JPH11280532A - Control device of engine for automobible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize smooth starting of an engine, by adjusting timing of combustion so as to suppress a fluctuation of torque while performing good ignition and combustion at starting time by effectively utilizing purge gas, in the engine for an automobile. SOLUTION: In an engine for an automobile provided with an injector 18 injecting fuel directly to a combustion chamber and a purge device having a canister, purge valve 38, etc., an engine controlling ECU60 comprises a start discrimination means 70, means 71 deciding an adsorption amount of the canister, purge control means 72 making a purge gas introducing condition when the adsorption amount is large decided in the beginning of starting of the engine, and a combustion control means 73 performing starting initial combustion adjusting control, injecting fuel from the injector 18 in a range of expansion stroke from a compression stroke latter period when the purge gas introducing condition is provided in the beginning of starting of the engine, and making ignition timing after the top dead center of compression.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling purge and fuel injection so that an automobile engine having an injector for directly injecting fuel into a combustion chamber and having a purging device performs a smooth engine start. It is about.

[0002]

[0003]

2. Description of the Related Art Conventionally, in a spark ignition type engine (gasoline engine) in which ignition is performed by a spark plug, an injector having a tip facing a combustion chamber is provided so as to inject fuel directly into the combustion chamber, and a low rotation speed low 2. Description of the Related Art There is known an in-cylinder injection engine in which a fuel is injected from an injector in a compression stroke in a specific operation region such as a load so that a combustible air-fuel mixture is unevenly distributed in the vicinity of an ignition plug to perform stratified combustion to improve fuel efficiency. ing.

There is also known an engine equipped with a purge device that adsorbs fuel vapor generated in a fuel tank or the like to a canister and guides the fuel vapor from the canister to an intake passage via a purge valve. In an engine equipped with this purging device, a purge gas is introduced into an intake passage during a specific operation of the engine and supplied to a combustion chamber for combustion. In some cases, it may not be possible to sufficiently purify this against the increase in the amount of adsorption.

For example, in a hybrid vehicle equipped with an engine and a motor, the engine of which is intermittently operated while the vehicle is operating, the engine is often in an idle state even while the vehicle is running. As the amount of adsorption of the canister increases, a situation may occur in which the canister cannot be purged.

As a countermeasure against such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 6-233410, an electric motor in which a vehicle is driven by a motor and a generator for supplying power is driven by an engine. In an automobile, the amount of fuel vapor is detected based on the detection of the weight of the canister, etc.
In some cases, the engine is driven when the amount of evaporated fuel increases, and the engine is stopped when the amount of evaporated fuel decreases after driving the engine. Also, JP-A-8-30
As shown in Japanese Patent Application Publication No. 8019, in an electric vehicle in which a vehicle is driven by a motor and a generator for supplying electric power is driven by an engine, the engine is charged for charging when the stored amount of the battery is reduced. In addition to driving, the engine is driven with a smaller load than the driving for charging when the adsorption amount of the canister becomes large.

Although all of the publications described in the above publications use an engine for driving a generator, in addition to this type of hybrid vehicle, the engine is used for assisting the driving of the vehicle. It is also known that the engine is started to assist the output when an increase in output is requested during driving of the vehicle driven by a motor, and the engine is intermittent even in such a hybrid vehicle. The canister is easily operated and the adsorbed amount of the canister tends to increase when the engine is at rest, and a countermeasure is required.

[0008]

In the prior arts disclosed in the above publications, the engine is operated merely for purging when the amount of adsorption of the canister increases, but the evaporated fuel is not vaporized. It is desirable to increase the chance of purging as much as possible and to effectively use the purge gas in order to improve the operation performance and the like, since it has characteristics of being excellent and having excellent ignitability.

In general, in a four-stroke engine, after an air-fuel mixture is supplied to a combustion chamber (for example, fuel is injected from an injector), ignition is performed immediately before a top dead center of a compression stroke. Immediately after the dead center, a large torque is generated due to the pressure rise due to combustion, but in the latter half of the previous compression stroke, a negative torque is generated with the increase in compression pressure, and this negative torque and positive torque are temporally different. In this case, torque fluctuation occurs. In particular, at the time of cranking in the early stage of starting when the engine speed is extremely low, the time interval between the negative torque and the positive torque becomes long and the rotational inertia is small, so that the torque fluctuation increases, and this torque fluctuation causes engine vibration.

[0010] Such engine vibration due to torque fluctuation at the time of starting the engine is not preferable in terms of feeling and the like. In particular, in a hybrid vehicle in which the engine and the motor are used separately and the engine is operated intermittently while the vehicle is running, the engine may be started regardless of the driver's intention during driving or the like. The engine vibration gives the driver a sense of incongruity and worsens the feeling.

In order to suppress the torque fluctuation in the early stage of the engine start, a method of lowering the peak of the positive torque by delaying the combustion timing is considered. However, mere adjustment of the combustion timing so as to deviate causes poor ignitability and makes it difficult to perform good combustion.

In view of such circumstances, the present invention satisfies the demand for increasing the chance of purging to eliminate the increase in the amount of adsorption of the canister and the demand for reducing engine vibration at the initial stage of engine start. It is an object of the present invention to provide a start control device for an automobile engine that can effectively utilize ignition and perform ignition and combustion at the time of engine start, suppress torque fluctuations, and reduce engine vibration.

[0013]

According to a first aspect of the present invention, there is provided an injector for directly injecting fuel into a combustion chamber, and guides fuel vapor from a canister to an intake passage via a purge valve. In an automobile engine equipped with a purge device, start determination means for determining when the engine is started, adsorption amount determination means for determining the amount of fuel vapor adsorbed by the canister, and determination by the start determination means and determination by the adsorption amount determination means. According to the above, when it is determined that the amount of adsorbed fuel vapor is large at the early stage of the engine start, the purge valve is opened and the purge gas is introduced by the purge control unit at the early stage of the engine when the purge valve is opened. The fuel is injected from the injector in the range from the late stage of the compression stroke to the expansion stroke. Allowed, and, in which a combustion control means for starting initial combustion adjustment control to the compression top dead center after the ignition timing.

