no matter where the stop crank angle θcr_stop is located. For example, as shown in FIG. 6, when it is estimated that the stop crank angle θcr_stop is located between 0 degrees and 180 degrees, it is predicted that the cylinder # 2 will be the compression stroke cylinder at the time of stop.

  Based on the control of the ECU 100, the fuel injection valve 50 measures the intake air of the stop-time compression stroke cylinder so that the air-fuel mixture is supplied into the stop-time compression stroke cylinder immediately before the crankshaft 60 stops. Inject fuel into the port. At the next start-up of the internal combustion engine 10, the stop-time compression stroke cylinder (cylinder # 2 in the example shown in FIG. 6) becomes the initial explosion cylinder.

  Thereafter, the crankshaft 60 is completely stopped. That is, the processes in steps S230 and S240 are executed within a short period from when fuel injection and ignition are stopped until the crankshaft 60 is completely stopped.

  When the internal combustion engine 10 is automatically stopped, the ECU 100 monitors whether or not a predetermined engine start condition is satisfied (step S140). As the predetermined engine start condition, the five engine stop conditions described above may be used as they are, and it may be determined that the engine start condition is satisfied when one of the five conditions is not satisfied. When the engine start condition is not satisfied (step S140: NO), the ECU 100 continues to monitor the engine start condition while keeping the internal combustion engine 10 in the automatic stop state. When the engine start condition is satisfied (step S140: YES), ECU 100 executes an engine automatic start process (step S150).

  FIG. 7 is a flowchart showing a processing routine of engine automatic start processing. When the ECU 100 starts the engine automatic start process, the ECU 100 controls the inverter 300 to start driving the electric motor 200 (step S310). The crankshaft 60 is rotationally driven by the power of the electric motor 200, and the first explosion cylinder is driven by the spark plug 25 in the vicinity of the piston position of the first explosion cylinder (stopped compression cylinder filled with fuel) reaching the compression top dead center. The air-fuel mixture is ignited (step S320). Due to the combustion pressure in the first explosion cylinder and the power of the electric motor 200, the angular velocity Vθ of the crankshaft 60 (hereinafter referred to as the crank angular velocity Vθ) quickly increases.

  The ECU 100 determines whether or not the exhaust valve 40 of the first explosion cylinder has been opened (step S330). Since the valve opening timing of the exhaust valve 40 is set at the bottom dead center of the expansion stroke by the retard angle control (FIG. 5: step S210) in the engine automatic stop process, the ECU 100 detects the crank angle θcr, It is determined whether or not the crank angle θcr has reached the bottom dead center of the expansion stroke in the first explosion cylinder.

  When the crank angle θcr reaches the expansion stroke in the first explosion cylinder, that is, when the exhaust valve 40 is opened in the first explosion cylinder (step S330: YES), the ECU 100 advances the opening / closing timing of the exhaust valve 40. Valve opening / closing timing advance processing is executed (step S340).

  FIG. 8 is a flowchart showing a processing routine of exhaust valve opening / closing timing advance processing. First, the ECU 100 controls the exhaust side VVT 46 to advance the opening / closing timing of the exhaust valve 40 to a position where the overlap period does not occur (step S410). FIG. 4C shows the valve timing after the advance angle control in this step. The overlap period is a period in which the intake valve 30 and the exhaust valve 40 are simultaneously opened in one cylinder. As shown in FIG. 4A, the overlap period OL occurs at the valve timing before the advance angle control in this step, but the overlap period occurs at the valve timing after the advance angle control shown in FIG. It can be seen that OL has not occurred.

  The ECU 100 further detects the crank angular speed Vθ and determines whether or not the crank angular speed Vθ is greater than the reference crank angular speed Vθ_ref (step S420). The reference crank angular velocity Vθ_ref is a value determined in advance by experiment. If the crank angular velocity at this time is equal to or higher than the reference crank angular velocity Vθ_ref, the engine speed Ne is not changed with the valve timing shown in FIG. This is a value that rises too much and causes a so-called blow-up. In the present embodiment, the reference crank angular velocity Vθ_ref is set to about 200 rpm (rotation number / minute) in terms of engine rotation speed.

