JP3769928B2 - Automotive engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device that controls purge, fuel injection, and the like so that a smooth engine start is performed in an automobile engine that includes an injector that directly injects fuel into a combustion chamber and that includes a purge device.
[0003]
[Prior art]
Conventionally, in a spark ignition engine (gasoline engine) that is ignited by a spark plug, an injector with a tip facing the combustion chamber is provided so that fuel is directly injected into the combustion chamber, and a specific operation such as low rotation and low load is provided. 2. Description of the Related Art An in-cylinder injection engine is known in which in the region, fuel is injected from a injector in a compression stroke to cause flammable mixture to be unevenly distributed in the vicinity of a spark plug to perform stratified combustion to improve fuel efficiency.
[0004]
Further, an engine having a purge device that adsorbs evaporated fuel generated in a fuel tank or the like to a canister and guides the evaporated fuel from the canister to an intake passage through a purge valve is known. In an engine equipped with this purge device, purge gas is introduced into the intake passage during a specific operation of the engine and is supplied to the combustion chamber for combustion. However, in an engine where there is little opportunity for a purgeable operation state, a canister In some cases, this cannot be sufficiently purged with respect to an increase in the amount of adsorption.
[0005]
For example, in a hybrid vehicle that includes an engine and a motor and the engine is intermittently operated while the vehicle is operating, the engine is often in a resting state even while the vehicle is running, and the canister is adsorbed during the engine resting period. As the amount increases, it may happen that it cannot be purged.
[0006]
As a countermeasure for such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-233410, in an electric vehicle in which a vehicle is driven by a motor and a power supply generator is driven by an engine, The amount of evaporated fuel is detected based on the detection of the weight of the canister, and the engine is driven when the amount of evaporated fuel increases, and the engine is stopped when the amount of evaporated fuel decreases after the engine is driven. is there. Further, as disclosed in Japanese Patent Application Laid-Open No. 8-308019, in an electric vehicle in which the vehicle is driven by a motor and the generator for power supply is driven by an engine, when the amount of charge of the battery is reduced, etc. In addition to driving the engine for charging, there is one that drives the engine with a smaller load than the driving for charging when the amount of adsorption of the canister increases.
[0007]
In addition, although all the engines 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 driving driving assistance, for example, It is also known that the engine starts and assists the output when an increase in output is required while the vehicle is driven by a motor. Even in this type of hybrid vehicle, the engine operates intermittently. Therefore, the amount of adsorption of the canister is likely to increase when the engine is stopped, and countermeasures are required.
[0008]
[Problems to be solved by the invention]
In the prior art as shown in each of the above publications, when the amount of adsorption of the canister increases, the engine is simply operated for purging, but the evaporated fuel has good vaporization and excellent ignitability. Because of the characteristics, it is desirable to increase the purge opportunities as much as possible and to effectively use the purge gas in order to improve the operation performance.
[0009]
By the way, in general, in a four-cycle engine, after supply of an air-fuel mixture to a combustion chamber (for example, fuel injection from an injector) is performed, ignition is performed immediately before the top dead center of the compression stroke. Immediately after that, a large torque is generated due to the pressure increase due to combustion, but in the latter half of the compression stroke before that, a negative torque is generated as the compression pressure increases, and the negative torque and the positive torque are shifted in time. Acting causes torque fluctuations. In particular, at the time of cranking at the initial stage of starting when the engine speed is very 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 start of the engine is not preferable in terms of feeling and the like. In particular, in a hybrid vehicle in which the engine and motor are used properly and the engine is intermittently operated during vehicle operation, the engine may be started regardless of the driver's will during driving. Engine vibration makes the driver feel uncomfortable and makes the feeling worse.
[0011]
In order to suppress the torque fluctuation at the initial stage of engine start, a method of lowering the peak of positive torque by delaying the combustion timing can be considered. However, the ignitability is deteriorated simply by adjusting the combustion timing so as to be shifted, and it becomes difficult to perform combustion well.
[0012]
In view of such circumstances, the present invention satisfies the requirement of increasing the purge opportunity to eliminate the increase in the amount of adsorption of the canister and the requirement of reducing engine vibration at the initial stage of engine start. In particular, the purge gas is effectively used. An object of the present invention is to provide a start control device for an automobile engine that can reduce engine vibration by suppressing torque fluctuation while favorably performing ignition and combustion at the time of engine start.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an automobile engine provided with an injector that injects fuel directly into a combustion chamber and a purge device that guides evaporated fuel from a canister to an intake passage through a purge valve. A start determining means for determining when the engine is started, an adsorption amount determining means for determining the evaporated fuel adsorption amount of the canister, and an evaporative fuel at an initial stage of engine startup according to the determination of the start determining means and the determination of the adsorption amount determining means. A purge control means that opens the purge valve when it is determined that the amount of adsorption is large, and enters the purge gas introduction state; and when the purge gas introduction state is established by the purge control means at the initial stage of engine start, The ignition timing is after compression top dead center, and the fuel injection timing is during the expansion stroke after the ignition timing. Combustion control means for performing initial start combustion adjustment control In addition, the purge gas introduction control by the purge control means and the initial combustion adjustment control by the combustion control means are performed within the cranking state at the initial stage of engine start, and the number of revolutions from the cranking to the completion of the start is increasing. Changes the ignition timing before the compression top dead center, and the fuel injection timing is before the ignition timing, and the fuel is injected in the stratification mode in which the fuel is injected in the compression stroke and the stratified combustion is performed. It was configured to change to the injection timing corresponding to one of the combustion modes of the uniform mode that injects and performs uniform combustion Is.
