WO2002031355A1

WO2002031355A1 - Control method for spark ignition engine

Info

Publication number: WO2002031355A1
Application number: PCT/JP2000/007025
Authority: WO
Inventors: Yoshihiro Sukegawa; Minoru Oosuga; Toshiharu Nogi; Masami Nagano
Original assignee: Hitachi, Ltd.
Priority date: 2000-10-10
Filing date: 2000-10-10
Publication date: 2002-04-18
Also published as: JPWO2002031355A1

Abstract

A control method for spark ignition engine capable of reducing emissions at the start of the engine and increasing the reliability and durability thereof, wherein a control unit (25) is formed so that, when the temperature of the engine is lower than a specified temperature, an ignition timing is advanced ahead of one at which a fuel efficiency is best.

Description

TECHNICAL FIELD The present invention relates to a method for controlling a spark ignition engine, and more particularly, to a method for controlling a spark ignition engine which is effective for controlling exhaust emission suitable for control at the time of starting the spark ignition engine. About. BACKGROUND ART When a spark ignition engine is started, if the engine temperature is low, the injected fuel collides with a low-temperature intake valve or an intake port, and a liquid film of fuel is formed on a wall surface. The liquid film on the low-temperature wall is poorly vaporized and deteriorates in combustion, so that a large amount of unburned hydrocarbons (H C) is emitted in the exhaust gas. In addition, in order to improve the combustion at the start, it is common practice to inject a large amount of fuel at the start to make the fuel richer than the stoichiometric air-fuel ratio (fuel increase at the start). In this case, Excess fuel that could not be vaporized by adhering to the low-temperature wall enters the exhaust gas and increases HC.

Therefore, in a conventional spark ignition engine, for example, as described in Japanese Patent Application Laid-Open No. H11-8203, the ignition timing is delayed with respect to the normal ignition time in an idle state. It has been known that by squaring, the exhaust gas temperature is raised, and the three-way catalyst attached to the exhaust pipe is heated and activated at an early stage, thereby reducing startup emissions. However, this method cannot reduce the increase in HC due to fuel adhering to the intake valve and the like.

Therefore, for example, as described in Japanese Patent Application Laid-Open No. 5-26013 and Japanese Patent Application Laid-Open No. Hei 6-221121, the intake valve is heated by an electric heater to reduce HC. It is also known to reduce. Disclosure of Invention · However, in the method described in Japanese Patent Application Laid-Open No. Hei 5-26013 and Japanese Patent Application Laid-Open No. Hei 6-221121, a heater is directly provided at an intake valve that repeats opening and closing operations at high speed. However, there was a problem that reliability and durability were low.

It is an object of the present invention to provide a control method for a spark ignition engine that can reduce emissions at the time of starting and has improved reliability and durability.

In order to achieve the above object, the present invention provides a spark ignition engine having a fuel injection valve, in which, when the engine temperature is lower than a predetermined temperature, the ignition timing is advanced from the ignition timing at which the fuel efficiency becomes best. It is like that.

With this method, the temperature of the combustion gas in the combustion chamber can be raised to a higher temperature, and heat transfer from this high-temperature gas causes the intake valve to heat up quickly. The heat transfer from the valve allows the adhering fuel to be quickly vaporized, reducing wall flow when starting the engine and reducing HC.

Further, in order to achieve the above object, the present invention provides a spark igniter having a fuel injection valve, comprising: means for changing an opening timing of an intake valve, wherein when an engine temperature is lower than a predetermined temperature, The opening timing of the intake valve is advanced from the normal opening timing.

With this method, high-temperature combustion gas is introduced into the intake pipe immediately after the intake valve opens, and the temperature of the intake valve rises, so the high-temperature gas introduced into the intake pipe promotes fuel vaporization and reduces HC. Can be.

Further, in order to achieve the above object, the present invention provides a spark ignition engine having a fuel injection valve, further comprising a swirl control valve for generating a swirl by changing a flow passage step area of an intake pipe, wherein an engine temperature is lower than a predetermined temperature. When the engine temperature is lower than the predetermined temperature, the swirl intensity generated by the swirl control valve is made lower than when the engine temperature is higher than a predetermined temperature.

With this method, the air flow velocity in the intake pipe is reduced, and the trajectory of the fuel spray due to the air flow can be prevented from being deflected. Therefore, the adhesion of the fuel injected in the intake stroke to the wall surface is reduced, and HC can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system configuration diagram showing a configuration of an engine control system using a spark ignition engine control method according to a first embodiment of the present invention.

FIG. 2 is a transparent perspective view showing a configuration of an engine using the control method of the spark ignition engine according to the first embodiment of the present invention.

FIG. 3 is a transparent plan view showing a configuration of an engine using the spark ignition engine control method according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a control unit in an engine control system using the spark ignition engine control method according to the first embodiment of the present invention. FIG. 5 is a flowchart showing the content of the engine start-up process by the control method of the spark ignition engine according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating the relationship between the injection pulse width of the fuel injection valve and the fuel injection amount in the engine control system using the spark ignition engine control method according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of the ratio of fuel adhesion to the intake valve when fuel is injected during the intake stroke and when fuel is injected during the exhaust stroke in the method for controlling the spark ignition engine according to the first embodiment of the present invention. .

FIG. 8 is an explanatory diagram of a change in the amount of unburned hydrocarbons (H C) emitted from the engine with respect to the fuel injection timing in the control method for the spark ignition engine according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram of the behavior of the fuel in the combustion chamber when the fuel injection timing is set to the intake stroke in the method for controlling the spark ignition engine according to the first embodiment of the present invention.

FIG. 10 is an explanatory diagram of the time history of the gas temperature in the combustion chamber in the control method of the spark ignition engine according to the first embodiment of the present invention.

FIG. 11 shows an explosion stroke when the air-fuel mixture formed by the intake stroke injection in the control method of the spark ignition engine according to the first embodiment of the present invention is burned with the ignition timing advanced from normal, (Expansion stroke) It is explanatory drawing of a state.

FIG. 12 is a diagram illustrating a suction method in the control method of the spark ignition engine according to the first embodiment of the present invention. FIG. 4 is an explanatory diagram of how to determine a valve operating time t 1.

FIG. 13 is an explanatory diagram of the behavior of the fuel in the combustion chamber when the fuel injection timing is set to the exhaust stroke in the control method of the spark ignition engine according to the first embodiment of the present invention. FIG. 14 is an explanatory diagram of the behavior of the air-fuel mixture during the intake stroke in the control method for the spark ignition engine according to the first embodiment of the present invention.

FIG. 15 is an explanatory diagram of the behavior of the air-fuel mixture during the exhaust stroke in the control method for the spark ignition engine according to the first embodiment of the present invention.

FIG. 16 is a transparent perspective view showing a configuration of an engine using the spark ignition engine control method according to the second embodiment of the present invention.

FIG. 17 is an explanatory diagram of the operation of an intake valve of an engine using the method for controlling a spark ignition engine according to the second embodiment of the present invention.

FIG. 18 is a flowchart showing the processing content of the engine start-up processing by the control method of the spark ignition engine according to the second embodiment of the present invention.