  Here, the crank angular speed Vθ (for example, radians / second) is a value representing the rotational speed of the crankshaft 60 calculated based on the electrical signal from the crank angle sensor 102, and is essentially the engine rotational speed Ne. The same. The detection of the rotational speed in step S420 is to detect an instantaneous rotational speed that continuously changes in a short period of time such that the crankshaft 60 rotates halfway. For this reason, for the rotational speed of the crankshaft 60 detected in step S420, the term crank angular speed Vθ is used instead of the engine speed Ne.

  When the detected crank angular velocity Vθ is larger than the reference crank angular velocity Vθ_ref (step S420: YES), ECU 100 controls exhaust side VVT 46 to further advance the opening / closing timing of exhaust valve 40 (step S430). FIG. 4D shows the valve timing after the additional advance control in this step. The additional advance amount Δθfwd at this time is determined according to the detected crank angular velocity Vθ. For example, a map in which the advance amount Δθfwd corresponding to the crank angular velocity Vθ is experimentally determined and recorded in advance is stored in the ROM of the ECU 100, and the advance amount Δθfwd may be determined with reference to this map. .

  When the detected crank angular velocity Vθ is smaller than the reference crank angular velocity Vθ_ref (step S420: NO), or after executing the additional advance angle control in step S430, the ECU 100 opens the exhaust valve 40 of the second explosion cylinder. It is determined whether or not (step S440). The second explosion cylinder is a cylinder that burns the air-fuel mixture after the first explosion cylinder. In the example shown in FIG. 6, when the first explosion cylinder is the # 2 cylinder, the # 1 cylinder corresponds to the second explosion cylinder. The ECU 100 determines whether or not the exhaust valve 40 of the second explosion cylinder is opened depending on whether or not the crank angle θcr has reached a crank angle corresponding to the opening timing of the exhaust valve 40 in the second explosion cylinder. Become.

  When the exhaust valve 40 is opened in the two explosion cylinders (step S440: YES), the ECU 100 ends this process and returns to the process routine shown in FIG. The ECU 100 repeats the processing from step S420 to step S430 until the exhaust valve 40 is opened in the second explosion cylinder (step S440: NO). As described above, the advance processing of the opening / closing timing of the exhaust valve 40 shown in FIG. 8 is performed from the exhaust stroke start timing of the first explosion cylinder to the exhaust stroke start timing of the second explosion cylinder, as indicated by the symbol t in FIG. Executed in a very short period of time.

  Returning to FIG. 7 and continuing the description, when the exhaust valve opening / closing timing advance processing (step S340) ends, the ECU 100 monitors whether or not the engine speed Ne has reached a predetermined speed Ne_ref (step S350). . When the engine speed Ne reaches the predetermined value Ne_ref (step S350: YES), the ECU 100 controls the inverter 300 to end the driving of the electric motor 200 and ends the engine automatic start process. The predetermined rotational speed Ne_ref is a rotational speed at which the internal combustion engine 10 can reliably shift to the idling state without assisting the rotational drive of the crankshaft 60 by the electric motor 200, and is determined empirically. In the present embodiment, the predetermined rotational speed Ne_ref is set to about 400 rpm.

  Returning to FIG. 3 and continuing the description, the ECU 100 shifts from the engine start process (step S150) to the normal operation control process (step S160). This normal operation control process is the same as the normal operation control process (step S110) in the idling state before the internal combustion engine 10 is automatically stopped. That is, ECU 100 idles internal combustion engine 10 at the valve timing shown in FIG. 2A according to the map shown in FIG.