[0014]
According to this apparatus, the ignition timing and the combustion timing of the air-fuel mixture due to fuel injection from the injector are delayed compared to the normal setting at the beginning of the engine start, where torque fluctuation is likely to occur. Be done Thus, torque fluctuations are suppressed by lowering the peak of torque due to combustion. In addition, ignition and combustion can be performed satisfactorily by introducing a purge gas having a good vaporization state.
[0015]
In particular, Torque fluctuations are suppressed during cranking, and torque is increased as compared with the initial stage of startup when the rotational speed is increasing from cranking to completion of startup.
[0016]
The purge gas introduction control at the initial stage of engine start by the purge control means and the initial combustion adjustment control at the start of combustion by the combustion control means are performed when the engine is warm. 2 In this case, purge gas introduction control is effectively performed in a state in which purge gas introduction is reliable and combustion stability is high.
[0017]
In addition, when the apparatus of the present invention is applied to a hybrid vehicle that includes an engine and a motor, and the engine is intermittently operated while the vehicle is operating, it effectively uses the evaporated fuel that tends to accumulate in the canister when the engine is stopped, etc. In addition, it is possible to reduce the uncomfortable feeling given to the driver even when the engine is started regardless of the driver's will during driving. In this case, the purge gas introduction control by the purge control means and the start initial combustion adjustment control by the combustion control means are performed at the time of engine start excluding engine operation due to sudden acceleration (claims). 3 ), Priority is given to securing torque for rapid acceleration when the engine is operating during sudden acceleration, and control for suppressing torque fluctuation is effectively performed during other engine startups.
[0018]
In addition, the fuel cell is provided with stratification means for causing the air-fuel mixture to be unevenly distributed around the spark plug when fuel is injected from the injector during the compression stroke, so that fuel is injected during the compression stroke during specific operation so that stratified combustion is performed. As the initial combustion adjustment control by the combustion control means at the beginning of the start, ignition and fuel injection are performed in the expansion stroke, and purge gas introduction control is performed by the purge control means for at least a predetermined period corresponding to several cycles from the start of cranking. (Claims) 4 ) Is preferred.
[0019]
In this way, during the predetermined period from the start of cranking, the ignition and fuel injection are set in the expansion stroke, so that the torque peak due to combustion becomes low, and the torque fluctuation is suppressed. In addition, ignition is performed well during stratified combustion by compression stroke injection, whereas when the engine is started, the ignition timing and fuel injection timing are shifted to the expansion stroke, so that the stratification degree tends to decrease and the ignitability tends to deteriorate. Although it occurs, it is compensated by supplying purge gas with good ignitability.
[0020]
Claim 5 The present invention relates to a hybrid vehicle that includes an electrically driven motor and an engine, and injects fuel directly into a combustion chamber in a hybrid vehicle that starts up and assists the output when an increase in output is required while the vehicle is driven by the motor. Engine having a stratifying 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 device for guiding evaporated fuel from the canister to an intake passage through a purge valve A start determination means for determining when the engine is started, a combustion control means for performing ignition and fuel injection in an expansion stroke as engine start initial combustion adjustment control according to the determination of the start determination means, Open the purge valve for at least a predetermined period corresponding to several cycles from the start of cranking to purge gas And a purge control unit for the input and state When the engine is warm, the introduction of purge gas is stopped and the ignition timing is changed before the compression top dead center until the start of the engine is completed after the elapse of a predetermined period corresponding to several cycles from the start of cranking. And the fuel injection timing is changed to a compression stroke before the ignition timing. Is.
[0021]
According to the present invention, in the hybrid vehicle described above, the engine includes the injector and the stratification means for directly injecting fuel into the combustion chamber, so that stratified combustion is possible depending on the operation state, and ignition and fuel injection are expanded when the engine is started. By setting the stroke, the torque fluctuation is suppressed, the engine vibration is reduced, and the tendency that the stratification degree is lowered and the ignitability is deteriorated is compensated by supplying purge gas with good ignitability.
[0023]
Also, When the engine is warm, the combustion chamber temperature rises after a specified period of time from the start of cranking, and the combustibility is improved. Further, it is possible to prevent a situation in which the combustibility is excessively increased by the supply of the purge gas and the torque is rapidly increased.
[0024]
In addition, there is provided a valve timing variable means for changing the valve 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 engine start, The valve closing timing is set earlier than the intake bottom dead center. 6 ) Is preferred.
[0025]
In this way, the effective compression ratio is reduced, so that the negative torque generated by the compression pressure in the compression stroke is reduced, and this also suppresses torque fluctuations in cranking and the like.
[0026]
In addition, the fuel pressure of the fuel supplied by the fuel pump and injected from the injector can be changed between a predetermined high pressure and a predetermined low pressure lower than this, and fuel pressure adjusting means for adjusting the fuel pressure to keep the predetermined high pressure during normal operation is provided. And a 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. 7 ) Is preferred.