FIG. 19 is an explanatory diagram of the gas behavior immediately before the end of the exhaust stroke in the intake valve heating mode in the control method of the spark ignition engine according to the second embodiment of the present invention.

FIG. 20 is an explanatory diagram of the behavior of gas and fuel spray at the initial stage of the intake stroke in the intake valve heating mode in the spark ignition engine control method according to the second embodiment of the present invention.

FIG. 21 is a transparent perspective view showing a configuration of an engine using the spark ignition engine control method according to the third embodiment of the present invention.

FIG. 22 is an explanatory diagram of the operation of an exhaust valve of an engine using the control method for a spark ignition engine according to the third embodiment of the present invention.

FIG. 23 is a flowchart showing the processing content of the engine startup processing by the control method of the spark ignition engine according to the third embodiment of the present invention.

FIG. 24 is a transparent perspective view showing the configuration of an engine using the method for controlling a spark ignition engine according to the fourth embodiment of the present invention.

FIG. 25 is a front view showing a configuration of a swirl control valve attached to an engine using the method for controlling a spark ignition engine according to the second embodiment of the present invention.

FIG. 26 is a flowchart showing a method for controlling a spark ignition engine according to the second embodiment of the present invention. FIG. 5 is an explanatory view of the operation of the swirl control valve attached to the engine.

FIG. 27 is a front view showing another configuration of the swirl control valve attached to the engine using the spark ignition engine control method according to the second embodiment of the present invention.

FIG. 28 is a front view showing another configuration of the swirl control valve attached to the engine using the control method of the spark ignition engine according to the second embodiment of the present invention. FIG. 29 is a flowchart showing the processing content of the engine startup processing by the control method of the spark ignition engine according to the fourth embodiment of the present invention.

FIG. 30 is an explanatory diagram of the fuel and gas behavior in the intake stroke in the intake valve heating mode in the spark ignition engine control method according to the fourth embodiment of the present invention.

Figure 31 is an explanatory diagram of the fuel and gas behavior during the intake stroke as a reference example. FIG. 32 is an explanatory diagram of the fuel and gas behavior during the intake stroke in the catalyst activation mode in the spark ignition engine control method according to the fourth embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a control method for a spark ignition engine according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 15.

First, a system configuration of an engine control system using the control method for a spark ignition engine according to the present embodiment will be described with reference to FIG.

FIG. 1 is a system configuration diagram showing a configuration of an engine control system using a control method for a spark ignition engine according to a first embodiment of the present invention.

The air introduced from the inlet 12 of the air cleaner 11 passes through the air filter 11 ′ and then enters the collector 16 through the downstream duct 14 and the throttle pod 15. The air in the collector 16 is charged into the cylinder of the engine 1 through the intake pipe 18. The amount of air drawn into the duct 14 from the air cleaner 11 is detected by a hot wire air flow meter 13.

On the other hand, the fuel pressurized by the fuel pump 20 from the fuel tank 19 passes through the fuel damper 21 and the fuel filter 22 and is guided to the fuel injection valve 4. Part of the fuel guided to the fuel injection valve 4 is guided to the fuel pressure regulator 24, and the fuel tank 1 Returned to 9. In the fuel pressure regulation 24, the pressure of the fuel supplied to the fuel injection valve 4 is regulated to a constant value. The fuel injection valve 4 injects atomized fuel into the intake pipe 18. In this example, the fuel injection valve 4 is attached to the intake pipe of each cylinder, and in the case of a multi-cylinder engine, controls the amount of fuel supplied to each cylinder. A so-called MPI (multi-port injection) system Is composed.

Here, a configuration of an engine using the control method of the spark ignition engine according to the present embodiment will be described with reference to FIGS.

FIG. 2 is a transparent perspective view showing a configuration of an engine using the control method of the spark ignition engine according to the first embodiment of the present invention. FIG. 3 is a transparent plan view showing the configuration of an engine using the control method for a spark ignition engine according to the first embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts.

As shown in FIGS. 2 and 3, the engine 1 has a so-called 4-valve engine configuration in which the combustion chamber 11 has two intake valves 5 and two exhaust valves 6. An ignition plug 45 is provided above the combustion chamber 11.

A fuel injection valve 4 is attached to an intake pipe 18 upstream of the intake valve 5. Fuel is injected by injecting fuel spray S from the fuel injection valve 4 toward the head 5 ′ of the intake valve 5.

In general, the fuel injection timing is determined in either the exhaust stroke in which the intake valve 5 is closed and the piston 7 in the cylinder 8 is in the upward movement, or the intake stroke in which the intake valve 5 is opened and the piston 7 is in the downward movement. Done.

As shown in FIG. 3, the spray injected from the fuel injection valve 4 is in the form of a two-way spray which is injected toward each intake passage 2. The spray direction and spray width are determined so as not to collide with the wall surface of the intake pipe 18 and to collide with the head 5 ′ of the intake valve 5 when the intake valve 5 is closed. Further, the spray S is atomized by the fuel injection valve 4 so that the Sauter average particle diameter becomes about 50 m or less.

Returning to FIG. 1, the fuel injected into the intake pipe 18 evaporates, mixes with the air filled in the combustion chamber 11, and is ignited by a spark plug (not shown) and burns. The combustion gas in the combustion chamber 11 passes through the exhaust pipe 31, is purified by the catalyst 32, and is released into the atmosphere. Here, the catalyst 32 is a so-called three-way catalyst, and the exhaust gas Simultaneous oxidation of CO and HC and reduction of NO. However, when the engine is started, the temperature of the catalyst 32 is low and not activated, so that harmful components in the exhaust gas are difficult to purify.

An electrical output signal representing the amount of intake air detected by the air flow meter 13 is input to the control unit 25. The throttle body 15 is provided with a throttle sensor 26 for detecting the opening of the throttle valve. The output signal of the throttle sensor 26 is also input to the control unit 25.

A distributor 28 is provided near the engine 1. A crank angle sensor (not shown) for detecting the crank angle of the engine is built in the interior of the distributor 28. The output signal of the crank angle sensor is also input to the control unit 25. In addition, the control unit 25 also receives output signals from a water temperature sensor 29 for detecting the temperature of the engine cooling water and an O2 sensor 30 for detecting the oxygen concentration in the exhaust gas. .

The control unit 25 performs predetermined arithmetic processing based on the signals from the various sensors described above, and drives various actuators in order to perform optimal control according to the engine operating state. For example, the ignition timing is controlled by controlling the voltage applied to the induction coil 27, and the fuel injection timing and the injection amount are controlled by controlling the opening of the fuel injection valve 4.

Here, the configuration of the control unit 25 in the engine control system using the control method of the spark ignition engine according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of a control port in an engine control system using the control method of the spark ignition engine according to the first embodiment of the present invention. The control unit 25 consists of an arithmetic unit (MPU) 251, a rewritable nonvolatile memory (EP-ROM) 252, a random access memory 253, an input port 2524, and an output port. It consists of 2 5 5.

The arithmetic unit 151 operates in synchronization with a fixed frequency clock generated by a crystal oscillator (not shown), and has a built-in timer that can measure the elapsed time from an arbitrary point based on the clock. The input ports 254 include a water temperature sensor 29, an air flow sensor 13, a crank angle sensor, a throttle sensor 26, a starter switch, Inputs signals indicating the operating state of the engine detected by various sensors and switches, such as a battery voltage sensor, idle switch, # 2 sensor 30 and engine temperature sensor. From the output port 255, a signal for controlling various factories such as the fuel injection valve 4, the ignition coil 28, and the fuel pump 20 is output.