According to this device, the ignition timing and the combustion timing of the air-fuel mixture by the fuel injection from the injector are delayed as compared with a normal setting at the initial stage of engine start where torque fluctuations are likely to occur, so that the torque peak due to combustion is reduced. Thus, torque fluctuation is suppressed. In addition, ignition and combustion are favorably performed by introducing a purge gas having a good vaporization state.

In the present invention, the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means are performed during a period in which the engine is in the cranking state at the beginning of the engine start, and the start is completed after the cranking. If the fuel injection timing is changed before the late stage of the compression stroke and the ignition timing is changed before the compression top dead center during the rotation speed increase up to (claim 2), torque fluctuation is suppressed during cranking. At the same time, the torque is increased during the rotation speed increase from the cranking to the completion of the start as compared with the initial stage of the start.

It is preferable that the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means be performed when the engine is warm (claim 3). Then, the purge gas introduction control is effectively performed in a state where the introduction of the purge gas is reliable and the combustion stability is high.

Further, when the device of the present invention is applied to a hybrid vehicle having an engine and a motor, the engine being operated intermittently while the vehicle is operating, the evaporative fuel which tends to accumulate in the canister during an engine halt or the like is removed in the early stage of engine start. In addition to being able to be used effectively, even when the engine is started irrespective of the driver's intention during traveling or the like, the feeling of discomfort given to the driver can be reduced, which is effective. In this case, if the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means are performed at the time of engine start except for engine operation due to rapid acceleration, the engine is operated at rapid acceleration. In this case, priority is given to securing torque for rapid acceleration, and control for suppressing torque fluctuation is effectively performed at other times when the engine is started.

[0018] Further, a stratifying means for unevenly distributing the air-fuel mixture around the spark plug when fuel is injected from the injector in the compression stroke is provided, so that stratified combustion is performed by injecting the fuel in the compression stroke during a specific operation. At the same time, ignition and fuel injection are performed during the expansion stroke as initial combustion adjustment control by the combustion control means at the initial stage of engine start, and the purge gas is introduced by the purge control means for at least a predetermined period corresponding to several cycles from the start of cranking. It is preferable to perform control (claim 5).

In this way, during a predetermined period from the start of cranking, the peak of torque due to combustion is reduced by performing the expansion stroke of ignition and fuel injection, thereby suppressing torque fluctuation. In addition, while ignition is favorably performed during stratified combustion by the compression stroke injection, when the engine is started, the ignition timing and the fuel injection timing are shifted to the expansion stroke, so that the stratification degree tends to decrease and the ignitability tends to deteriorate. Although this occurs, it is compensated by supplying a purge gas having good ignitability.

According to a sixth aspect of the present invention, there is provided a hybrid vehicle having an electric drive motor and an engine, wherein the engine is started to assist the output when an increase in output is requested during vehicle running by the motor drive. An injector for directly injecting fuel into the chamber, a stratification means for unevenly distributing an air-fuel mixture around a spark plug when fuel is injected from the injector in a compression stroke, and a purge for guiding evaporative fuel from a canister to an intake passage via a purge valve A start determining means for determining when the engine is started, and performing ignition and fuel injection during an expansion stroke as initial engine start combustion adjustment control according to the determination by the start determining means. Combustion control means for controlling the purge valve for at least a predetermined period corresponding to several cycles from the start of cranking. The open is obtained and a purge control unit for a purge gas introduction state.

According to the present invention, in the above-mentioned hybrid vehicle, the engine includes the injector for directly injecting fuel into the combustion chamber and the stratifying means, whereby stratified combustion can be performed depending on the operating condition, and ignition and fuel are started when the engine is started. Since the injection is performed in the expansion stroke, torque fluctuation is suppressed, engine vibration is reduced, and
The tendency for the ignitability to deteriorate due to the decrease in the degree of stratification is compensated for by supplying a purge gas having good ignitability.

According to the fifth or sixth aspect of the present invention, when the engine is warm, the introduction of the purge gas is temporarily stopped after a lapse of a predetermined period corresponding to several cycles from the start of cranking, and before the ignition timing. It is preferable to change the fuel injection timing so as to start the fuel injection, and to keep the purge gas introduction stopped state until the start of the engine thereafter (claim 7).

With this arrangement, when the engine is warm, the combustion chamber temperature increases after a lapse of a predetermined period from the start of cranking, so that the combustibility is enhanced. When the rotation speed increases until the start is completed, it is possible to prevent a situation in which the combustibility is excessively increased by the supply of the purge gas and a sudden increase in torque is caused.

Further, there is provided a valve timing variable means for changing the closing timing of the intake valve, and when the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means are performed at the initial stage of the engine start. Preferably, the closing timing of the intake valve is set earlier than the intake bottom dead center (claim 8).

With this configuration, the effective compression ratio is reduced, so that the negative torque generated by the compression pressure in the compression stroke is reduced, thereby also suppressing the fluctuation in torque during cranking and the like.

The fuel pressure of the fuel supplied from the fuel pump and injected from the injector can be changed between a predetermined high pressure and a predetermined low pressure lower than the predetermined high pressure. During normal operation, the fuel pressure is adjusted to maintain the predetermined high pressure. And fuel pressure changing means for changing the fuel pressure to the predetermined low pressure when the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means are performed in the initial stage of engine start. (Claim 9)
Is preferred.

In this way, when the purge gas is introduced at the initial stage of engine start, the fuel injection amount is reduced by the amount of the purge gas. Therefore, the pulse width (injection time) becomes extremely small in high pressure injection, and it is difficult to control the fuel injection amount. On the other hand, low-pressure injection is advantageous in controlling the amount of fuel injection because the pulse width is larger than that of high-pressure injection, and on the other hand, low-pressure injection is more finely divided than high-pressure injection. However, the ignitability is disadvantageous to the ignitability, but the ignitability is ensured by the purge gas.