  According to the internal combustion engine 10 according to the present embodiment configured as described above, the timing at which the exhaust valve 40 is opened immediately after the air-fuel mixture is first combusted in the first explosion cylinder at the time of automatic start is the conventional value. It is retarded from the internal combustion engine and set to the bottom dead center of the expansion stroke. As a result, since the combustion pressure of the first explosion is used to push down the piston without being released from the exhaust valve 40 at an early stage, the combustion pressure of the first explosion can be efficiently extracted from the crankshaft 60 as power. it can. Therefore, the crank angular speed of the crankshaft 60 can be quickly increased, and the startability of the internal combustion engine 10 can be improved.

  Furthermore, since the opening timing of the exhaust valve 40 is advanced after the exhaust valve 40 is opened in the first explosion cylinder, the combustion pressure after the second explosion is released from the exhaust valve 40 earlier. As a result, with respect to the combustion pressure after the second explosion, extraction as power is suppressed, and so-called blow-up can be prevented. Further, since the advance amount in such advance control is determined according to the crank angular velocity, appropriate advance control according to the degree of blow-up is possible.

  Further, the opening timing of the exhaust valve 40 is advanced, and the closing timing of the exhaust valve 40 is advanced so that no overlap period occurs. As a result, the exhaust gas once exhausted from the cylinder can be prevented from flowing back into the cylinder during the overlap period, and the combustion can be stabilized.

  Further, at the time of automatic stop, the compression stroke cylinder at the time of stop is predicted, and the internal combustion engine 10 is stopped in a state where fuel is filled in the compression stroke cylinder at the time of stop. Then, the internal combustion engine 10 is started using the compression stroke cylinder at the time of stop as the first explosion cylinder. As a result, the compression stroke cylinder at the time of stoppage can be immediately ignited at the compression top dead center immediately after, so that the internal combustion engine 10 starts the first combustion before the crankshaft 60 rotates at least 180 degrees at the start. it can. For this reason, the startability of the internal combustion engine 10 can be further improved.

B. Variations:
In the above embodiment, since the exhaust side VVT 46 is in the range from 60 degrees before the bottom dead center of the expansion stroke to the bottom dead center of the expansion stroke as viewed at the opening timing of the exhaust valve 40, the ECU 100 performs the engine stop process. The valve opening timing of the exhaust valve 40 is retarded to the bottom dead center of the expansion stroke (FIG. 5: Step S210). In the case of an internal combustion engine equipped with an exhaust side VVT in which the changeable range is narrow and the exhaust valve cannot be delayed until the bottom dead center of the expansion stroke, in step S210, the exhaust valve is opened. Although the timing cannot be set to the bottom dead center of the expansion stroke, the exhaust valve opening timing is retarded as much as possible to bring the exhaust valve opening timing as close as possible to the bottom dead center of the expansion stroke. By delaying the timing at which the combustion pressure of the first explosion is released from the exhaust valve as much as possible, the combustion pressure can be extracted as power as efficiently as possible, and the startability of the internal combustion engine can be improved.

  On the other hand, in the case of an internal combustion engine equipped with an exhaust side VVT that has a wide changeable range and can retard the opening timing of the exhaust valve beyond the bottom dead center of the expansion stroke, in step S210 the exhaust valve The valve opening timing is not retarded at the most, but is delayed to the bottom dead center of the expansion stroke. If retarded beyond the bottom dead center of the expansion stroke, the combustion pressure will not be released from the exhaust valve even after the piston reaches the bottom dead center and starts to rise, and the combustion pressure prevents the crankshaft 60 from rotating. Because it will end up.

  In the above-described embodiment, the compression stroke cylinder at the time of stop is predicted, and the predicted cylinder is filled with fuel (FIG. 5: Steps S230 to S240), but the piston position is expanded when the crankshaft 60 is completely stopped. A cylinder that reaches the stroke (hereinafter referred to as an expansion stroke cylinder when stopped) may be predicted, and fuel may be charged into the predicted cylinder. The prediction of the stop expansion stroke cylinder can be executed using a three-dimensional map created in advance, in the same manner as the prediction of the stop compression stroke cylinder. In such a case, the same operational effects as in the above embodiment can be obtained. In addition, when the internal combustion engine 10 is started, the internal combustion engine 10 can be started by immediately igniting the expansion stroke cylinder at the time of stop. Therefore, power that assists the driving of the crankshaft 60 such as the electric motor 200 is used. The internal combustion engine 10 can be started without the need.