[0027]
In this way, when the purge gas is introduced at the beginning of the engine start, the fuel injection amount is reduced by the amount corresponding to the purge gas, so that the pulse width (injection time) becomes very small in high-pressure injection, making it difficult to control the fuel injection amount. On the other hand, the low-pressure injection is advantageous for controlling the fuel injection amount because the pulse width is larger than that of the high-pressure injection. On the other hand, when the low-pressure injection is used, the atomization of the fuel is worse than that of the high-pressure injection. This is disadvantageous for the ignitability, but the ignitability is ensured by the purge gas.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0032]
FIG. 1 schematically shows the overall structure of an in-cylinder injection engine to which the present invention is applied. In this figure, the engine body 1 has a plurality of cylinders, for example, four cylinders 2a to 2d (see FIG. 2), and each cylinder has a combustion chamber above a piston 4 inserted in a cylinder bore. 5 is formed. An intake port 7 and an exhaust port 8 are opened in the combustion chamber 5, and these ports 7 and 8 are opened and closed by an intake valve 9 and an exhaust valve 10, respectively.
[0033]
The intake valve 9 and the exhaust valve 10 are opened and closed by a valve operating mechanism including camshafts 11 and 12. The valve operating 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.
[0034]
A spark plug 15 is disposed at the center of the combustion chamber 5, and the tip of the plug faces the combustion chamber 5. The spark plug 15 is connected to the ignition coil 16.
[0035]
In addition, the tip of the injector 18 faces the combustion chamber 5 from the side, and fuel is directly injected into the combustion chamber 5 from the injector 18. The injector 18 of each cylinder is connected to a 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 an in-tank fuel pump 25, filters 26 and 27, and a high-pressure fuel pump are provided 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 disposed between the return passage 23 and the fuel tank 24, and a passage (not shown) that bypasses the high-pressure side pressure regulator 29. And a bypass valve 31 for opening and closing the passage.
[0036]
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, and the fuel pressure can be changed by the operation of the bypass valve 31. 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 action of the high-pressure pressure regulator 29, and the bypass valve 31 is opened. In some cases, 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 regulating action of the low pressure side pressure regulator 30.
[0037]
A purge device 33 is provided between the fuel tank 24 and the intake passage 40 of the engine. The purge device 33 is connected between the canister 34 that adsorbs the evaporated fuel, the passage 35 that guides the evaporated fuel in the fuel tank 24 to the canister 34 via the check valve 36, and the canister 34 and the intake passage 40. A purge passage 37 and a purge valve 38 interposed in the purge passage are arranged so that purge gas (evaporated fuel) is introduced from the canister 34 into the intake passage 40 when the purge valve 38 is opened.
[0038]
Further, the intake passage 40 and the exhaust passage 41 are connected to the engine body 1. In the intake passage 40, an air cleaner 43, an air flow sensor 44, a throttle valve 45 driven by a motor 46, and a surge tank 47 are provided in this order from the upstream side. A throttle opening sensor 48 that detects the opening of the throttle valve 45 is provided. Further, an ISC passage 50 that bypasses the throttle valve 45 is provided, and an ISC valve 51 that controls the air flow rate of the passage is provided in the ISC passage 50.
[0039]
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. Each independent intake passage 53 is provided with a swirl control valve 54. The swirl control valve 54 is driven by an actuator 55 such as a step motor to open and close, and the intake swirl is controlled by the opening and closing operation. ing. The swirl control valve 54 serves as stratified combustion means for causing the air-fuel mixture to be unevenly distributed around the spark plug when fuel is injected from the injector 18 in the compression stroke.
[0040]
On the other hand, the exhaust passage 41 detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas. ₂ A sensor 57 is provided, and an exhaust gas purifying catalyst 58 is provided downstream thereof.
[0041]
Reference numeral 60 denotes an engine control unit (ECU). The ECU 60 includes the air flow sensor 44, the throttle opening sensor 48, and the O ₂ The detection signals a, b, and c from the sensor 57 are input, and the crank angle signal d and the cylinder discrimination signal e for detecting the engine speed and the like are input from the distributor 61 interlocked with the camshaft 12. Detection signals f, g, h from an accelerator opening sensor 62 that detects the opening (accelerator pedal depression amount), an intake air temperature sensor 63 that detects the temperature of intake air, a water temperature sensor 64 that detects the temperature of engine coolant, and the like. Is also entered.
[0042]
Further, the ECU 60 outputs a signal j for controlling fuel injection to the injector 18 via the injector drive unit 66, and also outputs a signal k for controlling the ignition timing to the ignition coil 16, and also drives the throttle valve. A signal l for controlling the throttle opening is output to the motor 46 through the throttle 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, and a valve timing variable device A signal o for controlling 13 and a signal p for controlling the purge valve 38 are also output.
[0043]
The apparatus of the present invention is effective when applied to a hybrid vehicle using both an engine and a motor. An example of the hybrid system is shown in FIG.