According to a tenth aspect of the present invention, an injector for directly injecting fuel into a combustion chamber, and a fuel pressure of fuel supplied from a fuel pump and injected from the injector can be changed to a predetermined high pressure and a predetermined low pressure lower than the predetermined high pressure. In an automobile engine including a fuel pressure adjusting means for adjusting the pressure to be maintained at the predetermined high pressure during the normal operation and a purge device for guiding the fuel vapor from the canister to the intake passage via a purge valve, it is determined whether the engine is started. It is determined that the amount of adsorbed evaporative fuel is large at the beginning of engine start according to the start judging means, the adsorbed amount judging means for judging the adsorbed amount of evaporated fuel of the canister, and the judgment of the start judging means and the judgment of the adsorbed amount judgment means. Purge control means for opening the purge valve and introducing a purge gas when the engine is started. When there is a purge gas introduced state by di control unit, in which the fuel pressure of the fuel injected from the injector and a fuel pressure changing means for changing the predetermined low pressure.

In this manner, the purge is performed when the amount of fuel vapor adsorbed by the canister is large in the early stage of the engine start, and the purge gas is used for improving the combustibility at the start. Then, with the introduction of the purge gas, the fuel injection amount is reduced by that much, but at this time it is advantageous to control the fuel injection amount because the pulse width is larger than that of the high pressure injection due to the low pressure injection, On the other hand,
In the case of low-pressure injection, the ignitability is ensured by the purge gas against the tendency that the atomization of the fuel becomes worse and the ignitability becomes disadvantageous as compared with the high-pressure injection.

It is preferable that the purge control means performs the purge gas introduction control at an early stage of engine start when the engine is warm.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the overall structure of a direct injection engine to which the present invention is applied. In this figure, an engine body 1 has a plurality of cylinders,
It has cylinders 2a to 2d (see FIG. 2), and in each of the cylinders, a combustion chamber 5 is formed above a piston 4 inserted into a cylinder bore. An intake port 7 and an exhaust port 8 are opened in the combustion chamber 5, and these ports 7, 8 are opened and closed by an intake valve 9 and an exhaust valve 10, respectively.

The intake valve 9 and the exhaust valve 10 are opened and closed by a valve mechanism including camshafts 11 and 12 and the like. The valve mechanism for the intake valve 9 is provided with a variable valve timing device 13 that can change the opening / closing timing of the intake valve 9.

At the center of the combustion chamber 5, a spark plug 15
Is disposed, and the tip of the plug faces the combustion chamber 5. This ignition plug 15 is connected to an ignition coil 16.

The front end of the injector 18 faces the combustion chamber 5 from the side, and fuel is directly injected from the injector 18 into the combustion chamber 5. The injector 18 of each cylinder is connected to the delivery pipe 21 of the fuel circuit 20. The fuel circuit 20 includes a fuel supply passage 22 and a return passage 23 connected to the delivery pipe 21, and a fuel pump 25, filters 26 and 27, and a high-pressure fuel pump between the fuel tank 24 and the fuel supply passage 22. 28, a high pressure side pressure regulator 29 and a low pressure side pressure regulator 30 are provided between the return passage 23 and the fuel tank 24, and a passage (not shown) that bypasses the high pressure side pressure regulator 29 is provided. ) And a bypass valve 31 for opening and closing this passage.

The bypass valve 31, the high-pressure side pressure regulator 29 and the low-pressure side pressure regulator 30 constitute a fuel pressure adjusting means.
The operation of 1 makes it possible to change the fuel pressure. That is, when the bypass valve 31 is closed while the high-pressure fuel pump 28 is operating, the fuel pressure is adjusted to a predetermined high pressure by the pressure adjusting operation of the high-pressure side pressure regulator 29, and the bypass valve 31 is opened. In such a case, the high-pressure side pressure regulator 29 does not substantially function, and the fuel pressure is adjusted to a predetermined low pressure by the pressure adjusting operation of the low-pressure side pressure regulator 30.

A purge device 33 is provided between the fuel tank 24 and the intake passage 40 of the engine. The purging device 33 includes a canister 3 that adsorbs fuel vapor.
4 and a check valve 3 for evaporating fuel in the fuel tank 24.
6 and a purge passage 3 connected between the canister 34 and the intake passage 40.
7 and a purge valve 38 provided in the purge passage. When the purge valve 38 is opened, purge gas (evaporated fuel) is introduced from the canister 34 into the intake passage 40.

The engine body 1 has the intake passage 4
0 and the exhaust passage 41 are connected. The intake passage 40
Is provided with an air cleaner 43, an air flow sensor 44, a throttle valve 45 driven by a motor 46, and a surge tank 47 in this order from the upstream side. A throttle opening sensor 48 for detecting the opening of the throttle valve 45 is provided. Further, an ISC passage 50 that bypasses the throttle valve 45 is provided. The ISC passage 50 is provided with an ISC valve 51 that controls an air flow rate in this passage.

An independent intake passage 53 for each cylinder is provided downstream of the surge tank 47, and each independent intake passage 53 communicates with the intake port 7 of each cylinder. A swirl control valve 54 is provided in each independent intake passage 53. The swirl control valve 54 is opened and closed by being driven by an actuator 55 such as a step motor, and the opening and closing operation controls the intake swirl. ing. The swirl control valve 54 serves as a stratified combustion means for unevenly distributing the air-fuel mixture around the spark plug when fuel is injected from the injector 18 in the compression stroke.

On the other hand, in the exhaust passage 41, the air-fuel ratio is detected by detecting the oxygen concentration in the exhaust gas.
_Two sensors 57 are provided, and an exhaust gas purifying catalyst 58 is provided downstream thereof.