Next, the processing content of the engine start processing by the control method of the spark ignition engine according to the present embodiment will be described with reference to FIG.

FIG. 5 is a flowchart showing the processing content of the engine start processing by the control method of the spark ignition engine according to the first embodiment of the present invention.

In step s100, when detecting the ON of the ignition key, the control unit 25 starts the engine start processing according to the present embodiment. Next, in step s105, the control unit 25 starts the cell motor.

Next, in step s110, the control unit 25 sets the internal timer time t to 0.

Next, in step s115, the control unit 25 reads the water temperature T detected by the water temperature sensor 29, and determines whether the temperature is lower than a predetermined temperature Twl. Here, for example, the predetermined temperature Twl is usually about 50 to 80 ° C. If the detected water temperature T is higher than the predetermined temperature Twl, the mode shifts to the normal operation mode. On the other hand, if the water temperature T is lower than the predetermined temperature Twl, the process proceeds to the process after step s120, and shifts to the operation control of the intake valve heating mode.

Next, the processing content of the intake valve heating mode will be described using steps s120 to s135.

In step s120, the control unit 25 calculates the amount of injected fuel based on signals from the water temperature sensor, the air amount sensor, and the like. At this time, when the water temperature is low, the fuel injection amount is appropriately corrected according to the water temperature in order to prevent the combustion from being deteriorated due to fuel vaporization delay. That is, when the water temperature is low, the fuel injection amount is increased so as to be richer than the stoichiometric mixture ratio (in the case of gasoline, the air-fuel ratio is about 15), assuming a delay in vaporization.

Here, referring to FIG. 6, the relationship between the injection pulse width of the fuel injection valve and the fuel injection amount will be described. Will be explained.

As shown in FIG. 6, an almost proportional relationship is established between the injection pulse width of the fuel injection valve and the injection amount. The relationship shown in FIG. 6 is obtained in advance and stored in the control unit. The control unit 25 determines the valve opening time (injection pulse width) of the fuel injection valve from the required fuel amount. The control unit 25 applies a valve opening signal (injection pulse) to the fuel injection valve only during the determined valve opening time to inject a predetermined amount of fuel.

Next, in step s1 25 of FIG. 5, the control unit 25 detects the crank angle of the engine based on the signal of the crank angle sensor, and calculates the crank angle of the engine in the intake pipe by the fuel injection valve during the intake stroke of each cylinder. Inject the required amount of fuel. The feature of the intake valve heating mode according to the present embodiment is that fuel is injected during the intake stroke.

Here, a description will be given of the fuel attachment ratio to the intake valve (the ratio of the fuel attachment to the total injection amount) when fuel is injected during the intake stroke and when fuel is injected during the exhaust stroke, with reference to FIG. .

In FIG. 7, the horizontal axis shows the crank angle (° ATDC), and the vertical axis shows the fuel adhesion ratio (%).

Dotted line A indicates the fuel adhesion ratio when fuel is injected during the exhaust stroke. In exhaust stroke injection, fuel is injected with the intake valve closed, so about half of the injected fuel adheres to the intake valve.

On the other hand, the solid line B shows the fuel adhesion ratio when fuel is injected during the intake stroke. In the intake stroke injection, fuel is injected with the intake valve open, so much fuel is supplied directly into the combustion chamber without colliding with the intake valve. Because of this, intake Fuel adhesion to the valve is significantly reduced compared to exhaust stroke injection.

Next, the change in the amount of unburned hydrocarbons (H C) from the engine with respect to the fuel injection timing will be described with reference to FIG.

FIG. 8 is an explanatory diagram of a change in the amount of unburned hydrocarbons (H C) emitted from the engine with respect to the fuel injection timing in the control method for the spark ignition engine according to the first embodiment of the present invention. In the figure, the horizontal axis shows the fuel injection timing (° ATDC), and the vertical axis shows the unburned hydrocarbon (H C) emission from the engine.

Dotted line C shows the change in unburned hydrocarbon (H C) emission from the engine with respect to the fuel injection timing when the engine is warmed up. With the engine warmed up, H C is lower during fuel injection during the exhaust stroke than during injection during the intake stroke. This is because during the exhaust stroke injection, the amount of fuel attached to the intake valve increases as described above.However, since the temperature of the intake valve is high at the time of the engine, the attached fuel evaporates due to the heat of the intake valve. This is because the fuel and air are better mixed. On the other hand, the solid line D shows a change in the amount of unburned hydrocarbons (H C) emitted from the engine with respect to the fuel injection timing when the engine is cold. When the engine is cold, the intake stroke injection has less HC than the exhaust stroke injection. This is because the temperature of the intake valve is low when the engine is cold, and the fuel adhering to the intake valve is poorly vaporized. As a result, the fuel and air are not sufficiently mixed, and most of the adhered fuel is discharged from the engine without completely burning in the combustion chamber. For this reason, the intake stroke injection with less fuel adhesion to the intake valve can suppress HC emissions.

Therefore, HC can be reduced when the engine is started by reducing the amount of fuel adhering to the intake valve as much as possible during cold periods, and by raising the temperature of the intake valve as soon as possible and using the heat of the intake valve for fuel vaporization.

Here, the behavior of the fuel in the combustion chamber when the fuel injection timing is in the intake stroke in the intake valve heating mode immediately after the start of the engine will be described with reference to FIG. FIG. 9 is an explanatory diagram of the behavior of the fuel in the combustion chamber when the fuel injection timing is set to the intake stroke in the method for controlling the spark ignition engine according to the first embodiment of the present invention. The same reference numerals as those in FIGS. 3 and 4 indicate the same parts.

The fuel spray S injected from the fuel injection valve 4 is injected toward the head 5 ′ of the intake valve 5. Fired. Here, in the intake stroke, the intake valve 5 is opened toward the combustion chamber 11, and a part of the fuel spray S enters the combustion chamber 11 without colliding with the umbrella section 5 ′, and is vaporized and mixed. Forming Qi. The remaining fuel spray collides with the umbrella section 5 ′, but a high-speed air flow from the intake passage 2 toward the combustion chamber 11 occurs on the surface of the intake valve 5 with the intake, so that the fuel spray quickly It is atomized and vaporized and enters the combustion chamber 11 to form an air-fuel mixture.

Therefore, in the intake stroke injection, the fuel liquid film formed on the umbrella portion 5 'is small, and most of the fuel injected in the cycle enters the combustion chamber 11 in the cycle to form an air-fuel mixture.

Next, in step s130 of FIG. 5, the control unit 25 sets the ignition timing by advancing the ignition timing by a predetermined amount ΔΘad with respect to the normal ignition timing. Then, when the crank angle reaches the set angle, an ignition signal is output to the ignition coil. The high-voltage current generated by the ignition coil is distributed to the ignition plug of each cylinder by the distributor, and the gas in the cylinder burns to obtain the engine output. The normal ignition timing is the ignition timing at which the fuel efficiency of the engine is the best, and is usually obtained in advance by a preliminary test on a test bench and stored in the control unit as a function of the engine load, rotation speed, water temperature, etc. I have. Further, the ignition timing advance angle width Δ 0 ad is set so that the maximum temperature of the combustion gas is the highest. Here, the time history of the gas temperature in the combustion chamber will be described with reference to FIG. FIG. 10 is an explanatory diagram of the time history of the gas temperature in the combustion chamber in the control method of the spark ignition engine according to the first embodiment of the present invention.