[0044]
In this figure, a continuously variable transmission is connected to the output shaft of the engine body 1. 8 0 input side torque converter 8 1 is connected, while continuously variable transmission 8 The final reduction gear on the output side of 0 8 2 through axle 8 3 is connected and a motor / generator 8 4 is connected. Further, a belt is provided on the output shaft front end side of the engine body 1. 8 Alternator via 5 etc. 8 6 is connected. Above motor / generator 8 4 and alternator 8 6 is an inverter 8 7, 8 Battery through 8 8 9 is connected.
[0045]
Then, a hybrid system control controller (ECU 60 in FIG. 1 or a controller not shown) separates the engine and the motor / generator for driving the vehicle according to the driving state of the vehicle. 8 The engine is driven intermittently while the vehicle is operating. For example, while the vehicle is driven by a motor, the engine is stopped during low-speed driving or the like, and when the output increase is requested, the engine is started to assist the output.
[0046]
FIG. 3 shows a functional configuration of the ECU 60. As shown in this figure, the ECU 60 functionally includes a start determination means 70, an adsorption amount determination means 71, a purge control means 72, and a combustion control means 73.
[0047]
The start discriminating means 70 discriminates when the engine is started based on information from a hybrid system control controller or the like. Further, the adsorption amount determination means 71 determines the evaporated fuel adsorption amount of the canister 34. Various methods for determining the evaporated fuel adsorption amount have been proposed in the past, and are not limited by the present invention. ₂ When purging is performed in a state where the air-fuel ratio feedback control based on the output of the sensor 57 is being performed, the purge gas introduction amount is obtained based on the change in the air-fuel ratio feedback correction coefficient, and is added to the control as a learning value. Therefore, the evaporated fuel adsorption amount is estimated based on the learned value. However, the determination to be performed when the engine is started from the stopped state is that the evaporated fuel adsorption amount is estimated based on the learned value obtained and stored in the feedback control during the previous engine operation (when the engine is operating before the stop). Good. The adsorption amount of the canister may be detected by a sensor.
[0048]
The purge control means 72 opens the purge valve 38 and introduces purge gas when it is determined that the amount of adsorbed fuel vapor is large at the initial stage of engine start according to the determination of the start determination means 70 and the determination of the adsorption amount determination means 71. Control to be in a state. Further, the combustion control means 73 injects fuel from the injector within the range from the latter stage of the compression stroke to the expansion stroke when the purge gas is introduced by the purge control means 72 at the initial stage of engine start, and the ignition timing. Is controlled to be after compression top dead center.
[0049]
In addition to this, 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 startup, the bypass valve 31 of the fuel circuit 20 is controlled. Fuel pressure changing means 74 for changing the fuel pressure to the predetermined low pressure may be provided. 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 being performed at the initial stage of engine start, the closing timing of the intake valve 9 is set to an earlier timing than the intake bottom dead center. As described above, a control means 75 for controlling the valve timing variable device (VVT) 13 may be provided.
[0050]
FIG. 4 is a flowchart showing an example of start control performed in the ECU 60. The process shown in this flowchart starts when engine start is started when a predetermined engine operating condition is satisfied, for example, during driving of the hybrid vehicle. Note that hybrid system control, including determination of engine operating conditions and control of engine operation and stop in accordance with it, and determination of motor operating conditions and control of motor operation and stop in accordance with that, are not shown. This is done by a control routine.
[0051]
When the engine is started, first, in step S1, for example, as described above, whether or not the adsorption amount of the canister 34 is larger than a predetermined value based on the purge learning value in the air-fuel ratio feedback control during the previous engine operation. Is determined. If the adsorption amount is large, in order to perform a purge for a predetermined period from the start of cranking, the predetermined time TM1 is set in the timer in step S2, and then the process proceeds to step S3. The value of this timer decreases with time. When the adsorption amount is small, the process proceeds to step S3 as it is.
[0052]
In step S3, the engine speed ne obtained from the crank angle signal, the accelerator opening accel detected by the accelerator opening sensor 62, and the water temperature Tw detected by the water temperature sensor 64 are read. Subsequently, in step S4, it is determined whether or not the engine speed ne is higher than the first set speed N1. The first set rotational speed N1 is set to a rotational speed slightly higher than the cranking rotational speed (for example, 300 rpm). Therefore, when the determination in step S4 is NO, the cranking state is established. When this determination is YES Means that the engine speed is higher than the cranking state.
[0053]
When the determination in step S4 is NO (cranking state), it is determined in step S5 whether or not the timer has become zero. When the timer is not 0, that is, within a predetermined time from the start of cranking, purge ON (purge valve 3) is controlled as the control of the purge control means 72 in step S6. 8 Is open). Further, calculation of the pulse width for determining the fuel injection amount (step S7), setting of the injection timing (step S8), and setting of the ignition timing (step S9) are performed. In this case, the injection timing and the ignition timing are set as indicated by 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 in the expansion stroke after the ignition timing IgA.
[0054]
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, purge OFF (purge valve 3) is determined in step S10. 8 Is closed) and the process proceeds to step S12 to be described later. Since the low rotation and low load region is the stratification region, the process proceeds to step S13 to be described later and the stratification mode is set.