Reference numeral 60 denotes a control unit (ECU) for controlling the engine. The ECU 60 receives the detection signals a, b, and c from the air flow sensor 44, the throttle opening sensor 48, and the O ₂ sensor 57, and receives a signal from the distributor 61 linked to the camshaft 12 to detect the engine speed. Angle signal d and cylinder discrimination signal e are input, an accelerator opening sensor 62 for detecting an accelerator opening (accelerator pedal depression amount), an intake air temperature sensor 63 for detecting a temperature of intake air,
Detection signals f, g, and h from a water temperature sensor 64 and the like for detecting the temperature of the engine cooling water are also input.

Also, the ECU 1 sends the injector 1
A signal j for controlling fuel injection is output to the ignition coil 16 via an injector drive unit 66, a signal k for controlling ignition timing is output to the ignition coil 16, and a throttle valve driving motor 46 is output to the throttle valve driving motor 46. A signal 1 for controlling the throttle opening is output via the drive unit 67, a signal m for controlling the ISC valve 51, a signal n for controlling the bypass valve 31 of the fuel circuit, a signal o for controlling the variable valve timing device 13, and A signal p for controlling the purge valve 38 is also output.

The device of the present invention is effectively applied to a hybrid vehicle using both an engine and a motor. FIG. 2 shows an example of the hybrid system.

In this figure, a torque converter 71 on the input side of the continuously variable transmission 70 is connected to the output shaft of the engine body 1, while the output side of the continuously variable transmission 70 is connected to the axle via the final reduction gear 72. 73 and a motor / generator 74 are connected. An alternator 7 is provided on the front end side of the output shaft of the engine body 1 via a belt 75 or the like.
6 are connected. The motor / generator 74 and the alternator 76 are connected to a battery 79 via inverters 77 and 78.

A controller for controlling the hybrid system (ECU 60 in FIG. 1 or another controller not shown) controls the hybrid system in accordance with the driving state of the vehicle.
The engine and the motor / generator 74 are selectively used for driving the vehicle, and the engine is intermittently driven during the operation of the vehicle. For example, the vehicle is driven by a motor, and at the time of low-speed running, the engine is stopped, and when an increase in output is requested, the engine is started and assisted in output.

FIG. 3 shows a functional configuration of the ECU 60. As shown in FIG.
0, functionally includes an adsorption amount determination unit 71, a purge control unit 72, and a combustion control unit 73.

The start determining means 70 determines the start of the engine based on information from a controller for controlling the hybrid system. Further, the adsorption amount determining means 71
Determines the amount of fuel vapor adsorbed by the canister 34.
Various methods for determining the amount of adsorbed fuel vapor have been conventionally proposed, and are not limited by the present invention.
When the purge is performed while the air-fuel ratio feedback control based on the output of the O ₂ sensor 57 is being performed during the engine operation, the purge gas introduction amount is obtained based on the change in the air-fuel ratio feedback correction coefficient, and the learning is performed. Since the value is added to the control, the amount of adsorbed fuel vapor is estimated based on the learned value. However, the determination to be made when the engine is started from a stopped state is that the evaporated fuel adsorption amount is estimated based on a learning value obtained and stored by feedback control during the previous engine operation (when the engine is operating before the stop). Good. It should be noted that the adsorption amount of the canister may be detected by a sensor.

The purge control means 72 responds to the judgment of the start judgment means 70 and the judgment of the adsorption amount judgment means 71,
When it is determined that the amount of adsorbed fuel vapor is large at the beginning of the engine start, the purge valve 38 is opened to control the purge gas to be introduced. Further, when the purge control means 72 is in a purge gas introduction state at the initial stage of engine start, the combustion control means 73
Fuel is injected from the injector within the range from the latter half of the compression stroke to the expansion stroke, and the ignition timing is controlled so as to be after the compression top dead center.

In addition, when the purge gas introduction control by the purge control means 72 and the initial combustion adjustment control by the combustion control means 73 are performed at the initial stage of engine start, the bypass valve 31 of the fuel circuit 20 is controlled.
May be provided to change the fuel pressure to the predetermined low pressure by controlling the fuel pressure. Further, when the purge gas introduction control by the purge control means 72 and the initial combustion adjustment control by the combustion control means 73 are performed in the early stage of the engine start, the closing timing of the intake valve 9 is set earlier than the intake bottom dead center. Means 75 for controlling the variable valve timing device (VVT) 13
May be provided.

FIG. 4 is a flowchart showing an example of the starting control performed by the ECU 60. The process shown in this flowchart is started, for example, when the engine start is started when a predetermined engine operating condition is satisfied while the hybrid vehicle is operating, for example. The control of the hybrid system including the determination of the engine operating conditions and the control of the operation and stop of the engine corresponding thereto, and the determination of the motor operating conditions and the control of the operation and stop of the motor corresponding thereto are performed by different types of illustration other than those shown in FIG. This is performed by a control routine.

When the start of the engine is started, first, in step S1, the adsorption amount of the canister 34 is larger than a predetermined value, for example, based on the purge learning value in the air-fuel ratio feedback control during the previous engine operation as described above. Is determined. If the suction amount is large, the timer is set to a predetermined time TM1 in step S2 to perform the purge for a predetermined period from the start of cranking, and then the process proceeds to step S3. The value of this timer decreases over time. When the amount of adsorption is small, the process directly proceeds to step S3.

In step S3, the engine speed ne obtained from the crank angle signal, the accelerator opening sensor 62
Is read, and the water temperature Tw detected by the water temperature sensor 64 is read. Subsequently, in step S4, it is determined whether or not the engine speed ne is higher than the first set speed N1. First set rotation speed N
1 is a rotation speed slightly higher than the cranking rotation speed (for example, 300 rpm).
When the determination of No. 4 is NO, the engine is in a cranking state, and when this determination is YES, it means that the engine speed is higher than the cranking state.

If the determination in step S4 is NO (cranking state), it is determined in step S5 whether the timer has reached 0. If the timer is not 0, that is, if it is within the predetermined time from the start of cranking, the purge control means 72 controls the purge control means 72 to turn on the purge (open the purge valve 34) in step S6. Further, the pulse width for determining the fuel injection amount is calculated (step S
7), setting of the injection timing (Step S8), and setting of the ignition timing (Step S9). In this case, the injection timing and the ignition timing are set as shown by the solid lines in FIG. That is, the ignition timing IgA is set to be after the compression top dead center (TDC), and the fuel injection timing injA is set to be during the expansion stroke after the ignition timing IgA.