In the figure, the horizontal axis indicates the crank angle, and the vertical axis indicates the gas temperature in the combustion chamber. Also, the star N indicates the ignition timing at which the usual fuel economy is best, the stars A l and A 2 indicate the ignition timing at the time of ignition advance, and the star D 1 indicates the ignition timing at the time of ignition retard Shows the ignition timing. As shown by the dotted line E, when the ignition timing is shifted to the advanced side (ignition timing A1 leftward) based on the combustion chamber gas temperature at the ignition timing (ignition timing N) at which the best fuel consumption is obtained. As shown by the solid line F, the maximum temperature of the combustion gas increases. This means that by burning in the compression stroke, the fuel is burned while receiving the compression work accompanying the rise of the piston, and is originally taken from the crankshaft of the engine as kinetic energy. This is because part of the combustion energy that is released becomes heat energy.

However, when the ignition timing is further advanced (ignition timing A 2), the gas is ignited without being sufficiently compressed by the piston, and the combustion becomes incomplete. The temperature reached decreases. On the other hand, when the ignition timing is retarded (ignition timing D 1), the maximum temperature of the gas decreases as shown by the two-dot chain line H.

Therefore, in the present embodiment, the ignition advance width Δ 0 ad is set such that the maximum temperature of the gas reaches the highest. The spark advance width ad is obtained by a preliminary test using a test bench or the like, and is usually about 5 to 20 ° crank angle.

Here, the state of the explosion stroke (expansion stroke) when the air-fuel mixture formed by the intake stroke injection is burned with the ignition timing advanced from normal will be described with reference to FIG.

FIG. 11 shows an explosion stroke when the air-fuel mixture formed by the intake stroke injection in the control method of the spark ignition engine according to the first embodiment of the present invention is burned with the ignition timing advanced from normal, (Expansion stroke) It is explanatory drawing of a state. The same reference numerals as those in FIGS. 3 and 4 indicate the same parts.

By advancing the ignition timing more than usual, the maximum attained temperature of the combustion gas C is higher than that during normal combustion, and the convective heat transfer and radiant heat transfer of the high-temperature combustion gas cause the intake valve 5 to operate. The temperature is raised early. This promotes atomization of the spray colliding with the intake valve 5 and vaporization of the attached droplets. In other words, in this operation mode, by injecting fuel during the intake stroke, fuel adhesion to the intake valve is suppressed, and the temperature of the intake valve is quickly raised with the high-temperature combustion gas generated at the advanced ignition timing. By promoting the vaporization of the adhering liquid droplets, the amount of HC discharged when the engine is started is reduced. In addition, since the formation of a liquid film is suppressed by the intake stroke injection, the amount of fuel increase at startup when the engine temperature is low can be reduced, and the increase in HC due to excess fuel can be prevented.

Next, in step s1 35 in FIG. 5, the control unit 25 compares the timer time t with a predetermined intake valve warm-up time t1, and if t <t1, Returning to si 20, the procedure of the intake valve heating mode in which fuel is injected during the intake stroke in the next cycle and the ignition timing is advanced is repeated. On the other hand, if t> t 1 First, it is determined that the temperature of the intake valve has been sufficiently raised, and the operation mode is shifted to the operation mode for activating the catalyst after step s140.

Here, how to determine the intake valve operating time t1 in the method for controlling the spark ignition engine according to the first embodiment of the present invention will be described with reference to FIGS.

FIG. 12 is an explanatory diagram of how to determine the required intake valve warm-up time t1 in the control method for the spark ignition engine according to the first embodiment of the present invention.

In FIG. 12, the horizontal axis represents the elapsed time after the engine started, and the vertical axis represents the surface temperature of the intake valve. That is, the solid line in the figure shows the change of the intake valve surface temperature with respect to the elapsed time after the engine start.

The intake valve surface temperature rises with time due to heat transfer from the combustion gas, and eventually stabilizes at a constant temperature if the engine load is steady. The intake valve warm-up required time t1 is determined as the time when the intake valve reaches a predetermined temperature tc. The temperature t c is a temperature at which the fuel attached to the intake valve can be quickly vaporized, and is desirably, for example, about 50 to 100 ° C. By measuring the temperature rise characteristic of the intake valve as shown in the drawing on a test bench or the like, the intake valve warm-up time t1 can be determined.

Note that the effect can be obtained even when the temperature t1 is set to a constant value. However, the temperature rise characteristics of the intake valve vary depending on the initial temperature of the engine and the outside air temperature.For example, when the cooling water temperature is low, the time t1 is longer when the cooling water temperature is low, and Is desirably corrected to shorten the time t1.

Next, control contents of the catalyst activation mode will be described using steps s140 to s155 in FIG.

In the judgment of step s 1 35 in FIG. 5, if the elapsed time t from the start of starting exceeds t 1, that is, if the temperature of the intake valve becomes higher than the predetermined temperature, the control unit unit 25 Shifts the operation mode of the engine to the catalyst activation mode. In step s140 of FIG. 5, the control unit 25 calculates the amount of injected fuel based on the signals of the water temperature sensor, the air amount sensor, and the like. At this time, when the water temperature is low, the fuel injection amount is appropriately corrected according to the water temperature in order to prevent the combustion from being deteriorated due to the fuel vaporization delay. In other words, when the water temperature is low, evaporation delay is assumed, and the mixture becomes richer than the stoichiometric mixture ratio (in the case of gasoline, the air-fuel ratio is about 15). The fuel injection amount is increased. one

Next, in step s145, the control unit 25 injects a predetermined amount of fuel in the exhaust stroke based on the value detected by the crank angle sensor. ·

Here, the behavior of the fuel and the air-fuel mixture in the combustion chamber in the catalyst activation mode will be described with reference to FIGS. 13 and 14.

FIG. 13 is an explanatory diagram of the behavior of the fuel in the combustion chamber when the fuel injection timing is set to the exhaust stroke in the control method of the spark ignition engine according to the first embodiment of the present invention. The same reference numerals as in FIGS. 3 and 4 indicate the same parts.

In the exhaust stroke, the air flow in the intake passage 2 is weak, and the fuel spray S injected by the fuel injection valve 4 collides with the head 5 ′ of the intake valve 5 without changing its trajectory. The temperature of the head 5 ′ of the intake valve is raised to about 60 to 100 ° C. by the intake valve heating mode performed before the present catalyst activation mode. Therefore, the spray S ′ that has collided with the intake valve head 5 ′ receives heat from the intake valve 5 ′ and quickly evaporates to form a mixture M in the intake passage 2.

FIG. 14 is an explanatory diagram of the behavior of the air-fuel mixture during the intake stroke in the control method for the spark ignition engine according to the first embodiment of the present invention. The same reference numerals as those in FIGS. 3 and 4 indicate the same parts.