[0055]
When it is determined in step S4 that the engine speed ne is higher than the first set speed N1, the water temperature T is determined in step S11. _W It is determined whether or not the temperature is higher than the set temperature T1. If it is warm, based on the determination of whether or not it is a stratified region (step S12), if it is a stratified region, it is set to a stratified mode (step S13), and if it is not a stratified region, it is set to a uniform mode (step S14). ).
[0056]
Here, the stratification region means an operation region suitable for performing stratified combustion. For example, a predetermined operation region on the low rotation and low load side is set as a stratification region in advance. The stratified mode is a mode for controlling the fuel injection timing and the ignition timing so that ignition is performed in a state in which fuel is injected from the injector in the compression stroke and the air-fuel mixture is unevenly distributed in the vicinity of the spark plug. Is a mode in which the fuel injection timing and ignition timing are controlled so that ignition is performed in a state where fuel is injected from the injector during the intake stroke and fuel is uniformly diffused throughout the combustion chamber. In the stratified mode and the uniform mode, the ignition timing is set before the top dead center, as in this type of general engine.
[0057]
In step S11, the water temperature T _W Is determined to be cold at or below the set temperature T1, whether or not the timer is “0” is determined in step S15. If the timer is not “0”, the engine speed ne is further determined in step S16. Is higher than the second set rotational speed N2. The second set rotational speed N2 is a rotational speed close to the idle rotational speed (for example, about 600 rpm).
[0058]
When it is determined in step S16 that the rotation speed is equal to or lower than the second set speed N2, the purge is turned on in step S17, and the process proceeds to step S13 to enter the stratification mode, which is determined to be higher than the second set speed N2. If so, the uniform mode is set in step S18.
[0059]
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.
[0060]
After the setting of the pulse width, the injection timing and the ignition timing in steps S7 to S9, or the mode setting in any of steps S13, S14 and S18, fuel injection and ignition are executed according to the settings in step S20.
[0061]
The operation of the apparatus of the present embodiment as described above will be described next.
[0062]
At the start of the engine, if the amount of adsorption of the canister 34 is large, the purge valve 38 is opened and the purge is introduced at the initial stage of cranking when the engine speed is lower than the first set speed N1, As indicated by the solid line in FIG. 5, ignition (IgA) is performed after compression top dead center, and fuel is injected (injA) from the injector into the combustion chamber during the subsequent expansion stroke.
[0063]
In such a control state, the purge gas in the combustion chamber is ignited and burned at the ignition timing after compression top dead center, which becomes a fire type, and the air-fuel mixture by the subsequent fuel injection is burned. In this case, the ignition timing is later than the ignition timing during normal operation (before compression top dead center), and fuel injection is performed during the subsequent expansion stroke, and combustion of the main mixture by this fuel injection is performed in normal operation. The torque peak is lowered by being greatly delayed compared to the time. For this reason, torque fluctuation in the initial stage of starting is reduced.
[0064]
Furthermore, in a multi-cylinder (generally four or more cylinders) four-cycle engine in which the later stage of the expansion stroke of some cylinders and the compression stroke of other cylinders lap, combustion is performed during the expansion stroke as described above. Thus, the action of canceling out the negative torque generated in the cylinder in the compression stroke can be obtained.
[0065]
Specifically, for example, in the case of a four-cylinder four-cycle engine, as shown in FIG. 6, the crank angle is shifted by 180 ° in order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. By sequentially performing the intake, compression, expansion, and exhaust strokes, the positive torque caused by the combustion in the expansion stroke of the first cylinder cancels the negative torque in the compression stroke of the third cylinder that wraps therewith. 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 lap, respectively. Even during this time, the torque applied in the cylinder in the expansion stroke cancels the negative torque in the cylinder in the compression stroke.
[0066]
By these actions, torque fluctuation at the start of the engine and accompanying engine vibration are reduced, and the feeling is improved. In particular, in a hybrid vehicle such as that shown in FIG. 2, the engine is started regardless of the driver's will, for example, during the transition from the motor operating state to the engine operating state even during traveling. In particular, it is possible to prevent the driver from feeling uncomfortable due to torque fluctuation.
[0067]
By adjusting the combustion in this way, torque fluctuation is suppressed. On the other hand, if ignition and combustion are delayed, the ignitability tends to deteriorate, but the purge gas already exists in the combustion chamber at the ignition timing. Since the purge gas is vaporized well and has good ignitability, ignition and combustion are performed well while the combustion of the main mixture is delayed. In this way, the purge gas is effectively used to improve the combustibility at the time of starting, and the adsorption amount of the canister 34 is reduced by this purge.
[0068]
Since it is predicted that the amount of adsorption of the canister 34 will decrease when the purge is performed for a predetermined time, the purge is turned OFF. When the purge is turned off during cranking, the mode is changed to the stratified combustion mode, and fuel is injected (injB) in the compression stroke as shown by the broken line in FIG. 5 and is ignited before the compression top dead center. (IgB) is performed. In addition, at the time of purge OFF during cranking, instead of being in the stratified mode as described above, the ignition timing is set at the start of fuel injection with 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 before the ignition timing and after the ignition timing.