When it is determined in step S5 that the timer has reached 0, that is, after a predetermined time has elapsed from the start of cranking, the purge is turned off in step S10.
(Purge valve 34 is closed), and the process proceeds to step S12 to be described later. Since the low-speed low-load region is a stratified region, the process proceeds to step S13 to be described below to be in the stratification mode.

If it is determined in step S4 that the engine speed ne is higher than the first set speed N1,
In step S11, it is determined whether or not the water temperature T _W is during a warm period higher than the set temperature T1. If it is warm, the stratified mode is set (step S13), and if not, the stratified mode is set (step S1).
4).

Here, the stratified region means an operation region suitable for performing stratified combustion. For example, a predetermined operation region on the low rotation speed and low load side is set in advance as the stratified region. The stratified mode is a mode in which fuel is injected from an injector in a compression stroke to control fuel injection timing and ignition timing so that ignition is performed in a state where an air-fuel mixture is unevenly distributed near an ignition plug. In this mode, the fuel is injected from the injectors during the intake stroke, and the fuel injection timing and the ignition timing are controlled so that the fuel is uniformly diffused throughout the combustion chamber and the ignition is performed. In the stratified mode or the uniform mode, the ignition timing is set before the top dead center as in the case of this type of general engine.

[0057] When it water temperature T _W in step S11 is time between the set temperature T1 or less cold is determined, whether the timer is "0" is determined in step S15, not the timer is "0" If it is, in step S16, it is determined whether the engine speed ne is higher than the second set speed N2. The second set rotation speed N2 is a rotation speed close to the idle rotation speed (for example, about 600 rpm).

When it is determined in step S16 that the rotation speed is equal to or lower than the second set rotation speed N2, the purge O is determined in step S17.
In step S13, the mode is set to the stratified mode. When it is determined that the rotation speed is higher than the second set rotation speed N2, the mode is set to the uniform mode in step S18.

If the timer is determined to be "0" in step S15, the purge is turned off in step S19, and the process proceeds to step S18 to set the uniform mode.

Setting of pulse width, injection timing and ignition timing in steps S7 to S9, or steps S13 and S1
After setting the mode in any one of S4 and S18, fuel injection and ignition are executed in step S20 according to the settings.

The operation of the apparatus of the present embodiment as described above is as follows.
Next, a description will be given.

When starting the engine, the canister 3
In the case where the amount of adsorption of No. 4 is large, the purge valve 38 is opened and the purge is introduced at the initial stage of the cranking when the engine speed is lower than the first set speed N1, and is indicated by a solid line in FIG. Thus, ignition (IgA) is performed after the compression top dead center, and fuel is injected (injA) from the injector into the combustion chamber during the subsequent expansion stroke.

In such a control state, at the ignition timing after the compression top dead center, the purge gas in the combustion chamber is ignited and burned, and this becomes the kind of ignition, and the air-fuel mixture is burnt by the subsequent fuel injection. In this case, the ignition timing is later than the ignition timing in normal operation (before compression top dead center), and fuel is injected during the subsequent expansion stroke, and combustion of the main mixture by this fuel injection is performed in normal operation. By being greatly delayed as compared with the time, the torque peak is reduced. For this reason, the torque fluctuation in the initial stage of starting is reduced.

Further, a multi-cylinder engine (generally a four-cylinder engine) in which the latter part of the expansion stroke of some cylinders overlaps the compression stroke of other cylinders.
In a four-stroke engine (cylinder or more), if the combustion is performed during the expansion stroke as described above, the positive torque resulting therefrom also has the effect of canceling the negative torque generated in the cylinder in the compression stroke.

This operation will be described in detail.
In the case of a four-cylinder engine, as shown in FIG. 6, the intake, compression, expansion, and exhaust strokes of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder are shifted 180 ° in crank angle in this order. By being sequentially performed, the positive torque due to the combustion in the expansion stroke of the first cylinder cancels the negative torque in the compression stroke of the third cylinder overlapping with the first cylinder. Similarly, the expansion stroke of the third cylinder and the compression stroke of the fourth cylinder, the expansion stroke of the fourth cylinder and the compression stroke of the second cylinder, and the expansion stroke of the second cylinder and the compression stroke of the first cylinder overlap each other. Even during the period, the torque given to the cylinder in the expansion stroke negates the negative torque in the cylinder in the compression stroke.

By these actions, the torque fluctuation at the initial stage of the start and the engine vibration accompanying it are reduced, and the feeling is improved. In particular, in a hybrid vehicle as shown in FIG. 2, the engine is started irrespective of the driver's will during the transition from the motor operation state to the engine operation state even during driving, etc. Also, a situation in which the driver feels strange due to torque fluctuation is prevented.

By adjusting the combustion in this way, torque fluctuations are suppressed, while ignition and combustion tend to deteriorate if ignition and combustion are delayed. Exists, and the purge gas is well vaporized and has good ignitability, so that ignition and combustion are performed well while the combustion of the main air-fuel mixture is delayed. While the purge gas is effectively used for improving the combustibility at the time of starting, the purge canister 3
4 is reduced.

When the purge is performed for a predetermined time, the canister 3
4 is expected to decrease, the purge O
FF is set. Purge OFF during cranking
If so, the mode is changed to the stratified combustion mode, fuel is injected (injB) in the compression stroke as shown by the broken line in FIG. 5, and ignition (IgB) is performed before the compression top dead center. When the purge is turned off during cranking, instead of the stratified mode as described above, the ignition timing is set to the ignition timing after the compression top dead center in order to maintain the torque fluctuation suppressing action. Alternatively, the fuel injection may be performed separately or before the ignition timing and after the ignition timing.