The air-fuel mixture M generated in the intake passage 2 is sucked into the combustion chamber 11 together with the air, mixed by the air flow generated at the time of suction, and the fuel and air are well mixed in the combustion chamber 11 To form an air-fuel mixture. Combustion becomes stable by homogenizing the air-fuel mixture, and the ignition timing in this catalyst activation mode can be greatly retarded.

Next, in step s150 of FIG. 5, the control unit 25 ignites the ignition timing on the retard side with respect to the ignition timing at which the fuel efficiency is the best. As shown in FIG. 10, when the ignition timing is retarded from the best fuel consumption timing, the gas temperature in the exhaust stroke increases. This is because heat is mainly generated during the expansion stroke due to ignition retardation, and part of the energy originally extracted as engine output is thermal energy. This increases the temperature of the gas supplied to the catalyst and activates the catalyst early. Although the ignition retard width Δ 0 re is usually about 10 to 30 ° crank angle, the combustion does not deteriorate, that is, the torque cycle fluctuation of the engine does not become extremely large. It is desirable to take as large a value as possible within the optimal range.

Here, the behavior of the air-fuel mixture in the exhaust stroke in the combustion chamber in the catalyst activation mode will be described with reference to FIG.

FIG. 15 is an explanatory diagram of the behavior of the air-fuel mixture during the exhaust stroke in the control method for the spark ignition engine according to the first embodiment of the present invention. The same reference numerals as in FIGS. 3 and 4 denote the same parts.

In the catalyst activation mode, the ignition timing is retarded, and as shown in FIG. 10, the combustion gas temperature during the exhaust stroke is higher than when the ignition is not retarded. Therefore, as shown in FIG. 15, the high-temperature combustion gas is discharged to the exhaust passage 9 and guided to a three-way catalyst (not shown) provided downstream of the exhaust passage 9. As a result, the temperature of the catalyst is rapidly raised and activated.

Next, in step s155 of FIG. 5, the control unit 25 compares the timer time t with a predetermined catalyst activation required time t2. Returning to 40, the procedure of the catalyst activation mode in which fuel is injected in the exhaust stroke in the next cycle and the ignition timing is retarded is repeated. On the other hand, if t> t2, it is determined that the catalyst has been sufficiently activated, and the operation proceeds to the normal operation mode.

The catalyst activation period t2 is the time required until the catalyst is activated (light-off), and is usually the time required for the catalyst temperature to rise to 200 to 300 ° C. The time t 2 is determined in advance by a preliminary experiment using a test bench or the like.

In the normal operation mode, except when there is a sudden change in the engine load, fuel is injected in the exhaust stroke, and the ignition timing that maximizes fuel efficiency is selected.

In the above description, in the intake valve heating mode, the ignition timing is advanced and the fuel injection timing is set to the intake stroke. However, the fuel injection timing may be set to the exhaust stroke. In other words, in the intake valve heating mode of the present embodiment, by elevating the temperature of the intake valve early by advancing the ignition timing, the fuel vaporization in the subsequent catalyst activation mode and the normal operation mode is promoted. The HC can be reduced at the time of starting. Incidentally, by advancing the ignition timing and setting the fuel injection timing to the intake stroke, the emission can be reduced by about 50% compared to the past. In addition, even if the ignition timing is advanced and the fuel injection timing is set to the exhaust stroke, it is about 30 % Emission can be reduced.

Further, in the above description, it is assumed that after the intake valve heating mode, the operation shifts to the normal operation mode via the catalyst activation mode.However, the catalyst activation mode is omitted, and after the intake valve heating mode, The operation may shift to the normal operation mode. In this case, too, by increasing the temperature of the intake valve early in the intake valve heating mode, it is possible to reduce HC in the subsequent normal operation mode.

In the above description, an example of a multi-port injection (MPI) engine in which a fuel injection valve is provided for each intake pipe has been described. DI) can be applied to institutions. In other words, in the intake valve heating mode, not only the intake valve but also the exhaust valve, the combustion chamber wall surface, the piston crown surface, etc. are quickly heated by the high-temperature combustion gas at the same time, so the DI engine injected fuel into the combustion chamber. When the fuel collides with the intake valve, exhaust valve, combustion chamber wall, and piston crown, these fuels can be vaporized at an early stage, and HC at startup can be reduced.

In the above description, the timing of switching from the intake valve heating mode to the catalyst activation mode is determined based on the elapsed time from the start of the start, but the cooling water temperature detected by the water temperature sensor has reached the predetermined temperature. It may be switched at the time. Alternatively, the temperature may be switched when the temperature reaches a predetermined temperature by using a temperature detected by an intake valve, a combustion chamber wall surface, a sensor for detecting a catalyst temperature, or the like. That is, as shown in Fig. 6, in addition to detecting the temperature of the intake valve at or above the predetermined temperature in advance by measuring it on a test bench and detecting the elapsed time, the intake valve and the combustion chamber wall It can be detected from the engine temperature by a method such as directly measuring the temperature.

As described above, according to the present embodiment, in the intake valve heating mode, HC can be reduced by increasing the temperature of the intake valve early by making the ignition timing advanced.

At this time, HC is further reduced by setting the injection timing to the intake stroke.

On the other hand, in the catalyst activation mode, fuel vaporization is promoted by the heat of the heated intake valve. This reduces wall flow and creates a uniform mixture. As a result, HC in the catalyst activation mode is reduced, and the activation time of the catalyst is shortened by a larger ignition retard.

As described above, according to the present embodiment, emissions at the time of starting the engine can be reduced. 'Moreover, since there is no need to provide a heater or the like for the intake valve, reliability and durability can be improved.

Next, a control method for a spark ignition engine according to the second embodiment of the present invention will be described with reference to FIGS.

The system configuration of the engine control system using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIG. Further, the configuration of the engine using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIGS. 2 and 3. However, since there is a difference in the drive mechanism of the intake valve, this point will be described later with reference to FIGS. 16 and 17. Further, the configuration of the control unit 25 in the engine control system using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIG.

Here, the configuration and operation of the intake valve of the engine using the method for controlling the spark ignition engine according to the present embodiment will be described with reference to FIG. 16 and FIG.

FIG. 16 is a transparent perspective view showing a configuration of an engine using the spark ignition engine control method according to the second embodiment of the present invention. FIG. 17 is an explanatory diagram of the operation of the intake valve of the engine using the control method of the spark ignition engine according to the second embodiment of the present invention. In FIG. 16, the same reference numerals as those in FIG. 2 indicate the same parts.

As shown in FIG. 16, the intake valve 5 is provided with a variable valve mechanism 50. The variable valve mechanism 50 is a so-called phase difference type variable valve mechanism, and is realized by providing a torsion mechanism (not shown) on a rotating shaft (not shown) of a cam for lifting the intake valve 5. Alternatively, a similar variable valve mechanism can be realized by using an electromagnetic valve or a hydraulic valve. The variable valve mechanism 50 can change the opening timing of the intake valve 5 by a control signal input from the control unit 25.

As shown in Fig. 17, there are two patterns of valve opening timing: normal mode and advanced angle mode. In the advance mode, the valve opening timing is advanced compared to the normal mode. is there.