[0069]
Further, when the engine speed starts to rise from the cranking speed, the stratification mode is set in the stratification region during the warm time, and when the timer is not "0" during the cold time, the purge is performed when the second set speed N2 or less. While being ON, the stratified mode is set. When the stratified mode is set in this way, the engine output can be adjusted by controlling the fuel injection amount even when the air is excessive, so the increase in the rotational speed from cranking may become too rapid or overshoot. Thus, 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 uniform mode is set to improve fuel vaporization and atomization.
[0070]
In addition, the specific example of the control at the time of starting is not limited to embodiment shown in said FIG. 4, A various change is possible.
[0071]
For example, the intake valve bottom dead center as shown by the broken line in FIG. 7 is the normal timing when the valve timing varying device 13 closes the closing timing of the intake valve 9 after the bottom dead center (BDC) as shown by the solid line in FIG. In addition to the control shown in FIG. 4 described above when starting the engine, the closing timing of the intake valve 9 can be changed at least at the beginning of the start when the purge gas is introduced. You may control so that it may become the said early closing timing.
[0072]
In this way, when the engine is started, the closing timing of the intake valve is quickly closed to reduce the effective compression ratio, thereby reducing the negative torque generated by the compression pressure in the compression stroke. Torque fluctuation in cranking or the like is suppressed. Note that the negative torque due to the compression pressure can be reduced even if the intake valve closing timing is further delayed than the normal timing, but 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 purge gas in the combustion chamber is likely to vary. On the other hand, when the valve is closed early, the purge gas is prevented from being blown back.
[0073]
In the example shown in FIG. 7, the valve opening start at the early closing timing is set to the same timing as the valve opening start at the normal timing, and the full valve opening period is changed (shortened). The valve opening start at the early closing timing may be made earlier than the valve opening start at the normal timing. That is, when the engine is started, the engine speed is low and the pressure of the intake port 7 is close to the atmospheric pressure. Therefore, even if the opening / closing overlap between the exhaust valve 10 and the intake valve 9 is large, the intake port of the exhaust gas 7 is small and the air ratio in the exhaust gas is large, the internal EGR amount (exhaust gas amount remaining in the combustion chamber 5) is small, and the combustibility is not deteriorated. Therefore, a rotational phase type valve timing variable device that shifts the phase between the crankshaft and the camshaft can also be employed.
[0074]
Further, as shown in FIG. 8, the control at the time of start may be changed between when the engine is operating due to rapid acceleration and when it is not. In other words, in the example shown in this flowchart, it is determined whether or not the vehicle is in the rapid acceleration state by examining the accelerator opening change rate following the processing of steps S1 to S3 (same as the processing of the same reference numerals in FIG. 4). (Step S101) If the acceleration state is sudden, the timer set in Step S2 is cleared (Step S102). If the acceleration state is not sudden, the timer is not cleared. Then, the process of step S4 is performed. Since the process of step S4 is the same as that in FIG. 4, the description is omitted in FIG.
[0075]
According to this embodiment, when the engine is operated by rapid acceleration, start-up combustion adjustment control (control for delaying the ignition timing and fuel injection timing) that suppresses torque to suppress torque fluctuation during cranking is prohibited, and torque is secured. Is prioritized to satisfy the driver's acceleration requirements. When the engine is started other than during rapid acceleration, the feeling is improved by suppressing torque fluctuations as in the first embodiment.
[0076]
FIG. 9 is a flowchart showing another embodiment of the start control, and 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, control is performed to reduce the fuel pressure when the purge is introduced at the start.
[0077]
That is, when it is determined in step S4 following the processing of steps S1 to S3 that the engine speed ne is equal to or less than the first set speed and in step S5 it is determined that the timer is not 0, the purge is turned on in step S6. In step S201, the fuel pressure is adjusted to a predetermined low pressure by opening the bypass valve 31 of the fuel circuit 20. In step S7 to step S9, the pulse width is calculated and the injection timing and ignition timing are set. The pulse width is calculated based on the correspondence between the pulse width and the fuel injection amount when the fuel pressure is a predetermined low pressure. Is done.
[0078]
If the timer is determined to be 0 in step S5, the purge is turned off in step S10, and the fuel pressure is adjusted to a predetermined high pressure by closing the bypass valve 31 of the fuel circuit 20 in step S202. . 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 with respect to the case where the injection timing or the like is purged ON.
[0079]
When the purge is turned on in step S17, the fuel pressure is adjusted to a predetermined low pressure (step S203). When the purge is turned off in step S19, the fuel pressure is adjusted to a predetermined high pressure (step S203). S204). Other processes are the same as those in the flowchart of FIG.
[0080]
According to this embodiment, the control of the fuel injection amount when the purge is turned on at the initial stage of engine startup is performed satisfactorily. In other words, when purge gas is introduced at the beginning of engine start-up, it is necessary to adjust the fuel injection amount accordingly, so if the fuel pressure is high, the pulse width becomes very small and control is difficult. However, if the fuel pressure is set to a low pressure, the pulse width becomes larger than that in the case of a high pressure, so that the accuracy of the injection amount is improved. Further, when an engine-driven fuel pump is used, the fuel pressure is unlikely to increase at the initial stage of extremely low rotation, and it is advantageous for controllability to adjust to a low pressure from this aspect.