When the engine speed starts to increase from the cranking speed, the engine is switched to the stratification mode in the stratification region at the time of warming, and the second set speed N2 or less when the timer is not "0" at the time of cold. At this time, the stratification mode is set while the purge is turned ON. In the stratified mode, the engine output can be adjusted by controlling the fuel injection amount even when the air is excessive, so that the number of revolutions from cranking may increase too rapidly or may overshoot. Is prevented,
The transition to the operating state after the start is completed is performed smoothly.
When the timer is "0" in the cold state after cranking, the purge is turned off and the mode is set to the uniform mode, so that the fuel vaporization and atomization are improved.

A specific example of the control at the time of starting is shown in FIG.
The present invention is not limited to the embodiment shown in FIG.

For example, the variable valve timing device 1
3, the closing timing of the intake valve 9 is closed early after the bottom dead center (BDC) as shown by the solid line in FIG. 7 and the early closing is closed earlier than the intake bottom dead center as shown by the broken line in the same drawing. In addition to the control shown in FIG. 4 at the time of starting the engine, the closing timing of the intake valve 9 is set to the above-mentioned early closing timing at least at the initial stage of starting when the purge gas is being introduced. May be controlled.

With this arrangement, when the engine is started, the closing timing of the intake valve is set to the above-mentioned early closing state, so that the effective compression ratio is reduced. As a result, the negative torque generated by the compression pressure in the compression stroke is reduced. This also suppresses torque fluctuations during cranking and the like. Note that the negative torque due to the compression pressure can be reduced even if the intake valve closing timing is made further later than the normal timing. However, if the intake valve closing timing is delayed in the purge introduction state, combustion occurs in the intake stroke. Since the purge gas supplied to the chamber is blown back, the amount of the purge gas in the combustion chamber tends to vary, and if the above-mentioned early closing is performed, the blow-back of the purge gas is avoided.

In the example shown in FIG. 7, the start of the valve opening at the early closing timing is set to the same timing as the start of the valve opening at the normal timing, and the full valve opening period is changed (shortened). The valve period may be the same, and the opening start of the early closing timing may be earlier than the opening timing of the normal timing. That is, when the engine is started, the engine speed is low and the pressure in the intake port 7 is close to the atmospheric pressure. Therefore, even if the opening and closing overlap between the exhaust valve 10 and the intake valve 9 is large, the intake port 7, the amount of internal EGR (the amount of exhaust gas remaining in the combustion chamber 5) is small, and the flammability does not deteriorate. Therefore, a rotational phase type variable valve timing device that shifts the phase between the crankshaft and the camshaft can be employed.

Further, as shown in FIG. 8, the control at the start of the engine may be changed between when the engine is operated due to rapid acceleration and when the engine is not operated. That is, in the example shown in this flowchart, following the processing of steps S1 to S3 (same as the processing of the same reference numeral in FIG. 4), it is determined whether or not the vehicle is in a rapid acceleration state by checking the rate of change of the accelerator opening. (Step S101) If the vehicle is in a rapid acceleration state, the timer set in step S2 is cleared (step S102).
The timer is not cleared unless the vehicle is in a rapid acceleration state. Then, the process of step S4 is performed. The process of step S4 is the same as that of FIG. 4, so that the description is omitted in FIG.

According to this embodiment, when the engine is operating due to rapid acceleration, the start-up combustion adjustment control (control for delaying the ignition timing and the fuel injection timing) for suppressing the torque to suppress the torque fluctuation during cranking is prohibited. Therefore, priority is given to securing the torque, and the acceleration demand of the driver is satisfied. When the engine is started other than during the rapid acceleration, the feeling is improved by suppressing the torque fluctuation as in the first embodiment.

FIG. 9 is a flowchart showing another embodiment of the start control. Steps for performing the same processes as those in the flowchart of FIG. 4 are denoted by the same reference numerals. In this embodiment, in addition to the control as shown in FIG. 4, a control for reducing the fuel pressure at the time of starting the purge at the time of starting is performed.

That is, if it is determined in step S4 following the processing in steps S1 to S3 that the engine speed ne is equal to or lower than the first set speed and the timer is determined not to be 0 in step S5, the purge is performed in step S6. Is turned on, and in step S201, the fuel circuit 2
The fuel pressure is adjusted to a predetermined low pressure by opening the zero bypass valve 31. In steps S7 to S9, the pulse width is calculated and the injection timing and the ignition timing are set. The pulse width is calculated based on the correspondence between the pulse width when the fuel pressure is a predetermined low pressure and the fuel injection amount. Is done.

When the timer is determined to be 0 in step S5, the purge is turned off in step S10, and in step S202, the fuel pressure is reduced to a predetermined high pressure by closing the bypass valve 31 of the fuel circuit 20. Adjusted. In this case, the pulse width is calculated based on the correspondence between the pulse width when the fuel pressure is a predetermined high pressure and the fuel injection amount, and is changed as compared with the case where the injection timing and the like are purge ON.

When the purge is turned on in step S17, the fuel pressure is adjusted to a predetermined low pressure accordingly (step S203), and when the purge is turned off in step S19, the fuel pressure is adjusted to a predetermined high pressure accordingly. (Step S204). Other processes are the same as those in the flowchart of FIG.

According to this embodiment, the control of the fuel injection amount and the like when the purge is turned ON at the initial stage of the engine start can be favorably performed. In other words, when the purge gas is introduced at the initial stage of engine start, it is necessary to adjust the fuel injection amount accordingly, so that if the fuel pressure is high, the pulse width becomes very small and control becomes difficult. However, if the fuel pressure is reduced, the pulse width becomes larger than in the case of the high pressure, so that the accuracy of the injection amount is improved. Also,
When an engine-driven fuel pump is used, the fuel pressure is unlikely to increase at the very beginning of the extremely low-speed rotation. From this viewpoint, it is more advantageous to adjust the fuel pressure to a low pressure for controllability.

However, when the fuel pressure is lowered, the ignitability tends to be deteriorated because the atomization of the injected fuel is deteriorated as compared with the case where the fuel pressure is high. However, since the purge gas is introduced, the ignitability is ensured, and Is performed favorably.