FIG. 18 is a flowchart showing the processing content of the engine start-up processing by the control method of the spark ignition engine according to the second embodiment of the present invention. Note that the same step numbers as those in FIG. 5 indicate the same processing contents.

In the present embodiment, similarly to the processing shown in FIG. 5, an intake valve heating mode and a catalyst activation mode are provided. However, the process in step s122 in the intake valve heating mode is different from the process shown in FIG.

The engine activation process according to the present embodiment is started by the ON of the ignition key in step s100. The control unit 25 sets the internal timer time to 0 in the process of step s110. Next, in step s115, the control unit 25 reads the water temperature detected by the water temperature sensor, and adjusts the water temperature from a predetermined temperature Twl (normally about 50 to 80 ° C). If the value is also high, the mode shifts to the normal operation mode. On the other hand, if the water temperature is lower than Twl, the control unit 25 shifts to the operation control of the intake valve heating mode.

In the intake valve heating mode, in step s120, the control unit 25 calculates the amount of injected fuel.

Next, in step s122, the control unit 25 sets the intake valve lift to the advance mode as shown in FIG. 17 and sets the variable valve mechanism 50 as shown in FIG. Outputs a control signal for setting the advance mode.

Here, the gas behavior immediately before the end of the exhaust stroke in the intake valve heating mode will be described with reference to FIG.

FIG. 19 is an explanatory diagram of the gas behavior immediately before the end of the exhaust stroke in the intake valve heating mode in the control method of the spark ignition engine according to the second embodiment of the present invention. The same reference numerals as those in FIG. 16 indicate the same parts.

In this mode, since the opening timing of the intake valve 5 is advanced with respect to the normal operation, the intake valve 5 opens with the pressure in the combustion chamber 11 higher than the intake passage 2. Therefore, the combustion gas C in the combustion chamber 11 flows into the intake passage 2. Flows into the intake channel 2 The convection and radiant heat transfer from the hot combustion gas C to the intake valve 5 heats the umbrella portion 5 'of the intake valve 5 early.

Next, in step s 1 25 in FIG. 18, the control unit 25 sets the fuel injection timing to the intake stroke, and in the intake stroke of each cylinder, a predetermined amount of fuel is injected into the intake pipe by the fuel injection valve. Inject.

Here, the behavior of gas and fuel spray at the initial stage of the intake stroke in the intake valve heating mode will be described with reference to FIG.

FIG. 20 is an explanatory diagram of the behavior of gas and fuel spray at the initial stage of the intake stroke in the intake valve heating mode in the control method for the spark ignition engine according to the second embodiment of the present invention. The same reference numerals as those in FIG. 16 indicate the same parts.

The fuel spray S injected during the intake stroke is vaporized by the heat transfer from the combustion gas C drawn into the combustion chamber 7 from the intake passage 2. Further, the mist that collides with the umbrella portion 5 ′ of the intake valve 5 is vaporized by receiving heat from the intake valve 5 that has become hot. For this reason, most of the fuel injected in the intake stroke enters the combustion chamber 7 in a vaporized state, and forms a mixture in the combustion chamber 7. As a result, combustion with less generation of a fuel liquid film in the intake valve and the combustion chamber and less HC is realized. In addition, since a uniform mixture is formed by promoting vaporization, stable combustion is realized, and the ignition timing can be greatly retarded. As a result, the exhaust gas temperature becomes higher and the catalyst can be activated in a short time.

Next, in step s135 of FIG. 18, when the elapsed time t from the start of the start exceeds the predetermined time t1, the control unit 25 shifts to the catalyst activation mode. The details of the processing in the catalyst activation mode are the same as those described with reference to FIG. 5. The exhaust stroke injection and the ignition retard control are performed, and the catalyst is activated early. In addition, the intake valve lift at this time is returned to the normal lift mode without advance.

As described above, according to the present embodiment, in the intake valve heating mode, HC can be reduced by increasing the temperature of the intake valve early by advancing the lift timing of the intake valve. it can. In particular, many recent spark ignition engines have been equipped with a variable valve mechanism, and such engines can be adopted without adding hardware. By advancing the lift timing of the intake valve, Since the surface of the intake valve is directly heated by the combustion gas, the surface temperature of the intake valve can quickly rise to a temperature at which fuel can be evaporated.

On the other hand, in the catalyst activation mode, wall heat is reduced by promoting the vaporization of fuel by the heat of the heated intake valve, and a uniform air-fuel mixture is formed. As a result, HC in the catalyst activation mode is reduced, and the activation time of the catalyst is shortened by increasing the ignition retard.

As described above, according to the present embodiment, emissions at the time of starting the engine can be reduced. In addition, since there is no need to provide a heater or the like for the intake valve, reliability and durability can be improved.

Next, a control method for a spark ignition engine according to the third embodiment of the present invention will be described with reference to FIGS.

The system configuration of the engine control system using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIG. Further, the configuration of the engine using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIGS. 2 and 3. However, since there is a difference between the drive mechanisms of the intake valve and the exhaust valve, this point will be described later with reference to FIGS. 21 and 22. Further, the configuration of the control unit 25 in the engine control system using the method for controlling the spark ignition engine according to the present embodiment is the same as that shown in FIG.

Here, the configuration and operation of the intake and exhaust valves of the engine using the control method of the spark ignition engine according to the present embodiment will be described with reference to FIGS.

FIG. 21 is a transparent perspective view showing a configuration of an engine using the spark ignition engine control method according to the third embodiment of the present invention. FIG. 22 is an explanatory diagram of the operation of the exhaust valve of the engine using the control method of the spark ignition engine according to the third embodiment of the present invention. In FIG. 16, the same reference numerals as those in FIG. 2 indicate the same parts.

As shown in FIG. 21, the intake valve 5 is provided with a variable valve mechanism 50, and the exhaust valve 6 is provided with a variable valve mechanism 60. The variable valve mechanism 50 is the same as that described in FIG. The variable valve mechanism 60 is similar to the variable valve mechanism 60. You. The variable valve mechanism 50 can change the opening timing of the intake valve 5 by a control signal input from the control unit 25. Further, the variable valve mechanism 60 can change the opening timing of the exhaust valve 6 according to a control signal input from the control unit 25.

As shown in FIG. 17, the opening timing of the intake valve 5 has two patterns, a normal mode and an advanced mode. In the advance mode, the valve opening timing is advanced compared to the normal mode.

The opening timing of the exhaust valve 6 has two patterns, a normal mode and an advanced angle mode, as shown in FIG. In the advance mode, the valve opening timing is advanced compared to the normal mode.

Next, the processing content of the engine start processing by the control method of the spark ignition engine according to the present embodiment will be described using FIG.

FIG. 23 is a flowchart showing the processing content of the engine start processing by the control method of the spark ignition engine according to the third embodiment of the present invention. Note that the same step numbers as those in FIGS. 5 and 18 indicate the same processing contents.

In the present embodiment, similarly to the processing shown in FIG. 18, an intake valve heating mode and a catalyst activation mode are provided. However, the process of step s142 in the catalyst activation mode is different from the process shown in FIG.