[0081]
However, if the fuel pressure is lowered, atomization of the injected fuel will be worse than in the case of high pressure, so that the ignitability tends to deteriorate.However, since the purge gas is introduced, this ensures the ignitability and improves the combustion. Will be done.
[0082]
FIG. 10 is a flowchart showing still another embodiment of the start control, and steps for performing the same processes as those in the flowchart of FIG. 4 are given the same reference numerals.
[0083]
In this flowchart, in accordance with the determination in step S1, when the adsorption amount of the canister is large, the flag F is set to “1” in step S2 ′. If it is determined in step S4 following step S3 that the engine speed ne is equal to or lower than the first set speed, it is determined in step S301 whether or not the flag F is “1”, and the determination is YES ( If the adsorption amount is large), it is determined in step S302 whether the water temperature Tw is warmer than the predetermined temperature T1.
[0084]
If it is warm, the purge is turned ON (step S6) for a predetermined time based on the determination (step S303) as to whether or not it is within a predetermined time corresponding to several cycles, and in steps S7 to S8. It is set so that ignition and fuel injection are performed in the expansion stroke. After a predetermined time has elapsed, the purge is turned off (step S10) and the fuel injection timing is changed in steps S7 to S8. For example, the ignition timing is maintained after the compression top dead center (expansion stroke), but the fuel The injection is changed so as to start before the ignition timing, or is divided into before and after the ignition timing.
[0085]
If it is determined in step S302 that the time is cold, regardless of whether or not it is within a predetermined time, the process proceeds to step S6 and the purge is turned on, and the ignition and fuel injection are performed in the expansion stroke. The If the determination in step S301 is NO (small amount of adsorption), the process moves to step S10 and the purge is turned off.
[0086]
If it is determined in step S4 that the engine speed ne is equal to or higher than the first set speed N1, and if it is determined in step S11 that the engine is warm, purge OFF while the engine speed is increasing until the second set speed N2 is reached. (Steps S304 and S305) If the rotational speed is higher than the second set rotational speed N2, the stratification mode or the uniform mode is selected according to the determination as to whether or not the stratification region is present (S12 to S14).
[0087]
If it is determined in step S11 that it is cold, it is determined in step S306 whether or not the flag F is “1”. If the determination is YES (large amount of adsorption), the process proceeds to step S16, and step S306. If the determination is NO (small amount of adsorption), the process proceeds to step S19. Other processes are the same as those in the flowchart of FIG.
[0088]
According to this embodiment, torque fluctuation in the initial stage of engine start-up is suppressed, and torque adjustment from cranking to start-up is properly performed. It can be moderately suppressed.
[0089]
That is, as shown in FIG. 11, when the engine is warm and the amount of adsorption of the canister 34 is large, purge gas is introduced for a predetermined time from the start of cranking and ignition and fuel injection are performed in the expansion stroke when the engine is warm. By being performed, torque fluctuation is suppressed while combustion is being performed satisfactorily. Then, after a predetermined time has elapsed, the combustion chamber temperature rises, and ignition and combustion are likely to be promoted. If purge gas introduction is continued under such circumstances, the combustibility of the purge gas increases, resulting in a torque peak immediately after ignition. Therefore, the introduction of the purge gas is stopped, and the fuel injection is started before the ignition timing, so that ignition and combustion are performed.
[0090]
Further, during the rotation speed increase period after cranking to the completion of the start (from the first set rotation speed N1 to the second set rotation speed N2), if the purge gas is introduced, the combustibility is enhanced and the engine rotation speed is increased. In a hybrid vehicle that may start up too rapidly (see the broken line in FIG. 11) and the engine may start regardless of the driver's will during driving or the like, such a rapid increase in the rotational speed is Therefore, the introduction of the purge gas is stopped, and the fuel injection amount is controlled in the stratified combustion state, so that the rotational speed increase is moderately moderated. In this way, as indicated by the solid line in FIG. 11, the rotational speed smoothly changes from cranking, and the engine smoothly shifts to the start completion state.
[0091]
On the other hand, when the engine is apt to deteriorate in combustibility, it is controlled so that purge is introduced as much as possible during cranking or when the engine speed increases after cranking, so that the combustibility is kept good and the cranking is maintained. The number of revolutions after ranking and cranking is effectively increased.
[0092]
The present invention is particularly effective when applied to an engine of a hybrid vehicle. However, even when applied to an engine other than a hybrid vehicle, the engine vibration is reduced by suppressing torque fluctuation while performing good combustion at the start. There is no change in the effect to be obtained, and it is effective for improving the feeling.
[0093]
【The invention's effect】
As described above, the present invention introduces purge gas in an automobile engine equipped with an injector for directly injecting fuel into a combustion chamber and a purge device when the amount of evaporated fuel adsorbed by the canister is large at the initial stage of engine startup. The ignition timing is after compression top dead center, and the fuel injection timing is during the expansion stroke after the ignition timing. To control In particular, such control is performed during the cranking period, and the ignition timing is changed before the compression top dead center and the fuel injection is performed while the engine speed is increasing after cranking until the start is completed. Change the timing to an injection timing that corresponds to the combustion mode before the ignition timing. Therefore, at the initial stage of engine start, where torque fluctuations are likely to occur, torque fluctuation is suppressed by delaying the ignition timing and the combustion timing of the air-fuel mixture from the fuel injection from the injector, and ignition and combustion are performed well with purge gas Can be made. Accordingly, vibration can be reduced by suppressing torque fluctuation while maintaining good combustibility at the start.