FIG. 10 is a flowchart showing still another embodiment of the start control. Steps for performing the same processes as those in the flowchart of FIG. 4 are denoted by the same reference numerals.

In this flowchart, if the suction amount of the canister is large according to the determination at step S1, the flag F is set to "1" at step S2 '.
When it is determined in step S4 following the processing in step S3 that the engine speed ne is equal to or less than the first set speed, it is determined in step S301 whether the flag F is "1", and the determination is YES ( If the amount of adsorption is large, it is determined in step S302 whether or not the water temperature Tw is higher than the predetermined temperature T1.

Then, if it is a warm time, it is determined whether or not the time is within a predetermined time corresponding to several cycles (step S30).
Purging is ON for a predetermined time based on 3) (Step S)
6), and it is set in steps S7 to S8 so that ignition and fuel injection are performed in the expansion stroke. After a lapse of a predetermined time, purge is turned off (step S1
0), and the fuel injection timing and the like are changed in steps S7 to S8. For example, the ignition timing is maintained after the compression top dead center (expansion stroke), but the fuel injection is started before the ignition timing. Or divided into a portion before the ignition timing and a portion after the ignition timing.

If it is determined in step S302 that the engine is in the cold state, the process proceeds to step S6, regardless of whether it is within a predetermined time, the purge is turned on, and ignition and fuel injection are performed in the expansion stroke. Is set to If the determination in step S301 is NO (small amount of adsorption), the process proceeds to step S10 and the purge is turned off.

In step S4, the engine speed ne becomes the first
If it is determined that the engine is warm during step S11 when it is determined that the rotational speed is equal to or higher than the set rotational speed N1, the second set rotational speed N2 is determined.
The purge is turned off during the rotation speed increase until the rotation speed reaches (Steps S304 and S305). If the rotation speed becomes higher than the second set rotation speed N2, the stratification mode or the uniform mode is selected according to the determination as to whether or not the stratified region is present ( S12 to S14).

If it is determined in step S11 that the engine is cold, it is determined in step S306 whether or not the flag F is "1". If the determination is YES (the amount of adsorption is large), the flow proceeds to step S16. If the determination in step S306 is N
If it is O (small amount of adsorption), the process moves to step S19. Other processes are the same as those in the flowchart of FIG.

According to this embodiment, the torque fluctuation in the initial stage of engine start is suppressed, and the torque adjustment from cranking to the completion of start is properly performed. Such a change can be appropriately suppressed.

That is, as shown in FIG. 11, when the engine is warm and the amount of adsorption of the canister 34 is large at the start of the engine, purge gas is introduced for a predetermined time from the start of cranking, ignition and fuel injection are performed. Performing in the expansion stroke suppresses torque fluctuation while performing good combustion. After a lapse of a predetermined time, the temperature of the combustion chamber rises, and ignition and combustion are likely to be promoted. In such a situation, if the introduction of the purge gas is continued, the flammability of the purge gas is increased, and the torque peak immediately after the ignition is increased. Is increased, which may cause torque fluctuation. Therefore, introduction of the purge gas is stopped, and ignition and combustion are performed by starting fuel injection before the ignition timing.

Further, during the period of increase in the number of revolutions after cranking and before the start is completed (from the first set number of revolutions N1 to the second set number of revolutions N2), the introduction of the purge gas enhances the combustibility to improve the engine. Such a rapid increase in the rotational speed of a hybrid vehicle in which the engine speed may be rapidly increased (see the broken line in FIG. 11) and the engine may be started regardless of the driver's intention during driving or the like. Gives an uncomfortable feeling to the driver, the introduction of the purge gas is stopped, and the fuel injection amount is controlled in the stratified combustion state, whereby the increase in the rotational speed is moderately moderated. Thus, as shown by the solid line in FIG. 11, the rotation speed changes smoothly from the cranking, and the engine smoothly transitions to the start-completion state.

On the other hand, when the engine is liable to deteriorate in flammability, the purge is controlled as much as possible during cranking or during the increase in the number of revolutions after cranking, so that the flammability can be maintained well. The cranking and the increase in the number of revolutions after the cranking are effectively performed.

Although the present invention is particularly effective when applied to an engine of a hybrid vehicle, even when it is applied to an engine other than a hybrid vehicle, it is possible to suppress the fluctuation of the torque while suppressing the torque fluctuation while satisfactorily performing the combustion at the start. The effect of reducing vibration is still obtained, which is effective for improving the feeling.

[0093]

As described above, the present invention relates to a vehicle engine equipped with an injector for directly injecting fuel into a combustion chamber and a purging device. In addition to the introduction, fuel is injected from the injector within the range from the late compression stroke to the expansion stroke, and the ignition timing is controlled so that it is after compression top dead center. In addition, by delaying the ignition timing and the combustion timing of the air-fuel mixture due to the fuel injection from the injector, torque fluctuations can be suppressed, and ignition and combustion can be favorably performed by the purge gas. Therefore, it is possible to suppress the torque fluctuation and reduce the vibration while maintaining the good flammability at the start.

In particular, in a hybrid vehicle in which the engine is operated intermittently while the vehicle is operating, the fuel vapor that easily accumulates in the canister while the engine is stopped can be quickly purged in the early stage of engine start, and the purge gas is effectively used. The engine is started regardless of the driver's intention while driving, etc. And the feeling can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an engine including a start control device according to the present invention.

FIG. 2 is a schematic diagram of a drive system of a hybrid vehicle shown as an example of application of the present invention.

FIG. 3 is a block diagram showing a mechanical configuration of an ECU.

FIG. 4 is a flowchart showing a first embodiment of start-time control;

FIG. 5 is an explanatory diagram showing an ignition timing and a fuel injection timing.

FIG. 6 is an explanatory diagram showing each stroke, fuel injection timing, and ignition timing of a four-cylinder four-cycle engine.