  In the internal combustion engine 10 according to the above embodiment, the fuel injection valve 50 is arranged to inject fuel into the intake port, but the fuel injection valve is arranged to inject fuel directly into the cylinder. An internal combustion engine may be used. In such a case, it is not necessary to predict the stop-time compression stroke cylinder or the stop-time expansion stroke cylinder before the crankshaft 60 is completely stopped, and immediately after the crankshaft 60 is completely stopped, the stop-time compression stroke cylinder or The expansion stroke cylinder at the time of stop can be detected, and the detected cylinder can be filled with fuel.

  The internal combustion engine 10 according to the above embodiment drives the exhaust valve 40 to open and close by rotationally driving the exhaust side camshaft 44, and changes the rotational phase between the exhaust side camshaft 44 and the crankshaft 60 by the exhaust side VVT 46. Thus, the opening / closing timing of the exhaust valve 40 is changed, but a mechanism capable of driving the exhaust valve 40 at an arbitrary timing may be used as the variable valve timing mechanism. For example, each exhaust valve 40 may include an electric actuator having a structure in which a plurality of disk-shaped electrostrictive elements are stacked. The exhaust valve 40 can be opened and closed at an arbitrary timing by outputting an electrical signal from the ECU 100 and changing the voltage applied to the electrostrictive element. Thus, if the valve timing control similar to that described in the above embodiment is executed, the same operation and effect as in the above embodiment can be realized.

  As mentioned above, although the Example and modification of this invention were demonstrated, this invention is not limited to these Example and modification at all, and implementation in a various aspect is possible within the range which does not deviate from the summary. It is.

Explanatory drawing which shows schematic structure around the internal combustion engine which concerns on the Example of this invention. The map which shows an example of the correspondence of the operating condition of the internal combustion engine which concerns on an Example, and the opening / closing timing of an intake / exhaust valve. 7 is a flowchart showing a control processing routine of the internal combustion engine 10 when idling stop is performed. FIG. 4 is an explanatory diagram schematically showing opening and closing timings of the intake valve 30 and the exhaust valve 40 with respect to a crank angle when performing idling stop. The flowchart which shows the process routine of an engine automatic stop process. Schematic explaining the relationship between the crank angle θcr and the stroke of each cylinder in the internal combustion engine 10. The flowchart which shows the process routine of an engine automatic start process. 7 is a flowchart showing a processing routine of exhaust valve opening / closing timing advance processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 12 ... Intake pipe 16 ... Exhaust pipe 20 ... Cylinder block 22 ... Cylinder head 25 ... Spark plug 30 ... Intake valve 32 ... Intake side cam 34 ... Intake side camshaft 36 ... Intake side VVT (variable valve timing mechanism)
40 ... Exhaust valve 42 ... Exhaust side cam 44 ... Exhaust side camshaft 46 ... Exhaust side VVT (variable valve timing mechanism)
DESCRIPTION OF SYMBOLS 50 ... Fuel injection valve 52 ... Fuel supply pump 60 ... Crankshaft 62 ... Crank pulley 70 ... Throttle valve 72 ... Electric actuator 80 ... Catalytic device 90 ... Air cleaner 100 ... ECU
DESCRIPTION OF SYMBOLS 102 ... Crank angle sensor 104 ... Accelerator opening sensor 106 ... Intake side cam angle sensor 108 ... Exhaust side cam angle sensor 110 ... Intake pressure sensor 200 ... Electric motor 202 ... Electric motor pulley 204 ... V-ribbed belt 300 ... Inverter 400 ... Battery OL ... Over Lap period IN ... Intake valve opening period EX ... Exhaust valve opening period

Claims (11)