The engine activation process according to the present embodiment is started by the ON of the ignition key in step s100. The control unit 25 sets the internal timer one time to 0 in the process of step s110. Next, in step s115, the control unit 25 reads the water temperature detected by the water temperature sensor, and adjusts the water temperature from a predetermined temperature Twl (normally about 50 to 80 ° C). If the value is also high, the mode shifts to normal operation mode. On the other hand, if the water temperature is lower than Twl, the control unit 25 shifts to the operation control of the intake valve heating mode.

In the intake valve heating mode, in step s120, the control unit 25 calculates the amount of injected fuel. Next, in step s120, the control unit 25 sets the intake valve lift to the advance mode as shown in FIG. 17 and advances the variable valve mechanism 50 as shown in FIG. Output control signal to switch to angular mode You.

Next, in step s125, the control unit 25 sets the fuel injection timing to the intake stroke, and injects a predetermined amount of fuel into the intake pipe by the fuel injection valve during the intake stroke of each cylinder. Next, in step s135, the control unit 25 shifts to the catalyst activation mode when the elapsed time t from the start of the start exceeds the predetermined time t1.

In the catalyst activation mode, in step s140, the control unit 25 injects a predetermined amount of fuel in the exhaust stroke based on the value detected by the crank angle sensor. Next, in step s142, the control unit 25 sets the exhaust valve lift to the advance mode as shown in FIG. 22 and sets the variable valve mechanism 60 as shown in FIG. Outputs a control signal for setting the advance mode. In the catalyst activation mode, by advancing the opening timing of the exhaust valve, in the catalyst activation mode, the combustion gas before complete combustion in the combustion chamber is led to the exhaust pipe. As a result, combustion continues in the exhaust pipe, and the temperature of the combustion gas supplied to the catalyst rises. In addition, the unburned fuel causes a combustion reaction in the catalyst, enabling early activation of the catalyst.

Next, in step s145, the control unit 25 injects a predetermined amount of fuel in the exhaust stroke based on the value detected by the crank angle sensor.

Next, in step s155, the control unit 25 compares the timer time t with a predetermined catalyst activation required time t2, and if t <t2, the control unit 25 Then, in the next cycle, the procedure of the catalyst activation mode for injecting fuel in the exhaust stroke and retarding the ignition timing is repeated. On the other hand, if t> t2, it is determined that the catalyst has been sufficiently activated, and the operation proceeds to the normal operation mode.

As described above, according to the present embodiment, in the intake valve heating mode, HC can be reduced by increasing the temperature of the intake valve early by advancing the lift timing of the intake valve. it can.

At this time, HC is further reduced by setting the injection timing to the intake stroke. On the other hand, in the catalyst activation mode, the activation time of the hornworm medium can be reduced by advancing the opening timing of the exhaust valve.

As described above, according to the present embodiment, emissions at the time of starting the engine can be reduced. In addition, since there is no need to provide the intake valve with a light source, reliability and durability can be improved.

Next, a control method for a spark ignition engine according to a fourth embodiment of the present invention will be described with reference to FIGS.

The system configuration of the engine control system using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIG. Further, the configuration of the engine using the control method of the spark ignition engine according to the present embodiment is the same as that shown in FIGS. 2 and 3. However, since the intake pipe is provided with a swirl control valve, this point will be described later with reference to FIGS. 24 to 26. Further, the configuration of the control unit 25 in the engine control system using the method for controlling a spark ignition engine according to the present embodiment is the same as that shown in FIG.

Here, the configuration and operation of the swirl control valve of the engine using the control method of the spark ignition engine according to the present embodiment will be described with reference to FIGS.

FIG. 24 is a transparent perspective view showing the configuration of an engine using the method for controlling a spark ignition engine according to the fourth embodiment of the present invention. FIG. 25 is a front view showing a configuration of a swirl control valve attached to an engine using the spark ignition engine control method according to the second embodiment of the present invention. FIG. 26 is an explanatory diagram of the operation of a swirl control valve attached to an engine using the control method for a spark ignition engine according to the second embodiment of the present invention. In FIG. 24, the same reference numerals as those in FIG. 2 indicate the same parts.

As shown in FIG. 24, a swirl control valve 30 is provided upstream of the intake passage 2. As shown in FIG. 25, the swirl control valve 30 has a structure in which a plate-shaped valve element 33 is attached to a swirl control valve shaft 31 rotated by a motor 32. The valve element 33 has a configuration having an opening 3 3 ′ at the upper right part thereof. A rotation instruction is given to the motor 32 by a control signal from the control unit 25, and as shown in FIG. 21, the swirl control valve 30 can be switched between fully closed and fully opened. When the load on the engine is large and a large amount of air needs to be introduced into the combustion chamber, the swirl control valve 30 is fully opened. On the other hand, the swirl control valve 30 is fully closed for stable combustion at low and medium loads. At this time, air flows from the opening 3 3 ′ of the valve element 33, but since the cross-sectional area of the opening 3 3 ′ is smaller than the cross-sectional area of the intake passage, high-speed air with high directivity due to the throttle effect is provided. Stream F is generated. This air flow F generates a strong vortex in the combustion chamber. The swirl control valve 30 shown in FIGS. 25 and 26 generates a lateral vortex in the combustion chamber.

Here, a swirl control valve having another configuration will be described with reference to FIGS. 27 and 28. FIG.

FIG. 27 is a front view showing another configuration of the swirl control valve attached to the engine using the spark ignition engine control method according to the second embodiment of the present invention. FIG. 28 is a front view showing another configuration of the swirl control valve attached to the engine using the spark ignition engine control method according to the second embodiment of the present invention. The same reference numerals as those in FIG. 25 indicate the same parts.

As shown in FIG. 27, the flat valve body 33 A constituting the steel control valve 3 OA has a shape capable of blocking the left half of the passage, and has an opening 33 A ′ on the right side thereof. have. When the swirl control valve 3OA is fully closed, a high directivity airflow F with high directivity is generated from the opening 33A 'of the valve body 33A by the throttle effect. This airflow F generates a strong vortex in the combustion chamber. The scale control valve 3OA generates a lateral vortex in the combustion chamber.

As shown in FIG. 28, the plate-shaped valve element 33 B constituting the swirl control valve 30 B has a shape capable of blocking the lower half of the passage, and an opening 33 B ′ have. When the swirl control valve 30B is fully closed, a high-directivity high-speed airflow F is generated from the opening 33B 'of the valve body 33B by the throttle effect. This air flow F generates a strong vortex in the combustion chamber. The swirl control valve 30B generates a vertical vortex in the combustion chamber.

FIG. 29 is an end view of the spark ignition engine control method according to the fourth embodiment of the present invention. It is a flowchart which shows the processing content of a gin activation process. Note that the same step numbers as those in FIG. 5 indicate the same processing contents.

In the present embodiment, similarly to the processing shown in FIG. 5, an intake valve heating mode and a catalyst activation mode are provided. However, the processing in step s124 in the intake valve heating mode and the processing in step s144 in the catalyst activation mode are different from the processing shown in FIG.

The engine activation process according to the present embodiment is started by the ON of the ignition key in step s100. The control unit 25 sets the internal timer one time to 0 in the process of step s110. Next, in step s115, the control unit 25 reads the water temperature detected by the water temperature sensor, and adjusts the water temperature from a predetermined temperature Twl (normally about 50 to 80 ° C). If the value is also high, the mode shifts to the normal operation mode. On the other hand, if the water temperature is lower than Twl, the control unit 25 shifts to the operation control of the intake valve heating mode.