[0094]
In particular, in a hybrid vehicle in which the engine is intermittently operated during vehicle operation, the evaporated fuel that tends to accumulate in the canister can be quickly purged during the engine start, and this purge gas can be used effectively. By suppressing start-up vibration while maintaining good start-up flammability, the engine may start regardless of the driver's will during driving, etc. The ring can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an engine provided with a start control device of 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-up 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 the opening / closing timing of the intake valve during normal operation and during startup.
FIG. 8 is a flowchart showing a second embodiment of start-up control with a part omitted.
FIG. 9 is a flowchart showing a third embodiment of start-up control.
FIG. 10 is a flowchart showing a fourth embodiment of start-up control.
11 is an explanatory diagram of the control shown in FIG.
[Explanation of symbols]
1 Engine body
5 Combustion chamber
13 Valve timing variable device
15 Spark plug
18 Injector
33 Purge device
34 Canister
38 Purge valve
60 Control unit
62 Accelerator position sensor
64 Water temperature sensor
70 Start discrimination means
71 Adsorption amount determination means
72 Purge control means
73 Combustion control means

Claims (7)

In an automobile engine that includes an injector that directly injects fuel into a combustion chamber, and a purge device that guides evaporated fuel from a canister to an intake passage through a purge valve,
Start determining means for determining when the engine starts; and
Adsorption amount determination means for determining the evaporated fuel adsorption amount of the canister;
A purge control means for opening the purge valve and introducing a purge gas when it is determined that the amount of evaporated fuel adsorbed is large at the initial stage of engine start according to the determination of the start determination means and the determination of the adsorption amount determination means;
When the purge gas is introduced by the purge control means in the initial stage of engine starting, the initial combustion adjustment control is performed so that the ignition timing is after compression top dead center and the fuel injection timing is in the expansion stroke after the ignition timing. Combustion control means ,
The purge gas introduction control by the purge control means and the start initial combustion adjustment control by the combustion control means are performed within the cranking state at the initial stage of engine start, and the engine speed is increasing after cranking until the start is completed. The ignition timing is changed before the compression top dead center, and the fuel injection timing is before the ignition timing, and fuel is injected in the stratification mode in which fuel is injected in the compression stroke and stratified combustion is performed. An automobile engine control device configured to change to an injection timing corresponding to any one of the uniform combustion modes in which uniform combustion is performed . 2. The control device for an automobile engine according to claim 1, wherein the purge control means performs purge gas introduction control at the initial stage of engine startup when the engine is warm . A control device for an automotive engine used in a hybrid vehicle having an engine and a motor, the engine being intermittently operated during vehicle operation, and introducing purge gas by the purge control means when starting the engine except for engine operation due to sudden acceleration 3. A control apparatus for an automobile engine according to claim 1, wherein the control and the starting initial combustion adjustment control by said combustion control means are performed . When fuel is injected from the injector in the compression stroke, it is equipped with a stratification means that causes the air-fuel mixture to be unevenly distributed around the spark plug, and in the specific operation, fuel is injected in the compression stroke to cause stratified combustion, and at the initial stage of engine startup As a starting initial combustion adjustment control by the combustion control means, ignition and fuel injection are performed in the expansion stroke, and purge gas introduction control by the purge control means is performed at least for a predetermined period corresponding to several cycles from the start of cranking. control apparatus for an automobile engine according to any one of claims 1 to 3, characterized in that the. In a hybrid vehicle that includes an electric drive motor and an engine, and the engine starts and assists the output when an increase in output is required during vehicle driving by the motor drive,
An injector that injects fuel directly into the combustion chamber;
Stratification means for unevenly distributing the air-fuel mixture around the spark plug when fuel is injected from the injector in the compression stroke;
A device for controlling an engine including a purge device that guides evaporated fuel from a canister to an intake passage through a purge valve;
Start determining means for determining when the engine starts; and
Combustion control means for performing ignition and fuel injection in the expansion stroke as engine start initial combustion adjustment control according to the determination of the start determination means;
Purge control means for opening the purge valve and setting the purge gas introduction state for at least a predetermined period corresponding to several cycles from the start of cranking,
During the warm period of the engine, the purge gas introduction is stopped and the ignition timing is changed before the compression top dead center after the elapse of a predetermined period corresponding to several cycles from the start of cranking to the completion of engine start. And a control device for an automobile engine , wherein the fuel injection timing is changed to a compression stroke before the ignition timing . There is provided a valve timing variable means for changing the valve 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 engine start, 6. The control device for an automobile engine according to claim 1, wherein the valve closing timing is set to a time earlier than the intake bottom dead center . The fuel pressure of the fuel fed by the fuel pump and injected from the injector can be changed between a predetermined high pressure and a predetermined low pressure lower than this, and is provided with a fuel pressure adjusting means for adjusting to maintain the predetermined high pressure during normal operation, The 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 1 to 6 .

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