An internal combustion engine that burns an air-fuel mixture formed in a cylinder and extracts power from a crankshaft,
An intake valve and an exhaust valve provided for each cylinder;
A variable valve timing mechanism capable of adjusting the opening and closing timing of the exhaust valve;
Control means for controlling the variable valve timing mechanism, the control for retarding the opening timing of the first exhaust valve to be changed after the first combustion in the first explosion cylinder in which the air-fuel mixture burns first when starting the internal combustion engine And an internal combustion engine. The internal combustion engine of claim 1,
When the opening timing of the exhaust valve that has been retarded by the variable valve timing mechanism is before the bottom dead center in the expansion stroke,
The control means is an internal combustion engine that retards the opening timing of the first exhaust valve most. The internal combustion engine of claim 1,
When the variable valve timing mechanism can retard the opening timing of the exhaust valve until after the bottom dead center in the expansion stroke,
The control means is an internal combustion engine that retards the opening timing of the first exhaust valve to the bottom dead center. The internal combustion engine according to any one of claims 1 to 3,
The control means is an internal combustion engine that advances the opening timing of the exhaust valve of each cylinder from the opening timing of the first exhaust valve after the opening of the first exhaust valve. The internal combustion engine according to claim 4,
An internal combustion engine in which the advance amount by the control means is determined so that there is no overlap period in which the intake valve and the exhaust valve are simultaneously opened. The internal combustion engine according to claim 4, further comprising:
A detecting means for detecting a crank angular speed which is an angular speed of the crankshaft;
An internal combustion engine in which the amount of advance by the control means is determined according to the detected crank angular velocity. The internal combustion engine according to any one of claims 1 to 6, further comprising:
Predicting means for predicting a stop-time compression stroke cylinder that is in a compression stroke at the time of stop before stopping the internal combustion engine;
Fuel filling means for bringing the predicted stop-time compression stroke cylinder into a fuel-filled state when the internal combustion engine is stopped;
An electric motor that rotationally drives the crankshaft,
An internal combustion engine that rotates the crankshaft to a compression top dead center in the stop-time compression stroke cylinder and then starts the stop-time compression stroke cylinder as the first explosion cylinder. The internal combustion engine according to any one of claims 1 to 6, further comprising:
A fuel injection valve for directly injecting fuel into the cylinder;
Detection means for detecting a compression stroke at the time of stop in the compression stroke when the internal combustion engine is stopped;
Injection valve control means for controlling the fuel injection valve to fill the detected stop-time compression stroke cylinder with fuel;
An electric motor that rotationally drives the crankshaft,
An internal combustion engine that rotates the crankshaft to a compression top dead center in the stop-time compression stroke cylinder and then starts the stop-time compression stroke cylinder as the first explosion cylinder. The internal combustion engine according to any one of claims 1 to 6, further comprising:
Predicting means for predicting a stop-time expansion stroke cylinder that is in an expansion stroke at the time of stop before stopping the internal combustion engine;
Fuel filling means for bringing the predicted stop expansion stroke cylinder filled with fuel when the internal combustion engine is stopped,
An internal combustion engine that starts the expansion stroke cylinder when stopped as the first explosion cylinder. The internal combustion engine according to any one of claims 1 to 6, further comprising:
A fuel injection valve for directly injecting fuel into the cylinder;
Detecting means for detecting a stop-time expansion stroke cylinder in an expansion stroke when the internal combustion engine is stopped;
Injection valve control means for controlling the fuel injection valve and filling the detected stop-time expansion stroke cylinder with fuel,
An internal combustion engine that starts the expansion stroke cylinder when stopped as the first explosion cylinder. An exhaust valve control method for an internal combustion engine having a variable valve timing mechanism capable of adjusting a timing at which an exhaust valve opens and closes, and combusting an air-fuel mixture formed in a cylinder to extract power from a crankshaft,
An exhaust valve control method for retarding the opening timing of the first exhaust valve that stops after the first combustion in the first explosion cylinder in which the air-fuel mixture burns first when the internal combustion engine is started.

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