Next, in step s124, the control unit 25 sends a control signal for opening the swirl control valve 30 to the swirl control valve 30 so that the swirl control valve 30 is opened. Here, as the swirl control valve to be controlled, swirl control valves 3 OA and 30 B shown in FIGS. 27 and 28 may be used instead of the swirl control valve 30. .

Here, the fuel and gas behavior during the intake stroke in the intake valve heating mode will be described with reference to FIG.

FIG. 30 is an explanatory diagram of the fuel and gas behavior in the intake stroke in the intake valve heating mode in the spark ignition engine control method according to the fourth embodiment of the present invention. The same reference numerals as those in FIG. 24 indicate the same parts.

In the intake valve heating mode, since the swirl control valve 30 is open, air flows through the entire cutting surface of the intake passage 2. Therefore, the speed of the air in the intake passage 2 is relatively low. Therefore, the fuel spray S injected into the intake passage 2 during the intake stroke is less affected by the air flow F. Specifically, intake channel 2 The fuel spray S does not deflect or disperse due to the air flow F inside, and the fuel spray S is introduced into the combustion chamber 11 through the opening of the intake valve 5.

Here, the behavior of fuel and gas when the swirl control valve is closed during the intake stroke will be described for reference with reference to FIG.

Figure 31 is an explanatory diagram of the fuel and gas behavior during the intake stroke as a reference example. The same reference numerals as those in FIG. 24 indicate the same parts.

When swirl control valve 30 is closed during intake stroke injection, air F accelerated by swirl control valve 30 deflects fuel spray S and forms liquid film L on the wall of intake pipe 18. . Due to the formation of the liquid film L, HC discharged from the engine increases. In contrast, as shown in FIG. 30, in the present embodiment, in the intake valve heating mode, the swirl control valve 30 is opened during the intake stroke injection to suppress the deflection and dispersion of the spray, HC can be reduced.

Next, in step s125 of FIG. 29, the control unit 25 sets the fuel injection timing to the intake stroke, and sets a predetermined amount of fuel into the intake pipe by the fuel injection valve during the intake stroke of each cylinder. Inject.

Next, in step s135, the control unit 25 shifts to the catalyst activation mode when the elapsed time t from the start has exceeded the predetermined time t1. At s140, the control unit 25 injects a predetermined amount of fuel in the exhaust stroke based on the value detected by the crank angle sensor. Next, in step s144, the control unit 25 sends a control signal for closing the swirl control valve 30 to the swirl control valve 30, and the swirl control valve closes.

Here, the fuel and gas behavior during the intake stroke in the catalyst activation mode will be described with reference to FIG.

FIG. 32 is an explanatory diagram of the fuel and gas behavior during the intake stroke in the catalyst activation mode in the spark ignition engine control method according to the fourth embodiment of the present invention. The same reference numerals as those in FIG. 24 indicate the same parts. In the catalyst activation mode, the swirl control valve 30 is closed, and a vertical vortex TF is formed in the combustion chamber 11. The fuel injected during the exhaust stroke receives heat from the umbrella section 5 ′ of the exhaust valve 5, which is heated by the operation in the intake valve heating mode performed before the catalyst activation mode, and is vaporized and burned Room 1 is led to 1. In the combustion chamber 11, mixing of the vaporized fuel and air is promoted by the vertical vortex TF, and strong turbulence is generated in the gas by the vertical vortex TF. This promotion of mixing and enhanced turbulence stabilizes combustion in the catalyst activation mode. This makes it possible to operate with a large ignition retard, which tends to cause unstable combustion, and to activate the catalyst in a shorter period of time. In addition, the combustion stabilization effect enables operation with a leaner air-fuel mixture, so it is possible to reduce the amount of fuel increase at startup and reduce HC.

Next, in step s150 of FIG. 29, the control unit 25 ignites the ignition timing on the retard side with respect to the ignition timing at which the fuel efficiency is the best. As shown in FIG. 10, when the ignition timing is retarded from the best fuel consumption timing, the gas temperature in the exhaust stroke increases. Next, in step s155, the control unit 25 compares the timer time t with a predetermined catalyst activation required time t2, and if t <t2, the control unit 25 Then, in the next cycle, the procedure of the catalyst activation mode for injecting fuel in the exhaust stroke and retarding the ignition timing is repeated. On the other hand, if t> t2, it is determined that the catalyst has been sufficiently activated, and the operation proceeds to the normal operation mode.

In the above description, the operation of the swirl control valve is fully opened in the intake valve heating mode and fully closed in the catalyst activation mode.However, the opening of the swirl control valve in the intake valve heating mode is determined by the catalyst activation. It may be set to an intermediate opening between full open and fully closed, as long as it is larger than the opening of the swirl control valve in the normalization mode.

As described above, according to the present embodiment, in the intake valve heating mode, HC can be reduced by closing the swirl control valve.

As described above, according to the present embodiment, emissions at the time of starting the engine can be reduced. In addition, since there is no need to provide a heater or the like for the intake valve, reliability and durability can be improved. INDUSTRIAL APPLICABILITY According to the present invention, emissions at the time of starting can be reduced, and reliability and durability can be improved.

Claims

The scope of the claims

1. In a spark ignition engine having a fuel injection valve (4),

A method for controlling a spark ignition engine, characterized in that, when the engine temperature is lower than a predetermined temperature, the ignition timing is advanced from an ignition timing at which fuel efficiency is best.

2. The method for controlling a spark ignition engine according to claim 1,

A method for controlling a spark ignition engine, characterized in that fuel is injected in an intake stroke when the engine temperature is lower than a predetermined temperature.

3. The method for controlling a spark ignition engine according to claim 1,

When the engine temperature is higher than a predetermined temperature and the catalyst is not activated, the fuel injection timing is set to an exhaust stroke, and the ignition timing is retarded from the ignition timing at which fuel efficiency is best. Control method.

4. In a spark ignition engine having a fuel injection valve,

A means (50) for changing the opening timing of the intake valve is provided,

A method for controlling a spark ignition engine, characterized in that when the engine temperature is lower than a predetermined temperature, the valve opening timing of the intake valve is advanced from a normal valve opening time.

5. The method for controlling a spark ignition engine according to claim 4,

6. The control method for a spark ignition engine according to claim 4,

7. The method for controlling a spark ignition engine according to claim 4,

Means (60) for changing the opening timing of the exhaust valve;

A control method for a spark ignition engine, characterized in that when an engine temperature is higher than a predetermined temperature and a catalyst is inactive, the opening timing of an exhaust valve is retarded more than usual.

8. In a spark ignition engine having a fuel injection valve,

A swirl control valve (30) that generates swirl by changing the flow path step area of the intake pipe is provided. When the engine temperature is lower than a predetermined temperature, the swirl strength generated by the swirl control valve (30) is reduced. A method for controlling a spark ignition engine, characterized in that the engine temperature is weakened when the engine temperature is higher than a predetermined temperature.

9. The method for controlling a spark ignition engine according to claim 8,

10. The method for controlling a spark ignition engine according to claim 8,