FIG. 7 is an explanatory diagram showing opening / closing timings of an intake valve during normal time and at startup.

FIG. 8 is a flowchart illustrating a second embodiment of the start-time control, with a part thereof being omitted;

FIG. 9 is a flowchart showing a third embodiment of the start-time control.

FIG. 10 is a flowchart illustrating a start-time control according to a fourth embodiment;

11 is an explanatory diagram of the control shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 5 Combustion chamber 13 Variable valve timing device 15 Spark plug 18 Injector 33 Purge device 34 Canister 38 Purge valve 60 Control unit 62 Accelerator opening sensor 64 Water temperature sensor 70 Start discrimination means 71 Adsorption amount judgment means 72 Purge control means 73 Purge control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/04 335 F02D 41/04 335B 41/34 41/34 F F02M 25/08 301 F02M 25/08 301L 301U 301H F02P 5 / 15 F02P 5/15 E

Claims (11)

[Claims] 1. A start determining means for determining an engine start time in an automobile engine having an injector for directly injecting fuel into a combustion chamber and having a purge device for guiding evaporated fuel from a canister to an intake passage via a purge valve. When it is determined that the amount of adsorbed evaporative fuel is large at the initial stage of engine start, according to the adsorbed amount determining means for determining the amount of evaporated fuel adsorbed by the canister; Purge control means for opening the purge valve to introduce a purge gas, and when the purge gas is introduced by the purge control means at the initial stage of engine start, fuel is supplied from the injector within a range from a late compression stroke to an expansion stroke. Initial combustion adjustment control for injection with injection and ignition timing after compression top dead center And a combustion control means for performing the following. 2. A purge gas introduction control by said purge control means and a starting initial combustion adjustment control by said combustion control means during a period in which the engine is in a cranking state at an early stage of engine start, and a start-up after cranking until a start is completed. 2. The control device for an automobile engine according to claim 1, wherein the fuel injection timing is changed before the latter half of the compression stroke and the ignition timing is changed before the compression top dead center during the rotation speed increase. 3. The control system for an automobile engine according to claim 1, wherein said purge control means performs a purge gas introduction control at an early stage of engine start when the engine is warm. 4. A control device for an automobile engine used in a hybrid vehicle including an engine and a motor, wherein the engine is operated intermittently during operation of the vehicle, wherein the purge is performed when the engine is started except when the engine is operated due to rapid acceleration. The control apparatus for an automobile engine according to any one of claims 1 to 3, wherein a purge gas introduction control by the control means and an initial combustion adjustment control by the combustion control means are performed. 5. A stratifying means for unevenly distributing an air-fuel mixture around a spark plug when fuel is injected from an injector in a compression stroke, and in a specific operation, fuel is injected in a compression stroke to perform stratified combustion. At the same time, ignition and fuel injection are performed during the expansion stroke as initial combustion adjustment control by the combustion control means at the initial stage of engine start, and the purge gas is introduced by the purge control means for at least a predetermined period corresponding to several cycles from the start of cranking. The control device for an automobile engine according to any one of claims 1 to 4, wherein the control is performed. 6. An electric drive motor and an engine,
In a hybrid vehicle in which the engine is started to assist the output when an increase in output is requested during driving of the vehicle by the motor drive, an injector that directly injects fuel into the combustion chamber and fuel is injected from the injector in a compression stroke A control device for controlling an engine including a stratification means for unevenly distributing an air-fuel mixture around a spark plug, and a purge device for guiding evaporative fuel from a canister to a suction passage via a purge valve. Discriminating means, combustion control means for performing ignition and fuel injection in an expansion stroke as initial combustion adjustment control for engine start according to the discrimination of the start discriminating means, and a predetermined period corresponding to at least several cycles from the start of cranking. Purge control means for opening a purge valve to make a purge gas introduction state. Controller of that engine. 7. When the engine is warm, the introduction of the purge gas is temporarily stopped after a predetermined period corresponding to several cycles from the start of cranking, and the fuel injection is started before the ignition timing. 7. The control device for an automobile engine according to claim 5, wherein the fuel injection timing is changed, and the purge gas introduction stop state is maintained until the start of the engine is completed thereafter. 8. A system according to claim 1, further comprising a valve timing variable means for changing a closing timing of the intake valve, wherein a purge gas introduction control by the purge control means and an initial combustion adjustment control by the combustion control means are performed at an initial stage of the engine start. 8. The control device for an automobile engine according to claim 1, wherein the closing timing of the intake valve is set earlier than the intake bottom dead center. 9. A fuel pressure adjusting device capable of changing a fuel pressure of fuel supplied from a fuel pump and injected from an injector between a predetermined high pressure and a predetermined low pressure lower than the predetermined high pressure, and adjusting the fuel pressure to maintain the predetermined high pressure during a normal operation. And fuel pressure changing means for changing the fuel pressure to the predetermined low pressure when the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means are performed in the initial stage of engine start. The control device for an automobile engine according to any one of claims 1 to 8, wherein: 10. An injector for directly injecting fuel into a combustion chamber, and a fuel pressure of fuel supplied from a fuel pump and injected from the injector can be changed between a predetermined high pressure and a predetermined low pressure lower than this. In a vehicle engine including a fuel pressure adjusting means for adjusting the pressure to be maintained at the predetermined high pressure, and a purge device for guiding the fuel vapor from the canister to the intake passage via a purge valve, a start determining means for determining an engine start time; An adsorption amount determining means for determining the amount of fuel vapor adsorbed by the canister, and the purge valve when the evaporative fuel adsorption amount is determined to be large in the initial stage of engine start according to the determination by the start determining means and the determination by the adsorption amount determining means. Purge control means for opening the purge gas to introduce a purge gas, and An engine control device comprising: fuel pressure changing means for changing the fuel pressure of the fuel injected from the injector to the predetermined low pressure when the gas is introduced. 11. The control apparatus for an automobile engine according to claim 10, wherein said purge control means performs purge gas introduction control at an early stage of engine start when the engine is warm.